Nobody knows, and in reality no answer will ever fully suffice. The length of Earth's day has a solid answer, on the other hand. Sort of.

The U.S. Treasury $250 billion or more a year in lost taxes.

Snakes have no visible ear, so they don't hear sounds as we do.

Sandy was a storm with perhaps more names than any in history.

Wild turkeys feed on the ground, which may have something to do with the myth that they can't fly.

Lizards work out for the same reason a guy at the gym might: as a display of strength.

Vultures sniff out their next meal from over a mile away.

You’ve heard the general advice. But here are the specific (and simple) tips.

A new study finds that those who volunteer their time feel less rushed.

Earth is a perfect worlds from the perspective of harboring life. But …

The next solar eclipse will grace skies over much of the United States this Sunday (May 20). The annular eclipse will create a ring of fire.

The biggest full moon of 2012 — dubbed a “supermoon” by some — will light up the evening sky Saturday.

There's something very unnatural about this sea.

One in a series of strange images to decipher.

Another strange image to decipher.

Another puzzling image to decipher.

Another puzzling image to decipher.

Another interesting image to decipher.

Another puzzling image to decipher.

Another puzzling image to decipher.

Another puzzling image to decipher.

Another strange image to decipher.

Another puzzling close-up image to decipher.