Science Dictionary

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!

By Craig Freudenrich, Ph.D.

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.

By Craig Freudenrich, Ph.D.

A light-year is a way of measuring distance, which doesn't make much sense because "light-year" contains the word "year," which is normally a unit of time. So, how does a light-year measure distance?

By Valerie Stimac

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"?