When does a 12-inch ruler look shorter than it really is? When it's fast on the move. In fact, at the speed of light, it would shrink to nothing. See length contraction for yourself ... at a safe speed.
Confused about fusion? You won't be once you've completed this experiment, which demonstrates how a strong nuclear force can fuse two protons that naturally repel each other.
Talk about a long-term power source. For billions and billions of years, the Sun has been giving off energy that equals 4 x 1026 watts. What keeps the Sun burning so bright?
Who said daydreams are a waste of time? One of Einstein's flights of fancy led to the equivalence principle—the knowledge that while an object is in free fall, it's free of gravity's effects.
Where to begin when a Web search turns up millions of sites about Einstein? Let us point you to some of the best—from Time's person of the century profile to a black hole animation.
In a Yao initiation ceremony, a 13-year-old boy jumps off a ladder, freeing his soul to travel to divine realms. Now he's ready to learn the Taoist teachings. Explore more cultural rites of passage.
Altars decorated to welcome ancestors home for the New Year, a Mid-Autumn Festival where kids parade through their neighborhoods in masks and receive toys ... take a look at Vietnamese traditions, past and present.
Meet one of the world's most influential scientists. Construct a compass and a flashlight. Find out how to pop through a wormhole. And further explore physics with these 10 kid-friendly titles.
Perfection certainly wasn't something to strive for, according to Einstein. In fact, he believed that messing up was a part of being successful—an idea that, itself, has proven relevance.
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The mountain-building processes of folding and faulting take many millennia on Earth—and a matter of minutes in the lab. Learn how even small models provide a big-picture view of our dynamic world.