Precipitation that results from the burning of fossil fuels by industries. The chemicals released into the atmosphere by the burning of fossil fuels cause sulfuric acid to form in the clouds; the sulfuric acid then mixes with the rainfall. Acid rain is a type of pollution that affects the forests Ec[000000]f[16]LFand wildlife of the northeastern United States and Canada.
Ec[000000]f[16]LBAlbert Einstein
BA famous scientist and physicist born in Germany in 1879. He is considered to be one of the most brilliant theoretical physicists of all time. His formula of E = mcS2S (energy equals units of mass times the speed of light squared) and his theory of relativity were the basis for the use of atomic energy. Einstein died in 1955.
Ec[000000]f[16]LBAndromeda Galaxy
BThe Andromeda Galaxy is the nearest galaxy to the Milky Way Galaxy. The Andromeda Galaxy is about 2.2 million light-years away but can be seen with a simple telescope on clear nights away from city lights. The Andromeda Galaxy contains at least 200 billion stars.
Ec[000000]f[16]LBAphrodite Terra
BThe smaller of the two major land masses on Venus, the planet named for the Roman goddess of beauty and love. Aphrodite was the Greek name for the goddess of beauty and love.
Ec[000000]f[16]LBasteroid belt
BA region located between the orbits of the planets Mars and Jupiter, where thousands of asteroids are found in orbit around the Sun. Most of the asteroids in our solar system are located within this asteroid belt.
Ec[000000]f[16]LBasteroids
B
Small, irregularly shaped, rocklike celestial bodies whose orbit around the Sun lies mainly between the planets Mars and Jupiter. Asteroids may range in size from 621 miles in diameter to less than one mile in diameter. There are thousands of asteroids in our solar system.B
B Ec[000000]f[16]LBastronaut
BA person trained for spaceflight.
Ec[000000]f[16]LBastronomer
BA scientist who studies and is expert in their knowledge of the universe. Astronomy involves the scientific study of the chemical and physical properties of celestial bodies such as stars and planets other than Earth. Astronomy is concerned with the study of the origin, evolution, Ec[000000]f[16]LFmotion, size, relative position and composition of the celestial bodies in our universe.
Ec[000000]f[16]LBastronomy
BThe science of the universe. Astronomy involves the scientific study of the chemical and physical properties of celestial bodies such as stars and planets other than Earth. Astronomy is concerned with the study of the origin, evolution, motion, size, relative position and Ec[000000]f[16]LFcomposition of the celestial bodies in our universe.
Ec[000000]f[16]LBAtlantis
BAtlantis often is called the lost continent. We don't know if it ever really existed, but some people believe that its land mass, once located in the Atlantic Ocean, supported an advanced society. Legend narrates that an earthquake caused the large island kingdom to sink to the bottom Ec[000000]f[16]LFof the ocean. People still search for Atlantis, but most scientists don't believe it ever existed.
Ec[000000]f[16]LBatmosphere
BThe gaseous mass that surrounds a star or planet. Earth's atmosphere, which consists of the air we breathe, includes the gaseous chemical elements oxygen and nitrogen. Earth's atmosphere extends to a height of approximately 621 miles.
Ec[000000]f[16]LBaurora australis
BThe southern lights; the aurora that occurs in the Southern Hemisphere around the south magnetic pole.
Ec[000000]f[16]LBaurora borealis
BThe northern lights; the aurora that occurs in the Northern Hemisphere around the north magnetic pole.
Ec[000000]f[16]LBaurora
BLuminous bands and streamers of light in the night sky, caused by charged particles in the solar wind that strike the outer part of Earth's atmosphere, usually in the northern and southern polar regions.
Ec[000000]f[16]LBaxis
BThe imaginary straight line on which a planet rotates. Earth's axis runs between the North Pole and the South Pole.
Ec[000000]f[16]LBbinary star
BA pair of stars that revolve around each other because they share a common center of gravity.
Ec[000000]f[16]LBCaloris
BA large crater on the surface of the planet Mercury. It is about 810 miles (1,300 kilometers) across. It is called Caloris, from the Latin word Icalor Imeaning "hot," because it is the hottest place on the planet Mercury.
Ec[000000]f[16]LBcanals
BArtificial waterways used for irrigation, flood control, shipping, and transport of drinking water. Some famous canals on Earth are the Panama Canal, the Suez Canal, and the Erie Canal.
Ec[000000]f[16]LBcarbon dioxide
BA compound that is made up of molecules containing one carbon atom and two oxygen atoms. Carbon dioxide is a colorless, odorless, and incombustible gas. Carbon dioxide, produced by respiration and combustion, is absorbed by green plants. Through photosynthesis, Ec[000000]f[16]LFthe plants release oxygen into the air. Air pollution raises the level of carbon dioxide in the air, which traps the Sun's heat.
Ec[000000]f[16]LBCastor and Pollux
BTwin stars in the constellation Gemini. These two stars were named for the twin sons of Leda, a queen of Sparta in Greek mythology. In Greek mythology, the twins Castor and Pollux were heroic warriors who were devoted to each other.
Ec[000000]f[16]LBCelsius scale
BA temperature scale that uses zero degrees as the freezing point of water and one hundred degrees as the boiling point of water. Before 1948, it was called the centigrade scale.
Ec[000000]f[16]LBCeres
BCeres was the first asteroid to be discovered. It was discovered on January 1, 1801 by the Italian astronomer Giuseppe Piazzi, who thought he had discovered a minor planet. Ceres, which is approximately 621 miles in diameter, is the largest asteroid discovered to date.
Ec[000000]f[16]LBIChallengerBIB disaster
BTheI Challenger Iwas a U.S. space shuttle that exploded seventy-three seconds after takeoff on January 28, 1986, killing the crew of seven. The disaster halted manned spaceflights for three years while the cause of the explosion was investigated and various features of the Ec[000000]f[16]LFspace shuttle were redesigned The blame for the disaster finally was placed on the faulty design of the O-ring seals, which are inexpensive ring-shaped elastic seals.
Ec[000000]f[16]LBcompass
BAn instrument used for finding cardinal directions on Earth. A compass, a type of small magnet, is affected by the magnetic field of Earth, causing the compass needle always to line up in a north-south direction; that is, pointing toward Earth's magnetic poles.
Ec[000000]f[16]LBcontinent
BOne of the seven major land masses on the surface of Earth that rise above sea level. The seven continents are Africa, Antarctica, Asia, Australia, Europe, North America, and South America.
Ec[000000]f[16]LBcoreB
The central section of a planet. Earth's core consists of metals such as iron and nickel and is partly liquid. The innermost core, however, is thought to be solid.
Ec[000000]f[16]LBcosmology
BThe branch of astronomy that involves the scientific study of the organization, content, form, and evolution of the universe.
Ec[000000]f[16]LBcosmonaut
BThe Russian term for a person trained for spaceflight; a Russian astronaut.
Ec[000000]f[16]LBcrater
BA bowl-shaped pit found on the surface of Earth and the Moon. Meteorites can create craters when they strike the surface of Earth and the Moon. The openings in volcanoes from which lava flows also are called craters.
Ec[000000]f[16]LBcrust
B
The outermost layer of rock and soil forming Earth's surface, which includes the continents and the ocean bottom. The crust is composed of a layer of basalt. On the continents, granitic rocks overlay the basalt. These rocks floated to Earth's surface when, early in its history, Earth was in a molten state.
Ec[000000]f[16]LBDeimos
BThe smaller of the two moons of Mars. The planet Mars was named for the Roman god of war. Deimos, which means "terror," was one of his companions.
Ec[000000]f[16]LBEarth-grazers
BAsteroids that leave their orbit between the planets Mars and Jupiter and fall towards Earth. Earth-grazers neither burn up in Earth's atmosphere nor fall to Earth's surface.
Ec[000000]f[16]LBearthquake
BA violent shaking or trembling of the earth caused by the slippage of Earth's crust along a fault. The breaking and shifting of rock strata within the earth creates shock waves, which are felt as tremors on Earth's surface. Earthquakes also can be caused by volcanic forces from within the earth.
Ec[000000]f[16]LBevaporation
BThe process by which a liquid is converted into vapor. On Earth, heat from the Sun causes the surface water from lakes, rivers, and oceans to evaporate; cooled in the atmosphere, the water vapor transforms into water droplets that form clouds.
Ec[000000]f[16]LBEvening Star
BThe planet Venus, when seen shortly after sunset, is quite bright in the western sky, and thus is called the Evening Star.
Ec[000000]f[16]LBFahrenheit scale
BThe temperature scale that uses 32 degrees as the freezing point of water and 212 degrees as the boiling point of water.
Ec[000000]f[16]LBfault
B
Faults, which originally are caused by earthquakes, are cracks, or fractures in the bedrock, at which earthquakes repeatedly occur. A fault shows where sections of Earth's crust move and have been displaced relative to each other by earthquake activity.
Ec[000000]f[16]LBfossil fuels
BCoal, petroleum, and natural gas, formed from the remains of plants and animals that lived millions of years ago, are examples of fossil fuels. When burned as sources of heat and fuel or by industry in manufacturing, fossil fuels produce carbon dioxide. Air pollution is caused by the burning of fossil fuels.
Ec[000000]f[16]LBGalileo Galilei
BGalileo Galilei was an Italian physicist and astronomer who lived from 1564 to 1642. His major contribution to science was the invention of the first complete telescope, which he used to study the Moon, the planets, and the stars.
Ec[000000]f[16]LBgas giants
BThe name given to Saturn, Jupiter, Uranus, and Neptune, the four large planets whose orbits lie beyond Mars. The four planets known as the gas giants were formed not from solid matter but from gases thrown off by the Sun. Pluto, the farthest planet from the Sun, is not considered to be a gas giant.
Ec[000000]f[16]LBGondwanaland
BThe name given to one of the two major continents that existed after Pangaea, the single supercontinent on Earth, began to break up and separate. Gondwanaland theoretically consisted of the land masses now known as South America, Africa, Australia, and Antarctica.
Ec[000000]f[16]LBgravitational pull
BThe force of gravity from a planet or star that pulls other bodies toward it. The gravitational pull of Earth holds the Moon in orbit around it.
Ec[000000]f[16]LBgravity
BA force of attraction. On Earth, this force attracts and draws all bodies in Earth's atmosphere toward the center of the earth.
Ec[000000]f[16]LBgreenhouse effectB
The glass construction of a greenhouse traps solar radiation; in this manner, the air within the greenhouse is warmed, enabling plants to grow even during the winter months. The term greenhouse effect describes the heating of Earth's lower atmosphere and surface Ec[000000]f[16]LFtemperature because of the Sun's heat, which has been trapped by high levels of carbon dioxide in the atmosphere; carbon dioxide, by absorbing infrared radiation from the Sun, prevents the release of the Sun's heat back into space.
Ec[000000]f[16]LBHalley's comet
BA famous periodic comet named for the English astronomer Edmund Halley, who lived from 1656 to 1742. Halley, who observed this comet in 1682, identified it as the same one witnessed by astronomers in 1531 and 1607. Based on this identification, Halley correctly Ec[000000]f[16]LFpredicted the comet's orbit and return close to Earth from outer space every seventy-six years. The comet reappeared in 1758 and again in 1835 and 1910. The most recent reappearance of Halley's comet occurred in 1986.
Ec[000000]f[16]LBhurricane
BA tropical cyclone, or violent, whirling windstorm, with winds exceeding seventy-five miles per hour. Hurricanes usually form in a low-pressure system over the warm, tropical waters of the western Atlantic Ocean between June and November. Barometric pressure at the Ec[000000]f[16]LFcenter of the storm drops rapidly and winds pick up speed as they rush towards the center. If the windstorm reaches shore, it can cause extensive damage to property.
Ec[000000]f[16]LBicecaps
BLarge masses of glacial ice covering the surface of Earth at the polar regions. The three icecaps on Earth include Antarctica, Greenland, and (on water) North Polar. The planet Mars also has icecaps.
Ec[000000]f[16]LBIsaac Newton
BSir Isaac Newton, an English mathematician and physicist, was one of the world's greatest scientists. Newton, who lived from 1642 to 1727, invented calculus; discovered the principle of gravity; and formulated laws of motion and theories on light.
Ec[000000]f[16]LBIshtar Terra
BThe larger of the two land masses on the planet Venus. As a land mass, Ishtar Terra is about the same size as the United States. Ishtar Terra was named after Ishtar, the Babylonian goddess of love.
Ec[000000]f[16]LBLaurasia
BThe name given to one of the two major continents that existed after Pangaea, the large, single supercontinent on Earth, began to break up and separate. Theoretically, Laurasia consisted of the present-day continents of North America, Europe, and much of Asia.
Ec[000000]f[16]LBlight-year
BThe common unit of distance measurement used in astronomy that is equal to the distance that light travels in a vacuum in one year. One light-year is equivalent to approximately six trillion miles.
Ec[000000]f[16]LBlightning
BA flash of light in the sky, caused by the discharge of atmospheric electricity between two clouds or between a cloud and the earth. Lightning constantly flashes in the clouds that cover the planet Venus.
Ec[000000]f[16]LBmagnetic field
BA force caused by the movement of electrical charges. Earth's magnetic field derives from a hot metal core located at the center of the planet. Earth's magnetic field causes compass needles to line up in a north-south direction, pointing to the magnetic poles.
Ec[000000]f[16]LBmeteor
BA meteoroid that burns up upon entering Earth's atmosphere. This is seen as a bright streak of light in the night sky. A meteor also is called a shooting star or a falling star. The compression of gases in Earth's atmosphere may create the heat that causes the meteoroid to burn. A Ec[000000]f[16]LFmeteoroid is a small, solid body of stone or iron that travels in orbit around the Sun. Meteoroids are remnants from the time when the solar system was created and the planets were formed. Most meteoroids have a mass of under one gram, but others are extremely large.
Ec[000000]f[16]LBmeteorite
BA meteoroid that has entered the gravitational field of Earth's atmosphere and falls to Earth's surface. A meteoroid is a small, solid body of stone or metal that travels in orbit around the Sun. Meteoroids are remnants from the time when the solar system was created and Ec[000000]f[16]LFthe planets were formed. Meteoroids also consist of the debris from disintegrated comets. Most meteoroids have a mass of under one gram, but others are extremely large. Meteoroids typically burn up upon entering Earth's atmosphere.
Ec[000000]f[16]LBmeteoroid
BA small, solid body of stone or iron that travels in orbit around the Sun. Meteoroids are remnants from the time when the solar system was created and the planets were formed. Most meteoroids have a mass of under one gram, but others are extremely large.
Ec[000000]f[16]LBMilky Way Galaxy
BA group of as many as one hundred billion stars, of which our Sun is one. Most of the stars that we see in the night sky belong to the Milky Way Galaxy.
Ec[000000]f[16]LBminor planets
BAnother name for asteroids, which are irregularly shaped, rocky objects that orbit the Sun largely in a path between the planets Mars and Jupiter. Asteroids may range in size from 621 miles in diameter to less than one mile in diameter. There are thousands of asteroids in our solar system.
Ec[000000]f[16]LBMorning Star
BThe name given to the planet Venus when it can be seen shining brightly in the eastern sky shortly before sunrise.
Ec[000000]f[16]LBNASA
BThe initials of the National Aeronautics and Space Administration. This U.S. government agency directs aeronautics research and the exploration of outer space.
Ec[000000]f[16]LBNewton's laws of motion
BThe English scientist Sir Isaac Newton, who lived from 1642 to 1727, discovered the three basic laws of motion. These laws state that a body at rest tends to remain at rest; a body in motion will continue in motion at constant speed in a straight line unless acted upon by an Ec[000000]f[16]LFoutside force; if a force does act upon a body in motion, the acceleration of the object is directly proportional to the force and inversely proportional to its mass; and for every action there is an equal and opposite reaction.
Ec[000000]f[16]LBNicolaus Copernicus
BA Polish astronomer who lived from 1473 to 1543. Copernicus discovered that Earth and the other planets in our solar system revolve around the Sun. Before his discovery, it was believed that Earth was the center of the universe, with the other planets and the Sun revolving around Ec[000000]f[16]LFit. Modern astronomy was built on the foundation of Copernicus's discovery.
Ec[000000]f[16]LBorbit
BThe path taken by planets and other celestial bodies as they revolve around the Sun. It takes Earth 365 days to orbit the Sun.
Ec[000000]f[16]LBozone layer
BA band of ozone, which is a form of oxygen, found in Earth's upper atmosphere. The ozone layer protects life on Earth from the harmful ultraviolet rays of the Sun.
Ec[000000]f[16]LBozone
BA form of oxygen that has three atoms per molecule.
Ec[000000]f[16]LBPangaea
BThe name given to the large, single land mass, or supercontinent, that scientists theorize existed 200 million years ago on Earth. This large, single land mass consisted of all the major land masses that we recognize today as the seven continents. Scientists theorize that Ec[000000]f[16]LFPangaea was centered near the South Pole.
Ec[000000]f[16]LBPercival Lowell
BAn American astronomer who lived from 1855 to 1916. Lowell believed that the lines visible by telescope on the surface of Mars were canals dug by intelligent creatures and predicted the possibility of life on Mars. The canals seen by Lowell were probably optical illusions, and we Ec[000000]f[16]LFnow know that there is no life on Mars. Lowell correctly asserted the existence of the outermost planet that we now call Pluto, although this planet's existence was not proven until 1930, fourteen years after his death.
Ec[000000]f[16]LBphases of the Moon
BThe visible appearance of the Moon in the night sky during the course of a month. The phases of the Moon include the new, or crescent moon; the first quarter; the gibbous moon waxing; the full moon; the gibbous moon waning; the last quarter; and the old moon. The Moon completes one Ec[000000]f[16]LFcycle of these seven phases in about a month's time; the Moon completes about twelve cyclical phases each year. The wordI month Icomes from the word ImoonI.
Ec[000000]f[16]LBPhobos
BThe larger of the two moons of Mars. The planet Mars was named for the Roman god of war. Phobos, which means "fear," was one of his companions.
Ec[000000]f[16]LBplanetoid
BAn earlier name for an asteroid. An asteroid, or planetoid, is a small celestial body that is considered a minor planet. Asteroids are irregularly shaped, rocklike objects whose orbit around the Sun lies mainly between the planets Mars and Jupiter. Asteroids may range in size from Ec[000000]f[16]LF621 miles in diameter to less than one mile in diameter. There are thousands of asteroids in our solar system.
Ec[000000]f[16]LBplate tectonics
BThe theory that explains major changes in the geological structure of Earth's crust, specifically with regard to the movement of plates, the sections of Earth's crust that float atop the mantle. The slow but constant motion of these plates explains the geological processes of continental Ec[000000]f[16]LFdrift and mountain building. The plates collide as they move, causing one plate to slide under another plate. Earthquakes and volcanic activity usually occur at the boundaries between plates.
Ec[000000]f[16]LBplates
BThe sections of Earth's crust that float atop the mantle and move steadily and slowly in response to forces deep within Earth. The movement of the continents, which rest on the main mass of these sections, or plates, is called the continental drift. The separate plates Ec[000000]f[16]LFcovering Earth's surface are made of a solid material that is many miles thick in its depth.
Ec[000000]f[16]LBprehistoric
BThe time before recorded, or written, history.
Ec[000000]f[16]LBPtolemy
BA Greek-born astronomer who lived in Alexandria, Egypt, during the second century A.D. He described the solar system as a system of clear spheres, one inside the other, with Earth at the center and the planets, the Sun, and other stars revolving around it. This concept of the universe prevailed for about 1,500 years.
Ec[000000]f[16]LBquicksilver
BAnother name for mercury, which is a heavy, silvery metallic element. Mercury, which is liquid at room temperature, is used frequently in thermometers because it rapidly expands or contracts in response to temperature changes. The element quicksilver was thus named for its Ec[000000]f[16]LFquickness. Quicksilver also is called mercury, after the fleet-footed Roman messenger god, for whom the planet Mercury is named. The planet Mercury, the planet closest to the Sun, orbits quickly, or moves rapidly, around that celestial body.
Ec[000000]f[16]LBradiation
BThe emission of energy in the form of particles or electromagnetic waves; also, a form of heat transfer that takes place by means of infrared energy. Objects that are different temperatures give off, or emit, different kinds of radiation.
Ec[000000]f[16]LBradio telescope
BA device for receiving radio waves emitted by stars and galaxies in outer space. A reflector on the radio telescope intercepts the radio waves and then focuses the waves onto a small receiver. The signals are analyzed electronically, enabling astronomers to learn more about distant Ec[000000]f[16]LFstars and galaxies. Quasars and pulsars were discovered through the use of radio telescopes.
Ec[000000]f[16]LBradioactivity
BThe emission of radiant energy, in the form of particles or electromagnetic rays, resulting from the spontaneous disintegration of certain unstable atomic nuclei.
Ec[000000]f[16]LBreflecting telescope
BA type of optical telescope that uses a large, bowl-shaped mirror at its base to collect and focus light so that the Moon, the stars, the planets, and other celestial bodies visible in the night sky can be studied closely by astronomers.
Ec[000000]f[16]LBRing of Fire
BA term used to describe the perimeter of the Pacific Ocean, which is characterized by a high concentration of active volcanoes and earthquake activity. Areas on the Pacific coastline that form part of the Ring of Fire include California and Japan.
Ec[000000]f[16]LBrobot lander
BA mechanical device that is sent to the surface of the Moon or other planets to gather data as well as soil and rock samples, which then are sent back or transmitted to laboratories on Earth for analysis.
Ec[000000]f[16]LBrotation
BThe spinning motion of a planet or other celestial body around an imaginary straight line, which is known as its axis. Earth's axis runs between the North Pole and the South Pole.
Ec[000000]f[16]LBsatellite
BA moon that revolves around a planet. The Moon is Earth's satellite; the planet Mars has two satellites. A satellite also can be a man-made object launched into outer space by rockets, such as the various communication satellites that orbit Earth.
Ec[000000]f[16]LBshooting stars
BThe popular name for meteors, which are streaks of bright light that appear suddenly in the night sky. Meteors result from meteoroids, which are small, solid bodies of matter traveling through outer space that burn up upon entering Earth's atmosphere. A meteor is not a star at all, Ec[000000]f[16]LFbut it does resemble a brightly lit star moving swiftly across the sky.
Ec[000000]f[16]LBsolar eclipse
BThe blocking of the Sun's light by the Moon, when the Moon passes, in its orbit, between the Sun and Earth. If the Moon completely blocks the Sun in a total solar eclipse, the eclipse will create a momentary, dusklike darkness in certain areas on Earth.
Ec[000000]f[16]LBsolar transit
BThe movement of a planet as it crosses in front of the surface of the Sun.
Ec[000000]f[16]LBsolar wind
BA constant stream of electrically charged particles given off by the Sun. These particles, which flow constantly through the solar system, move through space at a high speed. The magnetic fields of Earth trap the solar winds; however, those electrically charged particles that do reach Ec[000000]f[16]LFthe atmosphere in Earth's polar regions create the aurora. The aurora, or luminous streams of light, are caused by the collision of the electrically charged particles with gases in Earth's atmosphere.
Ec[000000]f[16]LBspace probe
BA spacecraft which has been designed to travel in close proximity to or within the atmosphere or even on the surface of other planets in order to collect scientific data about them. The data, which may consist of photographs, temperature readings, atmospheric composition, or the Ec[000000]f[16]LFcreation of surface maps through the use of radar, is then transmitted to scientists on Earth for analysis.
Ec[000000]f[16]LBspace station
BA spacecraft that has been designed to remain in orbit and be occupied by humans for a long period of time, in order to serve as a base for laboratory research in space or as a station from which to launch other, smaller spacecraft.
Ec[000000]f[16]LBsupercontinent
BThe large, single land mass on Earth that scientists theorize existed 200 million years ago. This large, single land mass, known as Pangaea, consisted of all the major land masses that we recognize today as the seven continents. Scientists theorize that Pangaea was centered near the South Pole.
Ec[000000]f[16]LBterra
BA Latin word meaning "land" or "ground." This term refers to highland areas, similar to Earth's continents, that astronomers have located on the surface of the Moon and planets such as Venus.
Ec[000000]f[16]LBterraforming
BThe futuristic transforming of the surface and atmosphere of another planet to resemble the surface and atmosphere of Earth.
Ec[000000]f[16]LBITheBI BIWar of the WorldsBIB
BA futuristic novel by the English writer H.G. Wells, which was first published in 1898. Wells lived from 1866 to 1946. A dramatization of this novel, presented on radio in 1938 as an actual newscast, reported that Martians had landed in New Jersey and were ready to attack the Ec[000000]f[16]LFUnited States. Listeners panicked and the army was called out to fight the invaders. It took several hours for the panic to subside.
Ec[000000]f[16]LBtornado
BA violent, high-speed, rapidly whirling column of air, shaped like a funnel cloud, with central wind speeds that can reach 300 miles per hour. A tornado extends downward from a cumulonimbus cloud, which is a dense, vertically shaped cloud associated with thunderstorms. The air Ec[000000]f[16]LFpressure at the center of a tornado is extremely low. Tornadoes are highly destructive and can cause considerable property damage and loss of life.
Ec[000000]f[16]LBTrojan asteroids
BAsteroids that remain in a consistent formation in Jupiter's orbit.
Ec[000000]f[16]LBtyphoon
BA tropical cyclone that originates in the western Pacific Ocean, especially in the South China Sea.
Ec[000000]f[16]LBultraviolet rays
BElectromagnetic waves whose wavelengths are shorter than that of visible light. Ultraviolet rays, which emanate from the Sun, are harmful rays that are filtered or blocked out by the protective ozone layer that surrounds Earth. Ultraviolet rays can be detected Ec[000000]f[16]LFthrough the use of special instruments or films.
Ec[000000]f[16]LBuniverseB
Every celestial body that exists, including our own Sun and solar system, the stars, asteroids, quasars, and other galaxies. The universe is vast and stretches far beyond even the imagination of humans.
Ec[000000]f[16]LBvolcano
BAn opening in Earth's surface through which molten rock, known as lava, erupts from the mantle within Earth's interior. A cone-shaped mountain forms a crater around this opening.
Ec[000000]f[16]LBVulcan
BThe Roman god of fire and the name given to an undiscovered planet that was mistakenly believed to orbit the Sun inside of Mercury's orbit. A theory of gravity developed by Albert Einstein proved that the planet Vulcan did not exist.
Ec[000000]f[16]LBX-rays
BBands of electromagnetic radiation characterized by short wavelengths with very high energy and frequency. Celestial objects in the sky emit, or give off, X-rays. Special instruments have been developed to allow astronomers to study space through the detection of these X-rays.
Ec[000000]f[16]LBX-ray astronomy
BThe study of space through the detection of X-rays by satellites in orbit outside of Earth's atmosphere. Celestial objects in the sky emit, or give off, X-rays. X-rays are bands of electromagnetic radiation characterized by short wavelengths with very high energy and frequency.
