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1944 A.D.
WORLD
The chemical 2,4-dichlorophenoxyacetic acid (2,4-D for short) was introduced in 1944 and was the first effective chemical herbicide (Latin for "plant killer"). Naturally, killing plant life indiscriminately is not something one would want to do, but 2,4-D is selective in its effects. It does not seriously affect grasses (including the various grains so important to humanity) but prevents the growth of broad-leaved plants, usually regarded as weeds.
WThe Abacus
500 B.C.
CAIRO, EGYPT
No one knows when the abacus first came into use, but it was probably known in Egypt at least as long ago as 500 B.C.
It consists essentially of rows of beads, sometimes strung on wires. In the simplest form there are 10 beads on each wire, the first row being units, the second row being tens, the third row being hundreds and so on.
The beads can be manipulated much as we manipulate the fingers on a hand in simple adding and subtracting. The advantage is that you may have nine or 10 "hands" present as so many rows of beads, and the movements you make are easier and quicker than manipulating your fingers would be.
A skilled operator can use the abacus flashingly to multiply, to divide, and to perform many complicated arithmetical manipulations. It was the first really important computing device worked out by human beings.
¬Aberration of Light
1728 A.D.
LONDON, ENGLAND
Since Copernicus's book nearly two centuries before, the question of the parallax of the stars had bothered astronomers. If the Earth did indeed move about the Sun, that should induce a parallactic displacement among the nearer stars as compared with the farther ones. Viewing a nearby star from one side of the Sun and then viewing it again from the other side, 186,000,000 miles away, should produce a displacement -- but it didn't.
Those who accepted Copernicus and Kepler felt this was because even the nearest stars were so far away that their parallax was too small to measure.
Still, telescopes were constantly improving, so astronomers kept trying.
One of those who tried was a British astronomer, James Bradley (1693-1762). Bradley, using a telescope 212 feet long, tried to measure the small displacement of stars in the course of the year and actually detected such a displacement. What he found, however, could not be parallax, because the displacement did not coincide with what would be expected if it were the result of Earth's changing position in its orbit.
Bradley looked for an alternate explanation and one occurred to him in 1728: The displacement arose because the telescope had to be tipped slightly to catch the light as the Earth moved (this is called adjusting to the aberration of light), just as an umbrella must be tipped when you're walking briskly through a rainstorm in which the drops are falling vertically. The amount by which the telescope must be tipped depends on the ratio of the speed of the Earth in its orbit to the speed of light.
This meant that although Bradley had not detected parallax, he had discovered a new way of calculating the speed of light, since the speed of the Earth in its orbit was known and the amount of the tipping of the telescope was known, too. This was the first determination of the speed of light since Roemer's a half-century before and it was a more accurate measurement. Bradley's figure was 176,000 miles per second, only 5 percent less than the true value.
What's more, the existence of light aberration was just as strong a proof that the Earth was moving as the existence of stellar parallax would have been.
UAcetylcholine
1914 A.D.
LONDON, ENGLAND
A fungus called ergot produces a variety of alkaloids with powerful effects on animal tissues. The eating of fungus-ridden grain can produce a disease called ergotism, and in the centuries before the cause was understood, there were terrible epidemics of ergotism.
Among those who worked on ergot was a British biologist, Henry Hallett Dale (1875-1968). In 1914 he isolated from it a compound called acetylcholine, which seemed to produce effects on organs similar to those produced by certain nerves. The significance of this was not fully understood for several more years.
╖Understanding Acids
1789 A.D.
FRANCE
Antoine Lavoisier had named the active portion of the atmosphere oxygen (acid-producer) because it was thought that all acids contained oxygen.
In 1789, however, the French chemist Claude-Louis Berthollet (1748-1822) showed that hydrocyanic acid and hydrosulfuric acid did not contain oxygen. To be sure, they are very weak acids, but it was eventually shown that hydrochloric acid, a strong acid, also did not contain oxygen.
┤Acid-Base Pairs
1923 A.D.
COPENHAGEN, DENMARK
After the notion of ionic dissociation was established by Arrhenius, an acid came to be defined as a substance that split up to yield hydrogen ions, while a base was one that split up to yield hydroxyl ions (OH;s-). These neutralized each other, because hydrogen ions and hydroxyl ions combined to form neutral water molecules.
The Danish chemist Johannes Nicolaus Bronsted (1879-1947) suggested a more general definition in 1923. An acid didn't simply give up a hydrogen ion (which could be viewed as a proton), because as a proton, it could not exist loose in solution. The proton, once it broke free of the acid molecule, must promptly attach itself to another molecule. Therefore, chemists ought to speak of acid-base pairs. Whenever a proton transferred from one molecule to another, the one that gave up the proton was an acid, the one that accepted it was a base. This broadened the concept and made it more useful.
╧Acetylcoenzyme A
1951 A.D.
GERMANY
Lipmann had demonstrated the existence of coenzyme A as the carrier of the acetyl group, which represented a crucial crossroad in metabolism.
In 1951 the German biochemist Feodor Felix Konrad Lynen (1911-1979) studied the function of coenzyme A in the metabolism of fat molecules particularly. He was the first to isolate acetylcoenzyme A, the compound that acts as intermediary in the transference of the acetyl group from one compound to another.
This work paralleled the work done the year before by Bloch, who used carbon- 14 as a tracer to work out the way coenzyme A was involved with cholesterol synthesis. As a result, Lynen shared with Bloch the Nobel Prize for physiology and medicine in 1964.
*Learning about Acoustics
1896 A.D.
CAMBRIDGE, MASSACHUSETTS
In 1896 an American physicist, Wallace Clement Ware Sabine (1868-1919), completed the study of a new lecture room that had been built at Harvard University the previous year. The lecture room had a flaw; the lecturer could not be heard because of excessive reverberation. Sabine had investigated every angle of the problem, even photographing sound waves that were made visible by the changes in light refraction they produced.
As a result of his studies, Sabine founded the science of architectural acoustics. In the process he showed how to design a hall that would make the sounds of voice and music clear. For the purpose, he made use of mathematical equations that related absorptivity of sound by various materials and the volume of the room to the amount of reverberation.
°Exploring North America
1793 A.D.
ALBERTA, CANADA
A British-born Canadian explorer, Alexander Mackenzie (1764-1820), worked his way into the interior of Canada, settling in what is now the Province of Alberta. From there he followed what is now called the Mackenzie River to its mouth in the Arctic Ocean, which he reached in 1789. In 1793 he crossed the Rocky Mountains to the Pacific Ocean in what is now British Columbia.
He was the first person to visit the Atlantic, Pacific, and Arctic shores -- all three -- of North America.
`Actinium
1899 A.D.
FRANCE
There was more in uranium ores than the polonium and radium that the Curies had detected. In 1899 the French chemist André-Louis Debierne (1874-1949), a close friend of the Curies, isolated still another element from the ores. He called it actinium, from a Greek word for "ray," so that the name was the Greek equivalent of the Latin radium.
∩Advanced Schools
387 B.C.
ATHENS, GREECE
The Greek philosopher Plato (ca. 428-ca. 348 or 347 B.C.) founded a school in the western suburbs of Athens in 387 B.C. Intended for advanced study, it might be called the world's first university. Because it was on the grounds that had once belonged to a legendary Greek named Academus, it came to be called the Academy.
Plato's pupil Aristotle (384-322 B.C.) founded a school of his own in Athens in 335 B.C. It was called the Lyceum, because the building it occupied had been dedicated to Apollo Lyceus, god of shepherds. Aristotle's lectures at the school were collected into nearly a 150 volumes, representing a one-man encyclopedia of the knowledge of the times. Much of it represented the original thought and observations of Aristotle himself.
Some 50 of these volumes have survived through a fortunate chance. They were found in a pit in Asia Minor about 80 B.C. by soldiers of the Roman general Lucius Cornelius Sulla (138-78 B.C.). They were then taken to Rome and copied.
σChemical Affinites
1788 A.D.
SWEDEN
Chemists up to this time had to take chemical reactions as they found them.
Substance A would react with substance B but not with substance C and that was all there was to it.
The Swedish mineralogist Torbern Olof Bergmann (1735-1784) had struggled to classify minerals and to make sense out of chemical reactions. He listed affinities -- that is, the extent to which different chemicals interacted. He also prepared tables that made some sense out of the matter and helped predict whether certain reactions, not yet observed, would take place or not if given a chance.
His results were published posthumously in 1788, and while they represented the barest beginning in the study of chemical behavior, they were a beginning.
YThe African Continent
1990 A.D.
AFRICA
If you always thought of Africa as mostly jungle, you can see from this satellite's-eye view that it isn't so.
In fact four-fifths of the world's second largest continent is made up of desert and grasslands. Less than a fifth is forest, and because of people's encroachment on the forest, it is unfortunately less forested every day.
Africa is made up of more than 11 million square miles, or 17.9 percent of the earth's land surface. With about 661 million people, it is second in terms of population, but far behind Asia's total of 3.1 billion people.
At the north edge of Africa you can see the vast Sahara, the largest desert in the world, covering about two-fifths of the continent.
The Sahara so divides the continent that people often speak of North Africa and Sub-Saharan Africa as if they were not connected. And indeed, they are very different.
The northern Mediterranean coastal area is largely Muslim and inhabited by Arabic peoples, while the vast southern portion of the continent is inhabited by black peoples who are largely Christian or animistic.
Africa is home to Egypt, one of the world's most ancient civilizations, estimated to be about 5,000 years old. And though not as much is known about them, great civilizations have also flourished in Sub-Saharan Africa.
The first of these civilizations, Timbuktu (a great university city), Goa and Ghana, arose along the southwestern edge of the Sahara as trade across the desert developed.
Ghana appears to have been founded about 300 AD and reached its height about 1,000 AD, when the empire of Mali arose to conquer it.
In the 1500s the Songhai Empire rose, spreading from the Atlantic to what is now central Nigeria. And Kanem-Bornu, around Lake Chad (the small spot just above the dark green section near the middle of the continent) was founded in the 700s and lasted a thousand years. It was known for its fierce iron-mailed knights.
Later, other civilizations arose further south. Kongo arose around the mouth of the Congo River and Zimbabwe became a great empire in south eastern Africa.
The isolated mountain nation of Ethiopia has a separate history. It traces its civilization to the Bible story of the Queen of Sheba's visit to King Solomon of Israel. According to the Ethiopian story, Solomon and the queen had a son named Menelik, who founded Ethiopia. Among the treasures of this country are beautiful churches in the town of Lalibela that have been carved in single pieces out of bedrock.
One of the most shameful periods of African history began in the 1400s when the Portuguese established trading posts on the west coast and began buying slaves. The slaves were generally prisoners taken in inter-tribal warfare who were sold to Europeans or Arabs.
The trading led to European political involvement, and during the 1800s Europe took over much of Africa, excluding only Ethiopia and Liberia, a colony founded by freed American slaves.
Naturally, that period is regarded as humiliating by Africans, though it did bring medicine and education to the area. And, interestingly, many of those who led independence movements were products of European schooling.
Currently, Africa is one of the most troubled areas of the world, facing poverty, disease, warfare and environmental decline.
In South Africa, for example, there are divisions between whites and blacks and between blacks and blacks. Much of the tribal violence throughout Africa was caused by how colonial governments divided the continent, often paying little attention to ethnic boundaries.
But perhaps the most badly afflicted area is in the northeast. Ethiopia, Somalia and Sudan have all been victims of periodic famines combined with government mismanagement and warfare. Also afflicting Africa is the decline in its famous jungle areas and in its wildlife, caused primarily by over-hunting and by people taking over the animals' habitats.
êArtificial Hearts
1969 A.D.
U.S.A.
In comparison with most living organs, the heart is simple. It is primarily a pump designed to push the blood through the vessels of the circulatory system.
It is not difficult to imagine that an artificial pump the size of the heart and similar in structure but powered from without might do the job.
The first attempt to place such an artificial heart inside a human being was made in 1969. The American surgeon Denton Cooley implanted a plastic heart designed by the Argentine-born American Domongo Liotta. The patient lived for nearly three days with the artificial heart before it was replaced with a transplanted natural heart.
}Smallpox and AIDS
1977 A.D.
SOMALIA, EAST AFRICA
In 1977 the last case of smallpox was recorded, in Somalia. The smallpox virus is now thought to be extinct except for samples grown in laboratories for research purposes.
The ending of one scourge, however, seemed to have been balanced by the coming of another. In 1977 two male homosexuals in New York City were found to have a rare form of cancer, which was eventually recognized to be a symptom of a disease called acquired immune deficiency syndrome, usually abbreviated AIDS. This disease, usually fatal and so far incurable, spread rapidly and became as feared in the 1980s as smallpox was in the 1780s.
]Air Masses
1920 A.D.
OSLO, NORWAY
A father-and-son team of meteorologists, Vilhelm Friman Koren Bjerknes (1862-1951) and Jacob Aall Bonnevie Bjerknes (1897-1975), had set up weather-observing stations all over Norway during World War I.
By 1920 they had shown that the atmosphere is made up of large air masses and that there is a sharp differentiation in temperature between warm tropical air masses and cold polar air masses. The sharp boundaries between them they called fronts, from an analogy to the battle lines that had so preoccupied Europe in recent years.
This simplified the technique of weather prediction.
ÜAir Pumps
1645 A.D.
GERMANY
Once Italian physicist Evangelista Torricelli (1608-1647) had produced a vacuum by allowing mercury to pour out of a tube, it seemed to some that vacuums could be produced in more direct ways. Perhaps air could simply be pumped out of any vessel, and larger volumes of vacuum could be formed than Torricelli had managed.
A German physicist, Otto von Guericke (1602-1686), produced the first practical air pump in 1645. It worked like a water pump but with parts sufficiently well fitted to be reasonably airtight. It was run by muscle power and was slow, but it worked. Guericke produced a large enough vacuum to make useful experiments possible.
He was able to show that a ringing bell within a vacuum could not be heard, thus bearing out Aristotle's contention that sound would not travel through a vacuum. Guericke also showed that candles could not burn in a vacuum and that animals could not live.
He also weighed a metal sphere before he evacuated it and then again afterward. The small loss in weight was obviously the weight of air that had been inside. From that, and the volume of the air, he was able to get the first measurement of air's density.
~Air Pressure and Altitude
1648 A.D.
FRANCE
If the mercury column of Italian physicist Evangelista Torricelli's (1608-1647) barometer were held up by air pressure, then if one went up high in the air, there should be less air above, and the air pressure should decrease. Therefore, so should the height of the mercury column.
To test this, French mathematician Blaise Pascal (1623-1662) sent his brother-in-law up a neighboring mountain with a couple of barometers. His brother-in-law climbed about a mile and found that the mercury columns had dropped from 30 to 27 inches.
This showed clearly that the atmosphere could only have a finite height. In fact, if it were as dense throughout as it was at sea level, it would be only 5 miles in height.
Even when it became apparent that air became less dense with height, so that quantities of it extended far higher than 5 miles, there had to be limits. At a height of 100 miles or so, air would be so thin that it might as well be vacuum, and so for all the rest of the distance to the Moon and to other heavenly bodies.
Experiments like those of Torricelli and Pascal's brother-in-law amounted to the discovery of outer space.
vAlaska
1784 A.D.
ALASKA
After Bering's discovery of the Bering Strait, Russians from Siberia, venturing eastward, found large numbers of sea otters, whose pelts proved very profitable. In 1784 the Russians established the first European settlement in Alaska, and for the next 80 years Russian holdings expanded until all of the present-day state of Alaska was part of the Russian Empire.
Alchemy
300 A.D.
EGYPT
Creating chemical change has been part of human life from the start. Cooking involved chemical changes and so did fermentation. The production of pottery out of clay, metals out of ore, charcoal out of wood, and glass out of sand all involved chemical changes.
It was not until the years after Alexander the Great, however, that scholars began to study chemical change systematically. This may have been the result of a fusion of Greek and Egyptian thinking, and it flourished first in Ptolemaic Egypt.
As Euclid, in Egypt, summarized ancient geometry, and Ptolemy, again in Egypt, summarized ancient astronomy, so Zosimus (240-?), also in Egypt, about the year 300, summarized ancient alchemy.
The early work in alchemy was highly mystical and not very useful and was sidetracked eventually in a vain effort to find some way of changing "base metals," such as lead or iron, to gold. Nevertheless, inquiring minds, even when misled, could not help making some discoveries in the long run, and this the alchemists did.
»Algebraic Symbols
1591 A.D.
PARIS, FRANCE
Until now, mathematicians had described quantities, relationships, and problems in words (it seemed the only way), and what they described was often hard to envisage.
Francois Vieta (1540-1603) began to symbolize constants and unknowns by letters of the alphabet, the now familiar x's and y's of algebra. In 1591, he wrote a book about algebra that was the first a present-day high-school student would recognize at a glance to be dealing with that subject.
The progression from words to symbols was to mathematics something like the progression from ideographs to letters in ordinary writing, or from Roman numerals to Arabic numerals in arithmetical computation.
=Algebra
250 A.D.
GREECE
Through most of Greek history, mathematicians concentrated on geometry, although Euclid considered the theory of numbers. The Greek mathematician Diophantus (3rd century), however, presented problems that had to be solved by what we would today call algebra. His book is thus the first algebra text.
He is best known for problems that had to be solved with whole numbers, and such problems involve what are still called Diophantine equations. He also showed that fractions could be treated as numbers, thus reducing much of the discomfort they usually caused.
Algebra and Mechanics
1788 A.D.
FRANCE
Geometry seemed a natural way of describing mechanics, but Descartes had shown that algebra could deal with geometric problems.
A French mathematician, Joseph-Louis Lagrange (1736-1813), tackled the study of mechanics in a totally nongeometric way. Using algebra and calculus, he worked out very general equations by means of which mechanical problems could be solved.
He summarized his work in Analytical Mechanics, published in 1788 by a very reluctant publisher. (A friend of Lagrange had to guarantee his purchase of any unsold copies.) It turned out to be a classic of science, although (as Lagrange boasted) there was not one geometric diagram in it. Geometry remains important, but Lagrange helped free the world of science from its unnecessary tyranny.
Alloy Steels
1883 A.D.
GREAT BRITAIN
For 3,000 years, steel (carbonized iron) had been the strongest material known for tools, structures, and weapons, but that didn't mean it couldn't be improved.
Attempts were made to improve the qualities of steel by adding other metals. Manganese was one of the metals tried, but it seemed to make the steel more brittle. A British metallurgist, Robert Abbott Hadfield (1858-1940), added more manganese than others had thought advisable, however, and when the steel was 12 percent manganese, it was no longer brittle. If it was then heated to 1,000° C and quenched, it became superhard. Where ordinary steel used for railroad rails had to be replaced every nine months, rails made of manganese- steel lasted 22 years.
Hadfield patented his manganese-steel in 1883, and that marked the beginning of the triumph of alloy steel. Other metals were then added to steel in varying quantities and mixtures -- chromium, tungsten, molybdenum, vanadium, niobium, and so on -- in search of alloys with new and useful properties.
▌Inventing the Alphabet
1500 B.C.
GREECE
By 1500 B.C., Egyptian hieroglyphic writing and Babylonian cuneiform writing (inherited from the Sumerians), together with Chinese writing in the Far East, were the most important written languages in the world. All remained terribly complicated, and there is no reason they should not have remained complicated until the present time. The Chinese language has. Between the Egyptians and the Babylonians were the Canaanites, inhabiting the eastern shore of the Mediterranean Sea. (The Greeks called them Phoenicians.) They were traders who acted, among other things, as intermediaries between the Egyptians and Babylonians. It was necessary for such traders to know both the Egyptian and Babylonian languages, and that was a hard chore indeed.
It occurred to some nameless Canaanite to simplify writing by adopting a kind of shorthand. Why not give a separate symbol to each of the common sounds made by human beings in speaking a language? You could then build up any words of any language by using those sound-symbols. Sound-symbols had, in fact, been used by the Egyptians, but they also preserved symbols for syllables and for whole words. The Canaanite inventor had the notion that the sound-symbols should be used exclusively and that words should be built up out of them.
The first two symbols of this collection were aleph (the usual symbol for an ox) and beth (the usual symbol for a house). To the Greeks, who eventually adopted the system, these became alpha and beta, and we still call the system of symbols the alphabet.
The Phoenician alphabet, which first came into use about 1500 B.C., revolutionized writing, making it far easier to write and to read, so that the chances of literacy were increased. This is one invention that seems to have occurred only once in human history. The alphabet was not invented independently by any other society. All alphabets in use today (including the one in which this book is written and printed) are descended from that first Phoenician one.
ºAlpha Particles
1906 A.D.
ENGLAND
By now it was understood that beta rays were streams of speeding electrons (beta particles), while gamma rays were electromagnetic radiation of still shorter wavelength and higher frequency than X rays. The nature of the alpha particles that made up the alpha rays remained to be determined.
In 1906 Rutherford, working with a German assistant, Johannes Hans Wilhelm Geiger (1882-1945), managed to determine the ratio of the electric charge to the mass in the case of the alpha particles. This ratio turned out to be equal to that in a helium atom from which two electrons had been removed.
Later Rutherford fired alpha particles at a double wall of glass with a vacuum between. The alpha particles had energy enough to penetrate the first partition but, in the process of penetration, lost so much energy that they were unable to penetrate the second. They therefore remained in the vacuum between, and after enough had accumulated, Rutherford found that the thin gas that had appeared in the vacuum was indeed helium, judging from the spectrum.
Alpha particles and helium were thus related, but not identical. After all, streams of helium atoms would not penetrate glass.
äAluminum
1825 A.D.
DENMARK
Though aluminum is more common than iron (only oxygen and silicon are commoner), it is extremely difficult to break its hold on other atoms.
Orsted, the first person to demonstrate electromagnetism, was also the first person to isolate aluminum. For the purpose, he made use of a still more active element, potassium, which could wrench other atoms out of aluminum's grip. In 1825 he managed to obtain the first bits of the metal.
The procedure for obtaining it was so difficult, however, that aluminum remained virtually a precious metal for some 60 years, until a cheap method for obtaining it in quantity could be worked out.
Manufacturing Cheap Aluminum
1886 A.D.
PITTSBURGH, PENNSYLVANIA
Aluminum is the most common element in the Earth's crust. It was first isolated by Orsted, but the isolation was so difficult that it was virtually a precious metal. Napoleon III had his cutlery and a baby rattle for the Prince Imperial made out of aluminum, and the capstone on the Washington Monument is a slab of aluminum.
In 1886 an American student of chemistry, Charles Martin Hall (1863-1914), heard his teacher say that anyone who discovered a cheap way of making aluminum would grow rich and famous. In his home laboratory, using homemade batteries, Hall devised a method of preparing aluminum by the use of an electric current, as Davy had prepared sodium and potassium nearly 80 years before. He used aluminum oxide dissolved in a molten mineral named cryolite, and into it he stuck carbon electrodes.
Oddly enough, that same year a French metallurgist, Paul-Louis-Toussaint Heroult (1863-1914), with the same last initial and the same birth and death years, independently devised precisely the same system, which is therefore called the Hall-Heroult process.
Aluminum became cheaper almost at once, and it is now second only to steel as a structural material. A combination of lightness and strength makes it ideal for aircraft, for instance.
%Amalthea, A Moon of Jupiter
1892 A.D.
PARIS, FRANCE
Galileo had discovered the four large satellites of Jupiter. In the interval since, no other Jovian satellite had been discovered, even though Saturn, a smaller and more distant planet, was known to have eight satellites by this time.
The American astronomer Edward Emerson Barnard (1857-1923) reasoned, as Hall had in connection with Mars, that a fifth satellite, if it existed, would have to be small and close to Jupiter. He searched the neighborhood of Jupiter and in 1892 spotted a satellite only 112,500 miles from Jupiter's center and only 68,000 miles above Jupiter's cloud surface. We now know it to be only 125 miles in diameter.
It was variously called Barnard's satellite and Jupiter V (because it was the fifth satellite to be discovered), but the French astronomer Camille Flammarion (1842-1925) suggested it be named Amalthea, after the goat (or nymph) that served as wet-nurse for Jupiter (Zeus) during the god's infancy.
Amalthea was the 21st satellite to be discovered and the last to be discovered without photography.
The Amazon River
1542 A.D.
PERU
One of Pizarro's aides during his conquest of Peru was Francisco de Orellana (ca. 1490-ca. 1546), who was exploring eastward past the Andes Mountains when he came upon the headwaters of a river. He felt it would be easier to see where the river led him than to make his way back across the formidable mountain barrier.
From April 1541 to August 1542, he progressed down the river, which as it happened, was by far the greatest in the world in terms of water volume delivered to the ocean and area drained. His report mentioned tribes that appeared to be led by women. This reminded people of the Amazons, the women warriors of Greek legend, and the river was named the Amazon in consequence.
Orellana was the first European to cross South America from ocean to ocean.
Americium and Curium
1944 A.D.
BERKELEY, CALIFORNIA
After Seaborg had helped McMillan isolate plutonium, it was clear that other elements might exist beyond that element. Seaborg devoted himself to the task of preparing such elements by bombarding the massive atoms already known with subatomic particles.
In 1944, by bombarding plutonium with neutrons and alpha particles, Seaborg and his associates prepared americium, with an atomic number of 95, and curium, with an atomic number of 96. The former was named for America and the latter for the Curies.
∞ Americans in Space
1962 A.D.
HOUSTON, TEXAS
On February 20, 1962, the United States launched Friendship 7, which placed the first American in orbit. He was John Herschel Glenn, Jr. (b. 1921), who orbited the Earth three times and remained in space for 5 hours.
'Inventing Pottery
9000 B.C.
MESOPOTAMIA
It has always been important for human beings to carry things, and the obvious way to carry them is in the hands, or in the crook of the arm. There is a limit to how much can be carried in this fashion, however. What we needed were artificial hands, so to speak, that were considerably larger than our natural hands.
Objects could be carried in hides, but hides are an inconvenient shape and heavy. Gourds might do, but they have to be taken as they come. Eventually human beings learned to weave twigs or other fibers into baskets. These were light and could be made in any shape.
Baskets, however, were only useful in carrying solid, dry objects made up of particles considerably larger than the interstices of the weave. Baskets could not be used to carry flour or olive oil, for instance, or most important, water. It might seem natural to daub baskets with clay, which upon drying would cake the holes and make the basket solid. The dried mud would tend to fall away, however, especially if the basket was shaken or struck. But if the basket was placed in the sun and allowed to bake in direct sunlight, the mud would harden further, and the basket might then become fairly serviceable for carrying powders and fluids.
But then why use the basket? Why not simply begin with clay, mold a container out of it, and let it dry in the sun? You would then have a pot made of crude earthenware, and some of these may have been formed as early as 9000 B.C. Such pots are soft, however, and don't last long.
Some stronger heat was required. When earthenware was placed in the fire, it became hard pottery, and such pottery can be traced back to perhaps 7000 B.C. This may have been the first use of fire for something other than light, heat, and cooking.
Pottery not only made it possible to carry liquids, it also introduced a new form of cooking. Until then, food had usually been roasted, exposed directly to the flames or to dry heat. Once a pot existed that could hold water and withstand the heat of flames, food could be heated in the water -- it could be boiled. In this way stews and casseroles came into existence. And of course pottery could be decorated and well shaped. Cleverly decorated examples would be in special demand. Artisans could exchange them for other material they found needful. And since pottery lasts indefinitely, if well cared for, it can change hands often, and one group of people can use it in trading with another group.
In early pottery, the clay was pressed and pounded into the shape of a pot and the result was something quite lumpy and asymmetric but serviceable. If the pot could be turned, however, a relatively light pressure from the hand would produce a symmetrical cylindrical shape, and by appropriate increases in pressure or by downward pushes, complicated modifications of the basic cylinder could be made while retaining symmetry. This could be done if the clay was placed on a horizontal, circular slab of wood or stone (a potter's wheel), which had a central spike underneath that could be balanced in a depression and the whole turned rapidly.
The potter's wheel was one of the first examples of the use of a wheel and one of the first uses of rotary motion. We don't know when it was first used, but it may have led to the idea of wheel generally, and to wheeled transportation.
NAnaphylactic Shock
1902 A.D.
FRANCE
The French physiologist Charles Robert Richet (1850-1935) worked on immune sera, the sort of thing that Behring had used successfully on diphtheria. To his surprise, Richet discovered that if he caused an animal to produce an immune serum to a particular foreign protein (an antigen) and then injected the antigen, the animal died. In 1902 Richet named this phenomenon anaphylaxis, from Greek words meaning "overprotection."
From then on, physicians were warned. Serum therapy had to be conducted in such a way as to prevent the possibility of sensitization, which would produce serum sickness. It came to be understood that people might be sensitized to foreign proteins in the environment -- in plant pollen, in dust, in food -- and exhibit unpleasant reactions. These reactions came to be called allergies (from Greek words meaning "other work," because the mechanisms of the body do something other than the work they are supposed to do).
Richet's work on anaphylaxis, and the understanding of allergies that it led to, brought him the Nobel Prize in medicine and physiology in 1913.
¥Spiral Nebulas
1845 A.D.
DUBLIN, IRELAND
The nebulas that had been seen in the sky until 1827 had seemed to be no more than little cloudy patches. Telescopes weren't good enough to make out much in the way of structure -- or perhaps structure was simply lacking in them.
In 1827, however, an Irish astronomer, William Parsons, Earl of Rosse (1800-1867), began work on the largest telescope yet planned, and by 1845 it was finished. It had a mirror that was 72 inches across. However, the telescope, though large, was clumsy. It couldn't see much of the sky even when the sky was clear -- and it was hardly ever clear.
Nevertheless, the telescope did accomplish a few things. In 1845 Rosse noted that one nebula had a distinct spiral shape, and in the following years he found 14 others that were also spiral in appearance. These were termed spiral nebulas, and the time was to come, 80 years later, when they achieved considerable importance.
·Andromeda Nebula
1612 A.D.
BERLIN, GERMANY
In 1612 German astronomer Simon Marius (1570-1624) noted a fuzzy spot in the constellation of Andromeda. It did not have the sharp, pointlike quality of a star, but seemed a tiny luminous cloud. Indeed, it came to be called the Andromeda nebula, from the Latin word for "cloud."
The discovery of the Andromeda nebula did not seem very important at the time, but three centuries later it would initiate a discussion that would lead to a fundamentally new understanding of the Universe.
╣Androsterone: A Male Hormone
1931 A.D.
GERMANY
Butenandt had isolated estrone, a female sex hormone. It seemed obvious that if female sex hormones existed, male sex hormones must also exist.
In 1931 Butenandt obtained a small quantity of a hormone that was named androsterone (from the Greek word for "man"). It is produced by cells of the testicle and stimulates the type of development required to produce the characteristics of the adult male. Butenandt isolated only 15 milligrams of the hormone (a two-thousandth of an ounce), but by delicate microanalytical methods, he was able to make two analyses of the compound.
For his work on the sex hormones, Butenandt was awarded a share of the Nobel Prize for chemistry in 1939.
æAnesthesia for Better Surgery
1846 A.D.
MASSACHUSETTS
Pain, however useful as a warning signal designed to keep living organisms from damaging themselves too badly, becomes useless agony when operations must be performed.
Attempts to control pain were many. The use of alcohol or some form of what came to be called hypnotism was old. Acupuncture was used in the Orient. The new chemistry also contributed nitrous oxide, which, when inhaled, served to suppress the sensation of pain.
As time went on, substances such as di-ethyl ether (more commonly called simply ether) and chloroform were found to cause unconsciousness during which the sensation of pain disappeared. Ether came to be used by physicians during operations, the first to do so being an American physician, Crawford Williamson Long (1815-1878), who used it in 1842 to remove a tumor. He did not publish or publicize his work, however.
An American dentist, William Thomas Green Morton (1819-1868), used ether on a patient in September 1846, when extracting a tooth. The patient himself told the tale to a newspaper, and Morton was urged to demonstrate the use of ether during an operation at Massachusetts General Hospital.
It was this demonstration that effectively introduced the practice into medicine, so that Morton usually gets credit for the discovery. The American physician Oliver Wendell Holmes (1809-1894) suggested the term anesthesia, from Greek words meaning "no sensation."
┴Animal Classification
350 B.C.
ATHENS,GREECE
Aristotle was a careful and meticulous observer who was fascinated by the task of classifying animal species and arranging them into hierarchies. He dealt with over 500 animal species in this way and dissected nearly 50 of them. His mode of classification was reasonable and in some ways strikingly modern.
He was particularly interested in sea life. He observed that the dolphin brought forth its young alive, nourishing its young by a special organ called a placenta before birth and by milk after it was born. No fish did this, but all mammals did, so Aristotle classified the dolphin with the beasts of the field rather than with the fish of the sea. It took biologists generally about 2,000 years to catch up with Aristotle in this regard.
Classification is important in itself, for it helps to organize a field of study. In the case of biology it was particularly important, for it led eventually to thoughts of biological evolution.
¥Hydrogen Radiation
1951 A.D.
CAMBRIDGE, MASSACHUSETTS
Dutch astronomer Hendrik Christoffel Van de Hulst (b. 1918) had predicted in 1944, from theoretical considerations, that hydrogen atoms in space would emit microwave radiation with a wavelength of 21 centimeters.
In 1951 American physicist Edward Mills Purcell (b. 1912), who had earlier helped work out the theory of nuclear magnetic resonance, actually detected this radiation coming from outer space. This demonstrated the value of radio waves in detecting the presence of given atoms and molecules in interstellar space. The wavelengths of the radiation emitted were characteristic of different substances and acted as "fingerprints."
ÇThe Antarctic Circle
1773 A.D.
ANTARCTICA
The Arctic Circle was first crossed at sea by Ottar, though unnamed primitives must surely have ventured past it on land earlier.
However, the Arctic Circle passes through northern North America, Europe, and Asia, and once the glaciers had retreated, the line was open to venturesome hunters.
The Antarctic Circle, however, lies far to the south of any populated area.
The closest is Tierra del Fuego at the southern tip of South America, which even at its most southerly is still about 650 miles north. It is safe to say, then, that no human being, primitive or civilized, had ever crossed the Antarctic Circle prior to 1773.
In that year, Captain Cook, on his second voyage through the Pacific in search of an important land area, ventured far to the south and on January 17 (at the height of the Antarctic summer) crossed the Antarctic Circle, a true first for humanity.
JAntarctica
1839 A.D.
ANTARCTICA
The American explorer Charles Wilkes (1798-1877) commanded an exploring expedition in Antarctic waters between 1838 and 1840. He cruised along the limits of the sea to the south of the Indian Ocean. Ice everywhere prevented him from landing, but he saw enough land at a distance to realize, by 1839, that there was a continent within the Antarctic Circle. The information he brought home demonstrated this amply (and part of the Indian Ocean sector of the continent is still called Wilkes Land in his honor), so that Wilkes may be considered the discoverer of Antarctica.
ΩAnthrax Inoculation
1881 A.D.
FRANCE
It had been three-quarters of a century since Jenner had successfully prevented smallpox by inoculating people with cowpox, a much milder disease that conferred immunity to the more serious one. This feat could not be repeated in other cases because other serious diseases did not seem to have milder cousins.
Pasteur decided, however, that one might be able to manufacture those milder cousins in the laboratory.
Pasteur studied the deadly disease anthrax, which ravaged herds of domestic animals. Koch had reported observing the bacteria responsible for the disease. Pasteur confirmed Koch's finding and showed that the germs sometimes survived in the ground as heat-resistant spores for long periods of time. It was therefore necessary to kill all infected animals and bury them deep.
If an animal did survive anthrax, however, it was immune thereafter. Pasteur therefore prepared cultures of anthrax germs and heated them. In this way, he destroyed the activity and virulence of the germs but left an "attenuated" preparation that could still produce immunity against anthrax.
In 1881 he carried through a dramatic experiment. Some sheep were inoculated with his attenuated germs; others were not. After a time, all the sheep seemed healthy, but when they were injected with deadly anthrax germs, those that had been inoculated lived; those that had not been inoculated died.
Pasteur, in tribute to Jenner, called the process vaccination, even though the disease vaccinia was not involved.
µBetter Antibiotics
1948 A.D.
MADISON, WISCONSIN
In 1948 a new antibiotic, chlortetracycline, discovered four years earlier by the American botanist Benjamin Minge Duggar (1872-1956), was placed on the market as Aureomycin. Its molecule was made up of four rings of atoms, and it was the first of a family of such antibiotics with the general name of tetracyclines. They were effective over a wide range of microorganisms and had low toxicity. They are now the most useful and least dangerous of the antibiotics.
4Protein Structures
1969 A.D.
UNIVERSITY OF CALIFORNIA, BERKELEY
The techniques for elucidating protein structure had continued to advance since British biochemist Frederick Sanger's (b. 1918) work on the structure of insulin.
In 1969 the American biochemist Gerald Maurice Edelman (b. 1929) worked out the structure of a gamma globulin, a type of protein that exists in the blood and out of which various antibodies are formed. (Antibodies react with particular foreign proteins, so that they are essential to the body's immune mechanism.) For this, Edelman received a share of the Nobel Prize for physiology and medicine in 1972.
Also in 1969, British physicist Dorothy Crowfoot Hodgkin completed our knowledge of the insulin molecule by working out its three-dimensional structure.
And still in 1969, the Chinese-born American biochemist Choh Hao Li (b. 1913) synthesized the enzyme ribonuclease, putting every one of its 124 amino acids into a chain in the right order. Ribonuclease, which catalyzes ribonucleic acid's breakdown into smaller fragments, was the first enzyme to be synthesized.
WMaking Antiprotons
1955 A.D.
BERKELEY, CALIFORNIA
In the 26 years since Dirac had advanced his theory of antiparticles, only the antielectron (positron) had been detected. Scientists were quite convinced that if the antielectron existed, the antiproton had to exist also. The antiproton, however, would have a mass 1837 times that of the antielectron and therefore require 1837 times the energy to be formed.
It was not practical to wait for one of the relatively few cosmic ray particles sufficiently energetic to form an antiproton. Once the bevatron was built, however, energies capable of forming antiprotons were available in quantity.
In 1955 Segré, who had first detected technetium, and the American physicist Owen Chamberlain (b. 1920) bombarded copper for hours with protons possessing energies of 6.2 BeV. They worked out an elaborate system for detecting any antiprotons that might be formed, even amid large numbers of other particles of different charge and mass. The result was that, among 40,000 particles, they detected 60 antiprotons.
For this, Segré and Chamberlain received the Nobel Prize for physics in 1959.
Radio From Space
1932 A.D.
PRINCETON, NEW JERSEY
As radio came more prominently into use for communication and home entertainment, the problem of static (a crackling interference that made communication uncertain and music unpleasant) cried out for correction. Static had a number of causes, including thunderstorms, nearby electric equipment, and aircraft passing overhead.
The Bell Telephone Company, which needed radio for ship-to-shore calls, among other things, set one of its employees, Karl Guthe Jansky (1905-1950), to exploring the problem.
Jansky detected a new kind of weak static from a source that at first he could not identify. It came from overhead and moved steadily. At first it seemed to Jansky that it must be the Sun. However, the source gained slightly on the Sun to the extent of 4 minutes a day. This is just the amount by which the vault of the stars gains on the Sun, so that the source must lie beyond the Solar System.
By the spring of 1932, Jansky had decided that the source was in the constellation of Sagittarius, the direction in which American astronomer Harlow Shapley had placed the center of our galaxy in 1918.
This represented the birth of radio astronomy, in which astronomers learned to receive and interpret radio waves rather than light waves. Light waves, of course, are easily perceived by the retina of the eye and by photographic film. In 1932, however, perceiving radio waves with any precision was extremely difficult, for instruments were lacking. Therefore, the development of radio astronomy was delayed for some 20 years.
iAntarctic Land
1820 A.D.
ANTARCTICA
After Captain Cook's crossing of the Antarctic Circle, much of the exploration of Antarctic waters was conducted by sealers and whalers, as a by- product of their search for seal fur and whale blubber and oil (whale oil being a major source of illumination in the lamps of Europe and America).
On November 16, 1820, an American sealer, Nathaniel Brown Palmer (1790-1877), sighted land south of Tierra del Fuego. Also in that year, and perhaps several months earlier, a British naval commander, Edward Bransfield (ca. 1795-1852), sighted land in the same general area. At the time there was no way of knowing what the nature of the land was, but we now know that it is a long, curved peninsula that we call the Antarctica peninsula. It is the only part of the Antarctic landmass that sticks up well north of the Antarctic Circle.
Also in 1820, a Russian explorer, Fabian Gottlieb von Bellingshausen (1778-1852), discovered a small island, which he named Peter I Island, about 150 miles south of the Antarctic Circle.
We might list Palmer, Bransfield, and Bellingshausen as joint discoverers of Antarctic land.
6The Apatosaurus
1877 A.D.
UTAH, UNITED STATES
As you can see, Apatosaurus -- also known as Brontosaurus -- had a very long neck. It took advantage of its neck to reach the leaves and branches on the tops of trees, using its massive tail for support while standing on its rear legs. It had to eat tons of plants and leaves every day just to maintain its incredible body weight. These were not slow, defenseless creatures, either. In a battle with its enemy Allosaurus, Apatosaurus could have reared up on its hind legs and then brought its entire body down on its predator. Apatosaurus' long tail was also not a bad whip. The first Apatosaurus was discovered by Otheniel Marsh in 1877. Recently, Dinamation International Society has discovered what may be the largest Apatosaurus skeleton ever found. It may have measured up to 95 feet long!
÷Space Casualties
1967 A.D.
CAPE CANAVERAL, FLORIDA
The Space Age, now 10 years old, saw its first human casualties. On January 27, 1967, three American astronauts died while an Apollo capsule was being tested on the ground. They were Virgil Ivan (Gus) Grissom (1926-1967), who had orbited in Gemini 3 in 1965; Edward White (1930-1967), who had been the first American to take a spacewalk in 1965, and Roger Bruce Chaffee (1935-1967).
On April 24, 1967, the Soviet spacecraft Soyuz made its first flight, but during the return to Earth, the ship became tangled in its parachute lines and the cosmonaut, Vladimir Mikhaylovich Komarov (1927-1967), who had piloted the first multiperson spacecraft in 1964, died. He was the first person to die in the course of an actual spaceflight.
äApollo XIII
1970 A.D.
HOUSTON, TEXAS
A near disaster in space took place in 1970 when Apollo XIII, en route to the Moon, underwent a loss in oxygen in the main chamber. The three astronauts crowded into the lunar module and maneuvered their way safely back to Earth while the world watched. Although the mission was a failure, the ingenious survival of the intrepid astronauts caught the admiration of all.
ⁿAqueducts
700 B.C.
NINEVEH
As cities grew, supplying what was needed to so many people so densely packed together became a problem. Air itself, the most immediate and pressing necessity, was available everywhere more or less (though the use of fires in every house could fill that air with unpleasant smoke).
Water was more of a problem. Cities are usually built where there is a water supply, but as they grow, the water supply may become insufficient. Wells within the city limits or just outside may not supply enough. It may then become necessary to fetch water from some distance, either through canals or tunnels or along artificial structures of masonry.
These last are called aqueducts (from Latin words meaning "a drawing off of water") and by 700 B.C., Sennacherib, who was king of Assyria from 704 to 681 B.C., had an aqueduct constructed that would bring water into his capital, Nineveh. At about the same time, Hezekiah, king of Judah from about 715 to about 686 B.C., built an aqueduct to supply Jerusalem with water.
Arabic Numerals
1202 A.D.
PISA, ITALY
An Italian mathematician, Leonardo Fibonacci (ca. 1170-after 1240), had occasion to travel widely in North Africa, since his father was a merchant. There he learned of Arabic numerals and positional notation, which had been advocated by Arabic mathematician Muhammad ibn Al-Khwarizmi (780-850).
Fibonacci wrote a book on the subject in 1202, Liber Abaci (Book of the Abacus). This served to introduce Arabic numerals to Europe, but Roman numerals held their own for three more centuries before succumbing.
Arches and Architecture
750 B.C.
ROME, ITALY
The easiest way to build an opening is to set up two vertical pieces of wood, stone, or other material and then balance a horizontal piece above the two.
The horizontal piece, unsupported in the middle, can break with relative ease, and the weakness increases as it grows longer. If instead one uses relatively small pieces arranged in a vertical semicircle so that each piece helps support the piece above, and if one uses mortar to make the pieces adhere to each other, one has an arch.
An arch can span a much wider distance and carry a much heavier load than a horizontal piece can.
Small, primitive arches were used as early as Sumerian times, but a true arch, properly built for maximum strength, showed up for the first time among the Etruscans in 750 B.C.
2The Archeopteryx
1861 A.D.
WORLD
Although the giant dinosaurs, whose fossil relics had been dug up over the past 40 years, were the most dramatic remnants of ancient life, the most important single fossil was not a giant, but a relatively small lizardlike animal that was discovered in 1861. It is estimated now to be about 140 million years old.
It left a clear impression in a rock, which showed that it had a head possessing teeth and no beak, a long neck, a long tail, and a flat breastbone -- all very lizardlike. There was, however, one all-important added feature. The "lizard" had feathers. The imprints of those feathers are unmistakable. They are in a double row down the length of the tail and are also present along the forelimbs.
In the world today, every known bird has feathers, and no living thing that is not a bird has them. Therefore, it is necessary to think of this fossil as representing a very primitive bird. It is called archeopteryx (from Greek words meaning "ancient wing").
The archeopteryx is the best-known example of an ancient life form that seems to lie exactly between two major groups of today's life forms. It is half reptile and half bird and is therefore a perfect example of a reptile in the process of becoming a bird. No other fossil discovered before or since is such a clear example of evolution at work.
∞The Arctic Circle
870 A.D.
ARCTIC CIRCLE
The Vikings were sea-raiders and the terrors of the European coasts in the ninth and tenth centuries, but they were great sea-explorers as well. Among Europeans, they were the greatest since the Phoenicians, 13 centuries earlier.
A Viking named Ottar sailed northward in 870 out of nothing more than sheer curiosity, apparently. He said he wanted to see how far north land existed, and whether it was populated. He succeeded in rounding the northern end of the Scandinavian peninsula (North Cape), and sailing on eastward, he eventually entered the White Sea.
When passing the North Cape, Ottar was 125 miles north of the Arctic Circle. He was the first human being, as far as we know, ever to cross the Arctic Circle by sea.
]The Arctic Ocean
1893 A.D.
ARCTIC OCEAN
Nansen, who had crossed Greenland, now made ready to explore the Arctic Ocean.
He designed a strong ship that would be lifted, rather than crushed, when the ocean about it froze. He named the ship Fram (Forward) and set sail in 1893 with 13 men aboard. His idea was to let himself be frozen in by the sea ice and carried along with it in its slow swirl about the Arctic Ocean, perhaps reaching the North Pole itself.
He remained on the ship for a year and a half, and although he never reached the North Pole, he got closer to it (86.23 degrees North) than anyone before him ever had.
Φ The Arecibo Radio Telescope
1963 A.D.
PUERTO RICO
In 1963 the largest single radio telescope ever built was put into use. It was located about 8 miles south of Arecibo, Puerto Rico, and is about 1,000 feet across. It is not steerable, however, but is fixed in place.
Φ Argon
1894 A.D.
GREAT BRITAIN
Ever since English chemist William Prout (1785-1850) had suggested that all atoms were built up of hydrogen atoms, chemists had been checking the atomic weights of various elements with greater and greater accuracy. The fact that so many atomic weights were not multiples of hydrogen's seemed to disprove Prout's hypothesis.
Twelve years before, for instance, the British physicist John William Strutt, Lord Rayleigh (1842-1919), had shown that the atomic weight of oxygen, although usually considered to be 16 times the atomic weight of hydrogen, is actually 15.882 times the atomic weight of hydrogen.
Rayleigh went on to measure the atomic weight of nitrogen and then encountered a puzzle. Whereas oxygen always had the same atomic weight no matter how it was prepared, nitrogen did not. Nitrogen prepared from the atmosphere consistently showed a slightly higher atomic weight than nitrogen prepared from a variety of nitrogen-containing compounds.
Rayleigh could not find a suitable explanation for this and wrote a letter to the journal Nature, asking for suggestions. The British chemist William Ramsay (1852-1916) rose to the challenge. He remembered having read that British chemist Henry Cavendish (1731-1810) had tried to combine the nitrogen of air with oxygen and had found that a small bubble of gas remained behind, which would simply not combine with oxygen. Cavendish had thought there might be some small quantity of gas in the atmosphere that was more dense than nitrogen, and more inert, too, but had not pursued the matter.
Ramsay repeated the experiment, and he too found himself with a small bubble of gas left over. He had spectroscopic techniques, however, which Cavendish had not had. Ramsay heated the bubble of gas, studied the spectral lines it emitted, and found them to be in positions that fitted no known element.
Clearly here was a hitherto-unknown gaseous element, which made up about 1 percent of the atmosphere. It was completely inert and would not react with any substance. It was also denser than nitrogen. The presence of this new gas as an impurity in the nitrogen obtained from air gave the nitrogen an abnormally high atomic weight, whereas nitrogen obtained from chemicals without any admixture of this impurity gave the true atomic weight.
The discovery was announced on August 13, 1894, and the new gas was named argon, from the Greek word for "inert." As a result, Rayleigh received the Nobel Prize in physics and Ramsay the Nobel Prize in chemistry in 1904.
╥Ariel and Umbriel
1851 A.D.
LONDON, ENGLAND
The last large satellite, Triton, had been discovered by Lassell five years before, but there were smaller satellites to be found. In 1848 Lassell had discovered an eighth satellite of Saturn, which he named Hyperion after still another of Saturn's (Cronos's) brother-Titans in the ancient myths. This satellite was discovered almost simultaneously by the American astronomer George Phillips Bond (1825-1865).
Then, in 1851, Lassell discovered a third and fourth satellite of Uranus. He followed Herschel's precedent by naming them after spirits in English literature. One he named Ariel after a spirit in Shakespeare's The Tempest and the other Umbriel after a spirit in Pope's The Rape of the Lock.
cLanding on the Moon
July 21, 1969
HOUSTON, TEXAS
For centuries people dreamed of what it would be like to go to the moon. They imagined methods of getting there and strange lunar creatures. But on July 20, 1969, it really happened. Astronaut Neil Armstrong first set foot on the moon. "That's one small step for man, one giant leap for mankind," he said.
Armstrong and Edwin "Buzz" Aldrin landed on the moon in the Eagle lunar module. While on the surface they performed various experiments, planted a U.S. flag and explored the area around their landing site. Meanwhile, Michael Collins orbited the moon in the Apollo 11 "Columbia" command module.
This great scientific accomplishment was prompted by a scare. In April 1961, Soviet Cosmonaut Yuri Gagarin became the first man in space. Jolted by this Soviet accomplishment, the United States decided it must catch up.
And it did. Through a series of space programs, from the single seat Mercury capsules to the slightly larger two-man Gemini missions, and finally to the three-man Apollo spacecraft, America gradually obtained the expertise in space exploration necessary for a trip to the moon.
ïArteries and Veins
300 B.C.
GREECE
The Greek physician Praxagoras (4th century B.C.) distinguished between the two kinds of vessels we know as arteries and veins. However, he thought arteries carried air (they are usually empty in corpses). That turned out to be wrong, but the idea remains in the name, which is from Greek words meaning "air-carrier." He also noticed that the brain and the spinal cord were connected.
[The Development of Artillery
1439 A.D.
PARIS, FRANCE
Charles VII, now truly king, bestirred himself to reform his army, hiring two brothers, Jean and Gaspard Bureau, to reorganize the artillery. They improved the design of cannon and the quality of gunpowder, oversaw the production of cannon in greater numbers, and placed them under the control of specialists.
Charles VII's armies became the first to make an able and systematic use of artillery. This marked the end of the medieval fashion of making war and it completed the job of restoring the cavalry to its one-time position as a mere auxiliary arm.
City walls, which, unlike personal armor, were impervious to longbows, began to fall before the new artillery. Just as the French could not understand why the longbow won, so the English could not understand why it stopped winning, and they proceeded to lose the Hundred Years War.
{Ascorbic Acid
1932 A.D.
U.S.A.
In 1932 the American biochemist Charles Glen King (1896-1988) concluded his investigations of vitamin C, in the course of which he had isolated the vitamin and determined its structure. The substance had a six-carbon molecule closely resembling those of the sugars and was named ascorbic acid, from Greek words meaning "no scurvy." The work of Lind was thus successfully concluded.
Two weeks later, Szent-Györgyi reported that his hexuronic acid was vitamin C, and he was right. This set off a violent and bitter controversy over precedence, which continued throughout the long lives of both men (each lived into his 90s).
ëThe Asian Continent
1990 A.D.
ASIA
Roughly defined, Asia stretches from the Ural Mountains in Russia in the west to Japan and the Pacific Ocean in the east and from the Arctic Sea south to India and Indonesia.
Like a wide belt across the length of Asia is the vast steppe, a swath of grassland that stretches from east to west. Though almost devoid of people compared to the densely populated southlands of the continent, the steppe has been important in the history of the world. From it have burst such conquerors as the Huns and Mongols, who ravaged both China and Europe. The southern half of the continent is much more broken up geographically, and thus, culturally as well. The vast Himalayan mountain range, which boasts the tallest mountain in the world, Mt. Everest, has to a great degree isolated Tibet, India and Burma from China and Central Asia. In the far east, wide stretches of water separate Japan, the Philippines and Indonesia from the rest of Asia.
Despite these obstacles, China and India in particular have been extremely important in the history of Asia.
Just as civilization developed around the Nile River and around the Tigris and Euphrates rivers in the Middle East, so it happened in the East. In China people settled around the Yellow River and in India around the Indus River.
In a succession of dynasties and warring kingdoms, China expanded to the south and west and developed a culture advanced in technology, art, literature and philosophy.
India is important as the birthplace of Hinduism and more importantly, of Buddhism, which has spread throughout Asia.
Today, Asia is the most populous continent in the world, with more than three billion people.
YThe Amino Acid Asparagine
1806 A.D.
FRANCE
Vauquelin, who had earlier discovered metallic elements such as chromium and beryllium, isolated a substance from asparagus, which he called asparagine. In itself, it might not have seemed important, but as was eventually realized, it was the first to be isolated of a set of compounds extremely important to life, called amino acids.
╠The Assembly Line
1908 A.D.
DETROIT, MICHIGAN
During the first 20 years of its existence, the automobile had been improved greatly and manufactured in greater numbers. It remained very largely a toy of the rich, however, rather as yachts are today.
The man who changed that was the American industrialist Henry Ford (1863-1947). He had built his first automobile in 1893 and started a car- manufacturing company in 1899. His aim was to produce cars in quantity (mass production) and to make them cheaply enough to put them within reach of middle-class Americans.
His key innovation came in 1908, when he thought of dividing the manufacture of cars into steps, each of which could be performed simply by a single worker. He then placed the future car on a moving belt that brought it to different workers in succession, each of whom performed the assigned task over and over, with all necessary tools and parts within reach. What started at one end of the assembly line was a mere skeleton of a car. What rolled off the other end was a complete, functioning automobile, including a gasoline supply so that it could be driven away.
Ford produced a series of models identified by letters of the alphabet and finally considered the Model T suitable for mass-production. It cost only $950 to begin with, but the price dropped in succeeding years, eventually reaching a low of $290. For the first time, the average man could afford to buy a car, and the automobile age -- still in full swing today -- began.
¬The Element Astatine
1940 A.D.
BERKELEY, CALIFORNIA
In 1940 Segre, who had isolated technetium, bombarded bismuth (element number 83) with alpha particles. If an alpha particle struck the bismuth and remained, or even if a neutron were emitted thereafter, the bismuth would have gained two protons and the result would be the undiscovered element number 85. This was accomplished in 1940, but World War II interrupted, and it wasn't until the war was over that they could confirm their finding.
The new element was quite unstable. Its most long-lived isotope had a half- life of only 8.3 hours. It was therefore named astatine, from the Greek word for "unstable." It belonged to the same group as fluorine, chlorine, bromine, and iodine, which is why it received the -ine ending.
With the discovery of astatine, only one gap remained in the entire periodic table from element number 1 (hydrogen) to element number 94 (plutonium), and that was element number 61.
░Asteroids
1802 A.D.
BERLIN, GERMANY
Olbers and his group of German scientists were shaken in their plan to search for a planet with an orbit between those of Mars and Jupiter by Piazzi's discovery of Ceres). Ceres was so small, however, that it scarcely seemed to be a planet. Olbers's group decided to continue the search.
In 1802 they discovered another planet between Mars and Jupiter, and they named it Pallas, one of the names of the goddess Athena. In 1804 they found still another, and in 1807, a fourth. These were named Vesta and Juno, after two of the sisters of Jupiter (Zeus). The three new planetary bodies, however, were even smaller than Ceres.
Herschel suggested they be called asteroids (Greek for "starlike"), because in the telescope they seemed mere dots of light, like stars (because of their small size) rather than orbs, like the larger planets.
Eventually it was realized that there were a vast number of such bodies, perhaps as many as 100,000 of them, between the orbits of Mars and Jupiter. This region came to be called the asteroid belt. Ceres was the largest of the asteroids (hence the first discovered), containing about a tenth the mass of all the other asteroids put together.
ZAstigmatism
1825 A.D.
ENGLAND
Spectacles for the far-sighted were some five centuries old, and for the near- sighted, almost as old. It is possible to have difficulty seeing, however, even if one is neither, if the cornea of the eye is not perfectly curved. Such a condition is known as astigmatism (from Greek words meaning "no spot," because a small spot cannot be seen sharply by astimatics) and can be combined with either near- or far-sightedness.
The British astronomer George Biddell Airy (1801-1892) suffered from astigmatism, and he was the first, in 1825, to design eyeglass lenses to correct that condition.
RAsteroid Photography
1891 A.D.
GERMANY
It had been almost a century now since the first asteroid was discovered by Piazzi, and others had been discovered in astonishing numbers. By 1891, 322 asteroids had been discovered and their orbits calculated.
Each one, however, had been discovered by eye; an object would be seen that looked like a rather dim star but would be shifting position against the starry background. If it moved at a certain rate, it was almost certainly an asteroid.
In 1891 it occurred to a German astronomer, Maximilian Franz Joseph Cornelius Wolf (1863-1932), to make the discoveries by photography. If a telescope is set to turning in time with the movement of the vault of the sky (a movement that arises because of the rotational motion of the Earth), then all the stars in the telescopic view will show up on the film as sharp points. An asteroid, however, will move with respect to the stars and so will show up as a small dash. The object responsible for the dash can then be put under observation and its orbit eventually calculated.
In this fashion, Wolf discovered the 323rd asteroid, which he named Brucia, and went on to discover others. In the course of his life, he discovered 500 asteroids. Nowadays, the orbits of nearly 2000 asteroids are known, and it is estimated that there may be as many as 100,000 asteroids that are at least a mile across.
Astrochemistry
1968 A.D.
WORLD
When the hydroxyl group had been detected in interstellar gas clouds, astronomers had been surprised. It seemed odd that enough individual atoms would strike each other and cling, forming two-atom combinations like the hydroxyl group, to be detectable at astronomic distances. It was thought there would be virtually no chance for combinations of three or more atoms.
The increasing ability to detect microwave radiation with great precision, however, led to further surprises. In 1968 microwave frequencies characteristic of water molecules (with three atoms each) and ammonia molecules (with four atoms each) were detected in interstellar gas clouds. This was the beginning of what came to be called astrochemistry. Since then, more and more complicated atom groupings have been detected, some involving as many as 13 atoms.
All but the very simplest are composed of chains of carbon atoms, which once again points up the uniqueness of the carbon atom as a component of complex groupings, and therefore of life as we know it.
óSelf-Starting Automobiles
1911 A.D.
U.S.A.
The automobile still had to be started manually by inserting a crank into the front of the car, where it could grip the rotor of the engine, forcing it to turn and "catch." That took a great effort, and sometimes when the engine caught, the crank began to turn at great speed, pulled out of the cranker's hand, and broke his arms.
The American inventor Charles Franklin Kettering (1876-1958) invented an electric starter in 1911 that would do the job at the turn of a key. It was used in the 1912 Cadillac and quickly grew popular. With the crank gone, automobiles could be started and driven by far more people, which greatly spread the automobile way of life.
ªThe First Scientific Device
140 A.D.
ALEXANDRIA, EGYPT
Claudius Ptolemaeus (2nd century), better known as Ptolemy, was the last important astronomer of the ancient world. He wrote a summary of ancient astronomy, known later to the Arabs as Almagest (the greatest). He drew largely from Hipparchus.
In this synthesis, he described the Earth as the center of the Universe and all the planets as going around it in combinations of circular motions. In order to account for the visible motions of the planets across the skies, those combinations of circular motions had to be complicated indeed, but Ptolemy worked out mathematical methods for predicting planetary motions that seemed adequate to his contemporaries and to future generations for 14 centuries. (His chief instrument was an astrolabe, a device for determining the latitude of the heavenly bodies. It had been invented a couple of centuries before and is considered the oldest of scientific instruments.)
HThe Atlantic Ocean
500 B.C.
GIBRALTAR
The Phoenician navigators, who had made themselves at home the length and breadth of the Mediterranean over the past six centuries, even ventured through what we now call the Strait of Gibraltar and into the Atlantic Ocean. One of the driving forces behind them was the depletion of eastern Mediterranean tin mines, since tin is a rather rare metal. (This was the first time that human beings had to contend with the loss of a necessary resource.) Since tin was an essential component of bronze, it had to be obtained somewhere; if not in the Mediterranean lands, then elsewhere.
The Phoenicians found Tin Islands somewhere in the Atlantic. They kept the location secret in order to retain a monopoly of the tin ore, but it is thought that they reached Cornwall, at the southwestern tip of England, where tin ore was produced right into modern times.
By 500 B.C., the Phoenicians are even reported to have circumnavigated Africa, a voyage that took them three years. The Greek historian Herodotus (ca. 484-between 430 and 420 B.C.), writing half a century later, described the voyage but doubted the whole thing because the Phoenicians reported that in the far south the noonday Sun was in the northern half of the sky. Herodotus felt this to be impossible.
We moderns, however, know that the Sun is always in the northern half of the sky when seen from the South Temperate Zone. The Phoenicians would not have made up such an apparently ridiculous story if they had not actually witnessed it, so the very item that caused Herodotus to doubt the story convinces us that it must be true.
░Atomic Clocks
1949 A.D.
US NAVAL OBSERVATORY, WASH DC
Ever since Dutch astronomer Christiaan Huygens (1629-1695) had invented the pendulum clock in 1656, scientists had depended on accurate time measurements in conducting their experiments and searched always for more and more accurate ways of measuring time.
Eventually the search for natural cyclic movements that were both precise and constant worked down to the molecular level. An ammonia molecule, for instance, vibrated back and forth, taking up its two possible tetrahedral positions alternately, about 24,000,000,000 times per second. At constant temperature, this vibration remained very constant.
In 1949 the American physicist Harold Lyons (b. 1913) was the first to harness this molecular vibration to time-keeping purposes. It was the first atomic clock. As atomic clocks of ever-greater precision were devised, physicists could eventually time events to a millionth of a trillionth of a second.
Elliptical Electron Orbits
1915 A.D.
MUNICH, GERMANY
The quantized atom of Danish physicist Niels Henrik David Bohr (1885-1962) did not explain all the fine details of spectra. Some dark lines that seemed simple, on closer investigation proved to consist of groups of narrow, closely spaced lines.
The German physicist Arnold Johannes Wilhelm Sommerfeld (1868-1951) felt the answer lay in the fact that electron orbits were more complicated than Bohr had suggested. Bohr had made use of perfectly circular orbits, but the orbits (like planetary orbits) might also be elliptical.
Sommerfeld used Albert Einstein's (1879-1955) theory of relativity to calculate the elliptical orbits and quantum theory to show that only certain kinds of ellipses were possible. The combination of circular and elliptical orbits explained some of the details of the spectra that Bohr's original treatment had left unexplained.
For this reason, people sometimes speak of the Bohr-Sommerfeld atom. It made use of the two great physical theories of the twentieth century, relativity and quanta.
Atomic Size
1908 A.D.
U.S.A.
Einstein had devised an equation showing how one might calculate the size of atoms and molecules from Brownian motion. In 1908 Perrin, who had shown that cathode rays consisted of particles carrying a negative electric charge, set about making the calculation.
Through a microscope, he counted the number of small particles of gum resin suspended at different heights in water. That they were suspended at all was the result of recoil from collisions with water molecules; in other words, from Brownian motion. From his observations and from Einstein's equations, Perrin could make his determination.
For the first time, the approximate size of atoms could be deduced from an actual observation. Atoms, it turned out, are about a hundred-millionth of a centimeter in diameter. In other words, 250,000,000 of them, lined up side by side, would stretch about an inch.
This was the final demonstration of the real existence of atoms. They were not merely a convenient hypothesis designed to make chemical calculations easier.
ªThe Atomic Theory
1803 A.D.
ENGLAND
From the time of Robert Boyle's experiments on the compression of gas, the evidence for the atomic nature of matter had been accumulating.
In 1803 an English chemist, John Dalton (1766-1844), advanced a summary of atomic thinking, backing it up with the evidence that had accumulated, including particularly Proust's law of definite proportions and his own investigations of the way in which gases behaved. (In 1808 he gave his arguments formally in a book entitled New System of Chemical Philosophy.)
Essentially, Dalton returned to the Greek notions of Democritus that all matter was made up of tiny, indivisible particles. Dalton even used Democritus's word atom for these particles. The difference was that Democritus's theory was based on speculation only, whereas Dalton's was based on a century and a half of careful chemical observation.
The Greeks, being geometers, naturally thought that atoms differed among themselves in shape. Dalton, in whose time weight and measurements had grown important, maintained that the difference was one of weight, and he pioneered the concept of atomic weight.
For instance, 8 grams of oxygen will combine with 1 gram of hydrogen to form 9 grams of water. Suppose that water is formed through a combination of one atom of oxygen and one atom of hydrogen (the result would be a water molecule). In that case, one atom of oxygen would have to be eight times as massive as one atom of hydrogen. If hydrogen was supposed to have an atomic weight of 1, oxygen would have one of 8.
Of course, water might be made up of molecules containing any number of oxygen and hydrogen atoms. Dalton supposed it to be built up of one of each merely because that was the simplest possible situation. Until such time as more was known about molecular makeup, the values obtained for atomic weights would be dubious. In Dalton's table of atomic weights (the first ever compiled), many were indeed wide of the mark.
Atomic Weights
1818 A.D.
SWEDEN
Berzelius was one of those who labored to determine atomic weights, and no one in his time was as careful as he. He ran 2,000 analyses on various chemicals after 1807 and used the results as a basis for working out atomic weights. In 1818 he felt justified in publishing a table of his results.
Despite the fact that he ignored Avogadro's hypothesis and made mistakes for that reason, many of his figures were reasonably correct. His atomic weight table was far more correct than Dalton's and was the first in which we can recognize many modern values.
Berzelius also presented the molecular weights of various compounds.
These are easily obtained if you know the weight of the individual atoms and know which atoms and how many of each go to make up the molecules of a compound.
Early Cattle
1627 A.D.
WORLD
The cattle that populate the world in their hundreds of millions and supply us with beef, milk, butter, cream, cheese, and leather are descended, it is supposed, from the aurochs, large, black animals standing 6 feet at the shoulder and with long, forward-curving horns. As cattle multiplied, the aurochs declined, until the only ones left in the world were a herd in Poland. The herd continued to dwindle, and the last one died in 1627. This was an example of how easy it is for large and magnificent animals to vanish.
╡Magnetic North Pole
1881 A.D.
ARCTIC CANADA
Since the time of English physicist William Gilbert (1544-1603), it had been understood that the Earth must have a North Magnetic Pole and a South Magnetic Pole. The general (and rather natural) feeling was that the magnetic poles would be near, or perhaps exactly at, the rotational poles. However, the Arctic and Antarctic regions of Earth, cold and desolate as they were, could only be explored with great difficulty.
It was not until June 1, 1831, that the North Magnetic Pole was actually reached. The feat was accomplished by a Scottish explorer, James Clark Ross (1800-1862). He found his compass pointing straight down, on the western shore of Boothia Peninsula, at 70.85 degrees North Latitude and 96.77 degrees West Longitude. The pole was discovered only because it was 2,100 miles from the geographic North Pole and therefore relatively accessible. In fact, it was only a few hundred miles north of the Arctic Circle.
⌐Australia
1990 A.D.
AUSTRALIA
Australia is the only continent in the world that is also a single country. It was originally inhabited by aboriginal peoples who are believed to have worked their way down the chain of islands that are now Indonesia to settle the continent.
Australia was later claimed by Great Britain, which initially operated parts of it as a penal colony for those convicted of crimes in England.
Australia is the most lightly populated continent in the world, with just 17 million people, or an average of 5.2 per square mile.
The highest point of this island continent is Mount Kosciusko, which rises 7,310 feet above sea level in New South Wales. The lowest point is Lake Eyre in South Australia, a point 52 feet below sea level.
New Zealand, the smaller islands to the right of the picture, were first inhabited by the Maori people, who lost the area to English immigrants following the costly (for both sides) Maori Wars.
dExploring Australia
1768 A.D.
AUSTRALIA
Transits of Venus occur in pairs, eight years apart, with over a century between pairs. Since there was one in 1761, there would be another in 1769. In 1768, therefore, the English navigator James Cook (1728-1779), usually called Captain Cook, was sent out on a voyage to the Pacific Ocean. He was to observe the transit from the newly discovered island of Tahiti.
In the course of this voyage, he was the first to explore, thoroughly, the shores of Australia and to get an idea of its size. Though earlier explorers had spied its shores, it was Cook whose reports were sufficiently detailed to bring the land clearly to European attention. For that reason, he is usually considered the discoverer of Australia. This, and two more voyages in the years following, made Cook the most famous navigator since Magellan. Cook crisscrossed the Pacific Ocean and finally demonstrated that it had no significant land areas in it. With Australia, the last major habitable land area on Earth had been discovered.
In the course of his voyages, Cook made use of Lind's dietary discovery and lost only one man to scurvy.
îThe Automobile
1885 A.D.
GERMANY
Until the invention of the steam engine, the dream of a carriage that would move without a horse pulling it (a "horseless carriage") had belonged to the world of myths and legends. The steam-engine is supposed to have been put into action as early as 1769, but such steam-powered vehicles were bulky, clumsy, and slow. Even fairly advanced ones, built much later, took time to start, because water had to be heated and boiled first.
The coming of the internal-combustion engine, especially the Otto four- stroke engine, offered a much better hope. What was needed now was an appropriate fuel, and eventually that turned out to be gasoline, a petroleum fraction with smaller molecules than those of kerosene, so that it vaporized more easily and burned more readily.
The first working automobile with a gasoline-burning internal-combustion engine was built in early 1885 by a German mechanical engineer, Carl Friedrich Benz (1844-1929). Its wheels looked like bicycle wheels, and there were three of them, a smaller one in front and two larger ones in back. It ran at a speed of 9 miles per hour, and it was the forerunner of all that was to follow.
┤ Explaining Atomic Weights
1811 A.D.
ITALY
It was clear that all gases expanded by the same amount as temperature rose, provided the pressure remained constant. In 1811 an Italian physicist, Amedeo Avogadro (1776-1856), suggested that this might mean that all gases -- at the same volume, pressure, and temperature -- were made up of the same number of particles. This came to be called Avogadro's hypothesis.
If this is so, since water upon being broken up by an electric current decomposes into hydrogen and oxygen, with hydrogen having twice the volume of oxygen, then twice as many particles of hydrogen must be formed as of oxygen.
This in turn makes it appear that water particles are not made up of one hydrogen atom and one oxygen atom, as Dalton had thought, but may be made up, at the simplest, of two hydrogen atoms and one oxygen atom.
In that case, since the oxygen in water has eight times the mass of the hydrogen, the oxygen atom must be eight times as massive as the two hydrogen atoms put together, or 16 times as massive as a single hydrogen atom.
Again, if all gases at a given temperature, pressure, and volume are made up of the same number of particles, and if the density of one gas is twice that of another, the mass of each particle in the first gas is twice that of the other.
Thus, the density of water vapor is nine times that of hydrogen at the same temperature, but since the oxygen atom has 16 times the mass of the hydrogen atom, then the weight of the water particle is 16 + 1 + 1, or 18.
Why isn't the density of the water vapor 18 times that of the hydrogen? It may be because the hydrogen particles are made up, not of single hydrogen atoms, but of combinations of two hydrogen atoms. In similar fashion, Avogadro argued that oxygen and nitrogen particles were made up of two atoms each.
Avogadro distinguished between single atoms and these combinations of atoms that made up the particles of compounds. The combinations of atoms he called molecules (from Latin words for "small masses"). Thus, there was an oxygen atom, and there was also an oxygen molecule made up of two oxygen atoms.
There was a water molecule made up of one oxygen atom and two hydrogen atoms.
And so on.
Avogadro's hypothesis, if fully applied, would explain a great deal about atomic weights and about the atomic constitution of compounds. Unfortunately, the hypothesis was largely ignored for half a century, and chemists remained unnecessarily confused in many ways during that time.
ßThe Weights of Molecules.
1865 A.D.
TURIN, ITALY
The hydrogen molecule is composed of two hydrogen atoms. The hydrogen atom has an atomic weight of just about 1, so that a hydrogen molecule has a molecular weight of 2. Hydrogen gas is made up of hydrogen molecules, and at 0 C and normal atmospheric pressure at sea level, 22.4 liters (5.9 gallons) of hydrogen gas weigh 2 grams. This is the molecular weight in grams, or 1 mole.
Since equal volumes of gases are made up of equal numbers of molecules, according to Amedeo Avogadro's hypothesis, and since each oxygen molecule has a weight of 32, then 22.4 liters of oxygen gas would weigh 32 grams -- or 1 mole.
In fact, 22.4 liters of any gas are likely to weigh 1 mole.
The question is, how many molecules are there in 22.4 liters of a gas? In 1865 the Austrian chemist Johann Joseph Loschmidt (1821-1895) used Maxwell's kinetic theory of gases to calculate what that number ought to be. It turned out to be about 600,000,000,000,000,000,000,000, or 600 billion trillion. Since all this was based on Avogadro's hypothesis, the number was called Avogadro's number.
From Avogadro's number, you could calculate the actual mass of a hydrogen molecule, since it would be two grams divided by 600 billion trillion. A hydrogen atom would have a mass half that, and the mass of other atoms and molecules could be calculated as well.
For the first time, scientists had a notion, and a rather good one, as it turned out, of the mass of the tiny atoms and molecules that made up matter.
ƒBuilding a Basis for Math
1889 A.D.
ITALY
The work of Lobachevsky and others in non-Euclidean geometry had highlighted the importance of choosing different systems of axioms to develop different types of geometry. The work of Boole on symbolic logic seemed to offer a tool for testing the necessary axioms of mathematics generally.
In 1889 an Italian mathematician, Giuseppe Peano (1858-1932), published A Logical Exposition of the Principles of Geometry, in which he applied symbolic logic to the fundamentals of mathematics. He built up a system beginning with undefined concepts for zero, number, and successor, and developed them symbolically into the arithmetic on which all mathematics is based.
'Axial Tilt of Mars
1781 A.D.
LONDON, ENGLAND
The Earth's axis is tipped 23.5 degrees to the perpendicular of the plane of its orbit. It is this which gives Earth its seasons. When the Earth is in that region of its orbit in which its North Pole is tipped toward the Sun, the northern hemisphere has its summer and the southern its winter. When the Earth is in the opposite region of its orbit, with the North Pole tipped away from the Sun, the northern hemisphere has its winter and the southern its summer.
Do other planets have similar characteristics? Herschel was studying the rotation of Mars -- the manner in which its markings moved about it, which Cassini had used to determine the length of the Martian day. It seemed to Herschel that the markings had to move parallel to the Martian equator and that its axis of rotation would have to be perpendicular to that. By determining the axis of rotation in this way, Herschel calculated that Mars had an axial inclination of just about 24 degrees, nearly that of Earth's. This was one more way in which Earth resembled other planets.
╙The First Mechanical Computer
1822 A.D.
CAMBRIDGE, ENGLAND
French mathematician Blaise Pascal (1623-1662) and German mathematician Gottfried Wilhelm Leibniz (1646-1716) had constructed calculating machines, but these were equipped to do only the very simplest tasks.
About 1822 an English mathematician, Charles Babbage (1792-1871), began thinking of something much, much more ambitious. He wanted a machine that could be directed to work by means of punched cards as in a Jacquard loom, that could store partial answers in order to save them for additional operations to be performed upon them later, and that could print the results.
Everything he thought of could be done, but not by purely mechanical means, using the techniques of Babbage's time. He spent virtually the rest of his life trying to build the machine, his plans growing ever more grandiose.
Babbage had conceived the modern computer, but he didn't have the necessary electronic switches. These were not to be developed for another century.
ôEarly Studies of Bacteria
1773 A.D.
DENMARK
Bacteria had just barely been made out by Leeuwenhoek nearly a century before. Since then, microscopists had not been able to do more than just barely see them. In 1773, however, a Danish biologist, Otto Friedrich Muller (1730-1784), managed to make them out well enough to divide them into categories. Some looked like little rods and he called them bacilli (from a Latin word for "little rod"); some were curved into spiral shapes and he called them spirilla.
He was the first to classify microorganisms generally into genera and species after the fashion of Linnaeus, but even he couldn't do very much with the tiny specks that were bacteria.
}Evidence of The Big Bang
1964 A.D.
U.S.A.
The German-born American physicist Arno Allan Penzias (b. 1933) and the American radio astronomer Robert Woodrow Wilson (b. 1936) were attempting to determine the characteristics of any radio-wave emission that might come from the outer regions of the Galaxy. They made use of a big horn-shaped antenna originally built to detect radio reflections from the Echo satellite.
In May 1964 they found an excess of radio-wave emission that they could not explain. When they had accounted for all possible sources of error (including pigeon droppings inside the antenna), they found that there was a distinct background microwave radiation, coming from all directions with equal intensity.
They turned to the American physicist Robert Henry Dicke (b. 1916), who remembered that Gamow had predicted such background radiation would occur as a consequence of the big bang.
The background radiation was characteristic of a universe with an average temperature of 3 degrees above absolute zero, and it could be assumed that the Universe had cooled to that average temperature from that prevailing at the moment of the big bang. The background radiation, as a fossil remnant (so to speak) of the big bang, finally established that event as the very likely mechanism whereby the Universe came into being.
For this discovery, Penzias and Wilson received a share of the Nobel Prize for physics in 1978.
NThe Scientific Method
1620 A.D.
ENGLAND
The English philosopher Francis Bacon (1561-1626) published Novum Organum (New Organon) in 1620. The reference is to Aristotle's Organon, in which the rules of logic were drawn up.
Bacon argued strenuously that deduction might do for mathematics but it would not do for science. The laws of science had to be induced; that is, established as generalizations drawn out of a vast mass of specific observation. Such experimental science had already been put into practice, but Bacon supplied the theoretical backing for it, describing what is today called the scientific method.
PMicroorganisms
1676 A.D.
AMSTERDAM, NETHERLANDS
Microscopists had been looking at minute sections of ordinary living organisms for 20 years and more, but a Dutch microscopist, Antoni van Leeuwenhoek (1632-1723), now surpassed them all.
Whereas other microscopists used combinations of lenses, Leeuwenhoek used small single lenses, but he ground them to perfection, so that they could magnify up to 200 times. He ground a total of 419 lenses in his long lifetime, even though he was already over 40 when he took up this hobby.
In 1676, studying pond water, he found it contained living organisms so small they could not be seen with the unaided eye. He called them animalcules, but we call them microorganisms. By whatever name, Leeuwenhoek had opened up an entirely new microscopic zoo to the astonished eyes of humanity. (In 1677 he detected spermatozoa in semen.)
ΣOrigin of Bacteriology
1872 A.D.
BOSTON, MASSACHUSETTS
Bacteria had been known for two centuries but were so small that till now they had not been studied in detail. French chemist Louis Pasteur's germ theory of disease, however, had brought them into lurid prominence. It turned out that a number of different bacteria were pathogenic. They were the cause of certain diseases and of their contagious character.
A German botanist, Ferdinand Julius Cohn (1828-1898), inspired by Pasteur's work, was the first to treat bacteriology as a special branch of knowledge.
In 1872 he published a three-volume treatise on bacteria that may be considered to have founded the science. He made the first systematic attempt to classify the bacteria into genera and species. He was also the first to describe bacterial spores (the form in which bacteria survive periods of desiccation and other unfavorable conditions by retreating behind a thick cell wall). Bacterial spores are so tenacious of life that they may even survive boiling.
¬The First Plastic
1909 A.D.
U.S.A.
Hyatt's celluloid had been the first important synthetic plastic, but in the 40 years since it had been introduced, there had been no flood of additional plastics on the market.
The real beginning came with the work of a Belgian-born American chemist, Leo Hendrik Baekeland (1863-1944).
It often happened in organic chemistry that hard tarry residues fouled chemical equipment and then could not be removed. Baekeland tried to find some solvent that would remove them. For the purpose, he deliberately reacted phenol with formaldehyde to form such a residue, and then searched for a solvent. He couldn't find one.
It occurred to him that if the residue was so resistant to solvents, it might have a useful application in its own right as an inert, strong, and cheap material, so he began to concentrate on forming the resinous mass more efficiently and making it still harder and tougher. By using the proper heat and pressure, he obtained a liquid that solidified and took the shape of the container it was in. Once solid, it was hard, water-resistant, solvent-resistant, and an electrical insulator. Yet it could be cut without trouble and was easily machined.
In 1909 he brought this substance (which he named Bakelite, after himself) on the market. Bakelite was the first of the thermosetting plastics (one that once set will not soften under heat) and has been useful ever since. It sparked the modern development of plastics.
¿Balloon Angioplasty
1977 A.D.
WORLD
Coronary atherosclerosis could now be treated by performing bypass operations. An alternative, nonsurgical technique was developed in 1977. This called for tiny balloons being led into the affected arteries by means of catheters. The balloons then expanded and pressed back the plaques, widening the bore of the arteries. Such balloon angioplasty slowly became more popular as an alternative to bypass operations.
The Ballpoint Pen
1938 A.D.
HUNGARY
In 1938 two Hungarian brothers, Ladislao Biro and Georg Biro, designed a ballpoint pen: ink from an internal reservoir coated a tiny ball at the end of the pen, and the ball rolled, depositing ink on the paper.
When the design was sufficiently improved and a high-viscosity ink was developed that would not blot, streak, or stain the fingers and that dried almost at once, the ballpoint pen took over. Fountain pens and inkwells became almost obsolete, and even pencils and erasers became less prominent.
bThe Big Bang
1927 A.D.
BELGIUM
Russian mathematician Alexandrovich Friedmann had developed the theoretical concept of an expanding universe and in 1927 the Belgian astrophysicist Georges-Henri Lemaître (1894-1966) drew what seemed a natural conclusion.
If the Universe was expanding as time went forward, then if we imagined the situation reversed and looked back in time, we should see the Universe contracting. (It would be as though we had taken a film of the expanding Universe and were running it backward.)
If we looked forward, the Universe might well expand forever, but if we look backward, the contraction had to be limited. Eventually, at a point far enough back in time, all the matter of the Universe would be compressed into one relatively small body, which Lemaître called the cosmic egg.
This cosmic egg apparently exploded in what came to be called the big bang and started the expanding Universe that now exists. Of course, Lemaître could offer no scientific explanation of where the cosmic egg came from and just how its explosion led to the present Universe. Physicists have been trying to work that out ever since.
)The First Barometer
1643 A.D.
PISA, ITALY
It had long troubled mining engineers and others that pumps could not lift water more than 33 feet above its natural level. The usual pump produced a partial vacuum, which the water rushed upward to fill, but apparently the rush had its limits. The Italian physicist Evangelista Torricelli (1608-1647) worked for Galileo in that scientist's last years, and Galileo suggested that his assistant investigate this pumping problem.
It occurred to Torricelli that the water was lifted not because it was pulled up by the vacuum, but because it was pushed up by the normal pressure of air. After all, the vacuum in the pump produced a low air pressure and the normal air outside the pump pushed harder.
In 1643, to check this theory, Torricelli made use of mercury. Since mercury's density is 13.5 times that of water, air should be able to lift it only 0/0113.5 times as high as water, or 30 inches. Torricelli filled a 6-foot length of glass tubing with mercury, stoppered the open end, upended it in a dish of mercury, unstoppered it, and found the mercury pouring out of the tube, but not altogether: 30 inches of mercury remained in the tube, as expected. Above the mercury in the upended tube was a vacuum (except for a small quantity of mercury vapor). It was the first one ever artificially created -- a Torricellian vacuum.
Torricelli noticed that the height of the mercury column varied slightly from day to day and surmised correctly that the atmosphere possessed a slightly different pressure at different times. He had invented the first barometer.
TThe Ship of the Deep
1948 A.D.
SWITZERLAND
Beebe explored the deeper layers of the ocean with his bathysphere.
The bathysphere, however, was a purely passive device suspended from a ship by a lifeline. It could not move or maneuver independently.
What was needed was a vessel that could move about in the ocean at any depth. Such a device was invented by the Swiss physicist Auguste Piccard, who had already explored the stratosphere by balloon.
He called the new device a bathyscaphe (ship of the deep). It used a heavy ballast of iron pellets to take it down and a "balloon" containing gasoline to give it buoyancy. It jettisoned the iron pellets to rise.
In 1948 the bathyscaphe descended, with a man on board for the first time, to a depth of 4,500 feet. Over the next 15 years, bathyscaphes penetrated the depths of the ocean, finding life at even the lowest levels.
ºThe Electric Battery
1800 A.D.
COMO, ITALY
Italian anatomist Luigi Galvani (1737-1798), noting that dead muscle twitched when touched simultaneously by two different metals, had decided that electricity was involved and that it originated in the muscle. The Italian physicist Alessandro Giuseppe Volta (1745-1827) thought the electricity originated in the metals.
He began to experiment with different metals in contact and was soon convinced that he was correct. In 1800 Volta constructed devices that would produce electricity continuously if it was drawn off as produced. This created an electric current, which turned out to be far more useful than the nonflowing electric charge of static electricity.
At first Volta used bowls of salt solution to produce the flow. The bowls were connected by means of arcs of metal dipping from one bowl to the next, one end of the arc being copper and the other being tin or zinc. Since any group of similar objects working as a unit may be called a battery, Volta's device was an electric battery -- the first in history.
Volta then made matters more compact and less watery by using small round plates of copper and zinc, plus disks of cardboard moistened in salt solution. Starting with copper at the bottom, the disks, reading upward, were copper, zinc, cardboard, copper, zinc, cardboard, and so on. If a wire was attached to the top and bottom of this battery, an electric current would flow when the circuit was closed.
âThe Storage Battery
1859 A.D.
FRANCE
All the electric batteries used in the six decades since Volta had invented the first one were one-shot affairs. The chemical reaction that gave rise to the electric current eventually proceeded to a point where it could no longer support current. It then had to be discarded, for the chemical reaction could not be reversed.
Yet some chemical reactions are easily reversible. In 1859 a French physicist, Gaston Planté (1834-1889), took two sheets of lead, with an insulating sheet of rubber between them, rolled the lead sheets into a spiral, and upended it into dilute sulfuric acid. He found that a chemical reaction resulted that would produce an electric current. Furthermore, when the battery was discharged, an electric current could be forced through it in the opposite direction, and the chemical reaction would be reversed, so that the battery could eventually produce an electric current again.
Naturally, we are not getting something for nothing. The second law of thermodynamics would not allow that. The electrical energy required to charge a storage battery is always greater than the amount it can then deliver. It would be a losing proposition, therefore, to charge a discharged storage battery from one that was fully charged. To charge a storage battery, you must get your electricity from a generator that makes use of fuel energy or some other nonelectrical source of energy.
≡The Mössbauer Effect
1958 A.D.
GERMANY
Ordinarily, when an atom emits a gamma ray, it recoils. The wavelength of the gamma ray depends in part on the extent of this recoil. Since this varies somewhat from atom to atom, the gamma rays emitted show a spread of wavelength.
The German physicist Rudolf Ludwig Mössbauer (b. 1929) studied conditions under which atoms that were part of a crystal would emit a gamma ray in such a way that the recoil would be spread over all the atoms making up the crystal.
The recoil is then vanishingly slight, and the gamma ray wavelength shows no spread due to that recoil. As a result, the crystal emits a sharply monochromatic beam of gamma rays, and this, discovered in 1958, is called the Mössbauer effect.
Gamma rays emitted in this way by one crystal will be easily absorbed by another crystal of the same type, but if the wavelength varies even slightly in either direction, absorption will not take place. For this work, Mössbauer received a share of the Nobel Prize for physics in 1961. @
æShuttle Flight
1981 A.D.
CAPE CANAVERAL, FLORIDA
Until 1981, all space vessels had been one-time operations, not reusable. It was clear that space exploration could be made more feasible if it were made less expensive by creating reusable vessels.
For that reason, the space shuttle was designed. Its purpose was to go into orbit and then return to Earth. It was not in itself designed to make spaceflight cheap; it was an expensive vessel. However, it would help engineers work out the techniques for developing a future generation of such vessels that would be cheaper.
The first shuttle flight took place on April 12, 1981, which happened, by coincidence, to be the twentieth anniversary of the first spaceflight, by Soviet cosmonaut Yury Alekseyevich Gagarin (1934-1968). The shuttle left and returned safely. It was the first of over a score of such flights during the next four and a half years to be carried through safely.
╧Uranium Radiations
1896 A.D.
FRANCE
The discovery of X-rays by German physicist Wilhelm Conrad Röntgen (1845-1923) fascinated a French physicist, Antoine-Henri Becquerel (1852-1908), who had been working on fluorescent substances as his father had before him. He wondered if perhaps the radiation given off by fluorescent substances might include X-rays.
A fluorescent substance both he and his father had been interested in was potassium uranyl sulfate. In February 1896 Becquerel wrapped photographic film in black paper and put it in sunlight with a crystal of potassium uranyl sulfate upon it. He reasoned that sunlight would make the crystal fluoresce, and any X- rays it produced would penetrate the black paper (as ordinary light would not) and fog the photographic plate.
Sure enough the plate was fogged and Becquerel decided that fluorescence did produce X-rays. But then came a series of cloudy days and Becquerel could not continue his experiments. He had a fresh plate neatly wrapped in the drawer with a crystal resting upon it, but there was no sunlight to expose it to. Finally, unable to bear doing nothing, he developed the film anyway, just to make sure that nothing happened in the absence of sunlight.
To his amazement, the film was strongly fogged. Whatever radiation was passing through the paper did not depend on either sunlight or fluorescence. For this discovery, Becquerel received a share of the Nobel Prize in physics in 1903 and rightly so, for it had enormous consequences.
úBee Communications
1919 A.D.
GERMANY
Pavlov's conditioned responses could be used to elicit answers from animals about what they sensed.
The Austrian-born German zoologist Karl von Frisch (1886-1982), for instance, conditioned bees to go to certain locations to pick up nectar, making certain that the location was of a certain color. They would then fly to other places of the same color, since they had been conditioned to react to that color as they would to a food source.
Frisch then changed the color to see what would happen to the conditioning.
Thus, if he conditioned the bees to black and then substituted red, they flew to it anyway, indicating that they could not see red -- red was black to them.
However, if they were conditioned to black and that was changed to ultraviolet (which would still look black to human eyes), the bees no longer flew to it.
They could see ultraviolet.
By 1919 Frisch had also interpreted the manner in which the bee communicated its findings to its colleagues of the hive. Having obtained honey from a new source, the returning bee would "dance," moving round and round or side to side. The number of the evolutions and their speed gave the necessary information about the location of the new source. Frisch also showed that bees could orient themselves in flight by the direction of light polarization in the sky.
For this work, Frisch was awarded a share of the Nobel Prize for physiology and medicine in 1973.
fPsychological Conditioning
1914 A.D.
U.S.A.
Freudian psychology had grown extremely popular by this time, but those who favored other views were not wanting. In 1914 the American psychologist John Broadus Watson (1878-1958) developed the thesis that human behavior was explainable in terms of conditioned responses, such as those Pavlov had demonstrated. Watson relegated even heredity to a minor role.
Animals, including the human being, he viewed as intensely complicated machines, which reacted according to their nerve-path wiring, those nerve paths being altered, or conditioned, by experience. This view of Watson's was called behaviorism.
⌐The Telephone
1876 A.D.
BOSTON, MASSACHUSETTS
The telegraph, now over 30 years old, transmitted only signals. The British-born American inventor Alexander Graham Bell (1847-1922) wanted something better than that. He wanted to send actual speech over the wires, by turning sound waves into a fluctuating electric current that waxed and waned as the sound waves compressed and decompressed air. The electric current could then be reconverted into sound at the other end.
He finally invented a device capable of doing that and first made use of it accidentally. He had spilled battery acid on his pants and automatically cried out to his assistant, "Watson, please come here. I want you." Thomas Augustus Watson (1854-1934), at the other end of the circuit on another floor, heard the instrument speak and ran downstairs.
On March 7, 1876, Bell patented the telephone. Edison improved it almost at once by devising a mouthpiece that contained carbon powder. When the carbon powder was compressed, it carried more current than when not compressed. As the sound waves compressed and decompressed the carbon powder, the electric current waxed and waned.
The telephone utterly revolutionized human communication.
Benzene Rings
1865 A.D.
GERMANY
Friedrich Kekule's way of writing chemical formulas did not solve all problems. There was one compound, benzene, which was extremely important, being involved in the molecular structure of the new artificial dyes, for instance, that did not yield to his system.
The molecule of benzene is made up of six carbon atoms and six hydrogen atoms. Given a chain of six carbon atoms, there seemed to be no way of adding six hydrogen atoms without producing a very unstable compound -- and benzene was quite stable.
It was Kekule himself who found the answer in 1865. According to his own story, he was in a semidoze in a horse-drawn bus and was visualizing carbon chains when suddenly the tail end of one chain attached itself to the head end and formed a spinning ring. At once he saw that if he imagined the six carbon atoms forming a hexagonal ring, with one hydrogen atom attached to each carbon, a stable atom might be the result. Once the notion of carbon rings was added to that of carbon chains, many structural problems were solved.
∙The Bering Strait
1728 A.D.
BERING STRAIT
As Peter I's reign drew toward its close, the Russian occupation of Siberia was complete. The question remained, though, of whether there was a land connection between Siberia and North America. Peter commissioned a Danish navigator, Vitus Jonassen Bering (1681-1741), to look into it.
In 1725 Bering crossed Siberia overland and reached Kamchatka, which he was the first to map. From Kamchatka, he sailed north in 1728 and reached the ice of the Arctic Ocean without sighting land. He had sailed through what is now known as the Bering Strait, which separates Siberia from Alaska. The sea to the south is the Bering Sea.
Finally, two and a quarter centuries after Columbus, it was shown definitely that North America was not part of Asia.
dBerkelium and Californium
1949 A.D.
BERKELEY, CALIFORNIA
For five years after being synthesized by Seaborg and his group, curium (atomic number 96) had remained the most complex atom known.
In 1949 the more complex elements 97 and 98 were produced. Since this was done at the University of California in Berkeley, California, element 97 was named berkelium and 98 was named californium.
ú Beryllium
1798 A.D.
FRANCE
In 1798 Vauquelin, who had discovered chromium, recognized the existence of a new element in the gems beryl and emerald. He named the element beryllium.
öMaking Tungsten Wires
1909 A.D.
U.S.A.
When Edison introduced the electric light bulb, he used carbon fibers as filaments. These were brittle, hard to handle, and didn't last long. Obviously some sort of metal wire would be better. However, it would have to be of a metal with a high melting point so that it could withstand white-hot temperatures, and such metals were for the most part expensive, hard to draw into wires, or both.
The metal with the highest melting point is tungsten, which melts at about 3410° C. It is not inordinately expensive, but it is brittle. In 1909, however, the American physicist William David Coolidge (1873-1975) managed to perfect a method of drawing tungsten into fine wires.
As a result, tungsten filaments became universal in light bulbs, radio tubes, and other devices. Light bulbs lasted for considerably longer before having to be replaced, therefore, though further improvements remained to be made.
âBlack Hole Evaporation
1970 A.D.
ENGLAND
Black holes, it seemed, could only gain matter, never lose matter.
If so, they were destined to grow indefinitely and would, in the end, consume all the matter of the Universe.
In 1970, however, the British physicist Stephen William Hawking (b. 1942) reasoned from quantum mechanical considerations that black holes might have a temperature. Therefore, if surrounded by an environment with a lower temperature, black holes would evaporate. Massive black holes with the mass of a star or of many stars would evaporate so slowly that they would endure for many, many times the present age of the Universe. As their mass decreased, however, their rate of evaporation would increase.
The view was developed, then, that the final status of the Universe would not be a collection of black holes but a thin expanding melange of leptons and photons originating from evaporated black holes.
7Bifocal Lenses
1784 A.D.
PHILADELPHIA, PENNSYLVANIA
Also in 1784, Franklin, who in his old age needed two sets of spectacles, one for distant vision and one for reading, grew tired of changing them frequently.
He devised bifocal spectacles, the lenses of which were suited for distant vision above and near vision (reading) below.
ÅBinary Stars
1781 A.D.
ENGLAND
Astronomers were still trying to detect the parallax of the stars, the task that Bradley had failed at a half-century earlier.
It struck Herschel that he might be able to detect parallax if he studied stars that were very close together in appearance. Both would be in the same line of sight, but if one was considerably brighter than the other, it might be considerably closer. In that case, the brighter star should show slight parallactic changes of position in the course of the year relative to the dim star.
Herschel began the study of such stars in 1781, and as time went on, he did notice that one of the stars changed position relative to the other in a number of cases. In no case, however, was this change quite what one would expect if it had resulted from the motion of the Earth. In time, astronomers were forced to the conclusion that some double stars were actually close to each other in reality and not merely in appearance and that they moved about each other.
Herschel had discovered binary stars, from a Latin word referring to objects that exist in pairs.
Newton had presented his law of universal gravitation, assuming that it was a force of attraction between any two objects in the Universe, but it had actually been tested only on objects within the Solar System. Now for the first time it could be tested on distant stars, where it was eventually proved to be truly universal.
±Biological Evolution
1749 A.D.
FRANCE
Until now, natural historians who had been busily engaged in classifying life forms had refrained, out of religious conviction or out of prudence, from drawing the conclusion that biological evolution had taken place.
The first important scientist to speculate openly on evolution was the French naturalist Georges-Louis Leclerc de Buffon (1707-1788). In 1749, he began publishing volumes of his book Natural History, which was eventually to consist of 44 volumes.
Buffon treated evolution as a matter of degeneration. It is, after all, a common observation that many things deteriorate with time. Why should not evolution exemplify this? Buffon maintained that apes were degenerated humans, donkeys degenerated horses, jackals degenerated wolves, and so on.
This view is quite wrong, but it implied that species did change with time, which was crucially important. It also sufficed to get Buffon into a certain amount of trouble, which he managed to smooth over with diplomatic recantations.
#The Vitamin Biotin
1942 A.D.
U.S.A.
At this time a new vitamin could only be detected by noting that certain food or food extracts could correct symptoms that known vitamins would not touch. One such new vitamin was called vitamin H. The American biochemist Vincent du Vigneaud (1901-1978) isolated tiny quantities of vitamin H in reasonably pure form, as judged by its powerful effect on the symptoms it could alleviate, and by 1942 had worked out its rather complicated two-ring structure. The compound was now called biotin. It was synthesized and its structure proven.
Quarantine to Reduce Disease
1403 A.D.
VENICE, ITALY
Despite the fact that nothing was known about how disease came to be (except for theories of punishment by God or infestation by demons), people did tend to avoid those who were sick with some particularly fatal or loathsome disease.
Thus, leprosy (undoubtedly along with less drastic skin diseases) was treated as something that required isolation. Lepers were driven out of society. When the Black Death struck, people instinctively fled from those affected (sometimes leaving the dying to die and the dead to remain unburied).
In 1403 the city of Venice, always rationally ruled, decided that recurrences of the Black Death could best be averted by not allowing strangers to enter the city until a certain waiting period had passed. If by then they had not developed the disease and died, they could be considered not to have it and would be allowed to enter.
The waiting time was eventually standardized at 40 days (perhaps because 40-day periods play an important role in the Bible). For that reason, the waiting period was called quarantine, from the French word for "forty."
In a society that knew no other way of fighting disease, quarantine was better than nothing. It was the first measure of public hygiene deliberately taken to fight disease.
·Black Holes
1916 A.D.
GERMANY
After Einstein's equations for general relativity were published, the first to work out solutions for them was a German astronomer, Karl Schwarzschild (1873-1916). He also calculated the gravitational phenomena in the neighborhood of a star with all its mass concentrated to a point.
In order for an object to move infinitely far from a body as the result of a single initial impulse, that initial impulse must produce a speed that will carry the object away so rapidly that its speed will not decline as quickly as does the gravitational pull (which declines with the square of the increasing distance). In that case, the gravitational pull will never be intense enough to bring the object to a complete halt. This escape velocity equals 7 miles per second for Earth but only 1.5 miles per second for the Moon.
In general, the escape velocity from an object's surface increases with the mass of the attracting object and also with its density. Over a century earlier, Laplace had pointed out that if an object was sufficiently massive and dense, even light wouldn't have sufficient velocity to escape.
Schwarzschild studied the case of a star with a mass compressed more and more strongly till the star's volume sank to zero, so that the gravitational pull at its surface got higher and higher without limit. Schwarzschild calculated the distance from such a point-mass at which light would barely have the speed to escape. This is the Schwarzschild radius. Once anything approached closer to the star than the Schwarzschild radius, it could never escape again. Not even light could.
Since nothing could escape, not even light, such a star would behave like a bottomless hole in space, so to speak. It would be a black hole, a name given to it half a century later.
₧Blood Color
1669 A.D.
ENGLAND
It was clear that blood went to the lungs to pick up air, and it was suspected that this must involve a chemical change in the blood. The first to notice evidence to that effect was an English physician, Richard Lower (1631-1691). In 1669 he noted that dark blood drawn from veins turned bright red on contact with air. The necessary details concerning the change had to wait another century, however.
δBlood Types
1900 A.D.
AUSTRIA
Although the usual 18th-century practice was to remove blood from a sick patient, there were occasional physicians who tried to add blood to patients, taking it from the veins of healthy humans or even from animals. Sometimes it was helpful, but sometimes it hastened death, so that most European nations by the end of the 19th century had prohibited such blood transfusion.
In 1900, however, an Austrian physician, Karl Landsteiner (1868-1943), was able to demonstrate some specific properties of human blood. Plasma (the liquid portion of blood) from one donor might clump red cells from person A but not from person B. Serum from another donor might clump red cells from person B but not from person A. Still other samples of plasma might clump both -- or neither.
Clumped red cells could block blood vessels and lead to death. Therefore, it was necessary in performing a blood transfusion to know that the blood of the donor would not clump the red cells of the receiver. Landsteiner showed that human blood fell into four classes: O, A, B, and AB. It was always safest if both donor and receiver were in the same class. In an emergency, O blood could be given to any receiver, but A blood could be given only to A and AB receivers, B blood only to B and AB receivers, and AB blood only to AB receivers.
Landsteiner made blood transfusion rational and safe and added an important weapon to the medical armory. For this discovery, he received the Nobel Prize in medicine and physiology in 1930.
╣ Quantized Atom
1913 A.D.
DENMARK
Now that British physicist Ernest Rutherford (1871-1937) had formulated the nuclear atom, it was possible to view the hydrogen atom as consisting of a nucleus (bearing a charge of +1) and a single electron (with a charge of -1) circling it.
One could argue that the electron, as it circled the nucleus, in effect oscillated from side to side. This oscillation, according to Maxwell's equations, should result in electromagnetic radiation. But if this were so, the electron would lose energy as it circled and would spiral into the nucleus.
The Danish physicist Niels Henrik David Bohr (1885-1962) tried to solve this problem by applying quantum theory to the atom. The electron, he decided, could not radiate energy except in intact quanta, each of which represented a large amount of energy on the atomic scale. Consequently the electron, when it radiated, would lose a large packet of energy and would not spiral into the nucleus gradually but drop very suddenly to a lower orbit nearer the nucleus. It would do this each time it radiated a quantum of energy. Eventually it would reach the lowest orbital state, below which it couldn't fall, and it would then emit no more energy.
In reverse, if the atom absorbed energy, the electron would suddenly rise to a higher orbit, and this would continue with further absorption of energy until it left the atom altogether, at which time the atom would be ionized, becoming a fragment with a positive charge equal in size to the number of electrons that had been boiled off, so to speak. As electrons rose to higher orbits and fell to lower orbits, they would radiate only certain wavelengths, and under other conditions, absorb those same wavelengths, as German physicist Gustav Robert Kirchhoff (1824-1887) had shown over half a century before.
The presence of many electrons rising and falling in orbits might confuse the issue, but hydrogen, with its single electron, should be easier to handle. Indeed, hydrogen has a simple spectrum, giving off radiation at a series of wavelengths that can be related to each other by a rather simple equation. This equation had been worked out by a Swiss physicist, Johann Jakob Balmer (1825-1898), in 1885. It had not seemed to have much significance at the time, but now Bohr could choose orbits for a hydrogen electron that would yield just those wavelengths that the hydrogen spectrum displayed.
Bohr's suggestion wasn't perfect. There were fine details of the hydrogen spectrum that it couldn't account for. There was also no explanation of why the electron, when it was in a particular orbit and oscillating back and forth, did not lose energy. If it couldn't give off an entire quantum, why didn't it stop oscillating?
Bohr's suggestion, however, was the first application of quantum theory to the atom and was enormously important for that reason. The imperfections were gradually removed in succeeding years, and for his work, Bohr was awarded the Nobel Prize for physics in 1922.
uThe First Botanist
320 B.C.
GREECE
The Greek scholar Theophrastus (ca. 372-ca. 287 B.C.) was a student of Aristotle (384-322 B.C.) and headed the Lyceum after the latter's retirement. He was interested in the plant world and wrote a book about 320 B.C. that included descriptions of 550 plant species. It was the first systematic book on botany and included some species from as far away as India.
uBows and Arrows
20,000 B.C.
AFRICA
In some of the early art, there are clear depictions of bows and arrows being used. How old the bow and arrow are is uncertain, but they were in use by 20,000 B.C. at least.
The bow and arrow is an important device because it is the first one invented by human beings in which energy is slowly stored and then released all at once. It made possible attack from a greater distance than with a thrown spear and so was the first truly long-distance weapon. The value of attacking an infuriated animal much larger than yourself from as great a distance as possible is clear.
Bows and arrows were eventually used by humans against other humans (as has been true of any object capable of inflicting damage, no matter what the purpose for which it might originally have been designed). The bow remained a prime weapon in warfare right down to the beginning of the 15th century.
╝Boyle's Law
1662 A.D.
OXFORD, ENGLAND
As Irish-born chemist Robert Boyle (1627-1691) experimented with vacuums, it was he who employed English physicist Robert Hooke (1635-1701) to build an improved air pump.
The air pump got Boyle interested in gases, and in 1662 he discovered that air could be compressed. He did this by trapping some air in the short closed end of a J-shaped 17-foot-long glass tube into which he poured mercury to close off the bottom curve.
If he next added more mercury to the open end, the weight of the additional mercury squeezed the trapped air in the closed end more closely together, and its volume decreased. Indeed, Boyle found that the volume of the gas varied inversely with the pressure upon it. That is, if he doubled the weight of mercury upon it, the volume shrank to one-half the original; if he tripled the weight of mercury, the volume shrank to one-third, and so on. This is called Boyle's Law.
The most important conclusion of this experiment was that air, and presumably other gases, were atomic in nature and that the atoms were widely spread apart. With pressure, the atoms were forced more closely together and the volume shrank.
Liquids and solids could not be compressed with the same ease that gases could be, but that did not necessarily mean they weren't composed of atoms. In their cases, the atoms might already be in contact.
The idea of atomism had not entirely died out since the time of Democritus (ca. 460-ca. 370 B.C.). There had always been a few from time to time who accepted atoms. Boyle's experiments, however, were the strongest evidence yet, and Boyle himself became a convinced atomist. It was to be a century and a half, however, before atomism won out entirely.
+Brain Shape
1810 A.D.
VIENNA, AUSTRIA
In 1810 a German physician, Franz Joseph Gall (1758-1828), published the first volume of a four-volume treatise on the nervous system. In it he stated that the gray matter on the surface of the brain and in the interior of the spinal cord was the active and essential part, and that the white matter, deeper in the brain and on the surface of the spinal cord, was connecting material. In this he was correct.
Gall believed that the shape of the brain had something to do with mental capacity and that different parts of the brain were involved with different parts of the human body. There was something to this, too, but Gall went much too far. He believed he could correlate the shape of the brain with all sorts of emotional and temperamental qualities and that the shape of the brain could, in turn, be deduced from the superficial unevennesses of the skull. This marks the beginning of the pseudoscience of phrenology (from Greek words meaning "study of the mind") in which character is supposedly analyzed by feeling the bumps on the head.
Nerves and the Brain
280 B.C.
ALEXANDRIA
The Museum at Alexandria was the site of important early work on anatomy by Herophilus (ca. 355-ca. 280 B.C.) and his successor, Erasistratus (fl. 250 B.C.). Both were particularly interested in the brain and the nerves. About 280 B.C., Herophilus divided nerves into sensory (those that received sense impressions) and motor (those that stimulated motion). He described the liver and spleen as well, described and named the retina of the eye, and named the first section of the small intestine the duodenum. He noticed that the arteries pulsed, and thought that they carried blood, not air.
Erasistratus distinguished between the cerebrum (the main section of the brain) and the cerebellum (the smaller section behind it). He was struck by the fact that the convolutions of the human brain were more numerous than those in other animals and suggested that this was related to superior human intelligence. Unlike Herophilus, he did not think the arteries carried blood.
This promising beginning came to a sudden end. The Egyptian population believed it was necessary to keep the body intact if a decent status in the afterlife was to be achieved, and public opinion forced an end to all dissection at the Museum. The study of the human body ceased for over 15 centuries as a result.
Recording Brain Waves
1929 A.D.
GERMANY
Dutch physiologist Willem Einthoven (1860-1927) had developed methods for detecting the rise and fall of electric potentials involved in the heartbeat and devised the electrocardiogram in 1903.
The German psychiatrist Hans Berger (1873-1941) thought the same might be done for the brain. During the 1920s he devised a system of electrodes that, when applied to the skull and connected to an oscillograph, would give a recording of the rhythmic shifting of electric potentials commonly called brain waves.
In 1929 he published his results, describing alpha waves and beta waves. In this way, electroencephalography (Greek for "the writing of brain electricity") was developed. It offered a technique for the diagnosis of such serious brain disorders as tumors and epilepsy.
CFermentation to Improve Food
1800 B.C.
CAIRO, EGYPT
Fruit juices that are left standing will sometimes ferment; that is, undergo changes that alter the taste. The same is true of moistened grain. Human beings, driven by thirst or hunger, might consume such fermented materials and then find that they liked the taste and the aftereffects. They were, of course, consuming alcohol, formed from sugars and starches by yeast, and they would grow elated as a result, because they were somewhat intoxicated. (This is not an exclusively human trait. Birds and animals will sometimes greedily feed on fermented fruits and become obviously intoxicated too.)
This may have happened in prehistoric times, but by 1800 B.C. the use of fermented materials was so common that laws had to be passed directing what was to be done in the case of misdeeds committed under the influence of too much beer.
From the beginning of agriculture, grain was converted into flour, which was moistened and made into flat, hard, but nourishing bread. Every once in a while, though, the moistened dough fermented and released gases (carbon dioxide) that caused the bread to rise and grow spongy. The result was leavened bread (from a Latin word meaning "to rise"), which was just as nutritious as flat bread but softer and much more pleasant to eat.
The Egyptians discovered this not long after 1800 B.C. and eventually learned that the process could be controlled. If some of the fermenting bread was saved before it was baked and added to dough that had not yet begun to ferment, the fresh dough would ferment in its turn. One would not have to depend on chance.
mBroca's Convolution
1861 A.D.
FRANCE
Gall had been of the opinion that different parts of the brain controlled different parts and functions of the body. Gall's conclusions were strictly speculative, however. The first person to present conclusive evidence of a specific region of the brain in charge of a specific function was Broca.
Broca had a 51-year-old patient who had lost the ability to speak.
When the patient died in 1861, a postmortem revealed damage to the third convolution on the left frontal lobe of the cerebrum (now known as Broca's convolution). Gall's insight, which had been misdirected into phrenology, was thus put right.
gBromine
1826 A.D.
FRANCE
Courtois had discovered iodine in seaweed 15 years before. The French chemist Antoine-Jérôme Balard (1802-1876), also working with seaweed, found that at times he obtained a brown substance in solution in the liquid he was using to dissolve the ashes of the seaweed. In 1826 he tracked this color to a substance that had properties apparently just midway between those of chlorine and iodine. For a while he thought he had a compound of those two elements, but further investigation convinced him he had a new element, which he called bromine, from the Greek word for "smell," because of its strong odor.
æBronze, The Man-Made Metal
3600 B.C.
GREECE
Copper obtained from some ores is harder than from others. The reason is that copper ore is not necessarily pure; it may be mixed with other substances that, on being heated, combine with copper to form an alloy.
One such mixture consists of copper and arsenic, but arsenic is poisonous, and people who worked with it must have fallen sick. Such mixed ores were therefore abandoned (perhaps the first known case in which worker safety was a factor in technology).
Fortunately, another type of ore mixture was discovered that also resulted in the smelting of a hard form of copper. This was a tin ore, and the hard copper was actually a copper-tin alloy. The alloy was called bronze (possibly from a Persian word for "copper"). Bronze was hard enough to compete with rock. It could hold an edge better and could, of course, be beaten back into shape if necessary, though that was not often required.
Increasingly bronze came to be used for tools and for weapons and armor, too. By 3000 B.C., the Middle East was in the Bronze Age, and this spread outward slowly in all directions as the methods of copper-smelting and bronze formation diffused.
The great cultural product of the Bronze Age was Homer's Iliad, the tale of the Trojan War (fought about 1200 B.C.), in which both Greek and Trojan heroes fought in bronze armor, carried bronze shields, and struck out with bronze swords and bronze-tipped spears.
ABrownian Motion Explained
1905 A.D.
U.S.A.
Brownian motion had remained somewhat of a puzzle since Brown had discovered it. In 1902 the Swedish chemist Theodor Svedberg (1884-1971) had suggested that the unequal bombardment of small particles by molecules from all sides impelled them to move randomly, this way and that.
Einstein, in 1905, analyzed the possibility of molecular bombardment thoroughly. He reasoned that any sizable object immersed in water (or any fluid) is bombarded from all sides, and surely more from one side at one moment and more from another side at another moment. However, the countless trillions of molecules involved means that any small differences will be so small as to be indetectable.
If we consider a smaller and smaller object, the total number of molecules striking it at a given moment will be smaller, and little deviations will loom larger. By the time objects approach the microscopic in size, an additional molecule from this side or that should be sufficient to give it a noticeable push in this direction or that.
Einstein worked out an equation to describe Brownian motion, one from which it was possible to work out the size of molecules and of the atoms making them up, provided one found a way to measure certain other variables that occur in the equation.
It was not long before Einstein's equation was put to good use.
²Brownian Motion
1827 A.D.
GREAT BRITAIN
In 1827 the British botanist Robert Brown (1773-1858) was studying a water suspension of pollen grains under a microscope and noted that the individual grains were moving about irregularly. This had nothing to do with water currents, for the water was still, and besides, while some grains moved in one direction, others would move in the opposite direction, and still others in all directions between.
Brown was at first not surprised. Pollen grains had sparks of life in them, of course, and the motion might be an aspect of life. However, just to check the matter, he then studied a suspension of dye particles, each about the size of a pollen grain, and unquestionably not alive. To his surprise, the dye particles moved precisely as the pollen grains did.
Brown reported the observation, and the phenomenon has been called Brownian motion ever since. It seemed a small thing and had no explanation at the time, but 80 years later it offered scientists the final proof of the existence of atoms.
≥Bubble Chambers
1953 A.D.
DETROIT, MICHIGAN
At this time the most familiar device for detecting the paths of subatomic particles was the cloud chamber invented by Scottish physicist Charles Thomson Rees Wilson (1869-1959). The American physicist Donald Arthur Glaser (b. 1926) thought of reversing its principle.
In the cloud chamber, you have humid air on the point of forming small droplets of liquid. What if you started, instead, with a liquid that was on the point of boiling and forming small bubbles of vapor? In the cloud chamber, a speeding charged particle would encourage the formation of droplets, and a line of droplets would mark out its path. In this new bubble chamber, a speeding charged particle would encourage the formation of bubbles, and a line of bubbles would mark out its path.
Since liquids are denser than gases, a speeding particle will slow more quickly in a bubble chamber than in a cloud chamber, curve more intensely, and reveal its properties more clearly. Then, too, there will be more collisions in the bubble chamber -- more events will take place. Finally, if liquid hydrogen is used as the liquid, it will consist, for the most part, of electrons and single protons, and the simplicity of the background will make the results easier to interpret.
╓Cadmium, Lithium, and Selenium
1817 A.D.
GERMANY
New elements continued to be discovered.
In 1817 a German chemist, Friedrich Strohmeyer (1776-1835), analyzed a bottle in an apothecary's shop that contained zinc carbonate. He found that it turned yellow on strong heating, which it shouldn't have done. It had to contain an impurity, and when he tracked it down, he found it was a new element, which he named cadmium from the Latin name for a zinc ore.
In the same year, a Swedish chemist, Johan August Arfwedson (1792-1841), discovered the element lithium (from the Greek for "stone," because it was found in minerals, whereas sodium and potassium, which were similar, were found in plants, and Berzelius discovered selenium (from the Greek word for "moon").
uCalculating Machines
1693 A.D.
GERMANY
German Gottfried Leibniz (1646-1716) devised a calculating machine in 1693 that went beyond French mathematician Blaise Pascal's (1623-1662). Whereas Pascal's could only add and subtract, Leibniz's could multiply by automatically repeating addition, and divide by automatically repeating subtraction. Leibniz also invented a mechanical aid to the calculation of trigonometric and astronomical tables.
This showed much more clearly than Pascal's device did that arithmetical manipulations followed simple rules and repetitions and by no means required the creative imagination or reasoning power of the human brain.
Pocket Calculators
1971 A.D.
DALLAS, TEXAS
In 1971 Texas Instruments placed on sale the first calculator that was easily portable. Making use of transistorized circuits, it weighed only 2-1/2 pounds and cost merely $150. In subsequent years, both the weight and the cost decreased dramatically.
<Candles as Early Lamps
30,000 B.C.
EGYPT
Oil lamps had been used for thousands of years and would continue to be used for thousands more, but the oil could be spilled, which could spread fire dangerously. If some solid fat was melted and then allowed to solidify again about a wick, the solid would be illuminant and container at once. Such a candle could be carried about without danger of spilling. The earliest candles are shown in Egyptian paintings dating back to about 3000 B.C. and they have been in use ever since, though at the present time they are used more for decoration than illumination.
▌Better Candles
1825 A.D.
FRANCE
Candles had been a source of illumination for nearly five thousand years, but the most common type, tallow candles, which were all that people in ordinary circumstances could afford, had their shortcomings. For one thing, they smelled bad.
The French chemist Michel-Eugène Chevreul (1786-1889) had studied fats and worked out their chemical nature. They were combinations of glycerol with fatty acids. Each glycerol molecule could combine with three fatty acids, and each fatty acid had a long chain of (usually) 16 or 18 carbon atoms.
Chevreul was the first to isolate the most common of these fatty acids: stearic acid, palmitic acid, and oleic acid.
In 1825 he and Gay-Lussac (known for his scientific ballooning work in 1804) patented candles made out of these fatty acids. Such candles were harder than tallow candles, gave a brighter light, looked better, needed less care while burning, and didn't smell as bad. To the society of the time, this was a major advance.
/Canning Food
1795 A.D.
FRANCE
The trouble with food is that much of it doesn't keep. Fairly quickly, it rots, sours, grows moldy. To preserve food for periods of time so that people don't starve over the winter, use must be made of drying, salting, smoking, and so on. A diet that depends on such foods preserves life but is monotonous.
The rising French military leader Napoléon Bonaparte (1769-1821) realized the importance of decent food to an army that had all Europe arrayed against it and offered a prize of 12,000 francs for some way of preserving fresh food for a long period of time.
In 1795 a French inventor, Nicolas-Françcois Appert (1750-1841), began working on the problem. He knew that Spallanzani had shown that meat would not rot if it was boiled for a long enough period and then sealed. Appert therefore worked out a system for applying this principle on a large scale, heating meats and vegetables and sealing them into glass or metal containers.
It took some years to perfect the process, but Appert's system represented the beginning of the canned food industry.
åThe Cannon
1346 A.D.
CRECY, FRANCE
Once the Europeans got their hands on gunpowder, it didn't take them long to place it in a strong metal tube from which its explosive force could hurl out a ball of rock or metal much more forcefully than any catapult could manage. We don't know who first attempted to build these tubes, or cannon (from the Italian word for "tube"). Some claim that primitive cannons were used at a siege of the city of Metz in 1324.
There is no doubt, however, that they were in use by 1346. Edward III of England, intent on claiming the throne of France, went to war in 1337 over the matter, thus beginning what was eventually to be called the Hundred Years War.
The first great land battle of the war was at Crécy in north-central France on August 26, 1346. The French outnumbered the English, particularly in mounted knights. The French also had crossbow archers from Genoa. The English, however, had longbow archers, and it was no contest. The English archers had it all their own way, and the French were massacred. Edward III also had cannon at Crécy. They were primitive things and accomplished nothing -- but they were a portent of the future.
The Cape of Good Hope
1487 A.D.
CAPE OF GOOD HOPE
In February 1487 the Portuguese navigator Bartholomeu Diaz (1450-1500) set forth to search for the southernmost part of the African continent. In a way, he didn't find it, for a storm drove him past it into the open sea.
He turned north again and reached a portion of the African coast that was running eastward. He followed it eastward until it began turning northward. By that time, his rebellious crew forced him to turn back. He retraced his steps, located the southernmost point of the continent, and reported it to King John II of Portugal (1455-1495) as the Cape of Storms, for obvious reasons.
King John II, however, realizing that one more push would now bring his ships to the Far East, renamed it the Cape of Good Hope, the name it bears to this day.
°Capillaries, Tiny Vessels
1660 A.D.
ENGLAND
The discovery of the circulation of blood by English physician William Harvey (1578-1657) had an important flaw. According to Harvey, the blood traveled from the heart through the arteries, into the veins, and back to the heart. But how did the blood get from the arteries to the veins? There was no visible connection, and Harvey was forced to maintain that the connection consisted of blood vessels that were too small to see.
The microscope was now an important tool, however, and a pioneer in this field was the Italian physiologist Marcello Malpighi (1628-1694). The thin wing-membranes of the bat contained what was virtually a two-dimensional network of blood vessels. Malpighi studied it under the microscope in 1660 and saw the tiniest arteries and veins connected by vessels too small to see without the microscope. He called the tiny vessels capillaries, from a Latin word meaning "hair-like." Harvey's theory was complete, but Harvey hadn't lived to see it. He had died three years before.
▐Entering the Heart
1941 A.D.
U.S.A.
Forssmann had introduced the principle of cardiac catheterization (inserting a catheter into a vein and maneuvering it to the heart -- see 1929). In 1941 it was introduced into clinical practice by the French-born American physiologist André Frédéric Cournand (1895-1988) and the American physician Dickinson Woodruff Richards (1895-1973). As a result, Cournand and Richards were awarded the Nobel Prize for physiology and medicine in 1956, sharing it with Forssmann.
8Carriage Springs
1706 A.D.
EUROPE
All conveyances, from sedan chairs to carriages, were subject to the unevennesses of the road, jolting passengers as every projection or rut was encountered. It was not till 1706 that springs were used in carriages to absorb some of the shock. To be sure, this induced swaying, which has its unpleasantness, too, but is undoubtedly preferable to the lurchings and bangings that existed before springs. The devising of ever-more-efficient springs and, just as important, smoother roads gave land transportation less the feeling of being a devil's playground.
óThe Discovery of Catalysis
1812 A.D.
MOSCOW, RUSSIA
From prehistoric times, human beings have known that some substances can bring about a change without themselves being consumed. In fact the substances may increase in quantity. The best-known example is yeast, which can spread its effect through bread dough, to all intents and purposes indefinitely. But then, yeast was eventually discovered to be alive.
It would be much more surprising if something that was not alive and did not reproduce itself were to be capable of bringing about a change without being consumed.
A Russian chemist of German birth, Gottlieb Sigismund Constantin Kirchhoff (1764-1833), boiled a suspension of starch in water to which a little bit of sulfuric acid had been added. If the starch had been boiled in water without the sulfuric acid, nothing much would have happened.
With the sulfuric acid, the starch was destroyed, and in its place, a substance was produced that was freely soluble in water and that tasted sweet.
It was a form of sugar, and it was named glucose, from the Greek word for "sweet."
Several discoveries were made here. First, glucose was studied for the first time, and (as was eventually discovered) it is one of the key substances of living tissue. Second, it was the first hint that starch was built up of glucose units and could be broken down to glucose again. Third, the sulfuric acid that made the breakdown to glucose possible was not itself consumed in the reaction.
In later years, Berzelius gave the phenomenon of participation- without-being-consumed the name of catalysis (from Greek words meaning "to break down"). Sulfuric acid was an example of a catalyst that brought about the breakdown of starch.
îCatapults
400 B.C.
SYRACUSE, SICILY
The Greeks of this period were good at war. They had developed hoplites (from a Greek word for "heavy shield"), or heavily armed foot soldiers. The hoplites' helmets, breastplates, and leg armor were made of good steel. They carried a shield on one arm (instead of around the neck) and a sword in the other. They also had long spears to thrust with, rather than to hurl. They were trained to fight in close formation as a unit -- it was not the individual champion but the weight of the entire formation that counted. A line of hoplites could wipe out the lightly armed disorderly mob that made up most non-Greek infantry, and it was for that reason that the Greeks managed to defeat the enormous Persian Empire.
The most important Greek city in the West was Syracuse, on the eastern coast of Sicily, which reached its period of greatest power under Dionysius (reigned 405-367 B.C.). He encouraged work on new weapons, and about 400 B.C. his workers devised the catapult (from Greek words meaning "to hurl down"). In its first form it was like a giant bow that was immobile and took many men to cock. When it was released, however, it hurled down upon a city's walls, not a little arrow but a huge rock -- or hurled it over the wall and into the city.
It was the first long-range weapon that could hurl heavy objects, or the first piece of artillery (from a French word relating to a bow, which was the first long-range weapon).
The one big disadvantage of the catapult was its slowness. The enemy could see the cocking going on and had plenty of time to prepare for the blow or avoid it. Nevertheless it was a premonitory example of things to come.
*Cattle Fever
1893 A.D.
TEXAS
In 1893 the American pathologist Theobald Smith (1859-1934) reported that Texas cattle fever was caused by a protozoan parasite, as had been found to be true of malaria 13 years before.
Smith went on to show that the parasite was spread from infected animals to healthy ones by blood-sucking ticks. This was the first definite indication that disease could be spread by an arthropod. Ticks were among the arachnids (the spider family), but it would soon be shown that blood-sucking insects could also be responsible for the spread of disease.
¢The Cell
1665 A.D.
LONDON, ENGLAND
The use of the microscope was spreading rapidly and one of the best of the early microscopists was English physicist Robert Hooke. In 1665 he published Micrographia, which outlined his work in this field. It had some of the most beautiful drawings of microscopic observations ever made.
His most important discovery (though it did not seem so at the time, no doubt) involved the structure of cork. Under the microscope, he found a thin sliver of cork to be composed of a finely serried pattern of tiny rectangular holes. These he called cells, from a Latin word for "small chamber" -- especially one of the type that exists in rows, as monastery cells or prison cells do.
The cells that Hooke observed were empty only because they were found in dead tissue. In living tissue they are filled with fluid, and that disqualifies them from being called cells, strictly speaking. The name, however, clung.
╫Law of Octaves
1863 A.D.
ENGLAND
By this time, over 60 elements were known, and they seemed to represent an unruly jungle of characteristics. Chemists were uneasy with that, so they tried to group elements into families. Several attempts had already been made, but an English chemist, John Alexander Reina Newlands (1837-1898), tried something a bit different.
He listed the elements in order of atomic weight and found that the second seven repeated the properties of the first seven quite closely. He tried to extend this further, referring to it as the law of octaves (as in music, where the same seven notes are repeated over and over, with every eighth note resembling the first octave higher, octave coming from the Latin word for "eight").
Newlands's work was not taken seriously, because the list of elements fit the law of octaves very imperfectly. Nevertheless, it helped put the listing of elements in vogue, and in the course of the following decade a much superior table was established.
èCelluloid
1869 A.D.
U.S.A.
Something is plastic if it is capable of being molded or shaped with relative ease. In that sense, clay, plaster, wood, rubber, and glass are all plastic. However, the noun plastic these days has come to be applied to a group of synthetic organic substances that possess plastic properties. The first of these was pyroxylin, prepared by Parkes 17 years earlier.
Pyroxylin had no commercial use at the time. Then a prize of ten thousand dollars (a fortune in those days) was offered for a substance cheaper than ivory but just as good, for the manufacture of billiard balls.
An American inventor, John Wesley Hyatt (1837-1920), wanted the prize money and had heard of pyroxylin. Hyatt improved on Parkes's method of preparing it and in 1869 patented his method of manufacturing billiard balls out of this material, which he named celluloid.
He did not win the prize, but celluloid enjoyed a minor boom as a material for baby rattles, shirt collars, photographic film, and other products. It was light, flexible, waterproof, and easily cleaned. Its one great flaw was that it was flammable. Celluloid was the first commercially successful plastic.
QCellulose
1834 A.D.
FRANCE
Having discovered diastase the year before, Payen went on to study the chemical composition of wood. From wood he obtained a substance that certainly wasn't starch but that could be broken down to glucose units as starch could. Because he obtained it from cell walls, he named it cellulose.
Sugars like glucose, and substances that can be broken down into sugars, are made up of carbon, hydrogen, and oxygen atoms, with the hydrogen and oxygen atoms in the ratio of 2 to 1, as in water. The notion arose, therefore, that these molecules consisted of carbon atoms to which water molecules had been added. For that reason they came to be called carbohydrates (watered carbon). The true structure of carbohydrates, it eventually turned out, was much more complex than that.
Until Payen's discovery, carbohydrates had been given ordinary names such as cane sugar, grape sugar, starch, and so on. Now use of the -ose suffix, as in cellulose, spread until it was used for carbohydrates generally. Cane sugar became sucrose, grape sugar glucose, starch amylose, and so on -- at least, to chemists.
Celsius Scale
1742 A.D.
SWEDEN
For nearly 30 years, the Fahrenheit scale had been commonly used for temperature measurements. It had some disadvantages, however.
For instance, the freezing point of water was set at 32 degrees, a curiously uneven number.
It makes a huge difference, both to scientists and to human beings generally, whether water is liquid or solid, whether a pond is frozen over or not, whether it snows or rains. In 1742, therefore, the Swedish astronomer Anders Celsius (1701-1744) suggested that the freezing point of water be set at 0 degrees, so that a positive reading meant water and a negative reading meant ice. The boiling point of water would then be set at 100 degrees, rather than 212.
This new scale was at first called the Centigrade scale (from Latin words meaning "a hundred steps" -- that is, from the freezing point to the boiling point of water), but this was converted to Celsius scale by international agreement in 1948. The entire world has now adopted the Celsius scale with only one significant exception -- the United States.
[Cell Theory
1838 A.D.
GERMANY
Hooke had first seen the empty remains of cells in cork. Since then, biologists had often seen cells in living tissue, seen them as small bodies marked off and enclosed by cell membranes in animals, and by thin, cellulose-containing cell walls in plants. Brown had even seen the nuclei within cells.
In 1838 the German botanist Matthias Jakob Schleiden (1804-1881) made the necessary leap of understanding and announced that all living plant tissue was made up of cells. The next year, Schwann extended the notion to animals as well. Both Schleiden and Schwann felt that the cell nuclei were of importance in connection with cell reproduction but could not divine the details. Those details were not to be worked out for another 40 years.
The Schleiden-Schwann cell theory helped scientists enormously in enlarging their understanding of life.
δ
Center of the Galaxy
1918 A.D.
PASADENA, CALIFORNIA
The concept of the galaxy had entered the astronomical mainstream with Herschel. Since then, astronomers had assumed the Sun to be near the center of the galaxy since the Milky Way encircled us more or less evenly, in a great arc around the sky.
There was one important asymmetry, however. Globular clusters were not evenly spread over the skies. (Globular clusters are closely packed spherically shaped groups of up to 100,000 stars. They were first noted by Herschel.) These globular clusters were to be found almost entirely in one hemisphere of the sky, something first pointed out by Herschel's son, John Frederick William Herschel (1792-1871). Indeed, about one-third of the globular clusters were to be found in the single constellation of Sagittarius, in which the Milky Way is rather brighter and richer in stars than it is anywhere else.
Once the Cepheid yardstick had been worked out by Leavitt and Hertzsprung, it became possible to find Cepheids in the globular clusters and determine their distances and the distances of the clusters themselves.
This task was undertaken by the American astronomer Harlow Shapley (1885-1972), making use of the new 100-inch telescope. By 1918 he was able to make a three-dimensional model of the globular clusters and could see that they themselves formed a loose sphere around a point in Sagittarius far distant from the Solar System.
Shapley assumed (correctly, as it turned out) that the globular clusters were distributed around the center of the galaxy. His estimate of the distance to that center was a trifle overlarge, something that was later corrected. We now know that the center of the galaxy is 30,000 light-years away and that the galaxy is about 100,000 light-years across. Our Solar System, far from being at the center of the galaxy, is about 20,000 light-years from one end and 80,000 from the other. Shapley had dethroned the Sun from its position at the center of the Universe, as Copernicus had dethroned the Earth.
We cannot see the center of the galaxy (let alone the far half of the structure), because dark clouds of dust and gas in the Milky Way obscure the view. We are, indeed, at the center of what we can see -- which is not surprising.
With Shapley, astronomers finally got a more or less correct picture of the size of the galaxy and of our own position in its outskirts. It was far larger than anyone had thought -- it contained at least 100 billion stars and perhaps twice that number. It is not surprising, then, that astronomers thought our galaxy and its two attendant and much smaller satellite galaxies, the Magellanic Clouds, made up the Universe.
This seemed large enough, but as it happened, astronomers had not yet even begun to grasp the true size of the Universe.
îCepheids in Andromeda
1923 A.D.
PASADENA, CALIFORNIA
Three years earlier, Curtis had debated Shapley over whether the Andromeda nebula was a distant galaxy.
The still-new 100-inch telescope offered a way of settling the matter. The American astronomer Edwin Powell Hubble (1889-1953) used it in 1923 to study the Andromeda nebula and managed to make out some ordinary stars (not novas) in it. Some of these stars were Cepheids, which meant that Hubble could determine the distance of the nebula using the technique worked out by Leavitt.
Hubble's calculations showed that the Andromeda nebula was 750,000 light- years away, although eventually this turned out to be a substantial underestimate. Even so, the distance was great enough to indicate that the Andromeda nebula was not part of our galaxy but existed far beyond it and must be an independent galaxy. From that time on, it was termed the Andromeda Galaxy, and it came to be understood that the Universe consisted of numerous galaxies, as many as a 100 billion perhaps.
For the first time, the general structure of the Universe came to be understood, and it was realized that its size was far, far greater than had been thought.
₧Ceres
1801 A.D.
GERMANY
The German astronomer Johann Daniel Tietz, in Latin Titius (1729-1796), had suggested in 1766 that it was possible to work up a simple arithmetical series that would give the relationship of the distance of the various planets from the Sun. Six years later, the German astronomer Johann Elert Bode (1747-1826) popularized that series, which came to be known as Bode's law.
Bode's law didn't seem to have much scientific significance. Still, when Uranus was discovered, it turned out to be just where Bode's law predicted a planet would be. That rather impressed astronomers. It so happened that Bode's law also predicted that a planet ought to exist in the space between Mars and Jupiter, but no such planet was known. It might be that it was a small one and had gone unnoticed.
For that reason, another German astronomer, Heinrich Wilhelm Matthaus Olbers (1758-1840), began to organize a group that would take different portions of the sky and search them for any moving object that might be that planet.
While the preparations were under way, an Italian astronomer, Giuseppe Piazzi (1746-1826), who wasn't looking for the planet, came across it while he was working at an observatory in Sicily. It was a dim object, not quite visible to the unaided eye, that changed position from night to night. The discovery was made on January 1, 1801, the first day of the 19th century.
Piazzi began to follow its course. Since it moved more rapidly than Jupiter and more slowly than Mars, its orbit must lie between the orbits of those two long-known planets. Since it was much dimmer than either of those planets, it must be far smaller, too, and we now know that it is about 640 miles in diameter, smaller by far than even Mercury, till then the smallest known planet.
That was why it had not been noted earlier.
Nevertheless, it fit Bode's law, and Piazzi named it Ceres, after the Roman goddess most closely associated with Sicily.
éCerium, Osmium, and Iridium
1803 A.D.
SWEDEN
New elements were being discovered rapidly. In 1803 the Swedish chemist Jons Jakob Berzelius (1779-1848) and his friend the Swedish mineralogist Wilhelm Hisinger (1766-1852) discovered cerium, which they named after the newly discovered asteroid Ceres.
The British chemist Smithson Tennant (1761-1815), who had worked with Wollaston and was therefore interested in platinum like elements, discovered two of them in 1803. One he named osmium, from the Greek word for "smell," because of the stench of one of its compounds, and the other iridium, from the Greek word for "rainbow," because of the different colors of its compounds.
⌡Characteristic X Rays
1906 A.D.
ENGLAND
X rays had been discovered 11 years earlier and were still of profound interest to physicists. The British physicist Charles Glover Barkla (1877-1944) studied the manner in which X rays were scattered by gases and found that the higher the molecular weight of the gas, the greater the scattering of the X rays. From this he deduced, in 1904, that the more massive the atoms and molecules, the more charged particles they contained, since it was the charged particles that did the scattering. This was the first indication of a connection between the number of charged particles in an atom and its position in the periodic table.
He further showed, from the manner of scattering, that X rays were transverse waves like light, not longitudinal waves like sound. This was the final proof that they were examples of electromagnetic radiation.
In 1906 Barkla went on to something still more important. He showed that when X rays were scattered by particular elements, they produced a beam with a particular degree of penetration. The higher the atomic weight of an element, the more penetrating the characteristic X rays they produced. He went on to describe two types of such X rays: the more penetrating he called K radiation and the less penetrating he called L radiation.
At the time it was difficult to know what to make of this, but before long, characteristic X rays were to be important in rationalizing the periodic table.
For his work on X rays, Barkla was awarded the Nobel Prize in physics in 1917.
÷Charon
1978 A.D.
CAMBRIDGE, MASSACHUSETTS
On June 22, 1978, the American astronomer James W. Christy, examining photographs of Pluto, noted a distinct lump on one side. He checked other photographs and found that the lump shifted position. Finally he decided it was a satellite located some 12,500 miles from Pluto. (At Pluto's distance, this is not much of a separation as seen from Earth, which accounts for the long- delayed discovery.) Christy named the satellite Charon, after the ferryman who took shades across the River Styx to Hades in Greek mythology.
Charon circles Pluto in 6.39 days, which is just the time it takes for Pluto to turn on its axis. The two bodies, Pluto and Charon, have slowed each other's rotational speed through tidal action until each perpetually presents one side to the other. They now revolve about a common center of gravity like two unequal parts of a dumbbell held together by a gravitational pull. (This is the only dumbbell-situation in the Universe that we have been able to observe so far.) From the distance of separation and the time of revolution, it is possible to work out the total mass of the two bodies, which comes to about one-eighth the mass of the moon. Pluto is about 1,850 miles in diameter (far smaller than anyone had thought), and Charon is about 750 miles in diameter. Charon has 10 percent the mass of Pluto, so that the two are the nearest thing to a double planet we know. (The Earth-Moon is second in this respect, but the Moon has only 2 percent the mass of the Earth.)
XChemical Elements
1661 A.D.
OXFORD, ENGLAND
It had been just about 2,000 years now since Aristotle listed the four elements (earth, water, air, and fire) that made up the Earth and a fifth (aether) that made up the heavenly bodies. That still remained the dominant theory, although some alchemists had considered mercury, sulfur, and salt to be particularly important.
But the day of alchemy was over. The Irish-born physicist and chemist Robert Boyle (1627-1691) published a book in 1661 that was called The Skeptical Chymist, and as a result, the very name alchemist was changed to chemist. The dropping of the prefix al-, which is the Arabic "the," seemed somehow to symbolize turning the back on medievalism. In this book, Boyle also divorced chemistry from medicine and made it a separate science.
Boyle's most important feat was to push chemistry in the direction of becoming an experimental science. He wanted chemical elements to be established by experimentation rather than by deduction.
He pointed out that an element was one of the simple components of the Earth, one that could not be converted into anything simpler. Therefore, anything that couldn't be converted into anything simpler was an element, while anything that could be so converted was not. The only way you could differentiate an element from a nonelement, then, was to try hard to make a substance simpler.
╧Chemical Fertilizer
1842 A.D.
ENGLAND
Plants make use of minerals in the soil, and intensive cultivation deprives the soil of those minerals from year to year. If no minerals are returned to the soil, it will eventually lose fertility. The time-honored way of guarding against this is to make use of animal wastes as fertilizer, so that one of the important functions of domestic animals was to supply material for the manure pile, which would then have to be spread over the fields.
The manure piles, however, were not only offensively redolent, but could also be a source of disease (as was eventually discovered).
It occurred to chemists that it would be possible to determine just what elements were withdrawn from the soil and to return them in the form of odor- free, disease-free chemicals.
In 1842 an English agricultural scientist, John Bennet Lawes (1814-1900), patented a method for manufacturing what he called superphosphate and the next year set up a factory for its production.
This was the first chemical fertilizer. Such fertilizers helped sweeten the atmosphere, reduce the disease rate, and increase the food supply. (Nowadays, there is a fashion for "organically grown" food. Hiding behind that "organically" is the manure pile.)
JChemical Thermodynamics
1876 A.D.
U.S.A.
Thermodynamics, although worked out originally through the study of heat, applies to all forms of energy. An American physicist, Josiah Willard Gibbs (1839-1903), applied it to chemical change.
He wrote a series of papers on the subject that totaled four hundred pages and appeared, over a two-year period beginning in 1876, in The Transactions of the Connecticut Academy of Sciences. In the course of his papers, he evolved the modern concepts of free energy and chemical potential as the driving force behind chemical reactions.
In the papers, he also considered equilibria (singular, equilibrium: the point at which a system comes to rest and there is no further change) between different phases (liquid, solid, or gas), where one or more components of a system are involved. The number of ways (degrees of freedom) in which temperature, pressure, or concentration can be varied in such cases can be expressed by a simple equation, which Gibbs called the phase rule. By the time he was through, Gibbs had left little more to do in what is now called chemical thermodynamics.
∩Chemotherapy
1907 A.D.
GERMANY
The medieval alchemists had attempted to cure disease by the use of various chemicals. They were not truly successful (except occasionally by accident), because they did not know the cause of disease and had no way of testing particular chemicals in a rational manner before using them. Their techniques were largely abandoned, therefore.
The German bacteriologist Paul Ehrlich (1854-1915) returned to the notion of chemical cures (he coined the word chemotherapy in this connection) on a much more knowledgeable basis. It was understood, thanks to the work of Flemming, that synthetic dyes could combine with some parts of cells and not others and could more markedly affect some cells than others.
It occurred to Ehrlich that if a dye could be found that combined with some pathogenic organism but not with human cells, it would be a "magic bullet" that could kill the pathogen while leaving the human patient largely unaffected.
By 1907 he had located a dye called Trypan red that combined with and killed trypanosomes, a type of protozoa that caused sleeping sickness.
Trypan red was therefore a possible cure for the disease.
This development of chemotherapy earned Ehrlich a share of the Nobel Prize in physiology and medicine in 1908.
ÜCherenkov Radiation
1934 A.D.
RUSSIA
Light travels at a speed of 299,792.5 kilometers per second (186,282 miles per second), and nothing can go faster than that according to special relativity. However, light travels more slowly when passing through matter, and the decrease in speed is more marked as the index of refraction of the transparent medium increases. In water, light travels at 224,900 kilometers per second, and only 124,000 kilometers per second in diamond. The speed of light is even a bit below maximum when it is passing through air.
A rapidly moving particle can never travel faster than the speed of light in a vacuum, but it can travel faster than light does in water, let us say. And if the particle is moving extremely close to the speed of light in a vacuum, it may move faster in air than light does. When particles move faster than light in some medium other than a vacuum, they leave a wake of light trailing behind.
A Soviet physicist, Pavel Alekseyevich Cherenkov (b. 1904), was the first to observe this wake of radiation, which came to be called Cherenkov radiation as a result. The reason for the wake was explained by the Russian physicists Igor Yevgenyevich Tamm (1895-1971) and Ilya Mikhaylovich Frank (b. 1908).
From the angle at which Cherenkov radiation is emitted, the speed of ultrafast particles can be calculated, and for this finding, Cherenkov, Tamm, and Frank were awarded the Nobel Prize for physics in 1958.
Child Development
1929 A.D.
GENEVA, SWITZERLAND
By 1929 the Swiss psychologist Jean Piaget (1896-1980) had worked out his observations on child development. By observing and asking questions, he learned much. He also developed what he called conservation tasks: he made changes in simple objects and studied whether children could tell what had not changed. For instance, if one pours water from a broad low vessel into a tall thin vessel, the height of the liquid increases. This may be taken to imply that there is more water, but after a certain stage of development the child recognizes that the quantity of water has not changed.
Piaget described four phases of mental growth, paralleling the physical growth taking place, and maintained that all children went through the same phases in the same order.
9Painless Childbirth
1847 A.D.
ENGLAND
A British obstetrician, James Young Simpson (1811-1870), heard of the American experience with anesthesia and adopted it at once. Disliking ether, however, he made use of chloroform (much more dangerous, actually).
Beginning in 1847, he was the first to administer anesthesia to women in childbirth.
Chloroplast Isolation
1954 A.D.
U.S.A.
Since Pelletier and Caventou had isolated chlorophyll, it had been well known that chlorophyll was essential to photosynthesis. However, no one had been able to make chlorophyll perform the task in the test-tube.
It had been nearly a century since von Sachs had discovered that chlorophyll was present in discrete organelles, called chloroplasts, within the plant cell. It was natural to assume that in the cell, chlorophyll worked as a catalyst, not by itself but as part of an intricate system that was present intact in the chloroplast.
This could be shown if chloroplasts could be isolated intact from the cells, and made to show that they could then carry out photosynthesis in the test-tube.
But chloroplasts are so flimsy that for a long time no procedure sufficed to extract them intact.
Finally in 1954 the Polish-American biochemist Daniel Israel Arnon (b. 1910) was able to obtain intact chloroplasts from disrupted spinach-leaf cells and demonstrate their ability to carry on photosynthesis outside the cell.
äChloramphenicol
1947 A.D.
WORLD
During World War II, penicillin and streptomycin had been isolated and the age of antibiotics had begun. In 1947 chloramphenicol was isolated from the same group of molds that had yielded streptomycin.
Chloramphenicol attacked many different microorganisms and was the first broad-spectrum antibiotic to be isolated. It was fairly toxic, however, and had to be used carefully.
hChlorophyll and Cells
1837 A.D.
FRANCE
When chlorophyll had been isolated, its widespread existence in plants made it seem inevitable that it had some important function.
In 1837 the French chemist Rene-Joachim-Henri Dutrochet (1776-1847) was able to show definitely that photosynthesis took place only in those plant cells that contained chlorophyll. The key importance of chlorophyll to all multicellular life, animals as well as plants, was thus definitely established.
Dutrochet was a convinced antivitalist, by the way. He believed that all aspects of nature, animate and inanimate, were subject to the same physical and chemical laws.
╘Chlorine is an Element
1810 A.D.
ENGLAND
Davy had worked with hydrochloric acid (a strong acid) and showed that it contained no oxygen. This was the final blow to the assumption that oxygen was essential to acids. However, hydrochloric acid did contain chlorine, and Scheele had thought chlorine to be an oxygen-containing compound. In 1810 Davy showed this was not so, and that chlorine was an element. For this reason he rather than Scheele usually receives credit for the discovery of chlorine.
cChlorine
1774 A.D.
SWEDEN
In a classic case of scientific misfortune, the Swedish chemist Carl Wilhelm Scheele (1742-1786) had discovered oxygen at least two years before Priestley did, and by the same method. However, Scheele's discovery was not published (through the negligence of a publisher) until after Priestley's discovery had been reported, so Priestley gets the credit.
Scheele, however, discovered many simple compounds from plants and animals, to say nothing of such poisonous gases as hydrogen fluoride, hydrogen sulfide, and hydrogen cyanide. He was also involved in the discovery of a number of elements, though he never managed to get undisputed credit for a single one of them.
Thus, by 1774 he had done most of the spadework that led to the discovery of the element manganese. His friend, the Swedish mineralogist Johan Gottlieb Gahn (1745-1818), however, took the final step and gets credit for the discovery.
Also in 1774, Scheele isolated the gas chlorine, which was unusual in not being colorless. Chlorine is greenish-yellow in color, and its name, in fact, is derived from the Greek word for "green." The trouble was that Scheele did not recognize chlorine to be an element but thought it was a combination of some substance with oxygen. Chlorine was found to be an element about 30 years later, and it was to that finder that credit for the discovery was awarded.
~ Chlorophyll Synthesis
1960 A.D.
U.S.A.
In 1960 Woodward, who specialized in synthesizing complex organic molecules, succeeded in synthesizing chlorophyll.
≤Chlorophyll
1817 A.D.
FRANCE
Since Joseph Priestley had first shown that plants could restore the vitality of air, chemists had searched for the substance that gave plants this property.
Two who were particularly keen on research into plant chemistry were the French chemists Pierre-Joseph Pelletier (1788-1842) and Joseph-Bienaimé Caventou (1795-1877). Together they isolated a number of alkaloids such as brucine, cinchonine, quinine, and strychnine.
In 1817 they isolated a green compound from plants (indeed, the compound that made them green) and called it chlorophyll, from Greek words meaning "green leaf." As was eventually discovered, it was this compound that trapped the energy of sunlight and converted carbon dioxide and water into plant tissue and oxygen.
φCholera: The Deadly Disease
1854 A.D.
ENGLAND
In the early 19th century, Europe suffered from several cholera epidemics that arrived from India, where it was endemic. Increasingly, physicians were sure that the contagion arose from polluted water. An English physician, John Snow (1813-1858), had published his views on this matter in 1849.
When an epidemic of cholera struck London in 1854, Snow studied the geographic incidence of cholera in relation to water supply. He found 500 cases of cholera, for instance, within a few blocks of a public water pump that drew water from a well just a few feet from a sewer pipe. He had the pump handle removed, and the incidence of cholera fell at once.
This gave a powerful impetus to improving hygiene as a means of disease prevention.
Chromatography
1906 A.D.
RUSSIA
The Russian botanist Mikhail Semenovich Tsvett (1872-1919) worked with plant pigments, which are made up of a large number of rather similar organic compounds, difficult to separate into individual substances that can be studied singly. (This is a difficulty that frequently arises in biochemistry.)
In 1906 Tsvett found a convenient means of separation. He let a solution of a mixture of the pigments trickle down a tube of powdered aluminum oxide. The different substances in the pigment mixture held onto the surface of the powder particles but with different degrees of strength. As the mixture was washed downward, the substances began to separate, those holding with less strength being washed down farther.
If the tube of aluminum oxide was long enough, the substances in the mixture would be completely separated by the bottom of the column, and they would be washed out individually. The separation could be judged by the appearance of different shades of color on the column, so the technique was called chromatography, from Greek words meaning "writing in color." The name was retained even in the case of mixtures of colorless substances. Chromatography, modified in many ways, became one of the most important techniques for the study of complex mixtures.
┼Chromosome Maps
1911 A.D.
NEW YORK, NEW YORK
American geneticist Thomas Hunt Morgan (1866-1945) had shown that chromosomes could cross over from one gene to another, which allowed them to be inherited separately where previously they had been linked, or inherited together. Obviously, the farther two genes were from each other on a particular chromosome, the greater the chance that a crossover somewhere along the chromosome would separate them.
Morgan and his assistant, the American geneticist Alfred Henry Sturtevant (1891-1970), investigated the frequency of separation by crossover in an attempt to locate the genes governing particular characteristics on a chromosome. The first such chromosome map was presented in 1911.
£Chromosomes
1888 A.D.
GERMANY
Flemming's book describing chromatin and the changes it underwent during cell division had appeared six years before.
In 1888 the German anatomist Heinrich Wilhelm Gottfried von Waldeyer-Hartz (1836-1921) suggested that the stubby threads of chromatin that appeared during cell division be called chromosomes. This has become one of those scientific terms that is well known to the public at large.
╪Chromosomes and Inheritance
1902 A.D.
AUSTRIA
Mendel, in working out the laws of genetics, had suggested that for every characteristic there was a pair of factors. Mother and father each contributed one of that pair to the offspring, who in this way inherited characteristics from each parent.
By the time Mendel's work had been rediscovered by De Vries and others, the role of chromosomes in cell division had been worked out by Flemming and their role in the formation of sex cells had been researched by Beneden.
In 1902, then, an American geneticist, Walter Stanborough Sutton (1877-1916), made a suggestion that in hindsight seems obvious. He pointed out that chromosomes were (or contained) the genetic factors Mendel spoke of. He proved to be correct.
;Ship's Chronometer
1728 A.D.
ENGLAND
If a ship wants to locate itself on the ocean, it can measure its latitude (the distance north or south of the equator) by taking the position of the Sun at maximum height or the position of the North Star and calculating the distance of either from the zenith. To measure a ship's longitude (the distance east or west of its home port), however, can be done accurately only if the exact time is known, which presented a problem at this time. A pendulum clock would obviously fail to work on the swaying deck of a ship, and the watches of the time were insufficiently accurate.
In 1714 the British government offered a prize of 20,000 pounds, an incredible fortune in those days, to anyone who would devise a method of determining a ship's longitude. The sum was clearly worth it, to be sure, considering the improvement it would make in a ship's ability to navigate accurately and the profits that would result from accelerated trade.
Beginning in 1728, an English instrument-maker, John Harrison (1693-1776), built a series of five clocks, each one better than the one before. Each clock was so mounted that it could take the sway of a ship without being adversely affected. He designed a pendulum of different metals so that it would stay the same length and give the same beat even as temperature changed.
He also inserted a mechanism that would keep the clock going while it was being wound. Any one of Harrison's clocks met the demands of the prize conditions. In fact, they were more accurate at sea than any other clock then known was on land. One of Harrison's chronometers was off by less than a minute after five months at sea.
The British parliament, however, put on an extraordinary display of miserliness in this connection. It put off the payment to Harrison for years, and he did not get the full amount until 1773.
òChemical Symbols
1813 A.D.
SWEDEN
Once the notion of atoms was advanced, the question arose of how to represent them. Simplicity recommended the use of letters, and in 1813 Swedish chemist Jöns Jakob Berzelius (1779-1848) advanced a system that was eventually adopted. Initial letters were used: H for a hydrogen atom, C for a carbon atom, O for an oxygen atom, and so on. If more than one element had the same initial, a second letter from the body of the name was used, so that Ca was calcium, Cl was chlorine, and Cr was chromium. In the case of ancient elements that had different names in different languages, the Latin name was used in the symbol, so that gold was Au (aurum), silver was Ag (argentum), and so on.
Compounds were symbolized, if simple enough, by simply listing the atoms.
Since water molecules are made up of two hydrogen atoms and one oxygen atom, water is H2O. Ammonia is NH3. Sulfuric acid is H2SO42. And so on.
The Citric Acid Cycle
1937 A.D.
ENGLAND
Many biochemists had contributed insights concerning the metabolism of carbohydrate, including Harden, Meyerhof, and Warburg.
Szent-Györgyi, Hexuronic Acid) had found that any of four different four-carbon acids, if added to tissue slices, stimulated oxygen uptake. He suspected that they must play some role in carbohydrate metabolism.
Beginning in 1937, the German-born British biochemist Hans Adolf Krebs (1900-1981) found two six-carbon acids, including the familiar citric acid, that also played a role. He worked out the details of a cycle that began and ended with citric acid. Sugar molecules entered the cycle, and carbon dioxide molecules emerged at the other end, along with several pairs of hydrogen atoms that, through another chain of reactions including cytochromes, were united with oxygen to yield the energy used by the body.
This citric acid cycle is often called the Krebs cycle in honor of its discoverer, and for this work, Krebs was awarded a share of the Nobel Prize for physiology and medicine in 1953.
DCloud-Seeding
1946 A.D.
U.S.A.
The American physicist Vincent Joseph Schaefer (b. 1906) had been working with Langmuir on the phenomenon of icing, particularly in reference to airplanes flying at high altitudes, which could develop layers of ice on their wings that could cause them to crash.
To study the production of ice crystals, Schaefer and Langmuir used a refrigerated box kept well below the freezing point of water. They hoped that in the box, water vapor would condense around dust particles to form ice crystals.
It was important, however, to find just the proper types of dust particles to use as seeds for ice formation, and the experiments therefore continued for some time.
In July 1946, during a heat wave, Schaefer dropped some solid carbon dioxide into the box to cool it more effectively. Promptly, ice crystals formed and a miniature snowstorm whirled inside the box. Solid carbon dioxide might therefore help in cloud-seeding.
On November 13, 1946, Schaefer was flown by airplane over a cloud layer in western Massachusetts and dumped 6 pounds of pellets of frozen carbon dioxide. A snowstorm started.
In mild weather, such an artificial snowstorm started at high altitudes would, of course, turn to rain as it fell. Nevertheless, rain-making never became important. In the first place, it worked only if the proper kinds of clouds were present -- in other words, if it was likely to rain in any case.
In the second place, rain that might be helpful to some people would invariably be harmful to others, so that to make rain artificially would be to ask for an infinite amount of litigation.
├Clinical Thermometer
1866 A.D.
ENGLAND
Doctors had long recognized the importance of knowing a patient's temperature, but the thermometers they were forced to use were long, clumsy, and required up to 20 minutes to register results. A British physician, Thomas Clifford Allbutt (1836-1925), devised a small thermometer, no more than 6 inches long, which took only 5 minutes to produce results. With this clinical thermometer, taking a patient's temperature became truly routine.
▌Mechanical Clocks
1335 A.D.
MILAN, ITALY
The first advance over the water clock came in the fourteenth century. Instead of being driven by a rise in water level, the dial on the clock face was driven by the downward pull of gravity on weights. The resulting mechanical clocks did not tell time more accurately than water clocks did, but they were more convenient and required less care. They could be mounted in a tower (either of the city hall or of the town church) for all to see. One was erected in Milan, Italy, in 1335, for instance. It struck the hour, and for the first time citizens could learn the time (to the nearest hour, at any rate) by listening to the number of times the bell rang. (The very word clock is from the French word for "bell.")
║Clones
1967 A.D.
GREAT BRITAIN
It is possible to produce a complete plant from a portion of one in a way that does not involve sexual reproduction. A plant twig, for instance, can be grafted to the branch of another tree, even when the other tree is of another species.
The twig may well grow and flourish there, and such a twig is called a clone, from the Greek word for "twig."
Simple animals, not too specialized, can regenerate an entire organism from a relative scrap. Sponges, fresh-water hydras, flatworms, and starfish are all noted for this. The new organisms may also be called clones, by analogy.
Among vertebrates, cloning does not occur spontaneously. Suppose, though, that the nucleus of a living skin cell of one individual is placed into an ovum of another individual, the ovum's own nucleus having been removed. The chromosomes of the skin cell may then replicate and produce new cells with the genetic equipment of the introduced skin cell. The ovum may thus produce an organism, not of its own original species but of the species from which the skin cell was taken. This, too, would be a clone.
The technique of replacing one cell nucleus with another is tricky. It had first been successfully carried through 15 years earlier by the American biologists Robert William Briggs (b. 1911) and Thomas J. King.
In 1967 the British biologist John B. Gurden applied this technique of a nuclear transplantation to transferring a cell from the intestine of a South African clawed frog to an egg cell of another individual of the same species. From that ovum, with its alien nucleus, a normal new individual developed -- a clone of the one from which the nucleus was taken. This was the first clone produced of a vertebrate.
Amphibian ova are naked and unprotected, however. The ova of reptiles and birds are protected by shells, and the ova of mammals remain within the body.
These require much more complicated techniques, and such cloning has not yet been achieved.
ïCloud Chamber
1911 A.D.
SCOTLAND
Since the discovery of radioactivity by Becquerel, the use of speeding subatomic particles had been increasing. This made it important to have devices that could yield information concerning them. The Geiger counter could detect their presence, but more was needed.
A Scottish physicist, Charles Thomson Rees Wilson (1869-1959), had been studying clouds and labored to produce small artificial clouds in the laboratory that he could also study.
In 1896 he had allowed moist air to expand within a container so that the expansion lowered the temperature and not all the moisture could be retained, the excess coming out as water droplets to form a tiny cloud. In this way he determined that the presence of dust or of electrically charged ions encouraged the formation of water droplets and therefore of clouds.
It occurred to Wilson eventually that energetic radiation would produce ions as they spread through the atmosphere. If he could prepare air that was dust- free, he could make it so moist that water drops would only be kept from condensing by lack of the dust that would serve as condensation-seeds.
If an energetic particle then passed through the chamber, and if the chamber was expanded, droplets of water would form around the ions produced by the passage of the particle, and not only would the presence of the particle be detected but its route of travel as well. If the cloud chamber was then placed in a magnetic field, the curvature of the path of the particle would indicate the nature of its electric charge and give information concerning its mass. It would also indicate collisions of particles with molecules and with other particles and offer a guide to events that took place before and after the collision.
Wilson perfected his cloud chamber in 1911 and it quickly became an important adjunct of nuclear research. For this work, Wilson was awarded a Nobel Prize in physics in 1927.
eClusters and Nebulae
1785 A.D.
ENGLAND
William Herschel studied the various fuzzy objects that Messier had listed and found, in 1785, that some of them were not nebulas but clusters of stars, densely packed (at least by the standard of our own uncrowded stellar neighborhood) into a roughly spherical shape. We call them globular clusters now and know that some consist of hundreds of thousands of stars.
There were some nebulas that Herschel couldn't resolve into constituent stars. He wondered, like Immanuel Kant, if they might not be large collections of stars too far off to resolve.
In addition, he discovered dark areas in the Milky Way, small regions that contained no stars but that were surrounded on all sides by countless numbers of them. Herschel thought they were holes, which happened to be pointed in our direction so that we could see through into a cylinder of starlessness.
┤Coal
1228 A.D.
CHINA
The first fuel used for fire, and still a very common one, is wood. Wood grows constantly, so that ideally it should last as long as Earth does in approximately its present form. However, it is possible to use wood faster than it replaces itself and, in fact, this becomes inevitable as population grows and the uses for fire increase.
Coal (from an old word meaning a "burning ember") is actually the remains of very ancient wood. When coal was found, it was burned. When quantities were found partly buried, the ground was sometimes dug into to find additional quantities. There are records of coal having been burned in China about 1000 B.C., in ancient Greece, among pre-Columbian Native Americans, and so on.
For a long time, these were merely opportunistic operations, but surface coal was getting hard to find, and people started digging in earnest -- first in China.
In England, coal-mining became a serious operation in the early 13th century, and by 1228 London was receiving shipments of coal by sea from Newcastle. (Londoners called it sea-coal, for that reason.) Coal continued to be burned as a substitute for wood, all the more so as England was gradually being deforested.
∞Coal Hydrogenation
1912 A.D.
GERMANY
The Haber process for hydrogenating nitrogen to form ammonia set off a flurry of activity. The German chemist Carl Bosch (1874-1940) improved the process and supervised the construction of large plants to make use of it.
In 1912 another German chemist, Friedrich Bergius (1884-1949), applied the principles in treating coal and heavy oil with hydrogen to form gasoline.
For their work on high-pressure processes, Bosch and Bergius shared the Nobel Prize for chemistry in 1931.
╡Cobalt
1737 A.D.
SWEDEN
It puzzled miners that a blue mineral resembling copper ore did not yield copper when smelted. The miners assumed it was copper ore that had been bewitched by kobolds -- earth spirits who were thought to be malevolent at times.
In 1737 a Swedish chemist, Georg Brandt (1694-1768), investigated the blue ore and managed to obtain a metal from it but one that was definitely not copper. Brandt gave it the name of the earth spirit, spelling it cobalt, and that is still the name of the element.
Cobalt was the first new element discovered since Brand's discovery of phosphorus three-quarters of a century earlier. Since phosphorus is not a metal, cobalt was also the first metal to be discovered that was not known to the ancients or to the medieval alchemists.
Brandt was perhaps the first important chemist to be completely free of any alchemical taint, and after him the discovery of new elements continued till contemporary times.
Coenzyme A
1947 A.D.
U.S.A.
The carbohydrates, fats, and proteins of food, in the course of their metabolism, all break down to an acetyl group, also called a two- carbon fragment. This is then built up again to form the substances characteristic of an organism's own tissues.
In 1947 Lipmann was able to isolate a substance that was essential to the transfer of the acetyl group from one compound to another. He called it coenzyme A, where the A stood for acetyl group. The structure of coenzyme A was found to include that of pantothenic acid, one of the B vitamins. Pantothenic acid is essential to life and must be present in our food, because the human body cannot form it within its own tissues, cannot form coenzyme A without it, and cannot run metabolic changes without coenzyme A.
íCoffee
850 A.D.
ETHIOPIA
In many regions of the world, it is necessary to treat water before it is safe to drink. Alcohol will kill germs, so that many people drank beer or wine rather than water. (They didn't know about germs, but beer or wine tasted better anyway.) Others boiled water and added tea leaves to get rid of the flat taste.
The Muslims were not allowed to drink wine and didn't know about tea. Naturally, they would be on the watch for something.
Coffee may have originally grown wild in Ethiopia in the province of Kaffe and been brought to southern Arabia. There, in 850, according to tradition, a goatherd noticed that his goats acted frisky after eating berries of the plant. He tried it himself, liked the sensation, and told others. In time, people learned how to roast the beans obtained from the berries, steep them in boiling water, and produce coffee. Centuries later, coffee was introduced to western Europe.
WCoincidence Counter
1929 A.D.
GERMANY
In 1929 the German physicist Walther Wilhelm Georg Franz Bothe (1891-1957) devised a new method of studying cosmic rays. He placed two Geiger counters one above the other and set up a circuit that would record an event only if both counters recorded it virtually simultaneously.
This would happen only if a cosmic ray particle, streaking down from above, shot vertically through both counters. Particles coming from some other direction would pass through one counter and not the other. And particles that were not cosmic rays, though coming from the right direction, would be insufficiently energetic to pass through both.
Such a coincidence counter turned out to be very useful in measuring the short intervals of time between passage through one counter and the next.
These ultrashort intervals were still long enough for events to take place on the subatomic scale. Bothe used this technique to show that the laws of conservation of energy and of momentum were as valid for atoms as for billiard balls.
For his coincidence counters, Bothe was awarded the Nobel Prize for physics in 1954.
║Coins
640 B.C.
ASIA MINOR
Trading originally consisted of barter: you give me this and I will give you that. If two people both had something they didn't need that the other badly wanted, the trade was easy. Usually, however, both sides wanted to make sure they didn't give up something more valuable for something less valuable. Since comparative values are hard to judge, there must have been many times when both traders felt cheated.
Eventually the custom arose of using metals, especially gold, as a medium of exchange. Gold was beautiful and much to be desired as ornamentation. It didn't rust or corrode, and it was rare, so that a little bit went a long way. Once everything was valued as so many unit weights of gold, a person could buy an object for that amount or exchange it for an object worth that same amount. In all transactions, it was then necessary to have a scale that could be used to weigh little odds and ends of gold, with the usual fears on all sides that the scale, or the weights, might be crooked.
In western Asia Minor, the kingdom of Lydia was founded about 680 B.C. by Gyges, who ruled till about 648 B.C. Under his son, Ardys, who ruled from about 648 to about 613 B.C., the Lydian government issued pieces of gold of standard weight, with the weight marked on them and a portrait of the monarch included as a governmental guarantee. In any transaction, it was now only necessary for a number of coins to be passed over; no weighing was necessary. (Coin is from a word meaning "stamp" because of the weight and portrait figure that are stamped upon it.) The development of coins greatly accelerated trade, and the idea was so transparently good that it was adopted by other governments as well.
äColor and Stellar Luminosity
1905 A.D.
DENMARK
We all know that some stars are brighter than others; astronomers measure that brightness as magnitude. A star can appear bright for either of two reasons. It may radiate a large amount of light (be of high luminosity), or it may be unusually close to us so that it appears bright even though it has low luminosity.
The Danish astronomer Ejnar Hertzsprung (1873-1967) suggested that if a star's distance were known, one could calculate what magnitude it would have if it were some standard distance away. The distance chosen was 10 parsecs, or 32.6 light-years. The brightness of the star at that distance would then be its absolute magnitude. Thus, if our Sun were 10 parsecs away from us, it would seem to have a magnitude of 4.86 (a rather dim star), and that would be its absolute magnitude.
In studying the absolute magnitude of various stars, Hertzsprung could calculate their relative luminosities. In 1905 he noticed that there were two kinds of red stars: red stars with very high luminosity (which we now call red giants) and red stars with very low luminosity (which we now call red dwarfs).
The most interesting aspect of the findings was that there were no red stars of intermediate luminosity. Hertzsprung's report did not attract much attention at first (he published it in a journal of photography), but it represented the first step toward understanding the evolution of stars.
τColor Vision
1959 A.D.
BOSTON, MASSACHUSETTS
For a century it had been thought that three basic colors were sufficient to reproduce the entire color range, and to combine into white light. The three colors were red, green, and blue. These colors are, in fact, used in color television to produce all the other colors. Furthermore, in the retina of the eye there are three types of cells, one to react with each of the three basic colors.
In 1959, however, Land, who had invented Polaroid and the Land camera, advanced a new theory of color vision. He maintained that only two different wavelengths of light are needed, and that they don't even have to be very sharp. One light could be ordinary white light with an average wavelength in the yellow-green. This would serve as the short-wave light. Red light would serve as the long-wave light. Thus, red and white in combination could present the full color range. Land produced a system of color photography based on this theory that reduced the cost of the process.
■Discovering a New World
1492 A.D.
SPANISH COAST
While the Portuguese were working their way around Africa, there were those who felt that the same result could be achieved another way. Since it was understood that the Earth was spherical, it was bound to occur to people that it might be circumnavigated and that the Far East could be reached by sailing west.
The concept was a simple one and, in fact, it had been suggested by Roger Bacon (ca. 1220-1292) two centuries before. What stopped people from making the effort was the thought that between the western coast of Europe and the eastern coast of Asia might be a vast stretch of ocean that the ships of the day could not be expected to manage.
If Eratosthenes (ca. 276-ca. 194 B.C.) was correct and the Earth was 25,000 miles in circumference, then between Europe and Asia were some 12,000 miles of unbroken sea. Yet other authorities, such as Ptolemy (2nd century), had thought the Earth was smaller than that, and Marco Polo (1254-1324) had thought that Asia extended farther east than it really did.
Combining a smaller Earth with a more eastward Asia, an Italian navigator, Christopher Columbus (1451-1506), was convinced that a westward trip from Europe to Asia was a matter of only 3,000 miles. He thought this could be managed, and he shopped about the various nations of western Europe for financial support so that he could outfit an expedition.
Portugal was a natural target, of course, but the Portuguese experts thought the Earth was larger than Columbus's figure (the Portuguese were right) and were convinced it would not be long before they circumnavigated Africa and reached their goal.
Columbus tried elsewhere without luck and was almost on the point of giving up when things turned out well for him in Spain. With Ferdinand and Isabella ruling jointly over a united Spain, the nation could assault the last scrap of Muslim rule. This was the nation of Granada in the far south of Spain. The joint monarchs prosecuted a vigorous war against Granada and on January 2, 1492, it fell. What's more, Torquemada engineered the expulsion of the Jews from Spain in 1492.
The Spanish monarchs, feeling Spain to be united and strong, decided to give Columbus a minimum of financial backing. With three old ships and a crew of prisoners released from jail for the purpose, he set forth on August 3, 1492. For seven weeks he sailed westward, encountering no land but also encountering no storms. Finally on October 12, he sighted land -- an island, as it turned out, in the Bahamas.
He sailed southward and encountered islands of the West Indies. (To his dying day, Columbus was convinced he had reached the Indies; that is, the eastern coast of Asia. The name of the West Indies and the habit of calling Native Americans Indians are the result of that delusion.) It was not Asia, of course, that he had come upon, but the American continents, a New World, and the Old World would never be the same again.
Columbus was not, of course, the first human being to set foot on these continents. Siberian natives had done so at least 30,000 years earlier. He was not even the first European to do so, for Leif Eriksson had done it five centuries before. Columbus's feat, however, led almost at once to the beginning of permanent European settlements on the new continents, and that marked their entry into the common current of world history. It is for this reason that Columbus is generally given credit for the "discovery."
Incidentally, the fact that new continents existed that were wholly unknown to the ancients helped eliminate the notion that the ancient thinkers had known everything and had solved all problems. Europeans gained the heady feeling that they now moved beyond the ancients, and that helped make possible the Scientific Revolution that was to start in half a century.
╬Combustion
1772 A.D.
FRANCE
Chemists' understanding of combustion at this time was based on a theory first propounded in 1700 by a German chemist, George Ernst Stahl (1660-1734). He suggested that objects that were combustible were rich in something he called phlogiston, from a Greek word meaning "to set on fire."
In the process of combustion, fuel lost its phlogiston, and eventually a residue was left that lacked phlogiston and would not burn. Stahl recognized that rusting was comparable to combustion. He believed metals to be rich in phlogiston and held that they gradually lost it as they were converted to rust.
The chief flaw in the theory was that when wood burned it lost much of its weight (presumably because of the loss of phlogiston), yet when iron rusted, it gained weight. In Stahl's time, however, it wasn't considered important to measure quantities exactly and chemists ignored this paradox.
French chemist Antoine Lavoisier, however, believed in weighing. In 1772 he began heating objects in enclosed volumes and weighing that volume. For instance, he burned certain elements in air and found that the material produced was heavier than the elements themselves, though nothing within the container had changed weight at all. If the elements gained weight in burning, then something else must have lost weight, and the only something else this could be was the enclosed air. If some of the air had been absorbed by the burning elements, there should be a partial vacuum in the flask. Lavoisier opened the flask, and sure enough, air rushed in. The added weight of the inrushing air was equal to the weight gained by the element that had been burned.
By such experiments, Lavoisier concluded that combustion did not come about through the loss of phlogiston, but through the combination of the substance that was burning or rusting with some portion of the air. This killed the phlogiston theory, although a few important chemists continued to accept phlogiston for some decades longer.
╒Halley's Comet
1758 A.D.
GERMANY
A little over half a century before, English astronomer Edmond Halley (1656-1742) had predicted that the comet of 1682 would return in 1758. The amateur astronomer Johann Georg Palitzsch (1723-1788) set up his telescope and trained it on the part of the sky where the comet was expected to appear, if it did return. On December 25, 1758, he spotted it, and once the news broke, professional astronomers zeroed their instruments in upon it. The comet has ever since been known as Halley's comet, or in line with the conventions of the present day, Comet Halley.
Calculating backward, Halley's comet turned out to be the one that appeared at the time of the invasion of England by William of Normandy. It was also the comet that Italian artist Giotto di Bondone painted in 1304. The return of Halley's comet suddenly made comets the headliners of astronomy, and for several decades it seemed that the greatest feat any astronomer could achieve was to discover comets.
Comets
1066 A.D.
LONDON, ENGLAND
Comets made periodic appearances in the sky. They were frightening because they came unheralded and followed an unpredictable path. Furthermore, their shapes were irregular, rather like a woman's head with long streaming hair as though in mourning. (Comet is from the Greek word for "hair.")
The unheralded coming made them appear like special warnings from heaven, and the streaming "hair" made it seem certain that the warning was of disaster. Sure enough, disaster always came when a comet blazed in the sky.
(Disaster always came when no comet blazed in the sky, too, but people paid no heed to that.)
In 1066, there was a bright comet in the sky that attracted much attention, especially because of events that were than taking place in Normandy and in England.
óComet's Tails
1538 A.D.
GERMANY
In the 1530s, no fewer than six comets appeared in the sky. Fired by the example of Regiomontanus (1436-1476), astronomers viewed them calmly. One of these was Girolamo Fracastoro, who had coined the word syphilis. In 1538 he published a book in which he recorded his observations and mentioned that a comet's tail always pointed away from the Sun.
A German astronomer, Peter Bennewitz (in Latin Petrus Apianus; 1501-1552), also studying these comets, published a book in 1540 in which he came to the same conclusion independently. He published the first scientific drawing of a comet, in which he indicated the position of the tail with reference to the Sun.
ƒTracking a Comet
1472 A.D.
GERMANY
Comets had always been viewed with such terror that almost no one had been able to observe them rationally. Then in 1472, when a bright comet appeared in the sky, a German astronomer, Johann Müller (1436-1476), refused to allow himself to be governed by fear. (He is better known by his self-chosen name of Regiomontanus, which means King's Mountain, as does the German name of his birthplace, Königsberg.)
Regiomontanus observed the comet from night to night and noted its position against the stars. In this way, for the first time, the exact path of a comet across the sky was plotted. It marked the beginning of rationalism with respect to those bodies.
Communications Satellite
1965 A.D.
U.S.A.
On April 6, 1965, the United States launched Early Bird, the first communications satellite intended primarily for commercial use. It made available 240 voice circuits and one television channel. In this year the Soviet Union also began to send up communications signals.
~Comets' Orbits
1705 A.D.
LONDON, ENGLAND
For a century or more, astronomers had been trying to puzzle out the orbits of comets. It was clear that comets' orbits were nothing at all like those of the planets. Some astronomers thought comets' passed through the Solar System in a straight line. Others thought they passed through in parabolas -- coming in from far-off space, going around the Sun and out forever.
Once Newton's Principia was published, however, it seemed to many that comets had to be bound by gravitation as the planets were.
Halley, in an attempt to prove that this was so, began collecting data on comets. Eventually, when he had listed the movements of two dozen comets, he was struck by the similarity of the path across the sky of the 1682 comet (which he himself had observed) with the paths of the comets that had appeared in 1607, 1531, and 1456. These four had come at intervals of 75 or 76 years. It seemed to Halley that it must be the same comet, returning regularly.
If that were so, a comet would have an orbit that was an ellipse, just as Earth's orbit was, but the cometary ellipse would be extremely elongated. At one end, the comet would approach close to the Sun; at the other, it would recede far beyond Saturn, the farthest known planet.
Halley predicted, in a book written in 1705, that this same comet would return about 1758 and that it would cross the sky in the same path as in 1682.
He was aware, he said, that the gravitational influence of the planets might alter the orbit somewhat and change the time of appearance a little.
Halley's claim was not taken seriously at the time, but it did rouse additional interest in comets.
\Comparative Anatomy
1798 A.D.
FRANCE
The greatest anatomist of his day was a Frenchman, Georges Cuvier (1769-1832). In a book published in 1798, he studied the anatomy of various animals to show how they compared with one another and did so with such excellence that he is considered the founder of comparative anatomy.
He introduced a new broad classification into the taxonomic scheme of Linnaeus. Linnaeus's broadest division was that of class, but Cuvier grouped various classes into phyla (singular phylum, from a Greek word for "tribe").
Cuvier's eye for detail was such that he could tell whether fossil remains represented animals that belonged to one or another of the known phyla even though they were not members of any living species.
Everything he discovered seemed to imply the existence of biological evolution, but Cuvier remained firmly in the antievolution camp.
Early Computers
1930 A.D.
U.S.A.
Babbage had tried to build a machine that would solve complicated mathematical problems by purely mechanical means. He was defeated by the fact that mechanical methods of the day were, by and large, too coarse to do the work.
By the 1920s, engineers had at their disposal electric currents, together with radio tubes to control those currents. These cut down on the number of moving parts needed and supplied a much more delicate way of controlling the parts of what came to be called a computer.
In 1930 the American electrical engineer Vannevar Bush (1890-1974) produced the first machine capable of solving differential equations and the first one that Babbage would have recognized as fulfilling his design. However, Bush's computer was only partly electronic.
╨Binary Numbers
1700 A.D.
HANOVER, GERMANY
Our system of positional notation for numbers is based on 10, undoubtedly because we have 10 fingers on our two hands. There is, however, nothing magic about the figure 10. Instead of units, tens, hundreds (10 x 10s), thousands (10 x 10 x 10s), and so on, we could have units, eights, sixty-fours (8 x 8s), five-hundred-twelves (8 x 8 x 8s), and so on, or ones, seventeens, two-hundred-eighty-nines (17 x 17s), four-thousand-nine- hundred-thirteens (17 x 17 x 17s), and so on -- or any number.
This was pointed out by German mathematician Gottfried Wilhelm Leibniz about 1700. Some bases for positional notation are, of course, more convenient than others. Using the base 12 or 8 each has some advantages over 10. Leibniz also showed that the binary system based on 2 had its uses. Its positions were units, twos, fours, eights, sixteens, and so on. The only symbols it needed were 1 and 0. The binary system is particularly useful for modern computers.
yThe Structure of Comets
1949 A.D.
PASADENA, CALIFORNIA
The approach of a comet to the Sun results in the development of a hazy coma and a tail. The American astronomer Fred Lawrence Whipple (b. 1906) suggested in 1949 that this could be explained by supposing that comets were essentially icy in nature, made up of an admixture of silicate dust and gravel (and in some cases perhaps, a small rocky core). When heated by the Sun's closeness, cometary ice vaporized explosively, and the dust it contained formed the haze and the tail. In short, a comet is a "dirty snowball." This suggestion was readily adopted by most astronomers, and few, if any, doubt it now.
∙Concave Lenses
1451 A.D.
GERMANY
Until now, only convex lenses had been used in eyeglasses. Convex lenses are thicker in the center than at the edges, and they curve the light inward so that on passing through the lens of the eye it reaches a focus sooner than it otherwise would. This is useful for eyes that are too short and are ordinarily far-sighted (usually among the aged).
In 1451, however, the German scholar Nicholas of Cusa (1401-1464) suggested the use of concave lenses, thinner in the center than at the edges, to bend light outward and bring it to a focus later than would otherwise take place. This is useful for eyes that are too deep and that are otherwise near- sighted. This made eyeglasses a boon to young people (who are often near- sighted) as well as old.
2Pavlovian Conditioning
1907 A.D.
RUSSIA
Salivation at the sight of food is an unconditioned response. It is brought about by the construction of the nerve network with which the organism is born. In 1907 Pavlov began an attempt to see if he could impose a new pattern upon such inborn ones.
Thus, a hungry dog that is shown food will salivate. If a bell is made to ring every time the dog is shown food, the dog will eventually salivate when the bell rings even when food is not shown. The dog has associated the sound of the bell with the sight of food and reacts to the first as though it were the second. This is a conditioned response.
Studies of the conditioned response led to the thought that a good part of learning and of the development of behavior is the result of conditioned responses of all sorts picked up in the course of life.
ÄElectrical Conductance
1729 A.D.
ENGLAND
The interest in static electricity produced by Hauksbee's friction machine began to bring about results. An English experimenter, Stephen Gray (1666-1736), found that when he electrified a long glass tube, the corks at the end were also electrified even though they had not been touched. The electricity, whatever it was, had clearly traveled from the glass into the corks. Gray thought, therefore, that electricity was a fluid.
He experimented further, causing the electrical fluid to travel through long stretches of twine (as long as 800 feet). He found that the fluid flowed more easily through some substances than through others. This led to the division of substances into conductors and nonconductors. Nonconductors might also be called insulators, from the Latin word for "island," since a nonconductor could pen up the electric fluid and keep it confined, as the sea confines an island.
h Conservation of Parity
1956 A.D.
CHINA
Physicists had worked out conservation laws that dictated conservation of energy, momentum, angular momentum, and electric charge, among others. In every case, this meant that the total quantity of that property in a closed system (one that did not interact with objects outside the system) could not change, no matter what happened within the system. The assumption was that such conservation laws were universal.
The study of subatomic particles showed that these conservation laws held in the subatomic realm as well. In addition, new conservation laws were discovered, such as the conservation of parity. Parity was the quality of being either odd or even. Just as in numbers, odd parity plus odd parity equaled even parity; even parity plus even parity equaled even parity; but odd parity plus even parity equaled odd parity. Each particle was assigned a particular parity, either odd or even, so that the total of all the particles in a closed system was either odd or even. No matter what happened to the particles within the system, if it began even, it ended even, and if it began odd, it ended odd. At least, so it was assumed.
Then trouble arose with kaons. Sometimes kaons broke down to two pions, which together had even parity; and sometimes to three pions, which together had odd parity. It was concluded that there were two kinds of kaons, one with even parity and one with odd. However, no one could detect any difference between the two kinds of kaons or predict which one a particular kaon would be.
In 1956 two Chinese physicists, Yang Chen Ning (b. 1922) and Lee Tsung-dao (b. 1926), suggested that there was only one kind of kaon, but that since kaons broke down through the weak interaction, and since in the weak interaction parity was not necessarily conserved, then a kaon could break down into either two or three pions indiscriminately. They pointed out that if parity was conserved in the weak interaction, then in certain particle changes, electrons would come out in equal amounts, left and right. If parity was not conserved, then electrons would come out predominantly in one direction. The experiment was performed, and the electrons came out predominantly in one direction.
This meant that although parity seemed to be conserved in the strong interaction and the electromagnetic interaction, it was not conserved in the weak interaction. As a result, Yang and Lee received the Nobel Prize for physics in 1957.
This did not mean, by the way, that conservation of parity really broke down altogether. It might merely mean that parity had to be combined with another property for both to be conserved. For instance, if particles gave off electrons predominantly in one direction, antiparticles gave them off predominantly in the other direction. The combination was called C-P (charge conjugation and parity), so scientists decided there was a law of C-P conservation.
;Conservation of Mass
1789 A.D.
PARIS, FRANCE
Antoine Lavoisier in 1789 wrote the best textbook of chemistry the world had seen up to that time.
The most important generalization he introduced in that book was that in any closed system (one from which no mass was allowed to leave, and into which no mass was allowed to enter), the total amount of mass remained the same no matter what physical or chemical changes went on. This is the law of conservation of mass. For over a century it has been central to chemistry, and when it was finally modified, it was only to make it even more fundamental.
îConservation of Momentum
1668 A.D.
ENGLAND
In studying motion, it became clear that motion wasn't created out of nothing. If some moving object struck another object at rest, it might well impart motion to the second object. (Anyone playing billiards can see this.) Yet a great deal of motion in a light object would impart only a small motion to a heavy object. (Anyone kicking a cannonball can see this.)
Perhaps if one multiplied the mass by the velocity, it would be that product that stayed the same. The product of mass and velocity is called momentum (from a Latin word for "movement"). The English mathematician John Wallis (1616-1703) was the first to suggest, in 1668, that the total momentum of a closed system (one into which no momentum from the outside entered, and from which no momentum leaked into the outside) remained always unchanged. This is called the law of conservation of momentum.
Momentum can be shifted from one part of a system to another but can neither be created nor destroyed. Momentum can be in either of two directions -- let us say, plus or minus. If one starts off with no momentum at all in a closed system, one part may start moving in one direction (the plus direction) if another part starts moving in the opposite (minus) direction. If the two momenta (movements) are equal and opposite, they cancel, and the total momentum remains zero. Similarly, if two bodies come together with equal and opposite momenta (total, zero), they can bounce off each other, having switched the plus and minus to some extent, or they can stick together and both be motionless (the total always remaining zero).
Such a conservation law explains a great many things about motion that would otherwise be puzzling. The law of conservation of momentum was the first of the conservation laws to be understood, but others would, in time, follow, and all are fundamental to our understanding of the structure and functioning of the Universe.
▀Conservation of Energy
1847 A.D.
GERMANY
Mayer had suggested a law of conservation of energy, and Joule had collected the data that made such a law reasonable. Both lacked the necessary credentials as physicists to be convincing.
In 1847, however, the German physicist Hermann Ludwig Ferdinand von Helmholtz (1821-1894), whose credentials were impeccable, gathered the necessary data and published his conclusion that the law of conservation of energy existed. In other words, the total amount of energy in the Universe was constant; none could be created and none could be destroyed. Similarly, in any closed system -- any portion of the Universe from which energy could not leave and into which energy could not enter -- the total amount of energy was constant and could be neither created nor destroyed. (To be sure, no subsection of the Universe can be perfectly isolated from all energy loss or gain.) Naturally, although energy can be neither gained nor lost, it can be converted from one form to another. Electricity, magnetism, chemical energy, kinetic energy, light, sound, and heat can all be interconverted.
The law of conservation of energy is also known as the first law of thermodynamics and it is usually viewed as the most basic of all the laws of nature.
≡Constitution of the Stars
1863 A.D.
ENGLAND
Granted that the elements in the Sun seemed to be the same as those on Earth, might it be argued that the Solar System would naturally be made of one set of materials but that other stars might be made of other elements?
The English astronomer William Huggins (1824-1910) studied the spectra of some of the brighter stars and announced in 1863 that their spectral lines were those of the old familiar elements. Presumably, then, the entire Universe was made up of the same elements.
╥Coolidge Tube
1913 A.D.
U.S.A.
Coolidge, who had pioneered the use of tungsten filaments in electric light bulbs, made a further advance involving that metal in 1913: he used a block of tungsten as an anode in a cathode-ray tube to produce X-rays. This increased the ease and efficiency with which X-rays could be produced. Whereas hitherto X-rays had been almost entirely a laboratory phenomenon, the new Coolidge tube made it possible to use them in industry, medicine, and dentistry.
Copper
4,000 B.C.
CYPRUS
From the early days of Homo habilis to 4000 B.C. or thereabouts, a period of two million years, tools and weapons were made of stone, wood, or bone. Stone is the most durable of these and the most likely to remain as evidence of long-past human activity. As a result, that long period is known as the Stone Age, a term first used by the Roman poet Titus Lucretius Carus (95-55 B.C.) and reintroduced by a Danish archaeologist, Christian Jürgensen Thomsen (1788-1865), in 1834.
The Stone Age is divided into the Paleolithic, the Mesolithic, and the Neolithic (from Latin words meaning "Old Stone," "Middle Stone," and "New Stone," respectively) based on advancing techniques of handling the stone.
Occasionally, though, pebbles that were not like other pebbles must have been found by Stone Age people. For one thing, these occasional odd pebbles were shiny and were heavier than ordinary pebbles of that size. What's more, if these shiny pebbles were struck with a stone hammer, they did not split or shatter as ordinary pebbles did, but they distorted.
These occasional pebbles were metals. Dozens of different metals are known, but most of them remain in combination with nonmetallic substances, and rocky substances are the result. Only those metals that are inert and tend not to combine with other substances are likely to be found in a free state. The three inert metals most likely to be found free are rather rare even for metals. These are copper, silver, and gold. Their rareness is shown by the fact that the very word metal is from a Greek term meaning "to search for."
Metal nuggets exist that were dealt with by human beings as long ago as 5000 B.C. or even earlier. Because of their metallic luster and the fact that they can be beaten into interesting shapes, they were used at first almost exclusively as ornaments. Of these, gold was the most desired, for it was the most beautiful in color (a gleaming yellow), the heaviest, and the most inert. It simply doesn't change with time. Silver, a very light yellow, tends to darken with time, and copper, which is reddish, may even turn green. (Copper is from the word for Cyprus, the island that served as an early source of the metal.)
It was only when human beings discovered that metals could be obtained from special rocks called ores that metals became common enough to use for other purposes. Of these, the first to be discovered was copper. Copper is combined with oxygen, carbon, or both in certain rocky ores, and the discovery that copper could be obtained from them in pure form took place about 4000 B.C.
Undoubtedly it was accidental at first. A fierce wood fire might be built on such copper ore. Under the heat of the fire, the carbon in the wood and in the ore would combine with the oxygen in the ore to form the gas carbon dioxide, which would escape, leaving metallic copper behind. Some observant person might notice the reddish globules among the ashes of the fire, and eventually the circumstances would be understood and the ores searched for and deliberately heated. In this way fire made possible metallurgy -- the obtaining of metals from their ores.
Copper ornaments became more common thereafter, but copper could not be used as a tool, though one might think it could. After all, a sharp-edged piece of rock, if chipped, loses its edge, and this cannot be restored without laborious chipping. If a sharp-edged piece of metal is blunted, it can simply and easily be beaten sharp again. However, copper was too easily blunted. It couldn't very well be beaten after every minor use.
∙Helicopter
1939 A.D.
STRATFORD, CONNECTICUT
One problem with airplanes is that they must move quickly in order to produce aerodynamic lift under their wings. If they slow up, the lift dwindles and they crash. A device that exerted a force straight upward instead of merely forward as propellers do would eliminate this necessity for speed-born lift. The obvious solution was a large propeller directly overhead. Since the ends of the propeller would mark out a helix as the vehicle lifted upward, such a device was called a helicopter, from Greek words meaning "helical wing."
The Russian-born American aeronautical engineer Igor Ivan Sikorsky (1889-1972) had been working with helicopters for 30 years and finally in 1939 produced a satisfactory model. On September 14, a helicopter with Sikorsky himself at the controls flew successfully. The time was to come when it would be a primary weapon in wars fought in Vietnam and Afghanistan, to say nothing of its uses in tracking traffic, rescue work, and intra-urban transportation.
;Cordite Smokeless Powder
1889 A.D.
ENGLAND
For four centuries, gunpowder had ruled the battlefield. It produced a smoke and a stench, however, and battlefields hidden under a thickening pall of gunpowder smoke made adequate generalship difficult.
An English chemist, Frederick Augustus Abel (1827-1902), worked on the problem of developing explosives that would not produce smoke. In 1889, with the help of another British chemist, James Dewar (1842-1923), he developed cordite.
Cordite was a mixture of nitroglycerine and nitrocellulose to which some petroleum jelly was added. The resulting gelatinous mass could be squirted out into cords (hence the name of the material), which after careful drying could be measured out in precise quantities.
The use of cordite (and other such smokeless explosives) freed the battlefield from its cloud. While it might seem small comfort that the scene of carnage and atrocity could be seen clearly, it was important militarily, for it allowed generals to survey a battle's progress and better avoid the casualties that come about when soldiers blunder about uselessly.
[Coriolis Effect
1835 A.D.
FRANCE
The existence of cyclonic storms, pointed out four years earlier by Redfield did not long remain a mystery.
In 1835 a French physicist, Gaspard-Gustave de Coriolis (1792-1843), took up the matter of motion on a spinning surface, both mathematically and experimentally. When the Earth spins, it spins all in a piece, so that a point on the Equator, forced to move a length of 25,000 miles in 24 hours, must move a little over 1,000 miles an hour. As one progresses farther and farther from the Equator, either north or south, a point on the surface makes smaller and smaller circles in the course of the day and moves more and more slowly. At the poles, there is no motion.
If, then, we imagine a quantity of air or water near the Equator, we can see that it must be carried west to east at just over 1,000 miles per hour. If that air or water moves north (or south) away from the Equator, it retains its speed, but the solid ground beneath it moves more slowly. The air or water gains on the ground, therefore, and curves off eastward. Similarly, if air or water moves toward the Equator, it finds the ground moving faster and gaining on it, so in effect, it curves westward.
This curving motion is the Coriolis effect, and it accounts for the fact that air currents and water currents take up circular paths in opposite directions north and south of the Equator.
Earth is so large that under ordinary circumstances, we don't move north or south fast enough for the Coriolis effect to come into significant play. It must be taken into account, however, in the case of artillery fire and satellite launchings.
BCoronary Bypass
1969 A.D.
U.S.A.
The heart receives blood from the coronary arteries, which branch off from the aorta near the point where the aorta leaves the heart. In other words, the very first share of the blood, as it emerges from the heart on its way to the body generally, is fed to the heart itself. There seems justice here, since the heart's labor on behalf of the body is both enormous and essential.
Unfortunately, the coronary arteries have a tendency to accumulate rough plaques on their inner surface, plaques that are rich in cholesterol. (This is particularly true when people eat too much of a cholesterol-rich diet.) These plaques narrow the bore of the arteries and allow less blood to reach the heart.
The roughness also increases the likelihood of clot formation, which may stop the blood flow altogether.
Starving the heart of blood causes the severe pains of angina pectoris, and of course any serious stoppage causes a heart attack and death. A perfectly healthy heart can be immobilized because of such coronary mishaps.
In 1969 a surgical technique was developed of using veins or sometimes arteries from the patient's own body to lead the blood around the clogged portions of the coronaries, renewing the heart's blood supply. If more than one such portion is bypassed, we speak of a double bypass, a triple bypass, and so on.
Since 1969 coronary bypass operations have become extremely common, and while they do not necessarily lengthen life, they make what remains of it much more pain-free and also make it possible to indulge in exertion freely again. This is a great boon to many.
úCoronagraph
1930 A.D.
FRANCE
For two centuries, astronomers had been traveling the world in order to witness rare astronomical events that were not easily visible in other places and at other times. Examples are the far southern stars, total eclipses of the Sun, and transits of Venus and of Mercury.
One of the rare sights, from the point of view of both beauty and scientific interest, was the Sun's pearly upper atmosphere, or corona, in which helium was first discovered.
In 1930 the French astronomer Bernard-Ferdinand Lyot (1897-1952) devised the coronagraph, a telescope that focused the light of the Sun on an opaque disk, cutting out all scattered light from the atmosphere and from the lens itself. Mounting a telescope in the clear air of the Pyrenees, Lyot managed to observe the inner corona, at least, of the uneclipsed Sun. This meant that astronomers no longer had to wait for total eclipses to study the corona and its spectrum.
⌠Cortisone
1935 A.D.
U.S.A.
The first hormone to be isolated was adrenaline. It had been obtained by Takamine, Epinephrine) from the adrenal glands. The adrenals consist of two parts, however, which turned out to be two different glands. The inner part, or medulla (the Latin word for "core"), is what manufactures adrenaline. The outside part, which wraps about the medulla, is the cortex (from a Latin word for "bark"). It too manufactures hormones.
The American biochemist Edward Calvin Kendall (1886-1972) isolated no fewer than 28 different cortical hormones, or corticoids, of which four showed effects on laboratory animals. He named the corticoids by letter, and the four effective ones were Compound A, Compound B, Compound E, and Compound F.
Of these, Compound E, which Kendall isolated in 1935, proved the most useful. It came to be called cortisone and was widely used as an anti- inflammatory drug.
For his work on corticoids, Kendall was awarded a share of the Nobel Prize for medicine and physiology in 1950.
≥Cortisone and Arthritis
1948 A.D.
ROCHESTER, MINNESOTA
The American physician Philip Showalter Hench (1896-1965) was interested in rheumatoid arthritis, a painful and crippling disease. Pregnancy and attacks of jaundice relieved its symptoms, so he conjectured that it was not a germ disease but a disorder of metabolism.
Hench tried various substances, including hormones, in the search for something that would relieve the symptoms. A decade earlier, the adrenocortical hormones had been isolated by Kendall, Cortisone), and it occurred to Hench that these ought to be tried. His role as a colonel in the Army Medical Corps during World War II delayed him, but after the war he began working with the new hormones. He tried Compound E, also called cortisone, which had been isolated in 1946, and in 1948 found that it worked well. For this he received a share, along with Kendall, of the Nobel Prize for medicine and physiology in 1950.
Cortisone proved to be a tricky substance, however, to be used only with great care and judgment.
eCotton Gin
1793 A.D.
UNITED STATES
The new textile industry of Great Britain, and the one that was just beginning to arise in New England, meant increasing demands for cotton, which could be grown with great profusion in the southern states. However, it was difficult to pull the cotton threads off the seeds in the cotton bolls, and that limited the quantity that could be produced.
In April 1793, however, an American inventor, Eli Whitney (1765-1825), challenged to do something about the problem, invented the cotton gin (gin is short for engine). It was a simple device in which metal wires poked through slats and entangled themselves in the cotton fibers. The wires were affixed to a wheel, and as the wheel turned, the cotton fibers were pulled off. One gin could produce 50 pounds of cleaned cotton per day.
The effect on the United States was catastrophic. The southern states began to produce cotton in great quantities, and slaves were needed, also in great quantity, to pull the bolls off the plants so that the gins would have enough to work on.
The southern states, which had been giving up on slavery, had to return to it now, defend it, and work up all sorts of excuses for its existence. They developed an agricultural economy based on slave labor, which kept them poor, while the northern states grew rich on wheat and industry. And in the end, it brought on the Civil War.
Copernicus
1507 A.D.
CRACOW, POLAND
The speculations of Aristarchus (fl. ca. 270 B.C.) in about 280 B.C. about a heliocentric (sun-centered) system in which the Sun was at the center of the Universe, with the planets, including the Earth, revolving about it, had been disregarded, and the geocentric system of Hipparchus (fl. 146-127 B.C.) and Ptolemy (2nd century) had been accepted without question.
However, the mathematics needed to work out the planetary motions on a geocentric basis was very difficult. While the Sun and Moon moved steadily west- to-east against the stars, the other planets occasionally reversed direction (retrograde motion) and grew markedly brighter and dimmer as they progressed across the sky.
The Polish astronomer Nicolaus Copernicus (1473-1543) thought, as early as 1507, that if one went back to Aristarchus's view and supposed that all the planets, including Earth, were moving about the Sun, it would become easy to explain retrograde motion. It would also be easy to explain why Venus and Mercury always remained near the Sun and why planets grew dimmer and brighter. In addition to all this, the mathematics for working out planetary motions and positions would be simplified.
Copernicus did not, in his suggestions, abandon all Greek ideas. He clung to the notion that planets had to move in orbits that were circles and combinations of circles, and in this way he retained much unnecessary complexity.
The difference between Aristarchus and Copernicus was that Aristarchus merely presented his notion as a logical way of looking at the planets. Since others thought it wasn't logical, that ended it. Copernicus, however, used the Aristarchean idea to work out the actual mathematics of the planetary motions and show the reduction in complexity. This meant that even if people denied that the heliocentric system could be true, they would still be apt to use it as a simplified device for calculations.
Nevertheless, Copernicus hesitated to publish his theory and his computations, because he knew that the geocentric theory was approved by the Catholic Church. To advance a heliocentric theory would surely create a storm. He therefore quietly circulated his book only in manuscript form.
Finally he let himself be persuaded by enthusiastic friends to have the book printed. It was entitled De Revolutionibus Orbium Coelestium (Concerning the Revolution of Heavenly Bodies). He dedicated it to Pope Paul III (1468-1549) as a placatory gesture, and then died. The story is that Copernicus was given the very first copy of his book on the day of his death. As Copernicus had forseen, the book created a loud and violent storm. The Catholic Church put the book on its Index, forbidding the faithful to read it, and did not lift the ban till 1835. The Lutherans were equally hostile. The book could not be suppressed, however. With the coming of printing, far too many copies flooded the libraries of the scholars.
Copernicus's book totally overturned Greek astronomy, and though it was 50 years before astronomers generally could bear to turn their backs on Ptolemy and accept the fact that the vast Earth flew through space on an annual journey about the Sun, the book marked the birth of what came to be called the Scientific Revolution. With it came final proof that the ancients did not know it all and that moderns might strike out on their own in new directions and reach new heights -- and they certainly did.
It could be argued that just as printing made the Protestant Reformation possible, it also made the Scientific Revolution possible.
╪CPT Symmetry
1964 A.D.
U.S.A.
After Lee and Yang had shown that parity was not conserved in the weak interaction, parity was combined with a particle characteristic called charge conjugation (which told whether the particle in question was an ordinary particle or an antiparticle) with the idea that if parity was unbalanced in one direction in a particular particle, charge conjugation would be unbalanced in the other, and the two together would be conserved.
This was called CP (charge-parity) conservation. But in 1964 two American physicists, Val Logsden Fitch (b. 1923) and James Watson Cronin (b. 1931), found that CP was not always conserved either. Neutral kaons in their decay, on rare occasions violated CP conservation. In order to keep the symmetry, time (T) had to be added. Where CP was asymmetric in one direction, T was asymmetric in the other, and the combination retained symmetry.
Physicists now speak of CPT symmetry. Cronin and Fitch shared the Nobel Prize for physics in 1980.
lCrab Nebula as a Radio Source
1947 A.D.
AUSTRALIA
It had been 16 years since Jansky first detected radio waves from outer space, but only since World War II had techniques been developed that permitted handling of the microwave radiation used in radar. These techniques could now be applied to astronomy.
In 1947 the Australian astronomer John C. Bolton had a radio telescope that was capable of locating a radio source with sufficient precision to associate it with an object that could be identified optically. Thus he found that the third strongest radio source in the sky was clearly the Crab Nebula, which was the remains of a great supernova explosion.
The Crab Nebula was the first optical object discovered to be a radio source, and this was the first indication that radio astronomy might offer a technique for making discoveries that were not apparent from the simple study of visible light itself.
═The Crab Nebula
1848 A.D.
IRELAND
Lord Rosse, whose giant telescope had detected the spiral nebulas, studied the first nebulosity (M1) on the list Messier had prepared.
It was a curiously irregular patch of fog that marked the spot at which a bright new star had appeared in 1054, although that event had gone unnoticed in Europe.
To Rosse, the foggy patch seemed to have numerous crooked legs like those of a crab and he called it the Crab nebula in consequence, a name it has kept ever since. As time passed, the Crab nebula grew more and more interesting to astronomers until it was stated (with some exaggeration, perhaps) that all of astronomy could be divided into two equal parts: one, the Crab nebula, and two, everything else.
dCardiac Catheter
1929 A.D.
GERMANY
A German surgeon, Werner Theodor Otto Forssmann (1904-1979), was the first to work out a practical system of cardiac catheterization. He inserted a catheter (a long, thin, flexible rod that was opaque to X rays) into a vein in his own elbow and pushed it along the vein until it reached the heart. This made it possible to study the structure and function of an ailing heart and to make accurate diagnoses without the necessity of exploratory surgery.
The technique was not used clinically for over a decade, but Forssmann was awarded a share of the Nobel Prize for physiology and medicine in 1956.
°Age of the Earth
1650 A.D.
ARMAGH, IRELAND
Of the written materials available to Europeans at this time, the Bible was the only one that claimed to give the history of Earth from the creation, and it was generally accepted by all scientists as the authoritative word of God at this time and for two more centuries. (Many people accept it as such to this day.)
The Bible does not use any acceptable chronology for its early history, but by following back from the reign of King Saul and making use of hints here and there in the earlier historical sections, it is possible to decide what the biblical date of the creation might have been.
In 1650 James Ussher (1581-1656), an Anglican bishop, worked out the date of the creation in this way and decided it had taken place in 4004 B.C. Four years later an English theologian, John Lightfoot (1602-1675), sharpened the date and made it 9 A.M., October 26, 4004 B.C.
Such dating of creation has no valid basis whatever, but it has strongly influenced popular opinion to the present day.
[ Cro-Magnon Man
20,000 B.C.
ALTAMIRA, SPAIN
Sometime after 50,000 B.C., a variety of Neanderthal existed with less pronounced eyebrow ridges, even in male adults, with a high forehead and a distinct chin, and with smaller teeth. In short, this was the kind of hominid, quite exactly, that we are. We are Homo sapiens sapiens, and we are sometimes referred to as modern man, though modern human beings is more appropriate terminology to make it clear that men, women, and children are meant and not only men.
Between 50,000 B.C. and 30,000 B.C., the two varieties of Homo sapiens coexisted, but by the latter date, some interbreeding and probably a great deal of slaughter had put an end to the Neanderthals, so that for the last 30,000 years or so, all living hominids have been of the modern type.
Modern human beings were extremely successful. For the first time, they extended the range beyond where Homo erectus had left it. Between 40,000 B.C. and 30,000 B.C., human beings took advantage of the existence of land bridges that the fall in sea level had produced. They entered Australia from southeastern Asia, and North America from northeastern Asia. No hominids had existed in either continent before. They also found their way to the Japanese islands.
The new lands were steadily overrun, and by 10,000 B.C. human beings had reached the southernmost part of South America, and even Tierra del Fuego, the island to the south of that continent. All the continental areas except Antarctica and the glaciated areas in the north were settled.
Human beings were hunters, of course, and they had developed rituals to improve their success. One, apparently, was to draw pictures of animals being successfully hunted, in the conviction, perhaps, that life would imitate art, or that the spirits that animated animals would be mollified in this way and would cooperate.
In 1879, a Spanish archaeologist, Marcellino de Sautuola (d. 1888), was excavating Altamira Cave in northern Spain, when his 12-year-old daughter, who was with him, spied paintings on the ceiling and cried out "Bulls! Bulls!"
There were paintings of bison, deer, and other animals in red and black, drawn perhaps as long ago as 20,000 B.C., similar to those seen here drawn in the caves at Lascaux, France.
The drawings spoke highly of the artists' skill. If anything were needed to show that early human beings were our intellectual equals, this would do. In the last 20 millennia, we have gained enormous knowledge and experience, but we are not one whit more human than those ancient cave artists.
So excellent was the art, in fact, that many people refused to believe it was truly ancient. Many felt it to be a fraud of some sort, a modern hoax. It was only with the finding of other caves and other cave paintings that the art was finally accepted as ancient.
The cave paintings were found in remote places and were invisible except by artificial light, so that it is believed they were drawn for religious and ritualistic purposes rather than for display. Nevertheless, they are clearly the result of infinite pains, and it is hard to believe that the artists did not derive joy from their work.
╔Crossbows
1050 A.D.
FRANCE
The greater the force with which a bow must be bent, the greater the force with which the arrow will be sent forth when the tension is released. The greater the force of the shot, the greater the range and the penetrating power. Naturally, the larger the bow, or the stiffer, the better -- except that eventually human muscle doesn't suffice for pulling back the string of the bow.
In France, sometime about 1050, machinery was brought into play: the bow was drawn back by a two-handed crank or the equivalent. Eventually the bows were made of steel, and a short bolt was shot out that had a range of about 1,000 feet and could penetrate chain mail. This was the first mechanized hand weapon, and the bolt it shot forth seemed so terrifying that the weapon seemed too horrible to use. At least a Church council of 1139 tried to ban its use except against non-Christians. (The ban didn't work.)
The chief disadvantage of the crossbow was its slowness. It took a long time to crank it up and make ready to shoot and once it was fired, the enemy might easily swoop down before it could be cocked again. (Hence the expression "to have shot their bolt," meaning to have taken action and to be helpless thereafter.)
│Cryptanalysis
1589 A.D.
FRANCE
Simple codes are almost as old as writing itself. After all, by substituting or rearranging words or letters according to some prearranged scheme, something that remains plain to the people involved may be made totally obscure to others. In such cases, you have a code or cryptogram.
Codes that can be made can be broken, and as the years went by, the use of ever more subtle methods of encoding messages were countered by ever more subtle methods of decoding them.
An early example of this came in 1589, when France was in the last stages of a civil war. Henry III (1551-1589) had no direct heirs, and his second cousin, Henry of Navarre (1553-1610), was the logical successor. Henry of Navarre was a Huguenot, however, and was bitterly opposed, not only by French Catholics but by Philip II of Spain.
Philip II was using a code that the French mathematician Françcois Viète (1540-1603; in Latin Franciscus Vieta), working for Henry of Navarre, was able to decode in 1589. Philip II, unable to account for the fact that his messages were being read, complained to Pope Sixtus V (1521-1590) that the French were using sorcery and ought to suffer ecclesiastical punishment as a result.
╞Crystal Asymmetry
1846 A.D.
FRANCE
Biot had shown that some substances were capable of twisting the plane of polarized light. He had suggested at the time that some asymmetry in the system brought about the twisting. This seemed more likely to be true when it was found that some samples of a particular substance twisted polarized light clockwise, while other samples of the same substance twisted it counterclockwise.
Starting in 1846, a French chemist, Louis Pasteur (1822-1895), began his search for the possible asymmetries. He worked with small crystals of substances called tartrates. He studied them under the microscope and found that the crystals were rather subtly asymmetric, with one particular little facet on one side but not on the other. What's more, some crystals had the facet on the left side, while others had it on the right side, so that the two varieties were mirror images of each other.
These crystals had been obtained from a solution that had no effect on polarized light, and Pasteur suspected that one type of crystal produced one type of twist while the other produced the opposite type, the two together canceling each other. To check this, Pasteur separated the crystals painstakingly with tweezers, putting all the lefts to one side and all the rights to another. He dissolved them separately, and sure enough, one solution twisted the polarized light clockwise and the other, counterclockwise.
Crystal asymmetry could be one reason for this optical activity, but it could not be the sole reason. After all, the solution twisted the plane of polarized light when the crystals were dissolved and gone. There had to be a more deep-seated asymmetry present, but it took another quarter-century before that was discovered.
çCrystallography
1781 A.D.
FRANCE
Crystal is from a Greek word for "ice" or "frozen." Since ice is sometimes transparent, the word crystal came to be used for any transparent object. Thus, a fortune-teller uses a "crystal ball" that is a ball of ordinary glass. The planets were thought to be set in "crystalline spheres" because those spheres were transparent.
When quartz was found, it had the properties of rocky material, but it was transparent. Since bits of quartz often had straight edges, planar faces, and sharp angles, people began to speak of any solids with straight edges, planar faces, and sharp angles as crystals, even when they were not transparent.
In 1781, a French mineralogist, René-Just Haüy (1743-1822), was handling a piece of calcite crystal that had a rhombohedral shape (a kind of slanted cube). Accidentally, he dropped it and it shattered. Haüy noticed that the pieces all had a rhombohedral shape. He broke more pieces of calcite and found that, no matter what the original shape was, it broke into rhombohedrals.
Haüy suggested that each crystal was built of successive additions of what we now call a unit cell, which formed, in the absence of external interference, a simple geometrical shape with constant angles. He felt that an identity or difference in crystalline form implied an identity or difference in chemical composition.
In this way, Haüy founded the modern science of crystallography.
Cubic Equations
1535 A.D.
ITALY
At this time, mathematicians found it easy to solve equations of the first degree (linear equations, involving x) and of the second degree (quadratic equations, involving x^2). Equations of the third degree (cubic equations, involving x^3) defeated them.
In 1535, however, the Italian mathematician Niccolò Tartaglia (1499-1557) found a general method for solving cubic equations. In those days, mathematicians would often keep their discoveries secret and parade their ability to solve problems others could not. This raised their reputations and gave them a feeling of power. However, another Italian mathematician, Geronimo Cardano (1501-1576), wheedled the cubic equation solution out of Tartaglia and then published it, so that Cardano is often given credit for the discovery. Tartaglia objected loudly, but the event set an important precedent.
Scientific discoveries do not belong to the discoverer but to the world. If discoverers all clutched their discoveries close to their chests in order to garner personal glory, the progress of science would creak to a halt. It has therefore become a rule that credit for a discovery goes not necessarily to the original discoverer, but to the first who publishes the discovery.
This encourages publication and allows all scientists to learn of discoveries as soon as possible. Science as we know it would not exist without the "first publication" rule, and Cardano, by his dishonorable action, pushed science in that direction, thus doing the world more good than he did Tartaglia harm.
#Uranium Radiation
1897 A.D.
PARIS, FRANCE
One of those who followed up instantly on the 1896 discovery by French physicist Antoine-Henri Becquerel (1852-1908) of the radiation from potassium uranyl sulfate was a Polish-born French chemist, Marie Sklodowska Curie (1867-1934). She was the wife of French chemist Pierre Curie.
In 1897 she made use of her husband's discovery of piezoelectricity to measure the intensity of radiation given off by a variety of uranium compounds. She showed that the intensity was always in proportion to the quantity of uranium present.
This demonstrated that the radiation did not come from the compound as a whole, but from the uranium atom specifically. It was an atomic phenomenon and not a molecular one.
Marie and Pierre Curie continued to work on the radiations produced by uranium.
αCyclic-AMP
1960 A.D.
CLEVELAND, OHIO
Adenylic acid, also known as adenosine monophosphate (AMP), is one of the nucleotides that make up the molecular chains of nucleic acids. The American pharmacologist Earl Wilbur Sutherland, Jr. (1915-1974) had discovered it in tissue some years earlier, and in 1960 he worked out its structure. He found that the phosphate group was attached to the rest of the molecule in two different places rather than one. A ring of atoms was thus formed, and Sutherland called it cyclic-AMP.
Cyclic-AMP has a profound effect on the course of metabolism within a cell, since it apparently controls the way hormones can penetrate cells. For this work, Sutherland was awarded the Nobel Prize for physiology and medicine in 1971.
àCyclotron
1930 A.D.
U.S.A.
The particle accelerator developed by Cockcroft and Walton forced particles to travel in a straight line, faster and faster, thus piling up more and more energy, while being pushed on ahead by a magnetic field. The difficulty with this was that in order to get really high energies, the device had to be inconveniently long.
It seemed to the American physicist Ernest Orlando Lawrence (1901-1958) that, instead of pushing the particles ever onward, it might be handier to make them travel in circles, giving them a magnetic-field push each time they came around.
In 1930, therefore, he built a small device in which protons were made to travel between the poles of a large magnet that deflected their paths into circles. At each turn, they received another push of electric potential. This made them travel faster and therefore in a path that, under the constant force of the magnet, curved less sharply. The path was a sort of spiral that brought them closer and closer to the rim of the instrument. By the time the charged particles finally shot out of the instrument altogether, they had accumulated high energies indeed.
Lawrence called the device a cyclotron, because the particles moved in cycles. His first device was quite small, but it produced more energetic particles than a very long voltage multiplier would have.
For this, Lawrence was awarded the Nobel prize for physics in 1939.
⌠Cylinder Locks
1865 A.D.
STAMFORD, CONNECTICUT
Human behavior being what it is, there has always been a demand for locks. A lock becomes more useful if it is small and not easily picked; if the key is small and not easily duplicated. No lock can be perfect, but some are obviously better than others.
In 1865 an American locksmith, Linus Yale (1821-1868), patented a cylinder lock with tumblers that had to be brought into a certain alignment if the lock was to open. The key had a serrated edge that sufficed to bring the tumblers into line. A vast number of combinations were possible, so that every key could be unique, even if there were millions of locks. The familiar locks and keys that have controlled house and apartment doors ever since are based on this principle.
zPhotography
1839 A.D.
PARIS, FRANCE
The French artist Louis-Jacques-Mandé Daguerre (1789-1851) had been working for years on a scheme for causing light to fall on a suspension of silver salts in such a way as to darken it selectively and produce a duplication of some scene. This is called photography, from Greek words meaning "light-writing." The difficulty lay, first, in performing the feat after a reasonably short exposure and, second, in keeping the silver salts from continuing to darken and erasing the photograph.
By 1839 Daguerre had learned to dissolve the unchanged silver salts with a solution of sodium thiosulfate, so that what was left was permanent. It still required an exposure of at least 20 minutes, however, and the photographs that were obtained were faint.
Nevertheless, photography was born, and as others turned to it enthusiastically, the technique was very rapidly improved.
vNeutrino Mass
1980 A.D.
UNITED STATES
In 1980 Frederick Reines reported on experiments that indicated neutrinos might have tiny quantities of mass (for years they had been thought to be massless).
Researchers in Moscow reported similar results in an entirely different experiment and thought the neutrino mass might be 1/13,000 of an electron. If this were so, then the three neutrinos -- the electron-neutrino, the muon-neutrino, and the tauon-neutrino -- might well have slightly different masses and be capable of oscillating; that is, of continually changing from one to another.
If this were so, it would explain the fact that the Sun seems to emit only one-third the number of neutrinos it ought to. It should be emitting electron- neutrinos only, and detecting devices would only pick up electron-neutrinos. But if the neutrinos oscillated, the electron-neutrinos emitted by the Sun might change into muon-neutrinos and tauon-neutrinos en route to Earth and arrive here in equal quantities. The detecting devices would then pick up only the one- third that were electron-neutrinos.
Then, too, even if the neutrinos had only a tiny mass, there were so many neutrinos in the Universe that their total mass might make up a hundred times as much mass as everything else put together. The presence of this mass, ignored until now by astronomers, might explain how galaxies rotate, how clusters of galaxies hang together, and how the galaxies formed in the first place. All these things would make sense if the "mystery of the missing mass" were solved by attributing it to neutrinos.
Furthermore, the presence of missing mass in the form of neutrinos would be just sufficient to close the Universe; that is, to make certain that the Universe would someday begin to contract again.
The only trouble with all this is that the question of the neutrino's mass has not yet been confirmed, and it may well be a false alarm.
ê
Natural Selection
1859 A.D.
DOWN, UNITED KINGDOM
The British biologist Charles Robert Darwin (1809-1882), like many biologists, believed that life forms had evolved; that some species, with time, changed into other related species, while some species became extinct.
What puzzled Darwin was the mechanism that drove evolution onward. In 1838 he read Malthus and realized that not only human beings multiplied past the food supply available, but that all living things did.
Therefore, in each generation, there was a competition for survival among the too-many, and those tended to survive who could snatch enough food, or best evade a predator. In short, nature itself would select a few from the many for survival. The characteristics that made survival likely would be inherited by the offspring of the survivors and again there would be a natural selection.
Darwin assumed that there were always variations among offspring, random and tiny variations perhaps, and that nature then used those variations as a means of selection, so to speak. The "better" among the variations would not always do better, since there was always the factor of chance, but on the whole, and in the long run, they would.
Darwin was theorizing, then, on evolution by natural selection. Knowing that this idea would create enormous controversy, and being a gentle person who could not bear to participate in such controversy, he spent some 20 years gathering evidence for his point of view, hoping that when he did publish, the evidence would be so overwhelming that it would preclude argument (though in this he was naive).
In 1858 another British biologist, Alfred Russel Wallace (1823-1913), was in the East Indies. He too had read Malthus and arrived at the notion of evolution by natural selection. Unhampered by Darwin's fear of controversy, Wallace wrote up his theories in three days. Then, in order that his views might be checked by an appropriate expert, he sent his 11-page paper to Darwin, who could scarcely believe his eyes when he saw himself so anticipated.
There was nothing for Darwin to do but to suggest a joint publication and this was carried through immediately. In the next year, 1859, Darwin reluctantly published a book, best known as The Origin of Species, in which he presented his theory in detail (but not in as much detail as he would have liked, for he had been planning a book five times as long at least). Darwin's book was the most notable scientific work since English scientist Isaac Newton's great classic. It was the foundation of a new biology, as Newton's had been the foundation of a new physics. It changed the very current of people's thinking, and the world has never been the same.
$DDT, The Insect Killer
1939 A.D.
SWITZERLAND
The most serious enemies of humanity, next to pathogenic microorganisms, are the insects. Not only do they carry and spread diseases such as yellow fever, malaria, typhus, and encephalitis, but they also eat crops and make serious inroads into the human food supply. Through the ages, they have been feared and fought, and as knowledge of chemistry grew, poisons had been used to kill them.
Unfortunately, the inorganic poisons used, such as Paris green, were deadly to mammals, including human beings.
The Swiss chemist Paul Hermann Müller (1899-1965) began a search for organic substances that might be poisonous to insects but not to other forms of life, and that would also be cheap, stable, and without unpleasant odor.
In September 1939 he tried dichlorodiphenyltrichloroethane (of which the common abbreviation is DDT=+=+=+), a compound known to chemists since 1873, and it seemed to fulfill all the requirements. DDT proved exceedingly valuable in the years to come, particularly in fighting lice-spread typhus, so that Müller was awarded the Nobel Prize for medicine and physiology in 1948.
In time, to be sure, DDT turned out to have its harmful aspects after all, and its use dwindled. Nevertheless, it was the forerunner of a great variety of pesticides that have served humanity.
ùDeep-Sea Life
1868 A.D.
ATLANTIC OCEAN
It was easy to assume that life in the sea was confined to the uppermost layers. After all, light could only penetrate about 250 feet below the surface of the ocean, and since plants depend on light, they couldn't exist lower than that. Since animals can't live without plants to feed on, it seemed they couldn't exist any lower than that either.
When cables were being laid under the Mediterranean Sea and under the Atlantic Ocean, however, life forms were occasionally brought up from great depths. Scientists were reluctant to believe this. Then in 1868 a British zoologist, Charles Wyville Thomson (1830-1882), began a series of deep-sea dredging operations that, after eight years, had led him some 70,000 zigzag miles over the oceans. He made 372 deep-sea soundings and showed once and for all that life inhabits the ocean from top to bottom.
What happens is that when plant life near the surface dies, it drizzles downward, and some escapes being eaten all the way to the bottom. The animals that live on this drizzle also die and themselves add to the drizzle. Deep-sea life does not live in the profusion that surface life does, but it exists.
ZOcean Vent Life
1977 A.D.
ATLANTIC OCEAN
In 1977 it was discovered that there were ocean vents, or "chimneys," that continually spewed hot water laden with minerals into the ocean. Bacteria could live in these surroundings by obtaining energy from the oxidation of sulfur compounds present in the spewings. Other life forms could live on the bacteria, so that at the other end of the food chain, large clams and tube-worms were supported.
Here was an entire society that lived on chemical change involving neither light nor photosynthesis. That such complex life forms could exist independently of photosynthesis had not been expected.
Independent research at this time discovered primitive forms of bacterial life that obtained energy by reducing carbon dioxide to methane. These methanogens live independently of oxygen.
Obviously bacterial life is tremendously versatile.
mThe Triode
1906 A.D.
YALE, NEW HAVEN, CONN
The rectifying diode worked out by British electrical engineer John Ambrose Fleming (1849-1945) was a useful tool but limited in its range. That range was extended in 1906 by the American inventor Lee De Forest (1873-1961). He inserted a third element, called a grid, into the tube to make it a triode (three electrodes).
The grid is an electrode with holes in it, so that electrons can move from the hot filament through the holes of the grid to the plate. Even a weak charge placed on the grid can have a relatively enormous effect on the electron current. It can increase the intensity of the current if the grid is slightly positively charged, since it then attracts electrons from the heated filament; and it can decrease the intensity if slightly negatively charged, since it then repels electrons. By placing a small varying charge on the grid, you get a much larger variation in the electron flow.
A triode therefore acts as an amplifier, and it can be modified to perform a great variety of tasks. Radio became more than ever adapted to the transmission of sound through Fessenden's modulation.
ôDentistry
1728 A.D.
FRANCE
The first book to be devoted entirely to dentistry appeared in 1728. It was Le chirurgien dentiste (The Dental Surgeon), and it was written by a French dentist, Pierre Fauchard (1678-1761). He discussed artificial dentures and crowns and described how to treat caries by cleaning out the decay and making use of metal fillings. Because of this, Fauchard is considered the father of dentistry.
*Deoxyribose
1929 A.D.
U.S.A.
Levene had identified the sugar in some molecules of nucleic acid as ribose. There were other nucleic acids from which a sugar that was not ribose could be obtained, but it was not till 1929 that Levene could identify that other sugar. It turned out to be deoxyribose, which had a molecule just like that of ribose except for a missing oxygen atom.
That meant that there were two types of nucleic acid: ribosenucleic acid and deoxyribonucleic acid, usually abbreviated as RNA and DNA, respectively. It was DNA that was found in chromosomes.
+Analytic Geometry
1637 A.D.
PARIS, FRANCE
The French mathematician René Descartes (1596-1650) published, in 1637, his Discours de la méthode (Discussions on the Method) -- of finding scientific truth by good reasoning, that is.
In a hundred-page appendix to this book, Descartes combined algebra and geometry. He pointed out that if one drew two perpendicular straight lines, marked the intersection 0, and laid off units on each line, positive numbers to the right and up, negative numbers to the left and down, then every point in the plane could be represented by two numbers, one for its position along the horizontal axis and the second for its position along the vertical axis. (One could add a third axis, in and out, and locate every point in the Universe by three numbers.)
Straight lines and curves could then be expressed by algebraic equations, which would locate every point on the line or curve with reference to the two axes. This combination of disciplines, producing analytic geometry, strengthened both. Geometric problems could be solved algebraically, and algebraic equations could be illustrated geometrically.
It also laid the foundation for the development of the calculus, which is essentially the application of algebra to smoothly changing phenomena that can be represented geometrically by curves of various sorts.
╔Deuterium
1931 A.D.
U.S.A.
As more and more stable elements proved to be made up of mixtures of isotopes, there was considerable feeling that even the lightest and simplest of the elements, hydrogen, ought to consist of isotopes. Hydrogen has an atomic weight of very close to 1, so that if it did consist of isotopes, hydrogen-1 must be overwhelmingly the most common. Still, there might be very small quantities of hydrogen-2 present.
The American chemist Harold Clayton Urey (1893-1981) tackled the problem in 1931. He reasoned that hydrogen-2, being the more massive atom, would be less easily evaporated than hydrogen-1. If, then, he slowly evaporated a large quantity of liquid hydrogen, the final bit of liquid ought to have a percentage of hydrogen-2 larger than that in the supply he began with.
Now if hydrogen-2 were present, its spectral lines ought to have slightly different wavelengths than those of hydrogen-1, and the ordinary hydrogen spectrum ought to have, accompanying each spectral line, a very faint one nearby -- too faint to be sure of.
However, when most of the liquid hydrogen had evaporated, leaving an unusually high concentration of hydrogen-2, the hydrogen-2 lines ought to become more prominent and should be unmistakable.
This turned out to be so, and Urey announced the discovery at once. Hydrogen- 2 came to be called heavy hydrogen or deuterium (from the Greek word for "two"). For this discovery, Urey was awarded the Nobel Prize for chemistry in 1934.
▌Distant Galaxies
1988 A.D.
OUTER SPACE
New instruments and computerized techniques made it possible to detect galaxies with red shifts greater than any previously seen; greater even than those of quasars.
In 1988 some were detected that might be as much as 17 billion light-years away. This was important with respect to the birth of the Universe. If the galaxies were 17 billion light-years away, it had taken their light 17 billion years to reach us, and we were seeing them as they existed 17 billion years ago. This meant that even 17 billion years ago the Universe was old enough to have formed galaxies.
The age of the Universe has not been determined precisely. It depends on knowledge concerning the distance of galaxies and the rate at which the Universe is expanding. These are uncertain quantities. The age of the Universe has been set at somewhere between 10 and 20 billion years, with 15 billion as the most probable.
If the distant galaxies are actually at the distance estimated, however, it would seem that the Universe must be older than we had thought. Again, any information we can get from those distant galaxies may tell us more about the formation and youth of galaxies, and that may change our ideas about how and when the Universe formed.
┤Diamond
1772 A.D.
FRANCE
One of the substances that Antoine Lavoisier burned was a diamond. He and some other chemists invested in one, placed it in a closed vessel, and then focused sunlight on it with a magnifying glass. The diamond, when it grew hot enough, simply disappeared, and carbon dioxide appeared within the vessel. The conclusion was that diamond consisted of carbon and, despite appearances, was chemically very closely related to coal.
√Diastase
1833 A.D.
FRANCE
A French chemist, Anselme Payen (1795-1871), managed a factory engaged in the refining of sugar from sugar beets. This turned his attention to plant chemistry.
In 1833 he reported the separation of a substance from malt extract that had the property of hastening the conversion of starch to glucose. Payen called the substance diastase, from a Greek word for "separate," for in a sense, it separated the building blocks of starch and produced the individual glucose units.
This was an example of an organic catalyst. Yeast is an organic catalyst that was known even to prehistoric humanity, but yeast is a living organism.
Diastase was the first organic catalyst to be isolated from living material that would display catalytic activity without being a living organism itself.
Diastase is an example of what later came to be called an enzyme, and it was the first enzyme to be prepared in concentrated form. Because of it, the suffix -ase eventually came to be used in the names of enzymes generally.
ôDiesel Engine
1897 A.D.
MUNICH, GERMANY
The four-stroke engine invented by German engineer Nikolaus August Otto (1843-1910) used low-boiling gasoline for fuel and ignited the vapor-air mixture with an electric spark.
A German inventor, Rudolf Diesel (1858-1913), tried to eliminate the complexities that resulted from running an electrical system in conjunction with an engine. By 1897 he had perfected a Diesel engine that ignited the vapor-air mixture by the heat developed through compression. This allowed him to use higher-boiling fuel such as kerosene, which was cheaper and less flammable (hence safer) than gasoline.
However, the compression had to be great, so the Diesel engine had to be considerably larger and heavier than the Otto engine if the higher pressures were to be brought about and maintained. Diesel engines therefore found their use in heavy transport vehicles such as trucks, buses, locomotives, and ships.
ÿDietary Deficiency Diseases
1896 A.D.
THE NETHERLANDS
People in the Dutch East Indies commonly suffered from beriberi, which produced weakness and death. Naturally it was assumed to be a germ disease, since Pasteur and others had been so successful at combating disease on that assumption. However, no one could find the germ that caused the disease.
A Dutch physician, Christiaan Eijkman (1858-1930), who had gone to the East Indies to study the disease, was nonplussed. But then an ailment broke out in 1896 among the chickens being used at the laboratory for bacteriological researches. The chicken polyneuritis showed symptoms similar to beriberi, and Eijkman was busily studying the disease and checking on its contagiousness -- when it suddenly disappeared and all the chickens got well.
Eijkman investigated and found that during the period when the chickens had had the disease, they had been feeding on rice ordinarily meant for the human patients. The disease disappeared when a new cook put them back on commercial chicken feed. Eijkman found he could produce the chicken disease at will when he fed the chickens polished rice. By feeding them unpolished rice, he cured them.
Eijkman was the first to correct a specific disease by diet since Lind had connected citrus fruits and scurvy. Although Eijkman missed the point at first, it became clear that beriberi was a dietary deficiency disease. It was caused by the absence of some substance (present in the hulls of unpolished rice and not present in polished rice from which the hulls had been removed) that seemed necessary to health in small traces.
For this discovery, Eijkman received a share of the Nobel Prize in physiology and medicine in 1929.
∩Dipole Moments
1912 A.D.
NETHERLANDS
Now that it was understood that electrons formed part of atoms, it followed that when atoms joined to form molecules, electrons ought to be distributed over the various atoms of the molecules.
Such distribution might be symmetrical, so that the molecule was electrically uncharged, or unsymmetrical, so that one part of the molecule might have a surplus of electrons and thus a slight negative charge while another part might have a deficit of electrons and a slight positive charge. These would represent positive and negative poles of the molecules, which would thus be polar molecules, or molecular dipoles.
Naturally, polar molecules and nonpolar molecules would act differently with respect to electric fields. In addition, polar molecules would attract each other, positive toward negative, and therefore have higher melting and boiling points than nonpolar molecules of similar size.
In 1912 a Dutch physical chemist, Peter Joseph William Debye (1884-1966), worked out a set of equations that would represent the behavior of such polar molecules. This gave rise to the concept of dipole moments and greatly helped chemists understand the behavior of molecules.
For this work, Debye was awarded the Nobel Prize for chemistry in 1936.
> Math and Astronomy
1800 B.C.
SUMERIA (IRAQ)
The concept of mathematics is as old as human beings. Even some animals have a primitive number sense. It is certainly difficult to believe that the pyramids, for instance, could have been built without substantial ability in geometry.
The Sumerians, and the Babylonians who succeeded them, were the first to make significant advances in mathematics and in astronomy. By 1800 B.C., they had developed a number system based on 60 that we still follow in some ways, since we still have 60 seconds to the minute and 60 minutes to the hour. Why 60? Because it can be evenly divided by 2, 3, 4, 5, 6, 10, 12, 15, and 30, thus eliminating the frequent need of fractions -- with which the ancients had trouble.
In addition, there are 360 degrees (6 x 60) in the circle. Again, it is a number easily divided. In addition, the Sun takes 365 days to move completely around the sky, so that it travels, relative to the stars, just about 1 degree per day. That too may have influenced the choice of 360.
The sky-watchers of the Tigris-Euphrates valley eventually discovered that, in addition to the Sun and Moon, five bright stars changed position against the remaining "fixed" stars. These moving stars, which we call planets (from a Greek word for "wandering") were given the names of gods and goddesses, and we still do that today. We call the five bright stars Mercury, Venus, Mars, Jupiter, and Saturn. The presence of seven such planets (if we include the Sun and the Moon) gave rise to the seven-day week, with one of the planets in charge of each day. The week as a unit of time was thus instituted by the Babylonians and was adopted first by the Jews, then by the Christians, and through them, by virtually all the modern world.
The seven planets had paths around the sky, paths that passed through certain conglomerations of stars that were termed, in total, the zodiac by the later Greeks. This was divided into 12 constellations, so that the Sun remained in each constellation for about a month. Eventually the Sumerians and Babylonians worked out the pathways in some detail and could predict, in at least a rough manner, where the planets would be at future times. That represented the beginning of mathematical astronomy.
Since the Sun affected the Earth profoundly, making the difference between the day and night, and the Moon's phases marked the length of the month, it seemed natural to suppose that the other planets also had significance to human beings. Imaginative suggestions were made about the influence of each, as it varied in position with respect to the stars and other planets, and an intricate system of foretelling the future from planetary positions was evolved. This is astrology.
Astrology is not true, but people strongly want the security of knowing the future, so that even today astrology is accepted by many people.
mDissection
1316 A.D.
ITALY
The stirrings of humanism allowed scholars to grow more interested in science. In the medical schools of Italy, it even became possible to dissect cadavers once again. The greatest of the new group of anatomists was the Italian Mondino de Luzzi (ca. 1275-1326), who taught at the medical school of Bologna.
In 1316 he published the first book in history to be devoted entirely to anatomy. He remained under the influence of the Greek and Arabic writers and clung to them sometimes in preference to the evidence of his own eyes. Nevertheless, his book remained the best there was for two and a half centuries.
ÖEncke's Distance to the Sun
1824 A.D.
BERLIN, GERMANY
A century and a half before, Cassini, making use of the parallax of Mars, had estimated the distance of the Sun from Earth as 87,000,000 miles.
In 1824 Encke, using the time that Venus entered the Sun's disk and left it during its transits, announced the Sun to be 95,300,000 miles from Earth. This was better than Cassini's figure had been. Encke's figure was only 2.6 percent too high.
*Distance to the Sun
1941 A.D.
LONDON, ENGLAND
The earliest reasonable estimate of the distance to the Sun had been based on Cassini's measurement of the parallax of Mars. Measurement of the parallax had improved with time, but it was always difficult to deal with Mars in this respect, since it showed a small orb in the telescope, which forced a certain ambiguity on the measurement of its exact position.
Nearly a century before, the German astronomer Johann Gottfried Galle (1812-1910) had suggested that the parallax of an asteroid be used for determining the scale of the Solar System and the distance of the Sun, since its size and starlike appearance would make its positioning more accurate. However, asteroids were farther off than Mars and their parallax was correspondingly smaller and harder to measure.
But then Eros had been discovered by Witt, and Eros could on occasion approach more closely than any planet.
In 1931 Eros approached within 16,000,000 miles of Earth, and a long, detailed program was set up in advance. Fourteen observatories in nine countries took part under the leadership of the English astronomer Harold Spencer Jones (1890-1960). Seven months were spent on the project, nearly three thousand photographs were taken, and the position of Eros was determined on each.
Ten years of calculation followed, and by 1941 Jones was able to announce that the distance of the Sun was 93,005,000 miles. That was the most accurate determination yet and was probably the best that could be done until methods transcending the accuracy of parallax determination were devised.
<The First Observatory
1577 A.D.
SWEDEN
Tycho Brahe (1546-1601), with the help of the Danish king, set up the first real astronomical observatory, on the island of Hven in the strait between Denmark and Sweden, outfitting it with the best instruments he could make.
In 1577 a bright comet appeared in the sky and Tycho observed it carefully. By Greek notions, it was an atmospheric phenomenon, and therefore it should have a large parallax. However, Tycho could find none, and was certain that it was at a distance far beyond that of the Moon. This was another serious blow against Greek astronomy.
!Distance to the Stars
1838 A.D.
ENGLAND
Since the Earth moves around the Sun, the nearer stars should show a parallactic displacement compared with the farther ones. Bradley, when trying to detect stellar parallax, had discovered light aberration instead.
Herschel, in the same attempt, had discovered binary stars instead.
The trouble was, the stellar parallax was so small that not till the 1830s did telescopes become sufficiently refined to detect it. At this time, the British astronomer Thomas Henderson (1798-1844) measured the parallax of Alpha Centauri from his observatory at Capetown in South Africa. (Alpha Centauri was so far south that it could not be observed from Europe.) The German astronomer Friedrich Georg Wilhelm von Struve (1793-1864), while working in Russia, measured the parallax of Vega.
Alpha Centauri is the third-brightest star in the sky, and Vega the fourth- brightest, so there was a chance they were comparatively close. The German astronomer Friedrich Wilhelm Bessel (1784-1846) chose the star 61 Cygni, which was rather dim but had the fastest proper motion (the apparent shift in position across the sky) then known, so that it was likely to be close, too.
Henderson was the first to complete the determination, but Bessel was the first to publish, in 1838, and it is he who gets the credit. His star, 61 Cygni, turned out to be about 35 quadrillion miles away. This distance is so mighty that even light takes 6 years to reach us from 61 Cygni -- so that it is 6 light-years away. Alpha Centauri is only 4.3 light-years away, and it is actually the star closest to ourselves. Vega is 11 light-years away.
These distances made the Universe suddenly much larger than astronomers till then had dreamed. The entire Solar System shrank to a dot in space in comparison to the distance of even the nearest stars.
δDistilled Liquor
1300 A.D.
SPAIN
Natural fermentation has its limits. As fruit or other materials ferment, alcohol accumulates and eventually grows sufficiently concentrated to kill the yeasts or other microorganisms that were producing the fermentation. The alchemists had learned how to distill: how to heat a substance and drive off the volatile materials, which could condense into liquid elsewhere, leaving behind dissolved matter. Thus, if sea water is heated, the vapors consist only of water, and if cooled, this is drinkable. The salt is left behind and has its own uses.
Eventually, alcoholic beverages were distilled. Since alcohol boils at a lower temperature than water does, the initial vapors of the beverage are higher in alcohol than the original liquid. If the vapors are then cooled and condensed, the result is a stronger liquor with a good deal more of a "kick" than the original has.
In 1300 the Spanish alchemist Arnau de Villanova (ca. 1235-1312) distilled wine and obtained reasonably pure alcohol for the first time. In the process, of course, he prepared brandy, which is distilled wine with a much higher alcohol content than ordinary wine. Not only brandy, but whiskey (made by distilling fermenting grain) became available in sizable quantities.
VThe Shape of DNA
1953 A.D.
CAMBRIDGE, ENGLAND
The work of American biochemist Erwin Chargaff (b. 1905) and English biophysicist Rosalind Elsie Franklin (1920-1958) in 1952 had supplied the information necessary to work out the structure of DNA. The key conceptual step was then taken by the English physicist Francis Harry Compton Crick (b. 1916) and the American biochemist James Dewey Watson (b. 1928). They made use of a key X-ray diffraction photograph taken by Franklin and made available to them by her boss, the New Zealand physicist Maurice Hugh Frederick Wilkins (b. 1916), apparently without Franklin's knowledge or permission.
In 1953 Watson and Crick suggested that DNA consisted of two chains of nucleotides arranged as a double helix, with the purine and pyrimidine bases facing each other and the phosphate links on the outside. Each two-ringed purine faced a one-ringed pyrimidine, so that the space between the two strands was constant. Adenines and thymines were paired, as were guanines and cytosines (thus accounting for Chargaff's results). Each strand of the double helix was a model (or template) for the other. In cell division, each DNA double helix would separate into two strands, and each strand would build up its complementary strand on itself; an adenine fitting over every thymine on the strand, a thymine over every adenine, a guanine over every cytosine, and a cytosine over every guanine. In this way two double helixes would appear where there had been one before. Thus DNA underwent replication without changing its structure except for very occasional accidental errors, which represented mutations.
The Watson-Crick structure made so much sense that it was accepted at once. Watson, Crick, and Wilkins shared the Nobel Prize for physiology and medicine in 1962 as a result. By that time Franklin was dead, and her involvement did not have to be considered.
DNA, Humans and Chimps
1984 A.D.
WORLD
DNA molecules change with time, forming mutations. Presumably, if the DNA molecules of two different species are compared, then the more closely related the species are, the fewer the differences. And from the number of differences, one can tell, perhaps, the length of time it has taken the two species to differentiate from a common ancestor. Since the mutations are the result of chance changes, conclusions cannot be drawn with mathematical certainty, but they are suggestive.
In 1984 such DNA analysis was used to present reasons for supposing that human beings and chimpanzees were more closely related to each other, evolutionarily, than either was to gorillas or orangutans, and that human beings and chimpanzees diverged from a common ancestor some five to six million years ago.
φ DNA as the Genetic Material
1944 A.D.
U.S.A.
By now it had been understood for some 40 years that chromosomes carried the genetic material. It was also known that chromosomes were nucleoprotein in character, containing both protein molecules and de-oxyribonucleic acid (DNA) molecules.
It was assumed that the key portion of the genetic material in chromosomes was the protein, since at every point proteins seemed to be the key to living tissue. They were giant molecules of enormous variety and versatility; the enzymes, which controlled the chemistry of the body, were proteins. The nucleic acid was thought to consist of relatively small molecules that behaved as adjuncts, like the heme in hemoglobin or the coenzymes in enzymes -- though what the function of the nucleic acid adjunct might be was not known.
Then biochemists began discovering that nucleic acids were not small molecules after all. Methods of isolating DNA had been so harsh that the molecules were recovered in small fragments. Gentler isolation retrieved larger molecules. It was also noticed that in sperm cells, where chromosomes were condensed to minimum size, the protein portion seemed unusually simple while the DNA seemed present in the usual quantity and complexity. Nevertheless, faith in proteins remained unshaken.
At this time, a Canadian-born American bacteriologist, Oswald Theodore Avery (1877-1955), was working with pneumococci -- bacteria that caused pneumonia. Two different strains were grown in the laboratory -- one with a smooth coat made up of a complicated carbohydrate molecule and one with a rough surface. The strains were called S (for smooth) and R (for rough).
Clearly the R strain lacked a gene for the formation of the carbohydrate surface. It was possible to prepare an extract from the S strain that contained no cells and was clearly nonliving, which on addition to the R strain would convert it into an S strain. The extract must contain the gene (or transforming principle) that catalyzed the production of the carbohydrate. But what was the chemical nature of the transforming principle?
In 1944 Avery and his associates purified the transforming principle as far as they could while still leaving it functional and showed that it was DNA in nature and nothing else. There was no protein present. This was the first indication that the genetic material in cells was DNA and not protein. The discovery revolutionized genetics, which now began a quick advance.
Avery's discovery was clearly worthy of a Nobel Prize, but he died too soon to receive one.
Space Docking
1966 A.D.
HOUSTON, TEXAS
On March 16, the American satellite Gemini VIII linked up with another orbiting vessel. This was the first actual docking of one space vessel with another -- a maneuver essential if human beings were to be sent to the Moon and brought safely back.
πThe First Medicine
1550 B.C.
EGYPT
People are sure to get sick at times, or have accidents and be hurt. The problem of getting well, or being made well, naturally concerns everyone. To aid the coming of wellness, people might attempt to conciliate various gods by proper incantations or rituals, make use of various forms of ritualized behavior, or use parts of plants or animals thought to have curative value.
The first written compilation of such cures that we know of is an Egyptian papyrus dated about 1550 B.C. It was discovered in 1873 by a German archaeologist, Georg Moritz Ebers (1837-1898), and is called the Ebers Papyrus in consequence. It contains about 700 magical remedies and descriptions of folk medicine for the treatment of various ailments.
Extinction of the Dodo
1681 A.D.
MAURITIUS
Mauritius is an island about half again as large as the state of Rhode Island, located in the Indian Ocean 500 miles east of Madagascar. In 1598 the Dutch settled it and named it after Maurice of Nassau. The Dutch stayed, on and off, till 1710.
Mauritius had forms of life that had evolved in isolation and that were different from forms elsewhere. For example, there was the dodo, a flightless pigeon, larger than a turkey and with a huge hooked bill. It was harmless and unafraid (hence its name, perhaps) since there was nothing on Mauritius to threaten it.
Once settlers arrived, however, they and their domestic animals began to kill this inoffensive bird. This continued until the very last dodo died about 1680. Similar birds on nearby islands were also killed off. Now we have the expression "dead as a dodo."
It is hard to believe, nowadays, that such an unusual and interesting form of life should have been slaughtered so casually, with no attempt made to save a few, but it has happened over and over again. It is one of the brighter aspects of recent history that human beings are now desperately trying to save various endangered species, though considering the inexorable increase in the number of human beings and the space they must occupy, this is often a losing battle.
tNegative Numbers
1545 A.D.
ITALY
Until 1545, mathematicians had assumed that all numbers, whether integers, fractions, or irrationals, had to be greater than zero. It might seem, after all, that one could not possibly have less than nothing.
On the other hand, mathematicians knew there were such things as debts. To have no money and to owe a sum to someone else means having less than no money.
This might seem merely like practical business, nothing to do with ethereal numbers, but Italian mathematician Geronimo Cardano (1501-1576) showed, in 1545, that debts and similar phenomena could be treated as negative numbers, which would follow rules of mathematics very similar to those that ordinary numbers did. You could have negative integers, negative fractions, and negative irrationals.
In that same year, Cardano worked out a general solution for equations of the fourth degree, involving x^4.
Animal Domestication
12,000 B.C.
IRAQ
In the 1950s, fossil remains of dogs were found along with remains of humans in caves near Kirkuk in what is now northern Iraq. They dated from about 12,000 B.C.
How dogs came to be domesticated is not known, of course. My own guess is that, again, children were responsible. A child could form a close bond with a puppy that had been found abandoned, or that was left over when the mother was killed either in self-defense or for food. Once the bond was formed, the child would object strenuously to the use of the puppy as food, and parents might oblige.
It would quickly have turned out that dogs, being hunters and pack animals, will accept a human master as the pack leader. Dogs would go hunting with their masters, help in killing the game, wait for the human beings to take what they wanted, and be satisfied to be thrown a minor share. In this way human beings, for the first time, obtained the services of another species of animal.
By 10,000 B.C., another step had been taken, with the domestication of goats in the Middle East. The goats would be cared for, fed, and encouraged to reproduce. They would supply milk, butter, and cheese and, by dint of judicious culling, meat. What's more, since goats eat grass and other substances humans find inedible, the food supply was increased at no cost. (Dogs have to be given food that would otherwise fill human stomachs.)
Until then, people had found their food by hunting and gathering, with all the insecurities attendant on that. Herding provided a much more secure food supply.
ïDouble Refraction
1669 A.D.
DENMARK
Sometimes a discovery is so puzzling it must simply be put aside until science advances to the point where an explanation is possible. Thus, in 1669 a Danish physician, Erasmus Bartholin (1625-1698), obtained a transparent crystal of a type now called Iceland spar.
Bartholin noted that objects viewed through the crystal appeared double. It was as though some light were refracted by the crystal through one angle, with the rest refracted through a slightly different angle. The phenomenon was therefore called double refraction.
Bartholin further noticed that when he rotated the crystal, one of the images remained fixed and the other revolved about it.
Bartholin could not explain these observations, and neither could anyone else. The observations had to remain in suspended animation for a century and a half until enough was known about light for an explanation to become possible.
8Double Stars
1650 A.D.
ITALY
In 1650 the Italian astronomer Giambattista Riccioli (1598-1671) observed, telescopically, that Mizar, the middle star of the handle of the Big Dipper, was actually two stars so close together that they could not be seen as separate with the unaided eye. This was the first double star to be detected.
¥The Doppler Effect
1842 A.D.
AUSTRIA
The coming of the locomotive made a particular phenomenon much more noticeable than it had been earlier. The combination of speed and a warning whistle did the trick. People noticed that the whistle was high in pitch as the locomotive approached, and that the pitch dropped suddenly as the locomotive passed and began to recede.
An Austrian physicist, Christian Johann Doppler (1803-1853), explained the phenomenon correctly by pointing out that the sound waves partake of the motion of the source and so reach the ear at shorter intervals when the source is approaching -- hence higher pitch. When the source recedes, the waves reach the ear at longer intervals -- hence lower pitch.
Having done this in 1842, Doppler proceeded to check the matter experimentally a couple of years later. For two days, a locomotive pulled a flat car back and forth at different speeds. On the car were trumpeters sounding this note or that, while on the ground, musicians with a sense of absolute pitch recorded what they heard. Doppler verified his explanation in this way.
The Doppler effect turned out, in a few years, to have enormous importance in connection with astronomy.
╘Drake Strait
1578 A.D.
SOUTH AMERICA
The English navigator Francis Drake (1540 or 1543-1596) had made a career out of raiding the Spanish possessions in the Americas in the course of an undeclared war between England and Spain. It occurred to him that the Spanish settlements on the Pacific coast of the Americas were entirely undefended because none of Spain's enemies had made their way into the Pacific, so in 1572 he had landed at Panama, crossed the Isthmus, and became the first Englishman to see the Pacific.
In 1577 he set sail on an expedition that he hoped would carry him through the Strait of Magellan, which so far only Spanish ships had passed through. No one knew the exact extent of Tierra del Fuego, the land south of the strait, and some thought it was part of a vast Antarctic continent.
Drake passed through the Strait of Magellan in 1578 and was then struck by a storm in the Pacific and driven far enough south to see that open water lay to the south of Tierra del Fuego, which turned out to be nothing more than a moderately sized island. The water to the south of that island has been known as Drake Passage, or Drake Strait, ever since.
Drake sailed up the Pacific coast of the Americas as far as what we now call San Francisco Bay. He found no water route that would connect with the Atlantic Ocean, so he decided to sail westward across the Pacific. He reached England in 1580, the first person to circumnavigate the globe since Magellan's ship had done so six decades earlier.
₧Dreams
480 B.C.
GREECE
Dreams have always seemed to human beings to be a doorway into some strange and different world. Dreams in which people who were dead appeared and seemed to live and speak might have given rise to notions of ghosts and a spirit world, and reinforced belief in a life hereafter. Dreams that made little sense might seem like obscure messages from divine beings. Dreams are described as messages from Zeus in Homer, and as messages from God in both the Old and New Testaments.
The Greek philosophers, however, were wedded to rationalism. They felt that the Universe ran according to laws of nature that could be understood by observation and reasoning and did not require any supernatural force -- that is, any force outside of or superior to the laws of nature.
Thus, about 480 B.C., the Greek philosopher Heracleitus (ca. 540-ca. 480 B.C.) maintained that dreams had no meaning outside a person's own thoughts.
ôDry Cell
1867 A.D.
FRANCE
Batteries in use up to this time, including storage batteries, were made up of liquids inside a container. They had to be, since the chemical reactions required to produce an electric current proceeded in solution. Batteries containing fluid had to be handled with care. They could be easily tipped and spilled, and the fluid was usually corrosive.
In 1867, however, a French engineer, Georges Leclanché (1839-1882), devised a cell and, experimenting over the course of 20 years, gradually converted its fluid into a stiff paste by adding flour and plaster of Paris.
In the end, while such a cell was not really dry, it was not so wet that it would spill. It could be thrown about, placed on its side, and turned upside down without being adversely affected. It came to be called a dry cell. It was these dry cells that came to be used in myriads of small devices from flashlights to children's toys.
ΘDyes
1200 B.C.
TYRE, PHOENICIA
The human urge to beautify is irresistible, and since we can see colors, we usually find them, singly and in combination, to be more attractive than black and white. The Old Stone Age artists used colored earths to make their paintings.
As early as 3000 B.C., dyes were used to color otherwise white or yellowish cloth, both in Egypt and in China. Indigo, a blue color extracted from a plant, was used and madder, a red color extracted from the root of another plant. By 1400 B.C., cloth could be dyed in virtually all colors.
The chief trouble with most early dyes was that they tended to bleach in the sun and to wash out in water, so that dyed fabrics quickly grew dim and blurred.
One dye that was very resistant both to sun and water was obtained from a snail in the eastern Mediterranean. To obtain the dye was a tedious task, but the resultant red-purple color was brilliant and stayed brilliant. The city of Tyre in Phoenicia had developed this dye industry by 1200 B.C. so that the color was called Tyrian purple. Between the difficulty of amassing a quantity of it, and its great desirability, its price went sky-high, but it still sold, albeit only to the rich and powerful. Tyre grew wealthy out of its dye trade and was able to support its merchant fleet and undertake trading ventures that made it richer still.
Some believe that the Greek name Phoenicia, applied to the land in which Tyre was a city, came from a Greek word meaning "red-purple" in reference to the dye.
áDynamite
1866 A.D.
SWEDEN
During the 20 years since nitroglycerine had been discovered by Sobrero, it had been used in blasting roads through mountains, digging canals, and laying foundations. It fulfilled such tasks admirably, but it was such a touchy explosive that it sometimes blew up at the wrong time, destroying factories and killing people as well.
The Swedish inventor Alfred Bernhard Nobel (1833-1896) was a member of a family that produced nitroglycerine and had lost a brother in an explosion. He therefore sought a way of taming nitroglycerine. In 1866 he came across a cask of nitroglycerine that had leaked. The liquid had been absorbed by the packing, however, which consisted of diatomaceous earth, or kieselguhr (made up of the siliceous skeletons of myriads of microscopic diatoms).
The soaked kieselguhr remained dry, and Nobel experimented with the mixture.
He found that the nitroglycerine could not be set off without a detonating cap once it had been mixed with kieselguhr. Short of that, the mixture could be handled virtually with impunity. Once set off, though, the nitroglycerine in the kieselguhr retained its shattering quality.
Nobel called the combination dynamite (from the Greek word for "power"), and it replaced free nitroglycerine, initiating the era of safe use of explosives in construction. (At his death, Nobel left his estate of nearly 10 million dollars for the establishment of the annual Nobel prizes.)
"Dysprosium
1886 A.D.
FRANCE
Lecoq de Boisbaudran, who had already isolated gallium and samarium, was working on a rare earth ore containing holmium when he discovered that it contained a small amount of still another rare earth element, which he named dysprosium, from a Greek word meaning "hard to get at."
+Earth
1989 A.D.
BOULDER, COLORADO
You may have heard that Earth is a mere speck near the edge of our galaxy, and that is true. But don't underestimate Earth, it is actually an amazing -- but delicate -- little planet.
As many environmentalists have pointed out, Earth's atmosphere has just the right amount of ozone and carbon dioxide. If there was much more or less of either, Earth's surface would be too hot or cold.
Or, suppose Earth was a bit closer to the Sun. The added heat would prevent the clouds from raining. But move it a little farther away and too little water would evaporate from the oceans, so clouds would not form.
If you painted the Earth's surface a darker color, it would absorb too much heat. But paint it a lighter color and the surface would reflect too much heat and become too cold.
While Earth is small, its distance from the Sun and tilt and rotation and gravity and many other factors make it ideal for life.
This wonderful planet is a slightly flattened ball measuring about 24,860 miles around at the equator. It is covered with a 5- to 40-mile thick crust divided into plates that slide slowly around on the mantle, a mass of hot, gooey rock surrounding a core of molten metal.
Because Earth is slightly tilted in relation to the Sun, either its north or south end is closer to the Sun at any time. Sunlight strikes the closer end more directly and intensely, causing summer, and strikes the farther end at a greater angle and less intensely, causing winter.
Today, many scientists are encouraging us to change our lifestyles so we don't upset the delicate balance that makes Earth a wonderful place to live. They are concerned that some human activities, such as burning fossil fuels, clearing forests and releasing man-made chemicals into the atmosphere, may upset the planet's environment.
+Earth as a Magnet
1600 A.D.
ENGLAND
Although the compass had been known for nearly five centuries, no one knew why it pointed north. The English physician and physicist William Gilbert (1544-1603) put it to the test and published a book, De Magnete (Concerning Magnets), in 1600 in which he described his experiments.
For instance, he tested the general opinion that garlic would destroy magnetism and that diamonds would produce it. He rubbed magnets with garlic and the magnetism did not disappear. He rubbed unmagnetized iron with diamonds and magnetism did not appear. He took the precaution of doing this before witnesses.
The most important thing he did, however, was to take a large piece of loadstone and fashion a globe out of it. He located its magnetic poles and showed that a compass needle would point north if placed near the surface of this spherical magnet.
What's more, if he arranged for the compass needle to swivel vertically, it showed what was called magnetic dip, for it pointed straight through the body of the object. In fact, if the compass needle was held above the magnetic pole, it pointed straight down. (Magnetic dip was first noted on Earth's surface by an English navigator, Robert Norman in 1576.) Gilbert concluded, then, that compass needles acted the way they did because Earth itself was a huge magnet.
óEarthquakes and Faults
1911 A.D.
SAN FRANCISCO, CALIFORNIA
It was known that there were faults in the Earth's crust, regions where two dissimilar sets of rocks came together. It was as though there had been a smooth stretch of rock originally, which had cracked, with one side sliding along the other to produce a mismatch. The general feeling was that such faults were produced by earthquakes.
The American geologist Harry Fielding Reid (1859-1944) studied the San Francisco earthquake and came to the conclusion, in 1911, that the reverse was true. The fault existed first, and the earthquake resulted when pressure upon the fault caused it to slip further.
This idea has been accepted ever since.
oLandsat I
1972 A.D.
CAPE CANAVERAL, FLORIDA
In 1972 the United States launched Landsat I, the first satellite specifically designed to take large-scale photographs of Earth that would make it possible to study global resources. Not only did it give an overview of geological data, but it was capable of studying forest- and grain-growing areas, yielding data on normal and abnormal growths, plant disease, and so on.
Such Earth resource satellites are one of the many answers to those who ask why so much money and effort is expended on space when there are so many problems on Earth that are crying out for study. Space technology is a powerful tool for studying those problems.
The chief Soviet rocket achievement of the year was the Moon probe Luna 20, which, though without a crew, reached the Moon, made a soft landing, scooped up a sample of soil, and brought it safely back to Earth.
╓Newton Describes Earth
1687 A.D.
ENGLAND
In the Principia, English scientist Isaac Newton (1642-1727) referred to French astronomer Jean Richer's (1630-1696) expedition to Cayenne, in French Guiana, which helped determine the parallax of Mars. While there, Richer had found that a pendulum beat more slowly than it did in Paris, so that a clock that would have been correct in Paris lost two and a half minutes a day in Cayenne.
Newton pointed out that this could be so if the force of gravity were slightly weaker in Cayenne than in Paris or if Cayenne were farther from the Earth's center than Paris was. Since Cayenne, like Paris, was at sea level, the conclusion was that sea level must itself be higher at Cayenne than at Paris. Newton showed that if a body rotated, a centrifugal effect would act to counter gravitation to a certain extent and that this countering force would be zero at the poles and grow stronger and stronger as one moved away from the poles until it reached a maximum at the Equator. The centrifugal effect would, in other words, give rise to an equatorial bulge, which would make the diameter across the Equator somewhat longer than the diameter from pole to pole.
Jupiter and Saturn, which are much larger than Earth, spin much faster and are, in addition, made of lighter material. In their cases, the equatorial bulges are so great that their orbs look clearly elliptical rather than circular. Earth's outline drawn from pole to pole and back would also be slightly elliptical (though not noticeably so to the unaided eye). Instead of being almost perfectly spherical as the Sun and Moon are, Earth would be an oblate spheroid according to Newton's reasoning. (Of course, the matter would have to be checked by actual measurement eventually.)
╚Size of the Earth
240 B.C.
GREECE
Even after the Earth was known to be spherical, there was the question of how large that sphere might be. It was bound to be huge, since no traveler had ever been totally around it. There was always more Earth, unknown and as yet unvisited, up ahead.
But then a Greek scholar, Eratosthenes (ca. 276-ca. 194 B.C.), working at Alexandria, found a way to measure the Earth's circumference without leaving Egypt. At the summer solstice, he had been told, the Sun at noon cast no shadow at the city of Syene (modern Aswan), which was far south of Alexandria. That meant that the Sun was then directly overhead at Syene. At the same time, though, the Sun was 7 degrees from the zenith in Alexandria. This difference had to result from the fact that the Earth curved between Syene and Alexandria. Knowing the north-south distance from Syene to Alexandria, Eratosthenes could use mathematics to calculate how far it would take the curvature of the Earth, worked out between Syene and Alexandria, to take him all the way around the Earth.
He came out with a length of 25,000 miles for Earth's circumference. He was correct.
The ancients, however, thought his figure was too high and preferred to accept a lower one.
╟Revised Size of the Earth
1684 A.D.
FRANCE
Eratosthenes' figure for the circumference of the Earth in 240 B.C. had not been bettered in a thousand years.
In 1684, however, certain observations of the French astronomer Jean Picard (1620-1682) were published posthumously. Instead of noting the distance of the Sun from the zenith (the point in the sky that is directly overhead) at different places on the Earth by measuring its shadow, as Eratosthenes had done, Picard measured the distance of a star from the zenith at different places. With telescopes, that was the more accurate method, and Picard calculated the Earth's circumference as 24,876 miles and its diameter as 7,900 miles, figures that are very close to the best we have today.
²Earth's Climatic Zones
25 A.D.
ITALY
Anyone who traveled was bound to find that the climate was different in different places. In the north European forest, it was colder than it was in Greece, with longer, snowier winters. In Egypt it was warmer than in Greece, and cold weather was rare.
The idea was formalized by the Roman geographer Pomponius Mela about A.D. 25. Pomponius Mela, accepting a spherical Earth, suggested that it be divided into a North Frigid Zone and a South Frigid Zone in the neighborhood of the poles, a Torrid Zone in the neighborhood of the Equator, and a North Temperate Zone and a South Temperate Zone in between. This notion still holds today, even though variations in climate are far more complicated than would be thought from a consideration of zones alone.
dEaster Island
1722 A.D.
EASTER ISLAND
Dots of land scattered over the Pacific remained to be discovered by Europeans even two centuries after Magellan had made the first crossing. In 1722 the Dutch navigator Jacob Roggeveen (1659-1729) came across a small island, 45 square miles in area, that was one of the most isolated bits of land in the world. It was 1,200 miles from the nearest land, which was another small island like itself. Since the island was sighted on Easter Sunday, it was named Passeisland in Dutch, or Easter Island in English.
Easter Island was probably the farthest point reached by the Polynesians in their settlement of the Pacific Islands. The island is best known for 600 stone statues of a type found nowhere else. This has lent the island an air of mystery that it probably doesn't deserve.
Later in the same voyage, Roggeveen discovered the Samoan Islands.
┌Eastern United States
1990 A.D.
NORTHEAST, U.S.
Shown here is the Northeastern United States, the birthplace of the United States. People from Europe (particularly England and Germany) settled all along the northeast coast of the continent, and gradually spread westward.
The land was -- of course -- inhabited when the Europeans arrived, and unfortunately, conflicts often arose between settlers and Native Americans. And usually it was the Native Americans who suffered the most in these disputes.
~Eclipses
585 B.C.
MILETUS, ASIA MINOR
In studying the motion of the planets along the path of the zodiac, the Babylonian astronomers could not help but note that sometimes the motions would bring two of them fairly close together. This would be most spectacular in the case of the Sun and the Moon. Every once in a while the Moon would pass in front of the Sun and obscure part or sometimes all of it. At times, too, the Sun would be on one side of the Earth, and the Moon would be directly on the other. The Earth's shadow would then fall on the Moon, obscuring it. Thus, there could be either a solar eclipse or a lunar eclipse. (Eclipse is from Greek words meaning "to leave out," since when one happened, the Sun or the Moon would seem to be left out of the sky.)
An eclipse is a frightening spectacle. Those who become aware of it may actually think that the Sun or the Moon is dying, with incalculable consequences. Even if it is understood that the Sun or Moon is only obscured temporarily, there is a feeling that it is an omen of evil sent by the gods as a warning.
However, by studying the movements of the Sun and Moon, early astronomers learned to predict when eclipses would take place. Since that made the eclipses appear to be automatic and unavoidable phenomena, it removed their unexpected and ominous connotations. (There is some feeling that even prehistoric watchers of the sky learned to tell when lunar eclipses would occur, and that the stones at Stonehenge in southwestern England were arranged as a kind of observatory that allowed prediction of such phenomena.)
The Greek philosopher Thales (624-546 B.C.) seems to have learned the Babylonian methods and predicted an eclipse of the Sun, one that we now know (by calculating backward) took place on May 28, 585 B.C. This added greatly to Thales' prestige and also helped make eclipses less frightening, since they were demonstrated to be predictable.
≡The Electric Light
1879 A.D.
U.S.A.
With a source of energy like electricity, there seemed a chance of having light without flame. A current forced across an air gap can produce a bright spark, and arc lights had been introduced by Davy nearly three-quarters of a century before, but the light was harsh and the danger of fire was great. Edison now tackled the problem of an alternate form of electric lighting.
Electricity passing through a wire warmed it because of the wire's resistance. If the resistance was made great enough by making the wire thin enough, the wire would heat to incandescence. If it did so, however, it would either melt or burn.
To prevent burning, the wire filament would have to be in an evacuated glass bulb. That would also soften the light and lessen the danger of fire to nearly nothing.
That still left the problem of finding a conductor that would not melt.
Edison spent a considerable time experimenting with platinum wire, but platinum was too expensive -- and wouldn't work.
Finally, after thousands of experiments, Edison found what he wanted, and it wasn't a metal at all. He used a scorched cotton thread, which proved to be equivalent of a carbon wire. On October 21, 1879, Edison sent a current through such a filament in an evacuated glass bulb. It burned for 40 continuous hours.
Edison promptly obtained a patent, and on the following New Year's Eve, he illuminated the main street of Menlo Park using his electric light bulbs before a crowd of 3,000.
To make the light bulb useful, Edison had to develop a generating system that would supply electricity as needed and in varying amounts as lights were switched on and off. He accomplished that, too.
The age of electric lighting had come, and the dark of night was on the road to vanishing.
The Edison Effect
1883 A.D.
U.S.A.
Once Edison had invented the electric light, he naturally endeavored to improve it. In particular, he wanted to make the filament last longer. In 1883 he sealed a metal wire into a light bulb near the hot filament. Perhaps he thought this might absorb some of the remaining air in the tube and lessen its destructive effect on the filament.
To Edison's surprise, electricity flowed from the hot filament to the cold wire across the gap that separated them. This is called the Edison effect.
Edison wrote up the effect meticulously and patented it, as a matter of course, but he could think of no use for it. This was his only purely scientific discovery, and he didn't follow it up. The Edison effect proved the basis for the science of electronics that was eventually to come.
╙Popularizing Radio
1916 A.D.
NEW YORK, NEW YORK
Until now, radio operation had been a rather complicated thing that had to be left to radio engineers. In 1916, however, the American radio engineer Edwin Howard Armstrong (1890-1954) worked out a system for lowering the frequency of electromagnetic waves and then amplifying them. He called this a superheterodyne receiver. The addition of such devices to radios made them far easier to use. The turn of a dial was all that was needed to get good reception, or to transfer reception from one wavelength to another. It was only after such devices were widely adopted that radios could be operated by anyone, so that they entered the home and became a vehicle for mass entertainment and information.
Beginnings of Agriculture
8000 B.C.
MESOPOTAMIA
Human beings led a nomadic life. As long as hunting was a major source of food, they had to be prepared to follow migrating herds of animals. Even if they lived on plants and on nonmigrating animals, a tribe lingering in one place too long would consume the available food and have to move elsewhere for fresh foraging.
Even when human beings became herders, they remained nomads. The herds had to be taken to fresh pastures now and then, either because of seasonal changes or because of overgrazing.
About 8000 B.C., however, in the same region where animals were first domesticated, something new arrived, heralding a change greater than any since the first use of fire.
What it amounted to was that plants were domesticated. Somehow it occurred to human beings to plant seeds deliberately, to wait for them to grow, to water them, and to wait for them to ripen while destroying competing plants. Then the plants could be harvested and would serve as food.
It was tedious and back-breaking work, but the net result was that a great deal of food could be obtained, far more than by hunting and gathering, or even herding, since plant life is more copious than animal life.
The coming of herding and agriculture, particularly agriculture, meant that a given area of land could support a larger population than before. There was less starvation, more children survived, and the population increased.
Agriculture began in northern Iraq where wheat and barley grew wild, and it was these that were domesticated. The kernels of grain could be ground into flour that could be stored for months on end without spoiling and could be baked into a tasty and nutritious bread.
Agriculture, for the first time, condemned human beings to a sedentary existence. Once a farm was established, there could be no further wandering. The farmers had to remain with the farm, which was fixed in one place.
A sedentary life had its dangers. As long as human beings hunted and gathered, or even herded, danger could be avoided. If a hungry, marauding tribe approached, intent on taking what food they could find, the tribe already present, if they decided fighting would be too dangerous, could always flee. Farmers could not run, at least not without abandoning their farms and seeing their lifework ruined and themselves faced with starvation. Once the population had increased, thanks to agriculture, they could not possibly find enough food to maintain themselves except by continuing with agriculture -- they had a tiger by the tail.
Farmers therefore had to be prepared to fight at whatever cost, and they gathered together for mutual self-protection. They would find a site on an elevation (so that they could throw missiles downward, whereas an enemy would have to throw them upward, with lesser effect) and with a secure water supply (you can go without food for a period of time but not without water). There they would build houses and surround them with a protective wall. The result would be a city, and the inhabitants would be city-dwellers, or citizens.
In northern Iraq, for instance, near the site where herding and agriculture developed, are the remains of a very ancient city, founded perhaps in 8000 B.C., at a site called Jarmo. It is a low mound into which, beginning in 1948, the American archaeologist Robert J. Braidwood dug carefully. He found the remains of houses built with thin walls of packed mud and divided into small rooms. The city may have held no more than 100 to 300 people, but cities grew rapidly larger.
Agriculture made it possible for farmers to produce more food than their own families needed. This meant that people could do things other than farming -- for example, engage in artisanry or art -- and trade their products for some of a farmer's excess food. For the first time, human beings could find time to think of something other than the next meal. In addition, living in close quarters in a city, they could interact easily, and the innovations and ideas of one could be rapidly transmitted to the others. As a result, the coming of agriculture and of cities meant the coming also of a new and more complex way of life, which we call civilization (from a Latin word for "city-dweller"). The civilized area was small at first, but it spread outward steadily until it now occupies virtually the entire world.
-Mass to Energy
1905 A.D.
GERMANY
Another consequence of Einstein's theory of special relativity is that mass must be viewed as a highly concentrated form of energy. Einstein's equation representing this is the famous e = mc2, where e is energy, m is mass, and c is the speed of light. The speed of light is so huge that to square it and multiply it by even a small amount of mass is to represent a large amount of energy (1 gram of mass equals 900 billion billion ergs of energy).
Whenever any process gives off energy, it loses a little mass; when it absorbs energy, it gains a little mass. The amount of mass lost or gained under ordinary conditions is so minute it had never been detected. That is why Lavoisier could consider mass conserved independently of energy and Helmholtz could consider energy conserved independently of mass.
With the study of radioactivity, much larger energy changes per unit mass were involved, as Pierre Curie had found. Mass-energy equivalence could then be measured and was found to be precisely as Einstein's theory required it to be. The law of conservation of energy was thus extended and made more precise by the inclusion of mass as one more form of energy.
The law of conservation of mass became obsolete, or rather, was included in what is sometimes known as the law of conservation of mass-energy.
ÉBose-Einstein Statistics
1924 A.D.
ITALY
In 1924 the Indian physicist Satyendra Nath Bose (1894-1974) worked out a statistical method of handling certain subatomic particles. Einstein was enthusiastic about this and generalized Bose's work the next year.
The resulting Bose-Einstein statistics may be used with any of a group of subatomic particles called bosons in Bose's honor. The best- known example of a boson is the photon.
,Einsteinium and Fermium
1952 A.D.
BERKELEY, CALIFORNIA
Seaborg and his team continued to make ever more complex atoms, and as the atoms were made, they were bombarded with small atomic nuclei.
Some of these stuck to the complex nucleus of the atoms being bombarded so that still newer and more complex atoms were formed.
In 1952, however, complex atoms were formed in a different way. The ravening energies of the fusion bomb explosion in the Pacific had driven nuclei together and formed atoms even more complex than californium (element number 98), which was at the time the most complex known. As a result, elements 99 and 100 were formed and detected. They were eventually named, respectively, einsteinium and fermium in honor of Albert Einstein and Enrico Fermi, who had died in the months preceding laboratory study of the elements.
_
Special Relativity
1905 A.D.
BERN, SWITZERLAND
The Michelson-Morley experiment of 1887 was still troublesome. The work of Irish physicist George Francis FitzGerald (1851-1901) and Dutch physicist Hendrik Antoon Lorentz (1853-1928) in 1895 got rid of the difficulty in a way, but the notion of decrease of distance and increase of mass seemed to hang in the air without an overall physical theory for support.
The German-born physicist Albert Einstein (1879-1955) supplied that in 1905. He began with the assumption that the speed of light in a vacuum would always be the same, regardless of the motion of the light source relative to the observer. This was what Michelson and Morley had observed, but Einstein maintained that he was unaware of the Michelson-Morley results when he worked out his theory.
From this assumption it was possible to deduce length contraction and mass increase with velocity. It was also possible to deduce that the speed of light in a vacuum was an absolute speed limit and that the rate of time-flow would decrease with velocity.
This is Einstein's theory of special relativity. It is relativity, because velocity has meaning only as relative to an observer, there being no such thing as "absolute rest" against which an "absolute motion" can be measured. There is also no such thing as "absolute space" or "absolute time," since both depend on velocity and therefore have meaning only relative to the viewer. Nevertheless, despite this absence of absolutes, the laws of physics still held for all "frames of reference." In particular, British mathematician James Clerk Maxwell's equations in 1865 still held, though the much older and more revered laws of motion as worked out by English scientist Isaac Newton had to be modified. The theory is special, because it confines itself to the special case of objects that are moving at constant velocity. Under those conditions, the theory does not take into account the effect of gravitational interactions, which are everywhere present and which force accelerations on motion.
Einstein's view of the Universe seemed to go against common sense, but that was only because the average person deals with a Universe of small distances and small velocities. Under those conditions, Newton's theories hold almost perfectly. In fact, Einstein's equations reduce to Newton's under such conditions. However, where large distances and large velocities are involved, Einstein's equations hold and Newton's do not.
In the eight decades since special relativity was advanced, endless tests and observations have upheld it completely. No divergences between reality and the Einsteinian view have been found.
pElectrocardiogram
1903 A.D.
DENMARK
That muscles gave rise to tiny electric potentials had been known since Italian anatomist Luigi Galvani's (1737-1798) time. It seemed natural to suppose, then, that the heart, beating rhythmically, might give rise to rhythmic electric potentials. Perhaps a departure from the natural rhythm might be used to diagnose pathological conditions before they could be discovered in any other way. The problem was to detect the small currents with sufficient accuracy.
In 1903 a Dutch physiologist, Willem Einthoven (1860-1927), developed the first string galvanometer. This consisted of a delicate conducting thread stretched across a magnetic field. A current flowing through the thread would cause it to deviate at right angles to the direction of the magnetic lines of force. The delicacy of the device was sufficient to make it possible to record the varying electrical potentials of the heart.
The result was an electrocardiogram. The abbreviation is EKG because in German "cardio" is spelled with a k. For the development of electrocardiography, Einthoven was awarded the Nobel Prize for medicine and physiology in 1924.
^Electric Motors
1831 A.D.
NEW JERSEY
American physicist Joseph Henry (1797-1878) discovered electrical induction in 1823 independently of English physicist Michael Faraday (1791-1867), but the latter published first by a few months and gets the credit. Henry went on to study the reverse process. If the rotary motion of a copper wheel cutting across magnetic lines of force can induce an electric current, then an electric current ought to be able to produce a rotary motion.
In essence, Faraday had already shown this in a simple way), but in 1831 Henry devised a much more practical version of such a machine, one in which a wheel would turn if electric current was supplied. This was the first practical electric motor (from a Latin word meaning "to move").
The importance of the motor cannot be overemphasized. A motor can be made as large or as small as desired. It can be run by electricity brought to it over a distance of many miles. Most important of all, it can (unlike a steam engine) be started in a moment and stopped in a moment.
The supply of cheap, abundant electricity made possible by Faraday's discovery of the generator (once it was sufficiently improved) would have been useless without some means of putting it conveniently to work. Henry's motor (once it was sufficiently improved) did that, so that between them, Faraday and Henry ushered in the age of electricity.
9 Electric Generators
1831 A.D.
ENGLAND
Since Orsted had shown that an electric current could produce a magnetic effect, it had seemed to Faraday that there ought to be some way of showing that the reverse was also true, that a magnet could induce an electric current.
To do this, Faraday made use of an iron ring. In 1831, he wound a coil of wire around one portion of the iron ring and attached it to a battery. The circuit could be opened or closed by a key. If he closed the circuit, current would flow, and a magnetic field would be set up and concentrated in the iron ring.
Suppose, then, that a second coil was wrapped around another segment of the iron ring and connected to a galvanometer. The magnetic field set up in the iron ring might produce a current in this second coil, and the galvanometer would record its presence.
The experiment worked. Faraday had devised the first electrical transformer and had discovered electromagnetic induction. However, it did not work as he had expected. There was no continuous electric current to match the continuous presence of the magnetic field. Instead, there was a momentary flash of current, marked by a jerk of the galvanometer's needle when he closed the circuit, and a second flash, in the opposite direction, when he opened the circuit.
Faraday explained this by means of the lines of force that he had visualized. When a circuit was closed and electricity was set to flowing, magnetic lines of force sprang outward and crossed the second coil, inducing an electric current. When the circuit was opened again, the magnetic lines of force collapsed inward and crossed the second coil again, inducing an electric current in the opposite direction. When the magnetic lines remained in place because the current in the first coil was flowing steadily, no lines crossed the second coil in either direction and no current was induced in it.
Faraday went on to devise a way of having metal cut across the lines of force continually. He turned a copper wheel so that its rim passed between the poles of a permanent horseshoe magnet. As long as the copper wheel turned, its rim continually cut through magnetic lines of force and an electric current flowed continually in the wheel. That current could be led off and made to do work. Faraday had thus devised the first electric generator.
Until then, electric current had been produced only by batteries, which meant that the electricity was obtained by burning metals such as zinc. This meant that electricity was expensive and limited in quantity.
The turning of the copper wheel to cut across the magnetic lines of force took considerable effort, and it was this energy that was turned into electricity. If one had to turn the wheel by muscle power, little electricity could be obtained. However, the wheel could be and eventually was driven by steam power, which meant that the electricity was formed from burning fuel or from some other copious source of energy such as falling water or blowing wind.
Eventually, when the electric generator was sufficiently improved, electricity could be generated cheaply and in any quantity desired.
Electricity Produces Motion
1821 A.D.
ENGLAND
The discovery of electromagnetism continued to provoke a surge of experimentation. The English physicist Michael Faraday (1791-1867) set up an electrical circuit that included two wires and two magnets. In one case, the wire was fixed and the magnet was movable. In the other, the magnet was fixed and the wire was movable. When the current passed through the wire, the movable wire revolved about the fixed magnet and the movable magnet revolved about the fixed wire.
In this way, Faraday demonstrated for the first time that electrical forces could produce motion.
This experiment led Faraday to consider magnetism a field that stretched out from its point of origin, weakening with distance. One could draw imaginary lines in the field, connecting all points of equal magnetic intensity, and call these lines of force. Around a wire with a current flowing through it, the lines of force were concentric circles, and it was this that caused the circular movement.
Here began the conception that today is very nearly central to physics: that the Universe consists of fields, of which particles are the origin. Lines of force, first visualized by Faraday (who had no mathematics but who had a terrific grasp of what must be) are of the utmost importance to the physics of today.
ΣElectronic Rectifier
1904 A.D.
ENGLAND
A British electrical engineer, John Ambrose Fleming (1849-1945), studied the Edison effect on a hot filament and a cold plate enclosed in an evacuated glass vessel and separated by a gap. He noted that the electric current only flowed across the gap if the hot filament was the negative electrode (the cathode) and the cold plate was the positive electrode (the anode). In that case, electrons poured into the hot filament and were driven off by the heat. If the current was reversed and electrons poured into the cold plate, there was insufficient energy to send them flying outward.
If an alternating current was sent through the vessel, the anode and cathode changed place many times a second, and there was a spurt of electrons each time the filament was a cathode but nothing when it was an anode. The current went in as an alternating current but came flowing out in only one direction, as a direct current, even if the flow was in little gushes.
In this way, the vessel containing the filament and plate acted as an electronic rectifier, because it let electricity through in only one direction. Fleming called it a valve, which is descriptive. In the United States, however, it was for some reason called a tube, which is not descriptive. Because it contains two electrodes, it can also be called a diode.
Fleming's rectifier was the first of a long line of radio tubes (so called because they became most familiar to the general public in radios) that made electronic devices work.
3Electromechanical Calculator
1880 A.D.
U.S.A.
The American census was growing more and more elaborate. There were more and more people, and more and more questions were being asked of each person. The information gathered was so voluminous that it took literally years to sort it.
An American inventor, Herman Hollerith (1860-1929), who worked for the census, thought there might be a better way of handling the data, and beginning in 1880, he set about the task.
He made use of punch cards after the fashion of Jacquard and Babbage. Each card could be punched to represent data gathered in the census: holes in appropriate places could represent sex, age, occupation, and so on.
In order to add up and analyze all this information, the cards were placed on a stand and a metal device was pressed down against them. The device had many pins, which would be stopped by the cardboard. Wherever there was a hole, however, a pin would go through and reach a pool of mercury underneath.
Electricity would pass through that pin and control the pointer on a dial. As the punch cards were sent rapidly through the machine, it was only necessary for people to record the numbers indicated on the dial.
What made all the difference between Hollerith and Babbage was that Hollerith had the use of electricity. He had developed an electromechanical calculator, and not merely a mechanical one.
Eventually, Hollerith founded a company devoted to making all kinds of machines that could handle and analyze information. That company developed into the International Business Machines Corporation, usually known simply as IBM.
?The Electron Microscope
1937 A.D.
CANADA
The first electron microscope had been constructed by Ruska. It was not till 1937, however, that an electron microscope was constructed that could clearly outperform the best optical microscopes. The Canadian physicist James Hillier (b. 1915) accomplished this feat. His microscope could magnify seven thousand times, whereas the best optical microscope could only manage a magnification of two thousand times.
Eventually, Hillier and others devised electron microscopes with still further capabilities, until magnifications of two million times became possible.
µElectroencephalography
1929 A.D.
GERMANY
Einthoven had developed methods for detecting the rise and fall of electric potentials involved in the heartbeat and devised the electrocardiogram.
The German psychiatrist Hans Berger (1873-1941) thought the same might be done for the brain. During the 1920s he devised a system of electrodes that, when applied to the skull and connected to an oscillograph, would give a recording of the rhythmic shifting of electric potentials commonly called brain waves.
In 1929 he published his results, describing alpha waves and beta waves. In this way, electroencephalography (Greek for "the writing of brain electricity") was developed. It offered a technique for the diagnosis of such serious brain disorders as tumors and epilepsy.
cLaws of Electrolysis
1832 A.D.
ENGLAND
In his youth Faraday had worked under Davy and carried on the elder's work in electrochemistry. The method whereby Davy had liberated a number of new metals, by passing an electric current through molten compounds of those metals, Faraday named electrolysis (from Greek words meaning "to loosen by electricity").
Faraday named a liquid or a solution that could conduct electricity an electrolyte. The metal rods inserted into the liquid or solution he called electrodes (from Greek words meaning "the road of electricity"). The positively charged electrode he called the anode (high road) and the negatively charged electrode he called the cathode (low road). This likened the flow of electricity to the flow of water from the height of the anode to the depth of the cathode, following Franklin's guess that electricity flowed from positive to negative. (In fact, that turned out to be wrong, however, and electricity flowed from the negative electrode to the positive.)
All these names were suggested to Faraday by the British scholar William Whewell (1794-1866), who also coined the word scientist in the next decade.
In 1832 Faraday announced what are now called his laws of electrolysis. They are: 1. The mass of substance liberated at an electrode during electrolysis is proportional to the quantity of electricity driven through the solution.
2. The mass liberated by a given quantity of electricity is proportional to the atomic weight of the element liberated and inversely proportional to the combining power of the element -- that is, to the number of atoms that one atom of the element will combine with.
xElevator
1852 A.D.
U.S.A.
As cities grow more crowded, they may spread out in area, or divide the available room into smaller and smaller living quarters, or build higher and higher structures.
High structures were originally built of stone, as the strongest available material, but the higher the building, the thicker the stone had to be at the bottom to support the structure and the less room available for living quarters.
Reinforced concrete made higher structures possible, and steel beams would in time be even better.
Yet with the best materials and the cleverest designs, a tall building is useless if there is no way but slow climbing to lift oneself to the top floors.
In 1852 an American inventor, Elisha Graves Otis (1811-1861), built the first mechanical elevator with an adequate safety guard, one that would keep it from falling even if the cable holding it were severed completely. In 1854 Otis demonstrated the workability of the device by having himself raised to a considerable height and then having the cable cut. He descended safely.
It was the elevator more than anything else that made possible the shape of cities to come.
Electromagnets
1823 A.D.
ENGLAND
Three years earlier, Ampère had shown that a wire helix (or solenoid, from a Greek word meaning "pipelike," because such a helix looks like a pipe with its walls made of turns of wire) acts like a bar magnet when electricity flows through the wires.
In 1823 an English physicist, William Sturgeon (1783-1850), placed an iron bar within a solenoid of 18 turns. He found that the iron seemed to concentrate the magnetic field and make it stronger.
Sturgeon varnished the iron bar to insulate it and keep it from short- circuiting the wires. He used one that was bent into the shape of a horseshoe.
His device would lift nine pounds -- 20 times its own weight -- while the current was running. When the current was turned off, the magnetic properties vanished. Sturgeon had invented the electromagnet.
It was quickly improved upon by the American physicist Joseph Henry (1797-1878), who in 1829 wrapped insulated wire around an iron core. This meant that many more turns of wire could be wrapped about the core, since crisscrossing them would not produce a short circuit. The more turns of wire, the stronger the magnetic field when the current was running. By 1831, using the current from an ordinary battery, Henry could make an electromagnet lift a ton of iron.
Better Tissue Transplants
1949 A.D.
ENGLAND
Snell had shown the genetic basis of the intolerance for foreign proteins that made tissue transplantation difficult.
It occurred to an English anatomist, Peter Brian Medawar (1915-1987), that embryos might not yet have developed an immunological system capable of rejecting foreign proteins. And in fact, when he inoculated mice embryos with tissue cells from another strain, he found that rejection did not take place.
Furthermore, when such embryos entered independent life and could form antibodies, they no longer treated cells from the other strain as foreign proteins.
By 1949 Medawar had shown how this technique might lead to reducing the difficulties of tissue transplantation. For this he received a share of the Nobel Prize for medicine and physiology in 1960.
├Embryo Photograph
1973 A.D.
STOCKHOLM, SWEDEN
People have always been able to see much of the world around them, and even -- by examining dead people -- to observe the interior structure of the human body.
But it is only recently that optical and surgical equipment has been developed that allow us to watch the interior of the body in action. In this picture we see one of the most amazing aspects of life, the development of a human being in its mother's womb.
Because human beings are born all the time, we sometimes forget how amazing this process is.
The life process starts when two half-cells -- one half from the mother and the other half from the father -- join together into one full-cell.
Though this cell is so tiny you couldn't see it without a microscope, it contains an astonishing amount of information. The entire design for a person, a being more complicated than anything people have ever designed, is contained in just the smallest part of the cell. This information chain (called "DNA," for deoxyribonucleic acid) is so small that scientists can't see it with regular optical microscopes, so they use powerful electron microscopes. If computer designers could easily duplicate this information chain, they could build computers far more powerful than anything available today.
But this original cell not only contains all the information necessary to design a human body, but also has the ability to build the body. In other words, this little cell is not only like a giant library, but also like a factory that can reproduce itself!
Over nine months in the womb, the body grows. Within several weeks you can begin to recognize the head, then later you can see the arms and feet, and finally -- at birth -- the full body.
vEmbryology
1759 A.D.
GERMANY
It was customary at this time to think that seeds and eggs (or pollen and sperm) had miniature organisms in them that simply grew. Some even thought that an organism within an egg might have eggs of its own with ultraminiature organisms within and still smaller eggs -- and so on.
In 1759, however, the German physiologist Kaspar Friedrich Wolff (1734-1794) showed that specialized organs developed out of unspecialized tissue. Thus the tip of a growing shoot consists of undifferentiated and generalized tissue. As it grows, however, specialization develops, and some bits of tissue develop into flowers, while other bits, originally undistinguishable, develop into leaves.
The same principle could, and did, apply to animals, so that the idea of miniature organisms in eggs disappeared. Wolff is considered another of the founders of modern embryology, in consequence.
-Encke's Comet
1818 A.D.
GERMANY
Since Halley had predicted the return of Halley's comet, no other cometary orbit had been worked out, and no other comet's return had been predicted.
In 1818, however, the German astronomer Johann Franz Encke (1791-1865) worked out the orbit of a comet that had been observed the year before by the French astronomer Jean-Louis Pons (1761-1831). The comet has been called Encke's comet ever since, the name going to the orbit-establisher rather than to the discoverer.
Encke's comet, the second to have its orbit established, returned to the neighborhood of the Sun every three and a third years. It was the first short-period comet known and, indeed, to this day no comet has been discovered with a smaller orbit. Encke's comet was the first to be visible throughout its orbit, and this went far to decrease the mystery of comets. It is, of course, a very dim comet, since repeated approaches to the Sun have drained it of the material that goes into the forming of the tail. Nowadays it has just a trace of the fuzziness that reveals it to be a comet.
fEndorphins
1975 A.D.
WORLD
It was discovered in 1975 that the nervous system gives rise to compounds that alleviate pain. These consist of short chains of amino acids that seem to interact with the pain-receptors. Presumably, morphine and similar opiates work by mimicking the action of these substances, which are now called endorphins. The first part of the name indicates that they are "endogenously formed;" that is, formed within the human body. The second part of the name indicates their morphinelike action.
Endorphins may someday be used in pain control without the addictive qualities and other side effects of opiates.
£Energy of Activation
1889 A.D.
WORLD
It was the experience of early humans that fires were hard to start but that once started, they kept right on going with no further trouble as long as they were fed fuel.
This is also true of many chemical reactions. Nevertheless, a reaction that ordinarily yields energy when it proceeds will not take place spontaneously until energy is added to it. The reaction has to be activated, by breaking molecules apart, perhaps, so that individual atoms or molecular fragments can react with each other more freely. The energy required is called the energy of activation.
Once the reaction starts, it yields energy that can be used to activate neighboring parts of the initial substance. Thus, when you heat a hydrogen and oxygen mixture and a small amount begins to react, the energy it produces will cause a wave of reaction to spread to other parts of the mixture so rapidly that it explodes. This is a chain reaction, since each step leads to the next, as each link in a chain leads to the next.
Arrhenius analyzed the energy activation concept systematically in 1889 and brought about new understanding of chemical reactions, of chain reactions, and of explosions.
ÇBetter Gasoline
1921 A.D.
U.S.A.
One of the difficulties in automotive engineering was that of getting the gasoline vapors to burn smoothly within the cylinder. If they burned too rapidly, there was too great an explosion and a resulting "knock" in the engine. This was hard on the engine, disturbing to the ear, and wasted energy.
In 1921, however, the American chemist Thomas Midgley, Jr. (1889-1944) discovered that if the compond tetraethyl lead was added to the gasoline, it inhibited the burning just enough to prevent knock. It was an antiknock compound. From that time on, one could speak of "ethyl gas" or of "leaded gasoline." A bromine compound was also added to the gasoline, to prevent accumulation of lead in the cylinder. It meant that the relatively volatile compound lead bromide was formed and discharged through the exhaust. This added another factor to the air pollution produced by automobiles.
âThe First Electronic Computer
1946 A.D.
UNIVERSITY OF PENNSYLVANIA
American electrical engineer Vaannevar Bush (1890-1974) had devised a computer that made use of radio tubes as electronic switches in addition to the usual mechanical parts.
The obvious next step was to make an entirely electronic computer, with no moving mechanical parts at all. This was done by the American engineers John William Mauchly (1907-1980) and John Presper Eckart, Jr. (b. 1919), who devised the first practical electronic digital computer in 1946. It was called ENIAC (electronic numerical integrator and computer).
It was an enormous, energy-guzzling device, weighing 30 tons and taking up 1,500 square feet of space. Though it was a wonder of its time, ENIAC was retired some nine years after it had been set up. It was by then hopelessly obsolete, for its descendants were growing steadily smaller, cheaper, more efficient, and much more capable.
gSilent Spring
1962 A.D.
U.S.A.
It isn't often that a book intended for the general public makes the world aware of a scientific problem, but it happened in 1962, when Silent Spring, by the American biologist Rachel Louise Carson (1907-1964), was published. Her account of the effect of indiscriminate use of pesticides on the environment was riveting. She described the possibility that pesticides would kill birds, for instance, to the point where spring would finally arrive without birdsong.
The book was largely responsible for a sudden increase in awareness of environmental dangers on the part of a large segment of the public.
%Adrenaline
1898 A.D.
ENGLAND
What we now call the adrenal glands (from Latin words meaning "at the kidney") are small lumps of tissue above each kidney. They first came into prominence in 1855, when a British physician, Thomas Addison (1793-1860), showed that the deterioration of the adrenal glands gave rise to a serious condition (known as Addison's disease to this day).
In 1894 a British physiologist, Edward Albert Sharpey-Schafer (1850-1935), showed that a substance extracted from the adrenals would raise the blood pressure if injected into an animal's bloodstream.
An American pharmacologist, John Jacob Abel (1857-1938), was able to study this substance in 1898, and he named it epinephrine (from Greek words meaning "above the kidney"). Three years later, a Japanese chemist, Jokichi Takamine (1854-1922), working in the United States, isolated the substance in pure, crystalline form. He called it adrenaline. Both names are still used.
Actually epinephrine/adrenaline was the first hormone to be isolated, but the hormone concept had not yet been elaborated.
The Formation of the Earth
1749 A.D.
FRANCE
Buffon was daring enough to think that there might be some natural cause, one not involving God, for Earth's coming into existence. In the first volume of his Natural History, he suggested that Earth (and presumably the other planets) had been formed by the collision of the Sun with another massive body (which he called a comet).
Buffon then tried to decide how old the Earth was by calculating how many years it would take an object the size of the Earth to cool from the temperature of the Sun to the temperature of the Earth today. This, he eventually announced, could be as much as 75,000 years; Earth had grown cool enough to support life about 40,000 years before, and it would exist for another 90,000 years before becoming too cold to support life any longer.
To be sure, Buffon's estimates of these values were much smaller than the time periods scientists were to accept later on, but he was the first important scientist to suggest that the Earth might be much older than the 6,000 years allotted it by Ussher.
zCircling the Moon
1968 A.D.
CAPE CANAVERAL, FLORIDA
On September 17, 1968, the Soviet probe Zond 5, with no crew aboard, circumnavigated the Moon. On December 24, 1968, the American probe Apollo 8, with three astronauts aboard -- Frank Borman (b. 1928), James A. Lovell, Jr. (b. 1928), and William A. Anders (b. 1933) -- circumnavigated the Moon 10 times. The stage was finally set for a lunar landing.
┤Earthquakes
1760 A.D.
ENGLAND
Human beings have always known about earthquakes from sad and frightening experience. What they didn't know was the cause. Early theories attributed them to the restlessness of gods or demons imprisoned underground.
The ancient Greek philosophers, in search of a more rational cause, supposed that there might be pent-up air underground, which occasionally, in its attempt to escape, shook the earth.
The Lisbon earthquake of 1755 forced serious thinking on the matter. In 1760, the English physicist John Michell (1724-1793) noted that earthquakes frequently appeared in volcanic areas. He felt that underground water might be boiled by volcanic heat at times, and that it was the imprisoned steam that caused earthquakes.
Furthermore, he said, the earthquakes set up waves that traveled through the Earth at some measurable speed. If the time at which waves reached different points were recorded, the point of origin (or epicenter) of the earthquake could be determined. Epicenters, he suggested, could exist in the rocks beneath the sea, and it was one of these that had destroyed Lisbon.
All of Michell's ideas were pretty sound, so that he is known as the founder of seismology.
1Climatic Cycles
1920 A.D.
YUGOSLAVIA
Weather is so erratic that even the most modern devices have trouble predicting it long in advance. Nevertheless, very general cycles of weather may exist, and these may explain the periodic ice ages that have occurred in the last million years of Earth's history.
In 1920 the Yugoslavian physicist Milutin Milankovich (1879-1958) suggested that astronomic factors played a part. Slow oscillations in the eccentricity of Earth's orbit and in the tilting of the Earth's axis, together with the precession of that axis, seemed to suggest a 40,000-year cycle, which could be divided into a Great Spring, Great Summer, Great Autumn, and Great Winter, each about 10,000 years long.
Milankovich's suggestion was ignored at the time, but after more than half a century, it came to be considered seriously.
8A Female Sex Hormone
1929 A.D.
ST. LOUIS, MISSOURI
Males and females of the same species develop differently. The sex organs arise out of similar structures, but though the penis and the clitoris are homologous, they are very different in appearance and function. The male grows a larger larynx, the female larger breasts, the subcutaneous fat distribution and the hair pattern are different in the two sexes, and so on.
It wasn't very difficult to suppose that hormones were involved and that, like the organs whose development they controlled, they were similar but different in the two sexes.
In 1929 the American biochemist Edward Adelbert Doisy (1893-1986) and, working independently, the German chemist Adolf Friedrich Butenandt (b. 1903) isolated a female sex hormone, which came to be called estrone, from the Greek word for "sexual heat."
àHuman Breeding
1883 A.D.
GREAT BRITAIN
From earliest times, human beings have bred their animals in such a way as to enhance desired characteristics, so that larger and speedier horses were obtained, sheep with more wool, cows with more milk, hens with more eggs. It must have occurred to many that similar tactics might improve the human species.
One who thought this was the British anthropologist Francis Galton (1822-1911), a first cousin of Charles Darwin. In 1883 he coined the term eugenics (from Greek words meaning "good breeding") for the study of the improvement of human qualities by careful breeding.
However, eugenics is not easy to put into practice. In the first place, one can't guide human breeding with quite the ease that one can guide the breeding of animals. Second, we are not as sure of what we want in human beings as we are in the case of animals. Third, when Mendel's discovery of recessive traits was understood, it came to be seen that it was hard to get rid of what one might consider undesirable characteristics. Fourth, the loudest supporters of eugenics were unsavory characters who wished to place it at the service of prejudice and racism.
^Europe
1990 A.D.
EUROPE
On ancient Assyrian monuments are some of the earliest references to Europe and Asia. In contrast to "Asu" (Asia), which means "Land of the rising sun," "Ereb" (Europe) means "land of darkness," or "land of the setting sun."
Despite that rather dismal description, Europe has actually had many bright days in science, art and government.
Europe is the land area located north of the Mediterranean Sea and west of the Ural Mountains in Soviet Union. Its culture owes much of its character to two major forces: the Greeks and the Romans.
From the sixth and fourth centuries B.C., the seagoing Greeks spread their arts and sciences throughout the Mediterranean basin. Then the Romans adopted it and spread it to places the Greeks had barely touched. But the Romans also added much, including their own versatile language, Latin, and their expertise in government and law. Even with the fall of the Roman Empire, much Roman civilization survived through the Roman Catholic Church.
Even today, much art and science is built on Greek foundations, and much law and government is based on the Roman model.
╬ Europium
1901 A.D.
FRANCE
Eleven rare earth elements were now known, but that did not exhaust the list.
The French chemist Eugène-Anatole Demarcay (1852-1903) detected a 12th, which he named europium in honor of Europe.
bCritics of Evolution
1859 A.D.
LONDON, ENGLAND
Darwin's theory of evolution has a simplicity that is appealing. One of his contemporaries summarized it in a single phrase: Evolution, he said, is the "survival of the fittest."
The theory is widely accepted by scientists today, and that acceptance is reflected by those who report on science, such as Isaac Asimov and other top writers. However, many object to evolution on religious grounds, and some on scientific grounds.
Though it is the minority view in scientific circles, critics of evolution raise some interesting points. Here are a few:
-- It is difficult (some believe to the point of impossibility) for life to arise from non-life, even if all necessary ingredients were mixed in abundance.
Though some doubt he meant it, Darwin apparently did not believe life developed from non-life. He attributed the first living thing to a "Creator." Nevertheless, life developing from non-life has become part of evolutionary theory.
English scientist Thomas Huxley suggested time and chance caused the first life. He reportedly said six monkeys typing mindlessly for millions of years could write all the books in the British Museum. By the same random method, he said, simple life could be created.
But in his recent book, "The Philosophical Scientists," British scientist David Foster says this is unlikely: "Allowing Huxley all the monkeys there have ever been, typing for all the time there has ever been, there would be a shortfall ratio of more than one hundred million millions, and that only relates to the chance of typing one line of one book in the British Museum."
-- That evolution causes minor changes is virtually beyond dispute, but some scientists (including Darwin's contemporary, French anatomist Georges Cuvier) don't believe it can cause major changes. This is because living beings are complex mechanisms and a change to one part of the mechanism affects other parts.
Compare life to an automobile. You can change the paint or flare the fenders (somewhat) without problem, but, for example, if you change the size of a piston, even a bit, other parts of the engine must be changed to accomodate it. That such coordinated changes should take place by chance at the same time in the same living being strikes some as extremely unlikely.
-- Darwin said occasional small changes make some animals better able to survive. Conversely, detrimental changes make them less likely to survive. But some anatomical changes would appear detrimental unless in fully functioning form.
Consider the bat, whose wing bones are, essentially, its fingers. If bats evolved from non-flying creatures, wouldn't the increasing length of these animals' fingers make them very clumsy and likely to be somebody's lunch long before the fingers became wings?
-- The fossil record doesn't show gradual changes. Darwin said big biological changes result from eons of little changes. Some in his day, such as anatomist Sir Richard Owen (who coined the word "dinosaur"), said the fossils didn't show little changes adding up to big changes. Many believed more study would close these gaps, but it hasn't.
Some scientists have proposed a theory called "punctuated evolution," in which species remain stable for ages, then isolated groups rapidly change from environmental pressure. Rapid change means there would be few intermediate species, which would explain the gaps in the fossil record. However, it also requires squeezing a vast number of changes into a relatively short time, which strikes some, including traditional Darwinists, as unlikely. -- Studies show that life forms that look similar are often genetically similar; apes and humans, for example. However, critics say, genetic material does not show the progression that evolution demands.
For example, most scientists believe jawless fish evolved into boney fish, which evolved into amphibians, then to reptiles and finally to mammals. This means genetic material should become increasingly different as you move from jawless fish to mammals. But it doesn't, they say. In fact the genetic material of boney fish, amphibians, reptiles and mammals is about equally different from jawless fish -- and from each other.
In his book, "Evolution: A Theory in Crisis," Australian scientist Dr. Michael Denton said, "There is little doubt that if this molecular evidence had been available one century ago it would have been seized upon with devastating effect by the opponents of evolutionary theory like Agassiz and Owen, and the idea of organic evolution might never have been accepted."
While the critics of evolution hold a minority view, their objections suggest that the question is not fully resolved.
╓Evolution and Mutation
1937 A.D.
U.S.A.
Darwin had advanced the theory of evolution by natural selection a century before. He assumed that selection took place because in every generation there were small variations among the offspring of a particular species. How those variations arose, he didn't know.
Soon after Darwin, Mendel had developed the laws of genetics, and some decades later, De Vries had shown the existence of mutations.
It seemed possible that mutations provided the variations that allowed natural selection to function as a mechanism for producing evolutionary changes. The exact rationale of this was not quite understood, however.
In 1937 the Russian-born American geneticist Theodosius Dobzhansky (1900-1975), who worked with fruit flies after the fashion of Morgan, published a book entitled Genetics and the Origin of Species in which mutation and evolution were neatly joined together. As a result, evolution was understood on a molecular level as well as on an organismic level.
ÆExpansion of the Universe
1922 A.D.
RUSSIA
Five years earlier, Sitter had suggested that Einstein's equations of general relativity implied a spontaneously expanding Universe. Sitter's work, however, applied to a Universe empty of matter.
In 1922 the Russian mathematician Alexander Alexandrovich Friedmann (1888-1925) went further. Solving the equations for a Universe containing mass, he showed that it too would naturally expand.
│Exploding Galaxies
1955 A.D.
MOSCOW, USSR
Radio astronomy continued to show its practitioners that it could reveal information about the Universe not readily obtainable (if at all) by ordinary optical observations.
A radio source in Cygnus was unusually strong, and optical investigation of the region revealed a peculiarly shaped galaxy that looked rather like two galaxies undergoing a collision.
The Soviet astronomer Viktor Amazaspovich Ambartsumian (b. 1908) examined the nature of the radio source closely and suggested that it was really a galaxy in a state of vast explosion. That idea was borne out by later work.
This was another example of what are now known as active galaxies, in which events releasing enormous energies are taking place at the core. Whereas under optical observation, the Universe seemed to be serene and peaceful (except for the occasional novas and supernovas), radio astronomy began to show that it was a surprisingly violent place.
Experimental Psychology
1872 A.D.
GERMANY
It might seem that psychology is one science that we would know as a matter of course. We know how we think, what our motivations and emotions are, and, perhaps, feel that others are like ourselves in these respects. However, being sure we know something is no substitute for observation and measurement.
It seemed to a German psychologist, Wilhelm Wundt (1832-1920), that there were facets of human behavior that could be profitably measured. There was, for instance, the manner in which the human brain handled sense impressions. He thus initiated experimental psychology, writing a textbook on the subject in 1872. He went on in later years to establish the first laboratory devoted to experimental psychology and the first journal devoted to publishing findings on the subject.
ÅExtinction of the Dinosaurs
1979 A.D.
ITALY
In 1979 the American scientist Walter Alvarez was trying to establish sedimentation rates in old sedimentary rocks in Italy. To do that, he made use of neutron-activation techniques that allowed him to determine with great precision the quantities of various rare elements present in the rocks.
He found to his surprise that a certain narrow layer of the rock contained some 25 times as much of the rare metal iridium as there was above and below it. The narrow layer that contained the iridium was 65 million years old and was therefore right at the boundary where the Mesozoic era yields to the Cenozoic era. At that boundary, dinosaurs and many other species of plants and animals had become extinct with surprising suddenness.
For years scientists had puzzled over that extinction and a variety of explanations had been offered, none of which had proved really satisfactory. Now it seemed to Alvarez that the excess of iridium couldn't be a coincidence. It had to have some connection with the "great dying," and it could only have come from some external body. Most of Earth's own iridium was in its iron core, so that the surface rocks were extremely short of it. A meteor, or even a comet, would be far richer in iridium than Earth's crust is.
Alvarez postulated, therefore, that a large asteroid or comet, several miles across, had struck Earth 65 million years ago, producing volcanic eruptions, tidal waves, fires, and so on. In addition, it may have splashed so much dust into the upper atmosphere that the radiation of the Sun was cut off for an extended period of time. All these varieties of disaster could have brought about enormous extinctions. (In fact, the litany of disaster makes it hard to see how any life at all could survive.) This explanation for the extinction of the dinosaurs was met with considerable skepticism at first, but the evidence has been piling up since, and many now accept it.
úContact Lenses
1954 A.D.
GERMANY
For some six centuries, people who were nearsighted, farsighted, or astigmatic had worn spectacles, or eyeglasses, to correct their vision.
Eyeglasses, however, are a noticeable adjunct that call attention to a physical shortcoming. Furthermore, the myth arose that men who wore glasses were effeminate and that women who wore them were ugly. (The movies, in particular, helped propagate these mischievous ideas.) For that reason, it seemed useful to correct vision in a less conspicuous way.
As early as 1887, a German physician, Adolf Eugen Fick (1829-1901), had worked out the notion of contact lenses, small lenses that would just fit over the iris of the eye, correcting vision without anyone noticing it.
Glass in direct contact with the eye, however, would be irritating and dangerous. In 1954 plastic contact lenses were produced, which proved useful and popular, and contact lenses are now in common use.
ΣLiquefying Gases
1823 A.D.
LONDON, ENGLAND
Generally speaking, there are two ways of making a gas condense into a liquid. You can cool it. This deprives the gas of energy, and its molecules sink toward each other and cling together. You can also put it under pressure. This forces the molecules toward each other until they cling. Naturally, if you use cold and pressure, you do better still.
English physicist Michael Faraday (1791-1867) was the first to use cold and pressure in a systematic attempt to liquefy gases. He used a strong glass tube bent into a boomerang shape. In the closed bottom, he placed some substance that, when heated, would liberate the gas he was trying to liquefy. He then sealed the open end. He placed the bottom end in hot water. This liberated the gas in greater and greater quantities and, since the gas was in the limited space within the tube, it developed greater and greater pressure.
The other end of the tube Faraday kept in a beaker filled with crushed ice. At that end the gas would be subjected to both high pressure and low temperature and would liquefy. In 1823 Faraday liquefied the gas chlorine in this manner. (Chlorine's normal liquefaction point is -34° C.) Using this method, Faraday liquefied several other gases, too.
YEarly Particle Accelerators
1929 A.D.
UNITED KINGDOM
In the quarter-century since the discovery of radioactivity, the most energetic particles easily available to nuclear physicists had been alpha particles. The shorter the half-life of a particular radioactive isotope, the more energetic the alpha particles they produced. In 1906 British physicist Ernest Rutherford (1871-1937) used alpha particles to bombard atoms and induce nuclear reactions, but even the most energetic alpha particles could only do so much. Of course, cosmic ray particles were more powerful still, much more powerful, but they were not under scientists' control.
What was needed was some way of beginning with ordinary nuclear particles, say protons obtained by ionizing hydrogen atoms, and then accelerating them, perhaps by means of an electromagnetic field.
This was first accomplished by the British physicist John Douglas Cockcroft (1897-1967) and his coworker, the Irish physicist Ernest Thomas Sinton Walton (b. 1903). In 1929 they devised a voltage multiplier that would build up high electrical voltages capable of accelerating protons to the point where they contained more energy than the alpha particles occurring in nature. This was the first particle accelerator (better known to the public for a time as an atom-smasher). For this work, Cockcroft and Walton were awarded the Nobel Prize for physics in 1951.
⌡New Quarks
1974 A.D.
BROOKHAVEN NATIONAL LAB, NEW YORK
While there may be only 12 leptons, there are a large number of hadrons, beginning with the pion, which is the least massive hadron, through over a hundred more massive ones.
Leptons, however, are fundamental particles, which cannot be broken down into simpler ones (as far as we now know), while hadrons are composite particles and are made up of quarks. Quarks, like leptons, seem to be fundamental particles.
In 1974 three kinds of quarks were known: u-quarks, d-quarks, and s-quarks. (The letters stand for up, down, and strange, respectively, though sometimes the s is made to stand for sideways to match the other two.) However, theoretical considerations indicated that quarks ought to exist in pairs. Up-quarks and down-quarks were a pair; there ought to be a quark to serve as the pair of the strange-quark. Such a new quark was named a c-quark even before it was discovered, the c standing for charmed.
In 1974 the American physicist Burton Richter (b. 1931), using the enormous energies of the latest particle accelerators, produced a particle that, from its properties, had to include a c-quark in its makeup. Another American physicist, Samuel Chao Chung Ting (b. 1936), working independently, also produced a particle that had to contain a c-quark. The two shared the Nobel Prize for physics in 1976.
A third pair of quarks, the t-quark and the b-quark (which may stand for top and bottom, or for truth and beauty, depending on the level of whimsy), undoubtedly exist also. If so, there are 12 quarks (the ones I've mentioned and their antiparticles) to match the 12 leptons. This may be significant, though no one yet can explain why quarks and leptons should match each other in number, or why that number should be 12.
OFermi-Dirac Statistics
1926 A.D.
ITALY
Bose and Einstein had worked out the Bose-Einstein statistics a year earlier, but the statistics now turned out to hold only for those particles (like the photon) that had spins of integral values: 0, 1, 2, and so on. Particles like the proton and electron had spins of half-values: 1/2, 1-1/2, and so on.
Once Pauli had worked out the exclusion principle for particles with half-value spins, it was clear that Bose-Einstein wouldn't work for particles with such spins. A new set of statistics would therefore have to be worked out.
Taking the lead in working out that problem, in 1926, was an Italian physicist, Enrico Fermi (1901-1954). Dirac also contributed, so that the result is known as the Fermi-Dirac statistics. All particles subject to these statistics, like the proton and electron, are called fermions in honor of Fermi.
eFertilization
1779 A.D.
ITALY
In early times, it was taken for granted that male human beings provided the "seed" and that females were merely the soil within which the seed developed. If no children were born, it was assumed that the woman involved, like desert soil, was "barren."
In 1779 Spallanzani studied the development of eggs. At that time, it was thought that the ovarian follicles (discovered by the Dutch anatomist Reinier de Graaf (1641-1673) in 1673 and still called Graafian follicles as a result) were the eggs.
Spallanzani showed that fertilization did not take place unless the sperm cells in the semen actually made physical contact with the follicles. This was a strong indication that reproduction was not a one-sided affair, but that both mother and father contributed to the birth of a child and that either side might be at fault in case children were not born.
á Fiber Optics and Telephones
1977 A.D.
U.S.A.
Fiber optics were used for the first time in experimental telephone setups and worked. Within a decade, they were being used in transatlantic cables.
┼Fiber Optics
1970 A.D.
LONDON, ENGLAND
Since current electricity had come into use metallic wires, especially those of copper, had been used to conduct the current wherever it was needed.
By 1970 techniques had been developed to conduct light by means of fine, very clear glass fibers. The fibers were coated with plastic or with a second type of glass so chosen that any light that tended to travel out of the fiber into the coating would be totally reflected. In this way, light could follow the fiber around curves and corners. With the use of lasers, such light could be as easily modulated as electric currents, so that sound waves could be converted into light of varying amplitude and, at the other end, reconverted into sound waves.
Fiber optics, by replacing expensive copper with cheap glass and by using the tiny waves of light, which can carry enormous amounts of information, was instantly seen as having the potential of greatly extending communication by telephone.
vFirst Integrated Circuit
1960 A.D.
DALLAS, TEXAS
Transistors had been in existence for a dozen years, constantly being made smaller and more reliable. By 1960 they could be made so small that it made no sense to try to handle them as separate units.
Instead, small pieces of thin silicon or some other semiconductor, about a quarter-inch square, were etched with tiny transistor circuits. These chips did the work of many transistors and were called integrated circuits.
The use of integrated circuits made computers smaller, cheaper, and more versatile. As time went on, more and more circuits -- eventually thousands -- could be etched into a single chip.
iThe Franklin Stove
1742 A.D.
U.S.A.
Originally, campfires were built in the open, or inside a cave. Fires in confined areas presented a problem with smoke, so chimneys had to be invented.
Fireplaces and chimneys are wasteful, however. Hot air from the fire goes straight up the chimney and does not warm much of the room. Indeed, the rising hot air creates a draft that brings cold air in from the outside.
It occurred to Benjamin Franklin that what was needed was an iron stove within a room. Inside that a fire could be built that would create no draft but would heat up the metal. That in turn would heat the air, and the warm air would stay inside the room instead of vanishing up a chimney. As for the smoke, that could pass through a stovepipe into the chimney.
Stoves of this sort grew instantly popular, and indeed, the modern home furnace in the basement is a kind of Franklin stove.
▐Flame Tests
1758 A.D.
GERMANY
It was always a difficult task for chemists to distinguish one substance from another when some clearly visible property difference (color, softness, and so on) didn't exist. Chemists then had to test for more subtle differences.
A new test that produced something clearly visible to the eye was discovered by a German chemist, Andreas Sigismund Marggraf (1709-1782), in 1758.
Marggraf found that sodium compounds turned a flame yellow, while otherwise very similar potassium compounds turned it violet. (Of course, while the compounds were known, the elements sodium and potassium were not to be isolated for half a century.)
This introduced the flame test into chemistry. Later, Cronstedt introduced the blowpipe, which directed a thin jet of air into a flame, making it hotter and more effectively heating minerals to produce delicate gradations of color. For many decades, chemists had to be skillful at blowpipe analysis if they expected to be successful in research.
╜Florida
1513 A.D.
FLORIDA
Puerto Rico (rich port) had been discovered in 1492 in the course of Columbus's first voyage, and he had left some men behind when he returned to Spain. When he reached Puerto Rico on his second voyage, the settlers were gone, but others soon followed. By 1513 the Spaniards were well established in Puerto Rico, and one of the settlers was Juan Ponce de León (1460-1521).
Ponce de León dealt in slaves and on March 3, 1513, he sailed northwestward in search of more. He reached the North American continent during the Easter season and called the land Florida (flowery) because of its appearance. It became the first portion of what is now the United States to be settled by Europeans.
åFluoridation
1951 A.D.
U.S.A.
The most common disease afflicting mankind is caries, more commonly known as tooth decay. The incidence until recently was almost 100 percent.
Modern dentistry handles it by drilling away the affected area and substituting fillings of ceramic or metal.
Prevention, however, is better than cure, and dentists had noticed that people in certain areas in the United States rarely got caries. Their teeth also showed a mottling of the enamel, caused apparently by the fact that their drinking water had a higher-than-average content of fluoride ions.
The search began for a level of fluoride in the water that would protect against tooth decay without mottling or darkening tooth enamel. By 1951, projects for the careful fluoridation of water supplies were in progress, in the hope that this (and the use of fluoridated toothpaste) would substantially reduce the incidence of tooth decay.
╘Flourine
1886 A.D.
FRANCE
For three-quarters of a century, chemists had known that a certain element must exist. They had even given it a name -- flourine. However, it was a particularly active element, the most active one known, more active than oxygen and chlorine, and nothing seemed capable of forcing it out of combination with other elements.
A number of chemists tried to isolate it and found the matter not only difficult but dangerous, for the materials they had to work with were poisonous.
Finally, a French chemist, Henri Moissan (1852-1907), tried. He used platinum for all his equipment, because it was one of the very few substances that fluorine would not attack and combine with instantly. If he isolated some fluorine in platinum, that fluorine would stay isolated.
He placed a solution of potassium fluoride in hydrogen fluoride in his platinum equipment, chilled it to -50° C to tame the fluorine a bit, and passed an electric current through it on June 26, 1886. He obtained a pale yellow gas that was the long-sought fluorine.
For this, he obtained the Nobel Prize in chemistry in 1906 (receiving, according to report, one vote more than Mendeleyev did, which if true was an injustice, for Mendeleyev was more deserving).
°Fruit Flies
1907 A.D.
NEW YORK, NEW YORK
In 1865 Austrian botanist and Augustinian monk, Gregor Johann Mendel (1822-1884), had worked out the laws of inheritance by studying pea plants, and in 1902 these laws had been verified for animals by British biologist William Bateson (1861-1926). However, animals are much harder to work with on the whole than plants are. In 1907, however, the American geneticist Thomas Hunt Morgan (1866-1945) began to use a tiny insect called Drosophila, or fruit fly. They have only four chromosome pairs in each cell, are simple to feed, and breed readily and copiously at brief intervals.
In studying them, Morgan found that there were characteristics that were linked and inherited together, but that the linkage was not necessarily permanent. Every once in a while, two characteristics that had previously been inherited together were suddenly inherited independently. He was able to correlate this with the fact that chromosomes sometimes interchanged parts so that two characteristics ordinarily on the same chromosome came to be on different chromosomes.
Fruit fly research greatly hastened the pace at which knowledge of genetic mechanisms increased. For his work with them, Morgan was awarded the Nobel Prize for medicine and physiology in 1933.
»Fingerprints
1885 A.D.
ENGLAND
In 1885 British anthropologist Francis Galton (1822-1911) pointed out the individuality of fingerprints. No two people (barring identical twins) had identical fingerprints, and Galton worked out a thoroughgoing system of classifying and identifying them.
In handling smooth surfaces, people always left sweaty, greasy fingerprints, even when these were unnoticeable unless the surface was appropriately powdered.
Eventually, fingerprints proved a useful way of showing that a given person had been present at a given place and had handled a given object. This added a new dimension to forensic medicine (from a Latin word referring to a public place such as a courtroom).
XFood Classification
1827 A.D.
ENGLAND
Prior to this time, food was seen to differ in appearance, in smell, and in taste, but anything that satisfied hunger was assumed to be as good as anything else that did the same.
However, as chemistry developed, it became clear that foods differed in chemical nature and therefore might be different in their effect on the human body. The first to make a broad classification of foodstuffs on a chemical basis was Prout who, in 1827, divided food into three broad classes, which today we call carbohydrates, fats, and proteins. Naturally, this classification was not exhaustive, and there are important substances that do not fall into any of these groups -- some of them present in only small quantities, but vital nevertheless.
Prout's classification, however, was a good start toward understanding some of the complexities of dietetics.
nUsing Forks
1071 A.D.
BYZANTIUM (Eastern Europe)
Knives and spoons are of prehistoric origin, but forks are relatively new. Byzantine aristocrats used them at a time when everyone in western Europe, high and low, ate with their fingers. A Byzantine princess who married a doge of Venice brought her forks with her. The Venetian aristocracy picked up this obviously clean habit and the fashion spread.
Nevertheless, it did seem a bit persnickety to many people, who felt it was an example of false gentility and prissiness. To this day we sometimes hear the phrase "fingers were made before forks." So they were, and so were dirty fingers.
Formation of the Moon
1974 A.D.
PASADENA, CALIFORNIA
Over the course of the last century, three different types of suggestions had been made about the origin of the Moon. It was suggested first that the Moon was originally part of the Earth and pulled away as a result of centrifugal effect when the primordial Earth was spinning rapidly. However, Earth had never rotated rapidly enough to make such a pullaway possible.
Second was the thought that Earth and Moon had formed separately from the same swirl of planetesimals. But the Earth and Moon should then have much the same chemical composition, and they don't. Earth, for instance, has a large nickel-iron core while the Moon seems to have none at all.
Third was the thought that Earth and Moon were formed from different swirls of planetesimals, and at some time in the past the Earth captured the Moon. But the mechanics of such a Moon capture are difficult to work out.
These seemed the only three possibilities, and each one was so flawed that it looked as though the only way out of the mess was to decide that the Moon didn't really exist.
In 1974, however, the American astronomer William K. Hartmann suggested a fourth alternative. Suppose that in the early days of the Solar System, a planet the size of Mars (about one-tenth the mass of the Earth) had had a glancing collision with Earth. It would knock off part of the Earth's outer layers, which would coalesce into the Moon, while the colliding body coalesced with Earth. The nickel-iron cores of Earth and the colliding object would merge, while the Moon, formed from the outer layers of Earth, would lack such a core.
The suggestion was largely ignored, but eventually computer simulations of such a collision made the idea begin to look good. At the moment, Hartmann's suggestion is preferred to any of the older ones.
Fossils
1669 A.D.
COPENHAGEN, DENMARK
The word fossil is from a Latin word meaning "to dig." At first anything that could be dug out of the earth was called a fossil. The word came to be applied, however, to those particular objects that were dug up and that, although made of rock, seemed remarkably like remnants of living things -- bones and teeth particularly. Georgius Agricola (1494-1555) had commented on these over a century earlier.
There were numerous theories about these fossils. Some thought them practice attempts by God to create living things. Some thought them failing attempts of Satan to imitate God. Some thought them the remains of animals that had drowned in Noah's Flood.
In 1669, however, the Danish geologist Nicolaus Steno (1636-1686) maintained that they were the remains of creatures that had lived long ago and whose remains had slowly petrified; that is, been converted into stone. This view gradually prevailed, and fossils were to be the most spectacular (though far from being the only) evidence in favor of biological evolution.
ÿThe Four-Stroke Engine
1876 A.D.
GERMANY
The Lenoir internal-combustion engine had been devised 16 years before, but its inefficiency was recognized.
A German engineer, Nikolaus August Otto (1832-1891), built a version in which the piston made four strokes. As the piston moved outward (first stroke), a mixture of air and flammable vapor would be drawn into the cylinder. As the piston moved inward (second stroke), the mixture would be compressed, and at the height of the compression, a spark would set off an explosion. The explosion would drive the piston outward (third stroke, which would supply the power that did the work). As the piston moved inward (fourth stroke), the waste gases would be forced out. The cycle would then be repeated.
Otto built such a four-cycle engine in 1876. The Otto engine, as it was called, was such a vast improvement that it caught on at once and was the basis for the internal-combustion engines of today.
Calculating with Fractions
1586 A.D.
NETHERLANDS
Mathematicians had found fractions difficult to handle ever since the days of the Sumerians. Special rules had to be worked out to deal with them.
In 1586, however, Dutch Mathematician Simon Stevin (1548-1620) showed that they could be made part of ordinary positional notation. To the right of the units column (on the other side of a decimal point) could be the tenths column, then the hundredths column, and so on. Thus 2-1/4 would become 2.25; 2-1/8 would become 2.125; 2-7/8 would become 2.875; and so on.
The disadvantage of such decimal fractions is that some never end.
Thus 2-1/3 is 2.3333333 . . . forever; 2-5/6 is 2.8333333 . . . forever; and so on. Despite this, decimal fractions greatly simplified computations involving fractions.
ªFrancium
1939 A.D.
FRANCE
Only three elements remained undiscovered: numbers 61, 85, and 87. In 1939 the French physicist Marguerite Perey (1909-1975), working with the radioactive element actinium, discovered a type of beta activity that was not quite like that of any known isotope. She tracked it down and found that it resulted from the breakdown of an isotope of element number 87. She named it francium, for her native country.
As it turned out, the most nearly stable isotope of the element is francium- 223, which has a half-life of only 22 minutes. Of all the elements between 1 and 92, francium is the only one that possesses no isotope with a half-life of as much as half an hour.
bInventing the Lightening Rod
1752 A.D.
PHILADELPHIA, PENNSYLVANIA
The Leyden jar had become a favorite plaything of many scientists. One of them was Benjamin Franklin.
In 1747 Franklin rejected French physicist Charles-Françcois de Cisternay du Fay's notion of two electrical fluids. He thought there was only one, which could exist in an excess (above normal) or in a deficiency (below normal). Excess repelled excess, since neither could accept the other's. Similarly, deficiency repelled deficiency, since neither could offer anything to the other. Excess, however, attracted deficiency, and the electrical fluid poured from the excess to the deficiency, neutralizing both and leaving each uncharged.
Franklin suggested that the excess be called positive electricity and the deficiency negative electricity. There was no telling which variety of electricity, vitreous or resinous, was positive and which negative. Franklin guessed arbitrarily and happened to guess wrong. That makes no difference, however. The names can be used and the literal meanings forgotten.
Franklin noted the manner of discharge of the Leyden jar. When the electrical charge was drawn off, it emitted a spark of light and a crackle of sound. Franklin was struck by the similarity to a tiny lightning stroke and an equally tiny crack of thunder. He at once reversed the thought. During a thunderstorm, did Earth and sky set up a gigantic Leyden jar, and was the lightning and thunder an equally gigantic discharge?
He decided to experiment. In 1751, he flew a kite in a thunderstorm. The kite carried a metal point to which a long silk thread was attached. At the bottom of the thread, near Franklin (who held onto the silk by way of a second thread that remained dry), was a metal key. As the thunderclouds gathered and the silk thread began to show signs of electrical charge (the separate fibers repelled each other), Franklin put his knuckle near the key and it sparked and crackled just like a Leyden jar. Moreover, Franklin charged a Leyden jar from the key just as easily as if it were a friction machine. The Leyden jar charged by heavenly electricity behaved precisely as though it had been charged by earthly electricity. The two electricities were identical.
Franklin was able to put his discovery to practical use at once. Lightning, he decided, hit a particular building when that building gathered charge during a thunderstorm. His experience with Leyden jars showed that they discharged much more easily if a sharp needle was attached to them. Indeed, the charge leaked out so easily through the needle that they couldn't be charged in the first place. Why not, then, attach a sharp metal rod to the top of a building, and ground it properly, so that any charge that gathered might leak away rapidly and silently and no charge would accumulate to the point where a disastrous discharge would be forced.
Franklin published his thoughts on the matter in 1752 in Poor Richard's Almanac, and the lightning rods, as they were called, began to go up at once, first in America and then in Europe. They proved efficacious, and for the first time in history, a natural catastrophe was averted not by prayer or by magical incantations of one sort or another, but by reliance on an understanding of natural laws. Once lightning rods appeared on church steeples (which, being the highest point in town, were particularly vulnerable), the point was made for all to see.
αFreon and the Ozone Layer
1974 A.D.
U.S.A.
Freon, which had been introduced by Midgley, and similar compounds had first been used in air-conditioning and later in spray cans. The compounds contained chlorine and fluorine atoms attached to a carbon skeleton (chlorofluorocarbons) and seemed absolutely safe.
As such chemicals were released into the air by spray cans and eventually leaked out of air-conditioning units, they did not accumulate in such quantities as to present direct difficulties for any living organism.
On the other hand, some chlorofluoro-carbons inevitably drifted upward into the atmosphere and there they encountered the ozone layer. Two American scientists, F. Sherwood Rowland and Mario Molina, pointed out that such chlorofluorocarbons had the potential for destroying the ozone layer, even if they were present in comparatively small amounts. And indeed, in recent years the ozone layer has been observed to be thinning.
As the ozone layer thins, more energetic ultraviolet light from the Sun will be able to reach Earth's surface, causing increases in the incidence of such problems as skin cancer and cataracts. Worse yet, the ultraviolet may be deadly to soil bacteria and ocean plankton, with incalculable effects on Earth's ecological balance.
ⁿFrequency Modulation
1939 A.D.
U.S.A.
Static in radio broadcasts was proving a rather intractable problem. Radio transmission for the first 40 years after Marconi's discovery was carrried out by systematically altering the amplitude (the height of the wave) of the carrier signal to match the variation in the amplitude of the sound waves being transmitted. This was called amplitude modulation, or AM.
Unfortunately, thunderstorms and electrical appliances also modulate the amplitude, doing it randomly and producing the irritating noise of static.
In 1939, however, Armstrong, who had invented the superheterodyne receiver, devised a method of transmitting a signal by systematically altering the frequency (the length of the wave) of the carrier signal. This was called frequency modulation, or FM. Thunderstorms and electrical appliances have no effect on frequency, so FM transmission is largely static-free.
Unfortunately, FM will work only for carrier waves of high frequency, and these cannot be transmitted much beyond the horizon.
êPsychoanalysis
1893 A.D.
VIENNA, AUSTRIA
Austrian physician Josef Breuer (1842-1925) had started to use hypnotism in the treatment of mental diseases such as hysteria. The method had later been taken up by Austrian physician Sigmund Freud (1856-1939), but he eventually abandoned hypnotism for free association, allowing the patient to talk randomly and at will with a minimum of guidance. In this fashion, the patient was gradually put off guard, and matters came to be revealed that in ordinary circumstances would have been kept secret from the patient's conscious mind.
The advantage of this method over hypnotism was that the patient was aware of what was going on at all times and did not have to be informed afterward of what had been said.
In 1893 Freud and Breuer published The Psychic Mechanism of Hysterical Phenomena. This is considered to have laid the foundations of the medical technique of psychoanalysis.
∞Freud and Dreams
1900 A.D.
AUSTRIA
Dreams had always mystified human beings. Dreaming that dead people were alive helped lead to a belief in the spirit world. Erotic dreams led to belief in incubi and succubi. Dreams seemed to be doorways into a different world, to be messages from the gods, to be revelations of events at a distance or in the future.
All this was dismissed as superstition by rationalists, but Freud gave new meaning to dreams.
In 1900 he published The Interpretation of Dreams. Dreams, he maintained, might represent truths about human beings that they were not willing to accept in their waking hours, so that psychoanalysis might be hastened and made more effective if the analyst carefully considered the literal and symbolic meaning of dreams.
The Fuel Cell
1839 A.D.
UNITED KINGDOM
Ordinary electric batteries, even the copper and zinc Daniell cell developed by British chemist John Frederic Daniell (1790-1845), obtain their energy by, in effect, burning metals. Electricity, as obtained from batteries, would be much cheaper if ordinary fuels could be burned instead, a fuel cell.
In 1839 the British physicist William Robert Grove (1811-1896) devised an electric cell that made use of hydrogen and oxygen, producing electricity as they combined into water. Even today hydrogen is still rather expensive, however. Using methane or coal dust along with oxygen would be close to ideal, but in all the century and a half since Grove's discovery, scientists have not been able to make the fuel cell practical. It remains a laboratory curiosity.
QSteamboats
1807 A.D.
NEW YORK, NEW YORK
Since American inventor John Fitch (1743-1798) failed to make his steamboat succeed, the notion had not been taken up again. But then the American inventor Robert Fulton (1765-1815) tackled the project. In 1807 he built the Clermont, 133 feet long. This vessel performed well, steaming up the Hudson from New York to Albany in 32 hours, maintaining an average speed of nearly 5 miles per hour.
Soon he had a fleet of steamboats in operation, and unlike Fitch, he was commercially successful. For this reason, Fulton is usually considered the inventor of the steamboat.
╧ Gadolinium
1880 A.D.
FINLAND
Marignac, who had discovered ytterbium, discovered yet another rare earth element in 1880. This time Gadolin, who had discovered the rare earths was honored, and the element was named gadolinium.
ÉGalaxy
1785 A.D.
BATH, UNITED KINGDOM
British astronomer William Herschel (1738-1822) reported in 1785 on his attempt to determine the shape of the conglomeration of stars of which we were part. To count all the stars all over the sky was, of course, impractical. He therefore took samples. He chose 683 regions, well scattered, and counted the stars he could see in each one. (This was the first application of statistical methods to astronomy.)
He found that the number of stars per unit area of sky rose steadily as one approached the Milky Way, was maximal in the plane of the Milky Way, and minimal in the direction at right angles to that plane. This, he thought, would be explained if the star system were lens-shaped, with the Milky Way marking out the long diameter of the lens all around.
Such a lens-shaped star collection had been supposed by earlier astronomers, but Herschel had now made it a matter of close observation. For the first time, the Galaxy truly took shape, although even then no astronomer had a conception of its true size or of the vast number of stars it contained. Herschel thought it contained a 100 million stars -- an enormous underestimate.
╧Galileo and the Pope
1633 A.D.
ROME, ITALY
Galileo Galilei (1564-1642) had long accepted the Copernican idea of a heliocentric (sun-centered) planetary system, but he was reluctant to be open in this view, for the papacy was strong in Italy and geocentrism was the only allowable astronomical view in Catholic doctrine of the time.
Urban VIII (1568-1644) had become Pope in 1623, and Galileo thought him to be a friend. In 1632, therefore, he took the chance of publishing a book with the title, in English, Dialogue on the Two Chief World Systems. The dialogue has three actors: a Ptolemy-supporter, a Copernicus-supporter, and a neutral person seeking information.
The book created a stir. In the first place, it was written in Italian rather than in Latin, so that it was not confined to scholars but could reach the general public. In the second place, Galileo was a brilliant writer, much given to sarcasm, and he certainly gave the Copernican the best of it. What's more, it was easy to persuade the Pope that the Ptolemy-supporter was meant to be a satire on him personally.
Galileo was therefore brought before the Inquisition in the most famous confrontation between science and religion prior to the evolution controversy in the present century.
On June 22, 1633, under the threat (but not the use) of torture, he was forced to renounce any of his views that were at variance with geocentrism. Sometimes Galileo is blamed for giving in, but he was 70 at the time, and he had the example of Italian philosopher Giordano Bruno (1548-1600), a generation before, to keep in mind.
However, the victory of the Church was an empty one. The heliocentric theory continued to gain an ever-firmer hold on the minds of scientists and ordinary people everywhere.
èThe Pendulum
1581 A.D.
ITALY
In measuring time intervals of less than a day, the point is to find some physical action that proceeds at a constant rate. The sifting of sand or the dripping of water through a small hole, the burning of a candle, or the progress of the Sun across the sky are all fairly constant motions, but might there not be some convenient action that was even more steadily constant? The first hint of a constant action that was unknown to the ancients came in 1581, when a 17-year-old Italian boy, Galileo Galilei (1564-1642), who is usually known by his first name, was attending services at the Cathedral of Pisa.
His attention was caught by a chandelier that swayed as air currents caught it. Sometimes it swung through a small arc, sometimes through a larger one, but to Galileo's inquiring mind, there seemed an anomaly: long or short, the time it took the chandelier to complete its swing back and forth seemed the same. He timed it by the beating of his pulse. Upon returning home, he set up two pendulums of equal length and swung one in larger, one in smaller sweeps. They kept together and he found he was correct.
Nevertheless, when in later life Galileo conducted experiments in which it was necessary to know the time elapsed, he had to continue to use his pulse or dripping water. Not for another seven decades would the steady beat of the pendulum be put to use as a device to help measure time.
¼Gallium
1874 A.D.
FRANCE
The discovery of new elements continued after Mendeleyev announced his periodic table of elements. In 1874 the French chemist Paul-Émile Lecoq de Boisbaudran (1838-1912) found a zinc ore that displayed hitherto unknown spectral lines. He extracted the new element and named it gallium, from the old Latin word for the area that became France after the fall of the Roman Empire.
Once the discovery was announced, Mendeleyev pointed out at once that the element was his eka-aluminum. He was right. The characteristics and properties possessed by gallium were exactly what he had predicted for eka-aluminum. The validity of the periodic table could not thereafter be denied.
∞Electrical Stimulation
1780 A.D.
ITALY
An Italian anatomist, Luigi Galvani (1737-1798), noticed in 1780 that the muscles of dissected frog legs twitched wildly when a spark from a Leyden jar struck them. This was not too surprising. Electric shocks made living muscles twitch, why not dead ones, too?
Since Benjamin Franklin (1706-1790) had shown that lightning was electrical in nature, Galvani wondered whether muscles would twitch if exposed to a thunderstorm. He therefore placed frog muscles on brass hooks outside the window so that they rested against an iron latticework.
The muscles did indeed twitch during the thunderstorm, but they also twitched in the absence of it. In fact, they twitched whenever they made simultaneous contact with two different metals.
Apparently, electricity was involved, but where did it come from, the metals or the muscle? Galvani decided it was the muscle, and he spoke of animal electricity. In this he was wrong, but electricity was involved with nerve and muscle action just the same.
¡Game-Playing Computers
1950 A.D.
BOSTON, MASSACHUSETTS
It was natural to think of computers at first simply as very fast calculating machines, different from Pascal's first adding device in degree but not in kind.
However, it quickly became apparent that computers could solve problems that human beings considered to require human thought. Thus in 1947 the American engineer Arthur L. Samuel (b. 1901) had worked out a checker-playing computer, refinements of which eventually proved capable of playing championship checkers.
Checkers, however, is a comparatively simple game. In 1950 the American mathematician Claude Elwood Shannon (b. 1916) suggested ways to design a chess- playing computer, and such machines have since been built and play excellent games of chess. Indeed, it is not beyond the limits of probability that such a machine might become the world's chess champion.
Such devices further exemplify the potential reality of artificial intelligence.
~Game Theory
1928 A.D.
GERMANY
A new branch of mathematics was opened by a Hungarian-born American mathematician, John von Neumann (1903-1957), in 1928. He began devising the principles of what came to be called game theory because it dealt with the best strategies to follow when playing simple games with fixed rules, such as coin-matching.
The principles so developed could then be applied to far more complicated games, such as business or war, and an attempt made to work out the best strategy to beat a competitor or an enemy. Even scientific research can be considered a game, one in which scientists pit their wits against the impersonal Universe.
8Human Digestion
1825 A.D.
U.S.A.
On June 6, 1822, a 19-year-old Canadian, Alexis St. Martin, was accidentally shot in the side at a frontier post in northern Michigan. It was a close-range shotgun blast and he received a terrible wound.
An American army surgeon at the post, William Beaumont (1785-1853), treated him, and he recovered completely except that an opening (or fistula) remained in his side. It was nearly an inch across and it led into his stomach.
Through this opening, Beaumont, beginning in May 1825, was able to observe the changes in the stomach under different conditions and to extract samples of gastric juice, which he sent all over the world. It was like having the benefits of a vivisection. Beaumont's work served as a source for much early information on the process of digestion and increased interest in the field.
OGas Volume and Temperature
1699 A.D.
FRANCE
The French physicist Guillaume Amontons (1663-1705) devised an air thermometer that was different from Galileo Galilei's (1564-1642), for it measured temperature by the change in gas pressure rather than by the change in gas volume. He used the thermometer to show that a liquid such as water always boiled at the same temperature. This made it possible to use the temperature at which water boiled as a standard reference.
With his new thermometer, Amontons tested the volume of a fixed quantity of gas at different temperatures and, in 1699, showed that the volume increased at a steady rate as the temperature went up and decreased at the same steady rate as the temperature went down. Much more important, he showed that for each gas he studied, the volume change with temperature was the same. It seemed a property of all gases.
4The Bicycle
1839 A.D.
COURTHILL, SCOTLAND
The first vehicle a modern would recognize as a bicycle was designed in 1839 by a British blacksmith, Kirkpatrick Macmillan. It had two wheels, of which the rear was slightly larger, and a seat between. It had pedals, which were so arranged as to turn the rear wheel. It was heavy and clumsy and underwent a number of fundamental changes before becoming the instrument of today, but it did work. For the first time, progress had been made in allowing humans to make use of their own muscles to travel at a speed greater than they could run.
ΣQuarks
1961 A.D.
PASADENA, CALIFORNIA
In 1961 Murray Gell-Mann, who had advanced an explanation of strange particles, worked out a method for bringing order to the numerous hadrons that were being discovered.
He grouped them into families in which certain particle properties increased in value in a regular fashion and called it, whimsically, the Eightfold Way, with reference to certain Buddhist teachings. In doing so, he found that certain family groups had missing members, which he believed represented hadrons that had not yet been detected -- much as Mendeleyev had predicted the existence of undiscovered elements from gaps in his periodic table.
Independently, an Israeli physicist, Yuval Ne'emen (b. 1925), worked up similar groupings at about the same time.
In order to explain the existence of the families, Gell-Mann postulated the existence of unusual particles that he called quarks (from a phrase in Finnegans Wake by James Joyce). There were but a few of these quarks, each accompanied by an antiquark, and by grouping them in different combinations, either two or three at a time, the various hadrons could be accounted for.
The most startling thing about these quarks was that, if they were to produce hadrons properly, they had to have fractional electric charges. Some had charges of plus or minus 1/3 or 2/3. The notion of fractional charges was hard to take, but the quark theory explained so much that it was accepted perforce and earned for Gell-Mann the Nobel Prize for physics in 1969.
Space Rendezvous
1966 A.D.
HOUSTON, TEXAS
Maneuverability in space was increasing rapidly. On December 15, 1965, the American satellite Gemini VII, having been in space for 14 days, approached within several feet of the previously launched Gemini VI. This was the first space rendezvous.
On March 16, the American satellite Gemini VIII linked up with another orbiting vessel. This was the first actual docking of one space vessel with another -- a maneuver essential if human beings were to be sent to the Moon and brought safely back.
rGenes
1909 A.D.
DENMARK
Thanks to the work of Morgan and his fruit flies, it was established that chromosomes contained chains of many units of inheritance. It would obviously be convenient to have some way of referring to those units in a concise way. In 1909 the Danish botanist Wilhelm Ludvig Johannsen (1857-1927) suggested that they be called genes. The suggestion was adopted.
°Gene Synthesis
1970 A.D.
MADISON, WISCONSIN
Khorana, who had worked on the genetic code, headed a research team that in 1970 succeeded in synthesizing a genelike molecule from scratch. That is, they did not use an already existing gene as a template but began with nucleotides and put them together in the right order.
Further exemplifying the strides made in the synthesis of complicated molecules, Li, who had synthesized the enzyme ribonuclease, synthesized the still more complicated molecule of growth hormone in 1970.
PGenetic Engineering
1973 A.D.
UNIVERSITY OF COLORADO
It is one thing to understand the fundamental chemistry of the DNA molecules that make up the genes; it is another to be able to modify that chemistry. In 1973 two American biochemists, Stanley H. Cohen and Herbert W. Boyer, showed that when DNA was broken into fragments and these were combined into new genes, the new genes could be inserted into bacterial cells, where they could be reproduced whenever the cells divided in two.
This was the beginning of genetic engineering. It offered a technique for something as simple and useful as modifying defective genes to make them normal, thus holding out the hope that genetic defects might someday be cured. It also offered the possibility of something as far-reaching as the ability to direct human evolution (with all the treacherous side effects that might involve).
The Genetic Code
1954 A.D.
U.S.A.
Granted that DNA contained the information that governed the inheritance of characteristics, it must do this by overseeing the manufacture of enyzmes, which in turn controlled the chemical reactions that went on inside cells. But how could DNA turn the trick? It was composed of chains of four different nucleotides, while enzymes, which were proteins, were composed of chains of 20 different amino acids.
In 1954 George Gamow suggested that it made no sense to try to line up an individual nucleotide with an individual amino acid, since there were too few of the former and too many of the latter. He pointed out that it must be necessary to deal with combinations of at least three nucleotides. If there were four different nucleotides, they could be built up into 64 different trinucleotides, or codons -- more than enough to carry the information necessary to build up proteins.
Gamow got the details wrong in his scheme, but he had the right idea just the same. He was the first to conceive of a multinucleotide genetic code.
¿ Genetics
1865 A.D.
BRNO, CZECHOSLOVAKIA
There was a flaw in the theory of evolution proposed by British biologist Charles Robert Darwin (1809-1882) in 1858. Granted that in every generation of a particular species there are random variations, there are also (to some extent, at least) random matings. Therefore, the variations should tend to vanish into an average, since extremes are not likely to mate with similar extremes. (It might even be argued that the second law of thermodynamics requires this tending toward an average.)
The flaw was addressed by an Austrian botanist and Augustinian monk, Gregor Johann Mendel (1822-1884), who experimented with peas that he grew in the monastery garden.
Carefully, Mendel arranged for various plants to self-pollinate, wrapping them to guard against accidental pollination by insects. Carefully, he saved the seeds produced by each self-pollinated plant, planted them separately, and studied the new generation.
Mendel found that if he planted seeds from dwarf pea plants, only dwarf pea plants sprouted. The seeds produced by this second generation also produced only dwarf pea plants. The dwarf pea plants "bred true."
Seeds from tall pea plants behaved in a more complicated fashion. Some bred true, but some did not. Those that did not breed true gave rise to tall plants three-quarters of the time and to dwarf plants one-quarter of the time.
Mendel then crossed dwarf pea plants with the tall pea plants that bred true. All the peas produced grew into tall pea plants. The characteristics of dwarfness seemed to have disappeared.
Next Mendel had each of this new generation of tall plants self-pollinate and found that they produced peas that grew into tall plants and dwarf plants in a 3-to-1 ratio. Dwarfness had been submerged in one generation but had then shown up in the next.
In other words, tallness was dominant and dwarfness recessive, so that tallness overwhelmed dwarfness -- but only temporarily.
Mendel found that other types of traits in pea plants worked the same way. There was no mixing of extremes.
Mendel also found that male and female contributed equally. It was as though each organism had two factors for a particular trait and each contributed one of them to the offspring. If the factors were different in the offspring, and one was dominant, the recessive characteristic didn't show but was still there. It might be the one handed on to the next generation, and if the other parent also handed on a recessive, so that the offspring had two recessives and no dominant, the recessive trait would appear again.
Mendel thus worked out the Mendelian laws of inheritance, as they were later to be called, and founded the science of genetics (from a Greek word meaning "to give birth to"). He published his first paper on this work in 1865 (a second followed in 1869), but it was totally ignored for 33 years.
Since the Mendelian laws showed that extremes did not mix into a blind average, but continued to show up, they provided the mechanism by which natural selection could bring about a gradual change in species. Thus, Mendel corrected the flaw in Darwin, but both Mendel and Darwin were dead before the world of science came to realize what had happened.
7 General Relativity
1916 A.D.
GERMANY
Eleven years before, Einstein had advanced his special theory of relativity, in which he showed that the laws of physics remained unchanged in systems moving at constant velocity relative to each other. In 1916 he extended this to systems moving relative to each other at any velocity, however changing.
This was his general theory of relativity, often shortened to general relativity.
To make this possible, he assumed that inertial mass (mass derived from measurements of acceleration) and gravitational mass (mass derived from measurements of gravitational intensity) were identical. He also assumed that space was curved in the presence of mass, and that gravitation was not a force but merely the result of moving objects following the shortest possible path in curved space.
He advanced a set of equations to cover all this, equations that allowed grand conclusions to be drawn about the universe as a whole, so that he founded the science of cosmology. Einstein pointed out that Newton's laws of gravitation produced results quite close to those of general relativity but that there were three kinds of differences that might be measured in order to decide which was a closer approach to reality.
First, Einstein's theory allowed for a shift in the position of the perihelion of a planetary orbit slightly beyond that which would be expected in a Newtonian Universe. This advance of the perihelion had been discovered by Leverrier in the case of Mercury, Vulcan) 70 years earlier.
General relativity explained it without having to call upon an intra-Mercurian planet, which had never been found. The fact that this effect was already known rather diminished its importance, however.
Second, Einstein showed that light moving upward against a strong gravitational field should show a red shift. This involved something that had not been expected earlier, but even the Sun's gravitational field wasn't intense enough to make the measurement practical. Nothing much could be done with the prediction, therefore.
Third, and most dramatic, Einstein showed that light would be deflected by a gravitational field substantially more than would be expected in a Newtonian Universe, and the difference could be measured. To do so, however, it would be necessary to locate stars in the neighborhood of the Sun during a total eclipse.
Their light would have reached Earth after passing close to the Sun and bending in its path very slightly as it did so, so that each star would be seen a bit farther from the Sun than it really was. This would appear if the same region of the sky was photographed when the Sun was in another part of the sky.
However, World War I was raging and there was no way any eclipse expedition could be safely organized. In fact, it was difficult to get word of Einstein's views out of Germany. So the world had to wait.
y
Geometry
300 B.C.
ALEXANDRIA, EGYPT
Geometry, as a practical study, may have begun in Egypt, where the building of pyramids and the necessity of reestablishing boundaries after the Nile flood made it essential. The Greeks made it theoretical, however, working with ideal points, lines, curves, planes, and solids. They attempted to prove things by reason alone and without actual measurement. (Reason was the mark of the philosopher, measurement was only for the artisan, and the Greek scholars were snobs. Snobbery turned out to be useful in mathematics, though not in experimental science, where the Greeks fell badly short.)
A number of Greek mathematicians contributed to the development of geometry, particularly Eudoxus. It was Euclid (fl. ca. 300 B.C.) who brought geometry to maturity, however. He worked in Alexandria, Egypt, and thereby hangs a tale.
The city of Alexandria, on the seacoast at the westernmost branch of the Nile delta, had been founded by Alexander the Great (356-323 B.C.) and named after himself. It was a largely Greek city, though it contained many Egyptians and Jews as well. It quickly became the largest and most cosmopolitan city of the Greek world. Ptolemy I (ca. 366-ca. 283 B.C.), who ruled over Egypt after Alexander's death, established his capital at Alexandria.
Ptolemy I saw himself as a patron of the arts and sciences and founded the Museum, so-called because it was an institution devoted to the Muses, the patron goddesses of learning. He and his son, Ptolemy II (308-246 B.C.), made the Museum the largest and most important of all the ancient universities. Associated with it was the largest of all the ancient libraries. The Ptolemies encouraged scientists and thinkers generally to come to Alexandria and subsidized them well. Euclid, a Greek mathematician who may have studied at the Academy, moved from Athens to Alexandria as a result, symbolizing the "brain drain" that followed, as Greeks poured out of Greece proper into the new dominions of the Hellenistic kingdoms that succeeded Alexandria. Perhaps about 300 B.C., Euclid began compiling all the geometrical findings of earlier mathematicians into a textbook eventually called Elements. He added comparatively little himself, but what he did was beyond price.
He began with a minimum number of statements that were so self-evident that they required no proof. From these axioms, he proceeded systematically to prove theorem after theorem, each proof depending only on the axioms and on previous proofs, so that geometry was given a firm foundation and structure. It was the most successful textbook ever written and has been used, in more or less modified form, to this day.
┤Germanium
1886 A.D.
GERMANY
A German chemist, Clemens Alexander Winkler (1838-1904), analyzed a silver ore and, when he had completed his work, found that the elements he had located added up to only 93 percent of the whole. Puzzled, he searched out the remaining seven percent and, in 1886, found a hitherto unrecognized element, which he named germanium, after Germany.
It turned out to be eka-silicon and filled the one remaining gap for which Mendeleyev had predicted a new element. What's more, the properties that Mendeleyev had predicted for it once again turned out to be absolutely correct. Three predictions made, three predictions fulfilled. It was as amazing a feat as the discovery of Neptune.
┐The Greenhouse Effect
1863 A.D.
IRELAND
In 1863 the Irish physicist John Tyndall (1820-1893) pointed out that such gases as carbon dioxide and water vapor are transparent to the visible light that reaches Earth's surface from the Sun, but rather opaque to the infrared radiations that the Earth gives off to space when it cools down at night. This means that the presence of even a small amount of carbon dioxide and water vapor in the air will keep the Earth's surface temperature higher than it would otherwise be. This resembles the situation in a greenhouse, where light enters through the glass and warms the atmosphere within, but heat escapes only with difficulty, so that the net effect is to warm the greenhouse. For this reason, the action of carbon dioxide and water vapor is referred to as the greenhouse effect.
Since human activity has somewhat increased the carbon dioxide of the atmosphere and is continuing to do so, the greenhouse effect has become a serious threat.
╘Gibberellins
1957 A.D.
TOKYO, JAPAN
There are plant hormones that encourage growth, differentiation of tissue, budding, flowering, and so on. One group of these, the gibberellins, had been isolated from a fungus of the genus Gibberella (hence their name).
They were studied first in Japan before World War II, but it was not until 1957 that an awareness of the compounds reached the west. Gibberellins are used to increase the size of plants, particularly in the cultivation of grapes.
XGiotto's Comet
1301 A.D.
ITALY
A bright comet was visible in Europe's sky in 1301. It created the usual panicky stir, but the Italian artist Giotto di Bondone (ca. 1267-1337), usually known by his first name, observed it with an artist's eye.
Till then, and for a considerable time afterward, those who drew comets let their panic be their guide and presented the silliest pictures imaginable. In 1304, however, Giotto painted The Adoration of the Magi, in which he pictured the star of Bethlehem as a comet, and seems to have let the comet of 1301 guide his brush. Giotto's is the first realistic depiction of a comet.
ÖGlaciers
1821 A.D.
SWITZERLAND
Mountain glaciers were well known to people who lived in mountainous areas such as Switzerland. It was known that they stretched down the declivities on the mountainsides like rivers of ice; that the end in the valley melted in the summer and refroze in the winter; that in advancing and retreating at the valley end, the glaciers scraped rocks, since the pebbles frozen into the bottom of the glaciers gouged striations into those rocks.
It was also noticed by some geologists that there were striations in rocks that were nowhere near glaciers. It made sense to suppose that the striations could have been caused by glaciers, but how?
A Swiss geologist, Ignatz Venetz (1788-1859), decided there was only one explanation. Glaciers must, at some time in the past, have extended far beyond their present limits. He published material to this effect in 1821, but it made no great impression at the time.
Glass-Blowing
100 B.C.
SYRIA
Glass-making was, for many centuries, a slow and tedious affair, so that glass was rare and was used only for ceremonial purposes. The turning point came about 100 B.C., apparently in Syria, when someone discovered that molten glass could be blown out of a pipe like a soap bubble, so that a round hollow shape could be made at once, and that shape could easily be changed into enchanting curves, with other bits of glass fitted onto it. The whole glass vessel could then be allowed to cool and be broken off the blowpipe. In this way, artistic vases and cups and vessels of all kinds could be made. Glass at once grew cheaper and more common and was popular throughout the Mediterranean world. It remained colored, however. The art of producing colorless glass was still not known.
ìGlass
2500 B.C.
EGYPT
Glass is made out of sand rather than out of clay as pottery is. Glass is not really a solid at all but a liquid that is so stiff it does not flow perceptibly and seems to be solid. It is much more fragile and easily broken than pottery is, and it would not be considered a reasonable competitor for a moment except for its beauty. Glass has a certain transparency, and the presence of impurities (sometimes deliberately added) can give it deep and lovely colors. The earliest glass objects known were found in Egyptian tombs dating back to 2500 B.C., but they were simply ornaments. Not for another thousand years was glass used for vessels.
rFlight
1809 A.D.
UNITED KINGDOM
The dream of active flight had exercised the human imagination for millennia.
Usually, however, human beings could only think of imitating the birds. The Greek myth of Daedalus had that legendary inventor building a frame to which he stuck feathers in wax and which he moved in birdlike fashion with his arms.
The first person to consider the principles that would really keep objects in the air was a British scientist, George Cayley (1773-1857). He visualized flying devices with fixed wings that presented appropriate surfaces to the air, tails with control surfaces to allow turning and braking, and propulsive mechanisms. He described all this in publications that began to appear in 1809.
In these he founded the science of aerodynamics. While the state of technology at that time did not allow the construction of such devices, when they did come a century later, they fulfilled Cayley's requirements.
Balloons had been in existence for 70 years, proving that objects that were themselves denser than air could remain aloft under proper conditions of winds and updrafts, but Cayley was the first to study, scientifically, the conditions under which air might keep a heavier-than-air object aloft. He thus founded the science of aerodynamics. He realized that what was needed were fixed wings, like the flaps of a flying squirrel, rather than moving wings, like those of birds.
He worked out the basic shape that airplanes would eventually have -- wings, tail, streamlined fuselage, and rudder. He also realized that he needed an engine and propeller to be able to proceed against the wind, but he knew that no engine then existing would be light and powerful enough to do so.
In 1853 he built the first device so constructed aerodynamically as to glide with the wind and lift with the updrafts -- a glider, as it came to be called. Cayley, too old to take the risk, ordered his coachman to take the first glider flight. The coachman did so, vehemently objecting, flew 500 yards, and survived. Over the second half of the nineteenth century, glider-flying became a popular sport, as balloon-flying had been in the first half.
°The First Glider
1853 A.D.
ENGLAND
Balloons had been in existence for 70 years, proving that objects that were themselves denser than air could remain aloft under proper conditions of winds and updrafts.
Nevertheless, the English engineer George Cayley was the first to study, scientifically, the conditions under which air might keep a heavier-than-air object aloft. He thus founded the science of aerodynamics. He realized that what was needed were fixed wings, like the flaps of a flying squirrel, rather than moving wings, like those of birds.
He worked out the basic shape that airplanes would eventually have -- wings, tail, streamlined fuselage, and rudder. He also realized that he needed an engine and propeller to be able to proceed against the wind, but he knew that no engine then existing would be light and powerful enough to do so.
In 1853 he built the first device so constructed aerodynamically as to glide with the wind and lift with the updrafts -- a glider, as it came to be called. Cayley, too old to take the risk, ordered his coachman to take the first glider flight. The coachman did so, vehemently objecting, flew 500 yards, and survived. Over the second half of the 19th century, glider-flying became a popular sport, as balloon-flying had been in the first half.
Liquid-Fuel Rockets
1926 A.D.
WORCESTER, MASSACHUSETTS
The Chinese had made use of rockets in the Middle Ages, and English scientist Isaac Newton, with his law of action and reaction, had shown that rockets were one way of traveling through outer space. Until the twentieth century, however, rockets had made use of gunpowder as the fuel and had depended on the atmosphere for oxygen.
A crucial change was introduced by the American physicist Robert Hutchings Goddard (1882-1945). He had been interested in rocketry since his teens, and it occurred to him that a rocket would be more powerful and under better control if it made use of a liquid fuel such as gasoline and carried its own oxidizer in the form of liquid oxygen.
On March 16, 1926, Goddard fired his first liquid-fuel rocket. It was about 4 feet high, 6 inches in diameter, and was held in a frame like a child's jungle gym. It rose 200 feet into the air. It didn't seem like much, but that little rocket marked the first step in the expansion of the human range beyond the atmosphere.
ΦGodel's Theorem
1931 A.D.
AUSTRIA
Thirty years earlier, Frege had attempted to place all of mathematics on a formal logical basis, making it fully rigorous, and had failed.
Other, more elaborate attempts followed.
An Austrian mathematician, Kurt Gödel (1906-1978), put a final end to such schemes in 1931 by advancing what is now called Gödel's proof. He translated the symbols of symbolic logic into numbers in a systematic way and showed that it was always possible to construct a number that could not be arrived at from the other numbers of his system.
What it amounted to was this: Gödel showed that if you began with any set of axioms, there would always be statements within the system governed by those axioms that could be neither proved nor disproved on the basis of those axioms.
If the axioms were modified in such a way that the statement could be either proved or disproved, then another statement could be constructed that could be neither proved nor disproved in the new system, and so on forever.
Gödel had thus ended the search for certainty in mathematics by showing that it did not and could not exist, just as Heisenberg had in physics.
However, Gödel's proof does not affect the nitty-gritty of ordinary mathematics. Two plus two is still four.
ªMedieval Alchemy
1597 A.D.
GERMANY
The medieval alchemists didn't achieve much of what they would have liked to achieve. They didn't manufacture gold out of lead, and they didn't find the elixir of life. However, they weren't totally useless, either.
In 1597 a German alchemist, Andreas Libau (ca. 1540-1616), better known by the Latinized form of his name as Libavius, wrote a book entitled Alchemia in which he summarized medieval achievements in alchemy. It was the first chemical textbook worthy of the name. Libavius wrote clearly rather than mystically. He was the first to describe the preparation of hydrochloric acid, and he gave clear directions for preparing other strong acids such as sulfuric acid and aqua regia ("royal water," a mixture of sulfuric and nitric acids that was so powerful it would even dissolve the royal metal, gold).
With Libavius's book, the stage was set for the birth of real chemistry two- thirds of a century later.
'Improving Rubber
1839 A.D.
UNITED STATES
Rubber had come to the attention of Europeans when explorers found Native Americans using it. It was obtained from the sap of a tree originally native to tropical America but since grown in southeastern Asia and in other places as well.
Rubber was recognized as a useful waterproofing material, since it was impervious to water and wasn't rotted by it either. The trouble was, though, that when it grew cold, it stiffened and became brittle, and when it grew hot, it became soft and sticky. Attempts were made to find ways of making rubber less sensitive to temperature change, but at first there was only failure.
Then, in 1839, the American inventor Charles Goodyear (1800-1860) had a stroke of luck. He was trying to add sulfur to rubber when some of the mixture came accidentally into contact with a hot stove. To Goodyear's astonishment, those portions that weren't scorched too badly became dry and flexible, and they didn't lose flexibility in the cold or dryness in the heat. He began to heat the rubber-sulfur mixture to higher temperatures than anyone else had tried and thus obtained vulcanized rubber (after Vulcan, the Roman god of fire).
It was only with this discovery that rubber became truly useful, far more useful eventually than anyone might have suspected in Goodyear's day.
;Curving Light
1919 A.D.
GERMANY
Einstein had advanced the theory of general relativity, which among other things predicted that light rays would bend slightly and follow a gently curved path when in a gravitational field. The one way of testing that would be to study the stars in the immediate neighborhood of the Sun during a total eclipse, but astronomers had to wait for the end of World War I to make an eclipse expedition feasible.
On May 29, 1919, a solar eclipse was scheduled to take place at just the time when more bright stars would be in the vicinity of the eclipsed Sun than would be there at any other time of the year.
The Royal Astronomical Society of London, under the leadership of Arthur Stanley Eddington (1882-1944), who was a great enthusiast of Einstein's theories, made ready two expeditions, one to northern Brazil and one to Principe Island in the Gulf of Guinea off the coast of West Africa. The positions of the bright stars near the Sun were measured relative to each other at the time of the eclipse. If light was bent in its passage near the Sun, those stars would all seem to shift away from the Sun and would appear to be slightly farther apart from each other than they would six months earlier or six months later when they rode high in the midnight sky.
The positions of the stars proved to be in line with what Einstein had predicted, and this was considered a grand verification of general relativity.
However, the measurements were borderline and a trifle uncertain, and none of the tests of general relativity were entirely conclusive for an additional 40 years, so that a number of other types of cosmological theories were advanced to compete with that of Einstein. (On the other hand, special relativity was confirmed over and over, and there has been no reasonable doubt concerning it for three-fourths of a century.)
Universal Gravity
1687 A.D.
CAMBRIDGE, ENGLAND
From the laws of motion, English scientist Isaac Newton was able to deduce the manner in which the gravitational force of attraction between the Earth and the Moon could be calculated. He showed that it was directly proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between their centers. The proportionality could be made an equality by the introduction of a constant. In other words: F = gmm'/d squared. where g is the gravitational constant, m and m' are the masses of the Earth and the Moon, d is the distance between their centers, and F is the force of gravitational attraction between them.
Most important of all, Newton postulated that this law of gravitational attraction held not only between the Earth and the Moon, but between any two bodies at all throughout the Universe. It was not merely gravitation he was speaking of, but universal gravitation. This was another claim that the laws of nature were the same everywhere and the mightiest blow yet against the view that the heavenly bodies worked by some set of natural laws other than those that prevailed on Earth.
From this rather simple law of universal gravitation, all of Kepler's laws of planetary motion could be derived. It accounted for all the irregularities of planetary motion known in Newton's time, for while the Sun was the predominant attractive body, the planets had minor attractions for each other that resulted in slight alterations (perturbations) of their orbits from what they would be if the Sun alone were involved.
What Newton had done was to describe the machinery of the Universe effectively and to show that it was essentially simple. Despite the fact that forces other than gravitation are known today, and that Newton's description of gravitation has been refined since, it still remains true that gravitation is the overriding force that controls the great sweeps of the Universe, and that Newton's formulation is an excellent one if distances and velocities are not too great.
(The Great Wall
214 B.C.
CHINA
From its earliest history, China found itself threatened by the nomads of central Asia, who were only too ready to raid the hard-working Chinese peasantry and carry off their crops for food and them for slaves.
It struck Shih Huang Ti that the best thing to do would be to build a wall across the countryside, a large wall, tall and wide, not so much to keep the nomads out, as to keep their horses out. The nomads were helpless without their horses, and though human beings may climb even a difficult wall, a horse cannot. This wall was begun in 214 B.C. Initially it was of earth, but later it was made of brick. It eventually extended for 1,500 miles, from the Pacific Ocean to a point deep in central Asia. It had periodic watchtowers, and on the whole it did its job. China was not made invulnerable by the Great Wall but it was surely made less vulnerable.
The Great Wall is the largest construction project ever carried out, the only object made by human beings that outdoes the pyramids (which were, to be sure, built 25 centuries earlier).
OGreek Fire
673 A.D.
CONSTANTINOPLE
The Arabs, emerging from their peninsula, began an amazing series of conquests that in the space of 50 years seemed to bring to life again the old Persian Empire with Arabia and North Africa added. Nothing more seemed needed but the city of Constantinople itself before all the European dominions of the old Roman Empire would fall. In 673 the Arab army was just across the Hellespont from Constantinople, and their fleet was offshore. It seemed that nothing could possibly save the city.
There was in the city, however, an alchemist named Callinicus (7th century), of Egyptian or Syrian birth, who had arrived in Constantinople as a refugee. He had invented a mixture containing naphtha, plus potassium nitrate and calcium oxide, perhaps (we don't know the exact recipe), which not only burned but would continue to burn on water even more fiercely. This Greek fire was spurted out of pipes into the paths of the wooden ships of the Arabs. The fear of being set on fire, and the horror of watching fire burn on water, forced the Arab fleet to retreat and Constantinople was saved.
VThe Greenhouse Effect
1988 A.D.
EARTH
It had been known since 1884, when Swedish chemistry student Svante August Arrhenius (1859-1927) had pointed it out, that carbon dioxide in the atmosphere acted as a heat trap, making Earth's temperature warmer than it would otherwise be. (This was called the greenhouse effect.)
It was also known that the carbon dioxide content of the atmosphere had been rising steadily since 1900, partly because of the increasing use of coal and oil, which produce carbon dioxide when burned, and partly because of the cutting down of forests, which are the most efficient consumers of carbon dioxide.
As it happened, 1987 was the warmest year yet recorded by weather bureaus, and 1988 was warmer still. What's more, 1988 saw disastrous droughts in the United States and elsewhere. There was a feeling that the greenhouse effect was intensifying, and world concern began to intensify accordingly.
Rising temperatures would not only alter Earth's climate (probably for the worse) but could promote the melting of Earth's ice caps to produce a disastrous rise in sea level of up to 200 feet. The greenhouse effect, plus the thinning of the ozone layer, the steady rise in environmental pollution, and the inexorable increase in population, seemed to have placed the very habitability of our planet at risk, and a sense of crisis was beginning to pervade the world.
─The Gregorian Calendar
1582 A.D.
GERMANY
The Julian calendar, adopted by Julius Caesar, was not quite correct. It assumed a year that was 365.25 days long, but the year was more nearly 365.2422 days long.
If the year were exactly 365.25 days long, that extra quarter-day could be made up for by adding an extra day every fourth year. Then every fourth year would be 366 days long (leap year), and in the space of 400 years there would be 100 leap years.
A year that is 365.2422 days long is about 365-97/400 days long. This means that there should be only 97 leap years every 400 years, not 100. By the Julian calendar, 3 days too many were added every 400 years, and the vernal equinox fell earlier and earlier. If the vernal equinox was on March 21 when the Julian calendar was established, then by 1582 it would fall on March 11, 10 days too early.
The church was very involved in this because the holy days depended on the calendar, and if the drift continued, Easter would eventually come in winter and Christmas in the autumn. However, earlier attempts to reform the calendar had failed, for people are conservative about such things.
By 1582, however, the situation had come to seem intolerable to the church. The Bavarian astronomer Christoph Clavius (1537-1612) worked out a scheme for a more correct calendar and Pope Gregory XIII (1502-1585) adopted it. On October 4, 1582, 10 days were dropped and the next day was October 15. Thereafter, any year that ended in 00 but was not divisible by 400 was not a leap year. Thus 1600 was a leap year, but 1700, 1800, and 1900 were not leap years. However, 2000 will be a leap year. In this way, there are only 97 leap years every 400 years.
Catholic Europe adopted the Gregorian calendar (named in the Pope's honor) almost at once. The new Protestant states were more reluctant, preferring to disagree with the Sun rather than agree with the Pope. Great Britain didn't adopt the new calendar for two centuries; Russia, for three and a half centuries.
╕Group Theory
1830 A.D.
FRANCE
In mathematics it is possible to do a great deal in a short life. The French mathematician Évariste Galois (1811-1832) was killed in a duel before his 21st birthday. Even so, he managed to generalize the work of Abel, who had shown the impossibility of solving equations of the fifth degree by algebraic methods.
Galois went on to show that no equation of any degree higher than the fourth could be so solved. In order to do this, he invented a mathematical technique called group theory, which turned out to be useful a century later in working out quantum mechanics, one of the two great physical theories developed in the twentieth century that successfully describe the Universe.
╟Great Lakes
1990 A.D.
USA
Below you are the Great Lakes of the United States and Canada. The border between the United States and Canada runs down the middle of Lake Superior, a giant body of water larger than several states.
To the right of Lake Superior are lakes Michigan, Huron, Erie and Ontario.
At the south tip of Lake Michigan is the city of Chicago, Illinois, a communications center through which roads, railroads, airports serve the midwestern United States.
>The Nature of Mass
1891 A.D.
HUNGARY
Newton had defined mass in terms of the amount of acceleration produced in a body through the application of a force of a given magnitude. This is called the inertial mass, because the greater the mass of a body, the less acceleration a given force produces and the greater the inertia (the resistance to a change in velocity).
Newton also found that the intensity of an object's gravitational field at a given distance depended upon its mass. That is the gravitational mass.
These two kinds of mass were determined by two entirely different kinds of observations and would seem to have no necessary connection, yet the mass determined by inertial effects always seemed to be the same as the mass determined by gravitational effects.
A Hungarian physicist, Roland Eötvös (1848-1919), saw that if the gravitational mass and the inertial mass were truly identical, then objects in a given gravitational field would always drop (in a vacuum) at the same rate, regardless of mass. He made particularly delicate measurements in 1891 and found that objects of different mass fell at the same rate within five parts per billion. If there was a difference between the two kinds of mass, it was extremely tiny.
This measurement turned out to be very important later in the development of a new and better way of looking at gravity.
XAir Pressure
1654 A.D.
GERMANY
German physicist, Otto von Guericke (1602-1686), having invented the air pump, used it to demonstrate the power of air pressure, beginning in 1654.
For instance, he affixed a rope to a piston and had 50 men pull on the rope while he slowly created a vacuum on the other side of the piston within the cylinder. Air pressure inexorably pushed the piston into the cylinder despite the struggles of the 50 men to prevent it.
Then he prepared two metal hemispheres that fitted together along a greased flange. (They were called Magdeburg hemispheres because Guericke was mayor of Magdeburg.) When the hemispheres were put together and the air within them evacuated, air pressure held them together even though teams of horses were attached to the separate hemispheres, straining to their utmost in opposite directions. When air was allowed to enter the joined hemispheres, they fell apart of themselves.
This demonstration took place before the eyes of Ferdinand III (1608-1657), who became Holy Roman Emperor in 1637. He was so impressed, he ordered Guericke's work to be written up and published.
The Gulf Stream
1770 A.D.
GULF OF MEXICO
There are currents in the water that are as important to navigation as the winds are, though they are less noticeable.
Franklin had traveled from America to Europe several times and his ever-inquiring mind became aware of the difference in speed in the two directions. He was the first to study ships' reports seriously and to query the experience of whalers. As a result he found that there was a current of warm water coming up from the Gulf of Mexico (the Gulf Stream) and then crossing the North Atlantic toward Europe. It sped the ships sailing eastward to Europe and slowed those sailing westward to North America. Franklin mapped it and in this way showed British navigators the routes to avoid if they wished to make good time westward. This was the beginning of the scientific study of ocean currents.
Water currents did not concern only navigators. Labrador and Great Britain are at precisely the same latitude on opposite sides of the North Atlantic Ocean. However, the Gulf Stream, a warm-water current, bathes the British coasts, while a cold-water current from the Arctic bathes the Labrador coast.
For that reason, Great Britain has a mild climate and is populated by tens of millions, while Labrador is frigid and is populated by tens of thousands.
ï Printing
1454 A.D.
GERMANY
There is no way to overestimate the importance of writing. Nevertheless, it can't be denied that writing is a tedious process, and there have always been efforts to hasten it. The Egyptians worked out faster ways of scrawling their complicated symbols, and the Romans worked out systems of shorthand.
The ancient Sumerians, however, developed little cylinders of hard stone with designs incised into them that could be rolled onto soft clay so that the designs were impressed, and these could be made permanent by baking. The cylinders could be used over and over again and served as a signature for the owner.
Why could not the same system be used for pressing symbols onto a sheet of paper? If a block with a raised reversed symbol on it is smeared with ink, it can press an inked symbol (nonreversed) onto paper. The Chinese started doing this about the year 350, and by 800 they were carving entire pages on wooden blocks. Such a page could then be printed any number of times, all the impressions being exactly alike. But then, it took a long time to carve the wooden block into a bas-relief with all the symbols perfectly formed.
Later the Chinese got the idea of using a different block for each symbol, so that the blocks could be arranged into any desired combination to give any desired page. By 1450 they had movable wooden characters of this type, and by 1500 they were making use of metal characters.
By then, though, the Europeans had out-stripped them (though it is possible that news concerning movable type had reached Europe from China and given the Europeans a head start).
The German inventor Johannes Gutenberg (ca. 1390-1468) had been working out the matter of movable type since 1435. He had paper to work with (it had long ago reached Europe from China) and he experimented with different inks. He also designed a printing press, a device that would press the paper down on all those little metal characters evenly.
By 1454 Gutenberg had worked out all the bugs in his process and was ready for the big task: he began to put out a Bible, in double columns, with 42 Latin lines to the column. He produced 300 copies of each of 1282 pages and that produced the 300 Gutenberg Bibles. It was the first printed book, and many people consider it the most beautiful ever produced -- so that the art was born at its height. The Gutenberg Bibles that remain today are the most valued books in the world.
(Gyroscopes and Compasses
1852 A.D.
PARIS, FRANCE
Just as a pendulum has the ability to swing in an unchanging plane, so does a massive sphere in rotation have a tendency to maintain the direction of its axis of spin (as the Earth itself does). Jean Foucault, who had made an amazing demonstration with a pendulum, now demonstrated the matter of the rotating sphere, by setting a wheel with a heavy rim (a gyroscope) into rapid rotation. It not only maintained its axial direction, but when it was tipped, the effect of gravity was to set up a motion at right angles that was equivalent to the precession of the equinoxes.
This meant that a gyroscope, maintaining its axial orientation, could be used as a steady indicator of true north, substituting for, and better than, the magnetic compass that had been in use for some six centuries.
╣The Haber Process
1908 A.D.
GERMANY
Nitrogen is absolutely essential to life, and also to explosives. Hellriegel had discovered that leguminous plants could fix atmospheric nitrogen and keep soil fertile, but that was a slow process and would not suffice for the manufacture of explosives in the quantities that a war economy required.
Nitrogen in its most usable form exists in nature as nitrates in the soil. Nitrates are therefore sought after, both for fertilizers and for explosives. Nitrates, however, are uniformly soluble and tend to be leached out of the soil by rainfall. One can therefore expect a reliable source of nitrates to be found chiefly in desert areas such as those in northern Chile.
Germany, anticipating possible war with Great Britain, knew that British control of the seas would prevent Chilean nitrates from reaching Germany, reducing Germany's ability to fight a long war. German chemists were therefore encouraged to find an alternate source for nitrates.
The German chemist Fritz Haber (1868-1934) sought a way of fixing atmospheric nitrogen in the laboratory. He found that if he placed a mixture of nitrogen and hydrogen under high pressure, in the presence of iron as a catalyst, he could manufacture ammonia. From ammonia, it was easy to obtain nitrates. By 1908 he had perfected the method and provided a source of home- grown (so to speak) affordable nitrates.
This Haber process made it possible for Germany to fight long wars -- unfortunately.
╝Hafnium
1923 A.D.
DENMARK
Hevesy, who had introduced the notion of radioactive tracers, managed to reduce further the small number of still-missing elements. In collaboration with a Dutch physicist, Dirk Coster (1889-1950), Hevesy used an X-ray analysis method worked out by Coster and discovered hafnium, from the Latin name for Copenhagen. It is not a particularly rare element, but it is very like zirconium, which is just above it in the periodic table, and it is never found except in association with zirconium, which is 50 times as common, so that hafnium is hard to separate out.
Hafnium has an atomic number of 72, and its discovery reduced the number of still-missing elements between 1 and 92 to five.
Æ Hahnium
1967 A.D.
BERKELEY, CALIFORNIA
In 1967 the formation of element number 105 was reported in the United States, and it was named hahnium, after Otto Hahn.
½Halley's Comet
1986 A.D.
LONDON, ENGLAND
Halley's comet returned for the third time since Halley had first worked out its orbit. Its appearance in 1986 was unfortunately not a showy one, since it remained rather far from Earth even at its closest approach and could only be seen high in the sky from the southern hemisphere.
It was an unprecedented return, however, since it could now be studied by probes sent out by the Soviet Union and by the European Space Agency. The European probe, named Giotto (after the painter who had been the first to paint the comet realistically), made the closest approach.
Comets had been pictured as "dirty snowballs" by Whipple, and he was shown to be right, but Halley's comet turned out to be far dirtier than expected. While it lost ice each time it approached the Sun, it lost rocky particles to a much smaller extent and they accumulated on the surface, forming a kind of crust, through which the vapors formed by heated ice broke through at weak spots here and there. The result was that Halley's comet was dark black in color.
This meant it was larger than expected. Since it reflected so little light, a larger surface was required to produce its observed brightness.
ÆMuscles and Bones
1680 A.D.
ITALY
There has been a continuing struggle between those who feel that life is something fundamentally different from nonlife and obeys different laws of nature (vitalism), and those who believe that one set of natural laws governs everything, life and nonlife alike. Generally, over the last three centuries, victory has come to the latter group.
Thus, in 1680 the Italian physiologist Giovanni Alfonso Borelli (1608-1679) posthumously published a book, De Motu Animalium (Concerning Animal Motion), in which he successfully explained muscular action on a mechanical basis, describing the actions of bones and muscles in terms of a system of levers. The laws that applied to inanimate levers also applied to our bone-muscle systems. (Of course, the bone-muscle action is one of the simplest aspects of life. Things got much more difficult as scientists tried to deal with the more complex aspects of life.)
k Circulation of the Blood
1628 A.D.
NETHERLANDS
The idea of the Greek physician Galen (129-ca. 199) that the heart was a single pump and that there were pores in the thick muscular wall separating the right ventricle from the left ventricle was not universally accepted.
In 1242 an Arabic scholar, Ibn an-Nafis (d. 1288), wrote a book in which he suggested that the right and left ventricles were totally separate. Blood was pumped out of the right ventricle into arteries that led it to the lung. There, in the lungs, the arteries divided into smaller and smaller vessels, within which the blood picked up air from the lungs. The vessels were then collected into larger and larger vessels until they were brought back to the left ventricle from which the blood was pumped out to the body generally.
In this way, the double pump was explained. One pump was needed for the lungs and aeration; the other for the rest of the body. An-Nafis had grasped the lesser circulation. However, his book was not known to the West until 1924, and it had no effect on later developments.
In 1553 a Spanish physician, Miguel Serveto, known as Michael Servetus (1511-1553), published a book in which he too described the lesser circulation. The major part of the book, however, dealt with the Servetus's theological views, which were Unitarian. Servetus, having ventured into Geneva, which was ruled by his deadly enemy, John Calvin, was taken into custody and burned at the stake.
Calvin then attempted to destroy all copies of Servetus's book, and it wasn't till 1694 that some unburned copies were found.
In 1559 an Italian anatomist, Realdo Colombo (1516?-1559), became the third person to understand, independently, the lesser circulation. His work was the first to reach the medical profession, and it was much more detailed and careful than those of his two predecessors, so it is Colombo who gets credit for the discovery.
Then came the English physician William Harvey (1578-1657). He studied the heart carefully and noticed that each side had valves that allowed blood to enter each of the two ventricles but not to leave except by way of arteries. He also knew about the valves in the veins, since he had studied under Italian physician Girolamo Fabrici (1537-1619), who had discovered them. He experimented with animals, tying off a vein or an artery and noting that the blood piled up in a vein on the side away from the heart, but in an artery on the side toward the heart. It was clear to him that blood flowed away from the heart in arteries and back to the heart in veins.
By 1628, he had all the evidence he needed and he published a 72-page book in the Netherlands with the title De Motu Cordis et Sanguinis (Concerning the Motions of the Heart and Blood). In it, he advanced his findings concerning the circulation of the blood: It leaves the right ventricle, goes to the lungs, and returns to the left ventricle. It then leaves the left ventricle, goes to the body generally, and returns to the right ventricle to begin all over.
The book was received sourly by the medical profession, but Harvey lived long enough to see it accepted. His book represents the beginning of modern physiology.
{The Hawaiian Islands
1778 A.D.
HAWAII
Captain Cook, in his final voyage, explored the Pacific coast of North America north of California. This formed the basis for the later British claim to the region. In January 1778 he discovered the Hawaiian Islands, which he named the Sandwich Islands after John Montagu, fourth earl of Sandwich (1718-1792).
The earl of Sandwich was such an inveterate gambler that he had meat placed between two slices of bread so that he could eat with one hand and not be forced to leave the gaming table. It was in this way that the sandwich was invented. He was also one of the great anti-American "hawks" in the British government.
εHot Air Balloons
1783 A.D.
PARIS, FRANCE
Light objects can be borne on the air, as all of us observe in the case of small feathers, dandelion seeds, and so on. If objects are light enough, they needn't depend on wind and updrafts to remain in the air (or on muscular power as in the case of birds, bats, and insects). A light enough object can actually float in air, just as wood floats on water.
There are no known solids or liquids that are lighter than air, but some gases are. It occurred to two French brothers, Joseph-Michel Montgolfier (1740-1810) and Jacques-Etienne Montgolfier (1745-1799), that hot air expanded and was therefore lighter than an equal volume of cold air. If a quantity of hot air filled a light balloon, the hot air would float in the air and might have enough upward push to carry the balloon with it. In fact, if the balloon was large enough, there might be sufficient buoyancy to carry a human being upward.
On June 5, 1783, in the marketplace of their hometown, the brothers filled a large linen bag, 35 feet in diameter, with hot air. It lifted 1,500 feet upward and floated a distance of a mile and a half in 10 minutes. They went to Paris, and on September 19, they managed a flight of six miles before a crowd of 300,000 that included Benjamin Franklin.
The balloon carried up not only itself but a wicker basket in which were a rooster, a duck, and a sheep, which were not harmed. Finally, on November 20, a hot-air balloon carried into the air a French physicist, Jean Françcois Pilatre de Rozier (1756-1783), and a companion. They were the first aeronauts in history.
Meanwhile, a French physicist, Jacques-Alexandre-César Charles (1746-1823), having heard of the hot-air balloons, realized that hot air had comparatively little buoyancy and lost that little as it cooled, though a fire in the basket underneath might suffice to keep it warm for a while. The gas hydrogen, studied by British chemist Henry Cavendish (1731-1810), was much lighter than hot air and had much greater buoyancy. What's more, the buoyancy was permanent. On August 27, 1783, Charles constructed the first hydrogen balloon and subsequently used one to rise nearly 2 miles in the air.
In subsequent decades, ballooning became almost a craze, and it was also used for scientific purposes.
ΦThe Nuclear Fusion Bomb
1952 A.D.
KWAJALEIN ATOLL, MARSHALL ISLANDS
The American effort to produce a nuclear fusion bomb (hydrogen bomb) was successful. Hydrogen-2 fused at a lower temperature than hydrogen-1, and hydrogen-3 fused at a lower temperature still. Hydrogen-2 was a rare isotope of hydrogen, but there was enough present in the Earth's oceans to last humanity for billions of years. Hydrogen-3 was radioactive and had to be formed through nuclear reactions if enough was to be obtained for use. It was planned to fuse a mixture of hydrogen-2 and hydrogen-3 in liquid form by exposure to the temperatures and pressures produced by a fission bomb.
Such a fusion bomb was tested on a coral atoll in the Pacific Ocean on November 1, 1952, wiping out the atoll. The blast yielded energy equivalent to 10,000,000 tons (10 megatons) of TNT -- 500 times the 20-kiloton energy of the Hiroshima bomb.
Yet it did not give the United States security. Within a year, the Soviets had exploded a fusion bomb of their own. Both sides continually improved the efficiency and power of their fusion weapons, and Great Britain and China also acquired the technology. As Oppenheimer had foreseen in 1951, the world descended further into the abyss of fear, from which it has not yet emerged.
║Heart Transplants
1967 A.D.
SOUTH AFRICA
On December 3, 1967, the South African surgeon Christiaan Neethling Barnard (b.
1922) performed the first successful heart transplant in history. The patient received another person's heart and went on to live with it for an additional year and a half.
A period followed when heart transplants were performed in some numbers, but their benefits proved dubious and the ethical problems enormous. Their popularity subsided.
└Shaping the Earth
1752 A.D.
FRANCE
There is ample evidence that the Earth's surface has undergone enormous changes in its history, and there must be titanic forces behind those changes. Up to this time, most Europeans took it for granted that the causative factor was water and, in particular, the action of Noah's Flood, which was considered a God-caused cataclysm far more forcible than any natural flood could have been. Those who believed this were called Neptunists.
In 1752, however, a French geologist, Jean-Étienne Guettard (1715-1786), was convinced by his observations that the rocks he saw in central France had experienced great heat at some time in the past. This began the belief in heat as the causative factor.
AHeat and Radiation
1879 A.D.
AUSTRIA
An Austrian physicist, Josef Stefan (1835-1893), was particularly interested in how hot bodies cooled and, therefore, in how much radiation they emitted. He studied hot bodies over a considerable range of temperature and, in 1879, was able to show that the total radiation of a body was proportional to the fourth power of its absolute temperature (Stefan's law).
For example, if a body's temperature tripled, from 1,000 K to 3,000 K, its radiation output would increase 3 x 3 x 3 x 3, or 81 times. This very rapid increase of radiation with temperature was more of an increase than would have been expected and turned out to be of great use in deducing the evolution of stars. More immediately, from the total radiation of the Sun, its surface temperature was deduced from the rule, and turned out to be about 5,700 K.
The Heliocentric System
1543 A.D.
CRACOW, POLAND
The speculations of Aristarchus about a heliocentric (sun-centered) system in which the Sun was at the center of the Universe, with the planets, including the Earth, revolving about it, had been disregarded, and the geocentric system of Hipparchus and Ptolemy had been accepted without question.
However, the mathematics needed to work out the planetary motions on a geocentric basis was very difficult. While the Sun and Moon moved steadily west-to-east against the stars, the other planets occasionally reversed direction (retrograde motion) and grew markedly brighter and dimmer as they progressed across the sky.
The Polish astronomer Nicolaus Copernicus (1473-1543) thought, as early as 1507, that if one went back to Aristarchus's view and supposed that all the planets, including Earth, were moving about the Sun, it would become easy to explain retrograde motion. It would also be easy to explain why Venus and Mercury always remained near the Sun and why planets grew dimmer and brighter.
In addition to all this, the mathematics for working out planetary motions and positions would be simplified.
Copernicus did not, in his suggestions, abandon all Greek ideas. He clung to the notion that planets had to move in orbits that were circles and combinations of circles, and in this way he retained much unnecessary complexity.
The difference between Aristarchus and Copernicus was that Aristarchus merely presented his notion as a logical way of looking at the planets. Since others thought it wasn't logical, that ended it. Copernicus, however, used the Aristarchean idea to work out the actual mathematics of the planetary motions and show the reduction in complexity. This meant that even if people denied that the heliocentric system could be true, they would still be apt to use it as a simplified device for calculations.
Nevertheless, Copernicus hesitated to publish his theory and his computations, because he knew that the geocentric theory was felt by the Church to be in accordance with the Bible. To advance a heliocentric theory that would seem to be going against the Bible would surely create a storm. He therefore quietly circulated his book only in manuscript form.
Finally he let himself be persuaded by enthusiastic friends to have the book printed. It was entitled De Revolutionibus Orbium Coelestium (Concerning the Revolution of Heavenly Bodies). He dedicated it to Pope Paul III (1468-1549) as a placatory gesture, and then died. The story is that Copernicus was given the very first copy of his book on the day of his death.
As Copernicus had forseen, the book created a loud and violent storm. The Catholic Church put the book on its Index, forbidding the faithful to read it, and did not lift the ban till 1835. The Lutherans were equally hostile. The book could not be suppressed, however. With the coming of printing, far too many copies flooded the libraries of the scholars.
Copernicus's book totally overturned Greek astronomy, and though it was 50 years before astronomers generally could bear to turn their backs on Ptolemy and accept the fact that the vast Earth flew through space on an annual journey about the Sun, the book marked the birth of what came to be called the Scientific Revolution. With it came final proof that the ancients did not know it all and that moderns might strike out on their own in new directions and reach new heights -- and they certainly did.
It could be argued that just as printing made the Protestant Reformation possible, it also made the Scientific Revolution possible.
≈Helium, A Noble Gas
1868 A.D.
FRANCE
Improvements in transportation had made it possible for astronomers to travel all over the world if they had to. The most spectacular astronomical phenomenon that might be confined to a small area almost anywhere in the world was a total eclipse of the Sun. When an eclipse was due to be visible at certain areas in India in 1868, European astronomers didn't hesitate to make the journey.
A French astronomer at the site, Pierre-Jules-César Janssen (1824-1907), studied the spectra of the solar prominences.
Meanwhile, a British astronomer, Joseph Norman Lockyer (1836-1920), showed that by allowing light from the edge of the Sun to pass through a prism, he could obtain spectra of prominences even without an eclipse.
Janssen observed a spectral line that did not match any of the known lines in position. He sent a report on this to Lockyer, who decided that the line represented a hitherto unknown element. The element was named helium, from the Greek word for "sun." (Since then, a number of strange lines have been found in astronomical light sources, and other new elements have been postulated, but helium -- the first of these -- remains the only one to have proven truly a new element, though this was not proven until a quarter-century later.)
½Argon, A Noble Gas
1895 A.D.
ENGLAND
The time had passed when a new element could be discovered and then treated as though it existed all by itself. Mendeleyev with his periodic table had shown that elements existed in families.
Argon, discovered the year before by Rayleigh and Ramsay, did not fit in with any existing family, but it seemed to be in the neighborhood of chlorine and potassium as far as its atomic weight was concerned. Since the periodic table was based largely on valence, it made sense to put argon between chlorine and potassium. Chlorine and potassium each had a valence of 1, and since argon formed no combinations with other atoms at all, it had to have a valence of 0. The valence progression of 1, 0, 1 made sense, and argon would be the first member of a new family of elements of 0 valence.
In that case, where were the others? Ramsay made it his business to look for them. In 1895 he learned that in America, samples of a gas taken for nitrogen had been obtained from a uranium mineral. That looked hopeful, for the 0-valence gases could be mistaken for the rather inert nitrogen but for no other gas.
Ramsay repeated the work with a uranium mineral and got a gas that resembled nitrogen in its inertness. He tested the gas spectroscopically, however, and it did not produce the spectral lines of nitrogen. Instead it produced the spectral lines that Ramsay recognized as those detected by Janssen in sunlight.
Janssen's solar element had been named helium, and now Ramsay had identified it on Earth, and found that it would lie between hydrogen and lithium in the periodic table. As to what helium might be doing in the uranium mineral, that was a puzzle, but the answer was not long in coming.
!Gauss's Heptadecagon
1796 A.D.
GERMANY
Though Greek astronomy, physics, chemistry, medicine, and geography had all been replaced since the beginning of the Scientific Revolution, Greek geometry had remained staunch and firm.
In 1796, however, a young German mathematician, Carl Friedrich Gauss (1777-1855), worked out a method for constructing a heptadecagon (a polygon built up of 17 sides of equal lengths and sometimes called a seventeen- gon in consequence), using a compass and straightedge only. The Greeks had missed that construction, and Gauss's feat was considered the first notable addition to geometry since ancient times.
But Gauss did more than simply find a method of construction. He showed that only polygons of certain numbers of sides could be constructed with compass and straightedge alone. An equilateral heptagon (a polygon with seven equal sides) could not be constructed in this fashion. This was the first case of a geometric construction being proved impossible. From this point on, the proof of impossibility in mathematics grew increasingly important.
ùHero's Steam Engine
50 A.D.
ALEXANDRIA, EGYPT
Although Alexandria was now Roman and well past its great days, the Museum and the Library still existed, and a Greek engineer, Hero (1st century), worked there at about this time. Hero constructed a hollow sphere to which two bent tubes were attached, the openings pointing in opposite directions. When water was boiled in the sphere, the steam escaped through the tubes and, as a result of what we now call the law of action and reaction, caused the sphere to rotate rapidly. (The modern lawn sprinkler works in precisely this fashion, using the force of flowing water rather than steam.)
Hero had produced a steam engine. This does not represent the invention of the device, since it did not affect society. It is mentioned only as a curiosity and because it makes one wonder what might have happened if Greek science had continued unabated, uncrushed by the weight of Roman lack of interest.
╔The Photoelectric Effect
1887 A.D.
GERMANY
The German physicist Heinrich Rudolph Hertz (1857-1894) was interested in British mathematician James Clerk Maxwell's (1831-1879) equations. As part of his investigation of electromagnetic effects in the light of those equations, he set up an electrical circuit that oscillated. It surged alternately, first into one, then into the other of two metal balls separated by an air gap. Each time the potential reached a peak in one direction or the other, it sent a spark across the gap.
In the course of these experiments, Hertz noted that when ultraviolet light shone on the negative terminal of the gap, the one from which the spark issued, the spark was more easily elicited. This did not seem to have anything to do with what he was trying to observe, so he noted the matter but did not follow it up.
This was the first observation of the effect of light on electrical phenomena, however. This photoelectric effect turned out to be extremely important.
₧Multi-Dimensional Geometry
1843 A.D.
ENGLAND
Descartes had worked out an analytic geometry in two dimensions, expressing curves by algebraic equations. The British mathematician Arthur Cayley (1821-1895) wanted to extend this to higher dimensions, as Hamilton had extended imaginary numbers (also planar). In 1843 Cayley succeeded in working out analytic geometry in three or more dimensions. This would be called n- dimensional analytic geometry.
éHigh-Energy Phosphate Groups
1941 A.D.
U.S.A.
Harden had discovered the existence of phosphate esters in tissues, Metabolic Intermediates). Since then, Meyerhof and others had learned how the phosphate esters formed and how the phosphate groups were transferred from compound to compound in the course of metabolism.
In 1941 the German-born American bio-chemist Fritz Albert Lipmann (1899-1986) showed that there were two kinds of phosphate bonds. In one kind, the loss of the phosphate bond liberated a relatively small quantity of energy; in the other, the loss liberated a relatively large quantity. The latter esters possessed a high-energy phosphate.
In the course of carbohydrate metabolism, phosphate groups are added to sugar molecules forming a low-energy phosphate. The sugar molecule then undergoes the kind of change that concentrates the energy in the phosphate group, so that a high-energy phosphate is formed. These high-energy phosphate groups then serve as the "small change" of energy. In the simplest terms, food and oxygen combine to form high-energy phosphate bonds, which then deal out energy for all the energy-consuming functions of the body.
The most versatile of the high-energy configurations is a compound called adenosine triphosphate (ATP), each molecule of which contains two high- energy phosphates and which has been found to be concerned with body chemistry at almost every point where energy is required.
cThe Dirigible
1900 A.D.
GERMANY
Balloons had been in operation for over a century, and it was easy to see that if one could place a steam engine in a balloon's gondola and attach a propeller to it, the balloon might be guided in any desired direction, even dead against the wind. However, steam engines are very heavy, and supporting one by balloon would not be easy.
The coming of Otto's internal-combustion engine offered a much lighter energy source, but even so it was difficult to force a balloon through the air against air resistance.
It occurred to a German inventor, Ferdinand Adolf August Heinrich von Zeppelin (1838-1917), to streamline a balloon so that it would meet with less air resistance. This could be done by confining it within a cigar-shaped metal envelope. The Hall-Heroult method had made aluminum cheap, and aluminum had the combination of lightness and strength needed to make such a streamlined balloon feasible.
On July 2, 1900, one of Zeppelin's cigar-shaped vessels rose into the air. Beneath it was a gondola bearing an internal-combustion engine and a propeller. For the first time, an aircraft was not at the mercy of the wind but could move in any direction at will. It was called a dirigible balloon; that is, "a balloon that could be directed." This was soon abbreviated to dirigible, and the device was also sometimes called a zeppelin after its inventor.
öCAT Scans
1972 A.D.
GREAT BRITAIN
X-rays had been used in medical diagnosis for three-quarters of a century, but in all that time they had been used only to obtain a two-dimensional photograph of a three-dimensional body.
In 1972 a technique was introduced called computerized axial tomographic scanning (CAT scan), in which numerous X-ray "stills" were taken in such a way that they could be put together to form a three- dimensional image.
In another medical advance this year, the British surgeon John Charnley devised the first satisfactory plastic replacement for the fitting of the thighbone into the hip socket, thus preventing crippling through joint degeneration.
Holography
1965 A.D.
MICHIGAN
Gabor had worked out the theoretical basis of holography, a system of photography that recorded the interference patterns of an ordinary and a reflected beam of light. Holography made it possible to set up a real image in space, something that amounted to a three-dimensional photograph.
Once the laser had been invented and come into use, it proved an ideal light source for the purpose. In 1965 Emmet N. Leith and Juris Upatnieks, at the University of Michigan, were able to produce the first holograms.
nHome Photography
1888 A.D.
U.S.A.
Photography was now about half a century old, yet it remained almost entirely the province of experts and specialists, because it took considerable knowledge and skill to take and develop a photograph.
The American inventor George Eastman (1854-1932) simplified the process. He substituted a flexible film for the large and inflexible piece of glass on which photographic emulsion was spread and dried. With a film that could be rolled compactly, cameras could be made much smaller.
In 1888 Eastman developed a camera that weighed only about 2 pounds. He called it the Kodak, a meaningless name but one Eastman thought would be catchy and easily remembered. It had the film rolled up in it, and all the owner had to do was to point the camera, press a button, then send the camera to Rochester. Eventually, the photograph and the newly loaded camera were sent back. The Kodak slogan was "You press the button -- we do the rest." There were many improvements to come, but the Kodak started the process that allowed anyone and everyone to take photographs. The camera entered the home and began to make itself universal.
ÅHomo Habilis
1959 A.D.
TANZANIA
By now it was known that the two varieties of Homo sapiens, modern human beings and Neanderthal man, had been preceded by the smaller-brained Homo erectus, who may first have appeared on Earth as much as 1.5 million years ago. Before that there were various species of the genus Australopithecus.
The australopithecenes, whose existence seems to have overlapped that of Homo erectus, were hominids in that they more closely resembled human beings than they resembled any ape, living or extinct. Nevertheless, they were sufficiently primitive to be kept out of genus Homo. Did they develop directly into Homo erectus, or was there an intermediate form? The British anthropologist Louis Seymour Bazett Leakey (1903-1972), together with his wife, Mary, carefully explored the Olduvai Gorge in what is now Tanzania. There, on July 17, 1959, they came across the first fragments of a skull that, when pieced together, seemed to be a relic of the earliest known representative of genus Homo, a species that came into existence nearly 2 million years ago.
This species, intermediate between the australopithecines and Homo erectus, was eventually named Homo habilis (handy human). Homo habilis seemed to be the first hominid capable of shaping stone tools. Until then, all tools of earlier hominids, and of nonhominids for that matter, had been such things as leaves, twigs, shells, bones, and unmodified stones.
æHomologies
1555 A.D.
FRANCE
Anyone can see that living organisms can be grouped. Dogs and wolves resemble each other more than either resemble rabbits, for instance. Cats, lions, and tigers resemble each other. Sheep and goats resemble each other. Insects have a common resemblance that separates them from noninsects, and so on.
This might have given rise to evolutionary notions, that some basic doglike animal had given rise to both dogs and wolves, as an example. However, the Bible described all animals as being created simultaneously and separately, and it is possible to argue that God may just have decided to create animals in groups for his own purposes.
It would be more impressive if similarities could be found in more widely diverse organisms, similarities that were not too obvious to the eyes. This was done by a French naturalist, Pierre Belon (1517-1564).
Francis I of France (1494-1547) was engaged in a prolonged struggle with Charles I of Spain, who was also the Emperor Charles V. Francis was desperate enough to ally himself with the Ottoman Empire, and in 1546 he sent Belon on a diplomatic mission to the Ottomans.
This gave Belon a chance to study plant and animal life in the eastern Mediterranean and to compare it with life in France. He was the first to describe, in writings he published in 1555, basic similarities (homologies) in the skeletons of all vertebrates, from fish to humans.
Such details as the number of bones in the limbs were remarkably constant from animal to animal, regardless of the difference in outer appearance. This could not help but encourage evolutionary thought, although it was to be three centuries before it came to fruition.
7Wheeled Carts
3500 B.C.
SUMERIA (SOUTHERN IRAQ)
Where objects are too heavy to be carried by hand, transportation over land becomes a problem. Even where land is fairly smooth, there is considerable friction, whether the ground is sandy, pebbly, or grassy. Heavy objects had to be dragged on sledges by sheer force at first, and even when animals stronger than humans were used (oxen, for instance), it was slow going.
It could be made easier if crude rollers in the form of wooden logs were placed under sledges. The rollers turned rather than dragged, and that cut down on friction considerably. It meant less work, but might actually take more time, as rollers had to be picked up from the back and put down again in front. What is needed is an axle and wheels.
We don't know how someone came to think of attaching two rollers to the sledge back and front in such a way that they rolled inside the straps that held them and remained with the sledge at all times. At the end of each roller, solid wooden wheels were then placed to lift the sledge off the ground, and the wheels turned freely.
A wheeled cart moves more quickly and with far less effort than a sledge, even a sledge on rollers, so that such carts marked a revolution in land transportation. They made trade easier, for one thing.
Such carts had showed up in Sumeria by 3500 B.C.
qHorse Collars
900 A.D.
EUROPE
With moldboard plow and horseshoes, all that was needed to convert the horse into a farm animal was some good way of harnessing it.
In 900, or even some time before, the horse collar came into use. This allowed the horse to pull with the shoulder instead of the windpipe and increased the horse's available force fivefold.
Now, finally, the food supply and therefore the population began to increase in northern Europe. For the first time, power began to shift from the Mediterranean area, where it had been from the beginning of civilization, to the north -- a process that was to continue for nine centuries.
IHorseshoes
770 A.D.
EUROPE
Horses are by far the most useful animals. Strong and fleet, they were indispensable in war and could be indispensable on the farm if they could be used properly. A moldboard plow, cutting deep into heavy damp soil needs a strong pull.
One step forward was to take care of the horse's tender hooves, which could easily be hurt by rocks and pebbles. About 770, iron horseshoes were coming into common use, and that took care of that. What was still needed, however, was some method of harnessing that would allow a horse to pull hard without closing down its own windpipe.
ô Harnessing Horses
2000 B.C.
IRAN
Until now, the animals that had been used for pulling carts and ploughs were oxen and donkeys. The ox was strong, but it was lumbering, stupid, and slow. The donkey was more intelligent, but it was smaller and weaker than the ox. Neither could pull the heavy, solid-wheeled carts rapidly.
Animal transport could not be used in warfare with any great success, therefore. Armies consisted of masses of foot soldiers, who slogged into each other, wielding spears and swords and cowering behind their shields, until one side or the other broke and ran. The carts could serve only as a ceremonial means of keeping the ruler and other military leaders from walking, or to carry arms and supplies.
But then, about 2000 B.C., a fleet beast was tamed -- the wild horse -- and not by any of the civilizations but by nomadic dwellers in the steppes of what we now call Iran. The horse was larger and stronger than the donkey, and faster and more intelligent than the ox. At first, though, it seemed useless for transport, for it was difficult to harness. A harness that was suitable for an ox placed pressure on the horse's windpipe and cut its speed. Then, some time before 1800 B.C., someone devised a method of using the horse for specialized light traction. A cart was made as light as possible, becoming scarcely more than a small platform between two large wheels, a platform just large enough to hold a human being. Even the wheels were lightened, without loss of strength, by being made spoked rather than solid, and they were so fixed to the axle that they could turn individually. The result was a chariot (a word not too different from cart).
A horse, or horses, pulling so light a load could run fleetly, much faster than a foot soldier could. With only two wheels, the chariot was almost as maneuverable as the horse itself and could skid into a new direction with little trouble.
It did not take long for the nomads to discover that a body of charioteers, driving in fiercely, could not be stopped by the foot soldiers of the day. Indeed, foot soldiers broke and fled in horror at the first sight of the animals thundering toward them.
This is the first clear case we have of a new war weapon catching those without it by surprise and bestowing a kind of universal victory on those who had it. The raiding nomads ripped into the Tigris-Euphrates valley, which came under "barbarian rule" for a period of time. The nomads established the kingdom of Mitanni in what is now Syria and northern Iraq, and the Hittite kingdom in what is now eastern Turkey. In 1700 B.C., the horsemen drove down into Canaan and then even into Egypt, which fell to alien invaders for the first time, and also into India.
Such invasions spread devastation in the settled areas, but they did tend to stir things up. They helped change ways of life that had perhaps become somewhat decadent, and encouraged the flow of new ideas from one settled place to another.
\Heart-Lung Machine
1953 A.D.
U.S.A.
A heart-lung machine (or pump oxygenator) is one that takes venous blood from the veins, oxygenates it by mixing it with air, and pumps it back into the arteries, thus bypassing lungs and heart. It makes it possible to stop the heart and perform open-heart surgery without endangering the patient's life.
The first successful heart-lung machine, devised by John G. Gibbon of the United States, was used in 1953. Since then it has been repeatedly improved and is now used in the coronary bypass operations that are routinely performed to relieve the life-threatening agony of angina pectoris.
]Human Beings in Space
1961 A.D.
MOSCOW, USSR
The Soviet Union had put a dog into orbit four years before, where it was eventually put to death painlessly. A year before, the Soviet Union had put two dogs in space and brought them back alive. What followed was inevitable.
On April 21, 1961, Yury Alekseyevich Gagarin (1934-1968) was put into orbit by the Soviet Union in the spaceship Vostok I. He circled the Earth once in 89 minutes and was brought back alive. On August 6, 1961, a second Soviet cosmonaut, Gherman Stepanovich Titov (b. 1935), was put into orbit and circled the Earth 17 times, remaining in space for a full day.
≤Human Evolution
1871 A.D.
ENGLAND
Darwin, when writing his book on evolution, had deliberately refrained from discussing human evolution in order to avoid controversy. It was impossible, however, to suppose that biological evolution had shaped life in general but had somehow refrained from touching human beings.
It quickly turned out, then, that there was no point in ignoring the most important (to human beings) of all aspects of evolution.
Now, in 1871, Darwin published The Descent of Man, in which he applied the principles of evolution to humanity specifically. He pointed out the vestigial organs in man as evidence of descent from nonhuman animals: the trace of a point to human ears, the existence of useless muscles that once moved those ears, the four small bones at the bottom of the spine that were once tailbones, and so on. There were still no fossil remnants, however, that could give information as to the details of human ancestry. (Even the Neanderthals were too like ourselves to be useful in this respect.)
ÖCyclonic Storms
1831 A.D.
CONNECTICUT
An American meteorologist, William C. Redfield (1789-1857), traveled through Connecticut soon after a hurricane had ripped through New England on September 3, 1821. He noticed the manner in which the trees had fallen and deduced that, as the storm had traveled northeastward, the winds had spiraled.
He spent the next 10 years studying storms and in 1831 published his evidence to the effect that storm winds whirl counterclockwise around a center that moves in the normal direction of the prevailing winds.
Eventually it was discovered that this was true only in the northern hemisphere. In the southern hemisphere, storm winds whirl clockwise.
ñHydrogen and Water
1784 A.D.
ENGLAND
On January 15, 1784, Cavendish, still studying hydrogen, noted that if it was burned in a container, liquid drops appeared in the cooler portions of that container. On investigation, the liquid turned out to be water. The conclusion was that hydrogen combined with oxygen to form water. When Antoine Lavoisier heard that, he gave the gas its present name of hydrogen, from Greek words meaning "water-former."
Hydrogen
1766 A.D.
ENGLAND
Black's work with carbon dioxide had led to great interest in gases on the part of chemists. In 1766 the British chemist Henry Cavendish (1731-1810) found that some metals, when acted on by acid, liberated a gas that was highly inflammable and which he therefore called fire air. (We now call the gas hydrogen.)
Actually, early experimenters, notably Boyle, had obtained the gas, but Cavendish was the first to study it carefully and report on its properties, so he is usually given the credit for having discovered it.
Cavendish measured the weight of particular volumes of different gases in order to determine their densities. He found this new gas to be only one fourteenth the density of air, and no substance under ordinary conditions has ever been found to be less dense.
[Hydrogen in the Sun
1862 A.D.
SWEDEN
Once Kirchhoff had shown the use of spectral lines in determining the constitution of the solar atmosphere, astronomers began to compare the position of the dark lines in the solar spectrum with the lines produced by the elements.
In 1862 the Swedish physicist Anders Jonas Ångström (1814-1874) announced his discovery of hydrogen in the Sun. He went on, in later years, to publish a map of the spectrum in which he located about a thousand lines, measuring the wavelengths represented by each in units equal to a ten-billionth of a meter. That unit is still referred to as the angstrom.
èHydroxyls in Space
1963 A.D.
ITHACA, NEW YORK
Trumpler had shown that there were thin wisps of matter in interstellar space, and van de Hulst and Purcell had shown that hydrogen atoms were strewn across space.
It was reasonable to suppose that all this interstellar gas consisted of single atoms, since they would be spread out so thinly that the chances of collision would probably be too small to allow them to combine.
Yet suppose there were collisions. The three most common atoms are hydrogen, helium, and oxygen. Helium atoms don't combine with other atoms, but two hydrogen atoms might combine to form a hydrogen molecule, and a hydrogen and an oxygen atom might combine to form a hydroxyl group.
On Earth, a hydroxyl group is so active that it quickly combines with other atoms. The result is that such a group does not exist in the free state on Earth. In space, however, the chances of a hydroxyl group striking anything are so small that it might accumulate uncombined.
If so, hydroxyl groups ought to emit microwaves of characteristic wavelengths, and in 1963 two of those wavelengths were detected, indicating the presence of hydroxyl groups in interplanetary space.
kHypnotism and Mysticism
1774 A.D.
VIENNA, AUSTRIA
Throughout history, diseases had been cured (so it was said) by various mystic rites, by the laying on of hands, the saying of prayers, and so on.
In 1774 the German physician and mystic Franz Anton Mesmer (1734-1815) began to apply science to this by waving magnets over his patients, and effecting cures in some cases. Later, he discovered that magnets were unnecessary and that the same happy results could be achieved by simply passing hands over the patient. He claimed to be making use of animal magnetism.
Naturally, in some cases he did not effect a cure, and he was driven out of Vienna, where he first practiced, as a quack. He went to Paris, where again he was first popular and then forced to leave. His methods were examined by such men as Franklin and French chemist Antoine Lavoisier.
Franklin, for one, although he condemned Mesmer's mysticism, recognized that the mind influenced the body: that it could cause disorders and that it could be used to correct them.
What Mesmer was dealing with (without understanding it as well as Franklin did) were psychosomatic ailments, where often it is only necessary for patients to believe they will be cured in order to be cured. Mesmer's methods, refined and freed of some of their mumbo jumbo, became respectable half a century later as hypnotism, and some of them entered psychoanalysis later still.
┬Hypnotism
1841 A.D.
ENGLAND
Mesmerism had been debunked, but there were still those who practiced it as a form of show business. A British physician, James Braid (1795-1860), having witnessed an exhibition of mesmerism in 1841, investigated the matter and decided the phenomenon was real.
A person could indeed be put into a trancelike state resembling sleep by having the conscious mind forced into a state of weariness through repetitive stimuli. During such a state of quasi-sleep, the patient was extraordinarily open to suggestion and was relatively unresponsive to pain. Braid, avoiding the older name, called the phenomenon hypnotism, from the Greek word for "sleep."
It turned out to have its uses in medicine.
ôIntegrated Circuits
1960 A.D.
DALLAS, TEXAS
Since transistors had first been developed in 1948, they had been made steadily smaller, cheaper, and more reliable. By 1975 they had become so small, and the circuits upon them had been etched in so compact a manner, that they could be called microchips.
This meant that computers also could be made very small, very cheap, and very powerful. And this made possible personal computers, the first of which were introduced in 1975, foreshadowing the coming of word-processors and robots.
With the microchip, the computer was no longer suitable only for government and large industries. It began to invade the domain of the general public.
ïIcarus
1949 A.D.
ATHENS, GREECE
Witt had discovered Eros, an asteroid whose orbit carried it well within the orbit of Mars. Since then, a number of asteroids had been discovered that could approach Earth more closely than any planet did. These were called Earth-grazers. Some had been discovered that approached the Sun more closely than even Venus did. These were called Apollo-objects, after the first asteroid of this type, Apollo, which had been discovered in 1937.
In 1949 Baade, who had discovered the asteroid Hidalgo, discovered an asteroid that was an Earth-grazer, since it could come as close as 4,000,000 miles from Earth, and an Apollo-object too. Indeed, it approached the Sun more closely than Mercury did, skimming by at a distance of only 17,700,000 miles every 1.12 years. Baade named it Icarus, after the character in Greek mythology who lost his life when he flew on wax wings too close to the Sun.
uThe Ice Age
1837 A.D.
SWITZERLAND
For years, Swiss geologists, notably Venetz, had been pointing to evidence that the glaciers of the Alps had been more extensive in the past. A Swiss naturalist, Louis Agassiz (1807-1873), was among those who refused to accept these ideas -- until he himself began to study the evidence.
In 1837 he began to move ahead of those who had gone before him to postulate that ice sheets had covered far more than mountainous areas, having also spread over large sections of the lowlands in the northern portions of the continents. With time he found evidence of glaciation in Great Britain, and after he went to the United States to lecture (and decided to remain there), he found evidence of glaciation in North America.
In the end he drew a convincing picture of an Ice Age, a period in the past when millions of square miles of North America, Scandinavia, and Siberia lay under a thick ice sheet. This was the first intimation that uniformitarianism was not one long, steady progression without surprises. The coming and going of the ice sheets had to be a kind of catastrophe, though clearly it had not put an end to life.
▌The First Television
1938 A.D.
U.S.A.
The existence of the cathode ray tube had raised a new possibility.
If an electron beam could be made to pass over every part of a screen as the result of an appropriately varying magnetic field, and if the screen could be made to fluoresce appropriately, the electron beam could paint a picture, so to speak. The result would be what was eventually called a television screen.
The first practical television camera was constructed in 1938 by the Russian- born American engineer Vladimir Kosma Zworykin (1889-1982). He called it an iconoscope. The rear of the iconoscope was coated with a large number of tiny cesium-silver droplets. Each emitted electrons as a light beam scanned it, in proportion to the brightness of the light. The electrons in the television tube were controlled by the electrons in the iconoscope, so that the screen showed the same scene that entered the iconoscope.
Eventually, with improvements, the iconoscope made television a practical reality.
εImaginary Numbers
1685 A.D.
ENGLAND
Mathematicians knew that the multiplication of two negative numbers yields a positive product. Thus, not only does +1 x +1 = +1, but -1 x -1 = +1. What number, then, multiplied by itself yields -1? To put it another way, what is the square root of -1?
Mathematicians can invent the necessary number, call it an imaginary number, and symbolize it as i for imaginary. You can then say that +i x +i = -1. What's more, -i x -i = -1.
English mathematician John Wallis (1616-1703) succeeded in making sense out of such imaginary numbers in 1685.
Imagine a horizontal line. Mark off a point as zero and then imagine the positive numbers marked off to the right and the negative numbers marked off to the left, with all the fractions and irrational numbers appropriately marked off between the whole numbers. That is the real number axis.
Next, draw a vertical line passing through the zero point. Mark all the i numbers (i, 2i, 3i, and so on) upward, and all the -i numbers downward, with all the imaginary fractions and irrational numbers marked off, too. That is the imaginary number axis.
Every point in the plane can then be marked off just as French mathematician René Descartes (1596-1650) did in his analytical geometry. Every point (a) on the real number axis becomes a + 0i; every point (b) on the imaginary number axis becomes 0 + bi; and every number on neither axis (the complex numbers) becomes a + bi.
Such a scheme proved enormously useful to mathematicians, scientists, and engineers.
jImprinting
1935 A.D.
AUSTRIA
In 1935 the Austrian-born German zoologist Konrad Lorenz (1903-1989), a student of bird behavior, described imprinting. He showed that at a certain critical point in early life, soon after hatching, young birds learned to follow a moving object, usually their mother, who was sure to be in the neighborhood after all. If this for some reason was not the case, the hatchlings would follow some other adult bird or a human being or even a pulled inanimate object.
Once imprinting had taken place, it affected their behavior to some extent all their lives.
Lorenz thus established the science of ethology, the study of animal behavior in natural environments, and initiated the study of how learned behavior in very early life affected later events. For his work on animal behavior, he was awarded a share in the Nobel Prize for physiology and medicine in 1973.
wIndia
1990 A.D.
INDIA
At the upper edge of the Indian subcontinent you can see the Himalayan Mountains. In this range is Mt. Everest, at 29,028 feet above sea level, the tallest mountain in the world.
Though the mountains are tall, they have not always been tall enough to keep out invaders.
Thousands of years ago, starting with Aryan tribes from Central Asia, invaders have filed through the famous Khyber Pass in the northwest of this mountain range to conquer the land.
Though empires have risen and fallen here, India's major influence upon the world is undoubtedly religious. Here Hinduism was developed and is still powerful today, and from here (though it is no longer very influential in India) Buddhism had its start.
While Hinduism is not a major influence outside India, Buddhism is. Buddhism has become a major religious force throughout Southeast Asia and as far away as Japan.
RDa Gama Reaches India
1497 A.D.
INDIA
On July 8, 1497, the Portuguese navigator Vasco da Gama (1460-1524) set sail from Lisbon with four vessels. He rounded the Cape of Good Hope on November 22, passed the farthest point reached by Bartholomeu Diaz (1450-1500), sailed up the eastern coast of Africa, and finally reached Calicut, India, on May 20, 1498.
The deed was done. What Prince Henry the Navigator had begun was complete, nearly four decades after his death. The Portuguese had bypassed the Ottoman Empire and the Italian trading cities, such as Venice. From this point on, the Mediterranean region declined in power and wealth, and the Atlantic powers took the lead.
Da Gama's trip was the first one long enough to induce scurvy in his men. It was a debilitating disease that eventually killed those who suffered from it. Da Gama lost three-fifths of his crew to it.
¿Indium
1863 A.D.
GERMANY
A German mineralogist, Ferdinand Reich (1799-1882), suspected that a yellow precipitate he had obtained from a zinc ore might contain a new metal.
Because he himself was color-blind, Reich had his assistant, Theodor Richter (1824-1898), examine it spectroscopically. Richter did so and spotted an indigo-colored line that was not characteristic of any known element. The new element was therefore named indium.
cIndustrial Revolution
1790 A.D.
PAWTUCKET, RHODE ISLAND
Great Britain's economic position was improving enormously with its ingenious new textile machinery and the manner of powering it by steam. It was easy for the British leaders to see that if they could retain a monopoly on this Industrial Revolution, Britain might easily become the strongest power in the world -- economically, at any rate.
For this reason, what we would today call an "iron curtain" was clamped down. Blueprints of the new machinery were not allowed to leave the country, and neither were engineers who were experts in the new technology.
The new nation of the United States wanted the new technology to aid in its economic independence from Great Britain, without which its political independence wouldn't amount to much. It therefore did its best to steal the knowledge by encouraging defectors. It found its man in Samuel Slater (1768-1835).
Slater was an engineer who knew the new technology intimately, but who also knew that he could advance only so far in the class-ridden society of Great Britain. The United States was offering money for his knowledge and he decided to go for it. He couldn't take any blueprints with him, of course, so he painstakingly went about memorizing every detail of the machinery. He then disguised himself as a farm laborer and sneaked out of the country. In 1789 he arrived in the United States and made contact with rich merchants in Rhode Island.
In 1790, working from memory, Slater began building the first American factory based on the new machinery, in Pawtucket, Rhode Island.
In this way, the Industrial Revolution came to the United States, and once the process of proliferation began there was no stopping it. It continues to this day. Of course, when other nations try to make use of our technology in the same way that we made use of Great Britain's, we are, very naturally, indignant.
╩Libraries
640 B.C.
NINEVEH, ASSYRIA
Books, whether clay bricks covered with cuneiform or papyrus covered with hieroglyphics and rolled up (the word volume is from the Latin word for "to roll up") were hard to come by in ancient times. To get an additional copy of a book, it had to be copied over, stroke by stroke, by a meticulous and thoroughly literate scribe. Such copying took a long time and was hard work, so that books were both rare and expensive.
Only a few people could own books, and a library (from a Latin word for "book") consisting of several books must have been the mark of a rich man or the painfully accumulated store of a scholar. Only monarchs with the resources of kingdoms behind them could accumulate large libraries in the modern sense.
The first such monarch that we know of was Ashurbanipal. He arranged to have every book in his kingdom copied and the copy placed in his library at Nineveh. He ended up with thousands of books, all carefully cataloged.
Invisible Light
1800 A.D.
BATH, ENGLAND
It seemed natural to suppose that light, by its very nature, could be seen; light that could not be seen would be a contradiction in terms. Yet invisible light existed.
British astronomer William Herschel (1738-1822) in 1800 had formed a sunlight spectrum and tested different parts of it with a thermometer to see if some colors delivered more heat than others. He found that the temperature rose as he moved toward the red end of the spectrum, and it seemed sensible to move the thermometer just past the red end in order to watch the heating effect disappear.
Except that it didn't. The temperature rose higher than ever at a spot beyond the red end of the spectrum. The region was called infrared (below the red).
How to interpret the region was not readily apparent. The first impression was that the Sun delivered heat rays as well as light rays and that heat rays refracted to a lesser extent than light rays. A half-century passed before it was established that infrared radiation had all the properties of light waves except that it didn't affect the retina of the eye in such a way as to produce a sensation of light.
Herschel's discovery of infrared radiation naturally created a stir. German physicist Johann Wilhelm Ritter (1776-1810) was also studying the Sun's spectrum, but he was more interested in the chemical changes it brought about.
It had been known for nearly two centuries that light broke down the white compound silver nitrate, darkening it (by liberating tiny specks of metallic silver). This was first reported in 1614 by an Italian chemist, Angelo Sala (1576-1637).
Ritter soaked strips of paper in silver nitrate solution and placed them in different sections of the spectrum to see how rapidly they darkened. He found that the darkening was least rapid in the red end of the spectrum and took place faster and faster as one progressed toward the violet end. Ritter, perhaps influenced by Herschel's experience, proceeded to place strips of soaked paper beyond the violet end, where nothing could be seen. There the darkening proceeded faster still. Apparently, there was radiation beyond the violet end of the spectrum as well as beyond the red. The new radiation was called ultraviolet (the prefix ultra is from a Latin word meaning "beyond").
sThe Eustachian Tube
1552 A.D.
ITALY
Flemish anatomist Andreas Vesalius's (1514-1564) new anatomy spurred on the field generally.
The Italian anatomist Bartolommeo Eustachio (1520-1574) prepared a book on anatomy in 1552, nine years after Vesalius's. In some respects it was more accurate than the earlier book, but the illustrations were not as beautiful.
Eustachio described a narrow tube connecting the ear and the throat, which has been known as the Eustachian tube ever since, though it may have been discovered by a Greek physician, Alcmaeon (6th century B.C.), 2,000 years before.
Eustachio was also the first to describe the adrenal glands.
nIntegrated Circuits
1960 A.D.
WORLD
Transistors had been in existence for a dozen years, constantly being made smaller and more reliable. By 1960 they could be made so small that it made no sense to try to handle them as separate units.
Instead, small pieces of thin silicon or some other semiconductor, about a quarter-inch square, were etched with tiny transistor circuits. These chips did the work of many transistors and were called integrated circuits.
The use of integrated circuits made computers smaller, cheaper, and more versatile. As time went on, more and more circuits -- eventually thousands -- could be etched into a single chip.
≤Intelligence Quotients
1905 A.D.
FRANCE
While abnormal psychological phenomena have long interested physicians and scientists, the normal manifestations of the mind were what interested the French psychologist Alfred Binet (1857-1911).
He strove to devise tests that would measure the ability of the human mind to think and reason, independently of learning and education in one field or another.
To do this, he asked children to name objects, follow commands, rearrange disordered things, copy designs, and so on. In 1905 he and his associates published the first batteries of tests designed to measure intelligence.
Standards were set empirically. If a particular test was passed by some 70 percent or so of the nine-year-olds in the Paris school system, then it represented the nine-year-old level of intelligence.
The phrase intelligence quotient (often abbreviated IQ) became popular. It represents the ratio of the mental age to the chronological age, with 100 considered average. Thus, a six-year-old who can pass a ten-year- old's test has an IQ of 10/6 x 100, or 167.
Binet's initial efforts gave rise to batteries of tests designed to measure personalities, attitudes, aptitudes, and potentialities as well as intelligence -- and their value is almost certainly overestimated.
Internal-Combustion Engine
1860 A.D.
FRANCE
For a century and a half, steam engines had produced heat outside the system they were powering. Steam formed by the heat entered a cylinder and moved a piston.
What if a mixture of flammable vapor with air could be exploded within a cylinder? The force of this internal explosion would then move the piston directly. (The fuel would have to be a gas to begin with, or an easily evaporated liquid.) If such an internal-combustion engine were developed, it would be much smaller than a steam engine and so much more readily set into motion. After all, a vapor-air mixture will explode at the touch of a spark, while the initial boiling of water over a fire, in the case of the external-combustion steam engine, is a slow process.
A working internal-combustion engine was first constructed by a Belgian- born, French inventor, Jean-Joseph-Étienne Lenoir (1822-1900). In 1860 he hitched such an engine to a small conveyance and had a "horseless carriage." Horseless carriages run by steam had existed previously, but Lenoir's was more compact and more responsive to controls.
Nevertheless, Lenoir's internal-combustion engine was very inefficient. It was not till the next decade that an engine of this sort was built that was efficient enough for widespread use.
Iodine
1811 A.D.
FRANCE
A French chemist, Bernard Courtois (1777-1838), was in the business of manufacturing potassium nitrate (needed in gunpowder). He got it from potassium carbonate (potash), which in turn he got from seaweed. As one of the steps to get the potassium carbonate, he heated the seaweed in acid. One day in 1811 he added too much acid and, on heating, obtained a beautiful violet vapor. On condensing the vapor, he produced dark, lustrous crystals. He suspected it might be a new element and passed it on to other chemists for confirmation. It was a new element, and Davy suggested it be named iodine, from the Greek word for "violet."
Jupiter's Moons
1979 A.D.
HOUSTON, TEXAS
The probes Voyager 1 and Voyager 2 passed by Jupiter in March and July, respectively, of 1979. The most interesting result was that they gave humanity its first close look at the four Galilean satellites.
The satellites are subject to tidal heating from Jupiter, a heating that increases rapidly as distance from Jupiter decreases. Thus, Ganymede and Callisto, the outermost pair, are both covered with craters as might be expected and seem to be made up largely of icy material.
Europa, second-closest to Jupiter, is not cratered -- it has, in fact, the smoothest solid surface yet seen in the Solar System -- but cracked and criss-crossed with lines (rather like the old maps of Mars that showed the supposed canals). Apparently Europa is covered with a worldwide glacier that has liquid underneath. Any cosmic collision that might ordinarily cause a crater merely cracks the glacier, and the hole produced is then repaired by the formation of additional ice.
Io, the closest of the four satellites to Jupiter, has no water at all, the heating having driven it off. In fact, the inner heating produces active volcanoes, which the probes photographed in actual eruption. Sulfur dioxide exudes and breaks up into sulfur and oxygen. Io's surface is therefore covered by a yellow to red layer of sulfur, which fills in any but the most recent of craters. The eruptions also account for the thin gas that fills Io's orbit, forming a doughnut around Jupiter.
In addition to all of this, three more small satellites were discovered, all of them closer to Jupiter than any that had been discovered from Earth. This made 16 satellites all told for Jupiter. Finally, very close to Jupiter, a thin ring of debris was found, so that Jupiter joined Saturn and Uranus in being a ringed planet.
CThe Iron Age
1000 B.C.
ASIA MINOR
Iron is the second most common metal in the Earth's crust (only aluminum is more common), but it always occurs in combination with other substances. It is not found in free metallic form except in some meteorites, which are not of Earth but fall from the sky.
Such meteorites were occasionally found by the ancients and used even in the earliest days of civilization. Compared to gold, silver, and copper, iron is an ugly metal, but the meteoric iron that was found revealed itself to be harder and tougher even than bronze. Since it held its edge far better than bronze did, it was much in demand for edged portions of tools.
The result is that no iron meteorite from the past is ever found where the earliest civilizations flourished. The ancients scavenged them all.
Yet ores did not yield iron. Gold, silver, copper, lead, tin, and eventually mercury were obtained with ease by use of wood fires, but such fires never yielded iron. Iron held on to other substances more tightly than the other metals did, and a higher temperature was needed.
Eventually, though, charcoal was obtained by burning wood with an insufficient supply of air so that more-or-less pure carbon was left behind when other substances burned away. Charcoal burns flamelessly but reaches higher temperatures than wood does.
About 1500 B.C. the Hittites of Asia Minor found they could obtain iron from certain ores by heating those ores with burning charcoal. Iron was at first a disappointment. In pure form, it is tough but not as hard as the best bronze. (Meteoric iron is not pure iron but is a 9-to-1 mixture of iron and nickel, something the ancients couldn't duplicate since they knew nothing of nickel.)
By 1200 B.C., undoubtedly through hit-and-miss, it had been discovered that iron, properly smelted, could appear in hard form. This came about when some of the carbon in charcoal mixed with iron to form an iron- carbon alloy we call steel.
By 1000 B.C., such carbonized forms of iron could be formed in quantity and the Iron Age began, the period when iron was the chief metal used in arms and tools.
╣Irradiation
1924 A.D.
U.S.A.
Vitamin D is not often to be found, as such, in food. However, it was known that sunshine converted an inactive precursor in the skin to vitamin D. It followed that similar inactive precursors of vitamin D might exist in food, which exposure to sunlight (irradiation) might produce.
The American biochemist Harry Steenbock (1886-1967) showed in 1924 that this was, in fact, the case, and the use of irradiated food grew common.
δ Water and Governments
5000 B.C.
SUMERIA (Iraq)
Agriculture requires a steady supply of water to keep the plants alive, so it naturally started where rainfall could be counted upon to a reasonable extent. Rainfall, however, even at best, is a chancy thing, and droughts are all too common.
One reliable source of fresh water (the salt water of the sea won't work) is a sizable river. Farms therefore began to develop along riverbanks. Whereas rain falls directly on the crops, however, river water generally remains within its banks. In order to correct that situation, it is necessary to dig ditches so that water will flow outward from the river and soak the ground in which the plants are growing. These ditches have to be kept in order and not allowed either to silt up or to overflow.
What's more, when the river's water level falls during a drought, the ditches have to be dug deeper. And since the river occasionally rises in periods of heavier-than-usual rains (not necessarily at the site of the farms, but many miles away, nearer the river's source), levees have to be built to confine the rising water within the banks. These have to be tended continually to prevent leaks and breakdowns.
All this irrigation (from Latin words meaning "to water inward") more or less guarantees a good harvest and an ample food supply, at the cost of unremitting labor.
This labor cannot be done alone, nor can it be done by various people, each in his or her own way and at his and her own time. Irrigation requires cooperation. Many farms depend upon it, and the labor of many has to be supervised to make a coherent whole, so that the levees are in good shape everywhere.
As a result, the farms depend upon control by capable leaders who can supervise the work and allot the tasks, encourage the industrious and capable, and punish the idle or incompetent. In short, irrigation leads to the formation of what we call government, so that a cluster of farms surrounding a defensible city becomes a city-state, with a ruler and established rules of behavior.
The first such city-states formed along the lower courses of the Euphrates and Tigris rivers in what is now southern Iraq (but was then known as Sumeria) about 5000 B.C. Other city-states developed at nearly the same time along the Nile River in Egypt. It almost never rains in Egypt, but the Nile remains a reliable water supply and overflows regularly once a year when the rainy season takes place far to the south, nearer its source. The Nile flood deposits fertile mud over the farms on its banks.
┐Chemical Isomers
1823 A.D.
GERMANY
With the coming of the atomic view of matter, chemists routinely tried to find out the atomic composition of the molecules of the substances they were studying. In 1823 the German chemist Justus von Liebig (1803-1873) was studying a class of substances known as fulminates. Silver fulminate, for instance, has a molecule in which there is one atom each of silver, carbon, nitrogen, and oxygen.
At the same time, another German chemist, Friedrich Wöhler (1800-1882), was studying a class of substances known as isocyanates. Silver isocyanate also has a molecule containing one atom each of silver, carbon, nitrogen, and oxygen.
Both chemists submitted their reports for publication to a journal of which Gay-Lussac was editor. He noticed that the molecular formulas were the same, yet the compounds had quite different properties. He told Berzelius, who prepared both compounds and found that it was true: same formula, different properties. Berzelius referred to such unlike twins as isomers (from Greek words meaning "equal parts").
This was the first indication that counting the atoms in a molecule was not enough; it was also necessary to consider the arrangements of those atoms. The more complicated the molecule, the more likely it was that there would be numerous isomers. Since the molecules in living tissue tend to be far more complicated than the molecules in the inanimate world, isomerism became particularly important to organic chemists.
╦Nuclear Isotopes
1913 A.D.
ENGLAND
During the intense study of radioactive phenomena that had been going on for the previous 17 years, some 40 to 50 different elements had been reported (as judged by differences in radioactive properties -- the kinds, intensities, and energies of particles emitted). However, there were only 10 to 12 places available for them in the periodic table. Either the periodic table did not apply to radioactive elements or there was something subtle about those elements that had been missed.
The British chemist Frederick Soddy (1877-1956) worked on the problem.
He made clear what is now called the radioactive displacement law. (The Polish chemist Kasimir Fajans [1887-1975] made these same suggestions independently at about the same time.) When an atom gives off an alpha particle, the alpha particle has a positive charge of 2 and a mass of 4. The atom that gave it off therefore has to turn into another atom with a smaller charge (by 2) on its nucleus and a smaller mass (by 4).
When a beta particle is given off, with a negative charge of 1, the loss of the negative charge is equivalent to the gain of a positive charge. An atom that gives off a beta particle therefore turns into another atom with a larger nuclear charge (by 1). Since an electron has only a tiny mass, the mass of an atom is virtually unchanged in beta-particle emission.
A gamma ray, having neither electric charge nor mass, does not affect the nature of an atom when given off; it merely decreases the atom's energy content.
By following these changes, Soddy suggested that a given place in the periodic table might be occupied by two or more different substances, distinguishable from each other by their differing radioactive properties. These occupants of the same place would be equal in nuclear charge but different in mass. Soddy called them isotopes, from Greek words meaning "same place."
For his advancement of the isotope concept, Soddy was awarded the Nobel Prize for chemistry in 1921.
«Jacquard Loom
1801 A.D.
FRANCE
To weave textiles in such a way as to introduce patterns would ordinarily require people to work in a careful manner, producing certain motions here, but not there. It is not the sort of thing that one might think could be done by machinery. A machine wouldn't have the "brains" to do what human beings do only with difficulty.
In 1801, however, a French inventor, Joseph-Marie Jacquard (1752-1834), invented what came to be called the Jacquard loom. In such a loom, needles ordinarily move through holes set up in a block of wood.
Suppose a card containing holes in a certain pattern is interposed between the needles and the holes in the wood. Where there are holes in the card matching the holes in the wood, the needles pass through; otherwise, the needles are stopped. In this way, a card might enforce, quite automatically, just the type of needle motions that would produce a pattern. Different cards would produce different patterns.
To be sure, devising the punched card required considerable intelligence and ingenuity in the first place, but once the cards were designed and in place, the machine did not need brains; it worked automatically.
The Jacquard looms spread rapidly throughout France and eventually through Great Britain as well. The holes in the card were a primitive kind of yes-no mechanism; a century and a half later a much more subtle type of yes-no mechanism would serve as the basis for digital computers.
«Japan and Korea
1990 A.D.
JAPAN
Almost 150 years ago, Japan, the land of the rising sun, was isolated. Earlier the country had cut off contact with the outside world. But then American Commodore Matthew Perry, in search of new markets for American goods, forced the Japanese to open their ports. And considering it was forced to do so, Japan acted with surprising speed and enthusiasm.
From a society little removed from feudalism, Japan quickly rose to become a mighty military power that defeated the Russians, Chinese and Koreans. And during World War II the country engaged the United States in some of the most difficult battles it ever faced.
World War II was ended when American bombers dropped atomic bombs on Hiroshima and Nagasaki, near the south tip of the large island of Honshu.
Since its World War II defeat, Japan has risen again, but this time as a powerful economic nation.
The peninsula to the left of Japan is Korea, which has been divided into two halves following World War II. The north half was occupied by the Soviet Army and adopted communism, while the southern half was occupied by the United States and became capitalist and mostly democratic, though with instances of military rule.
0Vaccination
1796 A.D.
GLOUCESTERSHIRE, ENGLAND
Inoculation had been used to fight smallpox for some 80 years, but it was dangerous.
The English physician Edward Jenner (1749-1823) knew that in his native Gloucestershire there were tales to the effect that anyone who caught cowpox (a very mild disease, prevalent among cows, that somewhat resembled smallpox) was thereafter immune not only to cowpox but also to smallpox. (Since milkmaids almost invariably caught cowpox early and then never got smallpox, they retained a clear complexion. This in itself may have been enough to fuel the romantic cliché of the time concerning pretty milkmaids.)
Finally Jenner decided to test the matter. On May 14, 1796, he found a milkmaid who was undergoing an attack of cowpox. He took the fluid from a blister on her hand and injected it into an eight-year-old boy named James Phipps who, of course, got cowpox. Two months later, Jenner inoculated the boy with smallpox in the manner usual for those days. The boy did not get smallpox. Two years later, he found someone else with active cowpox and tried again. It worked this time also, and he felt it safe to announce his discovery. The Latin word for cow is vacca, so cowpox is vaccinia.
Jenner coined the word vaccination to describe his use of cowpox inoculation to create immunity to smallpox. In this way, he founded the science of immunology.
Such was the dread of smallpox that the new technique was instantly adopted and quickly spread all over Europe. It was the first case of a serious and frightening disease that could be reliably prevented.
iJet Plane
1941 A.D.
RUGBY, UNITED KINGDOM
During the 40-year history of air flight, planes had been propelled through the air by the aptly named propeller. There was no question, though, that a plane could also be made to move through the air, perhaps even more quickly and efficiently, by means of the rocket principle -- by burning fuel and ejecting a jet of exhaust gas at high speed (such planes are therefore called jet planes).
The advantage jet planes had over rockets such as those developed in 1926 by American physicist Robert Hutchings Goddard (1882-1945) was that they traveled through the atmosphere, so they needed to carry only fuel and could make use of the oxygen in the surrounding air as the oxidizer.
Plans for engines that made some use of the jet principle can be traced back to 1921, but the first patent for a jet engine of the type used today was obtained by a British aeronautical engineer, Frank Whittle (b. 1907), in 1930. The first jet plane making use of Whittle's engine was flown in May 1941. Jet planes were developed too late to play much of a role in World War II, but they came into their own afterward.
Conservation of Energy
1843 A.D.
GREAT BRITAIN
Some conservation laws had already been accepted by this time. French chemist Antoine-Laurent Lavoisier (1743-1794) had advanced the law of conservation of mass and before that there had been the law of conservation of momentum.
There were suspicions that energy ought to be conserved also. After all, motion was a common form of energy, and according to English scientist Isaac Newton, a moving body would move on forever if not affected by an outside force. The energy would not disappear.
In real life, though, a moving body does stop moving after a while because of air resistance or because of friction with the ground. What happens to its energy then? Perhaps it is converted into heat. If so, however, a given amount of mechanical energy should be converted into some fixed amount of heat. Otherwise energy is not conserved.
A British physicist, James Prescott Joule (1818-1889), undertook to check this by experimentation. He expended energy in a variety of ways and measured the amount of heat produced. All his experiments showed that a fixed quantity of work ended up in a fixed quantity of heat. In 1843 he published his results: that 41,800,000 ergs of work produce 1 calorie of heat. This is called the mechanical equivalent of heat. Since 10,000,000 ergs are now called a joule in Joule's honor, we can say that 4.18 joules equal 1 calorie.
This made it appear that there might well be a law of conservation of energy if heat were included among the forms of energy. In fact a German physicist, Julius Robert von Mayer (1814-1878), had presented a figure of the mechanical equivalent of heat in 1842 (one that was far less accurate than Joule's) and deduced from it that a law of conservation of energy existed, but his work did not attract attention.
)Drugs in Medicine
1935 A.D.
GREENCASTLE, INDIANA
Physostigmine had been found effective in the treatment of muscle disorders. But until the 1930s, the muscle relaxant had to be expensively extracted from soybeans. Then, in 1935 a southern Black man by the name of Percy Julian developed a breakthrough method for synthesizing physostigmine in the lab. The development was a culmination of Julian's research work at Howard University and DePauw University in Indiana. Today, physostigmine is used to treat glaucoma, a disease where fluid pressure impairs vision and can cause blindness.
Julian's work in chemical synthesis attracted the attention of Glidden Company in Chicago, a well-known manufacturer of paints, varnishes, foodstuffs, and various industrial chemicals. It was here that Julian developed a new chemical for use in fire-fighting foam, and a method for synthesizing the male and female sex hormones--testosterone and progesterone. Eventually, he was appointed as director of research at Glidden, a major turning point in the acceptance of African-American scientists.
√The Planet Jupiter
1610 A.D.
ITALY
Other than the Sun and the Moon, the planets known to the ancients were seen merely as points of light. When Galileo Galilei (1564-1642) turned his telescope on them, however, he found that they expanded into little orbs. Clearly, they were extended bodies but were too small, or too distant, or both, to show as orbs to the unaided eye. (The stars, however, remained points of light even when viewed by telescope.)
Jupiter was not only an orb but, in January 1610, Galileo observed four dimmer objects in its immediate vicinity. As he watched from night to night, he saw that they were circling Jupiter, as the Moon circles the Earth. They were, in short, four moons of Jupiter. German astronomer Johannes Kepler (1571-1630) later referred to them as satellites, a Latin word referring to those who remain close to someone rich or powerful in the hope of picking up scraps and favors.
Jupiter's four satellites were the first objects ever seen in the sky that clearly circled some object other than Earth, which was a strong point against Ptolemy's geocentrism. For that reason, the discovery displeased the rigidly religious. Some refused to look through the telescope in order to avoid seeing the satellites. One pointed out that since the satellites were not mentioned by Aristotle, they clearly did not exist.
Seeking support from Cosimo II (1590-1621) of the Medici family, who in 1609 had become grand duke of Tuscany (an Italian state with its capital at Florence), Galileo called the satellites "the Medicean stars." Fortunately, the name didn't stick. The German astronomer Simon Mayr, known by his Latin name of Simon Marius (1570-1624), saw the satellites soon after Galileo. He named them, in order of increasing distance from Jupiter, Io, Europa, Ganymede, and Callisto, after individuals closely associated with Jupiter (Zeus) in the Greek myths.
Galileo also noted that Jupiter and Saturn both had orbs that did not appear perfectly circular, as did the orbs of the Sun and Moon, but were somewhat elliptical.
9The Jupiter Probe
1973 A.D.
CAPE CANAVERAL, FLORIDA
On March 2, 1972, a Jupiter probe, Pioneer 10, had been launched -- the first probe intended to yield information concerning the outer Solar System. After passing safely through the asteroid belt, Pioneer 10 reached the vicinity of Jupiter on December 3, 1973, and passed only 85,000 miles above Jupiter's surface, going right through the planet's magnetosphere. Jupiter's magnetic field, 40 times as energetic as Earth's, made itself felt at a distance of 4,300,000 miles from the planet.
From the data obtained by the probe, it was possible to build a picture of the planet's structure. It would seem that Jupiter is a ball of hot liquid hydrogen mixed with some helium (a constitution much like that of the Sun).
The temperature rises rapidly with distance beneath the visible cloud surface. At 600 miles below, it is already 3,600° C; at 1,800 miles below, it is 10,000° C; at 15,000 miles below, it is 20,000° C; and at the very center of Jupiter, it is 54,000° C. Below 15,000 miles, hydrogen takes on a metallic form.
Pioneer 10 carried a message from Earth etched into a 6- by 9-inch gold-plated aluminum slab. It showed a man and woman next to an outline of Pioneer 10 drawn to scale. Also included were details of the Solar System and its location in the Universe relative to distant pulsars.
═Jupiter's Outer Satellites
1904 A.D.
WASHINGTON, D.C.
The large satellites had by now all been discovered, but there still remained small ones to find. In 1904 the American astronomer Charles Dillon Perrine (1867-1951) discovered a small satellite circling Jupiter.
It was the sixth to be discovered and was no more than 110 miles across. The next year he discovered a seventh, even smaller, satellite, only 50 miles across. Both circled Jupiter at average distances of 7,000,000 miles or so, far outside Jupiter's large satellites. They may be captured asteroids.
For a long time they were not given names but called Jupiter VI and Jupiter VII. The sixth is now known as Himalia and the seventh as Elara, after obscure nymphs in the Greek myths.
δJupiter's Radio Waves
1955 A.D.
PASADENA, CALIFORNIA
Radio waves are not only emitted by stars and galaxies. In 1955 the American astronomer Kenneth Linn Franklin (b. 1923) detected radio waves emanating from the planet Jupiter. They were nonthermal; that is, they were not of the pattern that would be emitted simply because of the temperature of Jupiter's cloud layer. Speculation arose that they were the result of charged particles in motion in the neighborhood of Jupiter, and eventually this was found to be true.
yMultiple Galaxies
1755 A.D.
KONIGSBERG, PRUSSIA (KALININGRAD)
Do the stars in the sky spread out evenly and indefinitely in all directions or are they contained in a finite volume with a particular shape? To the eye it might seem that the first alternative is correct -- except for the Milky Way. Once Galileo showed that the Milky Way consisted of very many, very dim stars, it became clear that there are far more stars in the direction of the Milky Way than in other directions. In 1750, an English astronomer, Thomas Wright (1711-1786), maintained that the stars formed a flattened finite system, but his writings were so mystical that it was hard to take him seriously.
In 1755, however, the German philosopher Immanuel Kant (1724-1804) made a similar suggestion. He said the Sun was one of a large number of stars that existed in a lens-shaped conglomerate, and that the Milky Way was the result of looking into the sky along the long axis of the lens. This conglomerate came to be called the Galaxy, from a Greek word for the Milky Way. Kant also suggested that certain nebulas, such as the one in Andromeda, were other galaxies or, as he called them in a dramatic phrase, "island universes."
In this, Kant was quite correct, but it was to be over half a century before the Galaxy's existence could be clearly demonstrated and over a century and a half before the existence of other galaxies could be demonstrated.
┴Kerosene
1853 A.D.
ENGLAND
In 1853 a British physician, Abraham Gesner (1797-1864), developed a process that would yield an flammable liquid from asphalt. Because it was driven out of a waxy mixture of solid hydrocarbons, Gesner called the liquid kerosene, from a Greek word for "wax."
Kerosene proved ideal for lamps, but even with Gesner's process, enough kerosene could not be produced to meet the great demands represented by the lamps of Europe and America.
Kidney Transplant
1954 A.D.
BOSTON, MASSACHUSETTS
When a vital human organ fails, death may be prevented if another organ can be transplanted. The transplanted organ may come from a living human being who can spare it, or from a human being dead in an accident so recent that the organ is still viable.
Unfortunately, human beings are allergic to one another, and the donated organ tends to be rejected, although scientists like Medawar were striving to find ways of reducing this tendency.
The first successful kidney transplant took place in December 1954 in Boston, from one identical twin to another. Since identical twins have the same genetic makeup, they have very little tendency to reject each other's organs. If one twin has two bad kidneys and the other two good ones, one of the good pair (which the donor can spare) can keep the dying twin alive. In this case, the twin that received the kidney lived on for eight years.
Many other kidney transplants have been carried through since, sometimes with considerable success, even among other than identical twins.
ΩTutankhamen's Tomb
1352 B.C.
EGYPT
The ancient Egyptian pharaohs had magnificent burials, and much in the way of gold and other precious materials was interred with them. Every effort was made to keep the tombs from being rifled and the contents stolen, even to the extent of placing the tomb at the center of a solid pyramid.
All efforts failed. All tombs were burglarized -- and a good thing, too. If all the gold had remained buried, it would have ruined the economy of the ancient world. The tomb-robbers did civilization a remarkable favor by restoring the tomb contents to circulation.
By 1000 B.C., the great days of the pharaohs were over, and every last tomb was empty -- except one. From 1361 to 1352 B.C., the pharaoh ruling over Egypt had been Tutankhamen. He was only about 21 when he died, but he was given the usual sumptuous burial. His grave was at once robbed, but for a wonder, the robbers were caught in the act and forced to return the loot.
Perhaps the fact that the grave had been looted had gotten out but the return had been kept quiet. At any rate, no further effort at looting was made for two centuries. Then, while a grave was being excavated for a later pharaoh, the resulting showers of stone chips covered the entrance to Tutankhamen's tomb, hiding it so effectively that it came down to the twentieth century intact.
A British archaeological expedition under George Edward Stanhope Molyneux Herbert, Earl of Carnarvon (1866-1923), and Howard Carter (1873-1939) found the first sign of the entrance to Tutankhamen's tomb on November 4, 1922. Three days later they reached the sealed burial chamber, and a rich treasure trove of ancient Egyptian artifacts was uncovered. It gave tremendous impetus to Egyptian studies.
It also gave rise to the silly tale of the "Pharaoh's curse," when Lord Carnarvon died five months later of an infected mosquito bite complicated by pneumonia, but surely no sane man could believe Tutankhamen had anything to do with it. Carter lived on for 17 years after opening the tomb.
╫Gaps in Saturn's Rings
1866 A.D.
PASADENA, CALIFORNIA
By now, nearly 90 asteroids had been discovered and their orbits calculated. It was clear that they were not evenly distributed, and the American astronomer Daniel Kirkwood (1814-1895) showed in 1866 that there were definite gaps, since called "Kirkwood gaps." He explained these gaps by postulating that any asteroids that would have been in those gaps would revolve around the Sun in a period that bore a simple ratio to the period of Jupiter. That meant that every two or three turns of the asteroid would bring it into the same position with respect to Jupiter.
Jupiter's gravitational pull would then be cumulative, and the asteroid would be forced either farther from the Sun or nearer to it, leaving a gap.
He pointed out that the gaps in Saturn's rings existed for similar reasons. If there were ring particles in Cassini's division, for instance, those particles would revolve about Saturn in just half the period of Saturn's satellite, Mimas.
╛Instant Cameras
1947 A.D.
CAMBRIDGE, MASSACHUSETTS
In 1947 American inventor Edwin Herbert Land produced the Land camera, which produced not negatives but positive prints, completely developed soon after the photograph was taken.
The camera had a double roll of film consisting of ordinary negative film and a positive paper with sealed containers of chemicals between. The chemicals were released at the proper moment and developed the positive print automatically.
┤Lanthanum
1839 A.D.
SWEDEN
The rare earths discovered by Gadolin were far more complex in chemical nature than he could have expected. The Swedish chemist Carl Gustaf Mosander (1797-1858) did more to reveal that complexity than anyone else.
He began, in 1839, by studying a compound of cerium, an element that had already been isolated from a rare earth mineral. In the process, he found a new element, which he named lanthanum, from a Greek word meaning "hidden," because it had been hidden so effectively in those minerals.
In the next few years, he isolated four other elements from the rare earth minerals: yttrium, erbium, terbium, and didymium.
The first three were named from syllables of Ytterby, the quarry in Sweden where the first rare earth mineral had been obtained. The last was named from the Greek word for "twin," because it seemed so similar in properties to lanthanum. In fact, all rare earth elements are remarkably similar to each other.
åLaser Disks
1972 A.D.
NETHERLANDS
Since the phonograph had been invented, sound had been reproduced through the vibration of a needle running along a groove. Eventually, of course, both needle and groove wore out, so that sound reproduction became imperfect.
In 1972 laser disks (also called compact disks) became practical. Here the sound was picked up by a laser beam, which translated it into information recorded on flat disks in the form of microscopically small pits. These could then be picked up by other laser beams. There was no question of wear, more sound could be packed onto a given surface, and reproduction was nearer perfection than ever before.
The Laser
1960 A.D.
LOS ANGELES, CALIFORNIA
The principle of the maser, which produced an intense, coherent, monochromatic beam of microwaves, could be applied to any wavelength, including those of visible light. This had been pointed out by American physicist Charles Hard Townes in 1953.
The first maserlike device capable of producing an intense, coherent, monochromatic beam of visible light was constructed in May 1960 by the American physicist Theodore Harold Maiman (b. 1927), making use of the three-level principle worked out in 1956 by Dutch-born American physicist Nicolaas Bloembergen (b. 1920).
Maiman designed a ruby cylinder with its ends carefully polished flat and parallel and covered with a thin silver film. Energy was fed into it from a flash lamp until it emitted a beam of red light.
The coherent light so produced had only a slight tendency to spread and could be concentrated into so tiny a point that, at that point, temperatures could be reached far higher than the surface of the Sun. The device was first called an optical maser, but since it could be described as light amplification by stimulated emission of radiation, the initials of that phrase were used and it came to be called a laser.
Lasers soon proliferated into many different types, with many different uses.
≡Latent Heat
1762 A.D.
SCOTLAND
Black found in 1762 that if a mixture of ice and water was heated, the heat was absorbed but the temperature did not change.
All the heat went toward melting the ice into water, the water being at the same temperature as ice but containing more heat. The same happened to an even greater extent when water was boiled into vapor.
Black called this latent heat (from a Latin word for "hidden"), since the heat was there but did not make itself apparent in the form of temperature. The latent heat was not lost, of course, for when water vapor was condensed to water, or water was frozen to ice, the latent heat was given off again.
An understanding of latent heat was important in the improvement of the steam engine a few years later.
çRadioactivity and Earth
1906 A.D.
DISTRICT OF COLUMBIA, UNITED STATES
In 1906 the American geologist Clarence Edward Dutton (1841-1912) suggested that pockets of radioactivity in the Earth's crust delivered enough heat over time to activate volcanic action.
This was the beginning of the understanding that radioactivity added substantial heat to the Earth's crust, enough to balance that lost by radiation, so that any attempt to judge the Earth's age by calculating the time it took Earth to "cool down" from an initial high temperature was far off base. Earth could be billions of years old and still retain a heated interior.
Dutton also developed methods for determining the depth of earthquake origins and the velocity with which earthquake waves traveled through the Earth. This opened the way for a technique that finally offered strong evidence concerning the physical and chemical nature of the Earth's deep interior. @
3Quantitative Chemistry
1769 A.D.
FRANCE
Although Scottish chemist Joseph Black (1728-1799) had demonstrated the usefulness of quantitative measurements in chemistry, what made them an integral part of the science was the work of French chemist Antoine-Laurent Lavoisier (1743-1794), who is universally considered the father of modern chemistry.
There were at this time some who still clung to the Greek theory of elements and their changeability. They argued that if water were boiled for a long time, a sediment appeared, and that this was clearly a conversion of water into a kind of earth, in line with Greek thinking.
Lavoisier decided, in 1769, to test this matter. He boiled water for 101 days in a device that condensed the water vapor and returned it to the flask, so that no water was lost in the process. He weighed both water and vessel before and after the boiling.
Sediment did appear, but the water did not change its weight during the boiling, so the sediment wasn't formed out of the water. The flask itself, however, had lost an amount of weight just equal to the weight of the sediment.
In other words, the sediment was material from the glass, slowly etched away by the hot water and precipitating in solid fragments. Here was a clear-cut example of the way in which observation, without measurement, could be useless and misleading.
e The Law
1775 B.C.
BABYLON (Iraq)
Human beings must always have had customs that they followed assiduously, even when enforcement was not an issue. In a simple society, custom is, in fact, enough. Everyone knows what behavior is expected, and conforms almost automatically. If not, there is social ostracism, and this is sufficiently undesirable to enforce the rule of custom.
As a society grows more complex, however, there are more varieties of behavior that must be controlled and regulated, more perplexing conditions, more complicated questions, more puzzling interactions. It becomes difficult to remember all the rules, and the suspicion is sure to arise that powerful people make up or alter rules to suit themselves. The demand, then, is for the rules of society to be put in writing, so that all can see for themselves what they are, and so that they cannot be unfairly or arbitrarily twisted or modified.
We don't know when the first laws were written down, but the first relatively complete law code that we still have was established by Hammurabi, king of Babylon (reigned 1792-1750 B.C.), who founded a rather short-lived Babylonian Empire in the Tigris-Euphrates valley, one that succeeded the Akkadian Empire. (After this time, the people of the valley were referred to as Babylonians for nearly two millennia.)
Perhaps about 1775 B.C., Hammurabi had his law code inscribed on an 8-foot-high stone pillar of hard diorite. It was clearly intended to be permanent, and it was, for we still have it.
The stele is topped by a relief that shows Hammurabi standing before the Sun- god, Shamash. (It was usual in ancient times to suppose that a law code was received by a king from a god. That tended to lend the law authority. Thus, Moses received the Jewish law code from God on Mount Sinai, according to the Bible.)
Down along the face of the stele are 21 columns of finely written cuneiform, outlining nearly 300 laws that were to govern people's actions and guide the king and his officials in dispensing justice.
The stele originally stood in the town of Sippar, some 30 miles upstream from Babylon, but an invading Elamite force plundered the city and carried away the stele as spoil. It remained in Elam's capital, Susa, thereafter and was still there, in Susa's ruins, in 1901, when a French archaeologist, Jacques Jean Marie de Morgan (1857-1924), found it and brought it back to Europe.
dLawrencium
1961 A.D.
U.S.A.
The attempt to produce more and more complex atoms did not cease. In 1961 a few atoms of element 103 were produced, and it was named lawrencium after Lawrence, the inventor of the cyclotron, who had died three years earlier.
With lawrencium, the last of the actinides was discovered.
There were now 15 actinides as there were 15 lanthanides.
└ Laws of Motion
1687 A.D.
CAMBRIDGE, ENGLAND
In the nearly 80 years since German astronomer Johannes Kepler (1571-1630) had come up with the elliptical orbits of the planets, scientists had been trying to work out what it was that kept the planets in their orbits and made the orbits ellipses. It was clear that the Sun had to attract the planets somehow, but what was the attraction and how did it work?
A number of scientists got pretty close to what turned out to be the truth, notably English physicist Robert Hooke (1635-1701), who was a great enemy of English scientist Isaac Newton (1642-1727). When Hooke boasted to English astronomer Edmond Halley, who was a great friend of Newton, that he (Hooke) had the answer. Halley went to Newton to check the matter with him. Newton said that he had worked out the answer in 1666 but had never published it. Halley, in great excitement, urged publication.
Newton could do this now with much greater confidence than he could have done it 20 years earlier. For one thing, he now had calculus, which made some calculations easy that would have been difficult before. For another, he had French astronomer Jean Picard's (1620-1682) figures on the Earth's size, and accuracy in that respect was necessary to his calculations.
Newton took 18 months to write the book and, in 1687, published Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), often known simply as the Principia. It was written in Latin and did not appear in English until 1729. It is generally considered the greatest science book ever written.
Despite the greatness of the book, Newton had trouble publishing it. Hooke was unalterably opposed, and the Royal Society hesitated to become involved in the controversy. Fortunately, Halley had inherited a fortune in 1684, when his father was murdered by unknown assailants. He saw to the proofreading of the book and had it published at his own expense.
In the book, Newton codified Galileo's findings concerning falling bodies into the three laws of motion.
The first enunciated the principle of inertia: A body at rest remains at rest and a body in motion remains in motion at a constant velocity (that is, constant speed in a constant direction) as long as outside forces are not involved.
The second law of motion defines force as the product of mass and acceleration. This was the first clear distinction between the mass of a body (representing its resistance to acceleration) and its weight (representing the extent to which it is acted on by a gravitational force). The third law of motion states that for every action there is an equal and opposite reaction.
These laws of motion are equivalent to the axioms and postulates with which Euclid began his treatment of geometry. From the axioms and postulates, an incredible number of theorems can be derived, each one building on theorems that went before. In the same way, from the laws of motion, an enormous number of mechanical effects can be deduced.
▒The Leap Year
46 B.C.
ITALY
The Romans, whatever their success in war, politics, and law, were poor in science. There was not one really important Roman scientist. The Romans left science to the Greeks, and as Roman fortunes grew and Greek fortunes declined, science too declined into what was eventually a dark age.
It is not surprising then that the Romans used a calendar far worse than those used by any of the nations to its east. And since that calendar was occasionally manipulated by political priests for partisan advantage, it grew worse with time rather than better.
The Roman statesman Gaius Julius Caesar (100-44 B.C.) admired the Egyptian solar calendar, however, and brought in a Greek astronomer, Sosigenes (1st century B.C.), to work out a version of that calendar for use at Rome. Thus originated the Julian calendar (named in Caesar's honor) of 365 days, with some months of 30 days and some of 31, plus an added day every four years (Leap Year). The additional day was added because the year is actually 365-1/4 days long, and in this respect the Julian calendar was an improvement over the Egyptian. (The Julian calendar, with a small correction made 16 centuries later, is still in use today.)
lLe Chantelier's Principle
1888 A.D.
FRANCE
The French chemist Henri-Louis Le Châtelier (1850-1936) stated a rule in 1888 that became known as Le Châtelier's principle. The rule is this: Every change in one of the factors of an equilibrium brings about a rearrangement of the system in such a direction as to minimize the original change.
If a system in equilibrium is placed under increased pressure, for instance, the system rearranges itself to take up less room, so as to minimize the increased pressure. Again, if the temperature is raised, the system undergoes a change that absorbs some of the additional heat, so as to minimize the rise in temperature.
This very general statement included the law of mass action of Guldberg and Waage and fit in well with Gibbs's chemical thermodynamics.
It also worked as a guidepost to direct scientists in how best to bring about desired changes in a system.
▀Light-Emitting Diodes
1962 A.D.
WORLD
Light-emitting diodes are semiconductor devices that emit visible light as their electrons drop from a higher energy level to a lower one. The first practical device of this sort was produced in 1962.
Such diodes are now routinely used where light needs merely to be seen and not to illuminate. Thus, light-emitting diodes are used in digital clocks, in pocket computers, in elevator floor indicators, in taxi meters, and as signals in electronic equipment generally.
The Lever
260 B.C.
SYRACUSE, ITALY
Levers were used in prehistoric times. It is no great trick for a lively mind to try to pry up a rock with a long stick and to find that it works better if another, smaller rock is placed under the stick to give the stick something to push against. It would then quickly be discovered that the closer the small rock is to the big rock being pried up, the easier the prying gets.
Nevertheless, the precise mathematics of lever action was not worked out until the Greek scientist Archimedes (ca. 287-212 B.C.) did it about 260 B.C.
You might say, "What difference does it make that scholars worked out fancy theories and mathematics for levers, when practical people had been actually using such devices for thousands of years?"
The point is that use without theory is largely hit and miss. Advances are made, yes, but slowly. Once a useful theory is worked out, however, it is like removing a blindfold. It becomes obvious how a device might be improved, or what new observations need to be made. With a theory, advances speed up enormously. Therefore we give Archimedes credit for the principle of the lever, regardless of how long the lever had been in use before his time.
Archimedes also worked out the principle of buoyancy, the manner in which any object immersed in a fluid displaces a volume of fluid equal to its own volume. This provided a way of measuring volume, a way of explaining why some things float and some don't, and so on. Archimedes grasped the principle quite suddenly when he lowered himself into a public bath and noticed the water overflow.
The story is that he sprang out of the bath and raced home nude, shouting "Eureka! Eureka!" ("I have it! I have it!"). He had been given the problem of checking whether a golden crown was adulterated with a less dense metal or not, without damaging the crown. For that he had to know the volume, and the buoyancy effect would give it to him. (The ancient Greeks, by the way, did not mind nudity, so Archimedes' action was not as bizarre as might be thought.)
4Missouri River
1804 A.D.
MISSOURI RIVER, USA
President Jefferson wanted the new territory of Louisiana to be explored. For the purpose, he chose Meriwether Lewis (1774-1809), who in turn chose William Clark (1770-1838). These two, with a party of about 40 young men, made up the Lewis and Clark Expedition.
They went to St. Louis where they remained over the winter of 1803-1804. Then on May 14, 1804, they moved up the Missouri River and followed it back to its source. This brought them to the American border, but they went on anyway into the Oregon Territory, the only part of the American continents that had still not been effectively claimed by any one power. They followed the Columbia River to the Pacific Ocean, which they reached on November 15, 1805, and then returned to St. Louis, which they reached on September 23, 1806. This was the first trip across the United States from ocean to ocean and back. The Lewis and Clark Expedition brought back information on the Indian tribes of the region, on animal life (including huge herds of bison), on plant life, and on natural features.
JLight and Magnetism
1896 A.D.
SCOTLAND
Maxwell had maintained that an oscillating electric charge could produce radiation, and Hertz had shown that to be correct with his discovery of radio waves. Maxwell had also maintained that light was an electromagnetic radiation, but if so, what was the electric charge that was oscillating and therefore producing it?
Arrhenius had maintained that atoms or groups of atoms could carry electric charges, and Lorentz had wondered if it might be electric charges within the atom that did the oscillating. If that were the case, then placing a light source under the influence of a strong magnetic field ought to affect the oscillating charges and introduce changes in the spectral lines.
Lorentz had a student, the Dutch physicist Pieter Zeeman (1865-1943), who undertook the experiment, and indeed, the magnetic field split the spectral lines into three components. This Zeeman effect could be used to study the fine details of atomic structure and to yield information on the structure of stars as well.
As a result, Lorentz and Zeeman shared the Nobel Prize in physics in 1902.
═The Diffraction of Light
1665 A.D.
ITALY
It was about this time that the question of waves versus particles began to be raised, one that was to be argued for a long time.
Water waves could be seen, and the fact that they tended to curve around obstacles could be considered a characteristic of all waves. Particles, on the other hand, if moving in a straight line, did not curve around obstacles but either struck and bounced back (being reflected) or missed and continued moving in a straight line.
Since sound curved around obstacles, it was taken to be a wave phenomenon. Since light cast sharp shadows, it was natural to think of it as composed of tiny particles.
An Italian physicist, Francesco Maria Grimaldi (1618-1663), made an observation that was published posthumously in 1665. He had let a beam of light pass through two narrow apertures, one behind the other, and then fall on a blank surface. He found that the band of light on that surface was a trifle wider than the apertures. He believed, therefore, that the beam had been bent slightly outward at the edges of the aperture, a phenomenon he called diffraction.
This would make it seem that light was a wave phenomenon. But a wave's bending about an obstacle depends on the relative size of the wave and the obstacle. Any wave will be reflected by a barrier considerably larger than itself: water waves will be reflected by a breakwater and sound waves will be reflected by a cliff wall. Since light waves were reflected from small objects, and diffraction was only very slight, it must follow that if light were composed of waves, they were very small waves indeed.
However, Grimaldi's work was largely neglected and the controversy went on for a century and a half without reference to him.
ªLighthouses
280 B.C.
ALEXANDRIA, EGYPT
The Hellenistic realms did not hesitate to show their advanced technologies in the form of large architectural undertakings. The island of Rhodes, for instance, celebrated its successful resistance to a siege by a Macedonian general in 305-304 B.C. by having a large statue of the Sun-god constructed overlooking its harbor. That statue was 105 feet high and was completed in 280 B.C. It was called the Colossus of Rhodes. It stood for 60 years before being destroyed by an earthquake, and after its destruction its size was greatly exaggerated.
In Alexandria a much more useful and even larger structure was built, the first major lighthouse. It was called the Pharos from the name of the spit of land on which it was built. It was at least 280 feet high, rested on a bulky square base, and had stairs up which loads of resinous wood had to be carried. (No elevators, of course.) The light of the burning wood could be seen 35 miles out to sea. It, too, was completed in 280 B.C. and it stood for 16 centuries before being destroyed by an earthquake.
Both the Colossus of Rhodes and the Pharos were listed by the ancients as among the Seven Wonders of the World.
jLeyden's Electric Jar
1745 A.D.
LEYDEN, NETHERLANDS
The glass sphere English physicist Francis Hauksbee (ca. 1666-1713) produced in 1706 was surpassed as an electricity-storing device by the work of a Dutch physicist, Pieter van Musschenbroek (1692-1761).
In 1745 he placed water in a metal container suspended by insulating silk cords, and led a brass wire through a cork into the water. He built up an electric charge in the water but did not realize how much had accumulated in the device until an assistant happened to pick it up and touch the brass wire outside the cork. The container promptly discharged all of the electric charge it had accumulated and gave the poor assistant a fearful shock. It was the first good-sized artificial electric shock anyone had ever received. (The lightning stroke is worse, of course, but it is a natural electric shock.)
A German physicist, Ewald Georg von Kleist (1700-1748), independently produced the same device at about the same time. He discovered the strength of the charge by accidentally discharging it into his own body. He said he wouldn't take another such shock to be the king of France and worked with the device no longer.
Because Musschenbroek popularized the device and because he worked at the University of Leyden in the Netherlands, the electricity-storing device came to be called a Leyden jar. It was at once made use of by other experimenters.
äLightning Fire
500,000 B.C.
BEIJING, CHINA
The first traces of Homo erectus (erect man) in Asia were found by Canadian anthropologist Davidson Black in a filled-up cave near Beijing.
The cave near Beijing had traces of campfires. This meant that fire had been "discovered" some 500,000 years ago. Here is a characteristic that marks off human beings from all other organisms. Every human society in existence, however primitive, has understood and made use of fire. No living creature other than human beings uses fire in even the most primitive fashion.
I have put discovered in quotation marks, for fire was not discovered in the usual sense. Lightning could start a fire ever since Earth's atmosphere gained enough oxygen to sustain one and Earth's land surface possessed a forest cover that could burn, and that means for some 400 million years. From that fire, then as now, any animal capable of fleeing would flee.
1Gliders
1891 A.D.
GERMANY
Four decades had passed since English engineer George Cayley (1773-1857) had built the first glider capable of carrying a human being. Now a German aeronautical engineer, Otto Lilienthal (1848-1896), made them into things of grace and ability. As early as 1877 he had shown that curved wings were superior to flat wings as far as gliding was concerned. In 1891 he launched himself on his first glide. He died a few years later in a crash landing, but he made gliding popular, and it turned out to be not too long a step from a glider to an airplane.
jLindbergh's Flight
1927 A.D.
PARIS, FRANCE
On May 20-21, 1927, the American aeronaut Charles Augustus Lindbergh (1902-1974) flew from New York to Paris. Others had flown across the Atlantic Ocean before, but Lindbergh did it nonstop and alone in a small single- engine plane, Spirit of St. Louis, in a flight that kept him awake for 33-1/2 hours. With this feat, aeronautics came of age.
⌠Linen
6000 B.C.
IRELAND
Flax produces a fiber that can be interwoven much as twigs or bark might be interwoven to form a basket. To make a strong thread, a number of flax fibers would be twisted together. We call the result linen. (Like the word linen, the word line comes from the word for "flax.")
The first use of linen, perhaps as early as 6000 B.C., was to produce linen cords that could be used in fishing. Interweaving these cords produced nets.
Eventually very fine nets were made -- in other words, cloth, or textiles (from a Latin word for "weaving"). The formation of cloth from linen and eventually from other plant and animal fibers, such as cotton and wool, revolutionized clothing. Until then, furred hides had been worn. These were all right in cold temperatures but too hot at other times. They weren't porous, they were heavy, and they smelled.
Textiles, on the other hand, were light, flexible, porous, and could be easily cleaned. They have remained the preferred material for clothing ever since.
Spectral Line Shift
1848 A.D.
FRANCE
Six years earlier, Doppler had explained the Doppler effect with respect to sound. Now the French physicist Armand-Hippolyte-Louis Fizeau (1819-1896) argued that the same effect would apply to any wave motion, particularly that of light.
If the light of the spectrum were unbroken, this would not be noticeable, since if the source were receding from us, ordinary visible light would move past the red boundary and become invisible, while invisible ultraviolet light would move past the violet boundary and become visible. It would work in the opposite direction if a light source were approaching us, and in neither case would there be any apparent change.
There are dark lines in the spectra, however, and these would shift their position. That would be noticeable. The lines would shift toward the red if the light source were receding and toward the violet if the light source were approaching. This is sometimes called the Doppler-Fizeau effect.
It was the red shift that proved of particular importance to astronomy.
╣Antiseptic Surgery
1865 A.D.
GREAT BRITAIN
Anesthetics had come into use nearly 20 years before, but if the process had become more nearly painless, it still remained deadly. The operation might be successful, yet the patient might develop inflammation and die. In 1865 the British surgeon Joseph Lister (1827-1912) learned of French chemist Louis Pasteur's (1822-1895) germ theory of disease and it occurred to him that death after operations might result from a germ infection to which the traumatized tissues were particularly susceptible. The germs producing the infection might come from the doctors themselves, or from their instruments.
Lister therefore instituted the practice of using phenol solutions to clean hands and instruments, and the death rate after operations dropped at once. Hungarian physician Ignaz Phillipp Semmelweiss (1818-1865) had attempted the same thing 17 years earlier, but without the justification of Pasteur's theory, and physicians refused to listen.
This shows the importance of theory in the most practical of affairs.
Eventually, chemicals less irritating and more effective than phenol were used, and antiseptic (from Greek words meaning "against putrefaction") surgery became the rule.
óLight as Waves or Particles
1678 A.D.
ENGLAND
The particle-versus-waves controversy grew sharper.
English scientist Isaac Newton (1642-1727) felt that light consisted of particles, partly because there was a vacuum between Earth and Sun and he didn't see how a wave could cross a gap where there was nothing to wave.
Dutch astronomer Christiaan Huygens (1629-1695), on the other hand, insisted that light consisted of waves of the same type as sound (so-called longitudinal waves, which wave in and out in the same direction the waves are traveling). As to what was waving, Huygens supposed that there was a very subtle fluid in the vacuum of space (this came to be referred to by Aristotle's term aether), which could not be detected in any ordinary way.
Neither Newton's particles nor Huygen's longitudinal waves could explain Bartholin's observation of double refraction nine years before, but that was ignored. The controversy continued to rage.
6Human Beings on the Moon
1969 A.D.
HOUSTON, TEXAS
At 4:18 P.M. eastern daylight savings time on July 20, 1969, Neil Alden Armstrong (b. 1930) and Edwin Eugene Aldrin, Jr. (b. 1930) brought the lunar module of Apollo 11 to the surface of the Moon, while Michael Collins (b. 1930) remained in orbit about the Moon. Neil Armstrong stepped out, the first human being to set foot on any world other than the Earth, saying "That's one small step for a man, one giant leap for mankind." John Kennedy's goal of reaching the Moon by the end of the decade had been reached.
The two men remained on the Moon for 21 hours 37 minutes and returned to Earth safely at 12:51 P.M. eastern daylight savings time on July 24, eight days after takeoff. A second American ship landed on the Moon in November 1969, and astronauts remained on the Moon's surface for 15 hours.
¬Aristotle's Logic
350 B.C.
GREECE
Everyone reasons after a fashion. It is impossible not to. Primordial hunters would reason from footprints that an animal had passed that way and would identify it from the nature of the markings. Everything you do, if you are in a normal state of mind, has some reason behind it. Unfortunately, however, there are innumerable ways of reasoning in a faulty manner, and reasoning in general can be swayed by emotions, by self-interest, and so on. The result is that people frequently, and under some circumstances almost always, behave in an irrational manner.
Aristotle was the first thinker we know of who undertook to work out a legitimate system of reasoning (logic, from the Greek for "word"). His book Organon developed the study of logic in great and satisfying detail, describing the art of reasoning from premise to necessary conclusion and thereby demonstrating how to establish the validity of a line of thought.
║The Longbow
1298 A.D.
ENGLAND
The longbow was invented in the 13th century by the Welsh. It was more than 6 feet long and fired arrows that were 3 feet long. A skilled longbow archer could shoot an arrow accurately for 250 yards and reach an extreme range of 350 yards. This was twice the range of the average crossbow, and much more important, while the crossbow was being cranked up once, the longbow could be fired five or six times. If equal numbers of archers with longbows and crossbows were to encounter each other, the crossbow archers would be riddled.
The disadvantage of the longbow, however, was that the archer had to exert a force of 90 to 100 pounds to draw the bow and to maintain that pull evenly until the feather of the arrow was aligned with the archer's ear. That required strength and a great deal of training.
Edward I of England recognized the value of the weapon and set about training a corps of English longbow archers. He put the longbow to the test against the Scots at the Battle of Falkirk on July 22, 1298.
The Scottish infantry had pikes, but the English archers with their longbows shot them down from a distance, and when enough had been destroyed to reduce the rest to a disorderly mob, the English cavalry came in to finish the job.
The English went on to use the longbows in other battles, and no other nation ever adopted this obvious weapon. As a result, the English were a great military power for the next century and a half.
ILarge Refracting Telescope
1897 A.D.
ITALY
The first telescope that Galileo used was a refracting telescope, making use of lenses only. In the nearly three centuries since, such telescopes had grown larger and more elaborate.
In 1897 Clark, the discoverer of Sirius's dim companion, supervised the construction of a refracting telescope with a lens 40 inches across. It was the largest and best refractor built up to that time, but it had reached the limits of the art. No larger refractor has been built since then, or is likely to be built. All larger telescopes are of the reflecting variety that Newton invented.
▐Light Waves
1678 A.D.
ENGLAND
The controversy over the nature of light -- whether it consisted of a stream of particles or of tiny waves -- had been going on for a century.
In 1801 an English physicist, Thomas Young (1773-1829), began a series of experiments that seemed to settle the matter. He showed, for one thing, that the kind of diffraction noted by Grimaldi did exist.
Then too, he allowed two separate beams of light emerging from two narrow slits to overlap and found interference, for the overlapping beams showed alternate strips of light and dark.
If light consisted of waves, then the waves of the two bands of light might move up and down in unison and reinforce each other in some places. In other places, one might move up while the other moved down, and they would cancel each other. Such interference is well known in the case of sound waves and water waves. Streams of particles, on the other hand, could scarcely produce interference effects.
It took a while for Young's demonstration to be understood and accepted, but once it was, it was seen that light was a wave phenomenon. The different colors of the spectrum marked out light with different lengths of waves (or different wavelengths). Short wavelengths are refracted (bent in their path) more than long wavelengths, so red light (the least refracted) has the longest waves, while orange, yellow, green, blue, and violet have successively shorter waves.
From Young's work, it began to seem probable that infrared radiation had waves longer than those of red light, while ultraviolet radiation had waves shorter than those of violet light.
Because light cast sharp shadows and the diffraction effects were so small, light waves had to be very tiny. Young calculated from his interference experiments that they must be less than a millionth of a meter long.
Two kinds of wave action are known, however. There are longitudinal waves, in which the vibration is back and forth in the direction in which the waves are moving. Sound waves are of this type. In transverse waves, the vibration is up and down in the direction at right angles to that in which the waves are moving. Water waves are of this type.
Young rather suspected that light consisted of longitudinal waves, but in this he was wrong.
▌Lutetium
1907 A.D.
FRANCE
The rate of discovery of elements had been falling off -- at least of elements that were not involved in radioactive series. Up to this point, 13 elements had been isolated from the rare earth minerals, which might have exhausted the supply, but there turned out to be room for another. In 1907 the French chemist Georges Urbain (1872-1938) discovered a 14th and named it lutetium, from an old name for the Roman town that had stood on the site of what is now Paris.
ALSD
1943 A.D.
SWITZERLAND
In 1913 a Swiss chemist, Albert Hoffman (b. 1906), was working with lysergic acid, which is obtained from ergot, a mold that produces serious and sometimes deadly disorders in the human body. Hoffman modified it to form the diethyl amide of the compound and apparently absorbed some of the substance. He was overcome by strange sensations, vivid fantasies, and brilliant colors. He deliberately swallowed a tiny bit more of the material -- and the results were even more weird.
He had clearly suffered from hallucinations, so that lysergic acid diethylamide (usually abbreviated LSD) came to be called a hallucinogen, or a psychedelic drug. Other hallucinogens occur in nature, in certain mushrooms, in peyote cactus, and elsewhere. Even alcohol in sufficient quantities becomes hallucinogenic. Hallucinogens have been widely used in religious ceremonies, presumably because they seem to offer a vision of another world.
LSD was a particularly effective hallucinogen, and in time its use became a fad among young people, which helped fasten the drug culture on America.
vMach Numbers
1887 A.D.
AUSTRIA
With advancing technology, human beings were traveling faster than they had in the past, and they were likely to travel faster still in the future. The faster human beings traveled, the more important air resistance would be. The Austrian physicist Ernst Mach (1838-1916) studied the conditions that occurred when a solid object and air were in rapid motion relative to each other.
The natural rate at which air molecules can move is the speed of sound through air. When an object moves through air at higher speeds, the air molecules can no longer move aside naturally but must be shoved aside (so to speak) faster than they want to go. This produces new conditions, which Mach studied.
For instance, faster-than-sound motion compresses air and sets up a bunching of sound waves that then expands to produce a sudden clap. Thunder is the best example of such a sonic boom, with the heat of lightning expanding the air at greater than the speed of sound. Another example of a sonic boom is the crack of a bullwhip.
A speed equal to that of sound is now called Mach 1 in Mach's honor.
Twice that speed is Mach 2, and so on.
gCircumnavigating the Earth
1523 A.D.
STRAIT OF MAGELLAN
Ferdinand Magellan (ca. 1480-1521) is the English name of a Portuguese navigator, financed by Spain, who sailed west with five ships on September 20, 1519, in search of the Far East. When he reached the eastern bulge of South America, he began looking for a southern end to that continent, which he found on October 21. For over five weeks, he felt his way through what is now known as the Strait of Magellan, amid storms, and on November 28, it opened into an ocean and the storms ceased. As Magellan sailed on and on through good weather, he called this new ocean the Pacific.
However, the Pacific Ocean was far larger than anyone would have expected, and was sadly free of land. For 99 days, the ships sailed through unbroken sea, and the men underwent tortures of hunger and thirst. Finally they reached the island of Guam, then they sailed westward to the Philippine Islands.
There, on April 17, 1521, Magellan died in a skirmish with the inhabitants. The expedition continued westward, however, and a single ship with 18 men aboard, under the leadership of Juan Sebastián de Elcano (ca. 1476-1526), finally arrived back in Spain on September 7, 1522. This first circumnavigation of the globe had taken three years, and if the loss of life can be set aside, the single returning ship carried enough spices to make the voyage a complete financial success.
The voyage showed beyond doubt, at last, that the Earth was 25,000 miles in circumference, as Eratosthenes had calculated in about 240 B.C. It showed also that the Earth possessed a worldwide ocean in which the continents existed like huge islands.
╙The Shifting Magnetic Poles
1635 A.D.
ENGLAND
Gilbert's demonstration that the Earth was a magnet could be used to explain the fact that the compass needle did not necessarily point to the truth north. If the Earth's magnetic north pole were not located at the geographic north pole, and if the compass needle pointed to the magnetic north pole, then naturally it would not necessarily point true north. What's more, if the magnetic pole were on the Atlantic side of the geographic north pole, then as one crossed the Atlantic from east to west, the compass needle would begin by pointing west of north and end by pointing east of north, as Columbus found it did.
At any one place, however, Gilbert maintained, the compass needle would always point in the same direction.
The English astronomer Henry Gellibrand (1597-1636) showed, however, that this was not so. He kept track of the pointing of the compass needle in London, both by his own observations and by the recorded observations of others, and in 1635 published his findings: the compass needle had shifted direction some 7 degrees in the past half-century. This was an indication not only that the magnetic poles might exist away from the geographic poles but that they might be shifting position as well.
Magnesium and Chlorophyll
1906 A.D.
GERMANY
Ever since Pelletier discovered chlorophyll, it had been understood that the substance was of the utmost importance. After all, it brought about the production of food and oxygen on which animal life, including human beings, subsisted. The chemical structure of chlorophyll was therefore of devouring interest to biochemists, but it was still poorly understood for all that.
The German chemist Richard Willstätter (1872-1942), however, managed to supply a key item of information about chlorophyll structure in 1906. He showed that each chlorophyll molecule contained a magnesium atom, held in much the same way that an iron atom was held by hemoglobin.
For this and for other work on planet pigments, Willstätter was awarded the Nobel Prize for chemistry in 1915.
╡Magnetic Ore
500 B.C.
MAGNESIA (MANISA), ASIA MINOR
In the sixth century B.C. it was discovered (by a shepherd, according to legend) that a certain kind of ore attracted iron. Since the ore was found near the Asia Minor city of Magnesia, it came to be called the Magnesian stone, or in English, a magnet, and the phenomenon was magnetism. The phenomenon was first studied by Thales. It was eventually found that stroking with the magnetic ore could turn a sliver of iron or steel into a magnet.
Somehow it was discovered that if a magnetic sliver was allowed to turn freely, it would come to rest pointing in a north-south direction. We don't know how this fact was discovered, but the Chinese were the first to be aware of it.
It is referred to in Chinese books dating as far back as the second century.
The Chinese never used the magnet for direction-finding in navigation, because by and large they were not great navigators. The Arabs may have learned of it from them, however, and perhaps some Crusaders learned of it from the Arabs. In 1180 the English scholar Alexander Neckam (1157-1217) was the first European to make reference to this directional ability of magnetism. As soon as the Europeans heard of it, they began to try to put it to use as a navigation aid, and they began to improve it. Eventually a magnetic needle was put on a card marked with various directions, and because the needle was free to move all around the card, it was referred to as a magnetic compass (from a French word meaning "to go around"). If a single point in time can be picked as the moment when Europe first took the road that was to lead to world dominion, it was the moment when Europeans heard of the magnetic compass and put it to use. With the compass, Europeans could eventually go wherever they wished over the wide oceans, so that they eventually dominated the whole world as no other relatively small group of people had ever done before or (in all likelihood) will ever do again.
äThe Sun's Energy Source
1938 A.D.
U.S.A.
Gamow had suggested that hydrogen fusion was the source of the Sun's energy but could not supply the details.
By 1938, however, much had been learned about nuclear reactions -- the energy they delivered and the speed with which they took place -- from experiments in the laboratory. This, together with reasonable estimates of the pressures and temperatures deep in the Sun's core, enabled the German-born American physicist Hans Albrecht Bethe (b. 1906) to outline in detail the mechanism by which hydrogen fusion could take place in the Sun's core. (The German astronomer Carl Friedrich Weizsacker [b. 1912] independently advanced similar ideas at about the same time.) For the first time, a suitable answer was given to Helmholtz's question about the source of the Sun's energy.
For this, and for other work in nuclear physics, Bethe was awarded the Nobel Prize for physics in 1967.
mHunting Magnetic Monopoles
1982 A.D.
SCOTLAND
Maxwell's equations are not quite symmetrical with respect to electricity and magnetism. The asymmetry lies in this: Electricity exists as positive and negative charges, and these can be easily isolated -- there are particles with positive charge only (positrons or protons) and particles with negative charge only (electrons or antiprotons). Magnetism, however, exists as north and south poles that do not seem to exist separately. Objects possessing magnetism always have both a north and a south pole. If an object could be found that was only a north pole or only a south pole (magnetic monopoles), then Maxwell's equations could be made completely symmetrical.
By the Grand Unified Theory, (see Proton Decay), it would seem that magnetic monopoles must exist but must be so monstrously massive that there could only have been enough energy to form them in the immediate instants following the big bang. Still, if they were formed then, they should still exist today, and scientists should be able to detect them.
Therefore, the physicist Blas Cabrera devised a setup that would produce an electric current if a magnetic monopole were to pass through it, and on February 14, 1982, it produced such a current.
That single detection has not yet been repeated, however, either by Cabrera or by anyone else, so the existence of the magnetic monopole remains in question.
KMagnetic Reversals
1963 A.D.
FRANCE
As early as 1906, the French physicist Bernard Brunhes had noted that in some rocks, crystals magnetized in directions opposite to that of Earth's magnetic field. This was ignored at first, but slowly it came to be realized that the Earth's magnetic field strengthened and weakened. The weakening might go all the way to zero and then begin to strengthen in the opposite direction.
It might be, then, that magnetic reversals occurred at intervals in Earth's history.
If the Atlantic Ocean's floor had spread with the upwelling of magma in the Global Rift, then the sediments laid down on the sea bottom ought to exist in strips. If magnetic reversals had occurred, these strips ought to reflect them.
On investigation, this turned out to be the case.
On either side of the rift were sediments with normal magnetization, farther away on either side were sediments with reversed magnetization, then normal again, then reversed, and so on, quite symmetrically on either side.
This offered the best evidence so far for the existence of sea-floor spreading, and also for the periodic reversal, at irregular intervals, of the magnetic field.
Of course, if two adjoining plates are pushed apart, two adjoining plates in some other part of the Earth must be pushed together. Thus the study of plate tectonics finally made sense out of mountain-building, volcanoes and earthquakes, the development of ocean deeps and island arcs. In short, plate tectonics became the central dogma of geology, as evolution is of biology, the atomic theory is of chemistry, and the conservation laws are of physics.
πMagnetic Poles
1269 A.D.
FRANCE
In 1269 a French scholar, Pèlerin de Maricourt (13th century), also known by his Latin name of Petrus Peregrinus de Maricourt, was taking part in the slow and dull siege of an Italian city. To pass the time, he wrote a letter to a friend describing his researches on magnets. He described the existence of magnetic poles, regions on a magnet where the magnetic force was most intense, and showed how to determine the north and south poles of a magnet, since like poles repelled each other and unlike poles attracted each other. He also explained that one could not isolate a pole, for if a magnet were broken into smaller pieces, each piece would have both a north and south pole.
This is about the first piece of good scientific experimentation in the modern sense, although it would be more than three centuries before experimental science was well established.
In the same letter, Peregrinus explained that a compass would work better if the magnetic sliver or needle were put on a pivot rather than allowed to float on a piece of cork, and that a graduated circular scale should be placed under it to allow directions to be read more accurately. This was another major step toward making navigation of the open sea a practical task.
╔Producing Microwaves
1921 A.D.
U.S.A.
By this time, many different varieties of radio tubes were being developed. In 1921 the American physicist Albert Wallace Hull (1880-1966) developed a diode that could produce bursts of short radio waves (microwaves) of high intensity. He called it a magnetron, because an external magnet was used to apply a magnetic field to the electrodes inside the tube.
In the next decade, tubes of this sort played a key role in the development of radar.
The Magnetosphere
1958 A.D.
CAPE CANAVERAL, FLORIDA
In 1958 the United States entered the Space Age. The Soviet Union had placed two satellites in orbit in 1957, Sputnik I on October 4 and Sputnik II on November 3. The latter carried a dog, the first living animal to be placed into orbit.
The first successful American satellite was Explorer I, which was launched on January 31, 1958. It carried counters designed to estimate the number of charged particles in the upper atmosphere, and detected about the expected concentrations of particles at heights of up to several hundred miles, but at higher altitudes the number fell to zero. Two other satellites launched soon afterward, one by the United States and one by the Soviet Union, recorded the same phenomenon.
The American physicist James Alfred Van Allen (b. 1914) did not believe the count could really fall to zero. He felt that what happened was that the count went so high it put the counter out of action.
When Explorer IV was launched by the United States on July 26, 1958, it carried special counters that were shielded with a thin layer of lead to keep out most of the radiation (rather like wearing sunglasses to protect the eyes). The radiation that penetrated the lead was not enough to overwhelm the counters, and now the count went up and up and up with increasing altitude -- far higher than scientists had expected.
It appeared that surrounding the Earth, outside the atmosphere, there were belts containing high concentrations of charged particles that moved along the lines of force of Earth's magnetic field. These particles approached the Earth's surface in the neighborhood of the Earth's magnetic field. There they were responsible for the aurorae and, at times of unusually high concentration, for magnetic storms that affected the compass and electronic equipment. These belts were at first called the Van Allen belts but were eventually referred to as the magnetosphere.
This was the first important discovery -- an entirely unexpected one -- to be made as a result of the launching of artificial satellites.
MIsolating Malaria's Cause
1880 A.D.
FRANCE
Malaria is perhaps the most widespread and debilitating disease in the world. It was only the discovery of quinine nearly two and a half centuries before that had made it possible for Europeans to maintain themselves in the tropics.
In 1880 a French physician, Charles-Louis-Alphonse Laveran (1845-1922), isolated the microorganism that caused malaria and, to everyone's astonishment, found it to be not a bacterium but a protozoan, a one-celled animal. It was the first pathogenic organism to be found that was anything but a bacterium.
For this discovery, Laveran received the Nobel Prize in physiology and medicine in 1907.
Other bacteriologists were identifying pathogenic microorganisms, too. In 1880, for instance, the German bacteriologist Karl Joseph Eberth (1835-1926) identified the bacillus that caused typhoid fever.
εM and N Blood Groups
1927 A.D.
U.S.A.
Landsteiner had discovered the A, B, O series of blood groups and demonstrated their importance in blood transfusion. He thought it was possible that other blood groups might exist that were not of importance to transfusion but that might still be of interest in studying heredity, distinguishing between geographically separated human groups, determining paternity questions, and so on.
Thus in 1927 Landsteiner and his group discovered blood groups they designed as M, N, and MN.
The Mapping of Mars
1971 A.D.
HOUSTON, TEXAS
On May 30, 1971, the United States launched the Mars probe Mariner 9, and on November 13, 1971, it arrived at Mars and went into orbit, the first human-made object to be placed into orbit about another planet.
Mars was experiencing a planetwide dust storm as Mariner 9 approached, but fortunately it was possible to have the probe study its small satellites. They were irregular potato-shaped bodies, with craters as "eyes." The longest diameter of Phobos was 17 miles, that of Deimos, 10 miles.
Eventually, when the dust storm died down, Mariner 9 was able to take more than seven thousand photographs of Mars, which served to map it completely. There were no canals, although there was a huge canyon stretching for thousands of miles. It was named Valles Marineris.
There were numerous craters, crowded mostly into one hemisphere, with volcanoes and jumbled terrain in the other. The largest volcano, Olympus Mons, reached a height of 15 miles above base level and had a base width of about 250 miles.
The atmosphere was only about one-hundredth the density of Earth's and consisted almost entirely of carbon dioxide. The temperature was too low for liquid water to exist at any time, and the ice caps of Mars may contain both frozen water and frozen carbon dioxide.
The Distance to Mars
1672 A.D.
CAYENNE, FRENCH GUIANA
Nineteen centuries before, Hipparchus (fl. 146-127 B.C.) had determined the distance to the Moon. Since then, no further heavenly distance had been determined accurately. The parallaxes of all other heavenly bodies were far too small to measure with the unaided eye, and the telescopes weren't quite good enough to do the job.
However, German astronomer Johannes Kepler's (1571-1630) elliptical orbits and his three laws of planetary motion had made it possible to build a model of the Solar System in the proper proportions. If any planetary distance could be obtained, then all the other distances would be known too.
Italian-born French astronomer Gian Domenico Cassini (1625-1712) tackled the job. Thinking his telescope might be good enough if he viewed Mars from two places sufficiently far apart, he sent another French astronomer, Jean Richer (1630-1696), to Cayenne in French Guiana on the northern shore of South America.
In 1672 Cassini determined the position of Mars against the stars as seen from Paris and, using the position of Mars as given in reports from Cayenne, worked out the parallax of Mars. That gave him the distance between Mars and Earth at that time, and from that he could calculate the other distances of the Solar System.
From his figures, he determined that the Sun was 87,000,000 miles from the Earth, as compared with the 5,000,000-mile distance that Aristarchus had estimated. Cassini's estimate was 7 percent too low, but for a first try it was amazingly close.
For the first time, an appropriate idea of the size of the Solar System was obtained. Even allowing for the slightly low figure Cassini had, it was clear that the orbit of Saturn, which was then the farthest known planet, had to be over 1,600,000,000 miles across.
The stars must be farther still. No one yet knew how much farther the stars must be, but Cassini gave human beings the first shocking realization of how small they and their world were compared to the Universe. There were other and greater shocks yet to come.
° The Martian Ice Caps
1784 A.D.
LONDON, ENGLAND
In 1784 Herschel, who had determined the axial inclination of Mars and therefore knew where its polar regions were, noticed that it had visible ice caps in those polar regions. Here was another similarity between Mars and Earth.
ƒLife on Mars
1976 A.D.
CAPE CANAVERAL, FLORIDA
In 1975 two Mars probes had been launched by the United States, Viking 1 on August 20 and Viking 2 on September 9. Both went into orbit about Mars in mid-1976, and they took the best photographs of the Martian surface yet.
On July 20, 1976, Viking 1 came down to the Martian surface at what would have been, on Earth, the edge of the tropical zone. Some weeks later Viking 2 came down in a more northerly position. In coming down, they discovered that the Martian atmosphere, though chiefly carbon dioxide, was also 2.7 percent nitrogen and 1.6 percent argon.
The Martian surface was rocky, as Earth's surface is. The Martian surface, however, was richer in iron and sulfur and poorer in aluminum, sodium, and potassium. There was no sign of life on Mars on a scale visible to the eye. The Viking probes were equipped to run experiments on Martian soil to see if any microscopic forms of life were present. The experiments were carried through with ambiguous results, but there was no trace of organic material in the soil, and this led astronomers to believe that certain lifelike responses to the experiments were the result of some odd chemical behavior of the soil.
There were signs of dry riverbeds, however, complete with tributaries. It may be that in ages past there was a reasonable supply of liquid water on Mars. If so, where did it go, and what led to such an extreme cooling of the planet? @
}Martian Satellites
1877 A.D.
WASHINGTON, D.C.
By now, Jupiter was known to have four satellites, Saturn seven, Uranus four, and Neptune one. Of the inner planets, Earth had one satellite, but no satellites were known for Mercury, Venus, or Mars.
At the 1877 conjunction of Earth and Mars, the American astronomer Asaph Hall (1829-1907) seized the opportunity to make certain that Mars had no satellites. If it did have, they would have to be small and dim, and might well be very close to Mars, whose light would tend to obscure them. Without all three of those qualifications, they would certainly have been seen by now.
Hall therefore began to search the neighborhood of Mars for any signs of little sparks moving about the planet. He worked inward toward Mars's surface and, by August 11, his telescope was trained so close to Mars that its glare was beginning to make it impossible to see anything else. He decided to give it up and assume that satellites were not present, but his wife, Angelina Stickney Hall, urged him to try for one more night.
Hall agreed, and the next night he spotted a small satellite. Five nights of clouds followed, and then on August 17 he noted a second satellite. The satellites were small indeed, the smallest that had yet been discovered, but they were there. Hall named them Phobos (Greek for "fear") and Deimos (Greek for "terror"), after the two sons of Mars (Ares), the god of war.
┐Martian Canals
1877 A.D.
ROME, ITALY
Every 30 years or so, Mars and Earth happen to pass each other where their orbits are closest. Mars is then only 35,000,000 miles from Earth, and astronomers get ready to study it carefully. One of these close approaches (or conjunctions) took place in 1877, and one of those interested was the Italian astronomer Giovanni Virginio Schiaparelli (1835-1910).
For one thing, he tried to map Mars. Even 35,000,000 miles is a large distance, and the Martian atmosphere tends to obscure things (to say nothing of our own atmosphere), so that earlier attempts to map the shadowy markings on Mars had not been very successful; different astronomers saw different markings.
Schiaparelli, however, recorded what he saw with so good a telescope and so clear an eye that, for once, other astronomers saw the same markings he did.
Schiaparelli gave the markings classical names, and others were content to use those names.
Schiaparelli did more. At this time, and at later, less favorable conjunctions of Mars, he detected rather narrow, dark markings. He thought they were bodies of water, so he called the narrow ones channels. The Italian word for channels was canali, and this was mistranslated back into English as canals.
The difference is that channels refers to natural bodies of narrow water, while canals are made by intelligent beings. The notion came into being, then, that Mars was a dying world, with its water slowly leaking into space; and that it was home for a superintelligent race, for whom the canals were a huge engineering development designed to bring water from the polar ice caps to the agricultural tropics. It was nearly a century before that notion was to be quashed once and for all.
Matches
1831 A.D.
FRANCE
For thousands of years, fires had been started by means of friction -- friction that entailed considerable effort.
Then, beginning with the discovery of phosphorus, chemists began to discover chemicals so active that with very little encouragement they could burst into flame. Why not, then, simply coat the edge of a splint of wood with some appropriate chemical that could at the proper time burst into flame and set the wood on fire? You would then have a small fire that would last long enough to ignite a larger and longer-lasting one. You would then have a match (from an old word for the nozzle of a lamp).
Such chemical matches began to be produced in the early 1800s, but the first to be made were too hard to ignite, or too messy, or too dangerously easy to light.
In 1831, however, a French chemist, Charles Sauria, produced the first practical friction match. It contained phosphorus, which was diluted with other materials so that the matches would not start to flame until they were struck on a rough surface. The moderate amount of heat induced by the friction would then suffice to ignite it. Such matches produced flame quickly and quietly when struck, and didn't deteriorate on standing. Their use quickly spread.
There was one catch. The phosphorus used in the matches was quite poisonous, and people who worked at producing the matches would get the phosphorus into their bodies where it caused bone degeneration and killed them slowly and painfully. It took some 70 years before this was corrected.
åMathematics and Logic
1910 A.D.
ENGLAND
Russell and the British mathematician Alfred North Whitehead (1861-1947) collaborated on a monumental three-volume work, Principia Mathematica, the first volume of which appeared in 1910. It was another effort to establish mathematics as a branch of logic, building all of it out of basic definitions and processes. It was the most nearly definitive accomplishment of this sort.
úMatrix Mechanics
1925 A.D.
GERMANY
Beginning with Bohr, physicists had tried to interpret spectral lines (which represented energy given off or taken up as electrons passed from one state to another) using images similar to those used for planets circling a star. They spoke of circular orbits, elliptical orbits, tilted orbits, rotation about an axis (particle spin), and so on.
The German physicist Werner Karl Heisenberg (1901-1976) considered all this useless and misleading. He preferred to take the numbers representing the energy level and manipulate them without regard to their pictured significance.
In 1925 he developed a form of manipulation called matrix mechanics for the purpose.
AMaxwell's Equations
1865 A.D.
SCOTLAND
The culminating work of Maxwell came in 1865 when he began to devise a set of equations (Maxwell's equations), simple in form, that expressed all the varied phenomena of electricity and magnetism and bound them together indissolubly, as Newton had done for gravitation.
Maxwell showed that electricity and magnetism did not exist separately, but that each was an inevitable aspect of the other. There was a single electromagnetic force.
Maxwell showed that the oscillation of an electric charge produced an electromagnetic field that radiated outward from its source at a constant speed. This speed could be calculated from the equations and turned out to be just the speed of light. Maxwell therefore maintained that light was a form of electromagnetic radiation and that the wavelengths of such radiation depended on the oscillation rate of the charge and could be anything -- far shorter than the ultraviolet and far longer than the infrared, for example. (Two decades later, this view was to be confirmed.)
In this way, Maxwell brought about the first unification in physics, or the first bringing under the umbrella of a single set of mathematical relationships such apparently disparate phenomena as electricity, magnetism, and light. Further unifications of this sort were to involve major efforts by later physicists.
ÄA Basis for Electromagnetism
1855 A.D.
UNITED KINGDOM
English physicist Michael Faraday (1791-1867) had introduced the concept of lines of force, but since he knew no mathematics, he could only describe them pictorially.
The British mathematician James Clerk Maxwell (1831-1879) was able to translate Faraday's concept into mathematical form in 1855 and show that the former's intuitive grasp of the subject was completely correct.
The First Evolution Proposal
1809 A.D.
FRANCE
While the fact that biological evolution had taken place was suspected by many scientists, until now no one had suggested a mechanism that would allow it to take place. Why should some catlike creature in the course of generation after generation slowly change, some into lions, some into tigers, and some into pussycats?
The first to attempt an answer was Lamarck in his book Zoological Philosophy, published in 1809. Here he suggested that particular animals might use a part of the body steadily, or not use it, and that those parts might develop slightly or degenerate slightly as a result, and that such developed or degenerated parts could be inherited by their young, which, by use or disuse, would continue the process.
Thus some antelopes, by stretching upward to reach leaves, would gradually develop slightly longer necks and legs, which would be inherited by the young, which, also straining, would continue the process so that the giraffe would evolve. Other antelopes, by dint of constantly fleeing from predators, strengthened their leg muscles and became very fleet as the generations progressed. Water birds, by using their feet to push water backward, developed webs, while moles, who didn't need eyes underground, gradually lost them.
This sort of thing is referred to as the inheritance of acquired characteristics. Experiments would show that acquired characteristics were not inherited. Nevertheless, the advancement of a mechanism for evolution, even if a wrong one, heightened interest in the matter.
2The Mediterranean
1990 A.D.
MEDITERRANEAN SEA
Here, along the northern regions of the Mediterranean Sea, is the home of much of Western philosophy, government and literature.
In the upper right of the picture, that jagged peninsula and those islands you see in this satellite's-eye view is Greece and the Aegean islands, where Socrates and Plato and Aristotle taught philosophies that affect the world today. And there Homer wrote his Iliad and Odyssey, two foundational works of western literature.
Now sail west across the Adriatic Sea to the boot of Italy. A city called Rome, located near the middle of this peninsula, rose to rule a long-lived empire from the British Isles to the Euphrates River, spreading Greek and Roman culture throughout Europe and serving as a model for republicanism, a form of government still influential today. Rome once controlled the Mediterranean so completely that the Romans called it "Mare Nostrum," or "Our Sea."
The Mediterranean was probably first settled because of its pleasant climate and natural harbors. It has been the chief trade route in history and long before ships ventured out into the stormy Atlantic Ocean, the waters of this inland sea were being crisscrossed by trading vessels.
The name Mediterranean is Latin and means "in the middle of land," and it certainly is, though it is not quite enclosed. At its west end it is almost shut off from the Atlantic Ocean by the Strait of Gibraltar, and on the east it narrows at the Dardanelles, which lead into the Black Sea.
It has one other major connection: the Suez Canal. The canal, built in 1869 by the French, cuts across a narrow strip of Egypt to meet the Red Sea, which connects with the Indian Ocean. Though too small for many of today's large ships, the Suez was once a vital shortcut to the East, and is still a shorter route for smaller ships.
(Megavitamin Therapy
1970 A.D.
PALO ALTO, CALIFORNIA
The necessity of vitamins in the diet had been recognized since the work of Eijkman. The dosages required appeared to be small, however -- in fact enzymatic in quantity.
Then it was suggested that the tiny recommended doses were merely those required to prevent the onset of serious disease and that much higher doses were common in primitive human diets that were heavy on fruits and vegetables. It was these much higher doses that might be needed for full health, and people began to speak of megavitamin therapy.
An outstanding proponent of this view was Linus Pauling, who, beginning in 1970, recommended massive doses of vitamin C (ascorbic acid) for health. His views seem not to be accepted by most biochemists, but Pauling's voice is not one that can be lightly ignored.
╢Cell Division
1883 A.D.
BELGIUM
The discovery of the mechanism of cell division by German anatomist Walther Flemming (1843-1905) stimulated many biologists into investigating the matter further.
The Belgian cytologist Edouard Joseph Louis-Marie van Beneden (1846-1910) found that the number of chromosomes in the cells of a particular species was always constant, though the number varied from species to species. (It is now known that there are 46 chromosomes in human cells.)
Furthermore, he discovered that in the formation of the sex cells (that is, the ova and spermatozoa), the division of chromosomes during one of the cell divisions was not preceded by a doubling. Each egg and sperm cell, therefore, ended with only half the usual number of chromosomes. (This halving of number was called meiosis, from a Greek word meaning "to make smaller"). Consequently, when a sperm cell entered an egg cell in the process of fertilization, the chromosomes reached their normal number for the species, half of them coming from the mother and half from the father.
Meiosis fit in perfectly with Austrian botanist and monk, Gregor Johann Mendel's (1822-188) genetic discoveries but those discoveries were still being ignored.
ⁿ Mendelevium
1955 A.D.
BERKELEY, CALIFORNIA
In 1955 Seaborg and his group bombarded einsteinium, element number 99, with protons and formed a few atoms of element 101. They named this new element mendelevium, after Mendeleyev, who had first worked out the periodic table.
ßMercury's Rotation
1889 A.D.
ROME, ITALY
Schiaparelli, who had been the first to see the markings on Mars that were interpreted as canals, went on to study the markings on Mercury.
Mercury was a smaller world than Mars and farther away. It was often lost in the Sun's glare, and when it could be seen best, only a crescent phase was visible.
Nevertheless, Schiaparelli did make out some markings, and since he always saw the same markings when the planet was in a particular position, he concluded, in 1889, that Mercury always presented the same side to the Sun.
Since Mercury was close enough to the Sun for tidal influences to produce this effect, Schiaparelli's suggestion was accepted without serious question for the next three-quarters of a century.
VThe Mapping of Mercury
1974 A.D.
HOUSTON, TEXAS
Mariner 10 had been launched on November 3, 1973. On February 5, 1974, it passed by Venus just 3,600 miles above its cloud layer and then headed for Mercury. On March 19, 1974, it passed within 435 miles of Mercury's surface. It moved into an orbit about the Sun in such a way that it passed near Mercury a second and third time. On the third approach, it passed within 200 miles of Mercury's surface.
Mariner 10 confirmed Mercury's rotation rate and temperature and showed that it had no satellite and no significant atmosphere. It determined the diameter, mass, and density of Mercury with greater precision than had been possible before. In addition, it allowed about three-eighths of Mercury's surface to be mapped.
The photographs it took of Mercury showed a landscape that looked very much like that of the Moon. There were craters everywhere, the largest being 125 miles in diameter. Mercury is not as rich in "seas" as the Moon is. The largest one sighted is about 870 miles across and is called Caloris (heat). Mercury also has cliffs that are a couple of hundred miles long and about 1-1/2 miles high. In addition Mariner 10 discovered that Mercury had a small magnetic field, about a hundredth as intense as the Earth's. This is puzzling, for Mercury does not rotate quickly enough to have a field, if current theories are correct.
gThe Mercury Thermometer
1714 A.D.
AMSTERDAM, NETHERLANDS
As long as thermometers were open to the air, like those of Galileo and French physicist Guillaume Amontons, they were affected by air pressure in one way or another and were always limited in accuracy. The first person to devise a closed thermometer was Ferdinand II de' Medici (1610-1670), who did so in 1654.
At first, sealed thermometers used water or alcohol or mixtures of the two, but these fluids produced vapors that introduced pressure effects. What's more, water didn't expand and contract as evenly with temperature as was needed for good precision, while alcohol boiled at too low a temperature.
The German-born physicist Daniel Gabriel Fahrenheit (1686-1736) worked with alcohol thermometers at first, but in 1714 he made the key advance of using mercury. Mercury stays liquid between quite low temperatures and quite high temperatures, produces very little vapor, and expands and contracts quite evenly with temperature change. It is an ideal fluid for thermometers and is still commonly used for the purpose today.
Fahrenheit made another advance toward the setting of good standard temperatures. He noted the height of the mercury column in a mixture of ice, water, and ammonium chloride, which resulted in the lowest temperature he could get, and he called that 0. A mixture of ice and water he set at 32, and the temperature of boiling water was then 212. This is the Fahrenheit scale, and it is still commonly used in the United States to measure temperature.
The Fahrenheit thermometer was the first that could measure temperature with sufficient accuracy to be useful to scientists.
gMetabolic Intermediates
1905 A.D.
ENGLAND
Harden, who had demonstrated the existence of coenzymes the year before, continued to study the behavior of yeast enzyme on the fermentation of glucose. The enzyme breaks down glucose rapidly at first and produces carbon dioxide, but as time goes on, the level of activity drops off. The natural assumption was that the enzyme broke down with time.
In 1905, however, Harden showed that this could not be so. If he added inorganic phosphate to the solution, the enzyme went back to work as hard as ever. This was a strange finding, for neither the sugar being fermented, nor the alcohol and carbon dioxide produced, nor the enzyme itself contained phosphorus.
Since the inorganic phosphate disappeared, Harden searched for some organic phosphate formed from it, which he located in the form of a sugar molecule to which two phosphate groups had become attached. This sugar phosphate was formed in the course of fermentation; then, after other reactions had taken place, the phosphate groups were removed again. The sugar phosphate was a metabolic intermediate. Harden was the first to isolate such a metabolic intermediate, but other biochemists were soon hot on the trail of such things.
Harden was also the first to indicate the important role that phosphate groups play in metabolism. For this work, he was awarded a share of the Nobel Prize in chemistry in 1929.
ìMeteorites
1803 A.D.
PARIS, FRANCE
Chladni had forced scientists to consider the possibility of meteorites seriously. Continuing reports of stones falling from heaven forced investigation. A French physicist, Jean-Baptiste Biot (1774-1862), was asked to look into reports of such falls in a region 100 miles west of Paris.
After a painstaking investigation, Biot gave it as his opinion that the reports were correct and that meteorites did exist and did fall from the sky.
Presumably, the discovery of the first two asteroids had forced scientists to understand that small bodies might be moving about the Sun and that some might occasionally collide with the Earth.
âMeteorites
1794 A.D.
WITTENBERG, GERMANY
It was the common experience of human beings that objects sometimes fell from the sky. Such falls had been reported. The Kaaba, the sacred black stone of the Muslims, was probably a meteorite that fell from the sky. In Ephesus, a stone was worshipped in the temple of Artemis that was probably a meteorite, and periodically reports of witnessed falls were received.
During the Age of Reason, such tales were discounted and dismissed by men of science.
In 1794, however, a German physicist, Ernst Florens Friedrich Chladni (1756-1827), published a book in which he suggested that meteorites did fall and that this happened because the space near Earth contained the debris of a planet that had once existed but had exploded. This was the first time that a reasonable explanation had been offered for meteorites, and the tide slowly began to turn. It took a while, though.
¿Amino Acids on Meteors
1970 A.D.
U.S.A.
The Sri Lanka-born American biochemist Cyril Ponnamperuma (b. 1923) was continuing to attempt to produce molecules of biochemical interest from the primordial constituents of Earth's atmosphere, in the line of experimentation begun by Miller.
This investigation into life's origins took an unusual turn in 1970 when Ponnamperuma studied a meteorite that had fallen in Australia the year before.
It was of a rare kind called a carbonaceous chondrite, a fragile black material that contained measurable quantities of water and organic material.
Ponnamperuma showed that five different amino acids of the kind that helped make up protein molecules were present in the meteorite.
These meteoritic amino acids did not originate in living tissue, for if they had (judging from the amino acids in living tissue on Earth), they would all have only one of two possible structural arrangements and would rotate the plane of polarized light (be optically active). The amino acids in the meteorite were optically inactive, meaning that they consisted of both structures in equal amounts, so that each canceled the optical activity of the other. This was to be expected if they had been formed by some process not involving life.
Combined with the findings of astrochemistry, this made it seem ever more likely that chemical changes took place in nonliving systems, where conditions were favorable, that would lead in the direction of life.
╬The Metric System
1790 A.D.
PARIS, FRANCE
Throughout history, every nation, sometimes every region within a nation, has developed its own system of measurements. As long as trade was slow and communication was limited, that was merely an annoyance. However, as the economic interdependence of Europe increased rapidly in modern times, the absolute jungle of different measurements was a serious handicap to progress and prosperity. Yet tradition made it almost impossible for any region to give up its time-sanctified system for others merely because the others made more sense and were easier to use.
The French, however, in the grip of their Revolution, thought it a suitable time to develop a system of sensible measurements, and they appointed a commission to work on it, a commission including such men as Laplace, Lagrange, and Lavoisier.
The commission tried to base the system on natural measurements, so that the basic unit of length, for instance, the meter (from a Greek word meaning "to measure"), was to be equal in length to 1/10,000,000 of the distance from the North Pole to the Equator. Other units were worked out to interconnect with the meter, when that was possible, while larger and smaller units were worked out by multiplying or dividing by 10.
This so-called metric system was by far the most useful and logical system of measurement ever dreamed up, and all that stood in the way of its instant adoption was, first, the dead weight of tradition, and second, the hostility of the rest of Europe to the French Revolutionaries. Even so, it gradually spread, and today the metric system is used universally, except in the United States. And even in the United States, the metric system is used by scientists, and increasingly by others.
The metric system represented an improvement in technique, and like other such techniques (writing, the alphabet, Arabic numerals, printing, chemical nomenclature), it may not have advanced scientific knowledge in itself, but it made such advances easier.
àMexico
1519 A.D.
MEXICO
After a quarter-century of sailing about the Caribbean, Spanish explorers had still not encountered the civilizations that existed in the American continents. In 1517, Francisco Fernández de Córdoba (1475?-1525 or 1526), had sailed westward from Cuba and discovered the peninsula of Yucatan.
There he was the first to encounter traces of the Mayan civilization, but that was a civilization in ruins.
Westward, however, across the Gulf of Mexico, lay the still flourishing Aztec Empire, which controlled all of central and southern Mexico and had a population of about five million.
In 1519 some 600 Spaniards under Hernán Cortés (1485-1547) landed with 17 horses and 10 cannon. That this small force sufficed to destroy the Aztec Empire is not as surprising as it may sound and does not imply that Europeans were innately superior to the Aztecs. For one thing, the Aztecs had nothing to counter either the horses or the cannon. For another, the subject peoples of the Aztecs were restive and ready to fight on the side of Cortés.
Finally, the Aztecs and their king, Montezuma II (1466-1520), had the superstitious feeling that the Spaniards were gods whose coming had been predicted, and they did not resist strongly until it was too late.
So the Aztec Empire was destroyed and Mexico was taken over by Spain. No effort was made to save the Aztec culture or retain information concerning it.
δMachine Guns
1862 A.D.
U.S.A.
The Colt revolver, which had come into use two decades before, was not the last word, of course. Repeating rifles, called carbines, had come into use in 1860. More destructiveness was wanted, though -- an indefinite stream of bullets.
The American inventor Richard Jordan Gatling (1818-1903) sought to devise a gun that could fire bullets out of a chain of cartridges and that wouldn't stop until the chain ran out. By November 1862 he had developed a rapid-fire gun that could shoot nearly six bullets per second, though it had to be hand-cranked.
This Gatling gun was the first machine gun and it was used by the Union forces toward the end of the Civil War. Gatling's name lives today in the slang term gat, used for any handgun.
J The Michelson Interferometer
1881 A.D.
CLEVELAND, OHIO
In 1881 a German-born American physicist, Albert Abraham Michelson (1852-1931), devised an interferometer, with the financial help of Bell (1847-1922), who had invented the telephone five years before.
This device acted to split a beam of light in two, send the parts along different paths, then bring them back together -- a way of treating light that British mathematician James Clerk Maxwell (1831-1879) had suggested six years before. Then, no one had had an instrument capable of the job; now Michelson had one.
If the two portions of the light traveled precisely the same distance at the same speed, they would then come back together in phase, and the light would be unchanged. If their distance or speed were slightly different, however, the two beams would be slightly out of phase when they rejoined, and interference fringes should be set up such as those English physicist Thomas Young (1773-1829) had detected and used to prove the wave nature of light.
At this time, it was thought that light, being a wave, had to be a wave of something. Consequently, it was supposed that all space was filled with a luminiferous ether. (The word luminiferous is from Latin, meaning "light-carrying," and ether harks back to Aristotle's aether -- see 350 B.C., Five Elements.) This luminiferous ether was thought to be in a state of absolute rest, and the Earth was thought to be moving at some particular speed relative to it, called Earth's absolute motion.
Michelson used his interferometer to measure Earth's absolute motion by sending two halves of a light beam traveling at right angles to each other. Light sent in the direction of Earth's motion through the ether and back again ought to complete its trip a little sooner than light traveling at right angles to the motion and back. Therefore the two halves of the light should rejoin out of phase, and by measuring the width of the interference fringes, one should be able to measure the speed of Earth relative to ether. Once that was known, the absolute motion of all other bodies should follow.
However, the experiment failed. No interference fringes were found. Michelson assumed there was something wrong with the experiment and set about refining it. It took years before he was satisfied that there truly were no interference fringes. That observation helped revolutionize science.
NMicheleson-Morley Experiment
1887 A.D.
U.S.A.
Michelson, who had hoped to determine the Earth's speed of motion through the stationary ether, continued to improve the delicacy of his procedure and of his instruments, and to repeat the experiment. Finally, in 1887, with the help of a colleague, the American chemist Edward Williams Morley (1838-1923), Michelson ran a definitive experiment and, once again, found no interference fringes.
There had to be an explanation. Either the Earth was motionless with respect to the ether, or the Earth dragged the ether with it, or something. All possible explanations seemed highly unlikely, and for nearly a quarter of a century, the world of science was completely puzzled. It took a scientific revolution to explain the matter, so that the Michelson- Morley experiment is perhaps the most important "failure" in the history of science.
=Microwaves off the Moon
1946 A.D.
BUDAPEST, HUNGARY
Thanks to radar, it was possible to detect microwave reflections from airplanes, and from the reflections to calculate the distance and direction of the airplanes. In principle, there was no reason this could not be done for an astronomical body.
In 1946 a Hungarian scientist, Zoltan Lajos Bay, sent a beam of microwaves to the Moon and detected the reflection. The time it took for the reflection to return could be used to determine the distance of the Moon at the time of reflection with far greater precision than had ever been possible before.
¡Microfossils
1965 A.D.
U.S.A.
Until this time the earliest fossils had been found in rocks of the Cambrian era and were a little over 600 million years old. However, the Earth is 4,500 million years old. This meant that the first seven-eighths of Earth's history seemed to show no signs of life. This seemed unlikely, since the earliest fossils were already well developed and quite specialized forms of life that could not have come into existence without a long evolutionary history. The trouble was, though, that prior to the Cambrian era, organisms had not yet developed shells and other hard parts, and softer tissues do not fossilize easily.
In 1965, however, the American paleontologist Elso Sterrenberg Barghoorn (1913-1984) worked with tiny bits of carbonized material in very ancient rocks and showed that they might represent bacteria living in the early eons of Earth's history. When these bits of material were eventually studied by electron microscope, they showed themselves unmistakably to be microfossils, or remnants of simple cells. Some were found in rocks as old as 3,500 million years.
Consequently it appeared that life arose no later than a billion years after the formation of the Earth.
£Microscopes
1590 A.D.
AMSTERDAM, NETHERLANDS
It must have dawned on people rather early that there were ways of making small objects appear larger in size. Dewdrops on a leaf or on a blade of grass will make the surface they rest on look larger. Spheres of glass will do the same.
The people who would most notice this sort of thing and be most concerned with it were the spectacle-makers, since the convex lenses used to correct far-sightedness acted to magnify objects.
The spectacle-making industry was most advanced in the Netherlands at this time. It occurred to a Dutch spectacle-maker, Zacharias Janssen (1580-ca. 1638), that if one lens magnified somewhat, two would magnify to a greater extent. He placed a convex lens at each end of a tube and found that magnification was indeed improved. The improvement wasn't great, but Janssen's tube can be viewed as the first microscope, and its descendants were to revolutionize biology.
The Middle East
1990 A.D.
THE MIDDLE EAST
What Greece and Rome have been to Western government and philosophy, the Middle East has been to its religious life.
All three of the major western religions (Judaism, Christianity and Islam) have their origin in this area.
At the eastern edge of the Mediterranean Sea, on the right of the picture, is Israel, the home of the Jewish and Christian faiths. Further to the east, across the desert of Saudi Arabia, is Mecca, the most holy city of Islam, and the site where Muhammad first began teaching.
VElectron Charge
1911 A.D.
UNITED STATES
The ratio of the electric charge of the electron to its mass had been worked out and compared with that of ordinary ions by British physicist Joseph John Thomson (1856-1940). The size of the electric charge in an absolute sense, however, was not known.
The American physicist Robert Andrews Millikan (1868-1953) tackled the job. Beginning in 1906, he had followed the course of tiny electrically charged water droplets falling through air, under the influence of gravity, against the pull of a charged plate above. The evaporation of the water confused the results, and in 1911 he began to use tiny oil droplets instead.
Every once in a while, such an oil droplet attached itself to an ion, which Millikan produced by passing X-rays through the chamber. With the ion added, the effect of the charged plate above was suddenly strengthened and the droplet would fall more slowly or perhaps even rise. The minimum change in motion was due, Millikan felt, to the addition of a single electronic charge. By balancing the effects of the electromagnetic attraction upward and the gravitational attraction downward, both before and after such an addition, Millikan was able to calculate the charge on a single electron. The figure we now have is 16- quintillionths of a coulomb.
For this work, Millikan was awarded the Nobel Prize in physics in 1923.
█The Milky Way
1609 A.D.
AMSTERDAM, NETHERLANDS
The Milky Way is a dim band of foggy light that encircles the sky. Many were the speculations as to what it was. It might be a spurt of milk from a goddess's breast, or it might be a bridge used by the gods to travel from Earth to Heaven or vice versa. Democritus suggested that the Milky Way was a conglomeration of vast numbers of stars that were individually too dim to be seen. That, however, was just a speculation.
In 1609, however, Galileo heard rumors of the construction of a telescope in the Netherlands the year before. From what he heard, he had little trouble devising a telescope for himself, and for the first time, he turned one on the sky.
When he looked at the Milky Way through the telescope, he found that it was indeed composed of a myriad of faint stars. Democritus had been absolutely correct.
In fact, wherever Galileo looked he saw additional stars that, without the telescope, were too dim to be seen. The sky was full of them.
ëMiranda
1948 A.D.
LONDON, ENGLAND
For almost a century, Uranus had been known to have four satellites. In 1948, however, Kuiper, who had described the atmosphere of Mars, located a fifth Uranian satellite. It was smaller than the other four and closer to Uranus. Since three of the satellites had been named for spirits from Shakespeare's plays -- Oberon and Titania from A Midsummer Night's Dream and Ariel from The Tempest -- Kuiper named the new satellite Miranda, after the heroine of The Tempest.
Miranda was the first satellite to be named after a human being rather than a god, a goddess, or a spirit, although it was a fictional human being, to be sure.
OMirrors
1291 A.D.
VENICE, ITALY
Until now, glass had almost always been colored. It was in Venice that the technique for adding decolorizing material to glass was developed and where glass was first formed that was reasonably clear and transparent. Though uncolored glass might seem boring, it turned out not to be so. Clear glass struck people as beautiful, and to have cups and other objects made of it proved very desirable.
In 1291 Venice removed its glass-manufacturing establishment to a guarded island and set up stiff penalties for anyone revealing any manufacturing secrets. It did its best to maintain a strict monopoly of the valuable material, and Venetian glass continued to be considered the height of luxury.
One thing that clear glass made possible was the modern mirror. In ancient times, people could see themselves in still water or in the polished surface of a metal such as bronze. Water rarely remained still for long, however, and polished metal was expensive. The result was that very few people knew what they looked like or could do something as simple as arrange their own hair.
A sheet of clear glass, however, could be backed with a film of metal, and the result was a luminously clear mirror in which it was possible to study one's own face to one's heart's content. (It is not for nothing that a mirror is also called a looking-glass.)
wThe Mississippi River
1541 A.D.
MISSISSIPPI RIVER
The interior of the American continents was being increasingly explored. Cortés explored what is now northern Mexico and in 1536 discovered the peninsula of Baja California.
In 1539 the Spanish explorer Hernando de Soto (ca. 1500-1542) was commissioned by Charles V to land in Florida and add it to the Spanish dominions. De Soto did more than that. Over the space of three years, he explored what is now the southeastern portion of the United States. In 1541 he and his men were the first Europeans to see the Mississippi River. He crossed it but returned to it in the spring of 1542 and died on its banks.
≤Mountain Climbing
1786 A.D.
SWITZERLAND
Mountains are impressive, and because they reach toward the sky and their tops are not attainable by human beings without a great deal of trouble, they were often assumed to be the abode of gods. The connection of Mt. Olympus with the Greek gods and of Mt. Sinai with the God of the Bible are examples.
Generally, human beings admired mountains but avoided them. If it was absolutely necessary to get to the other side, they searched for comparatively accessible "passes." Some climbing had been done for scientific purposes, however. Thus, the Swiss naturalist Conrad Gesner (1516-1565) had climbed mountain peaks in the Alps to search out alpine species of plants.
By the 1700s, however, scientists had grown increasingly interested in mountains -- in the plants and animals living there, in the nature of the rocks, and in the glaciers that frosted their peaks. The Alps were the mountains most available to west-European scientists, and their highest peak is Mount Blanc (French for "white," because its peak is white with snow and ice at all times). It is 15,700 feet high. No one had climbed it, of course, and it was universally regarded as the act of a lunatic to try.
However, a prize was offered for the first person who could accomplish the feat, and in 1786 a French doctor, Michel-Gabriel Paccard (1757-1827), along with a porter, Jacques Balmat, won the prize.
As often happens once one person accomplishes a feat previously considered impossible, others at once find out they can duplicate it. Paccard's climb initiated a virtual frenzy of mountain-climbing (among British aristocrats particularly). Sometimes this was for scientific purposes, but often it was merely for the excitement and adventure of it, as was the case with ballooning.
The Mobius Strip
1865 A.D.
GERMANY
In 1865 the German mathematician August Ferdinand Möbius (1790-1868) presented what came to be called a Mobius strip. This is a long, flat strip of paper (or other flexible material) that is given a half twist and the two ends then pasted together to give a circular figure. The resulting construction has but one edge and one side.
This made Möbius one of the founders of topology, the branch of mathematics that deals with those properties of figures that are not altered by deformations (as long as there is no tearing).
@X-Ray Diffraction
1917 A.D.
U.S.A.
The Braggs had shown how crystal structure could be worked out by X-ray diffraction. Intact and reasonably large crystals are hard to come by, however, and it represented a great advance when the Dutch-born American physicist Peter Joseph William Debye (1884-1966) showed, in 1917, that useful results could be obtained when X-rays were diffracted by powdered solids that consisted of tiny crystals oriented in every direction.
The technique was also discovered independently, and at about the same time, by the American physicist Albert Wallace Hull (1880-1966).
bIronclad Warships
1862 A.D.
HAMPTON ROADS, VIRGINIA
In 1862 the American Confederacy raised a scuttled Union ship, the Merrimack, from its resting place near Norfolk, Virginia, re-named the ship Virginia, covered her with iron plates, placed a cast-iron ram under the waterline, and outfitted her with 10 guns.
On March 8, the ironclad Merrimack attacked the wooden Union ships that were blockading the port and sank them. She was absolutely untouchable by the Union guns. For a while it seemed as though the Merrimack could single-handedly take on and destroy the entire Union navy and break the blockade. The Confederacy could then, with British help, win its independence.
However, an American engineer of Swedish birth, John Ericsson (1803-1889), had already built an ironclad vessel, the Monitor, for the Union. It was small, floated very low in the water, and had two guns. It sailed south just as the Merrimack was launching its attack. On March 9, only one day after the Merrimack's, triumph, the Monitor arrived, and there was a 5-hour fight in which neither ship could damage the other. However, the Merrimack sprang a leak, moved into dry dock, and never left again, so the Union was saved.
It was clear to the whole world, however, that wooden warships were now obsolete, and every navy (including especially the British) began the process of converting itself into an ironclad force.
vMonotheism
1375 B.C.
EGYPT
It is customary for people to believe in a multitude of separate supernatural influences. Every object -- the Sun, the Moon, trees, animals, even abstractions such as tribes and nations -- must have its supernatural accompaniment, cause, or protector.
The first person we know of to suppose that there was only one divine influence that controlled everything was an Egyptian pharaoh named Amenhotep IV, who reigned over Egypt from 1379 to 1362 B.C. He accepted the Sun-god as the one and only god, and this makes some sense, since the Sun is an overriding influence on Earth and on humanity. The Sun-god was, to him, Aton, and he called himself Akhenaton, meaning "Aton is satisfied." His 17-year reign was a failure, however, because his views were not accepted by the priesthood or by the Egyptian people, who clung to their old ways.
It is possible, however, that the Akhenatonic tradition lingered among a few and influenced Moses, the legendary leader who brought the Israelite slaves out of Egypt, according to the Bible, about a century and a half after Akhenaton's time. (The later Jews attributed monotheism to the legendary Abraham, about four or five centuries before Akhenaton, but there is no record of Abraham outside the Bible.)
Monotheism was a clear advance over polytheism, since it reduced the chaos of the supernatural and made possible a more orderly theology.
█Craters on the Moon
1609 A.D.
PISA, ITALY
Galileo also looked at the Moon through his telescope. He found that it contained craters, mountains, and dark areas that he thought might be seas.
These dark areas are still called maria, which is the Latin word for "seas." It was quite obvious that the Moon was not a heavenly globe of light, but was a world that in some ways resembled Earth. Aristotle's notion that heavenly bodies were of a structure different from that of Earth thus received a blow.
ÿThe Moon at Close Quarters
1966 A.D.
MOSCOW, USSR
On February 3, the Soviet Moon probe Luna 9 made the first soft landing on the Moon (one in which the landing vessel was not destroyed in the process) and took some photographs of the approaching surface. On June 2, the American Moon probe, Surveyor 1, did the same, taking many more photographs of better quality.
On April 3, the Soviet probe Luna 10 was the first to be placed into orbit about the Moon. The first of a series of American probes to go into orbit about the Moon (the Luna Orbiters) followed, and the United States was able to map the entire surface of the Moon, both the side facing us and the side away from us, in full detail.
ÖThe Distance to the Moon
150 B.C.
ATHENS, GREECE
In astronomy it is necessary to work with angles. You can't measure the distance between two heavenly bodies by holding a yardstick against the sky. You can only measure the angle you must turn your head in looking first at one, then at the other.
If you make the angle part of a right triangle, then the sides have fixed ratios to one another. The ratios have names like sine, cosine, and tangent. They are examples of trigonometric functions.
The Greek astronomer Hipparchus (fl. 146-127 B.C.), usually considered the greatest of ancient astronomers, was the first to make up careful tables relating angles to side ratios, so that if you knew the angle, you could look up the ratios, and vice versa. For this reason, Hipparchus is usually considered the founder of trigonometry.
Hipparchus used trigonometry to calculate the distance from the Earth to the Moon. First he noted the Moon's position against the stars from different positions on Earth, because when your point of view changes, a relatively near object seems to change position in comparison to a relatively distant one; this is called parallax. The smaller the shift with a fixed change of position, the greater the distance to the nearer object. Once he had measured the parallax of the Moon, he could determine by trigonometry the distance of the Moon, at least in terms of the Earth's size. In this way Hipparchus calculated that the Moon was at a distance equal to 30 times the Earth's diameter.
If, as Eratosthenes had determined, Earth had a circumference of 25,000 miles, it had to have a diameter of 8,000 miles. That meant that the Moon was 30 times 8,000 miles, or 240,000 miles away (which is very nearly correct). That's nearly a quarter of a million miles away, and yet the Moon was well known to be the nearest of the heavenly bodies.
This was the first indication that the Universe was far larger than had been thought, but it was also a dead end. Parallaxes grow smaller as objects grow more distant, and the Moon is the only object close enough to give a measurable parallax to the unaided eye.
Hipparchus also worked out in detail the mathematics of an Earth-centered planetary system.
º Size of the Moon and the Sun
280 B.C.
GREECE
It is easy to suppose that the heavenly bodies are insignificant in size compared to the enormous Earth. After all, the stars are just specks of light on the vault of a sky that looks as though it barely clears Earth's high mountains. The Sun and Moon have visible orbs, but they seem small too. To suggest otherwise would certainly have been considered foolish, or worse.
Thus, when the Greek philosopher Anaxagoras (ca. 500-ca. 428 B.C.) suggested that the Sun was a rock the size of southern Greece, he horrified the Athenian conservatives, who accused him of irreligion, brought him to trial, and forced him into exile.
Two centuries had passed since then, and the Greek world had expanded enormously. With its horizons broadened, daring thoughts were better tolerated, and the Greek astronomer Aristarchus (fl. ca. 270 B.C.) was the first to try to determine the size of the heavenly bodies.
About 280 B.C., he noted the size of the shadow cast by Earth on the Moon and, following a correct line of mathematical argument, estimated that the Moon was a body with a diameter one-third that of the Earth. His result was a little high because he lacked the instruments with which to measure the shadow accurately.
Aristarchus also tried to determine the relative size of the Moon and the Sun by trigonometry. He noted that at the time the Moon was in its half-phase, the Moon, Sun, and Earth were at the apexes of a right triangle. Thus, if the angles were measured, the lengths of the sides could be calculated. Aristarchus's mathematics was correct but again he was victimized by the lack of instruments with which to make accurate measurements. He ended by deciding that the Sun was 20 times as far from the Earth as the Moon was and that the Sun had therefore seven times the diameter of the Earth. This turned out to be a gross underestimate, but Aristarchus was nevertheless the first to show, by scientific reasoning, that the heavenly bodies were objects comparable to the Earth in size.
A consideration of the Sun's huge size possibly led Aristarchus to maintain that the Sun, and not the Earth, was the center of the Universe, and that the various planets, including the Earth, revolved about the Sun. He had no evidence for this, and the notion did not convince anyone. Even if the Sun were a huge body, it was considered an insubstantial ball of light, and the thought of the solid, heavy Earth revolving around it seemed ridiculous.
∙Temperature of the Moon
1930 A.D.
PASADENA, CALIFORNIA
Nicholson, who discovered Jupiter IX, also developed sensitive heat- measuring devices that could determine the surface temperature of an astronomical body such as the Moon from the amount of heat it delivered to the instrument. By using it he could show that the surface temperature of the Moon dropped nearly 200° C during the period of its eclipse by the Earth's shadow.
The Moon had no ocean or atmosphere to conserve and circulate heat, and its solid body was so poor a heat-conductor that the surface lost a great deal of heat before any new supply could work its way upward from the deeper layers.
In 1930 Nicholson and Edison Pettit obtained the first reasonably accurate measurement of the temperature of the lunar surface. As corrected by work since, it seems that the sunlit side of the Moon reaches a maximum temperature of 117° C, which is well above the boiling point of water. The night side of the Moon, after two weeks without sun, sinks to a temperature, just before dawn, of -169° C, far colder than Antarctica at its coldest.
Since the Moon is at Earth's average distance from the Sun, we see how fortunate it is that Earth has a faster spin and shorter day, an ocean to conserve heat, and an atmosphere to distribute it. @
«Morphine
1805 A.D.
GERMANY
The use of certain plants to dull pain and discomfort and to give a feeling of well-being is old indeed. In Homer's Odyssey, mention is made of those who ate the lotus and forgot all else, craving only to continue eating it. There is also mention of a drug nepenthe, which calmed and soothed.
It is very tempting to think of these as representing opium, which Dioscorides described. (Opium is one item that traveled from the West to the Fast East, and not vice versa.) An alcoholic extract of immature opium blooms was called laudanum and had first been introduced by Paracelsus.
In 1805 the German chemist Friedrich Wilhelm Adam Ferdinand Serturner (1783-1841) isolated a chemical from laudanum that he found to be the active ingredient. It was much more efficacious in dulling pain and inducing sleep than the juice itself. It was eventually called morphine, from the Greek word for "sleep."
Morphine has been an important adjunct to medical practice ever since, though its addictive effect was not at first understood. Its discovery initiated the study of alkaloids, which are important nitrogen- containing plant products with marked physiological effects even in small doses.
√Morse Code
1838 A.D.
WASHINGTON, D.C.
The idea of a telegraph had occurred to a number of people, including American physicist Joseph Henry (1797-1878) and the British inventor Charles Wheatstone (1802-1875). It was just a matter of setting up a long wire and sending electricity through it in pulses by opening and closing a key. Combinations of pulses could be interpreted as letters and words.
What was needed was not so much a scientist, however, as a promoter, who could raise the necessary money to set up a sufficiently long wire, with relays to keep the signal from fading with distance. One such promoter, who had been working on the task since 1832, was the American artist Samuel Finley Breese Morse (1791-1872).
In 1838 he produced a logical list of short and long electric impulses (dots and dashes) for the various letters of the alphabet.
This is called the Morse code to this day. It was the simple combination in Morse code of "... --- ..." that made the letter equivalents, SOS, the international distress call.
@Mortality Tables
1693 A.D.
ENGLAND
Death was death and human beings had to learn to accept it stoically. It did not occur to people to subject so universal and somber a fact to statistical evaluation until 1693, when Edmond Halley (1656-1742) prepared the first mortality tables, relating the death rate to age. It may seem perfectly obvious that the older you get, the more likely you are to die, but it is always useful to know something by observation rather than by assumption (however reasonable). Besides, careful mortality tables might show aspects of death that were not the result of age.
êMosquitoes and Malaria
1897 A.D.
LONDON, ENGLAND
Smith's discovery of the manner in which ticks served to communicate disease turned the minds of pathologists in the direction of stinging insects as possible disease-spreaders.
The British physician Ronald Ross (1857-1932) devoted himself to collecting, feeding, and dissecting mosquitoes until in 1897 he discovered the malarial parasite that had been identified by Laveran in the anopheles mosquito. This meant that malaria might well be fought by wiping out the breeding places of these mosquitoes, by making use of mosquito netting, and so on.
For this, Ross received the Nobel Prize in physiology and medicine in 1902.
╧The First Movie
1889 A.D.
MENLO PARK, NEW JERSEY
Once photography had been invented, it seemed natural to use it to simulate motion. If photographs are taken of a moving object in quick succession and flashed before the eyes rapidly, the eye retains an image of each for a brief while, so that all the flashings melt together and are not seen as separate images. Instead, the object photographed seems to move.
Such devices were constructed, but generally they showed very brief movements that might be repeated over and over again. Primitive as such devices were, they amused the audience.
American inventor Thomas Edison thought of a way to extend such illusions and perpetuate them for a considerable length of time. He used a strip of film, of the type brought into production by Eastman, and took a series of closely spaced photographs of a moving object, which he placed along its length. The film could then be moved by means of perforations along the sides over sprocket wheels, which could push the film in front of a flashing light at a carefully regulated speed.
In effect, Edison had invented motion pictures. With a steady stream of improvements, they developed into a giant industry as indispensable to modern life as the automobile.
Electric Motors
1831 A.D.
U.S.A.
Henry discovered electrical induction independently of Faraday, but the latter published first by a few months and gets the credit. Henry went on to study the reverse process. If the rotary motion of a copper wheel cutting across magnetic lines of force can induce an electric current, then an electric current ought to be able to produce a rotary motion.
In essence, Faraday had already shown this in a simple way, but in 1831 Henry devised a much more practical version of such a machine, one in which a wheel would turn if electric current was supplied. This was the first practical electric motor (from a Latin word meaning "to move").
The importance of the motor cannot be overemphasized. A motor can be made as large or as small as desired. It can be run by electricity brought to it over a distance of many miles. Most important of all, it can (unlike a steam engine) be started in a moment and stopped in a moment.
The supply of cheap, abundant electricity made possible by Faraday's discovery of the generator (once it was sufficiently improved) would have been useless without some means of putting it conveniently to work. Henry's motor (once it was sufficiently improved) did that, so that between them, Faraday and Henry ushered in the age of electricity.
cThe Discovery of Oxygen
1774 A.D.
ENGLAND
Joseph Priestley (1733-1804) worked with mercury in his collection of gases and could not help using it more directly in his experiments. Mercury, when heated in air, will form a brick-red compound, which we now call mercuric oxide. Priestley heated some of this compound in a test-tube by using a lens to concentrate sunlight upon it. When he did this, the compound broke up, liberating mercury, which appeared as shining globules in the upper portion of the test-tube.
In addition, a gas was given off that possessed most unusual properties. Combustibles burned more brilliantly and rapidly in it than they did in ordinary air. Mice placed in an atmosphere of this gas were particularly frisky, and
Priestley himself felt "light and easy" when he breathed it. When French chemist Antoine Lavoisier heard of the experiments of Priestley and of Rutherford, he realized in the light of his own experiments that air must consist of a mixture of two gases: one-fifth was Priestley's gas, which Lavoisier named oxygen (from Greek words meaning "acid producer," because it was mistakenly felt at the time that all acids contained oxygen), and four-fifths were Rutherford's gas, which Lavoisier named azote (from Greek words meaning "no life"), but which later came to be known as nitrogen.
Clearly, it was oxygen that supported combustion and animal life and oxygen that was involved in rusting. Animals must consume oxygen and produce carbon dioxide, and from Priestley's earlier experiment, plants must consume carbon dioxide and produce oxygen. Between these two forms of life, the atmosphere's makeup remained stable.
@Working with Platinum
1800 A.D.
ENGLAND
Platinum, because of its inertness and its high melting point, would be marvelously suited to laboratory equipment if only it could be easily worked and pounded into shape. A method for doing so was worked out by a British chemist, William Hyde Wollaston (1766-1828), in 1800. He kept his method secret and never allowed anyone in his laboratory. In this way he earned a fortune. He arranged to have his method published after his death.
In working with platinum, he discovered two other metals very similar in properties to it. These were palladium and rhodium.
Naming the Moon's Features
1651 A.D.
ROME, ITALY
In 1651 Italian astronomer Giambattista Riccioli (1598-1671) published Almagestum Novum (New Almagest). The reference to Ptolemy's (2nd century) old book was not accidental, for Riccioli rejected heliocentricity and insisted on an Earth-centered astronomy a full century after Copernicus's book had been published.
The book, however, included a map of the Moon, with names given to the various craters. Riccioli began the habit of naming surface features on other worlds after astronomical notables, and many of his names are still used. Of course, he gave the most conspicuous crater on the Moon the name of Tycho, whom he admired extravagantly. Another large one was Ptolemaeus. Copernicus is a pretty notable crater, and Kepler is not bad either.
~A Tool for Multiplication
1614 A.D.
SCOTLAND
Numbers can be written in exponential form. Thus, 2^4 is four twos multiplied together, or 16; while 2^5 is five twos multiplied together, or 32. Nine twos multiplied together, or 2^9, is 512. Since 16 x 32 = 512, we can say that 2^4 x 2^5 = 2^9. Instead of multiplying numbers, we add exponents. This turns out to be a general rule. In the same way, instead of dividing numbers, we can subtract exponents.
If 16 is 2^4 and 32 is 2^5, then 22 must be 2 to some exponent that lies between 4 and 5. If we had the exponents for all numbers listed in a convenient table, multiplication would be reduced to addition, and division to subtraction, with a great saving in time and trouble.
The Scottish mathematician John Napier (1550-1617) spent years working out formulas that would give him appropriate exponents for a great many numbers, and he called them logarithms (from Greek words meaning "proportionate numbers"). In 1614, Napier published his table of logarithms and they at once became useful in all sorts of complicated computations that scientists were forced to make. Nothing better was to come along for over three centuries.
pThe First Nation
3100 B.C.
EGYPT
As city-states enlarged their boundaries and grew more populous, their territories were bound to run into each other and their interdependence to grow.
Just as it was necessary to organize matters within a city-state when irrigation came into use, it became necessary to organize matters still further throughout all the city-states of a particular river. It did no good for one city-state to keep its irrigation ditches and levees in tip-top shape if another one upstream allowed its own to go to pieces and produce an untimely flood, or cut the flow of water downstream.
There was therefore pressure for union, and this was carried out first in Egypt. The ease of communication along the Nile tended to even out differences, and all the city-states for 500 miles along the river had the same culture and the same language.
About 3100 B.C., the city-states of the Nile delta (lower Egypt) were united with those south of the delta (upper Egypt) under the rule of Menes, the first king of the First Dynasty. (An Egyptian priest, Manetho, about 300 B.C., wrote a history of Egypt and divided its rulers into dynasties, each one representing a family whose members ruled over Egypt for a period of time.)
Since the Egyptian city-states shared a common language and culture, Egypt can be viewed as what we would today call a nation. It was the first nation the world had seen.
╟Neanderthal Man
1856 A.D.
GERMANY
In western Germany, in the Neander River Valley (Neanderthal in German), workers were clearing out a limestone cave in 1856 and came across some bones. This was not unusual, and what was commonly done in such cases was to throw away the bones. This time, though, the word reached a professor at a nearby school, and he managed to salvage about 14 of the bones, including a skull.
By this time, geologists were sure the Earth was very old, and biologists were sure that human beings had been alive for much longer than the Bible seemed to indicate. But however long human beings had been alive, had they always been human beings, or had they evolved from some simpler form?
The bones from the Neanderthal cave were clearly human, but the skull was rather different from those of modern humans. It had pronounced bony ridges over the eyes, a backward-sloping forehead, a receding chin, and unusually prominent teeth.
The remains were quickly dubbed Neanderthal man and the question arose as to whether it was a primitive form of human being or merely an individual with some bone disorder. The chief supporter of the view that it was a primitive form of humanity was a French anthropologist, Pierre-Paul Broca (1824-1880), and he won out eventually.
Nowadays, we believe Neanderthal man to be a subspecies of Homo sapiens. Nevertheless, the 1856 finding was the first step toward the demonstration, through fossil remains, of the evolution of the human species.
╠A Vacuum in Space
1930 A.D.
SANTA CRUZ, CALIFORNIA
Three centuries earlier, it had come to be understood that there was a vacuum between the astronomical bodies. It was all too easy then to assume that the vacuum was perfect; that there was really nothing at all once one got outside any atmosphere that might be clinging to the immediate surface of a body.
In 1930, however, the Swiss-born American astronomer Robert Julius Trumpler (1886-1956) noted that the light of the more distant globular clusters was dimmer than would be expected from their sizes. The more distant the cluster, the more marked this departure from the expected brightness. What's more, the more distant the cluster, the redder the light.
The easiest way of explaining this was to suppose that space, even far from sizable bodies, was not a perfect vacuum. (Indeed, a perfect vacuum does not exist and probably cannot exist in the Universe.) There are thin wisps of gas and dust throughout interstellar space, and over vast distances, there is enough of this -- of dust, particularly -- to dim and redden light. By taking the dimming effect of this interstellar matter into account, the size of the Galaxy was shown to be somewhat smaller than Shapley's too-large estimates.
`Nebular Photography
1880 A.D.
U.S.A.
As the art of photography advanced, it grew steadily more important in astronomy. In 1880 Draper, who had learned the use of dry plates from Huggins, used the new technique to photograph the Orion nebula and to study its spectrum. It was the first time a nebula had been photographed.
From its spectrum, it was possible to deduce that the Orion nebula was a cloud of dust and gas lit by stars that must be embedded in it. It would be natural to suppose, as a result, that all other nebulas might be of such composition, but within 40 years it turned out that there were all-important exceptions.
5Nebular Hypothesis
1796 A.D.
FRANCE
Kant's suggestion that the Solar System had formed from the condensation of a vast nebula of dust and gas had gone mostly unnoticed.
In 1796, however, Laplace had published a popular nonmathematical book on astronomy and, in the appendix, had made a similar suggestion, describing it in much greater detail. As the condensing cloud spun faster and faster, he explained, first one ring of gas, then another and another were given off. The rings condensed to form the planet. The planets, in condensing, gave off smaller rings that formed the satellites.
Laplace felt that certain nebulas visible in space were themselves contracting and represented planetary systems in the process of formation. His suggestion was therefore called the nebular hypothesis. It proved very popular with astronomers for a time.
▐Nebulae
1771 A.D.
FRANCE
The hungry search for comets became so important to some astronomers that it seemed to consume them. One such was the French astronomer Charles Messier (1730-1817), who discovered 21 comets, but who was depressed whenever some other astronomer discovered one he had missed, or when he was kept away from his telescope as, for instance, when his wife was on her deathbed.
He was irritated by the false hopes aroused by the sighting of some fuzzy object that turned out not to be a comet but a nebulosity fixed to some spot in the heavens. In 1771 he published a list of 45 of these nebulas, which in later years he expanded to 103.
As it turned out, the list of Messier objects turned out to be far grander and more important than comets, and Messier would be completely forgotten now if his comet discoveries were his only accomplishment. It is his list of things to be disregarded that has made his name immortal, for it includes numerous star clusters and distant galaxies.
Neon, Krypton, and Xenon
1898 A.D.
ENGLAND
Polonium and radium were not the only elements discovered in 1898. In the previous four years, Ramsay had discovered argon and helium. There had to be several more elements in the zero-valence family, and he searched for them with the assistance of a British chemist, Morris William Travers (1872-1961).
A British inventor, William Hampson (1854-1926), had developed a method for producing liquid air in sizable quantities. He gave some to Ramsay and Travers, who carefully distilled it and, in the argon fraction, discovered neon (from the Greek word for "new"), krypton (hidden), and xenon (stranger). The new elements were all gases and all zero-valence. The five elements (including helium and argon) were called, as a group, the inert gases, or more recently, the noble gases.
Neon Lights
1910 A.D.
FRANCE
Beginning in 1910, the French chemist Georges Claude (1870-1960) showed that electric discharges through the noble gases could be made to produce light.
Most spectacular was the red light produced in this manner by neon, so that light produced in this manner by any gas came to be called neon lights.
The fact that tubes filled with neon or other gases could be twisted into any shape -- so that they spelled out words, for instance -- made it inevitable that they would replace ordinary incandescent bulbs in advertising signs.
åThe First Synthetic Rubber
1931 A.D.
U.S.A.
Rubber had become a vital resource in an age of automobiles. Its use in tires was essential, and it had a myriad of other uses as well. The major producer of rubber was originally Brazil, but production had been transferred to Malaya. The possibility of such a distant source being cut off in time of war or political unrest made it advisable, even imperative, that the industrial nations of Europe and America devise some sort of synthetic rubber that could be made at home.
One of those involved in the search was a Belgian-born American chemist, Julius Arthur Nieuwland (1878-1936). His researches uncovered the fact that acetylene, a compound with a molecule made up of two carbon atoms and two hydrogen atoms, could polymerize; that is, add other atoms onto itself to form a long chain of atoms. At some stage, this chain gained some of the properties of rubber.
Nieuwland found that if, at the four-carbon stage, chlorine atoms were attached, the resulting chain was far more like rubber. By 1931 he had what was called neoprene. This kept essential facets of the American economy rolling later when the rubber supply was indeed cut off.
[Neptune's Rings
1981 A.D.
PASADENA, CALIFORNIA
The rings of Uranus had been discovered by the behavior of a star's light, which disappeared and reappeared as Uranus approached it and then left it.
In 1981 similar phenomena were noted when Neptune passed in front of a star. But the pattern had been symmetrical as the star passed into and out of occultation with Uranus, and in the case of Neptune it was not.
The suggestion was therefore made that Neptune did not have symmetrical rings but merely arcs of ring material that did not stretch all the way around the planet. If so, this is another unprecedented situation.
«Neptune
1846 A.D.
UNITED KINGDOM
The planet Uranus, discovered by British astronomer William Herschel (1738-1822) in 1781, was naturally observed frequently and carefully by many astronomers. In 1821 the French astronomer Alexis Bouvard (1767-1843) had shown that Uranus's position in the sky had drifted somewhat from the position to be expected if the gravitational influence of the Sun and various planets were taken into account.
One possibility was that an as-yet-unknown planet existed beyond Uranus whose gravitational influence had not been taken into account.
A British astronomer, John Couch Adams (1819-1892), attempted to calculate where such a distant planet might be in the sky based on the discrepancy in Uranus's position. He made some reasonable assumptions as to its mass and its distance from the Sun, and by October 1843, he had a possible position located. Unfortunately, he could not interest the Astronomer Royal, George Biddell Airy, in his work.
Meanwhile, a French astronomer, Urbain-Jean-Joseph Leverrier (1811-1877), was attempting the same task independently, and he ended with a position very similar to that of Adams. He wrote to a German astronomer, Johann Gottfried Galle (1812-1910), and asked him if he would check that region of the sky.
As it happened, Galle had a new map of that portion of the sky, and when he started looking, on September 23, 1846, he found the planet almost at once, for it was fairly bright (as seen through the telescope). It was not on the map. Because of its greenish color, the new planet was named Neptune after the Roman god of the sea. Although Galle actually saw the planet first, the credit for its discovery is divided between Adams and Leverrier. The whole story is usually regarded as the greatest victory that English scientist Isaac Newton's law of gravitation was to achieve, for a tiny apparent deviation from that law was enough to lead to the discovery of a giant planet.
Later in 1846, the British astronomer William Lassell (1799-1880) discovered a satellite of Neptune, which he named Triton after a son of Neptune (Poseidon) in the Greek myths. It was a large satellite, larger than our Moon, and was the last large satellite to be discovered.
kNeptunium and Plutonium
1940 A.D.
BERKELEY, CALIFORNIA
Fermi had tried to form element number 93 by bombarding uranium with neutrons. Hahn and Meitner had shown that the result was nuclear fission. The two were not mutually exclusive, however. It was possible that some uranium nuclei might undergo fission and others might undergo the kind of changes that would produce element number 93.
In 1940 the American physicists Edwin Mattison McMillan (b. 1907) and Philip Hauge Abelson (b. 1913), studying uranium that had been bombarded with neutrons, detected a beta particle with a half-life of 2.3 days. When they had tracked this down, they announced on June 8, 1940, that they had located traces of element number 93.
Since uranium had been named for the planet Uranus, the new element, lying beyond uranium, was named neptunium, for Neptune, the planet lying beyond Uranus.
Since the neptunium isotope that had been located emitted beta particles, it had to gain another unit in atomic number and produce element number 94, which was named plutonium, for the planet Pluto. In this part of the work, the American physicist Glenn Theodore Seaborg (b. 1912) was prominent.
Neptunium and plutonium were the first of the transuranium elements to be discovered. There would be others.
Seaborg recognized that the transuranium elements were part of a series analogous to the rare earth elements. There were 15 elements running from lanthanum (number 57) to lutetium (number 71) inclusive (with number 61 still undiscovered), and they were now called the lanthanides after the first member. The second group would be the 15 elements running from actinium (number 89) to element number 103 inclusive, and they were named the actinides. Six of the actinides were now known, and nine remained to be discovered.
For their work on transuranium elements, McMillan and Seaborg were awarded the Nobel Prize for chemistry in 1951.
0The Speed of Nerve Impulses
1922 A.D.
U.S.A.
The electric currents in nerves are tiny, so tiny that it was difficult to study them in detail. The American physiologists Joseph Erlanger (1874-1965) and Herbert Spencer Gasser (1888-1963) developed delicate methods of detection using Braun's oscilloscope to aid in the studies.
Beginning in 1922, they determined the rates at which nerve fibers conducted their impulses and showed that the velocity of the impulse varied directly with the thickness of the fiber. For this, the two men shared the Nobel Prize for medicine and physiology in 1944.
,Nerves are Cells
1849 A.D.
GERMANY
The cell theory, which had been advanced by Schleiden and Schwann, grew firmer with the years. The German anatomist Rudolf Albert von Kolliker (1817-1905) had shown that eggs and sperm might be considered cells, and in 1849 he showed that nerve fibers were elongated outgrowths of cells.
╨Nerve Growth Factor
1952 A.D.
ITALY
The Italian embryologist Rita Levi-Montalcini (b. 1909) worked on chick embryos during World War II under difficult conditions, since she was Jewish. After the war she continued her work and found that an implantation of certain tumors in chick embryos hastened nerve growth. By 1952 she could show that the nerve growth factor was a soluble substance released by the tumor. For this work she received the Nobel Prize for physiology and medicine in 1986.
╔Neuron Theory
1889 A.D.
GERMANY
Of all the cells, the nerve cells seem most complex, and of all the organs and systems of organs, the brain and nervous system seem most complex. Moreover, of all the parts of a human body, the brain and nervous system are, or should be, the most interesting, since it is they that make us human. German anatomist Heinrich Wilhelm Gottfried von Waldeyer-Hartz (1836-1921) was the first to maintain that the nervous system was built out of separate cells and their delicate extensions. The delicate extensions, he pointed out, approached each other closely but did not actually meet, much less join, so that the nerve cells remained separate. He called the nerve cells neurons, and his thesis that the nervous system is composed of separate neurons is the neuron theory.
An Italian histologist, Camillo Golgi (1843 or 1844-1926), 15 years before, had devised a system of staining with silver compounds that brought out the structure of neurons in fine detail. Using this stain he could demonstrate that Waldeyer-Hartz's views were correct. He could show that fine processes did indeed issue from the neurons and that those from one neuron approached but did not touch those of neighboring neurons. The tiny gaps between one neuron and the next are called synapses (oddly enough, from a Greek word meaning "union," which they appeared to be at a casual glance but were not in actuality).
A Spanish histologist, Santiago Ramón y Cajal (1852-1934), improved on Golgi's stain, and by 1889 had worked out the cellular structure of the brain and spinal cord in detail, firmly establishing the neuron theory. For their work on the neuron theory, Golgi and Ramón y Cajal shared the Nobel Prize in medicine and physiology in 1906.
ÅThe Beginnings of Neurology
1766 A.D.
SWITZERLAND
From Greek times, nerves had been thought to be hollow tubes that carried some sort of subtle fluid, perhaps in analogy to veins and arteries.
A Swiss physiologist, Albrecht von Haller (1708-1777), dismissed this possibility and decided to reach no decisions on nerves that could not be demonstrated by experiment. His experimental work, which he published in 1766, showed that muscles were irritable; that is, a slight stimulus to the muscle would produce a sharp contraction. He also showed that a stimulus to a nerve would produce a sharp contraction in the muscle to which it was attached. The nerve was the more irritable and required the smaller stimulus.
Haller judged, therefore, that it was nervous stimulation that controlled muscular movement. He also showed that the tissues themselves do not experience a sensation but that the nerves channel and carry the impulses that produce the sensation.
Furthermore, Haller showed that nerves all led to the brain or to the spinal cord, which were thus clearly indicated as the centers of sense perception and responsive action. For all this, he is considered the founder of modern neurology.
¡Neurospora
1941 A.D.
PALO ALTO, CALIFORNIA
Often genetics takes a step forward with the introduction of a simpler organism for study, as was the case, for instance, when Morgan began to study fruit flies.
The American geneticist George Wells Beadle (1903-1989), in collaboration with the American biochemist Edward Lawrie Tatum (1909-1975), began to work in 1941 with a mold called Neurospora crassa.
In the wild state, this mold will grow on a nutrient medium in which sugar is the only significant organic compound. For its supply of elements not present in sugar, such as nitrogen, phosphorus, and sulfur, Neurospora can make do with inorganic compounds.
If Neurospora are bombarded with X rays, using Muller's technique, however, mutations take place. Some of the mutated Neurospora lose the ability to form a particular organic compound necessary for growth, so that it has to be added to the nutrient medium.
Beadle found that it was not always necessary to add the missing compound itself to the medium -- a different but similar compound might do. This meant that the similar compound could be converted into the necessary one. By trying a variety of similar compounds and noting which would promote growth and which would not, Beadle could deduce the sequence of chemical reactions and locate the step that the mutated mold could not manage.
From his work, Beadle concluded that the characteristic function of the gene was to supervise the formation of a particular enzyme (one gene to each enzyme).
A mutation took place when a gene was so altered that it could no longer form a normal enzyme.
For this work, Beadle and Tatum were awarded a share of the Nobel Prize for medicine and physiology in 1958.
£Magellanic Supernova
1987 A.D.
CHILE
The last supernova that had been visible in our own Milky Way Galaxy was one studied by Kepler in 1604. Since then, the nearest supernova had been one spied 2,300,000 light-years away in the Andromeda galaxy, but at the time it was not known to be a supernova and was not carefully studied even with the instruments then available. Since then, the only supernovas to have been noted had been in still more distant galaxies.
In February 1987, however, a supernova was caught in its early explosive stage in the Large Magellanic Cloud. That was not in our own galaxy to be sure, but it was in the galaxy closest to our own, only 150,000 light-years away. The explosion had been heralded by a spray of neutrinos, some of which were caught in recently devised neutrino telescopes. Undoubtedly, as more and better instruments of the sort are built, the sky will be regularly scanned for neutrinos that may herald supernova explosions.
The Magellanic supernova was carefully studied as the light built up and faded and as the nebulosity about it expanded and thinned. In 1988 the expected appearance of a pulsar at its center rotating 2,000 times per second was reported.
┐ The Neutron
1932 A.D.
ENGLAND
For 20 years, it had been assumed that the atomic nucleus was made up of protons and electrons, since these were the only two subatomic particles known.
Thus the nitrogen nucleus had a mass of 14, so it must contain 14 protons.
On the other hand, the nitrogen nucleus had an electric charge of +7, whereas 14 protons would have an electric charge of +14. Therefore, the nucleus must have seven electrons with a charge of -1 each to neutralize the charge of seven of those protons. The net result was that the nitrogen nucleus was thought to be made up of 14 protons and 7 electrons, or 21 particles altogether.
But seven years earlier, when Uhlenbeck and Goudsmit worked out the concept of particle spin, it had become clear that something was wrong with the proton-electron notion of nuclear structure. Protons and electrons both had a spin of either + or -. If 21 such spins, or in fact any odd number of such spins, were added up (regardless of the distribution of pluses and minuses), the total spin should be one of the half-integers: 1/2, or 1-1/2, or 2-1/2, and so on. The actual measured spin of the nitrogen nucleus, however, was an integer. The nucleus, therefore, could not contain an odd number of particles but had to contain an even number. There were other nuclei that shared this anomalous characteristic.
If the proton-electron combination could be counted as a single particle, however, then the nitrogen nucleus would contain seven protons and seven proton- electron combinations, for 14 particles -- an even number.
A proton-electron combination would have the mass of a proton but would carry no electric charge. If such a neutral particle existed, however, it would be difficult to detect, for the various devices for detecting subatomic particles all depended on the electric charge these particles carried.
In 1930 Bothe, who had devised the coincidence counter, became aware of strange radiations emerging from beryllium that had been exposed to bombardment with alpha particles, but he couldn't tell what the radiation consisted of.
In 1932, however, the English physicist James Chadwick (1891-1974) repeated the experiments and maintained that the best way of explaining the observations was to suppose that the alpha particles knocked neutral particles out of the beryllium nucleus. These particles could not be detected directly, since they lacked an electric charge, but they succeeded in knocking protons out of the atomic nuclei in paraffin, and those protons could be detected. A radiation capable of ejecting protons must consist of particles with a mass in the proton range, and a particle possessing the mass of a proton and no charge was just the thing to represent a proton-electron pair and yet be one particle and not two. The new particle was called a neutron, and it proved to be by far the most useful particle for initiating nuclear reactions.
For his discovery of the neutron, Chadwick was awarded the Nobel Prize for physics in 1935.
₧A New Anatomy Book
1543 A.D.
BELGIUM
Just as Copernicus was overturning Greek notions of astronomy, a Flemish anatomist, Andreas Vesalius (1514-1564), was upsetting Greek notions of anatomy. Unlike other anatomists of the period, Vesalius was willing to trust his own eyes when they disagreed with the statements of the Greeks.
He put together the results of his researches in a book entitled De Corporis Humani Fabrica (Concerning the Structure of the Human Body) in which he corrected over 200 errors of Galen. What's more, the book took advantage of the technique of printing to reproduce careful illustrations of anatomical facts, drawn by the Flemish artist Jan Stephan van Calcar (ca. 1499-after 1545), who had been a student of Titian.
Vesalius's book was published in 1543, the same year in which Copernicus's book appeared, and this double appearance strengthens the feeling that the year marks the beginning of the Scientific Revolution.
;Discovering A New Star
1054 A.D.
CHINA
Hipparchus was supposed to have seen a new star some 12 centuries before, but no European had seen one since, though Chinese astronomers had reported a number of new stars in that interval.
On July 4, 1054, a bright new star blazed forth in the constellation of Taurus. For three weeks it shone so brightly it could be seen in daylight. At its peak, it was two or three times as bright as Venus at its brightest and could cast a dim shadow. It remained visible for nearly two years before finally fading away into invisibility.
This new star was recorded by the Chinese astronomers, but in Europe it went unnoted (or at least no reference to it has survived). This is an indication of the low state of astronomy, and of science generally, in Europe, which was just then emerging from a five-century-long Dark Age.
╟The Calculus
1669 A.D.
CAMBRIDGE, ENGLAND
In the years 1665-1666, English scientist Isaac Isaac Newton (1642-1727) was staying at his mother's farm in order to escape the London plague. One evening he saw an apple fall from a tree at a time when the Moon was shining peacefully overhead and began to wonder why the Moon didn't fall. He then thought that perhaps it did, but that it was also moving horizontally and fell at each moment just enough to make up for the curvature of the Earth. Thus, the Moon fell forever but only succeeded in moving around the Earth in one of Kepler's ellipses.
Newton spent considerable time trying to work out how Earth might pull at the Moon as it pulled at the apple, and at what rate the Moon might be falling, but he was not satisfied with his calculations and put them to one side. Some say it was because there was no good determination of the exact size of the Earth at the time; others say it was because he didn't know how to allow for the fact that every bit of Earth was pulling at the Moon from slightly different distances and angles. He needed a mathematical tool that would help him solve that problem.
In 1669 he began working on such a tool, a mathematical technique that came to be called calculus. This was a more versatile technique than anything invented earlier, and science could not do without it these days. Calculus is the beginning of higher mathematics.
Working on the calculus at roughly the same time as Newton was a German mathematician, Gottfried Wilhelm Leibniz (1646-1716). Both he and Newton worked out the technique -- Newton, perhaps, a little sooner -- but Leibniz ended with a better symbolism.
This is not unusual. Frequently two scientists working independently come up with the same answers in response to the same problems. Often the solution is to give them joint credit. Sometimes, however, there are arguments about which scientist was really first, and this may even degenerate into accusations of plagiarism.
That is what happened this time. Exacerbated by national prejudices, English versus German, there was a Homeric battle that poisoned the scientific community for years without ever settling anything. Today, Newton and Leibniz are given joint credit for the calculus.
üThe Vitamin Niacin
1937 A.D.
U.S.A.
Goldberger had shown that pellagra was a vitamin-deficiency disease. A disease of dogs called blacktongue was the canine equivalent of pellagra.
In 1937 the American biochemist Conrad Arnold Elvehjem (1901-1962) considered the problem. Euler-Chelpin had shown that Harden's coenzyme included nicotinamide. The enzyme wouldn't work without the coenzyme, and the coenzyme wouldn't work without the nicotinamide portion. Human beings, dogs, and other animals can manufacture all parts of the coenzyme from simpler substances -- except the nicotinamide. That has to be present in the diet.
Since enzymes are needed in trace quantities only, so are coenzymes, and so, in this case, is nicotinamide. Animals can risk depending on the diet for something needed in so small a quantity. Plants can make nicotinamide out of simpler substances.
But suppose the diet lacks even the trace quantities of nicotinamide that are needed? In that case, the enzyme won't work, carbohydrate metabolism will proceed limpingly or not at all, and serious symptoms will arise.
Nicotinic acid is simpler than nicotinamide and is easily converted to nicotinamide in mammalian tissue. Elvehjem therefore added a very small quantity of nicotinic acid to the diet of a dog with blacktongue, and it improved markedly and very quickly. It was at once apparent that nicotinic acid and nicotinamide were the vitamins that prevented pellagra, or cured it if it occurred.
Because physicians didn't want the lay public to confuse nicotinic acid with nicotine (a poisonous alkaloid) and assume there were vitamins in cigarettes, they used the names niacin and niacinamide for nicotinic acid and nicotinamide.
It turned out that other vitamins also worked because they were essential parts of coenzymes, parts that could not be manufactured in the body, were needed only in trace amounts, and could be picked up ready-made from the diet.
Nickel: A Hard Metal
1751 A.D.
STOCKHOLM, SWEDEN
Although Brandt had isolated cobalt 14 years before, the problem of copper ore that did not yield copper persisted. Some of this sort of ore didn't yield cobalt, either, and the miners called it kupfernickel (Old Nick's copper, with reference to the devil).
In 1751 a Swedish mineralogist, Axel Fredrick Cronstedt (1722-1765), who had studied under Brandt, tackled kupfernickel and isolated from it a white metal that was neither copper nor cobalt. Cronstedt called it nickel, taking the second half of the miners' name.
Cronstedt discovered that nickel, like iron but less strongly, was attracted by a magnet. It was the first time that anything but iron had been found to be attracted by a magnet. As a matter of fact, magnets were eventually found to attract cobalt as well.
Indeed, iron, cobalt, and nickel are very similar metals. This was the first hint that elements might be grouped into families and that some sort of order might be imposed on them -- but that did not take place for another century.
-River Boats
3500 B.C.
EGYPT
It is certainly easier to carry heavy loads over water than over land. Water offers much less friction than land does, and there are no permanent unevennesses in it: no rocks, no ridges, no uphill stretches.
In this connection, the Nile was ideal. Not only was it a source of water for rainless Egypt -- not only did its annual flood periodically fertilize the soil -- but its current was gentle and there were no storms. The Nile did not damage and overturn boats as the unruly Tigris in Sumeria did. (The very name of that river is the Greek word for "tiger.")
What's more, the Nile flows almost due north, while the wind is almost always from the north. Therefore a boat can move smoothly down river and, when the time comes to return, a sail can be hoisted to catch the wind and the ship will be blown upstream.
Egypt is not a forest nation, but it had luxuriant stands of reeds (called papyrus) along the river in those days, and the reeds could be used in bundles to build boats. The boats were built to form hollows, so that they would displace more water and carry more weight without sinking. These reed boats were not particularly sturdy, but the gentle Nile did not require sturdy boats. (When Moses was set afloat in the Nile River, he was placed in a little boat -- or ark -- of bulrushes; that is, papyrus.)
Egypt thus had a most convenient form of communication that perhaps accounted for its slowness to adopt the Sumerian wheeled cart. Egypt had scarcely any need for land transportation.
By 3500 B.C. Egyptian boats had begun to ply the Nile, and by 3000 B.C. they were venturing out of the Nile into the Mediterranean, hugging the shore, and making their way past Sinai and Canaan to Lebanon. There they obtained the tree-trunks they lacked in Egypt and brought them back for construction purposes.
╥The Nile River
1770 A.D.
SUDAN
The coasts of the continents were relatively easy to explore, but the interior represented greater toil and greater risks. This was particularly true of Africa. Its shores had been the first to be explored by the Portuguese explorers, but its interior was the last to be brought into the light of known geography, so that for a long time it was known as the Dark Continent.
Most paradoxical was the matter of the Nile River. On the banks of its northernmost portion, one of the two oldest civilizations of the world flourished, yet neither the Egyptians nor any of the civilized people that followed them had ever discovered the source of the Nile. This becomes less surprising when it is understood that the Nile is the longest river in the world. It flows in a fairly straight line from south to north, and the source is over 4,000 miles from the mouth. The ancient Egyptians had made their way upriver for about 1,500 miles before giving up the search.
In 1770, however, the Scottish explorer James Bruce (1730-1794) made his way upstream to Khartoum in the Sudan. There two rivers join, the White Nile coming up from the southwest and the Blue Nile from the southeast. Bruce followed the Blue Nile and finally found its source in Lake Tana in what is now northwestern Ethiopia.
This seemed at the time to solve the problem of the source of the Nile, but the White Nile, being the longer of the two, is the main river, and its source remained unknown for another century.
ENiobium
1801 A.D.
ENGLAND
An English chemist, Charles Hatchett (1765-1847), analyzed an unusual mineral in the British Museum, one that had been sent there from Connecticut in pre-Revolutionary days. In 1801 he reported a new element in the mineral, an element he named columbium in honor of the United States, which was sometimes known by the sobriquet of Columbia. There was, however, a dispute over whether the substance was really a new element or not. By the time it was finally decided that it was, its name had become niobium and that is now official, so the United States lost the honor.
~Nitrogen
1772 A.D.
ENGLAND
At this time it was known that ordinary air supported combustion and animal life and that carbon dioxide did not. If candles were burned in an enclosed volume of air until no further burning was possible, had all the air become carbon dioxide?
Black asked a student of his, the British chemist Daniel Rutherford (1749-1819), to investigate the matter. In 1772 Rutherford, having burned a candle to extinction in a closed container, absorbed all the carbon dioxide that had been produced by combining it with certain chemicals. He found that there was still a great deal of gas left that was not carbon dioxide, which also supported neither combustion nor animal life. He had, in this way, discovered a new gas that eventually came to be called nitrogen. This is from the Greek, meaning "niter producer," since niter, a mineral properly called potassium nitrate, contains nitrogen.
îNorth Magnetic Pole
1831 A.D.
NORTH POLE
Since the time of Gilbert, it had been understood that the Earth must have a North Magnetic Pole and a South Magnetic Pole. The general (and rather natural) feeling was that the magnetic poles would be near, or perhaps exactly at, the rotational poles. However, the Arctic and Antarctic regions of Earth, cold and desolate as they were, could only be explored with great difficulty.
It was not until June 1, 1831, that the North Magnetic Pole was actually reached. The feat was accomplished by a Scottish explorer, James Clark Ross (1800-1862). He found his compass pointing straight down, on the western shore of Boothia Peninsula, at 70.85 degrees North Latitude and 96.77 degrees West Longitude. The pole was discovered only because it was 2,100 miles from the geographic North Pole and therefore relatively accessible. In fact, it was only a few hundred miles north of the Arctic Circle.
ñNew Nebular Hypothesis
1944 A.D.
SWEDEN
For nearly two centuries, astronomers had been trying to work out some reasonable mechanism that would account for the formation of the Solar System.
Laplace's nebular hypothesis had broken down over the fact that 98 percent of the angular momentum of the Solar System was concentrated in the planets, which made up only 0.1 percent of the total mass of the system.
Chamberlin had advanced the planetesimal theory, which required a near collision that would draw out solar matter by gravitational pull and form the planets. Eddington, however, showed the interior of stars to be so incredibly hot that matter pulled out of the Sun would simply disperse and not collect into planets.
In 1944 Weizsacker worked out a new version of the nebular hypothesis. He introduced the notion of turbulence in the outer layers of the condensing nebula and showed how, as a result of such turbulence, planets would form in their actual observed orbits, more or less.
Furthermore, the development of magnetohydrodynamics at just about this time, by the Swedish astronomer Hannes Olof Gösta Alfvén (b. 1908), showed how thin gases moved when immersed in magnetic fields and how they could carry energy and angular momentum outward. This solved the problem of the concentration of angular momentum in the planets.
The Weizsacker mechanism, with minor modifications, is now viewed as a likely explanation of the formation of the Solar System.
:Nobelium
1958 A.D.
SWEDEN
The effort to form elements with higher and higher atomic numbers set a new record in 1958 with the formation of a few atoms with the atomic number of 102. There was some delay while the identity of the new atoms was confirmed, and when they were, the element was given the name of nobelium after Nobel.
IChemical Nomenclature
1787 A.D.
FRANCE
Language often stands in the way of scientific advance. This was especially true in chemistry, since chemists had inherited from the alchemists a bewildering array of names for various substances. The alchemists had deliberately attempted to increase their reputations by speaking metaphorically and mystically, and since no two used the same metaphors, chemists could scarcely understand each other when they reported their work.
Through the 1700s, attempts had been made to systematize the use of chemical terms and names for substances. Finally in 1787 Antoine Lavoisier and several coworkers published The Method of Chemical Nomenclature, in which a sensible and logical system was proposed. This was accepted by chemists over the next couple of decades, and finally chemistry had one language, which it retains to this day.
Another Geometry
1854 A.D.
GERMANY
The non-Euclidean geometry worked out by Lobachevsky and Bolyai presupposed the possibility of more than one line through a point (even an infinite number of lines), all parallel to a given line that did not include the point. As in Euclidean geometry, lines of infinite length were possible.
In 1854 a German mathematician, Georg Friedrich Bernhard Riemann (1826-1866), developed another kind of non-Euclidean geometry, one in which it was impossible for any two lines to be parallel, and all lines intersected. What's more, in this geometry all lines were finite in length. In Euclidean geometry, the three angles of a triangle add up to 180 degrees; in Lobachevskian geometry, they add up to less than 180 degrees; and in Riemannian geometry, they add up to more than 180 degrees.
Riemann's geometry is perfectly reasonable and self-consistent. Indeed, it resembles the geometry on the surface of a sphere, where all great circles (those that divide the surface into equal halves) are finite in length and intersect.
Riemann generalized geometry to the point where he considered it in any number of dimensions. He also considered situations in which measurements changed from point to point in space but in such a way that one could transform one set of measurements into another according to a fixed rule.
At the time, this sounded like pure abstraction, but half a century later, Riemannian geometry was shown to represent a truer picture of the Universe than did Euclid's geometry, thanks to the theory of general relativity.
+ Non-Euclidean Geometry
1826 A.D.
RUSSIA
Euclid had based his massive structure of geometry, over two thousand years before, on ten axioms and propositions that could be considered so self-evident that they required no proof. (One had to start some-where.)
One of these axioms can be stated in a number of ways, of which the simplest is "Through a given point, not on a given line, one and only one line can be drawn parallel to the given line." This did not seem quite as self-evident as Euclid's other axioms, and the notion of parallelism implied the existence of lines of infinite length -- not an easy thing to accept.
Since Euclid's time, mathematicians had desperately tried to prove that axiom from the other axioms. All failed to do so.
Nearly a century before, the Italian mathematician Girolamo Saccheri (1667-1733) had been struck with the idea of beginning by supposing that the axiom was not true. He could then proceed to build a geometry on that basis and, sooner or later, arrive at a contradiction. He could then conclude that the axiom was true. That having been proved, it would no longer be viewed as an axiom.
However, he could find no contradiction, and this made him so uncomfortable that he imagined he had found a contradiction and, in 1733, published a book entitled Euclid Cleared of Every Flaw, in which he claimed he had proved the axiom -- but hadn't.
Finally, in 1826, a Russian mathematician, Nikolay Ivanovich Lobachevsky (1792-1856), got onto the same track, but he went farther. The axiom, he decided, was not an axiom because it was not needed; geometry could be made self- consistent without it. He showed that if one began with an axiom that stated "Through a given point, not on a given line, any number of lines can be drawn parallel to a given line," then that and the remaining axioms of Euclid could be used to draw up a new "non-Euclidean" geometry. It would be different from the ordinary kind, but it would be self-consistent.
Lobachevsky published his ideas in 1829 and was first in the field. A Hungarian mathematician, János Bolyai (1802-1860), had as early as 1823 worked out the same non-Euclidean geometry. However, his publication was delayed till 1832, so Lobachevsky got the credit.
Gauss had actually worked out the idea of non-Euclidean geometry as early as 1816 but had lacked the courage to publish it.
5Noradrenaline
1946 A.D.
SWEDEN
It was already known that acetylcholine was a chemical that served to transmit a nerve impulse from one neuron to a neighboring neuron.
In 1946 the Swedish physiologist Ulf Svante von Euler (1905-1983) showed that in that part of the nervous system called the sympathetic nerves, the transmitting chemical was noradrenaline (more properly, norepinephrine), which was very much like the hormone adrenaline in structure but was missing a carbon atom.
Von Euler received a share of the Nobel Prize for medicine and physiology in 1979 for this discovery.
PComparative Embryology
1828 A.D.
GERMANY
Beginning in 1828, Baer published a two-volume textbook on embryology. In it he pointed out that, in early stages of their development, vertebrate embryos were quite similar, even among creatures that in the end were very dissimilar.
Small structures in different embryos, scarcely distinguishable from each other at first, might develop into a wing in one case, an arm in another, a paw in a third, a fin in a fourth, and a flipper in a fifth. Baer believed that relationships among animals could be deduced more properly by comparing embryos than by comparing adult structures, so that he is considered the founder of comparative embryology.
In particular, Baer pointed out that early vertebrate embryos possessed a notochord for a short period of time. The notochord is a stiff rod running the length of the back. Some very primitive fishlike creatures possess such a structure throughout life, but in vertebrates, it is quickly replaced by a spinal cord. Nevertheless, the temporary existence of the notochord in vertebrate embryos shows their relationship to the primitive creatures.
Composition of a Nova
1866 A.D.
ENGLAND
Since the exceedingly bright novas spied by Tycho Brahe and by Kepler nearly three centuries before, further novas of the sort had been seen. Nevertheless, dim novas had been sighted, and they still attracted notice because they had brightened suddenly and without warning.
In 1866 Huggins managed to study the spectrum of a nova and showed from its spectral lines that it was surrounded by a cloud of hydrogen.
This was the first indication that hydrogen might be a dominating constituent of the Universe.
¡Novas in Andromeda
1920 A.D.
U.S.A.
The Andromeda nebula was a matter of dispute among astronomers in the early decades of the twentieth century. There were some who thought it was a cloud of dust and gas that was part of our own Galaxy (and that the same was true of other nebulas that resembled it). Others pointed out that the spectrum of the Andromeda and other such nebulas was that of starlight and not at all like that of the Orion nebula, which was clearly a cloud of dust and gas. The Andromeda nebula and others like it might therefore be vast assemblages of stars that were independent galaxies but so far away from us that there was little hope of seeing their stars individually.
The leading exponent of a nearby Andromeda nebula was Shapley, who had worked out the shape and size of the Galaxy and determined the position of the Solar System within it. The leading exponent of a far-off Andromeda nebula was the American astronomer Heber Doust Curtis (1872-1942).
Curtis reasoned that, although the Andromeda nebula might be too far away for ordinary stars in it to be made out, unusually bright stars such as novas ought to be visible. He therefore observed the nebula carefully and did see numerous very faint stars that appeared and disappeared as though they were exceedingly faint novas. There were far more novas in the patch of light represented by the Andromeda nebula than there were in any other similarly sized patch of the sky. To Curtis, this meant that the Andromeda nebula contained a vast number of extremely faint stars and that it was an independent Galaxy (as Kant had suggested -- see 1755).
In 1920 Curtis and Shapley met in a great debate before the National Academy of Sciences and discussed the matter of Andromeda. Majority opinion among astronomers was on the side of Shapley, but Curtis made an unexpectedly strong showing and won a moral victory. However, the matter could not be decided by debate. It had to await the necessary observations.
ILinotype Machines
1884 A.D.
NEW YORK, NEW YORK
Ever since the invention of printing in 1454, advances had been made in the speed with which it could be carried through. The greater the speed, the more printed matter would be produced, the more would be read, and the more would be desired, especially as literacy increased the world over.
One bottleneck, however, was the setting of type. Plucking out an individual letter and setting it in line was time-consuming.
In 1884 a German-born American inventor, Ottmar Mergenthaler (1854-1899), patented a machine that, when directed by an operator at a keyboard, could set a whole line of type at one time. It was therefore called a Linotype machine. For the next three-quarters of a century it was a mainstay of publishing -- especially newspapers, which increasingly had to be turned out steadily and in quantity.
⌠Nuclear Winter
1983 A.D.
WORLD
The speculative accounts of a comet strike on Earth 65 million years ago, which may have put an end to the dinosaurs, partly because a vast cloud of dust raised into the upper atmosphere by the strike had cut off sunlight, inspired thoughts concerning nuclear war.
A group of people, of whom Carl Sagan (b. 1935) was most prominent, suggested that in the case of an all-out nuclear war, the explosion of thousands of nuclear bombs would raise enough dust to cut off sunlight for a considerable period and produce a nuclear winter. Mass starvation would then follow for the whole planet, not only for the loser of the nuclear exchange but for the "winner" as well, and for all the neutrals.
The predicted intensity of such a nuclear winter seems to have moderated a bit since the first pessimistic projections, but the side effects of a nuclear exchange in the form of fires, fallout, and disruption of the world's economy would surely be dreadful enough even if there were no nuclear winter at all.
▐Nuclear Chain Reactions
1939 A.D.
ENGLAND
Chain reactions are familiar in chemistry. A reaction may produce heat, which encourages further reaction, which produces more heat, and so on. The manner in which a lightning stroke, or a single match, can burn down an entire forest is an example of a chemical chain reaction. A chemical reaction can also produce a molecular product, which brings about more of the chemical reaction, which produces more of the molecular product, and so on. The formation of polymers is sometimes the result of such a chain reaction.
As early as 1932, it had occurred to the Hungarian-born physicist Leo Szilard (1898-1964) that a nuclear chain reaction was also possible. By that time, atomic nuclei were being bombarded by neutrons, and in some cases, the entry of one neutron into a nucleus meant the ejection of two neutrons.
Szilard envisaged the case of a neutron disrupting a nucleus and producing two neutrons, which would disrupt two nuclei, producing four neutrons, which would disrupt four nuclei, and so on. Each disruption would deliver a tiny quantity of energy, but each link in such a nuclear chain reaction would proceed so quickly that the energy produced would mount in a fraction of a second to titanic proportions. The result would be a nuclear bomb, tremendously more powerful than ordinary bombs based on chemical chain reactions.
Szilard was one of many scientists fleeing Central Europe because of German anti-Semitism, and the brains that Germany thus rejected and the allies absorbed were eventually to prove of inestimable help to the allies. Szilard patented the notion of a nuclear chain reaction and offered it to Great Britain.
The nuclear reactions known in 1932 and for several years afterward were not suitable for nuclear chain reactions, however. It took a fast, energetic neutron to eject two neutrons, but those two ejected neutrons were too slow, too lacking in energy, to continue the chain.
In 1939, however, when Szilard heard of nuclear fission, which was brought about by slow neutrons, he realized that a nuclear chain reaction and a nuclear bomb were finally possible, and he promptly began a campaign to persuade American scientists to keep their researches into such things secret. To a large extent, he succeeded.
╨Nuclear Reactions
1919 A.D.
ENGLAND
Rutherford, in his work with alpha-particle bombardments of matter, had made gases his target. For instance, when he bombarded hydrogen, he got bright scintillations on a zinc sulfide screen (which gave off a flash of light whenever struck by an energetic subatomic particle). The alpha particles themselves produced scintillations, but the new scintillations, which appeared when hydrogen was present, were particularly bright.
Rutherford decided (correctly) that the alpha particles occasionally struck a hydrogen nucleus (consisting of a single proton) and hurled it forward. It was these speeding protons, he felt, that produced the bright scintillations.
In 1919, when nitrogen was introduced into the cylinder, occasional bright scintillations like those of protons were produced. Rutherford knew that the nitrogen nucleus had a charge of +7, so that it had to contain at least seven protons. He felt that the alpha particle must knock one of these protons out of the nitrogen nucleus every once in a while.
The number of alpha-particle scintillations produced under these circumstances gradually decreased. Rutherford reasoned that some of the particles must be absorbed by the nitrogen nuclei. If a nitrogen nucleus absorbed an alpha particle with its charge of +2 and lost a proton with its charge of +1, the net change would leave the nitrogen nucleus with a total charge of +8. This is the characteristic charge of an oxygen nucleus.
In short, what Rutherford had done was to combine a helium nucleus (an alpha particle) and a nitrogen nucleus to form a hydrogen nucleus (a proton) and an oxygen nucleus. He had converted one type of atom into another by subatomic bombardment.
Ordinary chemical reactions involve the transfer or sharing of electrons, as Lewis had pointed out ***916). Now Rutherford had produced reactions that involved the transfer of particles inside the nucleus. In other words, he had brought about the first humanly engineered nuclear reaction.
⌐Nucleus of the Atom
1911 A.D.
ENGLAND
For some years, Rutherford had been firing alpha particles at sheets of matter, thinking that even if they could penetrate the matter, they might be deflected and scattered by the atoms making it up. From the manner of the deflection, Rutherford hoped to gain some knowledge of atomic structure.
In 1908, for instance, he fired alpha particles at a sheet of gold only 1/50,000 of an inch thick. Most of the alpha particles passed through, unaffected and undeflected, recording themselves on the photographic plate behind.
Since the gold represented a barrier that was two thousand atoms thick, the fact that alpha particles could pass through them all as though there were nothing there seemed to mean that atoms were mostly empty space.
Yet some alpha particles were deflected, and struck the photographic plate some distance away from the central spot formed by the main stream of alpha particles. Some were deflected through quite an angle.
This meant that part of the atom contained considerable mass. From the fact that so few alpha particles were deflected, it could be concluded that the part with the mass must make up a very small fraction of the atom.
By 1911 Rutherford had gathered enough evidence to put forward his theory of the nuclear atom. The atom, it would seem, has virtually all its mass squeezed into a tiny, positively charged atomic nucleus (which we now know is only 1/100,000 the diameter of the atom). The outer regions of the atom contain enough electrons, each with a unit negative charge, to neutralize the nuclear charge and leave the atom as a whole electrically neutral.
This theory was adopted quickly, for it answered major questions. For example, the relationship between alpha particles and helium was now understood. The alpha particles were helium nuclei, not helium atoms.
This accounted for the electric charge of the alpha particle and, thanks to its subatomic size, for its penetrating power.
▒Nuclear Structure
1948 A.D.
U.S.A.
The chemical properties of atoms depend on the arrangement of their electrons into shells. This is what makes the periodic table of the elements work.
The nuclear properties of atoms must depend on the arrangement of the protons and neutrons in the nuclei. They, too, might be arranged in shells, but if so, this would be more difficult to determine than in the case of the outer electrons.
The German-born American physicist Maria Goeppert-Mayer (1906-1972) tried to work out the nature of the nuclear shells from the nuclear properties that had been observed for different atoms. She showed that nuclei that contained 2, 8, 20, 50, 82, or 126 protons or neutrons would be more stable than their neighbors in the periodic table. These were called shell numbers, or more dramatically but less scientifically, magic numbers. If 28 or 40 protons or neutrons were present, some stability resulted, and these were called semimagic numbers.
Goeppert-Mayer advanced her notions in 1948, at about the same time a German physicist, Johannes Hans Daniel Jensen (1907-1973), advanced the same views. As a result, Goeppert-Mayer and Jensen received shares of the Nobel Prize for physics in 1963.
Nucleic Acids
1869 A.D.
SWITZERLAND
The classification of foodstuffs into carbohydrates, fats, and proteins still seemed quite satisfactory.
In 1869, however, a Swiss biochemist, Johann Friedrich Miescher (1844-1895), isolated a substance from the remnants of cells in pus that did not belong to any of these three classes. It contained both nitrogen and phosphorus.
Miescher took his new discovery to Hoppe-Seyler, who investigated the matter himself. When he discovered a similar substance in yeast, the discovery was announced. Since the material seemed to originate in cell nuclei, it was called nuclein at first, and later, because it had acidic properties, nucleic acid.
It was not till three-quarters of a century later that the true and overwhelming importance of nucleic acid was appreciated.
₧The Balance of DNA Bases
1948 A.D.
U.S.A.
It was now known that nucleic acids were large and very complex molecules, especially since Avery had shown that deoxyribonucleic acid (DNA) and not protein was the carrier of physical characteristics. It was DNA, in short, that made up the genes of the chromosomes.
The question was: Just what was it about the structure of nucleic acids that made it possible for them to carry the vast amount of information that genes must carry in order to make human eggs develop into human beings and grasshopper eggs into grasshoppers, without the reverse ever happening? Part of the structure of DNA was known to be four different bases.
Two of them (adenine and guanine) were purines with a two-ring molecule, and two of them (cytosine and thymine) were pyrimidines with a one-ring molecule.
The Austrian-born American biochemist Erwin Chargaff (b. 1905) broke down nucleic acid molecules to their constituent bases and separated them by paper chromatography. He determined the quantity of each present and by 1948 was able to demonstrate that, in nucleic acids generally, the number of guanine units was equal to the number of cytosine units, and the number of adenine units was equal to the number of thymine units. This meant that the number of purine units was equal to the number of pyrimidine units.
This was a more important discovery than Chargaff apparently realized at the time, and he did not follow it up properly.
+Nuclear Magnetic Resonance
1946 A.D.
U.S.A.
It is possible for chemical substances to absorb certain frequencies of microwave radiation when those substances are in a strong, steady, and homogeneous magnetic field. The frequencies that are absorbed depend on the magnetic properties of the atoms involved.
In particular, atomic nuclei act as tiny spinning magnets, and these can be lined up in a magnetic field, to strengthen the microwave absorption. The Swiss- born American physicist Felix Bloch (1905-1983) and the American physicist Edward Mills Purcell (b. 1912) independently developed this technique in 1946, and for it they shared the Nobel Prize for physics in 1952.
The technique, named nuclear magnetic resonance (NMR), provided a noninvasive way of studying the interior of living organisms. Since microwaves are far less energetic than X-rays, they are correspondingly less likely to do damage to tissues. Then too, X-rays are best at detecting massive atoms, of which there are few in the body, while NMR detects light atoms, particularly hydrogen, and these are plentiful in the body.
The use of NMR is growing more common, but because of public fears of the word nuclear (thinking that it implies the existence of destructive radiation -- definitely not so in this case), physicians commonly speak of it simply as magnetic resonance.
█Nuclear Reactor
1942 A.D.
CHICAGO, ILLINOIS
The idea advanced in 1942 by Hungarian-born physicist Leo Szilard (1898-1964) for a nuclear chain reaction could not be made practical. Once the Manhattan Project had been put in motion, Italian-born American physicist, Enrico Fermi (1901-1954) was placed in charge of producing such a chain reaction. Uranium and uranium oxide were piled up in combination with graphite blocks in a structure called an atomic pile. Neutrons colliding with the carbon atoms in graphite did not affect the carbon nuclei but bounced off, giving up their energy and moving more slowly as a result, thus increasing their chance of reacting with uranium- 235.
Making the pile as large as possible made it more likely that neutrons would strike uranium-235 before blundering out of the pile altogether and into the open air. The necessary size was the critical mass. Naturally, the more enriched in uranium-235 the pile was, the smaller the critical mass needed to be.
Cadmium rods were inserted into the pile, because cadmium would soak up neutrons and keep the pile from becoming active prematurely. When the pile was large enough, the cadmium rods were slowly withdrawn and the number of neutrons produced slowly increased. At some point, the increase would reach the level where more were being produced than were being harmlessly consumed by the cadmium. At that time the nuclear chain reaction would begin and the whole thing would go out of control in a moment.
What stopped that from happening was that some neutrons didn't come out of the bombarded nuclei at once. In other words, after the pile went critical, there was a slight pause before the delayed neutrons were emitted and everything went awry. During that pause, the cadmium rods could be shoved in again.
At 3:45 P.M. on December 2, 1942, in the squash court of the University of Chicago, the chain reaction became self-sustaining and was choked off. The atomic age had begun. The atomic pile was the first nuclear reactor.
ΦNuclear Fission Bomb
1945 A.D.
ALAMOGORDO, NEW MEXICO
For a nuclear chain reaction to take place, it is necessary to accumulate enough fissile material (uranium-235 or an appropriate plutonium isotope manufactured from uranium-238) to bring about an explosion. The amount of fissile material has to be large enough (the critical mass) for enough of the neutrons produced to strike other nuclei before wandering out into open air.
If two pieces of fissile material, each below the critical mass and therefore nonexploding, are fired into each other to form a single piece above the critical mass, any stray neutron (and there are always some around) will start the chain reaction and the material will explode in a fraction of a second.
By mid-1945 enough fissile material had been collected to carry through a test. On July 16, 1945, at a site 60 miles northwest of the town of Alamogordo, New Mexico, a nuclear fission bomb (popularly called an atomic bomb, or an A-bomb) made of plutonium was detonated before dawn. The scientists in charge had expected an explosive force equivalent to 5,000 tons of TNT. What they got was the equivalent of 20,000 tons of TNT.
At a stroke, the face of war had changed totally. It was even possible that the fate of humanity had been sealed.
█The Northwest Passage
1576 A.D.
BAFFIN ISLAND
The English, having failed at the Northeast Passage, tried their hand at the Northwest Passage around the northern shores of North America.
In 1576 an English navigator, Martin Frobisher (ca. 1535-1594), sailed to North America with three ships and 35 men.
He sailed northward from the Labrador area and discovered what we now call Baffin Island, a large island west of Greenland.
In a second voyage, in 1578, Frobisher sighted Greenland itself.
By the time Frobisher arrived, the Viking settlers had died or departed and its shores were occupied only by Inuit (Eskimos). From this time on, Greenland remained part of world geography.
Frobisher did not discover any practical Northwest Passage, however.
δOhm's Law
1827 A.D.
GERMANY
After Fourier had worked out the mathematical system that described the flow of heat adequately, it seemed that the same system might be used to describe the flow of electricity. Whereas heat flow from point to point depended on the temperatures of the two points and the heat conductivity of the material between, so electric flow from point to point might depend on the electrical potential of the two points and on the electrical conductivity of the material between.
By working with wires of different thicknesses and lengths, the German physicist Georg Simon Ohm (1789-1854) found that the quantity of current transmitted was inversely proportional to the length of the wire and directly proportional to its cross-sectional area. He was in this way able to define the resistance of the wire and, in 1827, showed that, "The flow of current through a conductor is directly proportional to the potential difference and inversely proportional to the resistance." This is called Ohm's law.
τOil Wells
1859 A.D.
TITUSVILLE, PENNSYLVANIA
Petroleum (from Latin words meaning "rock oil"), sometimes called simply oil, is a complex mixture of hydrocarbons, formed, it is believed, from the fat content of myriads of microorganisms in the distant past.
In the Middle East, where petroleum is particularly common, some was found even on the surface. There the smaller molecules evaporated, leaving behind a tarry substance variously called pitch, bitumen, and asphalt.
This was used in waterproofing. From pitch one could also sometimes extract a flammable liquid called naphtha (from a Persian word meaning "liquid"), which could be used in lamps. There was a limit to what could be obtained on the surface, however. It was also possible to dig for it. Two thousand years before, the Chinese had dug for brine and occasionally obtained oil.
An American railway conductor, Edwin Laurentine Drake (1819-1880), had invested in a firm that gathered oil for medicinal purposes, from seepages near Titusville, Pennsylvania. It occurred to Drake, who knew about the brine- drilling, that oil could be drilled for as brine was.
He studied drilling methods and, in 1859, set about using those methods at Titusville. He drilled 69 feet into the ground and, on August 28, struck oil. He had drilled the first oil well, which was soon producing 400 gallons per day. Other drillings followed, and other oil wells. The first consequence of this was that kerosene could be obtained in great quantities from petroleum, and the kerosene lamp became almost universal in the United States and elsewhere. Kerosene served to replace whale oil and to cut down somewhat on the carnage that humanity was visiting on those inoffensive animals.
Much more than that, however, lay in the future.
The Beginning of Optics
1025 A.D.
EGYPT
The Arabic physicist known to later Europeans as Alhazen (965-1039) was the first to maintain that vision was made possible by rays of light falling on the eye and was not the result of the eyes giving out rays of light, as physicists had thought till then.
Alhazen also worked with lenses and attributed their magnifying effect to the curvature of their surfaces and not to any inherent property of the substances making them up. His work represented the beginning of the scientific study of optics.
QOral Contraceptives
1954 A.D.
U.S.A.
In a world that was overpopulated and growing more so, it seemed useful to find methods of reducing the birthrate. The most straightforward way of doing so was abstention from sex, but that wasn't really a practical solution. The trick would be to find a cheap and convenient way to lower the birthrate without interfering with sex.
It had been noted that there were natural ways of bringing this about, for during pregnancy and some parts of the menstrual cycle, women can safely indulge in sex without much chance, if any, of conception. It might be possible, then, to find some sort of hormone that, taken by mouth in pill form, as an oral contraceptive, would induce temporary sterility. The American biologist Gregory Goodwin Pincus (1903-1967) found such a hormone, and clinical tests in 1954 demonstrated its efficacy. Use of the Pill (as it was popularly termed) made possible sex without fear of pregnancy. This went a long way toward abolishing the double standard and encouraged the women's liberation movement, with its demand that women be treated on a par with men economically.
:Organic Synthesis
1860 A.D.
FRANCE
When Wöhler had synthesized urea, it might very well have been considered an anomaly, but the techniques of organic chemistry were advancing, and other organic molecules were being synthesized from the elements.
In particular, Pierre-Eugène-Marcelin Berthelot (1827-1907), a French chemist, went about such syntheses and, by 1860, had synthesized such well-known and important organic molecules as methyl alcohol, ethyl alcohol, methane, benzene, and acetylene. He even synthesized molecules that fulfilled all the requirements of organic molecules in terms of structure and properties but that did not occur in living tissue, which put an end once and for all to the idea that only living tissue could manufacture organic molecules.
Indeed, in 1861, when Kekule published a textbook of organic chemistry, he defined it as the chemistry of carbon compounds, with no mention of life. After that, when a term was needed for the chemistry of compounds that occur in living tissue specifically, the term chosen was biochemistry (with bio- from the Greek word for "life").
┐Embryonic Development
1918 A.D.
GERMANY
The German zoologist Hans Spemann (1869-1941) was interested in the development of embryos. Thirty years later, it had been shown that if the fertilized ovum of a test animal was divided in two, and if one of the resulting cells was killed with a hot needle, then the remaining cell would evolve into a longitudinal half of an embryo. The act of dividing in two had established the plane of bilateral symmetry.
If, however, a fertilized ovum divided in two and the two resulting cells were separated and each allowed to develop, each would form a complete (though smaller than normal) embryo. (It is this which results in the birth of identical twins among human beings, for instance.)
To Spemann, the difference between a cell that developed from a divided fertilized ovum and one that developed while attached to a dead partner indicated that the individual cells of an embryo affected each other.
In a series of experiments, Spemann showed that even after an embryo had begun to show definite signs of differentiation, it could still be divided in half, with each half producing a whole embryo. This showed that cells remained plastic until quite late in the game.
Spemann found that an embryo develops according to the nature of neighboring areas. An eyeball develops originally out of brain material and is joined by a lens that develops out of nearby skin. If the eyeball is placed near a distant section of the skin, one that would never in the course of nature develop a lens, it nevertheless begins to develop one.
There were apparently organizers in the embryo that brought about certain developments nearby. For his work, Spemann was awarded the Nobel Prize for medicine and physiology in 1935.
~Organic Radicals
1815 A.D.
FRANCE
Joseph Louise Gay-Lussac (1778-1850) worked carefully with the poisonous gas hydrogen cyanide. In 1815 he discovered a related poisonous gas, cyanogen.
He went on to show that the carbon-nitrogen combination, or the cyano group, was very stable. In chemical changes, the two bound atoms tended to be transferred as a unit. Relatively tightly bound units that maintained their integrity through various chemical changes came to be called organic radicals.
This represented a major step forward in the understanding of organic chemistry; that is, the study of those chemicals and chemical changes characteristic of organisms.
ûThe Origin of Life
1922 A.D.
RUSSIA
Darwin, who had advanced his theory of evolution six decades earlier, had not taken up the matter of the origin of life. Not enough was known, and the subject was too touchy.
Spontaneous generation (life derived from nonlife) had been disproven by Pasteur, but only under present conditions. In earlier times, when life first made its appearance, the Earth's environment was radically different from what it is today (there was no oxygen in the atmosphere, for instance), and no life existed that might promptly consume the material that represented the first tentative approaches to life.
Even so, there was some reluctance to consider the matter of a naturalistic origin to life, one that did not require the intervention of a Creator. The first person to make a significant study of the matter was a Russian biochemist, Alexander Ivanovich Oparin (1894-1980), who, living under a government that was officially atheist, had no inhibitions in doing so.
He began his investigation of the subject in 1922, suggesting that life developed through the slow buildup of organic substances from the simple compounds present in the primordial ocean and atmosphere.
)
Primordial Soup
1952 A.D.
U.S.A.
Evidence of living things, in the form of traces of tiny bacterial cells, has been found in rocks that are 3.5 billion years old. Since the Earth is 4.6 billion years old, this means that in the first billion years of Earth's existence, living things must have evolved from nonliving chemicals. Presumably, they must have evolved from the molecules that made up the huge nebula of dust and gas out of which the Solar System was formed.
It is reasonably well established that the Universe is 99 percent hydrogen and helium in a 9-to-1 ratio, with oxygen, carbon, nitrogen, neon, sulfur, silicon, iron, and argon most important among the final 1 percent. Of these, helium, neon, and argon form no compounds. In the presence of a preponderance of hydrogen, the oxygen, carbon, nitrogen, and sulfur form water, methane, ammonia, and hydrogen sulfide respectively. Silicon combines with oxygen and various metals to form silicates, which are rocky substances, while iron mixes with other less common metals.
Earth therefore began with a core of nickel-iron, surrounded by a rocky mantle and crust. All of that was topped by an ocean of water and an atmosphere that may have consisted of ammonia, methane, and hydrogen sulfide (with some of each dissolved in the water). The simple compounds in the atmosphere and ocean would have been subjected to the energy of the Sun's radiation and, through the addition of such energy, might have built up very gradually into more complicated substances until objects complex enough to be considered alive were the result.
In 1952 the American chemist Stanley Lloyd Miller (b. 1930), working under Harold Urey, attempted for the first time to check this possibility by experimentation.
Miller began with carefully purified and sterilized water and added an "atmosphere" of hydrogen, ammonia, and methane. He circulated this through his apparatus and past an electric discharge that would add energy. He kept this up for a week. He then analyzed the solution and found organic compounds and even a few of the simpler amino acids formed abiogenetically, that is, without the presence of life.
Others later continued the work, using other sources of energy and other mixtures of simple compounds. They also added to the mix more complex compounds that had been formed in other experiments of the sort. None of this served to ascertain the exact route by which life was formed, but it all helped make it seem likely that life did start by some route that involved the action of chemical and physical laws, so that no supernatural cause need be sought.
BOrigin of the Universe
1973 A.D.
U.S.A.
Scientists had come to accept the big bang as the manner in which the Universe had come into being, but that left one crucial question unanswered. Granted that all the matter in the Universe was originally compressed into a comparatively tiny body that expanded into the present Universe, where did that originally tiny body come from?
In 1973 the American physicist Edward P. Tryon pointed out that what we ordinarily think of as a vacuum is not truly a vacuum. It can give rise to subatomic particles that disappear before they can be detected, in accordance with quantum mechanics and the uncertainty principle.
He suggested that if we start with an infinite sea of nothingness, particles will appear and disappear. Every once in a while, a particle may appear that can devlop the mass of the Universe and begin to expand before it can disappear. The Universe may therefore be a random quantum fluctuation in a vacuum, so that it originated out of nothing.
The implications and the detailed development of such a universe have been argued over by astronomers ever since.
|The Orion Nebula
1864 A.D.
LONDON, ENGLAND
Some patches of nebulosity, including the Milky Way itself, had turned out to be clusters of faint stars. A number of Messier objects -- nebulas named after French astronomer Charles Messier (1730-1817) -- had turned out to be globular clusters of stars. Was any nebulosity what it appeared to be -- simply a cloud of gas?
In 1864 English astronomer William Huggins, studying the Orion nebula, found that its spectrum was typical of what would be expected of a luminous gas. It is, indeed, a large cloud of gas (though we know today that stars are embedded in it and that they are what heat the gas to luminosity.)
┘Ancestor of Television
1897 A.D.
STRASBOURG, GERMANY
In 1897 a German physicist, Karl Ferdinand Braun (1850-1918), modified the cathode-ray tube in such a way that the spot of green fluorescence formed by the stream of speeding particles shifted in accordance with the electromagnetic field set up by a varying current.
The device was called an oscilloscope, because the spot could follow and reveal the oscillations of the field. Braun's device was the ancestor of the present-day television screen.
åThe Other Universe Centers
350 B.C.
GREECE
At this time it seemed obvious to almost everybody that the Earth was solid, immovable, and the center of the Universe, with everything in the sky moving about it. It certainly looked that way, and why should the evidence of one's eyes be denied?
Nevertheless, the Greek philosopher Philolaus (5th century B.C.), a student of Pythagoras, felt that the Earth, with all the visible planets including the Sun, rotated about a central fire, which could not be seen. He was the first person we know of to suggest that the Earth moved and was not at the center of the Universe, but his suggestion was more mystical than rational and it won little credence.
The Greek astronomer Heracleides Ponticus (ca. 390-after 322 B.C.) did not go so far. He felt the Earth was the immovable center of the Universe, but he pointed out, about 350 B.C., that Mercury and Venus were never very far from the Sun. This could be accounted for by schemes the Greeks worked out that had each planet circling independently about the Earth, but to do so was difficult. Heracleides maintained that it was much simpler to suppose that Mercury and Venus circled the Sun, and that the Sun, with these two subsidiary bodies in attendance, circled the Earth. He was the first to suggest that there was at least some heliocentrism to the Universe, that at least some bodies revolved about the Sun and only secondarily about the Earth.
The Antarctic Ozone Hole
1985 A.D.
ANTARCTICA
In 1985 a hole in the ozone layer over the Antarctic was detected by the British Antarctic survey, and the ozone concentration elsewhere was abnormally low. This was taken as disturbing confirmation of the deleterious effect of chloro\fluoro\carbons on ozone.
ÉOzone
1840 A.D.
GERMANY
In 1840 a German chemist, Christian Friedrich Schönbein (1799-1868), working in a poorly ventilated laboratory, became conscious of a peculiar odor in the neighborhood of electrical equipment. He tracked it down and located a gas, which he named ozone, from the Greek word for "smell." It was later identified by an Irish physical chemist, Thomas Andrews (1813-1885), as a form of oxygen.
NPacemakers Savings Lives
1957 A.D.
UNIVERSITY OF MINNESOTA
The heart beats regularly, speeding up when exertion or emotion increases the oxygen requirements of the body and slowing down again in repose. For half a century, it had been known that a special patch of cells in the heart initiated the beat, and the patch was called, popularly, the pacemaker. When the pacemaker was diseased or damaged, the heartbeat could not be maintained properly and death might ensue.
Then an artificial pacemaker was devised that used a regular electrical pulse to initiate the heartbeat. At first such things were so bulky they had to be carried outside the body. The first pacemaker that was compact enough to be inserted under the skin in the patient's chest was devised in 1957 by the American physician Clarence Walton Lillehei. Pacemakers are now common among the elderly population.
ÄPaper is Invented in China
105 A.D.
CHINA
About 105, a Chinese eunuch, Tsai Lun (50?-?118), invented a method for making a thin, smooth writing surface so like papyrus that in Europe the name was retained. (In English, the new surface was called paper, a word obviously derived from papyrus.) The advantage of paper over papyrus was that, instead of being made from an increasingly rare reed, as papyrus was, it could be made from bark, hemp, rags, even low-quality wood -- almost any form of useless cellulose. Since cellulose is the most common organic compound, there has never been any long-term shortage of paper.
It took a thousand years for knowledge of paper to reach Europe.
╟The First Working Parachute
1797 A.D.
FRANCE
The principle of the parachute (a light object that presents a large surface to the air so that air resistance slows its descent) was simple enough. The French balloonist Jean-Pierre-François Blanchard (1753-1809) used one in 1785 to drop a dog in a basket safely to Earth from a balloon. The first case of a human being using a parachute successfully came in 1797 when another French balloonist, André-Jacques Garnerin (1769-1823), managed it.
èParchment
170 B.C.
EGYPT
Throughout ancient times, papyrus had been the material on which people had written, but Egypt was the only source, and the papyrus reed could not be grown quickly enough to supply the demand. Besides, the Egyptian rulers were not anxious to have other nations build up libraries. So when the small Hellenistic kingdom of Pergamum in western Asia Minor, under Eumenes II, who ruled from 197 to somewhere around 160 B.C., wished to build a library that would rival the one at Alexandria, naturally the Ptolemies would not cooperate by shipping the necessary papyrus.
The scholars working under Eumenes II therefore invented a new way of treating hides, about 170 B.C. Hides had often been used as writing material, but the Pergamese learned to stretch them, scrape them, and clean them, so that they ended with a thin white sheet that could be covered with writing on both sides. In later times, it came to be called parchment, which may be a mispronunciation of Pergamum.
Parchment is much stronger than papyrus and lasts practically forever. It can be scraped clean and used again (not always a good thing), whereas papyrus cannot be. Its greatest flaw is that it is much more expensive than papyrus. Then too, parchment cannot be formed into long sheets that can be rolled into a volume. Instead, separate sheets have to be glued together into a codex, which is the form in which modern books appear.
)Particle Spin
1925 A.D.
THE NETHERLANDS
Once Pauli had enunciated the exclusion principle, two Dutch physicists, George Eugene Uhlenbeck (1900-1988) and Samuel Abraham Goudsmit (1902-1978), at once pointed out that the fourth quantum number that Pauli had decided was required could be interpreted neatly as particle spin.
Each particle, such as an electron, could spin either clockwise or counterclockwise at a rate that could be expressed as + or -.
Eventually, similar spins (equal to 1/2 or some multiple thereof) were found to exist for almost all other particles.
╚Particles as Waves
1923 A.D.
PARIS, FRANCE
Even as Compton was demonstrating that waves showed particle properties the French physicist Louis-Victor-Pierre-Raymond de Broglie (1892-1987) was maintaining that, from theoretical considerations, every particle ought also to have an associated matter-wave and therefore show wave properties.
The wavelength of such matter-waves would be inversely related to the momentum of the particle (that is, its mass times its velocity). A massive particle such as a baseball, or even a proton, would have matter-waves of such ultrashort wavelengths that they would be difficult or impossible to detect. Electrons, however, should have matter-waves with wavelengths similar to those of X-rays.
Increasingly, after the work of Compton and de Broglie, physicists began to take the view that all objects had both wave and particle aspects. Where energy was low (and mass is a form of energy), the wave aspect would predominate, and where energy was high, the particle aspect would predominate.
To be sure, de Broglie's work was strictly theoretical. An actual demonstration of matter-waves would not come for several years, after which de Broglie would be awarded a share of the Nobel Prize for physics in 1929.
╤Electron Diffraction
1927 A.D.
U.S.A.
De Broglie had suggested that electrons and indeed all particles had wave aspects. No one since, however, had actually caught a particle behaving like a wave.
An American physicist, Clinton Joseph Davisson (1881-1958), however, was studying the reflection of electrons from a metallic nickel target enclosed in a vacuum tube. The tube shattered by accident, and the heated nickel promptly developed a film of oxide that made it useless as a target. To remove the film, Davisson heated the nickel for an extended period. Once this was done, he found that the reflecting properties of the nickel had changed.
Whereas the target had contained many tiny crystal surfaces before heating, it contained just a few large crystal surfaces afterward. Davisson therefore carried matters to a logical extreme and, in 1927, prepared a single nickel crystal for use as a target.
Once that was done, he found that an electron beam was not only refracted, but also diffracted just as a beam of X-rays would be. Diffraction was a characteristic property of waves, so in this way the wave aspect of electrons was detected.
In 1927 the British physicist George Paget Thomson (1892-1975), the son of J. J. Thomson, who had discovered the electron, sent a beam of fast electrons through thin gold foil and also demonstrated electron diffraction.
Thus de Broglie's theory was amply confirmed, and for doing so Davisson and Thomson were awarded shares in the Nobel Prize for physics in 1937.
¬Mechanical Adding Machines
1649 A.D.
FRANCE
In 1642 the French mathematician Blaise Pascal (1623-1662) invented a calculating machine that could add and subtract. It had wheels that each had 1 to 10 marked off along its circumference. When the wheel at the right, representing units, made one complete circle, it engaged the wheel to its left, representing tens, and moved it forward one notch.
With such a machine, as long as the correct numbers were entered into the device, there was no possibility of a mistake.
He patented the final version in 1649, but it was a commercial failure. It was too expensive, and most people continued to add and subtract on their fingers, on an abacus, or on a sheet of paper.
▓Pasteurization
1856 A.D.
PARIS, FRANCE
In 1856 France's wine industry was in a bad way. Wine often went sour as it aged, and millions of francs were lost. French chemist, Louis Pasteur (1822-1895) undertook the task of investigating the problem.
He studied samples of wine under the microscope and found that, when wine aged properly, it contained yeast cells that were spherical globules. Wine that was souring contained elongated yeast cells. He decided there were two types of yeast cells, one of which created lactic acid.
He also decided that the only solution to the problem was to kill the yeast cells, good and bad alike, after the alcohol had formed but before the acid had a chance to form. The wine should be heated gently at about 50° C and then stoppered and left to age without the influence of yeast.
The vintners were horrified at the suggestion, but they were desperate enough to try it, and they found that it worked. The process of gentle heating was called pasteurization, and it was eventually applied to milk, too, to prevent diseases that might otherwise be spread by its contamination. This episode turned Pasteur's attention to the world of microorganisms, with enormously important results.
¬Studying Sickness
1760 A.D.
ITALY
In 1760 the Italian anatomist Giovanni Battista Morgagni (1682-1771) published a book in which he described the 640 postmortems he had conducted in his long life. He carefully detailed the lives of his patients, the presence and development of disease, and the manner of dying and tried to interpret everything from the anatomical point of view. As a result, he is usually considered the founder of modern pathology.
ÿPaved Roads
1815 A.D.
BRISTOL, ENGLAND
Through most of history and in most places, roads were simply bare earth from which vegetation and obstructions had been removed, more or less. They tended to be dusty in dry weather, muddy in damp weather, and worn into ruts by vehicle wheels, so that they were only marginally better than no roads at all. The Romans had built good roads of stone (as had other stable civilizations), and Europe had depended on them, where they existed, ever since.
A British engineer and businessman, John Loudon McAdam (1756-1836), had for years been investigating roads and experimenting with road-building methods.
He recommended that roads be built higher than the fields on either side, for drainage, and that they be covered with large rocks, then with smaller rocks, the whole to be bound with fine gravel or slag.
In 1815 he finally had the opportunity to put his suggestions into practice on roads around Bristol, and their obvious superiority to what had existed before led to the rapid spread of macadamized highways, first in Great Britain and then in other countries. These paved roads immeasurably eased transportation and communication across land.
%Discovering Hormones
1902 A.D.
RUSSIA
The pancreas begins to secrete its digestive juice as soon as the acid food contents of the stomach enters the small intestine. How does the pancreas "know" that food, requiring digestion, is making its appearance? The natural assumption is that the entering food stimulates a nerve that in turn stimulates the pancreas. The Russian physiologist Ivan Petrovich Pavlov (1849-1936) suggested that this was so.
Two British physiologists, Ernest Henry Starling (1866-1927) and his brother-in-law, William Maddock Bayliss (1860-1924), tested the matter. They cut all the nerves leading to the pancreas -- yet it still performed on cue.
They then discovered that the lining of the small intestine secreted a substance (which they named secretin) under the influence of stomach acid. It was this secretin that stimulated the pancreatic flow. In short, then, Starling and Bayliss had discovered that it was possible for chemical messages as well as nerve messages to exist in the body. Eventually other chemical messengers were discovered and Starling suggested they be called hormones, from Greek words meaning "to rouse to activity." Secretin was the first hormone to be recognized as such, but epinephrine, isolated by American pharmacologist John Jacob Abel (1857-1938), turned out to be a hormone, also.
ΣImproper Diet Causes Pellagra
1915 A.D.
U.S.A.
Pellagra was a disease that was endemic in the American South after the Civil War. It didn't seem contagious, and Funk had speculated that it might be a vitamin-deficiency disease.
The Austrian-born American physician Joseph Goldberger (1874-1929) noted that it struck wherever the diet was monotonous and limited and did not include much in the way of milk, meat, or eggs.
In 1915 he conducted a dramatic experiment on prisoners in a Mississippi jail. Volunteers (who were promised pardons in return) were placed on a limited diet lacking meat or milk. After six months, they developed pellagra, which was relieved by adding milk and meat to their diet.
During this time Goldberger's study group went to great lengths to try to contract pellagra by contact with the patients, their clothing, and their excretions. They failed. Pellagra was definitely not contagious. Goldberger spoke of a P-P (pellagra-preventive) factor in the diet, but its chemical nature was as yet unknown.
/The Pendulum Clock
1656 A.D.
NETHERLANDS
Up to this time, the best timepieces were still the mechanical clocks of medieval days that could not keep time to better than a large fraction of an hour.
Galileo's discovery of the principle of the pendulum did not help immediately. An ordinary pendulum swings in the arc of a circle, and when it does that it doesn't have a constant period. The period becomes a little longer through a wide arc than through a narrow one.
If the pendulum could swing through a cycloid (very like a circle over a small arc), then the period would remain truly constant. Dutch astronomer Christiaan Huygens showed how to arrange matters so that the pendulum would swing through a cycloid. He then hooked it up to falling weights in such a way that the pendulum controlled the rate at which the weights fell and made it truly constant.
In 1656 Huygens had the first pendulum clock (or as it is sometimes called, grandfather's clock). It was the first timepiece that could tell time to a minute or better and was the first accurate enough to be useful to scientists.
╒The Rotation of the Earth
1851 A.D.
PARIS, FRANCE
Ever since the time of Copernicus it had been taken for granted that the Earth was rotating on its axis. Nevertheless, no one had actually demonstrated the fact. It seemed stationary, and no effect had been observed (other than the apparent rotation of the sky) that could be attributed to the rotation.
In 1851, however, Jean Foucault suspended a large iron ball, about two feet in diameter and weighing 62 pounds, from a steel wire more than 200 feet long, hanging inside the dome of a large church. The pendulum ended in a spike that just cleared the floor but would score a mark in the sand with which the floor was sprinkled.
The iron ball was drawn far to one side and tied to the wall by a cord. To prevent vibration when the ball was released, the cord was not cut, but set on fire. The swinging pendulum would then remain in the same plane, but the Earth, as it rotated, would change its orientation. If the pendulum had been at the North Pole, for example, the pendulum would have seemed to change its plane through a complete circle in 24 hours. At the latitude of Paris, the change would have taken 31 hours and 47 minutes. Thus the spectators were actually watching the Earth rotate under the pendulum.
-Validating Penicillin
1939 A.D.
ENGLAND
Fleming had discovered penicillin, but nothing much came of it until 1939. Then an Australian-born British pathologist, Howard Walter Florey (1898-1968), in collaboration with a German-born British pathologist, Ernst Boris Chain (1906-1979), set about isolating the actual antibacterial agent from the mold.
They reached their goal quickly and the groundwork was laid for penicillin's use during the dark days of war that were to follow. As a result, Florey, Chain, and Fleming were awarded the Nobel Prize for medicine and physiology in 1945.
gPenicillin
1928 A.D.
LONDON, ENGLAND
Some discoveries are made by accident. In 1928 Scottish bacteriologist Alexander Fleming (1881-1955), who had discovered lysozyme (an enzyme), left a culture of staphylococcus germs uncovered for some days. He was through with it, actually, and was about to discard the dish containing the culture when he noticed that some specks of mold had fallen into it. Around every speck, the bacterial colony had dissolved away for a short distance.
Bacteria had died and no new growth had invaded the area. Fleming isolated the mold and eventually identified it as one called Penicillium notatum, closely related to ordinary bread mold. He decided that it liberated some compound that, at the very least, inhibited growth, and he called the substance penicillin.
Fleming tested the mold on various types of bacteria and found that some were affected and some were not. Human cells were not affected. He did not go further, and it was to be over a decade before scientists returned to the problem. Nevertheless, for this discovery, Fleming received a share of the Nobel Prize for medicine and physiology in 1945.
The First Animal Enzyme
1836 A.D.
GERMANY
The discovery by Prout of hydrochloric acid in the stomach juices led to the natural assumption that it was the acid that acted to break down and digest foodstuffs in the stomach.
That this was not the case was shown by a German physiologist, Theodor Ambrose Hubert Schwann (1810-1882). He had found in 1834 that when an extract of the stomach lining was mixed with acid, it had a far greater power to dissolve meat than when acid alone was used. By 1836 he had extracted a substance from the stomach lining that proved particularly active in dissolving and digesting meat. He called it pepsin, from a Greek word meaning "to digest."
Pepsin, like diastase, was an enzyme, but diastase had come from the plant world. Pepsin was the first animal enzyme to be isolated.
TTapping the Chest
1761 A.D.
AUSTRIA
Methods for medical diagnoses were not many in these days. In 1761, however, an Austrian physician, Leopold Auenbrugger von Auenbrugg (1722-1809), published a book entitled Inventum novum (A New Invention) in which he pointed out that tapping the body, especially the chest area, and listening to the sound produced would give some indication of certain disorders of the internal organs. (He checked this by comparing the sounds he elicited with the state of the organs as revealed by postmortems.)
It took 40 years, however, before this diagnostic method became common in medicine.
╢The Periodic Table
1869 A.D.
RUSSIA
Newlands had tried to set up a table of elements that would allow them to be grouped into natural families. A Russian chemist, Dmitry Ivanovich Mendeleyev (1834-1907), now tried his hand at the task.
Like Newlands, Mendeleyev arranged the elements in order of increasing atomic weight. However, he did not try to be too simple and arrange them in a fixed gridwork of seven elements per row. Instead, letting himself be guided by the valence of each element, he allowed the length of the period (row) to increase. He had hydrogen all by itself, then two periods of seven elements each, then two periods of 17 elements each. He had prepared what is now called the periodic table of the elements.
He published his table on March 6, 1869, beating out others who were attempting the same task, notably the German chemist Julius Lothar Meyer (1830-1895).
In 1871 Mendeleyev went a step further, one which put him in a class by himself. In order to keep the valences and other properties of elements similar as one looked down the columns of his table, he had to leave empty spaces. He did not view this as an imperfection in his table. He merely announced that the empty spaces represented elements that had not yet been discovered.
He picked out three gaps in particular, one under boron, one under aluminum, and one under silicon, and called them eka-boron, eka-aluminum, and eka-silicon. (Eka is "one" in Sanskrit, so that each element is one below the indicated element in the periodic table.) Mendeleyev went on to predict the properties of the missing elements according to their places in the table. Naturally, no one paid this serious attention at the time, but Mendeleyev turned out to be right.
\Permanent Gases
1845 A.D.
ENGLAND
In 1845 Faraday returned to the task of liquefying gases. He made use of a mixture of solid carbon dioxide and ether as a cooling agent, and he used higher pressures than he had in his earlier experiments.
Working in this way, Faraday managed to liquify many gases. Indeed, there were only six gases known in 1845 that Faraday could not liquefy despite his efforts. They were hydrogen, oxygen, nitrogen, carbon monoxide, nitric oxide, and methane.
These nonliquefiable gases were called, at least for a time, permanent gases, and they represented challenges that chemists tackled grimly.
2Mathematics and Perspective
1436 A.D.
ROME, ITALY
The Renaissance was a great age of realism in art, and the Italian painters wanted their canvases to appear to have three dimensions. In order to do that, they had to have proper perspective: lines had to come together as they seem to do in real life. The Italian artist Leon Battista Alberti (1404-1472) published a book in 1436 in which he described the proper method of achieving perspective, handling the matter in a careful mathematical manner. This proved to be a forerunner of projective geometry, which was developed four centuries later.
îCulturing Viruses
1948 A.D.
HARVARD UNIVERSITY, CAMBRIDGE
A great many of the advances in the fight against bacterial infection over the previous three-quarters of a century had resulted from the ability to grow pure bacterial cultures in the laboratory. This meant the bacteria could be studied easily and methods for slowing or stopping their growth could be developed.
Viruses, however, grow only within living cells, and working with organisms is much slower and less certain than working with Petri dishes. For this reason, viral diseases were far more difficult to fight than bacterial diseases.
Of course one needn't grow the viruses in adult organisms. They could be grown in the developing embryos in chicken eggs, or in those same embryo cells mixed with blood. The trouble was that although viruses would grow there, so would bacteria, and the bacteria would mask the viruses.
Once penicillin became available, however, it could be added to the chicken embryo broth. This prevented the growth of bacteria but did not affect the viruses. The American microbiologist John Franklin Enders (1897-1985) developed this technique in 1948, and it became useful in searching for ways to fight viral diseases, notably poliomyelitis (infantile paralysis). For this work, Enders, along with his colleagues Thomas Huckle Weller (b. 1915) and Frederick Chapman Robbins (b. 1916), shared the Nobel Prize for medicine and physiology in 1954.
MInventing the Phonograph
1877 A.D.
MENLO PARK, NEW JERSEY
In 1876 Thomas Edison had opened the first industrial research laboratory, at Menlo Park, New Jersey. In 1877, the same year in which he improved the telephone mouthpiece in a crucial manner, he also made what he always said was his favorite invention -- the phonograph (from Greek words meaning "sound-writing").
He put tinfoil on a cylinder, set a free-floating needle skimming over it as the cylinder turned, and connected a source that would carry sound waves to the needle. The needle, vibrating in time to the sound waves, impressed a wavering track on the tin. Afterward, following that track, the needle reproduced the sound waves in a form that was a bit distorted but recognizable.
We all know what the phonograph, and its much improved descendants, have done to bring music (good and bad) into the home.
White Blood Cells
1883 A.D.
FRANCE
A Russian-born French bacteriologist, Élie Metchnikoff (1845-1916), found that in simple animals there were semi-independent cells that were capable of ingesting small particles. Any damage to the animals brought these cells to the spot at once.
In 1883 Metchnikoff followed up this lead and studied more complicated animals. He was able to show that the white cells in blood were also semi- independent and were capable of ingesting bacteria. The white cells flocked to the site of any infection, and what followed was a battle between bacteria and what Metchnikoff called phagocytes (Greek for "eating cells"). When the phagocytes lost heavily, their disintegrated structures made up pus.
The white cells, Metchnikoff held, were an important factor in resistance to infection and disease. For this work, he received a share of the Nobel Prize in physiology and medicine in 1908.
╗Medical Uses of Plants
50 A.D.
GREECE
The Greek physician Pedanius Dioscorides (ca. 40-ca. 90) served in the Roman armies and had an opportunity to study the plant life in large parts of the Mediterranean world. He was interested chiefly in the medical applications of plants, and in his book De Materia Medica, he described about 600 plants and nearly a thousand drugs. This was the first important work on pharmacology (from Greek words meaning "the study of drugs").
≈Phoebe: A Moon of Saturn
1898 A.D.
WASHINGTON, D.C.
In 1898 the American astronomer William Henry Pickering (1858-1938) discovered a ninth satellite of Saturn, which he named Phoebe, after still another of the siblings of Saturn (Cronos) in the Greek myths. It was far more distant from Saturn than the satellites discovered earlier, and it revolved around the planet in a retrograde direction (clockwise rather than counterclockwise, if viewed from high above Saturn's north pole), so that it is considered to be a captured asteroid.
GDiscovering Phosphorus
1669 A.D.
GERMANY
Of the substances chemists now consider to be elements, nine were known to the ancients. These included seven metals: gold, silver, copper, tin, iron, lead, and mercury; and two nonmetals: carbon and sulfur. Four more elements were probably known and were unmistakably described by the medieval alchemists: arsenic, antimony, bismuth, and zinc. We do not know who first discovered any of these elements, or when.
The situation changed when the German chemist Hennig Brand (d. ca. 1692) began searching for something that would enable him to create gold. For some reason, he thought he would find it in urine. He did not succeed in making gold, but perhaps as early as 1669, he obtained a white waxy substance that glowed faintly in the air and which he therefore called phosphorus (from Greek words meaning "light-bearer"). The faint glow was due to the spontaneous combustion of phosphorus in air.
All the 90 or so elements discovered after 1669 can be attributed to a specific person and a specific time. Brand's discovery of phosphorus is the first of which this can be said.
eInvention of the Photocopier
1958 A.D.
U.S.A.
An important aspect of office procedures is the copying of documents. Copying by hand is slow and cumbersome, and errors inevitably arise. Carbon paper and mimeograph machines were great improvements but usually messy.
An American physicist, Chester F. Carlson (1906-1968), strove to find a method of copying that would use dry powder, electric charge, and light. Because nothing moist is used, the procedure he found is called xerography (Greek for "dry writing"), and because light is used, it is called photocopying. It works by giving paper a positive electric charge and the powder a negative electric charge, so that the powder clings to those places where light does not penetrate and destroy the charge. In other words, the powder clings to the shadows cast by the opaque printing of the object being copied. The application of heat fixes the powder on the paper and the copy is produced. There is no mess and no moisture, and it can be done very quickly.
Carlson worked on the method for some 20 years and finally perfected it for office use in 1958. When he introduced the device, he called it Xerox.
The Photoelectric Effect
1905 A.D.
GERMANY
In 1905 the photoelectric effect, as observed by Lenard, was combined with quantum theory by Einstein.
He showed that if light consisted of quanta, with energies proportional to frequency (inversely proportional to wavelength), then the atoms in a metal surface could only absorb intact quanta. Furthermore, long-wavelength quanta would not supply enough energy to eject an electron from the metal, no matter how intense the light might be. But as wavelength grew shorter, energy quanta grew larger, and a point would be reached where the energy was just sufficient to eject an electron. The shorter the wavelength beyond that, the more energetic the ejected electron would be and the more speedily it would travel. Since some metals may hold electrons more firmly than others, the critical wavelength must be shorter in some cases than in others.
Einstein's analysis had several consequences.
1. It explained the photoelectric effect completely. There have not had to be any extensions or additions to the explanation since.
2. It made use of quantum theory to explain a phenomenon unexplainable otherwise, and a phenomenon moreover that had not been in Planck's mind when he worked out the theory. If quantum theory were simply a mathematical device needed to make black-body radiation come out right, it wouldn't be likely to be applicable without modification to an altogether different phenomenon.
Einstein's work therefore established quantum theory as legitimate and not merely a mathematical trick.
3. It showed that light could be treated as particles in some respects.
Newton's particles and Huygens's waves were thus combined into a whole that was far more complex and useful than could have been imagined on the basis of 17th-century knowledge. The particle aspects of light, and of electromagnetic radiation generally, are referred to nowadays as photons.
It was for this work on the photoelectric effect (not on his still greater discoveries in connection with relativity) that Einstein gained a Nobel Prize in physics in 1921.
#The Photographic Negative
1841 A.D.
ENGLAND
In the early years of photography, the photograph that was produced looked like the object photographed (a photographic positive) and was the only one of its type. One could not make copies of it.
In 1841, however, an English inventor, William Henry Fox Talbot (1800-1877), patented a device in which a photographic negative could be formed on glass, with all the naturally light areas dark and vice versa. Light could then be passed through the negative onto sensitized paper and a negative of the negative could be made, with all the light areas light again and all the dark areas dark.
The advantage of this two-stage process was that, given a negative, any number of positive prints could be made. In 1844, in fact, the first book was published that was illustrated with photographs.
⌐Photosynthesis
1779 A.D.
NETHERLANDS
Joseph Priestley had shown that plants could make air breathable after it had been filled with carbon dioxide. In 1779 a Dutch physician, Jan Ingenhousz (1730-1799), repeated the experiments and confirmed Priestley's findings. His crucial added discovery, however, was that plants consumed carbon dioxide and produced oxygen only in the light. In the dark, plants, like animals, consumed oxygen and produced carbon dioxide.
Because of the importance of light, and because plants in the process produced not only light but also the large molecules of their tissues, the process came to be called photosynthesis, from Greek words meaning "to put together by light."
ÆPhotovoltaic Cells
1954 A.D.
BARSTOW, CALIFORNIA
Photovoltaic cells continued to be improved, and eventually some with efficiencies of up to 30 percent appeared. As efficiency rose and the cost of manufacture fell, it seemed the time might come when electricity could be manufactured directly out of sunlight. If the Sun were used in that fashion, we would never run out of the supply and there would be no chemical pollution. @
Photoelectric Effect
1902 A.D.
GERMANY
Hertz had first noted the photoelectric effect -- the greater ease with which electric sparks cross small gaps when ultraviolet light falls upon those gaps -- 14 years before. Now that electrons were known, the photoelectric effect could be studied more effectively.
Lenard showed in 1902 that the electrical effects produced by light falling upon certain metals were the result of electrons being emitted from the metal surface. He showed that only light of a certain wavelength or shorter could bring about electron emission from a particular metal, and that the crucial wavelength was different for different metals.
Increasing intensity of light of a given wavelength resulted in the emission of a greater number of electrons, but the energy of the individual electrons remained the same. If the wavelength decreased, the electrons emitted had higher energy; if the wavelength increased, the electrons emitted had lower energies.
There was no way of explaining this by 19th-century physics. Even unexplained, however, the photoelectric effect made it appear that electrons existed in matter even when electric currents were not involved. The fact that identical electrons were emitted by various metals made it seem that electrons were a constituent of all atoms without exception.
#Pi Equals 3.1415926...
1596 A.D.
NETHERLANDS
The ancient Greeks had their favorite problems and one of them was squaring the circle; that is, given a circle of a particular size, to construct a square with the same area. The rules were that you could only use a straight- edge (something that would draw straight lines) and a compass (something that would draw circles) and you had to do it in a finite number of steps.
Unfortunately, they could never solve that problem.
In working with it, though, they got involved with the ratio of the circumference of a circle to its diameter, a ratio that we now refer to as pi (one of the Greek letters). Anyone can measure the diameter and then run a piece of string around the circumference, straighten it, and measure that, too. It turns out that the circumference (for any circle at all) is just a little over 3 times as long as the diameter. But what is the ratio exactly?
There are geometric ways of trying to get the exact ratio, and Greek scientist Archimedes (ca. 287-212 B.C.) had gotten a figure of about 3.142. Better values were obtained in later centuries until, in 1596, the Dutch mathematician Ludolf van Ceulen (1540-1610) obtained a value of pi to 20 decimal places. (Later in life, he got it to 35 decimal places.)
Even that didn't give an exact value, but it was so nearly exact that no reasonable computation involving pi would need a more exact value. (In Germany, pi is still sometimes called Ludolf's number.) Since then, pi has been obtained to a vastly greater number of decimal places, but even so there is no exact figure.
NSleeping Pills
1863 A.D.
GERMANY
In 1863 the German chemist Adolf von Baeyer (1835-1917) discovered barbituric acid. (There is a story that he named it for a girlfriend of the moment whose name was Barbara.) Barbituric acid is the parent substance of a family of compounds known as barbiturates, which are well known today for their use in sleeping pills.
òDiscovering the Pion
1947 A.D.
ENGLAND
Yukawa had predicted the existence of a particle with mass between that of an electron and a proton. It would serve as an exchange particle, holding together the protons and neutrons within the nucleus despite the electromagnetic repulsion among the protons, Strong Interaction). Anderson detected a particle of intermediate mass, the muon, but it lacked the necessary properties to fulfill the role Yukawa had laid out for it.
Meanwhile, the English physicist Cecil Frank Powell (1903-1969) had worked out a new method of particle detection. Instead of having particles strike a cloud chamber and then photographing the results, he had the particles strike a photographic emulsion so that the result could be recorded directly.
In 1947 he exposed photographic plates in the Bolivian Andes and picked up evidence of a particle of intermediate mass that was not the one Anderson had discovered. Powell named it the pi-meson, which was eventually shortened to pion.
Whereas Anderson's muon had all the properties of an electron except for its greater mass, so that it was a lepton, the pion shared certain properties with the more massive particles and was lumped with them as a hadron. The pion interacted readily with protons and neutrons (as the muon did not) and had all the properties required for it to be Yukawa's predicted particle.
For this work, Powell was awarded the Nobel Prize for physics in 1950.
d The Speed of Falling Bodies
1589 A.D.
PISA, ITALY
Aristotle had stated that the heavier an object was, the more rapidly it would fall. It seemed reasonable to say so. Why shouldn't a heavier body fall more rapidly? It is clearly being attracted to Earth more strongly, or it wouldn't be heavier. Furthermore, anyone who watches a feather, a leaf, and a stone falling will see at once that the stone falls faster than the leaf, which in turn falls faster than the feather.
The trouble is that light objects are impeded by air resistance, and in order to avoid that one should consider only relatively heavy objects. Thus, if one observes the falling of a rock that weighs 1 pound and another that weighs 10 pounds, air resistance is insignificant in either case. Do we then see that the 10-pound rock nevertheless falls faster than the 1-pound rock?
In 1586, Dutch mathematician Simon Stevin (1548-1620) is supposed to have dropped two rocks at the same time, one considerably heavier than the other, and showed that they struck the ground at the same time. Later accounts said it was Galileo who demonstrated this by dropping different weights simultaneously from the Leaning Tower of Pisa. Both stories may or may not be true.
What is certain, though, is that in 1589 Galileo started a series of meticulous tests with falling bodies. Such bodies fall too rapidly to make it easy to measure the rate of fall accurately, especially since no accurate way of measuring short periods of time had yet been worked out.
Galileo therefore allowed balls to roll down inclined planes. The more nearly level the plane, the more slowly the balls moved under the pull of gravity and the more easily their rate of fall could be measured by primitive methods such as water dripping out of a small hole. In this way Galileo found it quite easy to show that as long as the balls were heavy enough to be relatively uninfluenced by air resistance, they rolled down an inclined plane at the same rate.
He was also able to show that the balls rolled down the inclined plane with a constant acceleration -- that is, they gained speed with time at a constant rate, under the constant pull of gravity.
This settled another important point. Aristotle had held that in order to keep a body moving, a force had to be continually applied. This again seemed to fit observation. If an object were sent sliding across a floor, it would quickly slow to a stop. To keep it moving, you would have to keep pushing.
For this reason, it was felt that the planets in their eternal movement about the Earth had to be continually pushed by angels.
Galileo's observations showed that a constant push was not necessary to keep an object moving, if friction was removed. If a constant pull was exerted by gravity, for instance, an object moved with a constantly increasing speed. Consequently, no angels were required to keep the planets moving.
Galileo's experiments on moving bodies were so impressive that, even though he was not the first to conduct experiments -- French scholar Peter Peregrinus (13th century) had done so more than three centuries before -- he is usually given credit for having founded experimental science.
LPi as Transcendental
1882 A.D.
GERMANY
In 1882 the German mathematician Ferdinand von Lindemann (1852-1939) studied pi, the ratio of the circumference of a circle to its diameter.
Its value is 3.14159 . . . and so on, forever, in a nonrepeating decimal, for pi is an irrational number.
Lindemann was able to show that it was more than irrational. It was transcendental, as Hermite had shown e to be. Therefore, pi could not serve as a solution for any conceivable polynomial equation, and that meant that the problem of squaring the circle by straightedge and compass in a finite number of steps was impossible.
░
Small Packets of Energy
1900 A.D.
GERMANY
German physicist Gustav Robert Kirchhoff (1824-1887) had pointed out that a black body (one that absorbed all electromagnetic radiation that fell on it) would radiate at all wavelengths if heated. Thus, a hollow body with a small hole in it would absorb all the radiation that entered through the hole, for virtually none of it would be reflected and find its way out again. If such a body was heated, radiation would therefore emerge from the hole at all wavelengths, with very little at the extremes and with a peak at some intermediate value. The higher the temperature, the shorter the wavelength of the peak value.
A number of physicists tried to work out mathematical equations for the distribution of wavelengths in such black body radiation. British physicist John William Strutt, Lord Rayleigh (1842-1919) and Wien both advanced equations in 1900, but Rayleigh's worked well only for the long-wavelength half, and Wien's only for the short-wavelength half. Neither one could work out an equation that gave the distribution across the board.
Then a German physicist, Max Karl Ernst Ludwig Planck (1858-1947), produced an equation that did just that. In order to derive that equation, he had to assume that energy was given off not continuously but in discrete pieces, and that the size of the piece was inversely proportional to the wavelength. Thus, since violet light had half the wavelength of red light, violet light would be delivered in pieces that were twice the size, and therefore twice the energy content, of red light.
Planck called the bits of energy quanta (singular, quantum, a Latin word meaning "how much?"). He worked out the relationship between energy and wavelength (or energy and frequency, since frequency is 1 divided by the wavelength), making use of a very small value called Planck's constant, which represents the "graininess" of energy. Since Planck's constant is exceedingly small, energy has a very fine grain indeed, and it is not noticeable in most circumstances, so that the laws of thermodynamics could be deduced as though energy were a continuous fluid without grain. The problem of black body radiation was the first in which the graininess had to be taken into account.
There was no evidence, at first, for the existence of quanta, except for the fact that it made the equation for black body radiation possible. Even Planck himself suspected that quanta might be only a mathematical device that had no physical meaning.
Nevertheless, the quantum theory, as it is now called, proved so fundamental that all physics prior to 1900 is called classical physics and all physics after 1900 modern physics. For his work, Planck received the Nobel Prize for physics in 1918.
~Rotating Polarized Light
1815 A.D.
FRANCE
Berzelius in 1807 had divided compounds into organic and inorganic. Organic compounds were those obtained from organisms (living or dead) or related to compounds so obtained. Those that had nothing to do with such organisms were inorganic.
Now Malus's discovery of polarized light gained some importance with a discovery made by Biot. Ordinarily, the polarized light would be shining brightly in a certain plane, so that if two pieces of Iceland spar were lined up parallel, the light would pass undimmed through both.
If, however, the polarized light, en route from one piece of Iceland spar to the other, was made to pass through some organic liquid, the second piece of Iceland spar had to be turned for the polarized light to shine brightly again.
This meant that the plane of the polarized light had twisted on passing through the organic liquid. For some liquids, it twisted clockwise, for others counterclockwise.
Biot suggested that this might be due to some asymmetry in the structure of the molecules of the organic substance. He was right in this, but there was as yet no way of determining what that asymmetry might be.
Planetary Tables
1627 A.D.
GERMANY
If Kepler's elliptical planetary orbits really presented an advance over the circular orbits of both Ptolemy and Copernicus, then using them ought to result in improved planetary tables.
Kepler spent some years working out new tables on the basis of his elliptical orbits, using Napier's logarithms in his calculations -- the first important scientific use of the new technique. In 1627 they were published as the Rudolphine Tables, in memory of Rudolf II (1552-1612), who had become Holy Roman Emperor in 1576 and who had supported Kepler.
They were indeed the best tables of planetary motions yet prepared. The publication included tables of logarithms and a star map based on the work of Tycho and expanded by Kepler to include over a thousand stars.
óThe Planetesimal Hypothesis
1905 A.D.
FRANCE
Laplace's nebular hypothesis of the origin of the Solar System had held sway for a century, even though astronomers had grown steadily more dubious about it. It turned out that most of the angular momentum in the Solar System was concentrated in the planets. (Jupiter alone has 60 percent of all the angular momentum in the Solar System because of its rapid rotation and the whirling of its major satellites.) There seemed no way in which the Solar System could have been formed by the slow condensation of a vast nebula without virtually all the angular momentum ending up at the core -- in the body that became the Sun.
Despite this concern, no alternate hypothesis was advanced till the American geologist Thomas Chrowder Chamberlin (1843-1928) and the American astronomer Forest Ray Moulton (1872-1952) came along with one.
Chamberlin had been working on it since 1900 and, in 1905, he and Moulton advanced the suggestion that the Solar System began when the Sun, already in existence, passed near another star. The gravitational influence of each star tore gouts of matter out of the other, and the gravitational pulls of the stars as they separated gave those gouts of matter a sidewise yank so that they became planets with high angular momentum.
In the process of planet formation, the gouts of solar matter condensed into small solid pieces called planetesimals, and these came together little by little to form planets. This planetesimal hypothesis retained a certain popularity for nearly half a century.
If it were true, it would mean that there were very few planetary systems in the Universe, since the close approach of two stars is an excessively rare phenomenon.
AModern Plant Classification
1686 A.D.
ENGLAND
There is a natural tendency for people interested in natural history to classify animals and plants. Aristotle (384-322) classified the former, and Theophrastus (ca. 372-ca. 287) classified the latter. The ancients, however, had limited access to living things because so much of the world was beyond their ken.
The first to do a modern job of classification was an English naturalist, John Ray (1627-1705). Starting in 1686, he published what eventually came to be a painstaking three-volume classification of 18,600 different plant species. While such work might seem to be mere listing, the basis for the classification requires a good deal of ingenuity, and on the whole, Ray made good decisions in these matters. Classifications such as his made the matter of biological evolution seem an overwhelming likelihood.
╕Plants and Carbon Dioxide
1771 A.D.
ENGLAND
Carbon dioxide was well known by this time to support neither combustion nor animal life. Joseph Priestley thought of checking to see whether plants, as well as animals, were unable to live in carbon dioxide.
In 1771 he placed a lit candle in an enclosed volume of air until the candle would burn no more and the air was filled with carbon dioxide. He then placed a sprig of mint in a glass of water and placed it in the enclosed air.
The plant did not die. It lived there for months and seemed to flourish.
What was more, at the end of that time, a mouse could be put into that volume of air and live -- and a candle would burn.
Whatever it was about air that supported combustion and animal life, and that was converted into carbon dioxide by burning candles and breathing animals, was restored by plant life. This was the first indication that plants and animals formed a chemical balance that kept Earth's atmosphere breathable.
8Plant Reproduction
1682 A.D.
ENGLAND
Before modern times, plants were usually thought to be not truly alive in the sense that animals were. In the biblical story of creation, plants grow as soon as dry land appears. They seem to be part of the land and meant only for food. In contrast, on the fifth and sixth days, God is described as specifically creating animal life and instructing it to multiply. (Even today, vegetarians announce that their love of living things keeps them from eating animal food, although the plant life they eat is every bit as alive.)
Some of this disdain for plant life was broken down, in 1682, by the English botanist Nehemiah Grew (1641-1712), who showed that plants reproduced sexually, that they had sexual organs, and that individual grains of pollen were the equivalent of the sperm cells of the animal's world.
YPlatinum as a Catalyst
1823 A.D.
GERMANY
As early as 1816, Davy had noticed that certain flammable gases seemed to ignite and burn more readily in the presence of platinum than in its absence.
In 1823 the German chemist Johann Wolfgang Döbereiner (1780-1849) found that the effect was heightened when he used powdered platinum. In fact hydrogen would ignite and burn in air without having to be heated if powdered platinum was present. Nor was the platinum consumed in the process. It was a catalyst.
Döbereiner went on to devise an automatic lighter in which a jet of hydrogen could be played upon powdered platinum, causing the hydrogen to flame at once.
This could be used to light a cigar, for instance.
It wasn't practical, to be sure. The platinum was very expensive, and although it wasn't consumed, it was quickly poisoned by impurities in the hydrogen or in the air and then wouldn't work until it was cleaned up again.
In time, however, it was discovered that platinum (and also other, cheaper metals) would catalyze many reactions involving hydrogen, and such metal- catalyzed reactions became very important in industry.
╥Properties of Platinum
1748 A.D.
EGYPT
Gold, silver, and copper are not the only rare metals sometimes found in free metallic form. Another is platinum. A metallic casket found among the relics of seventh century B.C. Egypt is reported to be of platinum. In general, however, the existence of this metal remained unremarked and unknown.
For one thing, platinum is as rare as gold, but it lacks gold's ostentatious beauty. Platinum has a dull, leaden color when unpolished that does not attract the eye.
In 1748, however, a Spanish scientist, Antonio de Ulloa (1716-1795), published a report on his travels in South America. In it, he reported on platina (from a Spanish word for "silver," chiefly because it was a free metal that lacked the pronounced color of gold or copper). He remarked on its peculiar properties, for when properly examined, it turned out to be denser than gold, higher-melting, and even less reactive. Eventually, it proved extremely useful to scientists for just these properties.
∙Plate Glass
1688 A.D.
FRANCE
For centuries clear glass had been a luxury item. Little by little, though, the art of pressing or casting glass (that is, the making of sheets by some means other than blowing) was developed. At first the sheets were quite small, but by 1688 in France, large sheets were being made for mirrors and for coach windows.
This meant that glass became increasingly common and cheap, so that its use became almost universal. Glass now allowed light to enter a room while keeping wind and rain out.
3Planetary Rotation
1665 A.D.
FRANCE
The fact that features could be made out on the surface of some of the planets meant that those features could be observed from night to night as they passed around the planet to the other side and across the face again. By watching long enough and dividing the time elapsed by the number of turns, an accurate measure of the rotation rate of the planet could be obtained.
In this way, in 1665, the Italian-born French astronomer Gian Domenico Cassini (1625-1712) determined that Mars rotated in 24 hours 40 minutes, while Jupiter rotated in 9 hours 56 minutes.
Since these planets rotated on their axis as Earth did, it made them seem more like our planet. As astronomical discoveries continued, Earth seemed less and less a special case -- except insofar as we are here on Earth and not anywhere else.
¬Plant Classification
1813 A.D.
FRANCE
The French botanist Augustin-Pyrame de Candolle (1778-1841) began a large encyclopedia of plant life in 1813, a project that outlasted him. Only seven of the 21 volumes had been published by the time of his death. His system of plant classification was far more scientific than that of Linnaeus and is still used today. It was Candolle who, in 1812, first used the word taxonomy to represent species classification.
öPlant Nourishment
1705 A.D.
ENGLAND
The English physiologist Stephen Hales (1677-1761) began experiments on plants in 1705. His most important suggestion was that air contributed to the nourishment of plants, thus correcting Helmont's misconception of a century before to the effect that only water counted.
Hales was the first person to collect gases by bubbling them through water and trapping them in an upside-down vessel.
φPlant Strains
1871 A.D.
SANTA ROSA, CALIFORNIA
In 1871 an American naturalist, Luther Burbank (1849-1926), began his life's work of cultivating plants and watching for new strains. He specialized in producing new strains of fruit and, for example, developed 60 varieties of plums in his lifetime. He also developed new varieties of flowers. His work, which caught the public eye, beautifully illustrated the capacity for variation in organisms and helped support Darwin's theory of evolution by natural selection.
φThe First Ploughs
3500 B.C.
SUMERIA (Iraq)
In the early days of agriculture, seed used to be scattered over the ground, where it grew in anarchic fashion. Eventually it was discovered that if the grain was planted in separated rows, it was then easier to water, to weed, and to harvest.
In its simplest form, the plough was a forked stick that was dragged through the soil making a furrow in which the seeds were planted. This greatly hastened the rate of sowing. A plough was first used in Sumeria about 3500 B.C.
åPlate Tectonics
1953 A.D.
U.S.A.
For 30 years it had been known that there was a mountain range down the middle of the Atlantic Ocean. Eventually it was understood that this was part of a world-girdling range called the Mid-Oceanic Ridge.
In 1953 the American physicists Maurice Ewing (1906-1974) and Bruce Charles Heezen (1924-1977) discovered that a deep canyon ran the length of the ridge. It was called the Great Global Rift. There were places where the rift came quite close to land: it ran up the Red Sea between Africa and Arabia and skimmed the borders of the Pacific through the Gulf of California and up the coast of the state of California.
The rift seemed to break the Earth's crust into plates tightly joined as though fitted together by a skilled carpenter. They were therefore called tectonic plates, from a Greek word for "carpenter." The study of the evolution of the Earth's crust in terms of these plates is called plate tectonics, and it has totally revolutionized geology, explaining a great deal that had been mysterious before.
There are six large tectonic plates and a number of smaller ones, and it is along the boundaries of the plates that Earth's quakes and volcanoes seem to be concentrated. One plate, which includes most of the Pacific Ocean, and with boundaries of the eastern coast of Asia and the western coast of America, accounts for about 80 percent of the earthquake energy released on Earth.
½Discovering Pluto
1930 A.D.
FLAGSTAFF, ARIZONA
Neptune had been discovered by British astronomer John Couch Adams (1819-1892) and French astronomer Urbain-Jean-Joseph Leverrier (1811-1877) because Uranus was not moving in its orbit exactly as it should, so that the gravitational field of a more distant planet was suspected.
Neptune's presence reduced but did not entirely wipe out the discrepancies in Uranus's orbit, and some astronomers thought that a still more distant but fairly large planet might exist beyond Neptune.
Percival Lowell, who was so enthusiastic about Martian canals, was also enthusiastic about this "Planet X" and spent much of his time calculating its possible orbit and then searching for it. He died without having found it, but at Lowell Observatory, which he had founded, the search went on.
The American astronomer Clyde William Tombaugh (b. 1906) continued the search methodically. His technique was to take two pictures of the same small part of the sky on two different days. Each of these would show from 50,000 to 400,000 stars. Despite all those stars, the two plates would be identical if the spots of light were stars, and only stars. If the two plates were projected on a screen in rapid alternation, none of the stars would seem to move. If one of the "stars" was really a planet, however, one that had moved against the starry background during the interval between photographs, as the plates were alternately thrown upon the screen, that one object would seem to dart back and forth.
On February 18, 1930, Tombaugh found such a flicker in the constellation Gemini. From the smallness of the shift, the object had to be moving very slowly and must therefore lie beyond Neptune. On March 13, 1930, the 75th anniversary of Lowell's birth, the discovery was announced. The new planet was named Pluto, first because that god of the nether darkness was appropriate to a planet swinging farthest out from the light of the Sun, and second because the first two letters were the initials of Percival Lowell.
In time, though, Pluto turned out to be a small planet incapable of influencing Uranus's orbit measurably. The possibility of another large planet beyond Neptune therefore remains to this day.
╙Pluto's Diameter
1950 A.D.
LONDON, ENGLAND
Pluto had been discovered by considering the unexplained perturbation of Uranus's orbit, assuming that the gravitational pull of an undiscovered planet caused it, and calculating the place where that planet must be. (Neptune had also been discovered in this way, but its presence had not corrected all of the perturbation of Uranus, just most of it.) For Pluto to have caused the perturbation, it would have to be several times as massive as Earth, and at first this was assumed to be the case, but it turned out to be considerably dimmer than would be expected of a massive planet, and that caused considerable consternation.
In 1950 Kuiper, the discoverer of Miranda and Nereid, managed to see Pluto as a disk and to measure its apparent width. He showed that its diameter could not be more than 3,600 miles, which made it smaller than Mars and explained its dimness. If Pluto was as small as this, it could not be the source of the perturbation of Uranus, and it must have been located in the right spot by sheer coincidence.
This would seem to indicate that a planet massive enough to account for the perturbations of Uranus must still exist beyond Neptune's orbit, but if so, it has not yet been located.
!Inventing Polaroid
1932 A.D.
BOSTON, MASSACHUSETTS
Nicol had made use of Iceland spar to produce an instrument that could be used in the study of polarized light. Some substitute for Iceland spar that would be cheaper and easier to work with would have been welcome, but none was known.
To be sure, there were certain organic crystals that behaved as Iceland spar did, but they did not readily produce crystals of the proper size, and the crystals would have been far too fragile to work with in any case.
An American inventor, Edwin Herbert Land (b. 1909), had the idea that a single crystal was not necessary. A myriad of tiny crystals would do if all were oriented in the same direction.
In 1932 he devised methods of aligning the crystals and of then embedding them in clear plastic. When set, this served nicely to keep them from drifting out of alignment and made their fragility irrelevant. The result was given the trade name Polaroid, and it quickly replaced Iceland spar in scientific instruments. It also came to be used in automobile windshields and in spectacles.
·Pollination
1763 A.D.
GERMANY
The existence of sexuality in plants must have seemed strange, since plants, being essentially immobile, cannot indulge in the kind of sex that animals do.
In 1763, however, a German botanist, Josef Gottlieb Kohlreuter (1733-1806), pointed out the manner in which plant pollen can be blown by the wind to reach female organs in a purely random manner. Because of this randomness, plants that depend on wind pollination must produce pollen in vast amounts.
He also pointed out that a more efficient process is to have bees or other similar animals do the job. A bee enters a flower in search of nectar (the bribe to make it enter). Pollen coats the bee's fuzzy covering, and when the bee visits the next flower, that pollen rubs off on the pistil.
ÿPolonium and Radium
1898 A.D.
FRANCE
Marie and Pierre Curie continued to work on the radiations produced by uranium.
In 1898 Marie Curie showed that thorium, another heavy metal, also produced radiations, and she coined the term radioactivity for the phenomenon, so that it could be said that both uranium and thorium were radioactive.
She also discovered that although pure uranium compounds were always radioactive only to the extent that uranium was present, some uranium ores produced far more radioactivity than could be accounted for by the uranium present. It seemed to her that the ores must contain other elements (in small quantities or they would have been discovered earlier) that were much more intensely radioactive than uranium.
In July 1898 the Curies detected such an element, which they called polonium after Marie Curie's native land. In December 1898 they detected another, which they called radium because of its intense radioactivity.
For their work on radioactivity, the Curies shared the Nobel Prize for physics with Becquerel in 1903. For the detection of polonium and radium, Marie Curie (her husband by then being dead) received the Nobel Prize for chemistry in 1911.
äPolarized Light
1808 A.D.
FRANCE
Bartholin's discovery that Iceland spar showed double refraction and produced two rays of light had never been properly explained.
In 1808 a French physicist, Étienne-Louis Malus (1775-1812), was playing idly with a crystal of Iceland spar and found that the sunlight reflected from a window produced only a single ray of light after passing through the crystal. What's more, as he turned the crystal, the ray of light faded and the other one appeared. When the crystal was at right angles to its original direction, only the other ray of light appeared, the first having disappeared.
Malus felt that light might have different poles, as magnets do, and that one beam of light had its poles at right angles to the other. He therefore called the rays polarized light, and the name stuck even though his theory was wrong.
Polarized light turned out to be enormously useful to chemists.
xPopulation Growth
1798 A.D.
ENGLAND
It seems obvious that population increases in times of peace, health, and prosperity and declines as a result of war, disease, and famine, but the first to try to analyze the matter dispassionately was a British economist, Thomas Robert Malthus (1766-1834). In 1798 he published a book, Essay on Population, in which he pointed out that population tended to increase in geometric progression (2, 4, 8, 16 . . .) while the food supply tended to increase in arithmetic progression (2, 3, 4, 5 . . .). As a result, population would always outstrip the food supply no matter what happened, and the surplus number of people would have to be stripped away by famine, war, and disease.
This imparted a certain inevitability to disaster and misery, which could only be removed by lowering the birthrate. In a second edition, Malthus suggested delayed marriage and sexual continence as a way of bringing this about. It doesn't take much of a cynic to realize that in the long run this won't work, but any suggestion that there are ways of lowering the birthrate without depriving people of the pleasures of sex is always met with strong disapproval on the part of some.
Malthus did not grasp the role technological advance could play in warding off disaster, even though he wrote at a time when the Industrial Revolution was in its early stages. Because of such advances, the world population is now five times what it was in Malthus's day and the Malthusian consequence has not yet been paid. But technological advance only delays, it does not stop, and the longer the delay, the more terrific the crash. Unless, of course, we lower the birth-rate.
╝Planetary Orbits
1609 A.D.
BERLIN, GERMANY
For nearly 2,000 years, since Plato, it had been taken for granted that planetary orbits were circles, if only because the circle was the simplest curve and therefore the most elegant and esthetic. Surely the heavens would not deal with anything else.
Planetary movements, however, did not match the notion of simple circular orbits, and the Greeks had to assume combinations of circles that grew more and more complicated as observations of actual planetary motions across the sky grew more precise.
Copernicus placed the Sun, rather than the Earth, at the center of the Universe, but kept circular orbits, which meant that there still had to be complicated combinations, although not quite as complicated as those required by the Greek system.
Tycho Brahe had carefully observed the position of Mars in the sky from night to night, making better measurements than anyone before him had done. His assistant during the last few years was a German astronomer, Johannes Kepler (1571-1630), and after Tycho's death in 1601, Kepler tried to work out an orbit that would best fit the data Tycho had gathered.
Kepler tried a number of things that didn't work and was finally driven to the all-but-unthinkable alternative of considering orbits that were not circles. Finally, he had his answer and, in 1609, published it in a book entitled Astronomia Nova (New Astronomy). In it, he maintained that planets moved about the Sun in ellipses (flattened circles whose geometric properties had first been explained by the Greek mathematician Apollonius in the first century B.C.). The Sun was located at one of the two foci of the ellipse, and with such orbits, no curve combinations were required. Our present picture of the Solar System (that is, the Sun plus its retinue of planets and other bodies) remains essentially that worked out by Kepler. No substantial change is expected in the future.
The elliptical orbit is Kepler's First Law of planetary motion. He also advanced a Second Law in his book, which described how the planetary speed altered with distance from the Sun. With the Sun at one focus of an ellipse, the planet was closer to the Sun (and moved faster) in one half of the orbit than in the other.
:Portland Cement
1824 A.D.
ENGLAND
The Romans used concrete for their structures, this being sand, gravel, or crushed rock held together by cement, a mixture of chemicals that hardened when water was added.
The first improvement on the Roman system came in 1824, when an English stonemason, Joseph Aspdin (1799-1855), invented a method for grinding and burning clay and limestone to produce a cement that was both cheaper and better than other cements in use at the time. He called it Portland cement in an attempt to emphasize its resemblance to Portland stone quarried at Portland, Dorset.
Discovering the Positron
1932 A.D.
PASADENA, CALIFORNIA
Dirac had predicted, from theoretical considerations, that there must be a particle just like the electron but with a positive charge rather than a negative one. However, such an antielectron had not been observed in nature.
The American physicist Carl David Anderson (b. 1905) was working with Millikan on cosmic rays. To carry out his studies, he had devised a cloud chamber with a lead partition running across it. A cosmic ray particle entering an ordinary cloud chamber was so energetic that a magnetic field scarcely managed to deflect it at all, and from the virtually straight- line trace that resulted, not much information about it could be derived. If a lead partition was placed in the chamber, the cosmic ray particle had energy enough to smash through it but lost enough energy in the process to allow it to be easily deflected on the far side of the partition.
In 1932, while conducting research with his lead-partitioned cloud chambers, Anderson noted tracks emerging from the lead that were clearly electron tracks (experienced researchers could read tracks at a glance). The only peculiarity was that the electron tracks curved in the wrong direction. Anderson had found the positively charged particle that Dirac had predicted -- the antielectron. Anderson, however, thought of it as a positive electron and gave it the shortened name of positron, which it has carried ever since.
For his discovery, Anderson was awarded the Nobel Prize for physics in 1936, sharing it with Hess, who had discovered cosmic rays.
tPraseodymium and Neodymium
1885 A.D.
AUSTRIA
Didymium was a rare earth element that had been discovered by Mosander some 40 years before. Its name is derived from the Greek word for "twin" because it was so like other rare earth elements. However, the name turned out to be more apt than was thought, for the element was actually twins, a mixture of two very similar elements.
In 1885, after much careful work, an Austrian chemist, Carl Auer, Freiherr von Welsbach (1858-1929), managed to separate the two elements. One he named praseodymium ("green twin," because of the color of a prominent line in its spectrum) and the other he named neodymium (new twin).
EGoldbach's Conjecture
1742 A.D.
RUSSIA
A mathematician who thinks some statement seems true but can't prove it's true may then advance it as a conjecture.
The most famous conjecture is one made by a German mathematician who worked in Russia, Christian Goldbach (1690-1764).
To explain it, we begin by saying that a prime number is any number greater than 1 that can only be divided by itself and 1. There are an infinite number of primes. The first few are 2, 3, 5, 7, 11, 13, 17, 19, and 23.
It seemed to Goldbach that any even number greater than 2 could be expressed as the sum of two primes (sometimes in more than one way). Thus, 4 = 2 + 2; 6 = 3 + 3; 8 = 5 + 3; 10 = 5 + 5; 12 = 7 + 5; 14 = 7 + 7; 16 = 11 + 5; 18 = 13 + 5; 20 = 13 + 7; 22 = 11 + 11; 24 = 13 + 11; 26 = 13 + 13; 28 = 23 + 5; 30 = 23 + 7; 32 = 19 + 13; 34 = 17 + 17; 36 = 23 + 13; 38 = 19 + 19; 40 = 23 + 17; 42 = 23 + 19; and so on.
No mathematician has ever found an even number higher than 2 that could not be expressed as the sum of two prime numbers. Every mathematician is convinced that no such number exists and that Goldbach's conjecture is true. However, no mathematician has ever been able to prove the conjecture.
But that sort of thing is the excitement of mathematics and of science generally. We shall never run out of problems, and some will always remain incredibly tantalizing.
╦Light's Many Colors
1666 A.D.
CAMBRIDGE, ENGLAND
The English scientist Isaac Newton (1642-1727), curious about light, conducted a series of crucial experiments in 1665 and 1666. He allowed a beam of light to pass through a prism (a triangular piece of glass) and then fall on a white wall.
What emerged was a band of colors, the least bent portion of the light being red, and then following, in order, orange, yellow, green, blue, and violet, each merging gradually into the next. Were the colors produced by the glass? No, for when Newton passed the light that had emerged from the prism through a second prism oriented in the opposite direction, all he got was white light. The colors had recombined. This meant that light had to be looked upon in a totally new way. It had always been assumed that white light was "pure" light and that color was introduced as an impurity through the effect of material substances on the light.
Newton's work made it clear that color was an inherent property of light and that white light was a mixture of different colors. Matter affected color only by absorbing some kinds of light and transmitting or reflecting others. Exactly what it was that made light assume different colors was not yet clear, however.
EProbability
1654 A.D.
FRANCE
People much given to gambling usually manage to work out rough-and- ready ways of measuring the likelihood of certain situations so as to know which way to bet their money, and how much. If they did not do this, they would quickly lose all their money to those who did.
A certain French gambler, Chevalier de Mere (1610-1685), was puzzled at the fact that he kept losing money in a certain game of dice, which he felt he ought to win. In 1654 he consulted French mathematician Blaise Pascal (1623-1662) on the matter, who in turn consulted another French mathematician, Pierre de Fermat (1601-1665). Pascal and Fermat worked out mathematical techniques for judging the likelihood of certain combinations appearing in the fall of (honest) dice. In doing so, they laid the foundations for the theory of probability.
The chief function of probability was to deal with large numbers of events, which singly were random in nature but in total were predictable. As time went on, considerations of probability proved to be almost inconceivably important in the development of science.
iPromethium
1945 A.D.
OAK RIDGE, TENNESSEE
By now, four elements beyond uranium had been discovered, but a single empty spot still remained in the periodic table below uranium. This belonged to element number 61, one of the lanthanides, Neptunium and Plutonium).
In 1945 a group under the direction of the American chemist Charles DuBois Coryell (b. 1912) discovered element number 61 among the fission products of uranium. Its most nearly stable isotope had a half-life of 17.7 years.
It was eventually named promethium, because just as the Greek god Prometheus had snatched fire from the nuclear furnace of the Sun, so promethium had been snatched from the nuclear furnace of the fissioning uranium atoms.
With the discovery of promethium, the periodic table had no further gaps, and all that remained was to discover further elements beyond the now-known curium (element number 96).
Dyes as Medicine
1932 A.D.
GERMANY
It had been a quarter-century since Ehrlich had found chemicals that attacked pathogenic microorganisms without damaging higher animals, and since then the matter had languished.
It was clear that possible chemicals for the purpose lay among the dyes.
Some dyes combined with cells and not with others, so surely there should be some dyes that combined with germs, killing them in the process, without affecting human cells.
The German biochemist Gerhard Domagk (1895-1964) conducted systematic tests of new dyes synthesized since the time of Ehrlich to see if he could find something appropriate. One of them was a newly synthesized orange-red compound with the trade name Prontosil. In 1932 Domagk found that injections of the dye had a powerful curative effect on streptococcus infection in mice.
As it happened, Domagk's young daughter, Hildegard, had been infected by streptococci following the prick of a needle. When other treatment failed, Domagk injected large quantities of Prontosil. She recovered, and the world had another item in its chemotherapeutic armory. Prontosil was the forerunner of a large number of drugs that would cause many infectious diseases to lose their terrors.
For this discovery, Domagk was awarded the Nobel Prize for medicine and physiology in 1939. (Hitler refused to allow Germans to accept Nobel Prizes, however, because a Peace Prize had been awarded to Carl von Ossietzky [1889-1938], an imprisoned German pacifist. Domagk was therefore not able to accept his prize formally till 1947.)
íProving General Relativity
1960 A.D.
GERMANY
The general theory of relativity, first advanced by Einstein, had been confirmed in three ways, all of them astronomic and all of them very borderline: (1) the advance of Mercury's perihelion, (2) the bending of light in a gravitational field, and (3) the reddening of light in a gravitational field.
Now, thanks to the Mössbauer effect, it was possible to test general relativity in the laboratory. Suppose a beam of monochromatic gamma rays were shot down a shaft from the top of a building to the bottom. The Earth's gravitational field would be very slightly stronger at the bottom of the building than at the top, since the bottom is nearer the Earth's center. This strengthening of the gravitational field would serve to increase the wavelength of the gamma rays, according to general relativity. The strengthening of the field and consequent increase in wavelength would be almost immeasurably small but large enough to cause the absorption of the gamma rays by a crystal at the bottom of the shaft to decrease considerably.
This experiment, when conducted in 1960, proved to support general relativity (as have all experiments and observations since that time).
eThe Screw Propeller
1827 A.D.
UNITED KINGDOM
Steamships were propelled by large paddlewheels on one side during the quarter- century of their existence. They worked well enough ordinarily, but in rough seas they could lift out of the water altogether if the ship listed to the other side, and that complicated steering. Furthermore, they were vulnerable to enemy fires so that it was considered completely impractical to power warships by steam.
In 1827, however, a British engineer, Robert Wilson (1803-1882), designed a screw propeller, which worked from the stern of the ship, so that it was symmetrically placed and was little affected by the ship's rolling. It was also well under water and so less vulnerable than the rest of the ship. Since it was judged to be a more efficient propulsion mechanism than the paddlewheel, it became possible to think of steam-powered warships thereafter.
«Prostaglandins
1935 A.D.
SWEDEN
In 1935 the Swedish physiologist Ulf Svante Von Euler (1905-1983) isolated a hormonelike substance from semen, which he took to represent a product of the prostate acting as a gland. He therefore called it prostaglandin.
Prostaglandin and related compounds referred to collectively as the prostaglandins have since been found in other tissues and have proved to have a wide variety of physiologic effects on the body.
╨Protactinium
1917 A.D.
GERMANY
Few of the new substances being detected as radioactive breakdown products of uranium and thorium were truly new elements. Once Soddy's isotope concept had been advanced, most of the new substances were recognized as isotopes of elements that were already known.
In 1917, however, the German physical chemist Otto Hahn (1879-1968) and a co-worker, Austrian physicist Lise Meitner (1878-1968), discovered a truly new element that disintegrated into actinium. They therefore named the new element protactinium (meaning "before actinium").
It turned out to be element number 91, one of the seven missing elements at the time Moseley had advanced his atomic number concept. That left only six elements to go.
æThe First Protein Discovery
1838 A.D.
THE NETHERLANDS
It sometimes happens that the chief contribution of a particular scientist is the invention of an important word. Thus the Dutch chemist Gerardus Johannes Mulder (1802-1880) worked on the chemical structure of albuminous substances, which seemed to consist of molecules more complex than those of carbohydrates or fats. He came to believe that such substances were made up of a basic building block of carbon, hydrogen, oxygen, and nitrogen, to which were added varying numbers of sulfur and phosphorus atoms.
In 1838 he gave this basic building block the name protein, from the Greek word for "first," since it seemed the foundation of substances that were of first importance to living tissue. Eventually the word came to be used for the substances generally, and to this day, protein is what we call one of the two types of substances that are indeed of first importance to living tissue.
JProtoplasm
1846 A.D.
GERMANY
A German botanist, Hugo von Mohl (1805-1872), studied plant cells assiduously. He found that the typical plant cell had a watery sap in the center, which showed no signs of life, and a granular colloidal layer rimming the cell, which did show such signs. In 1846 Mohl called this granular colloidal material protoplasm.
The word had been used earlier in another connection. The Czech physiologist Jan Evangelista Purkyine (1787-1869) had applied the word to the speck of living embryonic material in the egg, which was immersed in nonliving yolk that acted as its initial food supply. Protoplasm is from Greek words meaning "first formed," and thus referred to the living part of the egg as the first-formed part of the organism.
However, it was Mohl's more general use that caused the word to enter the scientific vocabulary.
ÆUnderstanding the Atom
1914 A.D.
SCOTLAND
Thomson felt that positive rays consisted of streams of high-velocity atomic nuclei. Rutherford studied them and came to the conclusion, in 1914, that the positive rays involving hydrogen nuclei were the smallest of all and that no smaller positively charged particles existed. He therefore called the hydrogen nucleus a proton (from the Greek word for "first").
The proton is not the positive analog of the electron, however, even though the size of their electric charge is precisely the same. The proton is a much more massive particle (now known in fact to be 1836.11 times as massive as the electron).
After Rutherford had made his suggestion, it seemed that the massive nucleus at the center of the atom must be made up of protons. (This meant that Prout's hypothesis that all elements were made up of hydrogen was in a manner of speaking correct.)
Of course it didn't make too much sense that the atomic nucleus should consist of protons. After all, the protons, being positively charged, would repel each other. The natural suggestion, then, was that electrons were also present in the nucleus and that their negative charges acted as a kind of cement. This seemed all the more logical since radioactive changes caused atoms to eject electrons in the form of beta particles, and these seemed to come from the nucleus.
Furthermore, only in hydrogen were the mass and charge of the nucleus equal. Thus an alpha particle (a helium nucleus) had four times the mass of a proton but a positive charge only twice that of a proton. It seemed logical to explain this by supposing that an alpha particle consisted of four protons plus two electrons. The electrons neutralized the charge of two of the protons without affecting the mass much. The remaining two positive charges on the nucleus were neutralized by the two planetary electrons circling outside the nucleus.
It seemed, then, that all atoms were made up of equal numbers of protons and electrons, with some of the electrons inside the nucleus and some circling around it.
This picture of the atom seemed simple and satisfactory but proved quite wrong, although the matter wasn't straightened out for 16 years.
╫The Nucleus
1932 A.D.
GERMANY
As soon as the neutron was discovered by Chadwick, Heisenberg pointed out that the atomic nucleus must be made up of protons and neutrons rather than protons and electrons.
Thus the nitrogen nucleus with a charge of +7 must contain seven protons.
Since it had a mass of 14, it must also contain seven neutrons. That would mean 14 particles altogether, and 14 particles, each with with a spin of + or -, would add up to a total spin that was an integer no matter how you distributed the pluses and minuses. Given a proton-neutron nucleus, all nuclear spins turned out to match what was expected, and all spin anomalies disappeared.
What's more, the proton-neutron picture clearly explained the existence of isotopes. The nuclei of all atoms of oxygen, for instance, must contain eight protons, but the common oxygen-16 nucleus must contain eight protons and eight neutrons, the oxygen-17 nucleus eight protons and nine neutrons, and the oxygen- 18 nucleus eight protons and ten neutrons. In the case of hydrogen, the hydrogen-1 nucleus must contain a proton only, with the hydrogen-2 nucleus containing one proton and one neutron.
This new view of the nucleus solved the spin problem but introduced a new problem of its own. If the tiny nucleus were filled with protons, all of which were positively charged, there must be an intense repulsion among them. The neutrons, being uncharged, would do nothing to reduce the repulsion. How then account for the fact that the nucleus clings together strongly? (As long as it was thought that electrons existed in the nucleus, they might be viewed as a kind of cement, but that possibility was now gone.) Heisenberg suggested that exchange forces might exist. In other words, the proton and neutron might exchange particles in such a way that a strong attraction would be produced, since the particles could not be exchanged unless the proton and neutron remained very close together. It took a few years for this notion to be properly developed.
4Psychoanalysis
1893 A.D.
AUSTRIA
Breuer had started to use hypnotism in the treatment of mental diseases such as hysteria. The method had later been taken up by Freud, but he eventually abandoned hypnotism for free association, allowing the patient to talk randomly and at will with a minimum of guidance. In this fashion, the patient was gradually put off guard, and matters came to be revealed that in ordinary circumstances would have been kept secret from the patient's conscious mind.
The advantage of this method over hypnotism was that the patient was aware of what was going on at all times and did not have to be informed afterward of what had been said.
In 1893 Freud and Breuer published The Psychic Mechanism of Hysterical Phenomena. This is considered to have laid the foundations of the medical technique of psychoanalysis.
Founding Paleontology
1812 A.D.
PARIS, FRANCE
French anatomist Georges Cuvier (1769-1832) found important and interesting fossils. In 1812 he reported the fossil remains of a creature that clearly must have had wings and been able to fly but whose skeleton showed it to have been a reptile. It was named pterodactyl, from Greek words meaning "wing-finger," because the membrane of its wing was stretched out along one elongated finger.
Cuvier could see that fossils represented creatures that were extinct and that the deeper the stratum and the older the remains, the less the fossils resembled modern organisms. Nevertheless, he couldn't accept the idea of evolution.
Instead, in a book entitled Inquiry into Fossil Remains, published in 1812, he advanced the notion that there had been numerous creations, each one ended totally by some catastrophe and followed by a new creation of life closer to that of the present.
This view, called catastrophism, is usually considered the opposite of James Hutton's uniformitarianism, and for a long time the two were considered mutually exclusive. However, it is quite possible that Earth's history shows periods of uniformitarianism interspersed by episodes of catastrophism (though none of the catastrophes, so far, seem to have been complete).
Cuvier was the first to go into detail on the appearances of ancient forms of life, and he attempted to classify them, as far as possible, by using the same system used for living species. In this way, he is considered to have founded paleontology, the study of ancient extinct forms of life.
∙Doctors Spreading Disease
1847 A.D.
AUSTRIA
It had long been understood that some diseases were contagious, although no one knew exactly what caused the contagion.
In the case of puerperal fever (from Latin words meaning "childbearing," and more familiarly known as childbed fever), there were suspicious signs of a certain type of contagion. A woman giving birth who was treated by a doctor who was also treating other child-bearing women was much more likely to get the disease than a woman treated by a midwife who was not treating anyone else.
Some grew suspicious that doctors were somehow carrying the disease from patient to patient. The patients, being in a weakened condition and often bleeding, were much more susceptible than the doctor, who generally escaped infection. In the United States, Holmes took this attitude and published his opinions, but was paid little heed.
In Vienna, a Hungarian physician, Ignaz Phillipp Semmelweiss (1818-1865), thought so, too, and when he gained control of a hospital in 1847, he began to force the doctors to wash their hands in a solution of calcium chloride before touching patients. This was unpleasant for the doctors, of course, especially those older ones who were proud of the "hospital odor" of their hands.
The incidence of puerperal fever went down drastically following Semmelweiss's ruling, but this did not impress the rebellious doctors. When Hungary revolted against Austria in 1849, the Austrian doctors used Semmelweiss's Hungarian origins as a way of forcing him out. The hand-washing stopped and the incidence of puerperal fever went up again at once -- which didn't disturb the doctors.
It was not until the cause of infection was finally understood, some 20 years later, that doctors began to reconcile themselves to washing their hands.
<Discovering Pulsars
1967 A.D.
ENGLAND
For some years there had been indications of radio sources in the sky that changed intensity after brief intervals, but radio telescopes at that time were not designed to catch such brief "twinkles." Then, in Great Britain, the British astronomer Anthony Hewish (b. 1924) supervised the construction of a device with 2,048 separate receivers spread out in an array that covered an area of nearly 3 acres. This was designed to detect brief changes in microwave intensities.
In July 1967 the array was put to work, and within a month a graduate student, Jocelyn Bell, had detected bursts of microwaves from a place midway between Vega and Altair. The bursts were astonishingly brief, lasting only a thirtieth of a second. Even more astonishing, they followed one another with remarkable regularity -- at intervals that were finally measured as 1.33730109 seconds.
This object was eventually called a pulsating star, a phrase quickly abbreviated to pulsar.
Eventually hundreds of pulsars were located. Hewish was awarded a share of the Nobel Prize for physics in 1974.
├Purines and Pyrimidines
1885 A.D.
GERMANY
Since the nucleic acids had been discovered by Miescher, little had been done to determine their molecular structure.
Then the German biochemist Albrecht Kossel (1853-1927) took up the matter. He got rid of the proteins associated with the nucleic acids and worked on the material itself. By 1885 he had obtained substances from it that included the double-ring purines Emil Fischer had studied a few years earlier.
He also obtained pyrimidines, whose molecules were made up of a single ring of atoms, four carbons and two nitrogens.
He isolated two different purines, adenine and guanine, and three different pyrimidines, uracil, cytosine, and thymine. He also decided that a sugar molecule was present but couldn't tell which one.
Much remained to be done, but it was a good start and far more important than anyone could tell at the time. This was some of the work for which Kossel received a Nobel Prize in physiology and medicine in 1910.
■ Stone Monuments
2650 B.C.
GIZA, EGYPT
Thanks to the Nile, the Egyptians were able to grow a surplus of food so that many could devote themselves, for at least part of the year, to other tasks. That meant that the Egyptian rulers could put the Egyptian people to work on public projects designed to show the greatness of their rulers and, through them, of the nation and the people. The projects would also serve as memorials to that greatness to future generations.
Thus the Egyptian rulers built elaborate houses (or palaces, as we now call them). Indeed, the ruler was referred to as pharaoh, which is the Greek version of an Egyptian word meaning "big house." (This is similar to our present habit of saying "the White House" when we mean the president.) It was customary for the important citizens of the nation to build themselves elaborate burial tombs, since Egyptian religion dealt in detail with life after death, and it was felt that, to insure immortality, the body had to be preserved. The tombs were oblong objects called mastabas. (Nowadays, to insure the immortality of our presidents, we build colossal presidential libraries.)
In about 2686 B.C., when Djoser, the second king of the Third Dynasty came to power, he decided to build a particularly elaborate tomb as a memorial to his greatness. He had a counselor named Imhotep who supervised the building of six mastabas of stone, one on top of the other, each smaller than the one below. The result was basically pyramidal in shape, but it was set back periodically as modern skyscrapers sometimes are. Because these setbacks were like steps a giant would use in climbing to the top, the structure is called the Step Pyramid. The base is an oblong about 400 feet by 350 feet, and the top is almost 200 feet high.
The Step Pyramid was the first large stone structure ever built and is the oldest structure built by humans that remains substantially intact today. The Step Pyramid set a fashion, and for a couple of centuries afterward the pharaohs kept the people busy in their spare time building more and more elaborate pyramids. Larger and larger stones were used, and the climax came when the Pharaoh Khufu (Cheops to the Greeks) supervised construction of the Great Pyramid, the largest of all, in about 2530 B.C.
When that pyramid was finished, its square base was 755 feet on each side, so that it covered an area of 13 acres. The four sides sloped upward evenly (for the notion of steps had been abandoned) to a point 481 feet high. It was solidly composed of slabs of rock -- 2,300,000 of them, it is estimated, with an average weight of 2-1/2 tons apiece. Each had to be brought some 600 miles, by water, of course, from quarries far up the Nile.
In among these rocky slabs were passages leading to a chamber near the center of the huge pile, which was to contain the king's coffin, his mummy, and his treasures after his death.
The fad for such large, vainglorious structures did not persist for long. They took too much time and too much work even for Egypt. The urge to build big objects, some useful, some symbolic, some vainglorious, has never left humanity, however. Some of the medieval cathedrals finally surpassed the pyramids in height (after 3,500 years or so) and today, of course, we have our skyscrapers, our huge bridges and dams, and so on.
ÉThe First Synthetic Plastic
1855 A.D.
ENGLAND
In 1855 a British chemist, Alexander Parkes (1813- 1890), found that pyroxylin (a partly nitrated cellulose), if dissolved in alcohol and ether in which camphor had also been dissolved, would produce a hard solid upon evaporation, which would soften and become malleable when heated. He found no way of doing anything commercial with it, but he had discovered the first synthetic plastic.
▌Irrational Numbers
520 B.C.
SAMOS, GREECE
The Greek philosopher Pythagoras (ca. 580-ca. 500 B.C.) believed that whole numbers, including fractions, since they are ratios of whole numbers, were the basis of the Universe. Thus, 3/4 is the ratio of 3 to 4. If you begin with 3 pies and divide them equally among 4 people, each person gets 3/4 of a pie. Whole numbers and fractions together make up the rational numbers (those that can be expressed as ratios), and it is easy to suppose that rational numbers are all that exist.
However, suppose you have a right triangle with each side equal to 1 unit. What is the length of the hypotenuse? The answer can be obtained by remembering that the square of the hypotenuse is equal to the sum of the squares of the sides. This was long known, but Pythagoras worked out a good proof and it is called the Pythagorean theorem as a result.
The square of each side is 1, so the square of the hypotenuse is 2, and the length of the hypotenuse is the square root of 2, or that number which, when multiplied by itself, equals 2. The number 7/5 is nearly right, since 7/5 x 7/5 = 2.04. The number 707/500 is even closer, since 707/500 x 707/500 is a little over 1.999.
It can be shown quite easily, just the same, that there is no fraction, no fraction at all, however complicated, that when multiplied by itself gives exactly 2. The square root of 2 is therefore not a rational number. It is an irrational number, and as it turns out, there are an infinite number of such irrationals.
ÜQuantum Electrodynamics
1948 A.D.
ITHACA, NEW YORK
Making use of quantum theory, the American physicist Richard Phillips Feynman (1918-1988), in 1948, worked out equations governing the behavior of electrons and electromagnetic interactions generally; equations that allowed predictions of such phenomena to be made with far greater precision than had been possible until then.
This theory was called quantum electrodynamics, and it proved so successful that it has been used as a model for the attempted working out of equations governing the behavior of particles subjected to the weak and strong interactions.
For this work, Feynman received a share of the Nobel Prize for physics in 1965.
εQuantum Chromodynamics
1972 A.D.
PASADENA, CALIFORNIA
By now it was well established that quarks combine two at a time (a quark and an antiquark) to form mesons and three at a time to form protons, neutrons, and other hadrons.
Murray Gell-Mann, who had originated the quark concept, labored to work out the rules governing the combination of quarks. He suggested that each quark came in three colors: red, blue, and green. (These colors are not to be taken literally but as an analogy.) Just as in the case of light, a red, a blue, and a green quark will combine to give a lack of color property (white). Only those combinations yielding white can exist.
In this way, Gell-Mann founded the study of quantum chromodynamics, on the model of quantum electrodynamics, which had proved to work so well.
Quarks, however, are much more complicated in their behavior in connection with the strong interaction than electrons are in connection with the electromagnetic interaction, and quantum chromodynamics is still being tinkered with.
èVastly Distant Radio Sources
1963 A.D.
U.S.A.
Among the radio sources located in the sky during the 1950s were a few that seemed confined to very small areas. These compact sources were known as 3C48, 3C147, 3C196, 3C273, and 3C286. The 3C is short for Third Cambridge Catalog of Radio Stars, a listing compiled by the British astronomer Martin Ryle (1918-1984).
In 1960 these sources were pinpointed, by such men as the American astronomer Allan Rex Sandage (b. 1926) and the Australian astronomer Cyril Hazard, and found to originate in certain objects that looked like dim stars. It seemed strange that dim stars would be such strong radio sources, and the feeling arose that they might be something other than stars. They were referred to eventually as quasistellar radio sources, where quasistellar means "starlike," and this was eventually shortened to quasars.
The spectra of quasars proved puzzling; the lines could not be identified. In 1963, however, the Dutch-born American astronomer Maarten Schmidt (b. 1929) realized that the lines could be identified if they were viewed as lines that would ordinarily be in the ultraviolet but had been displaced by means of an enormous red-shift.
Such a red-shift would mean that the quasars were enormously distant, over a billion light-years away, and the fact that they could be seen at all at such a distance meant they were unusual indeed. It was finally decided that they were galaxies with extremely active centers (like particularly large Seyfert galaxies -- see 1943). At their distances, only the centers could be seen, so that they had a starlike appearance. Some quasars have been detected that appear to be over 12 billion light-years away.
╖Quaternions
1843 A.D.
IRELAND
The discovery of non-Euclidean geometries taught mathematicians that there were no absolute truths but that many alternative mathematics could exist depending on the nature of the axioms chosen. In other words, more than one set of axioms could give rise to self-consistent and useful consequences. This was so in geometry, and the Irish mathematician William Rowan Hamilton (1805-1865) showed that it was true in algebra as well.
Gauss had shown that complex numbers could be treated as though they were points on a plane, and that each could be represented by two numbers. Hamilton tried to deal with hypercomplex numbers that could be presented as points in three or more dimensions. He tried to work out a system of dealing with such points and found he could not. Then, in 1843, the thought came to him that he could do so if he were willing to abandon the commutative law of multiplication.
It had always been taken as self-evident that A x B = B x A, but if this was abandoned, Hamilton found he could devise a self-consistent algebra of hypercomplex numbers, or as he called them, quaternions (from the Latin word for "four," because each of Hamilton's points involved four numbers).
ÖCoping with Malaria
1641 A.D.
CENTRAL AMERICA
The Incas had used the bark of the cinchona tree as a treatment for malaria. The active ingredient in it eventually came to be known as quinine. The first knowledge of quinine reached Europe in 1642, and for three centuries it remained the only treatment for this common and debilitating disease. Without quinine, it is doubtful if Europeans could have long remained in tropical climates.
├Fighting Malaria
1932 A.D.
GERMANY
Malaria, a widespread disease in the tropics and perhaps the most debilitating disease, on the whole, that was suffered by the human species, had been treated with quinine for three centuries. Quinine comes from the bark of a tropical tree, however, and the supply to the industrial nations might easily be cut off in wartime. The search was on for a substitute.
The first satisfactory substitute to be found was quinacrine (also called Atabrin), first developed in Germany and established as a successful antimalarial in 1932. When not too many years afterward, war did indeed disrupt the quinine supply, the existence of quinacrine made it possible for troops to operate in tropical regions.
wQuintic Equations
1824 A.D.
NORWAY
General solutions by algebraic methods had been found for the equations of the third degree (cubic equations) and the fourth degree (quartic equations) -- see 1535 and 1545. Ever since, mathematicians had been struggling to find a general solution for equations of the fifth degree (quintic equations), those that involved an x;s5.
They had failed, and in 1824 the Norwegian mathematician Niels Henrik Abel (1802-1829) was able to demonstrate that a general algebraic solution of the quintic equation was impossible. Just as Gauss had shown impossibility in geometry, so Abel was able to show impossibility in algebra.
╣Fighting Rabies
1885 A.D.
FRANCE
Rabies, or hydrophobia, is a severe disease of the central nervous system. It can occur in any warm-blooded animal. The microorganism that causes it can be present in the salivary glands and may be communicated by a bite. For human beings, dogs can be particularly dangerous. They become excitable and vicious ("mad dogs") when they have the disease, and bite at the slightest cause, or for no cause at all.
Once infected, it may take quite a while for a human being to show symptoms, because the microorganism has to penetrate the nervous system, but once it is established there, death is fairly quick, almost certain, and agonizing.
Pasteur tried to treat the disease as he had treated anthrax, by developing an attenuated and feeble preparation of the causative agent that would give immunity but not the disease. He showed that an attenuated agent could be obtained by passing a rabies infection through a variety of different species of animals until its virulence had abated.
In 1885 Pasteur made the first use of his attenuated preparation to prevent a case of rabies in a boy, Joseph Meister (1878-1940), who had been bitten by a mad dog. The treatment worked, and the boy was saved.
├Inventing the Radio Antenna
1895 A.D.
U.S.A.
Once Hertz had demonstrated the existence of radio waves, the possibility of using such waves in signaling across long distances occurred to a number of people. If one could use such radiation for the purpose, one could do away with total dependence on telegraph wires and cables. Indeed, the British call communications by radio waves wireless telegraphy or for short wireless. Americans call it radiotelegraphy or for short radio.
Of course, to make such communication possible, one needs a far better detector than the simple loop Hertz used. In 1890 a French physicist, Édouard- Eugène Branly (1844-1940), invented a detector that consisted of a container of loosely packed metal filings. It ordinarily conducted little current, but it conducted quite a bit when radio waves fell upon it. Using this detector, Branly could detect radio waves 150 yards from the source.
The British physicist Oliver Joseph Lodge (1851-1940) improved the device in 1894, called it a coherer, and used it to detect radio waves half a mile from the source. He also sent out the radio waves in dots and dashes so that he could transmit and pick up a message in Morse code.
In 1895 two men made a particularly crucial discovery. They found that a long vertical wire attached to the source, and another attached to the receiver, made the signals much stronger and easier to detect. The long wires were called antennas, because they seemed to resemble the long feelers that insects wear on their heads.
One of the discoverers was a Russian physicist, Aleksandr Stepanovich Popov (1859-1905), the other an Italian electrical engineer, Guglielmo Marconi (1874-1937). It was these antennas that really made radio communication possible.
The Distance to Venus
1961 A.D.
GOLDSTONE TRACKING STATION (BARSTOW, CALIFORNIA)
Fifteen years ago, microwaves had been reflected from the Moon. That had been comparatively easy. By 1961 the technique had advanced to the point where microwaves could be sent out to Venus, a hundred times as far away as the Moon. This was done, and reflections were received by five different groups, one Soviet, one British, and three American.
The microwaves traveled through space at the speed of light, and from the time measured between the emission of the original beam and the detection of the reflection, the distance of Venus and therefore the general scale of the Solar System could be determined much more accurately than had been possible from observations of the asteroid Eros.
It took a long time for our knowledge of Venus to advance to this point. Initially the Greeks, from whom we get so much knowledge, were not as advanced in astronomy as the Babylonians were. They knew the evening star, a bright planet that appeared in the western sky after sunset, and they called it Hesperos (the Greek word for "evening"). There was also a morning star, a bright planet that appeared in the eastern sky before sunrise, and they called it Phosphoros (the Greek word for "light-bring-er," because once it appeared, the Sun was not far behind).
In 520 B.C. Pythagoras (ca. 580-ca. 500) was the first Greek to realize the two were the same object, since when the evening star was in the sky there was no morning star and vice versa. (He is supposed to have traveled in Babylonia, and he may have learned this there.) About 500 B.C., he named this single planet, which swung from one side of the Sun to the other and back again, Aphrodite, after the Greek goddess of love and beauty. The Romans (and we) called it by their equivalent, Venus.
╒Radio Waves From Hydrogen
1944 A.D.
THE NETHERLANDS
In German-occupied Europe, scientific work could proceed only with extreme difficulty. The Dutch astronomer Hendrik Christoffel van de Hulst (b. 1918) was forced to do what work he could with theoretical notions that required no more in the way of instrumentation than pen and paper.
He considered the behavior of cold hydrogen atoms and worked out how the magnetic fields associated with the proton and the electron in the hydrogen atom were oriented to each other. They could line up in the same direction or in opposite directions. Every once in a while a particular atom could flip from one configuration to another, and in so doing, it would emit a radio wave 21 centimeters in length.
Any single hydrogen atom ought to do this only once in 11 million years or so on the average, but there were so many such atoms in space that a continuing drizzle of 21-centimeter radiation should be emitted, a drizzle that might be intense enough to be detectable.
Jansky's discovery had shown that radio waves were emitted by objects in the sky, but beyond Reber's simple radio telescope there was nothing with which to observe such radio waves in any detail. Van de Hulst's calculations had to wait for corroboration.
/Radio Telescope
1937 A.D.
U.S.A.
Radio waves from outer space had been detected by Jansky, but nothing had been done about it because the devices necessary for detecting and analyzing the radiation were not yet in existence.
In 1937, however, an American radio engineer, Grote Reber (b. 1911), built the first radio telescope in his back yard. It was a parabolic reflector 31 feet in diameter, and the radio waves he received could be reflected to a focus so that their intensity could be measured.
In this way, Reber discovered points in the sky that emitted radio waves more strongly than did the general background, and he was the first to prepare a radio map of the sky. Naturally, Reber's work was primitive compared to what was to come in succeeding decades, but for several years he was the only radio astronomer in the world.
Radio Waves
1888 A.D.
GERMANY
In 1887, when German physicist Heinrich Rudolph Hertz (1857-1894) was performing the experiments that gave him the first glimpse of a photoelectric effect, he expected that the oscillating current he was working with would produce an electromagnetic wave. Each oscillation should produce a wave, and the wave should be very long. After all, since light travels at a bit over 186,000 miles per second, a wavelength formed in an oscillation of a mere hundred-thousandth of a second will still be nearly 2 miles long. In 1888, he actually observed such waves.
Hertz used, as a device for detecting the possible presence of such long-wave radiation, a simple loop of wire, with a small air gap at one point. Just as the current in his first coil gave rise to radiation, so the radiation produced ought to give rise to a current in the second coil. Sure enough, Hertz was able to detect small sparks jumping across the gap in his detector coil.
By moving his detector coil to various parts of the room, Hertz could tell the shape of the waves by the intensity of the spark formation and could calculate a wavelength of 2.2 feet. This is a million times the size of a wavelength of ordinary light. He also managed to show that the waves were electromagnetic in nature. At first these long-wave radiations were called Hertzian waves, but later the name radio waves came into use instead.
In this way, Hertz verified the usefulness of Maxwell's equations and showed that light was only a tiny section of the electromagnetic spectrum.
}Radio Waves and Sound
1906 A.D.
MASSACHUSETTS
Radio communication first came into use only as a wireless telegraph, forming the dots and dashes of the Morse code in appropriate bursts of radio waves.
It occurred to the Canadian-born American physicist Reginald Aubrey Fessenden (1866-1932) to send out a continuous signal with an amplitude (the height of the waves) varying in such a way as to follow the irregularities of sound waves. The radio wave was said to have amplitude modulation (AM) imposed on it.
At the receiving end, the modulation could be reconverted into sound waves, with the result that you could use a radio for speaking and hearing thanks to modulated radio waves the same way you could use a telephone for speaking and hearing thanks to modulated electric currents.
On December 24, 1906, the first such message was sent out from the Massachusetts coast, and wireless receivers picked up music.
QDiscovering Radon
1900 A.D.
GERMANY
A German physicist, Friedrich Ernst Dorn (1848-1916), studying the radium that Curie had discovered, found in 1900 that it gave off not only radiations but a gas that was itself radioactive. The gas was called radium emanation at first, but on closer study it turned out to be a noble gas, the sixth one, and was named radon.
èRemote Sensing With Radar
1935 A.D.
SCOTLAND
To send out a beam of light and record the time it took to be reflected back across a given distance had first been used to determine the speed of light by Fizeau. Once the speed of light was determined with good accuracy, the time it took for a beam of light to strike an object and return could be made to yield both the direction and the distance of the reflecting object. Such a scheme, making use of ultrasonic sound, had been used by Langevin in devising sonar.
The use of light for such a purpose is impractical, because light is too easily stopped by obstacles and too easily absorbed and scattered by mist, dust, and fog. Radio waves are much more penetrating, but those most commonly used in communication are so long that they bend around obstacles rather than being reflected. However, if the shortest radio waves (microwaves) are used, they are reflected by moderately sizable objects and are sufficiently penetrating to pass through cloud and fog.
The Scottish physicist Robert Alexander Watson-Watt (1892-1973) worked on devices for the emission of microwaves and for the detection of the reflected beam. By 1935 he could use his device to follow the path of an airplane by the microwave reflections it sent back.
The system was called radio detection and ranging, abbreviated to ra. d. a. r., or radar. This development was to prove of life- and-death importance in just a few years.
_Moving Over Water
6000 B.C.
EURASIA
Human beings could not avoid bodies of water, especially since fresh water was needed for drinking. They would cluster near rivers and lakes for that purpose.
Water would offer them a source of food, too, and they would venture out into it to catch fish. People would learn to swim. In addition, they could not help but notice that wood floats. By 6000 B.C., they must have learned how to lash logs together to form rafts that would keep them out on the surface of quiet bodies of water for a time. By paddling with their hands, if nothing else, they could even cross small stretches of water.
wRayon: The First Synthetic
1883 A.D.
FRANCE
The French chemist Louis-Marie-Hilaire Bernigaud de Chardonnet (1839-1924) had begun some five years earlier to produce fibers by forcing solutions of nitrocellulose through tiny holes and allowing the solvent to evaporate. He perfected the process in 1883 and found he had a fiber that strongly resembled silk in its fineness and shininess. He called it rayon (from the French word for "a ray of light") because of its shininess. He used only partly nitrated cellulose, so rayon wasn't explosive, but it was still uncomfortably flammable.
Rayon was the first synthetic fiber, and it was to be followed by many others.
ùBlood Circulation
1733 A.D.
ENGLAND
English physiologist Stephen Hales (1677-1761) had studied the flow of sap in plants and went on to study the flow of blood in animals, measuring the rate of flow in different portions of the circulatory system. Most important of all, he was the first person to measure blood pressure, albeit in a crude way. He described his work in this field in a book entitled Hemostaticks, published in 1733.
xFission Reactors
1942 A.D.
CHICAGO, ILLINOIS
Even before the first fission bomb had been exploded, a controlled nuclear reactor (although a very inefficient one) had been set up in Chicago in 1942. Its only function was to show that a fission bomb was possible.
Efforts were later made, however, to devise nuclear reactors efficient enough to serve as reasonable sources of controlled energy for peaceful uses. The fissioning uranium or plutonium would liberate heat at a moderate rate, and this heat would turn water into steam, which would turn a turbine and produce electricity.
Naturally, methods had to be devised to slow the fission reaction if it showed signs of proceeding too quickly and producing enough heat to result in a meltdown. A controlled nuclear reactor could not explode, since it was not enclosed strongly enough to build up the kind of heat and force that would lead to an explosion. It would, however, be capable of releasing a surge of nuclear radiation into the environment, so the pressure for safe operation was therefore strong.
The first nuclear reactor built to produce electric power for civilian use was put into action in the Soviet Union in June 1954. It was a very small one. Larger reactors were produced in Great Britain and in the United States soon after, and eventually they were distributed around the globe and began to contribute substantially to the world's energy supply, particularly in France and the Soviet Union.
Controlled reactors also came into use in another way. Submarines throughout both world wars had remained vulnerable because they had to surface periodically to recharge their batteries. Under the driving force of the Polish-born American naval officer Hyman George Rickover (1900-1986), a plan developed to equip American submarines with atomic reactors, which would require no recharging and could keep a submarine submerged for months at a time. The first nuclear-powered submarine, the Nautilus, was launched in January 1954.
Some nuclear-powered surface vessels were eventually built by the Soviet Union and the United States, but except for submarines, nuclear-powered forms of transportation did not catch on.
φThe Mechanical Reaper
1834 A.D.
CHICAGO, ILLINOIS
Agriculture had always been a labor-intensive occupation, particularly at harvest time, when there was often a shortage of hands to reap and gather the grain.
Attempts were therefore made to devise a mechanical reaper, and the one that finally proved successful was built by an American inventor, Cyrus Hall McCormick (1809-1884). He first built what came to be called the McCormick reaper in 1831, and he secured a patent for it in 1834. It wasn't immediately successful, but McCormick pushed it with great pertinacity, and little by little, it took hold, particularly in the vast grain fields of the American Midwest.
This began a whole series of mechanical inventions that gradually reduced the number of laborers that had to work the land to produce food, until finally, in a thoroughly industrialized nation such as the United States, a work force of 4 percent of the whole suffices to grow food for itself and for the remaining 96 percent, with enough left over to export.
▄Receding Galaxies
1929 A.D.
U.S.A.
Slipher had measured the radial velocity of the Andromeda nebula even before it had been found to be an independent galaxy. After that he measured the radial velocity of other galaxies and found that all but two were receding from us.
The American astronomer Milton La Salle Humason (1891-1972) continued these labors, working with Hubble, who had first proved the Andromeda to be an independent galaxy. Humason measured the radial velocity of many more galaxies and also found that all were receding from us, some at unusually large rates.
Hubble went over all the work carefully and used various methods for estimating the distances of the various galaxies. By 1929 he felt sufficiently confident of his conclusions to announce them. Galaxies, he maintained, receded from us at a rate proportional to their distance from us (Hubble's law).
What is so important about our Galaxy that all the others (except for two of the very closest) should be receding from us, and why should those farther off be receding more quickly than those nearer? The explanation that seemed most logical was that the Universe was expanding in accordance with the suggestion of Friedmann, so that the galaxies (or clusters of galaxies) were all receding from each other, and not merely from us. An observer in any galaxy would see the other galaxies receding at a rate proportional to their distance.
With Hubble, then, the expanding Universe ceased being a matter of theory and became an observed fact.
╝Recombinant DNA
1970 A.D.
BALTIMORE, MARYLAND
In 1970 the American microbiologists Hamilton Othanel Smith (b. 1931) and Daniel Nathans (b. 1928) discovered an enzyme that could cut a molecule of DNA at certain specific sites. The resulting DNA fragments were still large enough to contain genetic information, and this work led to the formation of fragments that could recombine with each other to form new genes that did not exist in nature.
This technique of recombinant DNA became an important tool for geneticists and was a long step toward genetic engineering, in which genes could be modified, transferred, or designed.
For this work, Nathans and Smith shared the Nobel Prize for physiology and medicine in 1978.
Red Blood Corpuscles
1658 A.D.
THE NETHERLANDS
Microscopes of sorts had been in existence for half a century, but they had not been very good. They magnified but slightly and were usually not perfectly in focus. It was not till the 1650s that microscopes improved in quality to the point where they were useful in studying the minutiae of living things.
The Dutch naturalist Jan Swammerdam (1637-1680) studied insects under the microscope and collected some 3,000 species of them, so that he is considered the father of modern entomology.
Swammerdam's most famous discovery, however, made in 1658, was the red blood corpuscle. Present in the bloodstream in the billions, red blood corpuscles carry the chemical that absorbs oxygen from the air in the lungs, though this was not known till much later.
JJupiter's Great Red Spot
1664 A.D.
LONDON, ENGLAND
In 1664 English physicist Robert Hooke (1635-1701) noted a large oval marking on Jupiter that came to be called the Great Red Spot. The name was accurate, for it did seem to be red in color and it was great in the sense of being very large. The entire Earth could be dropped into it without touching its sides.
┐Reflecting Telescopes
1668 A.D.
UNITED KINGDOM
During the first 60 years of the telescope's use, its lenses curved light by refraction and focused it. In this way, the eye saw the image as brightened and expanded. Such telescopes were refracting telescopes.
Unfortunately, the lenses refracted different colors of light differently and formed a spectrum, so that the images in such telescopes were always blurred by colored rings, red or blue (chromatic aberration). This was minimized by using only the center of the lens and having the light come together only gradually and reach a focus at a considerable distance from the lens, but this meant that telescopes capable of considerable brightening and enlargement had to be long and unwieldy.
English scientist Isaac Newton (1642-1727), through his experiments with light, supposed that one couldn't possibly have a lens without blurring the image with color. He therefore thought of an alternative. Why not use curved mirrors instead of curved lenses, and focus the light by reflection rather than refraction?
Reflection did not produce a spectrum. In 1668, therefore, he built the first reflecting telescope, and thereafter two varieties of telescope were available to astronomers.
Studying How Light Bends
1621 A.D.
THE NETHERLANDS
The action of lenses had been known from ancient times. Archimedes, according to a doubtful story, used large lenses to focus sunlight and set the Roman ships afire when they were besieging Syracuse.
Obviously, light had to be bent in passing through them. The first to make a mathematical study of this was a Dutch mathematician, Willebrord Snel (1580-1626).
It was known that when a beam of light passed from air to a denser medium, such as water or glass, and struck the surface of the denser medium at an oblique angle, it was bent toward the vertical. Ptolemy maintained that the angle to the vertical made by the light hitting the surface bore a fixed relationship to the angle to the vertical made by the light after passing through the surface into the medium beyond.
Snel showed that the constant relationship was not between the angles themselves but between the sines of the angles. Ptolemy had been deluded because, with small angles, the sines are almost proportional to the angles themselves.
èNeanderthals: Cousins of Man
200,000 B.C.
AFRICA and EURASIA
By 200,000 B.C., the last individuals who might be considered members of Homo erectus were dead and the species was extinct. By then, though, some had evolved into hominids whose brains were every bit as large as ours, although they were somewhat differently proportioned, less massive in front and more massive in the rear. They had first appeared not long before this time and were probably instrumental in bringing about the end of the older species. The first traces of such hominids were discovered in 1856, in the valley of the Neander River in western Germany. Neander Valley is Neanderthal in German, and the skeletal remains were referred to as Neanderthal man at first, or simply Neanderthals.
These were the first hominids to be discovered. They were clearly different from modern human beings. Their skulls were distinctly less human than our own. They had pronounced eyebrow ridges, large teeth, protruding jaws, and receding foreheads and chins.
Because they were the first hominids to be discovered, and because the Western world still believed strongly that the Earth was only a few thousand years old (as the Bible seemed to imply), there was a certain reluctance to accept the Neanderthal bones as remains of an early form of Homo sapiens. Some preferred to consider them remains of ordinary members of Homo sapiens who were suffering from some sort of bone disease or other abnormality.
When more examples of Neanderthal skeletons were found and all had the same kind of skulls, however, the notion of abnormality could not be maintained. The French anthropologist Paul Broca (1824-1880) marshalled the arguments in favor of Neanderthals being a more primitive form of life than we ourselves, and that turned the tide.
The formal name for the Neanderthals was at first Homo neanderthalensis, but they were so like us in all but a few details of the skull that they were finally recognized as being of our species. And why not? There is evidence that they may have interbred with human beings of the present type. They are now referred to as Homo sapiens neanderthalensis and are considered one of the two known subspecies of Homo sapiens. We moderns are the other.
The Neanderthals lived from 200,000 B.C. to 30,000 B.C. in Africa and Eurasia. They lived during glacial times and hunted the mammoth, the woolly rhinoceros, and the giant cave bear. Their stone tools were greater in variety and more delicate and precise than had ever been seen before. They definitely knew how to start fires.
They were the first hominids to bury their dead.
Earlier hominids, like animals generally, simply left their dead lying where they had fallen so that they were scavenged by predators and what was left over rotted. The fact that Neanderthals buried their dead, thus preserving them from scavengers, if not from decay bacteria, tends to show that they valued life somehow, felt affection, and cared for individuals. Sometimes the dead were old and crippled and could only have lived as long as they did with the loving help of others of the tribe.
What's more, food and flowers were often buried with the corpse, and this seems to indicate that Neanderthals felt life continued on an individual basis after death. If they felt that there was life after death, then this might indicate the first stirrings of what we can call religion -- a feeling that there is more to the Universe than is apparent to the senses.
╥The Stages of Sleep
1952 A.D.
U.S.A.
Dreams were the subject of mystical theories in primitive times, being viewed as messages from some other realm not available to the waking senses. Freud initiated another form of dream analysis, but some think it has mystical components as well.
It was not till 1952 that straightforward observations were made concerning dreams, which didn't make use of the subjective reports of the dreamer. In that year the American psychologist William Charles Dement (b. 1928), studying sleeping subjects, noticed periods of rapid eye movement (REM) that sometimes persisted for minutes. During these periods of REM sleep, breathing, heartbeat, and blood pressure rose to waking levels. He noted that such REM sleep took up about a quarter of the sleeping time.
Sleepers who are awakened during these periods generally report that they were having a dream. Furthermore, a sleeper who is continually disturbed during these periods begins to suffer psychological distress. The periods of REM sleep are then multiplied during succeeding nights as though to make up for the lost dreaming.
It would seem, then, that dreaming has some important function in maintaining the working efficiency of the complex human brain. In this connection, REM sleep has been found to occur in infants to an even greater extent than in older individuals and to occur in mammals other than human beings, too. Exactly what the function of REM sleep and dreaming might be remains a matter of dispute, however.
·Pauling Proposes Resonance
1931 A.D.
PASADENA, CALIFORNIA
Four years earlier, London had applied quantum mechanics to the electron- sharing between hydrogen atoms in the hydrogen molecule. In 1931 the American chemist Linus Carl Pauling (b. 1901) extended this to the electron-sharing in organic compounds generally.
Consider the benzene molecule, for instance. It consists of six carbon atoms in a hexagonal ring, with one hydrogen atom attached to each carbon atom. Such a ring must have single bonds and double bonds in alternation. Double bonds in ordinary organic compounds represent a region of activity where two hydrogen atoms can easily be added. In the case of benzene, however, the double bonds are stable and are difficult to add to. The great stability of the benzene ring was a puzzle. Some suggested that the double bonds switched endlessly, so that any given adjacent pair of atoms were connected by a single bond and a double bond in rapid alternation.
Pauling showed in 1931, however, that if all the atoms of a molecule were in a single plane (as was true of benzene) and symmetrically placed (as was again true of benzene), then the electron waves would spread out over the carbon atoms generally, so that what connected the carbon atoms was neither an ordinary single bond nor an ordinary double bond but something intermediate between the two. This spreading out of the electrons (resonance) represented a very stable conformation, and any molecule increased in stability where there was an opportunity for resonance.
The concept of resonance helped greatly in explaining the manner of chemical reactions and made them far more predictable. For this, and for his work on chemical structure made possible by the concept of resonance, Pauling was awarded the Nobel Prize for chemistry in 1954.
ìRespiration and Combustion
1783 A.D.
FRANCE
Antoine Lavoisier, having worked out his theory of combustion as the combination of fuels with oxygen from the air, thought of respiration. Animals ate food that contained carbon. They breathed air that contained oxygen and exhaled air that contained less oxygen and more carbon dioxide.
In collaboration with a French scientist, Pierre-Simon de Laplace (1749-1827), Lavoisier undertook a series of experiments designed to measure the amount of heat and carbon dioxide produced by a guinea pig. It turned out that the amount of heat was about what would be expected from the production of that much carbon dioxide, and Lavoisier concluded that respiration was a form of combustion.
The essential point was that the laws that governed combustion outside the body seemed to hold inside the body as well. This was another blow against vitalism, the system of thought that gave life special status.
ΩResonance Particles
1960 A.D.
U.S.A.
The bubble chamber was excellent at detecting ultra-short-lived particles. The American physicist Luis Walter Alvarez (1911-1988) constructed huge bubble chambers and, beginning in 1960, detected particles that existed for only a few trillionths of a trillionth of a second before breaking down. The tracks they left in this incredibly short lifetime, even if they moved at the speed of light, were too small to detect directly. The existence of these so-called resonance particles could only be deduced from the nature of their longer-lived breakdown products.
The resonance particles, all hadrons, Kaons and Hyperons), came to be discovered in great numbers until something like 150 had been found. It seemed impossible for so many different particles to exist separately, so the search was on for still simpler and far fewer particles that, in different combinations, might make up all these resonance particles.
For this work, Alvarez was awarded the Nobel Prize for physics in 1968.
≈Inventing the Six-Shooter
1835 A.D.
U.S.A.
The various handguns that had been used for nearly four centuries could only be fired once before time had to be taken to reload. Clearly this was a vulnerable time for the user, and the ability to fire more than once before reloading would provide an advantage against opponents not so equipped.
The first successful handgun of this sort held six bullets in a cylinder that automatically rotated with each shot, bringing another bullet into line for shooting. Known as a revolver, or a six-shooter, it was patented in 1835 by the American inventor Samuel Colt (1814-1862). The revolver became standard equipment in America's pioneer society. No tales of the wild West, either in print or on film, could exist without copious use of the revolver.
iDiscovering Rhenium
1925 A.D.
GERMANY
In 1925 two German chemists, Walter Karl Friedrich Noddack (1893-1960) and Ida Eva Tacke (b. 1896), detected a new element with the atomic number of 75.
They named it rhenium, after the Latin name of the Rhine river.
Although they didn't know it at the time, Noddack and Tacke (they were married the next year) had discovered the 81st and last element that possessed stable isotopes. Four elements between 1 and 92 now remained to be discovered, atomic numbers 43, 61, 85, and 87. Of these, elements 85 and 87 could be assumed to be radioactive, but there seemed no reason to suppose that elements 43 and 61 were. In fact, Noddack and Tacke announced the discovery of element 43 at the same time as that of rhenium. They called element 43 masurium, after a district in eastern Germany. In the case of this element, however, their observations were mistaken.
èThe RH Factor
1939 A.D.
U.S.A.
After the A, B, and O blood factors were discovered by Landsteiner, other blood factors were discovered that did not interfere with transfusion and did not involve health problems.
A Russian-born American immunologist, Philip Levine (b. 1900), was studying erythroblastosis fetalis, a disease of fetuses and newborn infants that was marked by severe destruction of the red blood cells. (Victims were therefore called blue babies.)
Levine noted, in 1939, that the mothers in these cases lacked a blood component called the Rh factor (because it had first been recognized in the blood of rhesus monkeys used as experimental animals). The mothers were Rh-negative, but the fathers were Rh-positive, which was genetically dominant, so that their offspring were Rh-positive also. However, the fetus's blood apparently brought about the production of antibodies to the Rh-positive factor in the mother's blood. These antibodies filtered into the fetus's blood and destroyed the red corpuscles.
Routine testing for Rh factor prepared physicians for this possibility, and the replacement of the infant's blood supply by new blood reduced the death rate.
êVitamin B2: Riboflavin
1935 A.D.
SWITZERLAND
Since the work of Eijkman on beriberi, biochemists had discovered a number of vitamins that, like the vitamin B that cured beriberi, were water- soluble and contained rings made up of carbon and nitrogen molecules. They came to be labeled vitamin B-1 (which cured beriberi), vitamin B-2, and so on. The whole was the B-vitamin complex.
These letter-number combinations turned out to be unsatisfactory, however, because some reported vitamins turned out to be false alarms and others were simply not given such combination names. The B vitamins therefore came to be known by chemical names. Thus vitamin B-1 came to be called thiamin, vitamin B-2 riboflavin, and so on.
Karrer, who had determined the structure of vitamin A, synthesized riboflavin in 1935 and presented the final proof of its structure.
For this work, he was awarded a share of the Nobel Prize for chemistry in 1937.
|Discovering Ribose
1909 A.D.
U.S.A.
Kossel had isolated the nitrogenous bases of nucleic acid but had not been able to go further. It was clear, though, that nitrogenous bases were not all there was in the molecule.
In 1909 the Russian-born American chemist Phoebus Aaron Theodore Levene (1869-1940) extracted a sugar from nucleic acid and identified it as ribose. It had a five-carbon molecule. Not all nucleic acid molecules possessed it, but those that did came to be known as ribose nucleic acid, almost invariably abbreviated as RNA.
The sugar, if any, in the samples of nucleic acid that did not contain ribose was not identified for another 20 years.
[Fighting Rickets
1921 A.D.
ENGLAND
By now McCollum had distinguished between fat-soluble vitamin A and water- soluble vitamin B. Vitamin C, the antiscurvy factor, was also water- soluble but had no effect on beriberi and was therefore a substance different from vitamin B.
The disease of rickets, thought to be a vitamin-deficiency disease at this time, was not affected by any of these three vitamins. The British biochemist Edward Mellanby (1884-1955) undertook to track down some additional vitamin that might be involved.
By 1921 he had located a rickets-inhibiting substance in such animal fats as cod-liver oil, butter, and suet. The vitamin was fat-soluble, but its distribution was not that of vitamin A, and its absence did not produce the symptoms that absence of vitamin A did. Clearly, then, there were two fat- soluble vitamins, and the rickets-inhibiting one was labeled vitamin D.
Also in 1921, other researchers discovered that sunshine had a rickets- inhibiting effect. Sunshine itself couldn't contain a vitamin, but it might convert some substance in skin into a vitamin. This, in fact, turned out to be the case.
The Rifle: A Better Weapon
1710 A.D.
PENNSYLVANIA
If the muzzle of a gun is rifled -- that is, outfitted with spiral grooves -- the bullet is set to spinning, and a spinning bullet can be aimed with greater precision. Rifling was tried from the early days of gunnery, but rifling requires a greater force to push the bullet through the muzzle, which means that guns have to be better constructed and are harder to reload. On the whole, the smooth-bore muzzles of muskets seemed better.
About 1710 or soon thereafter, however, the Pennsylvania rifle was designed by the Pennsylvania Dutch (not Dutch, really, but German immigrants).
The Pennsylvania rifle took twice as long to reload as the musket, but it had two to three times the range and much greater accuracy. As long as soldiers fought with muskets, they had to maintain a straight line, and all had to shoot at once in the general direction of the enemy, hoping that by sheer luck some bullets would strike home. If they fought soldiers with rifles, the rifles could pick them off before they could even get in musket range.
ΘFinding the Rings of Uranus
1977 A.D.
WASHINGTON, D.C.
On March 10, 1977, the planet Uranus moved in front of a ninth-magnitude star in the constellation of Libra. This occultation was observed by the American astronomer James L. Elliot from an airplane that took him high enough to minimize the distorting and obscuring effects of the lower atmosphere. The idea was to observe how the starlight dimmed as the atmosphere of Uranus approached the star and moved in front of it. That would yield information about the atmosphere of Uranus.
Some time before Uranus reached the star, the starlight suddenly dimmed and brightened several times. When Uranus had passed the star and it emerged, the same dimming-brightening pattern occurred in reverse. Apparently Uranus was surrounded by a series of thin concentric rings that were opaque enough to obscure starlight.
In this way, Saturn's position as the unique possessor of rings was lost, although nothing we know of can duplicate its rings, which are so large, bright, and beautiful.
ÉThe Best Early Roads
312 B.C.
ITALY
Once carts were developed, roads were needed. Vehicles could not progress rapidly over rocks and underbrush, and if they tried, the wheels would be quickly ruined. That meant that everywhere roads, reasonably wide, reasonably straight, and reasonably smooth, had to be built. This Rome understood.
In the years after its humiliation by the Gauls, Rome had perfected the legion, which was a much more flexible formation than the phalanx. The phalanx could only fight in close order, and any unevenness in the ground would upset that order. The legion, on the other hand, could disperse on uneven ground without falling into disarray and could come together again when conditions allowed.
In 312 B.C. Appius Claudius (4th-3rd century B.C.), a high Roman official, initiated the building of the Appian Way, the best road the world had yet seen. It extended from Rome to Capua, a distance of 132 miles. At first it was covered by gravel, but eventually it was paved with blocks of stone and extended to the heel of Italy.
The road allowed for the rapid movement of troops and gave Rome an enormous advantage in bringing up reinforcements or achieving surprise. Eventually Rome would build 50,000 miles of roads throughout its dominions. Some were over 30 feet wide. This meant that Roman armies could be hurried from one border to another at quick step, and relatively small forces could protect its boundaries.
Robots: Mechanical Slaves
1954 A.D.
PRAGUE, CZECHOSLOVAKIA
The word robot (from a Czech word for "serf" or "slave") had been invented by the Czech playwright Karel Capek (1890-1938) in his play R.U.R., first staged in Europe in 1920. Since Capek's time, the word has come to be applied to any manufactured device, usually envisaged as humanoid in shape (though it doesn't have to be) and made of metal (though again, it doesn't have to be), which is capable of doing work ordinarily done by human beings.
Although robots were much used in science fiction, the first patent wasn't taken out on a robotic device in real life until 1954. It was the work of the American inventor George C. Devol, Jr., who teamed up afterward with the American entrepreneur Joseph F. Engelberger (b. 1925), who had grown interested in robots as a result of reading I, Robot by Isaac Asimov (1920-1992).
For 20 years they continued to develop patents, but the manufacture of robots that were sufficiently cheap and compact to be used in industry had to await further advances in computers.
zUnderstanding Saturn's Rings
1849 A.D.
GERMANY
Saturn's rings had now been known for nearly two centuries, but their nature and how they came to exist remained uncertain and controversial.
In this connection, a French astronomer, Edouard Albert Roche (1820-1883), calculated the effect of one body on another when at relatively close range. His conclusions are useful in astronomy especially in studying very closely spaced binary stars.
He showed that if a smaller body circled a larger body, and if the smaller body was held together by gravitational forces only and chemical bonding was ignored, then tidal effects would break up the smaller body if it approached within 2-1/2 times the radius of the larger body. Again, if a cloud of particles was within 2-1/2 times the radius of a large body to begin with, that cloud could not be pulled together into a body by gravitational forces.
None of the satellites known in the Solar System at that time were within 2-1/2 times the radius of the planet they circled. However, Saturn's rings were, in their entirety, within that distance. The conclusion was that Saturn's tidal force kept them from condensing into a satellite.
ÆThe Rocky Mountains
1739 A.D.
ROCKY MOUNTAINS
North America. The explorer Pierre Gaultier de Varennes de La Vérendrye (1685-1749) had been pushing westward from the Great Lakes since 1731 and by the end of the decade had discovered Lake Winnipeg and the Black Hills of South Dakota.
Two French brothers, Pierre and Paul Mallet, had reached Colorado in 1739 and were the first Europeans to get a glimpse of the Rocky Mountains.
■Bringing Moon Rocks to Earth
1971 A.D.
HOUSTON, TEXAS
Exploration of the Moon continued in 1971. Apollo 14 reached the Moon on February 5, 1971, and its crew collected 98 pounds of Moon rocks that were brought back to Earth for analysis. They were the first samples of material collected by human beings on another world.
On July 30, 1971, Apollo 15 landed on the Moon. It carried with it a lunar rover, a land vehicle designed to travel on the airless Moon. The astronauts traveled 17 miles using it and brought back more Moon rocks to Earth.
sThe Rosetta Stone
1799 A.D.
EGYPT
While the army of Napoleon Bonaparte (1769-1821) was in Egypt, a French soldier came across a black stone near a town that Europeans called Rosetta. What he found was therefore called the Rosetta Stone.
On the Rosetta Stone was an inscription in Greek dating back to 197 B.C. It wasn't an interesting inscription in itself, but present also were inscriptions in two different forms of Egyptian writing. If, as seemed likely, this was the same inscription in three different languages, then one had an inscription in two forms of Egyptian writing, which at that time no one could read, and a Greek inscription that many scholars could read.
In the next few decades, the Rosetta Stone was studied in order to learn the Egyptian languages, so that from inscriptions and writings left behind by the Egyptians, vast stretches of Egyptian history might come to be understood.
▐The Geometry of Shadows
1822 A.D.
FRANCE
The French mathematician Jean-Victor Poncelet (1788-1867) was taken prisoner during Napoléon's invasion of Russia, and during the year and a half he spent in Russia, he meditated on geometry. The fruits appeared in 1822, when he published a book on projective geometry (roughly, the study of the shadows cast by geometric figures). Previously knotty problems yielded easily to the new technique. The book is usually considered to be the foundation of modern geometry.
╔Exploring Antarctica
1839 A.D.
ROSS ICE SHELF
Ross, who had located the North Magnetic Pole, set out in 1839 to explore Antarctic waters. In the course of this exploration, he discovered a large oceanic inlet that cuts into Antarctica and is now known as Ross Sea in his honor. The southern portion of this sea is covered with a vast overhang of ice from the continental areas behind and is now known as the Ross Ice Shelf. He also located Mt. Erebus, the southernmost active volcano.
ƒThe Rotation of Mercury
1965 A.D.
WASHINGTON, D.C.
Schiaparelli had suggested that Mercury turned one face to the Sun at all times.
This had begun to seem doubtful, since if it were true, the side of Mercury facing away from the Sun should be extremely cold. Microwaves detected from the dark side of Mercury in 1962 had indicated that it was considerably warmer than would be expected if it were eternally dark.
In 1965 two American electrical engineers, Rolf Buchanan Dyce (b. 1929) and Gordon H. Pettengill, working with microwave reflections from the Mercurian surface, were able to show that it turned on its axis in about 59 days, despite the fact that it revolved about the Sun in 88 days. This meant that every portion of the planet received sunlight at one time or another.
Eventually, the rotation was found to be 58.65 days, just two-thirds of the period of revolution, so that Mercury showed the same side to Earth every second revolution.
─The Rotation of Venus
1962 A.D.
WASHINGTON, D.C.
Although Venus approached Earth more closely than any other planet did, its period of rotation had remained mysterious. This was ironic, since the periods of rotation of other planets, even that of far distant Pluto, were known. The reason for this was that Venus's thick and featureless cloud layer precluded any possibility of seeing its surface and detecting features that could be spotted as moving around the planet.
Yet although light waves could not penetrate the clouds, microwaves could.
Furthermore, if a beam of microwaves is reflected from an object moving at right angles to the beam (as would be true of Venus if it were rotating), then the wavelength of the beam is broadened and distorted. From the extent of the distortion, the speed of rotational motion can be calculated.
In 1962 the American astronomers Roland L. Carpenter and Richard M.
Goldstein were able to show that Venus had the astonishingly slow period of about 250 days. (The figure was later refined to 243.09 days.) What's more, Venus rotated in retrograde fashion, from east to west rather than from west to east as Earth and other bodies in the Solar System do. The reason why this is so is still not clear.
▐The Royal Society
1662 A.D.
ENGLAND
There had been informal meetings of scientists in London in the mid-1600s, and the habit grew more ingrained after the Restoration (of Charles II, that is).
Like many monarchs of his time, Charles II patronized science as a way of gaining prestige for the nation and possibly material benefit as well. He therefore gave a legal charter to the Royal Society in 1662. For years, it represented the most brilliant assemblage of scientists since the great days of Alexandria.
The Royal Society received communications from members, both at home and abroad, and held meetings where members could inform one another of their work. It also published a journal called Philosophical Transactions, in which experimental work and findings could be published. (By philosophical is meant what we today would call scientific. The words science and scientist had not yet been invented.)
Other nations established scientific societies as well following the success of the Royal Society.
µInventing a Better Wheel
1887 A.D.
ENGLAND
Since wheeled transportation had been invented five thousand years before, wheels had had wooden or metal rims. These were noisy and offered no spring, so that travel on carts and wagons was a jolting affair.
In 1887 a British inventor, John Boyd Dunlop (1840-1921), decided to rim the wheels of his son's tricycle with a rubber tire (and patented the notion the following year). Rubber, though soft, actually wears better than wood or iron does. What's more, Dunlop made it a pneumatic tire: what went round the rim was an air-filled tube, which was covered by a tire with a rubber tread.
This gave a vehicle spring and cut down the noise tremendously, so that tires were soon used for automobiles and other vehicles as well.
kRutherfordium
1964 A.D.
ENGLAND
In 1964 both Soviet and American researchers reported the formation of atoms of element number 104. There was some dispute as to priority and name. The Soviets named it kurchatovium after Igor Vasilyevich Kurchatov (1903-1960), who had led the team that developed the Soviet nuclear bomb. The Americans named it rutherfordium after Ernest Rutherford. @
⌐Alpha and Beta Rays
1897 A.D.
UNITED KINGDOM
The radiations given off by uranium were of more than one kind. Some were deflected only slightly in a direction that indicated them to be positively charged. Some were deflected much more sharply in the opposite direction and were therefore negatively charged. Both had to consist of streams of particles, and the particles of the former were clearly the more massive.
The British physicist Ernest Rutherford (1871-1937) noted this in 1897. He called the massive, positively charged radiation alpha rays, and the lighter, negatively charged radiation beta rays, after the first two letters of the Greek alphabet. Those names have remained in use ever since. @
aThe Sabin Vaccine
1957 A.D.
CINCINNATI, OHIO
The Salk vaccine had been proved effective against poliomyelitis.
However, the Salk vaccine consisted of dead virus that had to be injected, and whose ability to stimulate antibody production might not be long-lasting. The Polish-American microbiologist Albert Bruce Sabin (b. 1906) thought it might be possible to find strains of polio that were too feeble to produce the disease even while alive but that would activate antibody formation and continue to do so as long as they remained in the body. Such live strains could be taken by mouth.
When Sabin thought he had the proper strains, judging by animal experiments, he tried them first on himself, then on prison volunteers. In 1957 the Sabin vaccine came into widespread use in the Soviet Union and eastern Europe. Three years afterward, it came into use in the United States as well.
ÿSaccharin
1879 A.D.
U.S.A.
Discoveries can be made entirely by accident. In 1879 the American chemist Ira Remsen (1846-1927) and a student of his, Constantine Fahlberg, synthesized a compound named orthobenzoyl sulfimide. Ordinarily it would have ended there, for new organic compounds are manufactured endlessly every year. This time, however, Fahlberg happened to put his fingers to his mouth without knowing that a few grains of the new compound had adhered to them. He was astonished by an intensely sweet taste.
The compound was eventually named saccharin (from a Latin word for "sweet"). It was the first of the commercial sugar substitutes and is still a major one today.
<The Salk Vaccine
1953 A.D.
UNIVERSITY OF PITTSBURGH, PENNSYLVANIA
Poliomyelitis (infantile paralysis) was a particularly frightening disease, because when it did not kill, it often paralyzed permanently, leaving people in wheelchairs or even iron lungs. What's more, it often hit young people.
Once the polio virus could be cultured in chick embryos, however, as shown by American microbiologist John Franklin Enders (1897-1985) and his group, it was possible to experiment with it.
Thus the American microbiologist Jonas Edward Salk (b. 1914) tried to kill the virus, so that it would not give rise to the disease, but to leave it sufficiently intact that it would stimulate the growth of antibodies and lead to immunity should a living virus later invade.
First he tried his preparation (Salk vaccine) on children who had recovered from polio, to see if it raised the antibody content. Then in 1953 he dared to try it on children who had not had the disease, to see if antibodies would develop. They did, and within two years mass inoculation had begun. The dread disease became a thing of the past.
JBacterial Cultivation
1876 A.D.
SILESIA, GERMANY (POLAND)
When an anthrax epidemic struck the cattle in Silesia (eastern Germany), a local physician, Robert Koch (1843-1910), grew interested. In 1876 he located the particular bacterium that caused anthrax in the spleen of infected cattle and transferred it to mice, carrying the infection from mouse to mouse and recovering the same bacilli in the end. More important still, he learned to cultivate the bacteria outside the living body, using blood serum at body temperature.
Then he learned to make use of solid media for growing bacteria -- gelatin, or a complex carbohydrate called agar, which could be obtained from seaweed. When grown in such solid media, the bacteria could not move about easily, and if the bacteria happened to be isolated in one spot, they would, by division and redivision, give rise to a patch of descendant bacteria with no admixture of outside varieties. Bacteria could then be transmitted to animals or allowed to start new cultures with the certainty that only a particular strain of bacteria was being worked with.
In short, French chemist Louis Pasteur's germ theory was given practical application by Koch. Koch showed how the causative bacteria could be isolated, then used to produce the disease, then regained from the diseased animal, and finally worked with to find a prevention or cure.
╡Ions and Crystals
1914 A.D.
UNITED KINGDOM
Thirty years earlier Swedish chemistry student Svante August Arrhenius (1859-1927) had advanced the notion that electrolytes in solution dissociated into ions. The idea was that a substance such as sodium chloride existed in solid form as a molecule, symbolized as NaCl, but on solution split up into the positively charged sodium ion (Na+) and the negatively charged chloride ion (Cl-).
When the British father-and-son physicists, William Henry (1862-1942) and William Lawrence (1890-1971) Bragg, were studying X-ray diffraction, however, they found that that phenomenon could best be understood if it was supposed that in a solid crystal of sodium chloride there were no intact molecules, merely sodium ions and chloride ions positioned with geometric regularity. Sodium chloride and many other compounds did not exist as molecules in the older sense, then, but as arrays of ions held together by electromagnetic interaction.
µSouth America
1990 A.D.
SOUTH AMERICA
Notice the vast green stretch in the northeast part of South America. That green is the Amazon Jungle, a huge area of plant and animal life, many of which are found nowhere else in the world.
Unfortunately, there is less and less of this jungle each day as people move into the area and clear the land. Many environmentalists are concerned about the results of this deforestation on the local and global environment.
South America covers 6.8 million square miles and is inhabited by 296 million people. It is the fourth largest continent and has the largest tropical rain forest in the world, the Amazon, which occupies about two fifths of its area. The Amazon contains more plant types than any place on earth and is navigable by oceangoing ships as far north as Iquitos, Peru.
The continent also has the world's highest navigable lake, Lake Titicaca in the Andes, and the Atacama Desert in Chile, one of the driest places in the world.
In the Andes, the Incas founded a great empire centered in Cuzco, Peru that stretched more than 2,500 miles along the west coast of the continent. It was tied together by carefully constructed highways and bridges. In his quest for gold, the Spaniard Francisco Pizarro destroyed the Inca Empire in 1533.
Following the conquests of Pizarro and others, much of South America came under the dominion of Spain, but in the 1800s Simon Bolivar liberated much of the continent. Brazil, once a colony of Portugal, took its own route to nationhood, becoming independent in 1823.
Today, the most highly developed countries in South America are Argentina, Brazil, Uruguay and Venezuela. The continent is rich in such natural resources as farmlands, timber, minerals, copper, gold, lead, tin, zinc and coffee.
⌐ Continental Drift
1912 A.D.
GERMANY
As soon as the shoreline of South America had been mapped, three and a half centuries before, people had noticed that South America and Africa gave the impression that they would fit together neatly if they were moved together.
In 1912 the German geologist Alfred Lothar Wegener (1880-1930) proposed that Africa and South America had indeed once formed a single landmass, which had broken in two, and that the two parts had then moved apart in a sort of continental drift.
In fact, he suggested that all the continents had originally formed a single mass (Pangaea, Greek for "all-earth") surrounded by a continuous ocean (Panthalassa, Greek for "all-sea"). This large granite mass of Pangaea had broken into chunks that slowly separated, floating on a basalt ocean-floor, and over hundreds of millions of years, produced the pattern of fragmented continents that we now have.
Unfortunately, the notion of granite floating on basalt did not seem a tenable hypothesis, and on the whole, few people took Wegener's notions seriously at the time.
By 1953 it had been known for 30 years that there was a mountain range down the middle of the Atlantic Ocean. Eventually it was understood that this was part of a world-girdling range called the Mid-Oceanic Ridge.
In 1953 the American physicists Maurice Ewing (1906-1974) and Bruce Charles Heezen (1924-1977) discovered that a deep canyon ran the length of the ridge. It was called the Great Global Rift. There were places where the rift came quite close to land: it ran up the Red Sea between Africa and Arabia and skimmed the borders of the Pacific through the Gulf of California and up the coast of the state of California.
The rift seemed to break the Earth's crust into plates tightly joined as though fitted together by a skilled carpenter. They were therefore called tectonic plates, from a Greek word for "carpenter." The study of the evolution of the Earth's crust in terms of these plates is called plate tectonics, and it has totally revolutionized geology, explaining a great deal that had been mysterious before.
There are six large tectonic plates and a number of smaller ones, and it is along the boundaries of the plates that Earth's quakes and volcanoes seem to be concentrated. One plate, which includes most of the Pacific Ocean, and with boundaries of the eastern coast of Asia and the western coast of America, accounts for about 80 percent of the earthquake energy released on Earth.
▀The Skylab Satellite
1973 A.D.
CAPE CANAVERAL, FLORIDA
The first American orbiting object that might be considered a space station was Skylab. It was 118 feet long and was launched into orbit on May 14, 1973, about 270 miles above Earth's surface. On May 25, three astronauts were carried to Skylab and remained on it for 28 days. A second crew remained for 60 days, and a third for 84 days. Surveys were taken of Earth's mineral resources and its crops and forests. Photographs of the Sun were also taken.
╕Moons of Other Planets
1789 A.D.
LONDON, ENGLAND
By the end of the 1600s, 10 satellites were known: Earth's moon, the four satellites of Jupiter discovered by Galileo, and the five satellites of Saturn discovered by Huygens and Cassini.
A century had passed after Cassini's discovery of Dione in 1684 without any further satellite discoveries. Then in 1787, Herschel discovered two satellites of his own planet, Uranus.
He named them Titania and Oberon, after the queen and king of the fairies in William Shakespeare's A Midsummer Night's Dream, thus breaking with the traditional use of the classical myths.
In 1789 Herschel discovered two more satellites of Saturn, which were nearer the planet than the others were. He named them Mimas and Enceladus, after two giants who had rebelled against Zeus (Jupiter) in the Greek myths. Fourteen satellites were now known: Earth had one, Jupiter four, Saturn seven, and Uranus two. No more were to be discovered for half a century.
╢ Saturnian System
1980 A.D.
PASADENA, CALIFORNIA
The probe Voyager 1 passed by Saturn on November 12, 1980. Voyager 2 followed not long after. A number of the satellites of Saturn were for the first time seen as more than points of light.
Titan, the largest satellite, was known to have an atmosphere of methane, but methane turned out to be present in small quantities compared to nitrogen. (Nitrogen is a gas difficult to detect from Earth because its absorption characteristics are not easy to observe and study.) The Titanian atmosphere turned out to be 98 percent nitrogen and 2 percent methane and may be thicker than Earth's atmosphere. The atmospheric haze prevented any view of the surface, where there might be nitrogen lakes with dissolved polymers of methane and (a few speculate) possibly some form of life.
The other Saturnian satellites were, as might be expected, cratered. Mimas, the innermost of the nine sizable satellites, has a crater so large that the impact that produced it must have nearly shattered it.
Enceladus, the second of the nine, is comparatively smooth, while Hyperion is the least spherical and has a diameter that varies from 90 to 120 miles. Iapetus is a two-toned satellite, with one hemisphere much darker than the other, as though one side were icy and the other coated with dark dust. The reason for this is not yet clear.
The Saturn probes succeeded in finding eight satellites that were too small to be seen from Earth, bringing the total number to 17. Of the new satellites, five are closer to Saturn than Mimas is. Two satellites that are just inside Mimas's orbit are unusual in being co-orbital. That is, they share the same orbit, chasing each other around Saturn endlessly. This was the first known example of such co-orbital satellites.
The three new satellites beyond Mimas also represent unprecedented situations. The long-known satellite Dione was found to have a tiny co-orbital companion, Dione B, which circles Saturn at a point 60 degrees ahead of Dione. As a result, Saturn, Dione, and Dione B are always at the apices of an equilateral triangle. This is a comparatively stable gravitational position, called a Trojan situation because it is also the position of the Sun, Jupiter, and the Trojan asteroids.
The satellite Tethys has two tiny companions, one 60 degrees ahead of it in orbit and one 60 degrees behind it. Clearly, the Saturnian satellite system is the richest and most complex in the Solar System.
The Saturnian rings were also found to be far more complex than had been thought. From a close view, they consist of hundreds, perhaps even thousands, of thin ringlets, which look like the grooves on a phonograph record. In places, dark streaks show up at right angles to the ringlets, like spokes on a wheel. Then too, a faint outermost ring seems to consist of three intertwined ringlets. None of this can be explained so far. It may be that a straightforward gravitational situation is being complicated by electromagnetic effects.
qSaturn's Particle Rings
1857 A.D.
LONDON, ENGLAND
By this time it seemed very likely that Saturn's rings were composed of myriads of small particles. Since they were inside Roche's limit, solid particles would break up under tidal influences and be unable to coalesce again. In 1857 Maxwell showed that this was indeed so, based on purely theoretical considerations, and no one has doubted it since.
`Saturn's Ring
1656 A.D.
THE HAGUE, NETHERLANDS
Galileo had observed Saturn through his telescope in 1612 and noted something odd about it. There seemed to be projections on either side. He could not quite make them out, and after a while they disappeared. It annoyed Galileo. After all, he had been attacked by religionists who said that his telescope produced optical illusions, and here was one case where perhaps it did. He refused to look at Saturn again.
In 1655, however, the Dutch astronomer Christiaan Huygens (1629-1695), with the help of a Dutch philosopher and optician, Benedict Spinoza (1632-1677), worked out a new and better method for grinding lenses. He installed his improved lenses in a telescope that was 23 feet long, and with that he studied Saturn in 1656.
He could see what it was that had puzzled Galileo. Saturn was surrounded by a thin, broad ring that did not touch the planet at any point. No other object in the sky had so peculiar a structure, and Saturn is widely considered the most beautiful object in the sky because of it.
In addition, he discovered that Saturn had a satellite, which he named Titan (because Saturn, or Cronos as the Greeks called him, was the leader of a group of gods called Titans).
That same year, he discovered that the middle star of Orion's sword was not a star but a cloud of luminous gas. It is now known as the Orion nebula.
BSaturn's Two Rings
1675 A.D.
PARIS, FRANCE
French astronomer Gian Cassini (1625-1712), studying Saturn's ring in 1675, noted that a dark line seemed to separate the ring into an outer one that was narrow and bright and an inner one that was broad and a little less bright. Some astronomers thought the ring was a single object with a dark line running around it, but the majority opinion favored the possibility that there were two separate rings with a true division. The majority proved to be correct. The dark line is Cassini's division to this day, and people speak of Saturn's rings in the plural.
@Saturn's Moons
1671 A.D.
PARIS, FRANCE
By now, six satellites were known: four circling Jupiter (Io, Europa, Ganymede, and Callisto), one circling Saturn (Titan), and, of course, one circling Earth (Moon). Dutch astronomer Christiaan Huygens (1629-1695), in an uncharacteristic moment of mysticism, thought that the six satellites matched the six planets in number (Mercury, Venus, Earth, Mars, Jupiter, and Saturn), which balanced things, so that no further satellite discoveries were to be expected.
French astronomer Gian Cassini (1625-1712) blew that view to smithereens in 1671 when he discovered a second satellite of Saturn, which he named Iapetus. Over the next 13 years he discovered three more: Rhea, Dione, and Tethys. These names are those of Titans: Iapetus was a brother of Saturn (Cronos), while the other three were among his sisters.
5The Steamboat
1787 A.D.
U.S.A.
Until this time, steam engines had been used only to power pumps and textile machinery. Yet if a steam engine could turn a paddle wheel, it could also serve as a mechanical oar of great power, which could drive a ship through water against both wind and current without the expenditure of human muscle (except that of feeding fuel to the engine so that steam could be generated).
The first person to achieve a workable steamboat was the American inventor John Fitch (1743-1798). On August 22, 1787, his first steamboat navigated the Delaware River for the first time. For a while Fitch kept up a regular schedule of trips from Philadelphia to Trenton and back. However, there were few passengers, the ship operated at a loss, the financial backers quit, and the ship was finally destroyed in a storm in 1792.
>Using Scales for Weight
5000 B.C.
EGYPT
Trade is bound to lead to measurement -- so much of this for so much of that. You can heft things by hand, but that is subjective and buyer and seller will never agree. The easiest way to be objective is to hang two pans from opposite ends of a rod that is held up in the middle. The thing being weighed is placed in one pan, and standard weights are placed in the other until the two pans are in balance. The principle is so simple and the device itself so easy to make that it may have been used as early as 5000 B.C. in Egypt and have been reasonably accurate.
₧Scandium
1879 A.D.
SWEDEN
Since Gadolin had discovered the rare earths, about a dozen elements had been extracted from them that all closely resembled each other. An element that was not exactly one of the rare earth series, but that rather resembled them in its properties, was discovered in 1879 by the Swedish chemist Lars Fredrik Nilson (1840-1899). He named it scandium, for Scandinavia.
The Swedish chemist Per Teodor Cleve (1840-1905) pointed out soon afterward that its properties were exactly those of Mendeleyev's "eka-boron" and that it fit into the periodic table just where eka-boron had been placed. A second of Mendeleyev's predicted elements had thus been discovered.
Scanning Electron Microscopes
1970 A.D.
U.S.A.
In an ordinary electron microscope, an electron beam, in a vacuum, passes through the sample being studied and leaves an imprint on the recording device beyond. The sample must be very thin if this is to work.
If a low-energy beam of electrons is used, however, it can scan the surface of a sample much as an electron beam scans the picture tube of a television set.
The electrons will induce the surface to emit electrons of its own, and these induced electrons can be detected.
Such a scanning electron microscope produces a three-dimensional effect that gives more information about the surface and produces still greater magnifications than an ordinary electron microscope can do. In some cases it can even show the position of individual atoms.
The first practical scanning electron microscope was built in 1970 by the British-born American physicist Albert Victor Crewe.
HScientific Ballooning
1804 A.D.
FRANCE
The first important use of balloons for scientific research came in 1804, when Biot and Joseph Louis Gay-Lussac (1778-1850) made a balloon ascension that reached a height of four miles, higher than any peak in the Alps. They took the opportunity to test the composition of the air at that height and also to study the nature of Earth's magnetic field. They found no change in either compared with measurements at sea level.
This was the beginning of high-altitude investigations that were to carry human beings beyond the atmosphere altogether a century and a half later.
»Screw Threads
1841 A.D.
ENGLAND
Industrial production could be increased if parts were standardized. The British inventor Joseph Whitworth (1803-1887), for instance, had worked out techniques for producing devices that matched each other not merely to the nearest 16th of an inch but to the nearest thousandth.
Even such improved methods wouldn't help if different manufacturers produced items of different overall dimensions, however. For instance, one factory might produce screws, all alike, and so might another, but the pitch of the screws in the two factories might be slightly different, so that one screw might fit a particular bolt and the other might not. In 1841 Whitworth suggested a standard pitch for all screws made everywhere, and the suggestion was eventually adopted.
When trade becomes first national, then international, and finally worldwide, such standardization becomes first advisable, then intensely useful, and finally indispensable.
5The Aqualung
1943 A.D.
FRANCE
Until now, if you wanted to spend a reasonable period of time under water with sufficient mobility to allow exploration, you needed a diving-suit, which was heavy and required a lifeline.
In 1943, even while he was with the French underground fighting the occupying Germans, the French oceanographer Jacques-Yves Cousteau (b. 1910) invented the Aqualung.
This was a device that supplied the diver with air under pressure. It was self-contained and light, so that with an Aqualung and finned devices on their feet, divers could probe under the water's surface with freedom and mobility. This made it possible to observe coral reefs and ocean life in the uppermost layers of the ocean and also introduced a new sport, scuba diving. (Scuba is an acronym for "self-contained underwater breathing apparatus.")
^Scurvy
1747 A.D.
LONDON, ENGLAND
Ever since Vasco da Gama's voyage, scurvy had been an increasing menace. More men were disabled by scurvy on long voyages than by any other cause. This was particularly serious in Great Britain, which depended on its navy for protection and on its merchant ships for its prosperity.
A British physician, James Lind (1716-1794), had served in the navy and knew that the diet on board ship was monotonous in the extreme, consisting of hardtack, salt pork, and other food items whose only virtue was that they didn't spoil in an age without refrigeration or canning. He also knew that scurvy appeared in prisons, in besieged towns, on overland exploring expeditions -- always where diet was limited and monotonous.
Lind therefore studied the effect of adding food items that didn't last well, especially fruits and vegetables, to the diet of people affected with scurvy. In 1747 he found that citrus fruits worked amazingly well in effecting relief. It was nearly half a century, however, before the British navy could bestir itself to make use of that fact and put an end to the menace of scurvy.
@Sea Navigation
1100 B.C.
GREECE
Boats had been in existence for over 2,000 years, but they had been confined to rivers. When they did venture out to sea, they generally hugged the coast. Even the Cretans, the boldest seagoers up to this time, had confined themselves to the eastern Mediterranean and felt safest in the Aegean Sea, where numerous islands made possible short sails from land to land.
Greek legends treated distant portions of the sea as places of myth and mystery. The tale of Jason and the Argonauts reflects early ventures into the large and island-free Black Sea. Homer's Odyssey describes the adventures of Odysseus in the even larger western Mediterranean.
The first to cast out boldly into the open sea were the Phoenicians. They noted that the seven stars that made up the familiar grouping of the Big Dipper were always located to the north and were visible all night long at every season of the year (barring the presence of clouds). This must surely have been known for a long time, but the Phoenicians seem to have been the first who were willing to risk their ships and lives on the fact. By observing the Big Dipper, they knew always which direction was north, and from that they knew all other directions. This obviated the fear of being lost once out of sight of land and "landmarks." There were always the "skymarks," so to speak.
sSeaplanes
1911 A.D.
ALBANY, NEW YORK
The American inventor Glenn Hammond Curtiss (1878-1930) was deeply involved in the early airplane flights. He was the first to fly a mile in the United States, in 1908, and he flew from Albany to New York in 1910.
In 1911 he finally built a practical seaplane, or hydroplane, with pontoons rather than wheels, that could take off and land on water.
éSoutheast Asia
1990 A.D.
SOUTHEAST ASIA
Hot, humid, and covered with jungle. That is the impression many people have of Southeast Asia, but the area is much more than that.
This is one of the fastest growing economic regions in the world. Singapore, Taiwan, Hong Kong, Thailand and other "tigers," as they are sometimes called, have adopted capitalist principles and risen with a dramatic suddenness into the world economic scene.
Not all parts of this region have been so successful. Under the leadership of a socialist-isolationist military government, Myanmar (once called Burma and once the most prosperous country in southeast Asia), is mired in poverty.
Sea-Floor Spreading
1960 A.D.
U.S.A.
Once it was understood that the Earth's crust was divided up into a few large plates and some smaller ones, it seemed unlikely that the plates retained their position forever. Although Wegener's theory of continental drift seemed quite impossible, since the continents could not plow their way through the underlying rock, the similarity between the opposite coasts of the Atlantic Ocean might be accounted for in other ways.
In 1960 the American geophysicist Harry Hammond Hess (1906-1969) decided it was quite possible that molten magma from the mantle might ooze upward through the Great Global Rift. That might force the North American and South American plates farther westward while the Eurasian and African plates were forced further eastward.
The Atlantic ocean would thus widen, in what came to be called sea-floor spreading, but its coasts would retain their shape from the time the continents were in contact.
Continental drift, then, was not the result of continents slowly floating on the underlying rock, as Wegener had thought. The continents were firmly fixed to the plates and could not move through them. But the plates themselves were forced apart in some places and forced together in others. Actual evidence for this new view was not long in coming.
KSolar Eclipses
1715 A.D.
ENGLAND
On April 22, 1715, a solar eclipse was to take place and the path of totality was to cross Great Britain and parts of Europe. It had been 23 centuries since Thales had predicted an eclipse and it was perfectly understood by astronomers that eclipses were phenomena that were natural, harmless, and splendid. Nevertheless, superstition is immortal, and in order to prevent as much panic as possible, Halley carefully plotted out the path the eclipse would take and prepared maps of it well in advance so that everyone knew exactly when he or she would see the Sun lose its light.
Halley also organized a large number of observers throughout Europe to watch and time the eclipse. This was the first eclipse for which astronomers turned out en masse. From this point on, every eclipse would bring its crowd of observing astronomers.
Second Law of Thermodynamics
1850 A.D.
GERMANY
The first law of thermodynamics (that is, the law of conservation of energy -- see 1847) is an essentially optimistic law. Since no energy can be destroyed, it might seem that energy is always there to be used over and over.
Not all energy is equally useful, however. Carnot had pointed out that in a steam engine some of the energy must be lost as heat and so not all of it could be turned into useful work.
The German physicist Rudolf Julius Emanuel Clausius (1822-1888) found that this was true of any energy conversion: some energy was always lost as heat, and heat could never be converted completely to any other form of energy.
As a result, the energy supply of the Universe was constantly being degraded to heat, and the amount of useful energy was constantly decreasing.
Clausius proposed that if the ratio of the heat content of a system to its absolute temperature were taken, that ratio would always increase in any process taking place in a closed system. Under perfect conditions, it might remain constant, but it would never decrease. Years later, Clausius gave this ratio the name of entropy for some rather obscure reason.
Clausius had thus established the second law of thermodynamics, that the amount of entropy in the Universe always increases and will some day reach a maximum when no useful energy is left and disorder is total. That sounds pessimistic, but since it will probably take many trillions of years to degrade all the energy in the Universe, it can't be considered a matter of immediate concern.
The Seismograph
1855 A.D.
ITALY
An earthquake of considerable magnitude cannot be mistaken for anything else.
However, there are numerous small earthquakes that, in our busy, rumbling life, may go unnoticed.
In 1855 an Italian physicist, Luigi Palmieri (1807-1896), invented a device for the detection of such small tremors.
This consisted of horizontal tubes, turned up at the ends and partly filled with mercury. Even slight quakes would cause the mercury to bob from side to side.
Small iron floats were so attached that their movements could be read off on a scale and the intensity of the quake estimated.
This was the first crude seismograph. It was not very useful; traffic vibrations, for instance, were difficult to distinguish from minor earthquakes; but it was a beginning.
XThe Modern Seismograph
1880 A.D.
ENGLAND
The first attempt to develop a device that would measure the strength of earthquakes had been made by Palmieri. In 1880 the first modern seismograph (from Greek words meaning "to record earthquakes") was devised by a British geologist, John Milne (1850-1913). This was, essentially, a horizontal pendulum, one end of which was fixed in bedrock. When the ground moved as a result of a quake, the motion was recorded on a turning drum by a pen (eventually by a ray of light). Milne established a chain of seismographs in Japan and elsewhere, which marked the beginning of modern seismology.
0The Sewing Machine
1846 A.D.
BOSTON, MASSACHUSETTS
The idea of a sewing machine was natural enough, since machines that wove cloth in patterns had been around for quite a while. The trick was to make the machine small enough and convenient enough to use in the home. There were a number of near misses, but the first that really caught on -- the prototype of those that quickly came to be used -- was invented by the American Elias Howe (1819-1867).
In 1846 he obtained a patent for his device, in which the eye of the needle was placed near the needle point and two threads were used, with stitches made by means of a shuttle. He proved the value of his machine by racing against five women sewing by hand and winning easily.
This was the first product of the Industrial Revolution that specifically lightened a woman's household tasks.
fSex Hormones
1934 A.D.
GERMANY
Butenandt had isolated the male sex hormone androsterone and worked out its structure. In 1934 the Croatian-born Swiss chemist Leopold Stephan Ruzicka (1887-1976) synthesized androsterone and showed that Butenandt's analysis was correct. For this he shared the Nobel Prize for chemistry in 1939 with Butenandt.
Meanwhile, also in 1934, Butenandt isolated progesterone, a female sex hormone of vital importance to the chemical mechanisms involved in pregnancy. Butenandt, like Domagk, could not accept the Nobel Prize because of Hitler's ruling. It was not until 1949 that he could accept it formally.
bSex-Linked Characteristics
1910 A.D.
U.S.A.
In 1910 Morgan, still working with fruit flies, noted a white-eyed male fly among a mass of ordinary red-eyed ones. It was a mutation such as De Vries had observed among plants.
Morgan crossed the white-eyed male with a red-eyed female, and all the offspring were red-eyed (red was dominant). In the next generation, however, there were both red-eyed and white-eyed flies, and all the white-eyed ones were males.
This was the first observation of sex-linked characteristics. It meant that males and females had to be differentiated in chromosome makeup. The way they are is that not all the chromosomes make up perfect pairs. In the case of one of them, the female fruit fly did indeed have a pair (an X chromosome and an X chromosome), but the male had one normal chromosome and a stub (an X chromosome and a Y chromosome). A white-eye gene on the female X chromosome could be overbalanced by a red-eye gene on the pair, but a white-eye gene on the male X chromosome had nothing to balance it on the Y- chromosome stub.
The chromosome pairs of male and female human beings show a similar differentiation.
bSeyfert Galaxies
1943 A.D.
WASHINGTON, D.C.
More than 20 years had passed since it had become clear that there were innumerable galaxies lying deep in space, but there didn't seem much hope of learning any significant details about the inner structures of objects that were millions of light-years distant.
In 1943, however, the American astronomer Carl K. Seyfert (1911-1960) detected an odd galaxy with a very bright spot at the center. Other galaxies of the sort have since been observed, and the entire group is known as Seyfert galaxies. Altogether perhaps one percent of all galaxies are Seyfert galaxies.
This was the first case of what came to be called active galaxies, those with centers that seem to be the site of activity beyond the normal. Much more remained to be discovered about such galaxies when it became possible to observe them outside the range of visible light.
£Vanguard Measures Earth
1959 A.D.
CAPE CANAVERAL, FLORIDA
The previous year, the United States had launched a small satellite, Vanguard I. It revolved about the Earth in 2-1/2 hours and its orbit could be studied in great detail. Its perigee (the point of its closest approach to the Earth) moved somewhat with each revolution, in part because of the gravitational pull of the Earth's equatorial bulge upon it.
By 1959, after Vanguard I had made thousands of revolutions, it was clear that the perigee was slightly more affected by the bulge south of the equator than by the bulge north of it. This meant that the Earth was a little bulgier (to the extent of about 25 feet) south of the equator than north.
The shape of the Earth was, in this way, more accurately determined than would have been possible by any reasonable Earth-bound observations. This was an indication of the way we could learn more about the Earth itself by going out into space.
EThe Bulge of the Earth
1735 A.D.
FRANCE
Newton had suggested that, on the basis of his gravitational theory, the Earth ought to be an oblate spheroid and have an equatorial bulge, because it was rotating. Plans were now being made to check this prediction by actual measurement.
If the polar regions were slightly flattened and the equatorial regions were slightly bulging, a degree of latitude near the poles should be slightly greater in mileage than a degree of latitude near the Equator. To see if that were so, two expeditions were sent out by the French in 1735. One, under the French geographer Charles-Marie de La Condamine (1701-1774), was sent to Peru, quite near the Equator. The other, under the French mathematician Pierre-Louis Moreau de Maupertuis (1698-1759), went to Lapland, which was about as close to the pole as Europeans could venture in those days.
The results, when finally achieved, completely supported Newton. The degree of latitude was one percent longer near the poles than near the Equator. Sea level at the Equator, we now know, is 13 miles farther from the Earth's center than sea level at the poles.
Before returning to Europe, by the way, La Condamine explored the Amazon River region. This was the first time it had been explored in depth by a European since Orellana, and La Condamine brought back the first rubber and curare to Europe.
bThe Space Shuttle
1981 A.D.
CAPE CANAVERAL, FLORIDA
Until 1981, all space vessels had been one-time operations, not reusable. It was clear that space exploration could be made more feasible if it were made less expensive by creating reusable vessels.
For that reason, the space shuttle was designed. Its purpose was to go into orbit and then return to Earth. It was not in itself designed to make spaceflight cheap; it was an expensive vessel. However, it would help engineers work out the techniques for developing a future generation of such vessels that would be cheaper.
The first shuttle flight took place on April 12, 1981, which happened, by coincidence, to be the twentieth anniversary of the first spaceflight, by Gagarin. The shuttle left and returned safely. It was the first of over a score of such flights during the next four and a half years to be carried through safely.
îSiberia
1581 A.D.
RUSSIA
Despite Russia's vast extent over eastern Europe, its long sleep under the Mongols had left it technologically backward. On Russia's western boundaries were the Swedes, the Poles, and the Germans, with none of whom Russia could compete militarily.
Toward the east, however, were vast spaces that at the moment contained no formidable enemy. This was also a cold region that would ordinarily not seem very enticing except that, as in Russia's European north, there were animals living there whose pelts, adapted to the Arctic cold, were thick and valuable.
In 1581, as Ivan IV's reign approached its end, the Stroganovs, a Russian family that had made a fortune in the fur trade, employed a Cossack named Yermak Timofievich (?-1584) to explore eastward and expand the Stroganov fur trade. Yermak conquered a Mongol kingdom east of the Urals, named Sibir. The name (Siberia in English) came to be applied to the entire northern third of Asia. This was the beginning of a process that would eventually lead the Russians to the Pacific Ocean and put an end forever to the raids of central Asian nomads against the settled regions to its south and west. @
ΘThe Sickle
6000 B.C.
EUROPE
Human beings had to invent devices that would be of help in dealing with the plants they were trying to exploit. The ripe stalks of grain would have to be cut down, and as early as 6000 B.C., sickles (from a Latin word meaning "to cut") were used for that purpose. They were essentially knives (originally of sharpened stone) at the end of sticks, which could be used to slash at the base of the stalks.
Once the stalks were cut down, the grain could be rubbed between two stones to eliminate the chaff and reduce the starch to powder. One stone would have a depression into which the grain could be poured, and the other would be rounded and could be used for grinding, impelled by muscle power. Such a hand-mill is called a quern.
WSilicon
1824 A.D.
SWEDEN
Silicon, as chemists now know, is, next to oxygen, the most common element in the Earth's crust. It is a component of most rocks, of sand, of glass.
Nevertheless, it holds on to other atoms so tightly that it is not easy to isolate. Berzelius was able to manage it, however, and in 1824 was the first to obtain elementary silicon.
σ Silver Fillings
1847 A.D.
PHILADELPHIA, PENNSYLVANIA
The American dentist Thomas Wiltberger Evans (1823-1897), who emigrated to France about 1847, introduced the use of silver amalgam for fillings in teeth whose decayed portions had been drilled away.
σThe Cranial Index
1842 A.D.
SWEDEN
German anthropologist Johann Blumenbach had divided the human species into "races," largely on the basis of skin color (see 1776). In 1842 the Swedish anatomist Anders Adolf Retzius (1796-1860) tried to make a finer division on the basis of something more subtle.
He suggested using the skull. The ratio of skull width to skull length, multiplied by 100, he called the cranial index. A cranial index of less than 80 was dolichocephalic (Greek for "long head"), while one of over 80 was brachycephalic (wide head). In this way, Europeans could be divided into Nordics (tall and dolichocephalic), Mediterraneans (short and dolichocephalic), and Alpines (short and brachycephalic).
Actually, this was not a very good system for dividing the human species into smaller groups. In fact, no really satisfactory system has been devised, and every attempt has simply encouraged racism and ethnocentricity. It is safer--and better--to stop at the fact that Homo sapiens is a single species.
╧The Shape of the Milky Way
1951 A.D.
UNIVERSITY OF CHICAGO, IL
The spiral structure of galaxies had first been described in 1845 by Irish astronomer William Parsons, Earl of Rosse (1800-1867), but the structure of our own Milky Way Galaxy remained puzzling. Living within it as we do, we naturally lack the ability to view it from without, from which point of view its structure would become obvious.
By 1951, however, astronomers could detect radio wave emissions with great delicacy, and the American astronomer William Wilson Morgan (b. 1906) could make out the characteristic radio waves of ionized hydrogen coming from particularly hot, bright stars that were themselves characteristic of the spiral arms of galaxies. When several such lines of ionized hydrogen were found coming from our galaxy, it seemed convincing evidence that the Milky Way Galaxy had spiral arms. Our galaxy was thus revealed to be a spiral galaxy much like the Andromeda Galaxy. Our Sun is located in one of these spiral arms.
'Slide Rules
1622 A.D.
ENGLAND
It was not long after the discovery of logarithms by Napier that the matter became mechanized. An English mathematician, William Oughtred (1574-1660), prepared two rulers along which logarithmic scales were laid off. By manipulating the rulers one against the other, calculations could be performed mechanically by means of logarithms.
The instrument, modified and improved, became the slide rule that scientists and engineers carried about with them constantly until it was replaced three and a half centuries later by pocket computers.
≤Solar Neutrinos
1968 A.D.
PIERRE, SOUTH DAKOTA
Neutrinos had been detected but only in the form of antineutrinos produced by nuclear fission reactors. The existence of antineutrinos made the existence of neutrinos themselves certain; still it would be useful to detect them directly.
The Sun produces its energy by the fusion of hydrogen to helium.
In the process, vast quantities of neutrinos are produced, some of which reach the Earth and a few of which would interact, under appropriate conditions, with detecting devices. This would prove their existence.
Frederick Reines, who with Cowan had first detected the antineutrino, now tried to detect neutrinos from the Sun. For the purpose, he set up a huge tank containing 100,000 gallons of tetrachlorethylene in a deep mine in South Dakota.
There was enough rock and earth above the tank to absorb all radiation from the sky other than neutrinos. The tank was then exposed to neutrinos from the Sun for several months. Each neutrino that was absorbed by a chlorine atom in the tetracholorethylene would be converted to an argon atom, which could eventually be flushed out with helium.
By 1968 evidence of the existence of solar neutrinos was definitely obtained, but there were not enough of them. Calculations seemed to show that the Sun was actually producing, at most, only one-third of the neutrinos that it ought to be producing if current theories of nuclear activity at the Sun's core were correct. This mystery of the missing neutrinos has concerned astronomers ever since.
lSunspots and Magnetism
1908 A.D.
PASADENA, CALIFORNIA
For some three centuries, astronomers had observed sunspots, counted them, noticed the manner in which they increased and decreased cyclicly in number, but knew nothing more about them than they could see. Hale, who had invented the spectroheliograph and supervised the construction of the 40-inch refractor, changed that.
In 1908 he was able to show from the spectrum of sunspots that they exhibited the Zeeman effect. That indicated that they were subjected to a strong electromagnetic field. It was the first time such a field had been detected for any astronomical object but Earth itself.
∞Scientific Societies
1560 A.D.
NAPLES, ITALY
Throughout history, scientists have usually worked alone because of the difficulty of communication. Sometimes they gathered in some particular center of learning, as in Athens, Alexandria, and Baghdad, but even then their companionship was a haphazard thing.
The coming of printing made it easier to record and publish advances, however, and the affair of Italian mathematicians Niccolo Tartaglia (1499-1557) and Geronimo Cardano (1501-1576) made it important to publish if one wanted credit. There would be value in exchanging information, then, for it would benefit all scientists in their search for reputation.
In 1560 an Italian physicist, Giambattista della Porta (1535?-1615), founded the first scientific association designed particularly for this interchange of ideas, the Academia Secretorum Naturae (Academy of the Mysteries of Nature). It was closed down by the Inquisition, which was oversensitive to any gatherings in those harsh days of religious conflict, but the idea was too good to let go, and other scientific societies were formed in time, and persisted.
These societies helped give rise to a scientific community that was as superior to an individual scientist as a phalanx or legion was to an individual soldier.
┘Sodium and Potassium
1807 A.D.
ENGLAND
By this time, some 38 substances were known that are today recognized as elements; most of them being metals. There were some substances that were known to be oxides -- combinations of oxygen with a metal -- but the combination could not be broken up and the free metal could not be isolated. None of the ordinary chemical methods used to isolate other metals would work.
It was known, however, that an electric current would break up water molecules into hydrogen and oxygen when more customary chemical methods failed. An electric current might do the same for the recalcitrant oxides.
Davy grew interested in the problem and constructed a battery with over 250 metallic plates, the strongest ever built to that time.
On October 6, 1807, he passed an electric current through molten potassium carbonate and liberated a metal, which he called potassium. The little globules of shining metal, when added to water, tore the water molecule apart as the metal eagerly recombined with oxygen, and the liberated hydrogen was heated to the point where it burst into flame. A week later, he isolated metallic sodium from sodium carbonate.
The next year, by similar methods, Davy isolated the elements barium, strontium, calcium, and magnesium. All were active elements that held on to oxygen tightly and would not have been isolated easily by non- electric techniques.
These discoveries excited the scientific world enormously and greatly stimulated research into electrochemistry.
nDomes
537 A.D.
CONSTANTINOPLE (ISTANBUL, TURKEY)
A dome is a semispherical structure on top of a building, which looks impressive in itself and gives an opportunity for vertical windows that will introduce light inside. (Skylights on a flat roof are less impressive and are a source of weakness.)
The Romans first introduced domes, placing one on the Pantheon, a building begun in 27 B.C. This was the largest dome built before modern times. It is heavy, however, and is built on a circular building, with no openings except one at the very top, so its esthetic appeal is limited.
About 480 architects in the East Roman Empire perfected a system of placing a hemispherical dome upon a square support in such a way that the bottom of the dome could be pierced by many windows without sacrificing its strength.
This discovery was given its chance when the East Roman Emperor Justinian (who reigned from 527 to 565) decided to rebuild the church of Hagia Sophia after its destruction during a period of rioting. The ruins were cleared, a larger area was marked off, and for six years, 10,000 laborers worked on it. The large dome was so cleverly designed, so skillfully pierced with windows, that the whole interior of the church -- 108 feet across and 180 feet high -- was bathed in sunlight. The enormous dome, as seen from below, seemed to have no support at all but to be suspended from heaven.
qSolar Composition
1929 A.D.
STOCKHOLM, SWEDEN
Ångström had demonstrated the existence of hydrogen in the Sun two-thirds of a century before. It was not till 1929, however, that the Solar spectrum was used to give a fairly detailed picture of the overall composition of the Sun. Russell, who had earlier helped work out the matter of the Main Sequence, showed that the Sun consisted almost entirely of hydrogen and helium, in a 3-to-1 mass ratio. The most important of the minor components were oxygen, nitrogen, neon, and carbon. (This turned out to be similar to the composition of the Universe as a whole, as nearly as astronomers can determine.)
ƒSolar Energy
1929 A.D.
WASHINGTON, D.C.
Three-quarters of a century before, Helmholtz had suggested that the Sun obtained its energy from gravitationally induced shrinkage. This had given an impossibly small age for the Earth, but no suitable substitute source of energy had been found until the existence of nuclear energy was demonstrated by Pierre Curie. Then it seemed very likely that some sort of nuclear reaction was the solar power source.
In 1929 the Russian-born American physicist George Gamow (1904-1968) suggested that the nuclear source was the conversion of hydrogen nuclei into helium nuclei, since these two elements made up nearly all the Sun, as Russell had shown. As four hydrogen nuclei had to fuse together to form one helium nucleus, this process was called nuclear fusion, or more specifically, hydrogen fusion.
However, not enough was known about nuclear fusion as yet for Gamow to flesh out his suggestion in detail.
üSolar Prominences
1860 A.D.
SPAIN
Photography of astronomical phenomena was becoming more common. In 1858 the English astronomer Warren De la Rue (1815-1889) had devised a telescope that was particularly adapted to taking photographs of the Sun. After that, solar photography became an almost daily routine for him.
In 1860 he traveled to Spain to observe a total eclipse of the Sun. The photograph he took of the Sun during the eclipse showed gouts of flame about its edge. These were called solar prominences and, like solar flares, were evidence of violent activity on the Sun. This was the first astronomical discovery to be made as the result of photography.
`Our Stable Solar System
1799 A.D.
FRANCE
In 1799 French scientist Pierre-Simon de Laplace published the first volume of a monumental five-volume work called Celestial Mechanics, in which the gravitational influences on the various bodies of the Solar System were taken up in detail.
Although the Sun dominates the system, and the planets move about the Sun in stately ellipses, each planet pulls at the others, and so do the satellites. These small additional pulls introduce minor variations in the movement of the planetary bodies, called perturbations, and it was considered that they might gradually increase in size over time so that the Solar System would prove unstable in the long run.
Laplace showed that this was not the case. The perturbations are periodic and vary on either side of what would exist if the Sun alone had a gravitational pull. The Solar System, then, is stable.
ÅThe Solar Wind
1959 A.D.
EARTH
It had been recognized for some time that solar flares were highly energetic phenomena on the surface of the Sun. Occasionally, when a solar flare appeared on the solar surface, it was followed, after the lapse of some days, by a magnetic storm on Earth. Something was apparently emitted by the flares that eventually reached Earth.
The American physicist Eugene Newman Parker (b. 1927) had argued the year before that the Sun constantly emitted charged particles in every direction and that these drifted outward through the Solar System, passing Earth. He called them the solar wind.
A solar flare might therefore be the source of an unusually large gust of such particles, which on arriving at Earth would intensify the usual effects of the solar wind.
The existence of the solar wind was verified by Lunik II and Lunik III on their way toward the Moon in 1959, and later probes did the same.
╟Solar X Rays
1958 A.D.
U.S.A.
The firing of rockets beyond the atmosphere made it possible to detect X-rays coming from astronomical objects. Such X-rays could not be detected from Earth's surface, because the Earth's atmosphere absorbed them.
In 1958 the American astronomer Herbert Friedman (b. 1916) observed the Sun during a total eclipse, by means of rocket-borne instruments, and detected X rays coming from the Sun's corona.
Two years before, he had shown that solar flares emitted X-rays, but that was not surprising in view of the fact that flares were clearly very energetic solar explosions. X-rays from the apparently quiet corona were more surprising, but this supported the claim of the Swedish physicist Bengt Edlen (b. 1906), who in 1940, as a result of studying the ultraviolet radiation from the Sun, had claimed that the corona must have a temperature of a million degrees or so.
This does not mean that the Solar corona is a great reservoir of heat. It is a volume of extraordinarily thin gas, where the individual atoms have a great deal of heat individually (hence the temperature), but where there are so few atoms that the total heat over the entire corona is not as great as the temperature indicates -- by far.
╔Solar Flares
1859 A.D.
LONDON, ENGLAND
The British astronomer Richard Christopher Carrington (1826-1875) measured the Sun's rotation by the motion of the sunspots. Galileo had done that two and a half centuries before, but Carrington could work with more delicate instruments. He found that the Sun did not rotate all in a piece, which meant that it was not a solid body, but that the outer regions, at least, might well be gaseous. (In view of the temperature of the Sun's surface, this was not surprising.) A point on the solar equator took 25 days to make one turn around the Sun, while at solar latitude 45 degrees, a point that had to travel a considerably smaller distance to make the turn, it took 27-1/2 days.
On September 1, 1859, Carrington, watching the sunspots, observed a starlike point of light burst out of the Sun's surface. It lasted 5 minutes and subsided.
Carrington speculated that a large meteor had fallen into the Sun, but it was eventually realized that he had been the first to see a solar flare, a brief but violent explosion that was usually associated with sunspots. This was the beginning of an understanding that when the number of sunspots was high, we had an "active Sun" and when it was low, a "quiet Sun."
└Sonar
1917 A.D.
FRANCE
Pierre Curie, in discovering piezoelectricity, had shown how to produce ultrasonic sound vibrations. These were put to use by the French physicist Paul Langevin (1872-1946).
Waves are more easily reflected the shorter their length. Ordinary sound waves are long enough to bend around ordinary obstacles and are not efficiently reflected. The much shorter sound waves of ultrasonic vibration can easily be reflected by relatively small objects. The direction from which the reflection is received indicates the direction of the object, and the time it takes between emission and reflection (knowing the speed of sound) gives the distance, or range, of the object.
Since light cannot penetrate large thicknesses of water and ultrasonic vibrations can, the latter can be used to detect underwater objects such as submarines when light is impotent. Since World War I was raging and German submarines were a deadly danger to the Allies, it is not surprising that Langevin worked with that purpose in mind.
Langevin's system of echolocation was called sonar, an acronym (combination of initial letters) of sound navigation and ranging. While Langevin had the technique worked out in 1917, it could not be put into effective use before the end of the war.
Sonar is now used not only for the detection of underwater objects such as submarines and schools of fish, but also to study the conformation of the ocean floor. Sonar utterly revolutionized oceanography.
░The South Pole
1911 A.D.
SOUTH POLE
Peary's attainment of the North Pole sharpened the race to reach the South Pole. This was a more difficult objective, for the South Pole was more distant from important population centers, and it was at the center of a landmass, so that it was considerably colder than the North Pole.
The Norwegian explorer Roald Amundsen (1872-1928) had already made his way by sea across the northern border of North America in 1903 (achieving the Northwest Passage at last). Now he prepared for a race to the South Pole.
In October 1911 he set off, with dogs (who could eat meat -- and each other, in case of need), reaching the South Pole on December 14 and returning safely.
The British explorer Robert Falcon Scott (1868-1912) was also trying to reach the pole, but he didn't plan his expedition as well. He ran into enormous misfortune, reached the South Pole a month after Amundsen did, and perished with his party on the way back.
SThe South Sea
1513 A.D.
PACIFIC OCEAN
Columbus had reached the coast of what we now call the Isthmus of Panama in his final voyage, and Spanish settlers arrived soon after. One of the leading settlers was Vasco Nuñez de Balboa (1475-1519).
At that time, those Spaniards who thought they were in Asia kept looking for the vast wealth that Marco Polo had talked about, and gold was a particularly concentrated form of wealth, one they particularly lusted for.
Balboa heard rumors of gold to the west and he organized an expedition to find it. Panama, however, is a narrow isthmus and you can't wander far in it without striking the other coast. Balboa's expedition left on September 1, 1513, and on September 25, he climbed a hill and found himself staring at the limitless expanse of what seemed to be an ocean. Since the coasts of Panama run east-west and the Atlantic Ocean is on the north shore, Balboa named the new ocean on the south shore the South Sea.
Balboa probably did not realize that this was the second ocean Vespucius had referred to, the one that lay between the American continents and Asia -- but it was.
ÇThe Space Station
1971 A.D.
MOSCOW, USSR
On April 19, 1971, the Soviet Union placed Salyut 1 in orbit. It was the prototype of a space station intended for long-time habitation by relay teams of cosmonauts.
In July, however, three Soviet cosmonauts were found dead on board when the rocket Soyuz 11 returned to Earth, because of loss of air from the cabin. It was the worst space disaster up to that point.
¼Walking in Space
1965 A.D.
MOSCOW, USSR
In 1965 human beings were able to leave their orbiting rockets and, held by a tether, remain free in space -- within their spacesuits, of course. This was referred to as a spacewalk.
The first to take a spacewalk was the Soviet cosmonaut Aleksei Leonov, who left the rocket ship Voskhod II on March 18, 1965. The American astronaut Edward Higgins White II (1930-1967) left his ship, Gemini 4, on June 3, 1965.
:Space-Time
1907 A.D.
GERMANY
Einstein's theory of special relativity forced many physicists to reconsider their view of the Universe. It was clear from Einstein's work that an ordinary three-dimensional view of the Universe was insufficient.
The Russian-born German mathematician Hermann Minkowski (1864-1909) published Time and Space in 1907. In it he demonstrated that relativity made it necessary to take time into account as a kind of fourth dimension (treated mathematically somewhat differently from the three spatial dimensions).
Neither space nor time had existed separately, in Minkowski's view, so that the Universe consisted of a fused space-time.
Einstein adopted this notion as he continued to work on his theories. He was trying to extend them to accelerated motion in order to take gravitational interactions into account.
╒Space Flight
1903 A.D.
RUSSIA
Oddly enough, in the same year that air flight became a reality, space flight began to receive true scientific attention.
In 1903 a Russian physicist, Konstantin Eduardovich Tsiolkovsky (1857-1935), began a series of articles for an aviation magazine in which he went into the theory of rocketry quite thoroughly. He wrote of space suits, satellites, and the colonization of the solar system. He was the first to suggest the possibility of a space station.
ÿExamining Solar Chemistry
1890 A.D.
U.S.A.
For three-quarters of a century, the solar spectrum had been studied in increasing detail, but always the Sun had been photographed by light from the entire spectrum.
In 1890 an American astronomer, George Ellery Hale (1868-1938), perfected and put into use the spectroheliograph, a device that made it possible to photograph the light of a small band of wavelengths of the Sun. Thus he was able to photograph the wavelengths around a line emitted by calcium and the result was a clear indication of the distribution of calcium in the solar atmosphere. It now became possible to study the chemistry of the Sun's outermost layer in considerable detail.
╒Michelson's Speed of Light
1882 A.D.
U.S.A.
Since Jean Foucault's determination of the speed of light, no one had succeeded in bettering the figure.
However, Michelson, the inventor of the interferometer, measured the speed of light in 1882 and reported it to be 186,320 miles per second. This was over a thousand miles per second faster than Foucault had reported, and Michelson's value was the more accurate. In fact, it was less than 40 miles per second above the value that is currently accepted.
gSpectral Lines
1814 A.D.
GERMANY
Since Newton had first studied the spectrum, nothing much had followed. Wollaston in 1802 had observed a few dark lines in the spectrum but had supposed them to be boundary lines between the colors and had not followed up on the matter.
Meanwhile a German physicist, Joseph von Fraunhofer (1787-1826), was meticulously manufacturing the best lenses and prisms yet made. In 1814 he was testing one by sending sunlight through a narrow slit and then through the prism. In effect, he produced innumerable lines of light, each an image of the slit and each containing a very narrow band of wavelengths. Some wavelengths were missing, however, so that the slit images at those particular wavelengths were dark. The result was that the solar spectrum was crossed by dark lines.
In theory, these should always have been visible, even to Newton, but if the prism was somewhat imperfect and the slit too wide, there would be enough fuzziness to obscure them. Where Newton had reported none and Wollaston seven, Fraunhofer, with his excellent instrument, detected nearly 600 lines.
Fraunhofer went on to measure the position of the more prominent lines, which he marked off with letters from A to K, and showed that they always fell in the same portion of the spectrum, whether the light came directly from the Sun or was reflected from the Moon or planets. Eventually he mapped the wavelengths of several hundred of these Fraunhofer lines, as they were called.
Not much was done with these spectral lines for the next half-century, but eventually they proved to be major items in the research armory of chemists and astronomers.
cSpectral Lines and Elements
1859 A.D.
GERMANY
Since their discovery by German physicist Joseph von Fraunhofer (1787 - 1826) nearly half a century before, spectral lines had not been connected with chemistry.
The German physicist Gustav Robert Kirchhoff (1824-1887), however, had carefully studied the spectra of light produced when various elements were heated to incandescence. He found that each element produced light of only certain wavelengths, so that the spectrum consisted sometimes of only a few lines of light, which were sometimes well separated.
In 1859 Kirchhoff announced that every element produced characteristic spectral lines, which it also absorbed when its vapors were cooler than the light source. The pattern of lines was different for each element; no two elements shared spectral lines in exactly the same positions. In essence, each element had a spectral "fingerprint." This meant that if any sample of ore, on being heated to incandescence, produced even a single spectral line in a position not recorded for any known element, then some new element must be present in that ore.
Making use of such spectroscopic data, Kirchhoff discovered cesium in 1860. The name is derived from the Latin word for "sky-blue," since that was the color of the spectral line that had given away cesium's existence. The next year Kirchhoff discovered rubidium, a related element, its name coming from the Latin for "red." Kirchhoff also pointed out that the dark lines in the solar spectrum were the result of light being absorbed by the gases in the relatively cool atmosphere of the Sun. From those lines, one could be sure that sodium existed in the Sun's atmosphere, and half a dozen other elements as well.
This was the first actual observation indicating that the same chemical elements that existed on Earth existed also on other astronomical bodies, and therefore presumably throughout the Universe.
òFoucault's Speed of Light
1849 A.D.
PARIS, FRANCE
Roemer and Bradley had both determined the speed of light by astronomical methods. But until 1849 no one had been able to determine the speed of light by setting up an earthbound experiment. In that year, Fizeau set up a rapidly turning toothed disk on one hilltop and a mirror on another, 5 miles away. Light passed through a gap between the teeth of the disk to the mirror and was reflected. By that time, a tooth had moved into the way and the reflection could not be seen. If the disk turned rapidly enough, the reflected light passed through the next gap and could be seen again.
From the speed of revolution required for the reflection to become visible, the time required for light to travel 10 miles could be calculated.
Fizeau's assistant, the French physicist Jean-Bernard-Léon Foucault (1819-1868), improved the technique the next year. Instead of using a toothed wheel, Foucault used two mirrors, one of which was rotating rapidly.
Light would be reflected from the stationary mirror to the rotating one. The rotating mirror would have turned slightly in the time it took light to travel to it and would reflect that light slightly to one side as a result. From the amount of deflection, the speed of light could be calculated. Foucault's best figure for the speed of light was 185,000 miles per second. It was lower than the true value, but only by about 0.7 percent.
Foucault's method was so delicate that he only needed to let the light travel 66 feet. With only that distance to worry about, he could have it travel through water, and did. He found out that, through water, light traveled at only three-fourths its velocity through air. It turned out that the speed of light through any transparent medium is equal to the speed of light in a vacuum, divided by the index of refraction of the medium. (The index of refraction of a medium is a measure of the extent to which it will bend a light ray.)
ⁿEvenson's Speed of Light
1972 A.D.
BOULDER, COLORADO
The first useful approximation of the speed of light had been made by Olaus Roemer. Since then, measurements had become more and more precise, culminating for a while in Michelson's measurements.
In October 1972, however, a research team headed by Kenneth M. Evenson, working with a chain of laser beams in Boulder, Colorado, obtained a figure for the speed of light that was far more precise than anything previously reached.
He measured the speed as 186,282.3959 miles per second.
tMichelson's Speed of Light
1927 A.D.
CALIFORNIA MOUNTAINS
In his last years, Michelson, who had performed the fateful Michelson-Morley experiment, grew interested in measuring the speed of light with new precision. In the California mountains, he surveyed a 22-mile distance between two mountain peaks to an accuracy of less than an inch. He made use of a special eight-sided revolving mirror to reflect a light beam in the fashion used by Foucault.
In 1927 he obtained a value of 199,798 kilometers per second for the speed of light. This was only about 6 kilometers per second faster than the figure determined nowadays by much more sophisticated equipment.
ΣRoemer's Speed of Light
1675 A.D.
DENMARK
At this time, nobody knew how quickly light traveled. Galileo Galilei (1564-1642) had tried to measure it by standing on top of one hill and having a friend stand on top of another, each with dark lanterns. Galileo would reveal the flame in his lantern and at once his friend would reveal the flame in his. The time it took between Galileo's sending the light and seeing the return light would be the time it took light to make the round trip. However, the time was always the same, no matter how far apart the hills were, and Galileo realized that he was just measuring his friend's reaction time and gave up. Light obviously moved too swiftly for its speed to be measured in that way. (There were those who thought it moved with infinite speed.)
In 1675, however, a Danish astronomer, Olaus Roemer (1644-1710), was carefully observing the motions of Jupiter's satellites from the Paris Observatory, including the time when they passed behind Jupiter and were eclipsed. Italian born French astronomer Gian Cassini (1625-1712) had timed those motions carefully and Roemer was checking them. To Roemer's surprise, he found that the eclipses came progressively earlier at those times of the year when Earth was approaching Jupiter in its orbit and progressively later when Earth was receding from Jupiter.
Roemer supposed this might be because light did not travel at infinite speeds but took longer to go from Jupiter to Earth when Earth was on the opposite side of the Sun from Jupiter, and less time when Earth was on the same side. From these time differences, Roemer calculated that light must travel at a speed of about 141,000 miles per second. This is only about three-fourths of its actual speed, but for a first determination it's not bad.
▐A Union of Sperm and Egg
1875 A.D.
GERMANY
Egg cells and sperm cells were both known, and it was clear that the birth of young required a union of the two. Nevertheless, such a union was not observed until the German embryologist Oskar Wilhelm August Hertwig (1849-1922) saw a sperm cell actually enter the egg cell of a sea urchin.
What's more, although sperm cells are produced in swarming plenty, Hertwig could see that but a single sperm cell entered the egg cell and that it sufficed for fertilization.
ûThe Spherical Earth
350 B.C.
EARTH
Anyone looking at the Earth can see that the land surface is bumpy and uneven but on the whole flat. This is particularly true if we look out over the surface of a lake.
The first person we know of who seems to have suggested that the Earth was not flat but spherical was Pythagoras. It was Aristotle, however, who summarized the reasons, possibly about 350 B.C., reasons that still hold today.
As one moves north, stars rise above the northern horizon and sink below the southern horizon, while as one moves south, the reverse happens. The shadow of the Earth on the Moon during a lunar eclipse is always a circular arc. When ships sail away from you at sea, the hull always seems to disappear before the superstructure, and this happens in the same way in any direction. All these indicate the Earth to be spherical.
These arguments were accepted by educated people even at low points in intellectual history, yet there are people today, with an education of sorts, who cling to something equivalent to a Flat-Earth Society. This, of all antiscience movements, seems the most indefensible, and one suspects that they are either joking or just a little mad.
GNaming the Invertebrates
1801 A.D.
FRANCE
Swedish scientist Carolus Linnaeus (1707-1778) and others in the past three-quarters of a century had elaborated the taxonomy of vertebrates (those animals with backbones -- mammals, birds, reptiles, amphibia, and fish) in considerable detail.
The less familiar and more diverse animals without backbones (invertebrates) were less carefully considered. Linnaeus had lumped them all into the class Vermes (Latin for "worms").
The French naturalist Jean-Baptiste de Lamarck (1744-1829) tackled the problem in publications beginning in 1801. He divided the invertebrates into groups and created such divisions as the crustaceans (crabs and lobsters) and echinoderms (starfish and sea urchins). He distinguished between the eight- legged arachnids (spiders and scorpions) and the six-legged insects. In fact, Lamarck was the first to use the terms vertebrate and invertebrate, and he popularized the term biology for the study of life.
In founding the modern science of invertebrate zoology, Lamarck began the process of understanding the importance of invertebrate life. All the vertebrates are included in but a single phylum, while there are about 22 phyla of invertebrates. The number of species of insects alone far exceeds the number of species of vertebrates; indeed, it exceeds the number of species of all other animals combined.
?The Spinal Cord
180 A.D.
GREECE
A Greek physician, Galen (129-ca. 199), worked at a gladiatorial school at Pergamum, the city of his birth, and there was able to gain some rough-and-ready hints on human anatomy. In Rome, from 161 on, he could dissect only animals, which misled him now and then as far as human anatomy was concerned.
Nevertheless, he did good work on muscles, identifying many for the first time, and showed that they worked in groups. He also showed the importance of the spinal cord by cutting it at various levels in animals and noting the extent of the resulting paralysis.
fSpinning Wheels
1200 A.D.
ENGLAND
For thousands of years, fibers had been spun into thread by the action of the hand: the fiber was held on a distaff and was twisted into yarn by turning a spindle. It was a slow, painstaking process that thoroughly occupied much of the time of the females of a household. (It was "women's work" par excellence, and the females of a family are still referred to jocularly as "the distaff side.")
In India the process had eventually been mechanized: a foot-powered treadle turned a large wheel that twisted the spindle. Such a spinning wheel greatly hastened the work of spinning thread out of fiber. About 1298 the spinning wheel made its way into Europe.
The wheel and the spindle were connected by a belt, the first example of a belt drive in machinery. The spinning wheel was also one of the first important mechanical means of lightening women's work.
█Light Changing Conduction
1954 A.D.
BARSTOW, CALIFORNIA
Eighty years ago, it was discovered that the element selenium could conduct an electric current much more easily in the light than in the dark. It was eventually realized that the energy of sunlight knocked electrons loose from the selenium atoms, and it was those electrons that carried the current.
Selenium came to be used for small jobs. Thus a beam of light shone across a doorway into a selenium receiver and an electric current flowed that kept a door closed against the pull of a spring. If an approaching object interrupted the beam of light, the darkened selenium ceased conducting electricity and the door swung open. The device, popularly known as an electric eye, is more properly called a photoelectric or photovoltaic cell.
Selenium is not suitable for heavy jobs, as it is extremely inefficient, turning less than 1 percent of the energy of sunlight into electricity.
In 1954, however, photovoltaic cells were devised that made use of semiconductors of the type used in transistors. Light kicked electrons out of place much more efficiently in their case; they turned about 4 percent of the sunlight into electricity. At that level, photovoltaic cells could also be referred to as solar batteries.
ªDisproving Vitalism
1860 A.D.
FRANCE
Pasteur now took up the matter of spontaneous generation. It was already clear that nutrient broth that had been strongly heated till all microorganisms within it were dead would not develop microorganisms if it were sealed away from air. Vitalists, however, maintained that the heating destroyed some vital principle in the air.
Pasteur had shown that dust in the air carried microorganisms. In 1860, he therefore boiled meat extract and then left it in a flask exposed to air, but only by way of a long narrow neck that was bent down, then up. Although unheated air could thus freely penetrate into the flask, dust particles settled to the bottom of the curved neck and did not enter the flask. The meat extract did not spoil. No decay took place. No organisms developed. There was no question now of a destroyed vital principle. When Pasteur knocked the neck off the flask, microorganisms developed in the meat extract at once.
That was the final destruction of the notion of spontaneous generation -- at least under present conditions.
Darwin's theory of evolution, however, had opened the question as regards the past. If species had evolved, might there not have been a time when life itself evolved from nonliving precursors? This was a most uneasy thought to those who had always assumed life to be a creation of God, but Darwin himself had raised the possibility -- and that possibility has concerned science ever since.
₧The Soviet Space Program
1957 A.D.
MOSCOW, USSR
Nearly three centuries before, English scientist Isaac Newton had pointed out how a rocket could put a vehicle into orbit around the Earth. After Germany had developed the V-2 rocket during World War II, both the United States and the Soviet Union began to think of placing a rocket in orbit. It was naturally taken for granted by all Americans that the United States, with its advanced technology, would be first in the field.
It came as an enormous shock to the United States then, when on October 4, 1957, the first satellite went into orbit -- and was Soviet. It was called Sputnik I (the Russian word for "satellite"), and it began the Space Age.
ªSunspots and the Earth
1852 A.D.
ENGLAND
The British physicist Edward Sabine (1788-1883) showed, in 1852, that the frequency of disturbances in Earth's magnetic field paralleled the increase and decrease of sunspots on the Sun. This was the first example of a linkage between Earth and Sun involving something other than the Sun's radiation of light and heat or its gravitational pull. It was also the first hint that sunspots had magnetic properties.
╧Stagecoaches
1620 A.D.
U.S.A.
A stagecoach is any horse and carriage that travels between set places (stages) according to a fixed timetable and accepts passengers for pay. Such things came into use at about this time.
Stagecoaches allowed people without money enough to own a horse to be carried from one place to another more quickly than in any other way. There were disadvantages, of course. You had to ride with strangers, at a time and to a place that suited the coach-owners and not necessarily yourself. Nevertheless, it was much more convenient than having to walk or try to hitch a ride in a farmer's cart.
The stagecoach remained the fastest means of overland travel (for the relatively impecunious) for over two centuries.
óThe Germ Theory of Disease
1862 A.D.
PARIS, FRANCE
More and more biologists were coming to suspect that contagious diseases were caused by microorganisms.
In 1862 French chemist Louis Pasteur took up the matter and issued a publication that gathered all the evidence. His prestige was such that the germ theory of disease then had to be taken seriously. There is no question but that this was the most important single advance in the history of medicine.
Using the theory, Pasteur, and others as well, located the specific microorganisms that caused certain diseases and could then work out logical ways of preventing the disease in the first place or of curing it once it struck.
This was the beginning of modern medicine. It led to a fall in the death rate, a doubling in life expectancy, and an accelerated population explosion that has more than tripled world population since Pasteur's time and presented humanity with enormous problems in consequence.
>The Birth of Stars
1955 A.D.
WASHINGTON, D.C.
The more massive a star, the brighter it is, the more rapidly it consumes its nuclear fuel, and the shorter its life on the main sequence. The Sun came into being as a star only 4.5 billion years ago, some 10 billion years after the Universe itself came into being, and will remain on the main sequence only five or six billion years more.
Stars that are much more massive than the Sun can have lifetimes on the main sequence of less than a billion years, perhaps even only several million. Such stars that are still on the main sequence now must have been formed less than a billion years ago, or perhaps only a few million years ago. This leads to the thought that there may well be interstellar clouds out of which stars are forming right now.
For instance, there are reasons for thinking that the Orion nebula is an active star-former right now. In 1955 the American astronomer George Howard Herbig (b. 1920) detected two stars in the Orion nebula that had not been seen a few years earlier. This means we may have witnessed the actual birth of these stars.
≈Hipparchus's Star Map
134 B.C.
GREECE
In 134 B.C. Hipparchus observed a star in the constellation Scorpio of which he could find no record in previous observations. This was a serious matter, for the heavens were supposed to be eternal and changeless. Was it really a new star, or had Hipparchus simply overlooked it earlier?
Hipparchus determined to prepare a star map so that from then on any astronomer sighting a star that seemed new could check it against the map. In order to make his map, he plotted the position of each star according to its latitude and longitude, as Eudoxus had done. Hipparchus included over a thousand stars, and both in quantity and in accuracy it was a far better map than anything attempted before. What's more, it occurred to Hipparchus to transfer the system of latitude and longitude to maps of the Earth. That has been done ever since.
In the course of preparing his map, Hipparchus compared the locations of stars with those recorded by earlier astronomers and discovered a uniform shift of all the stars from west to east, at a rate that would bring them completely around the sky in 26,700 years. Because it meant that the vernal equinox came a bit ahead of its previous mark each year, this motion was called the precession of the equinoxes.
Perhaps it was about this time, too, that Hipparchus divided the stars into classes, later called magnitudes. The brightest 20 were of the first magnitude; those somewhat dimmer were second magnitude, and so on, until sixth magnitude stars were just barely visible.
ΣEudoxus' Star Maps
350 B.C.
GREECE
The Greek mathematician Eudoxus (ca. 400-ca. 350 B.C.), perhaps about 350 B.C., drew a better map of the Earth than Hecataeus had managed, and was the first to attempt a map of the sky.
The sky was more difficult to map than the Earth was. On Earth there were physical landmarks: coastlines, rivers, mountain ranges, and so on. In the sky there were only stars.
The reasonable thing to do was to create landmarks, so Eudoxus drew imaginary lines diverging out from the pole star, and other imaginary lines meeting the first set at right angles. The diverging lines are what we now call longitude, and the ones at right angles are latitude. In this way Eudoxus could locate stars unmistakably in the otherwise featureless sky.
}Generating Better Static
1706 A.D.
ENGLAND
Guericke's ball of sulfur was not an extremely efficient static- electricity generator. In 1706, however, the English physicist Francis Hauksbee (ca. 1666-1713) constructed a glass sphere turned by a crank, which, through friction, could build up a more intense electric charge than sulfur could. This greatly stimulated further experimentation with static electricity.
∙Static Electricity
1660 A.D.
MAGDEBURG, GERMANY
When Greek philosopher Thales (624-546 B.C.) studied the magnetic properties of loadstone, he is also supposed to have studied amber, which, when rubbed, attracts light objects. Whereas magnets attract only iron, rubbed amber attracts many things.
English physicist William Gilbert (1544-1603), who showed that Earth was a magnet, found that rock crystal and a variety of gems showed the same attractive force when rubbed that amber did. Since the Greek word for amber was elektron, Gilbert called these substances electrics, and the phenomenon came to be called electricity. Because the electricity in electrics seemed to stay put if left undisturbed, it was referred to eventually as static electricity, from a Greek word meaning "to stand."
The first to demonstrate static electricity on a large scale was German physicist Otto von Guericke (1602-1686), who had invented the air pump. The electrical phenomenon was produced by rubbing, and Guericke in 1660 fashioned a globe of sulfur that could be rotated on a crank-turned shaft. When it was stroked with the hand as it rotated, it accumulated quite a lot of static electricity. It could be discharged and recharged indefinitely, and Guericke could produce sparks from his electrified globe.
⌠Steam Locomotives
1825 A.D.
ENGLAND
Richard Trevithick had failed in his attempt to make a commercial success of the steam locomotive. Another English inventor, George Stephenson (1781-1848), took advantage of improved steam engines, however, and was able to build a steam locomotive that worked adequately.
On September 17, 1825, one of his locomotives pulled 38 cars at speeds of 12 to 16 miles an hour. For the first time in the history of the world, land transportation at a rate faster than that of a galloping horse was clearly on the way to becoming possible.
Railroads quickly began to knit nations together. It might be argued that a nation like the United States could not have been held together but for the fact that railroads made all parts reasonably accessible.
Making Steel
1856 A.D.
LONDON, ENGLAND
For more than 3,000 years, steel had been known to be the strongest metal, but manufacturing steel was a difficult process. First, iron came out of the smelting furnace with a great deal of carbon in it (from the charcoal or coke used to smelt it). This cast iron was hard but brittle. The carbon could be removed and pure iron (wrought iron) left behind. This was tough but too soft. Then finally, just the right amount of carbon could be added to form steel, which was both tough and hard. By then, steel was expensive.
The British metallurgist Henry Bessemer (1813-1898) sought a way of removing the carbon from cast iron more cheaply. In the old way, the carbon was burned off by oxygen from additional iron ore while the mixture was strongly heated. Bessemer wondered if the oxygen could not be supplied more simply by sending a blast of air through the molten iron. It might seem that the blast would cool the iron and spoil everything, but the combination of oxygen from the air and carbon in the iron actually heated the mix. By stopping the process at the point where the carbon level was right, Bessemer got his steel directly.
In 1856 Bessemer announced his discovery, and such blast furnaces began to be built. It took a while for the method to be perfected because it required phosphorus-free iron ore, something the steel manufacturers didn't understand. Eventually, however, the bugs were worked out and the era of cheap steel began. Steel, together with elevators, helped build the cities of the next century.
uDescribing AC
1893 A.D.
U.S.A.
Tesla had made alternating current useful. By 1893 a German-born American electrical engineer, Charles Proteus Steinmetz (1865-1923), worked out the intricacies of alternating current circuitry in complete mathematical detail, making use of complex numbers.
This made it possible to design alternating current equipment with increased efficiency. Steinmetz's mathematics spread among the electrical engineering profession and completed the victory of alternating current over direct current. (The house current we draw on whenever we plug an electrical device into a wall socket is invariably alternating current.)
The Stellar Diameter
1920 A.D.
PASADENA, CALIFORNIA
Throughout history, stars had been studied only as points of light, and all information about them had to be obtained in ways that required only points.
In 1920, however, Michelson, who had first used his interferometer to compare the speed of light in different directions, used it for another purpose. He built a 20-foot interferometer and attached it to the new 100-inch telescope. With it, he could measure light emerging from either side of the star Betelgeuse. (Betelgeuse is a relatively near red giant, so that its diameter was likely to prove more measurable than that of smaller or more distant stars.) The two rays from the sides of Betelgeuse made a very tiny angle, but from the interference fringes they produced, Michelson could measure the angle, and from that angle, knowing the distance of Betelgeuse, he could calculate its diameter. He worked it out to be about 260 million miles, or 300 times the width of our Sun.
It was news that made the first page of the New York Times.
Steroid Synthesis
1951 A.D.
U.S.A.
Woodward, who had made it his business to synthesize the most complex of naturally occurring organic molecules, achieved the synthesis of cholesterol and cortisone in 1951. These were both steroids, with molecules possessing a characteristic four-ring structure.
▐The Stethoscope
1816 A.D.
FRANCE
Diagnostic procedures were limited in the early days of modern medicine, but one obvious way of getting information was to place the ear to the chest wall and listen to the sound of the heartbeat. In 1816 a French physician, René-Théophile-Hyacinthe Laënnec (1781-1826), was faced with the necessity of listening to the heartbeat of a plump young woman with a heart condition. He felt that trying to hear the heart through the barrier of the breasts would be ineffective, while attempting to lift or separate the breasts for better hearing would be indelicate.
In a moment of inspiration, he bent a notebook into a cylinder and put one end between the woman's breasts and the other end to his ear. He was pleased to find that the heart sounds were actually louder than they would have been if he had placed his ear directly to the breastbone. He therefore prepared wooden cylinders for the purpose of listening to the heartbeat and thus invented the stethoscope (from Greek words meaning "to view the chest").
The stethoscope, steadily improved, of course, became so essential an adjunct of the medical profession that medical students with their stethoscopes became as stereotypical as engineering students with their slide rules.
Stirrups
300 A.D.
INDIA
The Greeks and Romans relied on infantry. Stolid, well-trained foot soldiers, whether organized into a phalanx or a legion, could withstand horsemen, so that the cavalry was reduced to auxiliary importance in Greek and Roman times. Cavalry could charge in an attempt to panic the enemy, and could chase the enemy once a panic had set it, and could fight each other, but cavalry rarely decided a battle.
The horse and chariot had faded in importance as a larger horse was bred capable of running with the full weight of an armed soldier on its back. Saddles made it easier to sit on a horse's bony spine, but riding was still precarious, and thrusting with a spear was dangerous, for if the thrust was parried the rider might easily be pushed off the horse. It was safer to shoot arrows from a distance.
In India, about 100 B.C., the notion arose of having a leather loop suspended from the saddle, into which the big toes could be thrust in order to steady the rider. The Chinese, living in a colder climate and wearing shoes, needed a wider loop into which the whole shoe might be thrust. By 300, such stirrups (from an old Teutonic word meaning "climbing rope," because they could be used to hoist oneself up on a tall horse) were made of metal and were wide enough to allow the foot to withdraw quickly in case of need.
The stirrup made it possible for a rider to sit firmly in the saddle and strike at an enemy with spear or sword. From the Chinese, the notion of the metal stirrup spread to the central-Asian nomads and from there westward.
`Steamships
1819 A.D.
SAVANNAH, GEORGIA
The steamboats designed and built by John Fitch and later by Robert Fulton were designed for river travel. Rivers are, after all, gentler than the open sea, and banks are always close at hand in case of accident.
In 1819, however, the American steamship Savannah (an ocean-going vessel is a ship, not a boat), sailed from Savannah, Georgia, to Liverpool, England, in five and a half weeks. It was not much of a steamship, for it bore sails that did the major work, while the steam engine on board was at work only one-twelfth of the time. Still, it bore the promise of things to come.
fThe Steam Engine
1781 A.D.
SCOTLAND
Since Watt had thought of having a hot and a cold chamber in a steam engine, he kept introducing improvements. He arranged to have the steam push into a chamber on each side of the piston alternately so that it would be pushed rapidly in both directions rather than in only one.
In 1781 he devised mechanical attachments that ingeniously converted the back-and-forth movement of a piston into the rotary movement of a wheel, so that the steam engine could be made to power a variety of activities and machines.
The now-versatile steam engine was the first of the modern prime movers, the first modern device, that is, that could take energy as it occurred in nature and apply it to the driving of machinery.
To be sure, wind and running water were the prime movers of ancient times, but wind is erratic, and running water only exists in certain places. The use of fuel is certain; it always contains energy. What's more, it can be used anywhere and in any quantity within reason.
The steam engine, bringing the use of energy to all mechanical devices in far greater quantity than anything else had offered in the past was the key to all that followed rapidly under the name of the Industrial Revolution, when the face of the world was changed as drastically (and far more rapidly) than at any time since the invention of agriculture, nearly 10,000 years before.
╝The Stock Ticker
1869 A.D.
NEW YORK, NEW YORK
In 1869 an American telegrapher, Thomas Alva Edison (1847-1931), came to New York seeking employment. While he was in a broker's office waiting to be interviewed, a telegraph machine transmitting gold prices broke down. Edison was the only one present who saw how to fix it.
He went on to devise something better, and invented a stock ticker of a type that was used for many decades. This he proceeded to sell to a large Wall Street firm. He wanted to ask five thousand dollars but lost his courage and asked the president to make him an offer. The president offered 40 thousand.
That launched Edison on his career as probably the greatest inventor the world has ever seen.
]
Early Calendars
2800 B.C.
EGYPT
Use of the day (or the alternation of day and night) and parts of the day as determined by a sundial is insufficient as a means for keeping track of time. Certain phenomena, such as the changing of the seasons, have periods that are several hundred days long. It is tedious to count those days, and the chances of mistakes are great.
There is a cycle of intermediate length, however, that of the phases of the Moon. It takes 29 or 30 days for the Moon to go through its cycle of phases, and it takes 12 or 13 of these cycles (months, from the word Moon) to make up the cycle of the seasons.
We don't know when people first began to attach importance to the months.
There are indications that even prehistoric people counted them, but it was the people of the Tigris-Euphrates region who first systematized the matter. They worked out a cycle of 19 years, in which certain years had 12 lunar months and others had 13 lunar months. Such a cycle kept the years even with the seasons.
This lunar calendar was adopted by the Greeks and the Jews and is still used as the Jewish liturgical calendar.
The Egyptians, however, did not make use of the Moon primarily. To them, the important feature of the year was the periodic flooding of the Nile. The priests in charge of irrigation carefully studied the height of the river from day to day and eventually discovered that, on the average, the flood came every 365 days. That was also the time it took the Sun to make an apparent circuit of the sky relative to the stars. (In modern times, we view this as the time it takes the Earth to go around the Sun.) This is the solar year, and a calendar based on it is a solar calendar.
The Egyptians were aware that there were 12 new Moons to the year, so they had 12 months, but they made each month 30 days long, paying no attention to the actual phase of the Moon. That made 360 days, to which they added 5 more days at the end.
This calendar was much simpler and handier than any other calendar invented in ancient times. Historians are uncertain of the date when it was first adopted, but priests may have been using it for their private computations (it obviously made them more powerful if they alone knew when the Nile would flood) as early as 2800 B.C.
Nothing better than the Egyptian calendar was devised for nearly 3,000 years, and even then what was produced was a mere modification of it -- and not all the changes were for the better. Our present calendar is still based on the Egyptian calendar, with changes that are, in some cases, also not for the better. This makes our calendar, in essence, nearly five thousand years old.
ûStone Tools
2,000,000 B.C.
EAST AFRICA
Sometimes, we think of the human being as a tool-using animal. Tool-using is not really unique to human beings, however. For example, sea otters routinely smash shellfish against a rock they carry for the purpose on their abdomens as they float belly-up. A long litany of other examples could also be given. If we change that to tool-making animal, we are somewhat better off, but not entirely. Chimpanzees have been seen to strip leaves from twigs and then use the bare twigs as devices for capturing termites, which to them are tasty snacks.
Undoubtedly, australopithecines could do anything that chimpanzees could do. We have no evidence, but we can be fairly certain that they used tree branches and long bones as clubs. They could surely throw rocks or use them as sea otters do.
The australopithecines may have existed on Earth for three million years, not becoming finally extinct till as late as 1,000,000 B.C. For the final third of their existence, though, they were no longer the only hominids.
About two million years ago genus Homo came into existence. For a time, it coexisted with the australopithecines, but there was bound to be conflict between them, and in this, the larger and brainier hominids won out, contributing (very largely, perhaps) to the extinction of the australopithecines.
In the 1960s, the English anthropologist Louis Seymour Bazett Leakey (1903-1972), his wife, Mary, and their son, Jonathan, located remains of the oldest of the genus Homo in the Olduvai Gorge, in what is now Tanzania. The hominids thus uncovered were named Homo habilis (Latin for "able man," because with them were discovered objects that seemed to indicate that they made simple stone tools).
Homo habilis was smaller than some of the larger species of australopithecines. When, in the summer of 1986, fossil remains of Homo habilis were discovered that were some 1.8 million years old (the first time that both skull fragments and limb bones of the same individual of that species had been located), they seemed to represent a small, light adult about 3-1/2 feet tall and with arms that were surprisingly long.
Though members of Homo habilis may have been small, they had more rounded heads than any of the australopithecines and larger brains, nearly half as large as those of modern human beings. They had thinner skull bones, and based on the brain configuration, if they could not talk, they could at least make a greater variety of sounds. Their hands were more like our modern hands, and their feet were completely modern. Their jaws were less massive, so that their faces looked less apelike.
These creatures apparently used stone tools to chip pieces of flint and so create a sharp edge. This meant that for the first time, hominids had sharp edges in quantity and did not have to depend on the chance finding of one. Moreover the edges could be made truly sharp, and the sharpness could be renewed when the rock was blunted.
These stone knives increased the food supply. Homo habilis could not tear away at the tough hides of animals, as fanged predators such as the various cats, dogs, and bears could. Without knives, hominids had to make do with carcasses that had already been mangled by other predators and to make off with what they could scavenge.
With knives, however, Homo habilis had artificial fangs that could slit hides and scrape the meat off hides and bones. What's more, Homo habilis no longer had to scavenge. Hominids could now kill animals on their own, even fairly large animals. And once they caught on to the trick of tying stone axes to wooden branches and creating the first crude spears, they could stab animals at a distance. If the spears were thrown, the distance could be made long enough to obviate immediate retaliation.
Hominids became hunters and killed off the competing australopithecines, no doubt, so that for the last million years, all hominids, without exception, have been part of genus Homo.
φThe Earth as a Clock
1799 A.D.
ENGLAND
Many observers had noted that rocks existed in layers, or strata (the Latin word for "layers"). An English geologist, William Smith (1769-1839), who was engaged in working on canals, had frequent opportunities to see the strata at excavation sites.
He became interested in strata to the exclusion of all else and, in 1799, began writing on the subject. Smith made a new point. Each stratum had its own characteristic forms of fossils, not found in other strata. No matter how the strata were bent and crumpled -- even when one sank out of view and cropped up again miles away -- its fossils went with it. In fact, it seemed to Smith, one could identify a stratum from its fossil content.
Since it could be reasonably supposed that a stratum nearer the surface was younger than one deeper down, the strata offered a method for working out an orderly history of life from the fossils and even coming to some rough conclusions as to how long ago different fossils had existed as living forms.
æOther Antibiotics
1940 A.D.
WOODS HOLE, MASSACHUSETTS
American microbiologist Rene Jules Dubos's (1901-1982) discovery of tyrothricin had galvanized one of his past teachers, the Russian-born American microbiologist Selman Abraham Waksman (1888-1973).
Using Dubos's methods, Waksman began to search for bacteriocidal compounds in microscopic fungi. In 1940 he located one he called actinomycin because it was found in fungi of the Actinomycetes family. Not long after, he found one in fungi of the Streptomycetes family and called it streptomycin.
Streptomycin was quite effective against bacteria that were not affected by penicillin but was considerably more toxic to human beings than penicillin and had to be used very cautiously.
It was Waksman who coined the term antibiotic (from Greek words meaning "against [microscopic] life"), and for his work on them, he was awarded the Nobel Prize for medicine and physiology in 1952.
UStrong Interaction
1935 A.D.
JAPAN
Heisenberg had tried to explain why the nucleus remained intact despite the repulsion between protons by supposing the existence of exchange forces, Proton-Neutron Nucleus). Fermi had made use of that concept in working out his theory of the weak interaction.
The Japanese physicist Hideki Yukawa (1907-1981) used the ideas of Heisenberg and Fermi to build up a theory that would explain the nucleus. There had to be a short-range force like that of the weak interaction, one that could be felt only within the nucleus. This short-range force would have to be much stronger than the weak interaction and indeed much stronger than the electromagnetic interaction in order to overcome proton repulsion. For that reason, it came to be called the strong interaction.
Yukawa worked out his mathematical treatment in 1935. He showed that in order for the nucleus to exist, protons and neutrons had to exchange a particle possessing mass. The shorter the range of the force, the more massive the particle. He calculated that the particle exchanged ought to be about two hundred times as massive as an electron, or one-ninth as massive as a proton.
Such intermediate-sized particles were unknown at the time, but eventually they were discovered. Yukawa was then awarded the Nobel Prize for physics, in 1949.
He was the first Japanese to win a Nobel Prize.
╛The Stratosphere
1902 A.D.
FRANCE
Ever since balloons had been invented, scientists had used them to explore heights that they could otherwise reach only by climbing the highest mountains. However, by the time a balloon was six miles in the air, the cold and lack of oxygen could be fatal.
The French meteorologist Léon-Philippe Teisserenc de Bort (1855-1913) therefore took to sending up balloons bearing only instruments that could be read when the balloon returned to Earth.
He found in this way that the temperature of the atmosphere dropped steadily up to a height of about seven miles. At higher altitudes, the temperature remained constant as high as he could reach.
In 1902 Teisserenc de Bort suggested that the atmosphere be divided into two parts. The lower part, below the seven-mile mark, had temperature variations and therefore produced winds, clouds, and in short, the weather changes so familiar to us. This would be called the troposphere (from Greek words meaning "sphere of change"). Above it would be the constant-temperature stratosphere ("sphere of layers," because Teisserenc de Bort felt that constant temperature meant the gases would lie in undisturbed layers). The names have remained with us ever since.
πSubmarines
1898 A.D.
THE NETHERLANDS
Ships made to go under the water have been a human fancy for centuries, but the first to attempt to build one was a Dutch inventor, Cornelis Jacobszoon Drebbel (1572-1633), who piloted one in the Thames River between 1620 and 1624. An American inventor, David Bushnell (1742-1824), devised simple submarines that were used unsuccessfully against British ships in harbor during the Revolutionary War and the War of 1812.
It was not till 1898, however, that an American mechanical engineer, Simon Lake (1866-1945), succeeded in devising a submarine that could actually go out to sea. In that year, his submarine Argonaut I sailed from Norfolk, Virginia, to New York. This marked the true beginning of modern submarines.
)The Structure of Sugar
1884 A.D.
GERMANY
Though sugars had been studied throughout the 19th century, and though their atomic content was more or less known, the actual three-dimensional arrangement of the atoms was not known. The work of van't Hoff, 10 years before, had shown the importance of the three-dimensional arrangement of atoms in a molecule and the way this could be responsible for optical activity.
In a long series of experiments beginning in 1884, the German chemist Emil Hermann Fischer (1852-1919) isolated pure sugars and studied their structures. He showed that the best-known sugars contained six carbon atoms and could exist in 16 varieties, depending on how the carbon bonds were arranged. Each different arrangement was reflected in the way the plane of light polarization was twisted.
Fischer showed that there were two series of sugars, mirror images of each other, which he called the D-series and the L-series. He had to pick which mirror image belonged to which method of writing the formula, and he did so arbitarily. He had a 50-50 chance of guessing correctly, and (unlike Franklin on the electric charge), he guessed right. The natural sugars all happen to belong to the D-series.
While engaged in this work, Fischer also studied a group of substances called purines, with molecules that consisted of a double ring of atoms made up of five carbons and four nitrogens. They were eventually found to make up an important part of certain key biochemical substances.
For his work on sugar structure and on purines, Fischer received the Nobel Prize for chemistry in 1902.
0The Motion of the Sun
1783 A.D.
BATH, ENGLAND
To the ancients, the Earth was the motionless center of the Universe. To the early moderns, the Sun was.
In 1783, however, British astronomer William Herschel (1738-1822) began a systematic measurement of the proper motion of a great many stars. Very dim and very distant stars moved so slightly they could be considered motionless and were references against which the perceptible motions of the nearer stars could be measured.
As the years passed, Herschel found that in one direction in the sky, the stars were generally moving away from each other, while in the opposite direction they were very slowly closing in toward each other. In 1805 he came to the conclusion that this could best be explained by supposing that the Sun itself was moving toward that point from which stars seemed to be separating and was moving away from the point toward which other stars seemed to be converging. Just as Polish astronomer Nicolaus Copernicus (1473-1543) had maintained that the Earth was a planet like other planets, moving as they did, so Hers
