One of the most amazing things about Astronomy is the sheer size of everything involved. To grasp this we can first consider earthly dimensions. To measure around the home you would use a tape measure graduated in centimetres of which there are 100 to every metre. To measure distances between places you use kilometres. There are a 1,000 metres to each kilometre.
To compare this with space have a look at the next book called Astronomical Scales of Measurement.
$A2 Astronomical Scales of Measurement
The distances to the stars are measured in light years which is the distance light travels in one year. Since light travels at around 300,000 km per second this is a huge distance.
The distance between galaxies (which are very large groups of stars) is measured in millions of light years.
The distance in our own backyard, the Solar System, is measured in millions of kilometres.
Just to make things worse it is commonly believed by astronomers that the Universe is getting bigger as the galaxies are moving further apart. This is because of the theory that the Universe was started by an enormous explosion called The Big Bang.
$A3 Distances in the Solar System
The distance of the Moon from the Earth is 384,000 kilometres, hardly any distance at all in terms of the galaxy, but it still took the Apollo space missions 4 days to get there. Light travels from the Moon to the Earth in about 1 second.
In comparison it takes light over 8 minutes (more than 500 seconds) to get from the Sun to the Earth. This is considered one astronomical unit (AU). This distance, of about 150 million kilometres, would take an Apollo mission rocket around 4 years to complete.
The furthest known planet from the Sun is Pluto. This is about 40 times further away from the Sun than is the Earth. Therefore it would take over 150 years for a rocket on an Apollo mission to reach Pluto.
$A4 Distance to the Stars
Parsecs
3.26 light years (or 206 000 AU) make up a parsec. This is an abbreviation for parallax second. It is the distance at which the mean radius of the Earth's orbit subtends an angle of one arc second.
Nearest Star
The nearest star to the Sun is Proxima Centauri. It was discovered in 1915 and is 4.24 light years away. It slightly closer than the better known Alpha Centauri.
The Sun as a Star
The nearest star to the Earth is the Sun. The Sun is a star which just happens to be relatively close to the Earth.
$A5 Distances to the Galaxies
The most distant object that we can see from Earth with the naked eye is the Andromeda galaxy. It consists of 200 billion suns and is 2.3 million light years away. It is spiral in shape and is the nearest great spiral galaxy.
Some galaxies in order of their distance from Earth (shown in millions of light years)are:
Large Magellanic Cloud - 0.17
Small Magellanic Cloud - 0.20
Andromeda (M31) - 2.3
M33 - 2.3
M81 - 7
NGC 253 - 10
NGC 5128 - 13
M87 - 40
M104 - 40
Quasars are the very bright core of an active galaxy and are thousands of times brighter than ordinary galaxies. They are the most distant objects known being some 2,000 million light years and more away from us.
$A6 Other Distances
The apparent size of an object in the night sky is measured in degrees. As an example the full Moon measures about half a degree.
The distance from the Earth to the Sun is about 150 million kilometres or one Astronomical Unit (AU). On this scale of measurement Pluto averages about 40 AUs from the Sun.
$A7 Planetary Sizes
The sizes of the planets varies enormously. Here are some useful approximations of relative planetary sizes:
Mercury: pinhead
Jupiter: golfball
Saturn: table tennis ball
Neptune: marble
Pluto: pinhead
$A8 Solar Sizes
The Sun is huge in relation to the Earth. It would take 330,000 Earths to fill the same volume. The Sun has a diameter of 1,392 thousand kilometres.
Sunspots are highly magnetised dark spots on the surface of the Sun. They often come in groups and can be much larger than the Earth. They take about 10 days to cross the Sun. They have a cycle of approximately 11 years.
$A9 Masses
Jupiter is the heaviest planet while Mercury is the lightest in the Solar System.
The Sun loses approximately 4 million tonnes of mass every second. The mass is converted into energy.
$A10 How to Measure Distances
As the Earth orbits the Sun from one side to the other, nearby stars appear to move against the background of more distant stars. This is called parallax. By measuring this movement the distance to the star can be worked out.
Galaxies, which are much further away, are moving away from us and this causes the light from them to shift towards the red end of the spectrum. Measure this shift and you can calculate the distance.
$B1 Simple Sun Observations
The Sun rises in the East and sets in the West due to the rotation of the Earth about its axis.
Sunspots are cooler patches on the surface of the Sun and are also regions of intense magnetic fields.
An eclipse of the Sun is caused when the Moon is exactly between the Earth and the Sun, so casting a shadow on the Earth.
$B2 Simple Earth Observations
The Earth is constantly spinning and moving. It takes one year to orbit the Sun and 1 day to complete a rotation on its axis. When you are on the side of the Earth facing the Sun it is day. Night occurs when your side of the Earth has spun away from facing the Sun.
On a clear night with good eyesight you can see about 5,000 individual stars. You can actually see billions more but these appear as a haze as they are so far away.
Some planets (the word means wandering star) can be seen at night. The brightest of these is Venus when viewed from the Earth. Dawn and dusk are good times to watch for planets.
If you were on another planet you would be very likely to be able to see the Earth. It is brighter than the other planets because of the atmosphere. The Earth viewed from space has a blue colour due to the oceans.
$B3 Simple Moon Observations
The Moon orbits the Earth approximately every 28 days (a lunar month). You can see the Moon because it reflects light from the Sun. It seems to change shape but this is simply due to the position of the Earth and the Sun.
Sometimes you barely see the Moon at all because it is between the Earth and the Sun and the light is shining on the side you cannot see. If it gets directly in the way then there is a solar eclipse and a part of the Earth will be dark for a short period.
A few facts:
There is no atmosphere on the Moon so there can be no wind as we know it.
The surface of the Moon is covered by "seas" (maria) and many craters.
$B4 Solar Eclipses
A solar eclipse is caused by the Moon coming exactly between the Sun and the Earth. This casts a shadow on the Earth about 300 km wide and many thousands of kilometres long.
Eclipses due to the rotation of the Earth and the movement of the Moon in its orbit can last a maximum, at any one point on the Earth's surface, of about 8 minutes.
$B5 Lunar Eclipses
A lunar eclipse is caused when the Moon passes into the shadow of the Earth. Therefore to see a lunar eclipse you must be on the dark side of the Earth ie nighttime. A partial lunar eclipse is when only part of the Moon passes into the shadow of the Earth.
$B6 Comets
A comet is a small body composed of ice and dust which orbits the sun on an elongated path.
Edmund Halley discovered Halley's comet. This comet was first recorded in 240 B.C. and returns to the Solar System every 76 years.
The comet Shoemaker-Levy 9 crashed into Jupiter in 1992 after first passing the planet and being broken up into several pieces by gravity.
$B7 Meteors
A meteorite is a lump of rock or metal which lands on the Earth from space, having survived the entry into the atmosphere.
Some meteors or "shooting stars" do not survive the entry into the atmosphere and burn up.
The large crater in Arizona was formed by a meteorite some 50,000 years ago.
$B8 Radio Telescopes
Grote Reber started off the science of radio astronomy in his backyard using parabolic reflectors in 1940.
Jodrell Bank is the site of the most famous radio telescope in the U.K. and is an example of a single array.
The VLA or very large array in Mexico uses many radio telescopes to mimic a radio telescope some 42 km across.
$B9 Ancient Astronomical Instruments
The first refracting telescope was invented by Lippershey in 1608. This used lenses to gather and focus light.
The first reflecting telescope was invented by Isaac Newton in 1671. This used mirrors to gather the light.
Stonehenge is generally thought to have been used as an observatory and a calculator for the prediction of equinoxes and eclipses.
$B10 Modern Astronomical Instruments
A CCD is a charge-coupled device which is an electronic detector that can record an image.
COBE (NASA's COsmic Background Explorer satellite telescope) used CCDs to measure the microwave background radiation left over from the Big Bang.
The HST is the Hubble Space Telescope placed into Earth orbit in 1990. It has had a chequered history but is now finally working correctly.
$C1Commonly Known Northern Constellations
The Great Bear, Big Dipper and Plough are all names for Ursa Major, a constellation in the Northern hemisphere.
The second most common constellation is Orion the Hunter with its three belt stars making it most distinctive. Orion was very important to the ancient Egyptians.
The Little Bear and Little Dipper are both names for Ursa Minor which has Polaris the pole star at the end of its handle.
$C2 Commonly Known Southern Constellations
The Southern Cross or Crux has helped to guide sailors in the Southern hemisphere for centuries. Because it lies so far south it was not mapped until 1592.
The Octant was invented by John Hadley in 1730 and the Southern constellation was named after it in honour.
The Water Snake or Hydras was created in 1603 by Johann Baker and is easily confused with Hydra the Sea Serpent.
$C3 Signs of the Zodiac
The Zodiac is a belt of 12 constellations that straddle the sky. The Signs of the Zodiac were established before Astronomy existed. It is commonly believed that they influence the lives of humans although there is no clear proof of this.
Scorpio is the sign of the scorpion.
Libra is the sign of the scales.
Aries is the sign of the ram.
$C4 Animal Constellations
Constellations represent many things. There are a number of animal constellations such as Leo the Lion, Aries the Ram and Delphinus the Dolphin.
$C5 Mythical Animal Constellations
Mythical creatures feature as constellations among which are:
Centaurs the Centaur , half man - half horse
Monoceras the Unicorn
Phoenix the Phoenix
$C6 Mythical People Constellations
People from mythology feature as constellations such as:
Andromeda the Chained Princess
Aquarius the Water Bearer
Ophiuchus the Serpent Bearer.
$C7 Constellations Representing Objects
The constellation of Aga the Altar represents the altar of the centaur Chiron.
Victor represents the Painter's Easel.
Triangulum the Triangle has a distinctive triangle shape.
$C8 Difficult Northern Constellations
The constellation of Cassiopeia has a distinctive "W" shape to it.
Recticulum is a quadrilateral shaped constellation.
Bootes was a herdsman the son of Demeter.
$C9 Difficult Southern Constellations
The Southern Constellations have among their members:
Indus the Indian
Volans the Flying Fish
Crux the Southern Cross.
$C10 Navigation
Sextants are used by sailors to measure the latitude of their position using the Sun. At night if they had no compass then they could look for Polaris the pole star which is at the celestial north.
$D1 Sun Facts
Like all stars, the Sun is a ball of hot, glowing gas. The centre is hottest and the surface is called the photosphere. You should never directly look at the Sun as it will damage your eyes.
Around the Sun is a cloud of gases. This is called the Corona.
The Earth orbits the Sun - this is known as the heliocentric view of the Solar System.
Due to the atmosphere many effects can be seen from the surface such as "white rainbows". These are luminous rings seen around the Sun in misty alpine regions.
Baily's beads is the light seen around the Sun during a total eclipse. They are caused by the irregular surface of the Moon affecting the light.
$D2 Moon Facts
The Moon orbits around the Earth completing one orbit approximately once a month ("moonth" is the origin of the word month). It is thought to be about 4.5 billion years old being created by a large object smashing off part of the Earth.
It is 384,000 km from the Earth and has an enormous effect in terms of the ocean tides. These are caused by the gravity of the Moon.
When the Moon was visited by the Apollo missions they left seismic detectors behind. These register around 3,000 Moon quakes every year.
The surface of the Moon features high mountains and vast plains of lava which when seen with the naked eye look like seas.
$D3 Mercury
Mercury is 0.39 AU from the Sun (58 million km) and is the nearest planet to it. From the Earth it looks white. It orbits the Sun every 88 days and rotates once every 59 days.
Mercury has no moons and because of its close proximity to the Sun it has no atmosphere.
The surface temperature is enough to melt lead. During the day it can get as hot as 400 degrees Celsius cooling to -200 degrees Celsius at night.
It is quite easy to see if you know where to look. Look low in the West after the Sun has gone down or in the East around dawn.
$D4 Venus
Named after the Roman goddess of beauty and love. Venus is the second planet from the Sun and takes approximately 7 months to orbit it. It takes longer to rotate (243 days) than it does to orbit the Sun (225 days) giving less than 1 day per year in effect.
Its atmosphere consists mainly of carbon dioxide at 460 degrees Celsius. The pressure is 100 times that of Earth. Because of all the carbon dioxide the heat cannot escape and it hardy cools even at night.
From Earth it can usually be seen in the early morning or late evening and has the names "Morning Star" and "Evening Star".
It used to be considered a star and was previously called Hesperus and Phosphorus.
$D5 Earth
The Earth is the third planet from the Sun and is unique in many ways. Its surface is covered by 70% water, it has 21% oxygen in its atmosphere and it also has life. The core is extremely hot and occasionally the liquid core bursts through weaknesses in the surface in the form of volcanoes. The largest volcano on Earth is in Hawaii.
Earth is a distance of 1 AU from the Sun. It features electrical storms and water vapour (clouds) which obscure a lot of the surface.
The atmosphere allows heat both in and out which is why it is generally warmer in the day than it is at night.
The Earth has been mostly compared to Mars to which it is very similar in a number of respects.
$D6 Mars
Mars is named after the God of War and is also known as the Red Planet because of its colour as seen from Earth. The colour is due to the rocks which are full of rusted iron. Mars has two moons - Phobos and Deimos. These are quite small and irregular in shape.
Many people believed that there was life on Mars until quite recently. Not many people still believe this although recent controversial evidence suggests otherwise.
It is 1.52 AU from the Sun and has volcanoes although they are no longer active. The largest of the volcanoes is called Olympus Mons which is much larger than any volcano on Earth.
Mars is a cold place and has ice caps made of solid carbon dioxide. There is evidence of flowing water erosion but probes have failed to find any trace of where it is now.
$D7 Asteroids
An asteroids is a minor planet less than 1,000km in diameter that orbits the Sun. Mostly asteroids tend to be in the Asteroid Belt which lies between the orbits of Mars and Jupiter.
The Asteroid Belt consists of about 15,000 asteroids which constantly crash into each other making smaller asteroids. The biggest known asteroid is called Ceres.
About 200 asteroids pass the orbit of the Earth and it is possible that one day one of these will collide with the Earth. There are probably thousands more yet to be discovered.
$D8 Jupiter & Saturn
Jupiter is the largest planet in the Solar System and is 5.2 AU from the Sun. It takes 11.9 years to orbit the Sun. It is a huge ball of liquid and gas.
It has a striking feature of a giant swirling red spot in its atmosphere. This is 50,000km long and is therefore considerably larger than the Earth.
Jupiter has 16 moons in total which are fascinating to study in their own right. The largest is Ganymede which is also the largest in the Solar System.
Saturn is much further at 9.54 AU and takes 29.5 years to make an orbit. It is slightly smaller and its most striking feature is its system of rings which are composed of chunks of ice of different sizes.
Saturn has a total of 18 moons, more than any other planet in the Solar System. The largest is Titan which is the 2nd largest in the Solar System and even has an atmosphere.
$D9 Uranus and Neptune
Uranus was discovered by William Herschell on the 13th March 1781. It is 19.2 AU from the Sun and takes 84 years to complete an orbit. It has 15 moons and rotates on its side. There are 11 narrow rings but these are much less visible than those around Saturn.
Neptune is an enormous ball of liquid and gas and takes 165 years to orbit the Sun. It has an atmosphere consisting of hydrogen and helium. It is the second furthest planet from the Sun at 30.0 AU. It is larger than the Earth but much smaller than its neighbour Uranus.
A fascinating feature of Neptune is that one of its 8 moons, Triton, has a retrograde orbit. This means it goes round the opposite way to the rotation of the planet.
Neither of these planets is visible with the naked eye.
$D10 Pluto
Pluto, the outermost planet, was discovered in 1930 by Clyde Tombaugh. It has one moon and its atmosphere consists of methane.
Pluto takes 249 years to orbit the Sun. It is much smaller than the Earth and is not visible with the naked eye.
$E1Common Galaxies and Star Clusters
Galaxies to the naked eye look like small fuzzy patches of light. When viewed through a telescope they can be seen in all their glory. The galaxy which can be seen best with the naked eye is the Andromeda galaxy in the constellation of Andromeda.
Star clusters are close groupings of stars usually all the same age. The best known is the Pleiades or Seven Sisters which contains about 500 stars and is about 410 light years away.
$E2 Galaxy Shape
Galaxy shapes or types of galaxies are as follows:
Spiral : have great spiral arms and look like whirlpools
Barred spirals : a spiral with a distinct bar running across the galaxy
Elliptical : vary in size from dwarfs to giants
Irregular : faint, amorphous groupings which can be quite small
Peculiar : a galaxy that seems to have suffered some form of disturbance
Seyfert : named after Carl Seyfert which are great energetic spiral systems
$E3 Types of Galaxy
Galaxy shape or types of galaxies are as follows:
Spiral : have great spiral arms and look like whirlpools
Barred spirals : a spiral with a distinct bar running across the galaxy
Elliptical : vary in size from dwarfs to giants
Irregular : faint, amorphous groupings which can be quite small
Peculiar : a galaxy that seems to have suffered some form of disturbance
Seyfert : named after Carl Seyfert which are great energetic spiral systems
$E4 Quasars and Seyferts
Quasars or quasi-stellar objects are believed to be the cores of highly energetic galaxies many millions of light years away. The great distance involved makes study of these objects difficult.
Seyferts, discovered by Carl Seyfert in 1942, are highly energetic galaxies with violent core activity. The most famous is M77 in Cetus.
$E5 Temperatures
The temperatures found in stars are the hottest in the Universe ranging from a few thousand degrees at the surface to many millions at the core.
The Sun is a fairly average star with a surface temperature of 6,000 degrees Centigrade and is known as a main sequence star.
The sequence of stars runs as follows:
Main Sequence
Most stars fall into this category.
Red Dwarfs
Cool, faint and smaller than the Sun.
White Dwarfs
Stars nearing the end of their life, very dense and small.
Red Giants
Very large cool stars, usually about the same mass as the Sun but very much larger.
Supergiants
Large fast burning stars such as Rigel in Orion. They are the hottest.
$E6 Red Giants and Dwarfs
A well known red giant star is Betelgeuse in Orion which is some 1,000 million km across. Red Giants are very large stars which radiate most of their energy at the red end of the visible spectrum.
Red dwarfs are cool, faint stars which use their nuclear fuel sparingly and so glow red. There are many red dwarfs, but we can only observe the closer ones.
$E7 White Dwarfs
White dwarfs are smaller than red dwarfs and are very dense. They typically have the mass of the Sun squeezed into the size of the Earth. The nuclear fire of these stars has gone out because all the available fuel has been used up. One day the Sun will end up as a white dwarf.
$E8 Gas Clouds
Gas clouds are interstellar clouds of gas and dust which can be many light years across. Stars are formed in gas clouds usually many at a time.
$E9 Nebulas
Nebulas are clouds of gas and dust usually left over from stars which have exploded. They are some of the most beautiful objects to be seen with a wide range of colours and shapes.
$E10 Super Novae
Super novae are stars which explode throwing off a shell of hot gas exposing the inner regions. These regions are very bright which makes the super nova very distinctive. The most famous remains of a super nova is the crab nebula. Super nova are becoming more common the further we can see with our instruments. Astronomers can on average expect to see a good super nova about once a year.
$F1Rockets
The Chinese invented the first rockets (and fireworks) around 1100 A.D. and they were propelled by gunpowder. They were used on festive events and were just really a novelty. It took the Europeans to put gunpowder to more practical use in weapons during the Middle Ages. Rockets themselves were put to use as artillery but it took the Second World War before rockets came into their own as proper weapons.
$F2 U.S.A. Rockets
The main propellants used for rockets are liquid oxygen and liquid hydrogen. These propelled the giant Saturn V rocket in the American Apollo program. These two fuels are combined in a more controlled way in a fuel cell to generate electricity aboard a spacecraft. A useful by-product is water for the crew to use.
$F3 U.S.S.R. Rockets
The U.S.S.R. spacecraft known as Soyuz is propelled by a mixture of liquid oxygen and kerosene (also known as paraffin). These crafts have been the mainstay of the Soviet space program being involved in the Soyuz 19-Apollo link up of 1975. Unlike the Apollo missions the Soyuz capsules always landed on dry land, a cushion of retro-rockets firing just before landing.
$F4 Launch Pads
The main launch pad for the U.S.A. is Cape Canaveral which used to be known as Cape Kennedy. The one for the Soviets is at Baikonur in Kazakstan. The E.S.A. uses a launch pad in French Guyana to launch its satellites.
$F5 Moon Shots
The Apollo program was the first and only Moon program by the Americans. After several test flights including Apollo 8 which circled the Moon for the first time, the first manned landing was by Apollo 11 in July 1969.
To get from the Earth to the Moon a manoeuvre called Trans-Lunar Injection is performed.
$F6 Space Stations
The first (and only) American space station was Skylab launched in 1973. The first Soviet space station was called Salyut which was the predecessor of the current station Mir (which means peace).
$F7 U.S.A. Astronauts
Alan Shepard was the first American to enter space on a 15 minute sub-orbital flight. He was followed sometime later by John Glenn who did the first proper orbit for an American. Neil Armstrong was the first man to set foot on the Moon followed by "Buzz" Aldrin. Michael Collins remained orbiting the Moon in the command module.
$F8 U.S.S.R. Astronauts
The first man in space was the Russian Yuri Gagarin on the 12th April 1961. Tragically Gagarin was killed in an air crash in 1968. The Russians scored an impressive series of firsts in the early sixties. These included the first female in space Valentina Tereshkova and the first man to space walk Alexei Leonov.
$F9 Disasters
The space travel business has not been without its disasters. The worst was the explosion aboard the space shuttle Challenger in 1986 killing all seven astronauts. A training accident during the Apollo I mission killed three astronauts in 1967. The tragedy was caused by an electrical fault which started a fire. The astronauts died from toxic gas inhalation.
$F10 Space Shuttle
The space shuttle is the current workhorse of the American space program. It weighs almost 2 million kg when launched and is protected by 34,000 ceramic tiles on re-entry to the atmosphere.
$G1 First Beginnings
The first credited flight by a liquid fuelled rocket was by Robert H. Goddard in March 1926. It was much derided at the time by the press. A rocket pioneer called Wernher von Braun took Goddard's results on board and went on to develop the V-2 rocket for Nazi Germany. This rocket was first used in action in 1944. At the end of the war operation paperclip made sure that he and his scientists went to work for America in the space program.
$G2 Early Experiments
Wernher von Braun went to work for the Americans after WW II using the captured V-2 rockets for high altitude research. The Americans had the lead by capturing most of the rocket scientists. However, this advantage was squandered as Soviet Russia won an impressive series of firsts with Sputnik I and then in 1957 the first animal in space: a dog.
$G3 Satellites
Sputnik I was the first successful satellite to orbit the Earth in 1957. This was closely followed by Explorer I, the first successful American satellite, launched in 1958. These achievements were ultimately down to Arthur C. Clarke who first proposed the idea of an artificial satellite in 1945.
$G4 Probes
There have been many probes and landers since the first satellites. Here are a few families:
Name: Galileo
Mission: Halley's Comet
Power source: Nuclear Reactor
Name: Mariner
Mission: Map Mars
Power Source: Solar Cells
Name: Surveyor
Mission: Soft landing on the Moon
Power Source: Solar Cells
Name: Voyager
Mission: Fly by the outer planets
Power Source: Nuclear Reactor
Name: Venera
Mission: Map and land on Venus
Name: Viking
Mission: Map and land on Mars
Power Source: Nuclear Reactor
$G5 Landers
There have been many probes and landers since the first satellites. Here are a few families:
Name: Galileo
Mission: Halley's Comet
Power source: Nuclear Reactor
Name: Mariner
Mission: Map Mars
Power Source: Solar Cells
Name: Surveyor
Mission: Soft landing on the Moon
Power Source: Solar Cells
Name: Voyager
Mission: Fly by the outer planets
Power Source: Nuclear Reactor
Name: Venera
Mission: Map and land on Venus
Name: Viking
Mission: Map and land on Mars
Power Source: Nuclear Reactor
$G6 Solid rocket fuels
Early rockets used gunpowder for propellant. They are an example of a solid fuelled rocket. They get the oxygen required for the reaction from the chemical makeup of the propellant. Modern solid fuel propellants, as used on the space shuttle boosters, are made from a putty like material moulded into shape in sections.
$G7 Liquid Rocket Fuels
Liquid propellants are the other main fuels, typically LH, liquid hydrogen, and LOX, liquid oxygen, are combined in a combustion chamber to produce thrust. The Russian space program uses liquid oxygen and kerosene (paraffin) as propellants. Kerosene is obtained from crude oil.
$G8 Communication Satellites
The first successful communication satellite was Echo I, a passive satellite made of plastic and aluminum. This bounced radio signals off its surface. The first satellite to relay television pictures across the Atlantic ocean was Telstar I. The majority of satellites in orbit today are for communication - relaying television, radio, telephone and computer messages around the globe.
$G9 Cost
The price of the space programs has been estimated. Firstly the cost of the rocket program in Nazi Germany has been estimated at about 2,000 million US dollars - almost as much as the Manhatten project which gave America the atomic bomb.
The Apollo program to put a man on the Moon cost approximately 25,000 million US dollars. Today's costs are more modest as the space race is no longer on.
The proposed Mars Global Surveyor by will cost about 154 million dollars.
$G10 Theory
Orbital velocity for an object varies with altitude. In general the higher the altitude the lower the orbital velocity required. Inertia is a property of mass and is a measure of a bodies resistance to motion. No orbits are truly circular although they look it. They are in fact elliptical in shape.
$H1First Rockets
The first rockets used gunpowder as a propellant. Gunpowder is known as a low explosive because it burns, unlike high explosives which detonate by a supersonic shockwave.
The first rocket to use liquid fuel was flown by Robert H. Goddard in 1926. Indirectly this led to the V-2 missile which used alcohol and liquid oxygen as the propellants.
$H2 Calendars
The Chinese made the earliest known calendars in 1300 B.C. although the Babylonians and ancient Egyptians also developed accurate calendars. The Egyptians used their calendar to regulate their economy, and help predict when the Nile's annual flood would take place and so irrigate their fields.
Stonehenge, built around 1800 B.C., was designed to predict the motions of the Moon and Sun and was therefore used as a calendar.
$H3Measuring Time
The easiest way to measure time is by passage of day and night. Man has sought better and better ways to measure time.
One of the most accurate is to use a mechanism regulated by the swing of a pendulum.
The most accurate way to measure time today is to use an atomic clock which uses the oscillation of atoms as a clock.
$H4Arthur C. Clarke
Arthur C. Clarke first proposed the idea of an artificial satellite in 1945. He was written many books in the field of science fiction and currently resides in Sri Lanka.
$H5Astronauts
The first American to walk in space was Ed White, who was tragically killed in a training accident aboard Apollo I in 1967.
The last American to walk on the Moon was Eugene Cernan on the Apollo 17 mission in 1972.
The average age of all the astronauts who walked on the Moon is 39 years.
$H6Missiles
The V-2 was the precursor to the modern ICBM, InterContinental Ballistic Missile. This missile carried a one tonne warhead and was powered by a mixture of alcohol and liquid oxygen. The alcohol came from the distillation of fermented potatoes.
After the war the Americans tested captured V-2s at White Sands, New Mexico.
$H7Kepler
Johannes Kepler (1571-1630) joined Tycho Brahe in Prague and succeeded him as Imperial Mathematician when he died. He used Tycho's records, which documented observations of the motions of the planets for over thirty years, to formulate his three laws of planetary motion.
1. The orbit of a planet is an ellipse.
2. A planet sweeps out equal areas of an orbit in equal time.
3. The period of an orbit squared is proportional to the distance from the Sun of the planet squared.
$H8Galileo
Galileo Galilei observed four moons of Jupiter in 1609 using a small refracting telescope he made himself. He published his discoveries only to have the Church warn him to change his views since they contradicted accepted dogma.
He was tried by the Inquisition for heresy, found guilty, and lived out his days under house arrest. He was finally absolved of his "crimes" in 1992.
$H9Newton
Isaac Newton invented the reflecting telescope in 1671 which used a curved mirror instead of a lens as the main light gatherer. He formulated his laws of motion in 1666 at the age of 24 but it was twenty years later before he refined and published his results.
He invented mathematical calculus to solve the problems of motion of the planets, showing that Kepler's laws were just a special case of his laws of motion.
The most famous law of motion is the third, which states that for every action there is an equal and opposite reaction.
$H10Einstein
Einstein's General Theory of Relativity, published in 1916, predicted an expanding Universe. A prediction which Einstein did not like, so he introduced a cosmological constant to give a steady state Universe neither expanding nor contracting. This, he acknowledged later, was a great mistake. Armed with his theory, he made many predictions: one of which was that as the velocity of a body increases its mass does as well.
$I1Simple Facts
Early man divided his time into three natural units: the day, the month (governed by the period of the Moon) and the year (governed by the seasons).
The laws of gravitation for the bodies of the Solar System were discovered by Isaac Newton.
The most common element in the Universe is hydrogen followed by helium.
$I2Definitions
A superior planet is one whose orbit is further away from the Sun than the Earth. While an inferior planet is one whose orbit is closer.
A planetoid is a minor planet or asteroid. These are small bodies which vary in size from the largest, Ceres, which has a diameter of 1003km, to objects with diameters of less than 1km. Most, like Ceres, orbit the Sun in a belt called the Asteroid Belt, which lies between the orbits of Mars and Jupiter, although a few, for example Chiron whose orbit lies almost entirely beyond that of Saturn, have very different orbits from those in the main belt.
$I3Spectrum
Light can be split up into its component colours using a prism. The prism refracts or "bends" the different colours which make up white light by different amounts so spreading them out.
Visible light is but one part of the electromagnetic spectrum stretching from radio waves up to gamma waves. As you proceed up the spectrum from red to blue the frequency of the waves increases and the wavelength decreases.
Sound is not part of the electromagnetic spectrum.
$I4Gravity
Gravity is a mutual attraction between two bodies. If a body is large enough then it can deflect the passage of light just like a lens. This gravitational lens enables us to see objects behind other large objects such as galaxies. The further you recede from a gravity source the more the force decreases.
$I5Radiation
The spectrum of electromagnetic radiation stretches from radio waves to gamma rays and beyond.
When a radioactive atom decays it can give off electrons otherwise known as beta particles. These electrons carry a negative electrical charge and produce electromagnetic radiation.
$I6Anti-Matter
Anti-matter was first proposed by Paul Dirac, an English theoretical physicist best known for his work on quantum mechanics and his theory of the spinning electron.
The first anti-particle, the positron, was found sometime later.
Anti-matter is composed of particles which are mirror images of the particles which constitute ordinary matter. Particles of anti-matter have the same mass as their corresponding normal matter particles but have opposite charge.
For example an electron carries a negative charge while its anti-matter equivalent, the positron, has a positive charge.
Anti-matter is destroyed when it comes into contact with normal matter, resulting in a great release of energy.
$I7Steady State
Fred Hoyle proposed the Steady State theory which holds that the Universe is infinite in size and that matter is slowly created as it expands. This was eventually displaced by the Big Bang theory of creation.
$I8The Big Bang
George Gamow first proposed the Big Bang theory in 1940 which said that the Universe expanded from an initial point of infinite density.
The best evidence we have supporting this theory is the background microwave radiation which has been described as the faint pale glow resulting from the Big Bang explosion thousands of millions of years ago.
$I9Speed of Light
Light is made up of particles called photons. The speed of light is an invariant which means that it is a quantity that does not alter. However you measure the speed of light it always gives the same value; the speed of light is independent of the velocity of the observer. This fixed speed means that there is an observation limit which is the greatest distance that light has travelled to reach the Earth.
$I10Black Holes
A black hole is a region where space-time is so warped that not even light can escape from it. It is a point of infinite density and is formed when a massive star collapses in on itself under gravity.
For a body of a given mass, once its radius decreases to a value known as the Schwarzchild radius, light is unable to escape form the bodies surface and so the body becomes a black hole.
Theory suggests that black holes may give rise to worm holes that link up to other black holes. These could be short cuts for spacecraft capable of withstanding the enormous crushing forces involved in passing through a black hole.
$J1Trivia
Moon's men are thieves and highwaymen of old who used to operate by the light of the Moon by which they could see to do their deeds.
The old English name for the Moon is Mona.
The Moon goes through several phases as it presents itself to the Sun.
Gibbous means that more than half of the Moon is visible.
$J2Little Green Men
Science fiction is a rich vein for speculating about the future. H.G. Wells wrote a book called The First Men in the Moon who used an anti-gravity substance called Cavorite in their spacecraft.
In his book War of the Worlds he had the Earth invaded by the inhabitants of the dying world of Mars.
Arthur C. Clarke set his book called The Sentinel, in 2001 which was made into a film by Stanley Kubrick.
$J3Television
Television has dealt with many astronomical facets and science fiction over the years amongst which was the television series U.F.O. which dealt with aliens visiting Earth for spare body parts. They used mankind as one giant organ bank for their use. The alien invaders in 'V' were lizards disguised as humans who had come to Earth to steal all the water.
The BBC have been running The Sky at Night presented by Patrick Moore for over 35 years.
$J4Unusual Facts
The Sun would burn for about 4,600 years if it were made of coal. This calculation means that ordinary burning does not power the Sun since it has been shining for many millions of years at the present rate.
On the Earth it is only possible to see a total solar eclipse every 360 years from the same position.
The Greek word "kosmos" means order and everything.
$J5Definitions
When an satellite is at the farthest distance from the object that it is orbiting, then it is at it's apogee. It is at its perigee when it is the shortest distance away. This is because orbits are not circles but ellipses.
The cosmological principle is that at the scale of the Universe everywhere looks pretty much the same where ever you look.
$J6Time
Einsteins theory of Relativity predicts that as an object approaches the speed of light, time measured by a motionless observer, appears to slow down. It can best be remembered by "moving clocks run slow". Using this property it is possible to time travel but only in one direction, the future.
Light pollution is the light from street lamps etc. reflecting around the atmosphere and so giving a glow to the night sky which makes astronomical observations difficult.
$J7Particles
Some particles of matter:
Electron a particle with a negative electrical charge found orbiting the nucleus of an atom
Proton a particle with a positive electrical charge found in the nucleus of an atom
Neutron a particle with neutral charge found in the nucleus of an atom
Quark a particle which,in different combinations, makes up those listed above
$J8Fuels
Hypergolic fuels are ones which need no spark to start combustion. They spontaneously ignite when mixed. An example of Hypergolic fuel is Hydrazine and Nitrogen Tetroxide as used aboard satellites.
The ISP value measures how efficient a fuel is as it burns. Values above 450 are rated as excellent.
$J9Space Flight
Konstatin Ziolkovsky wrote the first treatise on space travel many years before it actually happened.
A full size mock up of the space shuttle was carried on a Boeing 747 Jumbo Jet in order to test the design.
The Apollo 15 mission to the Moon had the first wheeled vehicle on the Moon. The Lunar Rover was made of aluminium to keep the weight down.
$J10Difficult Definitions
A geodesic is the shortest distance between two points. It is not always a straight line since any two points on the surface of the Earth are connected by a curve due to the shape of the Earth.
The isotropy of space means that all directions are the same, no matter where you go, space will always be the same. There are no preferred directions, an experiment performed pointing one way will give exactly the same results if pointing another way.
The homogeneity of time means that all time instants are the same. Time does not pass at different rates in different places.
Einstein showed these two assumptions to be false with his Theory of Relativity.
