Planet Earth. Part 2

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Summary

Earth's Moon was born in a catastrophic collision more than 4 billion years ago. It started out very close to the planet but has been moving away ever since. It's drifting away every year. The syst...

Earth's Moon was born in a catastrophic collision more than 4 billion years ago. It started out very close to the planet but has been moving away ever since. It's drifting away every year. The system's center of mass is currently inside Earth, though that is slowly changing. In a few billion years, the barycenter will eventually move outside the Earth as the Moon recedes. At that point the Moon will be promoted to planetary status. For that to happen the Earth and the Moon have to survive a host of remote catastrophe scenarios along with the predicted swell- ing of the Sun into a red giant in approximately five billion years, which might engulf and vaporize our civilization unless we figure out a way to relocate.

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