Earth rotates how fast

Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits.

See Subscription Options Already a subscriber? In scientists made a startling discovery. They found that, instead of slowing down, the Earth has started to spin faster. It is now spinning faster than at any time in the last 50 years. In fact, the shortest 28 days on record all occurred during Finally, at about 17, miles per hour, the centrifugal force at the equator would match the force of gravity.

Earthquakes, tsunamis, large air masses, and melting ice sheets can all change the spin rate at the millisecond level. A large air mass can have the opposite effect, slowing our spins a smidgen like an ice skater who leaves her arms out instead of drawing them in. About 4. At that time, Odenwald calculates our planet was probably shaped like a flattened football and spinning so rapidly that each day might have been only about four hours long.

We had better hope not! A controversial theory suggests that life could pre-date Earth. But we're not quite ready to trash general relativity. Sign up to receive Popular Science's emails and get the highlights. Since the formation of the moon, the rate that Earth spins has been slowing down by about 3. This post has been updated.

It was originally published on May 17, Ask Us Anything. We live in a universe of extremes.