If the Earth turns all the way around every 24 hours, then why are some days longer than others? And why do we have winter and summer? See the answers for yourself—in a matter of seconds.
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.
Online Resource, Article
Until the late 18th century, most people believed the Earth was about 6,000 years old. Hutton changed this belief by proposing that geologic forces operate at the same rate today as in the past.