Science Dictionary

The kilometer (km) is a standard unit of measurement used in the metric system. Derived from the French "kilomètre," the unit is used to measure length and distance along a straight path.

By Mitch Ryan

In any scientific research, there are typically two variables of interest: independent variables and dependent variables. In forming the backbone of scientific experiments, they help scientists understand relationships, predict outcomes and, in general, make sense of the factors that they're investigating.

By Marie Look

Physicist and cosmologist Stephen Hawking was a fierce spirit who symbolized the foibles and complexities inherent in human nature. Learn more about him by taking our quiz.

By Nathan Chandler

The world often seems chaotic and events appear to occur randomly, but what's the difference between chaos and randomness?

By Mitchell Newberry

Scientists are still trying to figure out the essence of dark matter. If they do, will it lead only to greater understanding, or can we develop new technologies?

By Patrick J. Kiger

Everyone knows that nothing travels faster than the speed of light, but how does the speed of dark compare? Read on to find out!

By Bambi Turner

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.

By Jacob Silverman

He starred with Superman, drove the getaway car at Pluto's demise and was voted sexiest astrophysicist by People magazine. Is there anything Neil deGrasse Tyson can't do?

By Laurie L. Dove

He is famous for a phrase he never said, for wearing turtlenecks and for hosting the original 'Cosmos' TV series. As enthusiastic about the stars as he was about marijuana, Carl Sagan led a very surprising life.

By Laurie L. Dove

If you have a theory that potato chips are making you fat (with the proof being your expanding waistline), you've just used two scientific terms in a very unscientific way.

By Beth Brindle

He built President Eisenhower an indoor golf-training machine, analyzed the Zapruder film and searched for an Egyptian pyramid's treasure chamber using cosmic rays. Aren't you dying to meet this wide-ranging scientist?

By Nicholas Gerbis

The man who had some theories about relativity was also an eccentric who gleefully eschewed socks, dodged German military service and spurned social conventions.

By Nicholas Gerbis

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?

By Robert Lamb

So much of our cosmological history starts with the much-discussed Big Bang, but what led up to that cataclysmic moment? And did time even exist back then?

By Robert Lamb & Patrick J. Kiger

Nobel prizes offer lots of prestige and big payouts. But how do you become eligible for one? And can you lobby for yourself?

By Dave Roos

Planck's constant, which made an appearance in the Netflix series "Stranger Things," is one of the most important differences between reality at the atomic and subatomic level and what we can see around us.

By Patrick J. Kiger & Austin Henderson

Having one Nobel Prize winner in the family is a huge accomplishment. But the extended Curie family had five winners – and one was even awarded twice. How did they get so smart?

By Jennifer Marquez

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.

By HowStuffWorks.com Contributors

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.

By Marianne Spoon

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.

By Marianne Spoon

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 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?

By Craig Freudenrich, Ph.D.

We take much for granted about our universe, like it's getting bigger. What if the universe stopped expanding and started collapsing inward with a giant crunch?

By William Harris

Payne-Gaposchkin, Cecilia Helena (1900-1979) was a British-born astronomer who became an authority on variable stars (stars that change in brightness) and the structure of the Milky Way Galaxy.

Al-Tusi, Nasir al-Din (1201-1274) was one of the greatest scholars of his time and one of the most influential figures in Islamic intellectual history.