Science Dictionary

Do you know what a meteor is, or what scientists mean when they are talking about cryogenics? Our collection of science terms explains the meaning of some of the most common scientific ideas.

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How Carl Sagan Worked

He may have been born in Brooklyn, but Carl Sagan was gunning for the stars as soon as he arrived in this world. Get to know the scientist whose infectious delight in the universe still holds us spellbound.

How Stephen Hawking Worked

He ventured to the abyss of black holes, wagered on the information paradox and floated around in zero gravity. Meet the man, the legend, the super scientist: Stephen Hawking.

How do you win a Nobel Prize?

How cool would that be to stand amongst the company of fellow laureates like Mother Teresa or Albert Einstein? We have some ideas for scoring you one (nominating yourself isn't one of them).

How are frequency and wavelength of light related?

Frequency has to do with wave speed and wavelength is a measurement of a wave's span. Learn how frequency and wavelength of light are related in this article.

10 Cool Things You Didn't Know About Stephen Hawking

He was born exactly 300 years after Galileo died. He never won a Nobel Prize, although he was awarded a guest spot on “The Simpsons.” What else do you know (or not know) about this acclaimed physicist?

How did the universe begin?

You've heard of the big bang, of course, but do you have any idea as to what was happening during that massive flurry of activity billions of years ago?

What are dark matter and dark energy?

Every day, astronomers unravel a little more of the universe's inner workings, but the jury is still out on 95 percent of its contents.


Quasar, or Quasi-stellar Object (QSO), a starlike object displaying an unusually large red shift.

Magellanic Clouds

Magellanic Clouds, three irregularly shaped galaxies that lie some 150,000 to 200,000 light-years from earth.

Laplace, Pierre Simon de

Laplace, Pierre Simon de, Marquis de Laplace (1749-1827), a French astronomer and mathematician.

Galilei, Galileo

Galilei, Galileo, generally called Galileo (1564-1642), an Italian astronomer, physicist, and mathematician.

Kepler, Johannes

Kepler, Johannes (1571-1630), a German astronomer. Kepler's three laws of the motions of planets are basic to the understanding of the solar system.

Bond (family)

Bond, the family name of two United States astronomers, father and son. They were pioneers in the use of photography in astronomy.


Draper, the name of two United States scientists, father and son.

Herschel (family)

Herschel, the family name of three British astronomers.

Pickering (family)

Pickering, the name of two brothers who were astronomers. They were born in Boston, Massachusetts.

Struve (family)

Struve, the family name of three noted astronomers.

Satellite, Artificial

Satellite, Artificial, a man-made object that orbits the earth, the moon, the sun, or any other celestial body.


Calendar, a system of dividing time into convenient periods of days, months, and years.

Cosmic Rays

Cosmic Rays, high-energy radiation consisting chiefly of subatomic particles moving at nearly the speed of light.


Eclipse. An eclipse of the sun, or solar eclipse, occurs when the moon's shadow sweeps across the earth.


Meteor. As the term is commonly used, a meteor is a small celestial body that enters the atmosphere of the earth.


Meteorite, a meteor that reaches the earth's surface. Meteors are naturally occurring objects that enter the earth's atmosphere from space, traveling at high speed.


Planetarium, is an educational device for showing the locations and movements of the planets and other objects in the universe.


Seasons, the four divisions of the year, called spring, summer, autumn (or fall), and winter.