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

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.

By Carolyn Snare

What exactly are asteroids? And what was the NEAR Shoemaker mission about?

By Craig Freudenrich, Ph.D. & Yara Simón

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.

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

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.

By Jacob Silverman

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.'

How does 24-karat gold relate to a 1-carat diamond in an engagement ring? It turns out there's a difference between these identically sounding measurements.

By Kathryn Whitbourne

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

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

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

So much about galaxies remains a mystery. We know what they're made of and that we live in one (the Milky Way), but how many galaxies are in the universe?

By Craig Freudenrich, Ph.D.