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.


The big bang theory is well-known, but there are many misconceptions about it. Like what? Let's start with this one: There was no bang.

Modern science allows us to break atoms down into tiny components. But can scientists use their mighty machines to recreate the foundation of the universe?

Some scientists believe that space is infinite. But is it? If it isn't, what form does space take? Is it a dodecahedron or a triple torus?

Space collisions are the universe's car wrecks. Only in outer space, it's stars, asteroids and even galaxies doing the smashing.

So much about galaxies remains a mystery. We know what they're made of and that we live in one (the Milky Way), but we're not sure how they form and evolve.

When a star dies, it becomes a black hole. Once something passes through the it's gone for good, never to be seen or heard from again. If we lived next to a black hole, would it suck us in too?

For decades, stargazing scientists have been facing their own darkness on the edge of town as they try to explain one of astronomy's greatest mysteries: dark matter. Have they been successful, or will the universe carry its secrets for a long time?

While routinely scanning the stars, NASA scientists came across something they didn't expect to see: a vast area of space empty of stars, planets and matter.

Scientists announced the discovery of the largest known planet in the universe. TrES-4 has a density similar to balsa wood, and some say this gas giant could float on water. Learn why this planet is so puzzling and how planet hunters make amazing discoveries like these.

The Freemasons is a secret organization that began in the 1700s and is still in existence today. Who are the Freemasons? And what do they do in their secret meetings?

There's a 45-million-ton asteroid out there with Earth's name on it. In 2029, it'll be closer to us than our moon is. And that's not even the fly-by that scientists are worried about.

A black hole occurs when a massive star dies -- its enormous mass implodes and becomes so heavy that it bends space. So how do astronomers detect something that they can't see?

How do scientists find details about the early days of our solar system? One way is to investigate comets. Find out how the Deep Impact spacecraft fired an impactor into Comet Tempel 1 to get some answers.

Every November, the Leonid meteor shower fills the sky with "shooting stars." This year, the shower is expected to peak twice. Learn how Leonid and other meteor showers work.

Polymer crystals are amazing in that they can absorb many times their size. In fact, one pound of these crystal flakes can hold up to 50 gallons of water. Find out what these polymer crystals are and why they are able to absorb so much water.

Eros is 21 miles long and 8 miles thick -- a mini planet! Explore the mission that landed on this asteroid after orbiting it for a year!

Comets are remarkable pieces of our universe's past, and they tell us a great deal about how the universe was formed. Learn about the long but rewarding process of discovering and analyzing comets.

We've all heard about this prestigious prize, but why is it such an honor, exactly? Learn the history and process of the awards and the winners, and see what makes the Nobel Prize such a distinguished accomplishment.

When satellites go off to places like Jupiter or Saturn (or even out of the solar system), they follow crazy orbits. They will often loop around a planet to get a "gravity assist" or "gravity boost." How does that work? I know the Galileo probe looped around Earth twice to get a boost, and the Pioneer and Voyager probes used Jupiter.

Have you ever really thought about the scale of the universe? A good starting point is the teaspoon.

If you took all of the matter in the universe and you pushed it all into one corner, how much space would it take up? I am trying to understand how much of the universe is 'empty.'

My fiancee gave me a 1 carat diamond in my engagement ring. What is a carat? And how does it relate to a karat, as in "18 karat gold"?

A light year is a way of measuring distance. That doesn't make much sense because "light year" contains the word "year," which is normally a unit of time. Even so, light years measure distance.