Moon Splits from Earth!

Where does the Moon come from? The leading hypothesis is the "Giant Impact Hypothesis" also known as the Big Splash or Big Whack (...with homage--vocabulary flash!--to the Big Bang.)

This theory says...

A large Mars-size molten object named Theia crashed into the young Earth at an oblique angle. The object sank within Earth's molten core. But the impact spun off debris that orbited the Earth for a short while and then coalesced into the a single object, the moon.

This coalescence may have taken less than a month but definitely no more than a century. PDQ in astronomical terms. (Pretty Darn Quick)

After the impact the Earth was spinning much faster than now, with an earth day only 5 hours long.

If your were alive back then and wanted a good night's sleep of about ten hours, you'd have to sleep through two nights. And two days...

...three days if you're a teenager. Of course after that you'd pull three all-nighters in a row to be awake for a normal 15 hours.

It seems there is still lots of debate over this hypothesis. There's some good evidence both fer and agin it...same for the other hypotheses.

Isotopic similarities between earth rocks and moon rocks brought back by Apollo astronauts gives some impetus to the Big Splash.