Did The Earth Give Rise To The Moon?

Whenever it seems there just aren’t enough hours in a day, think about this: Once the Earth might have spun so fast that a day lasted two-to-three hours.

That’s almost twice as fast as the once-prevailing theory of five hours. But, you see, a day in five hours wouldn’t have been fast enough.

It’s all in a new theory from a Harvard planetary sciences professor and an investigator at the Search for Extraterrestrial Intelligence Institute (SETI) about how a planet collided with the Earth to form the Moon.

The theory about the collision isn’t so new, but the how-what-and-when by Harvard’s Sarah Stewart and SETI’s Matija Cuk is putting a whole new spin on it. (Nope. Couldn’t resist.) Published in mid-October in the journal Science, the work by Stewart and Cuk has received attention from the likes of the Washington Post and the SlashGear website.

Scientists and historic thinkers — including one George H. Darwin, son of Charles — have long held the theory that the Moon was created in a collision between the Earth and another smaller planet, according to a summation on Stewart’s Harvard website.

In that theory, the Earth was spinning faster than today, but much more slowly than now theorized, at around the rate of five hours to a day. However, that  idea has been challenged by new research that reveals that the composition of the Earth and the Moon are a lot alike — isotopic twins even. So much alike that one of them couldn’t have been leftovers from this other planet.

Stewart and Cuk set out to explain the discrepancy between the old idea and the new findings. And with the help of the modern scientific miracle of fast computers with enough storage capacity to image extremely cool graphic models — they arrived at an answer: A smaller planet called Theia (she’s the mother of the Moon goddess Selene) did indeed collide with the planet called Earth, but the Earth was spinning almost twice as fast as originally conceived. Theia hit the Earth so hard that it buried itself down to the Earth’s mantle, effectively vaporizing itself and part of the Earth with it.

The Earth, spinning as fast as it was, spun off some of the earthly material broken apart in the impact. But that Earth-begotten material went only so far. It stabilized itself, as did the Earth, until new the celestial bodies and the Sun achieved a gravitational interaction called orbital resonance.

All this grand thinking sounds mystical somehow, doesn’t it? But that’s the new theory, based on the old theory, that explains the new science.

AJ Plunkett is a freelance writer in Virginia with experience in covering defense and aerospace industries, as well as health care issues. AJ blogs via Contently.com.

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