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Old December 20th, 2007, 11:17 PM

Baron Munchausen Baron Munchausen is offline
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Default Re: Planet Rotation Speeds

Quote:
Spoo said:
Quote:
MasterChiToes said:
The Terrestrial planets can be expected to turn slower due to 'tidal forces' dissipating their rotational angular momentum. If you check out the length of a day on ancient earth, it was much shorter than the Jovian planets.

In general, for a stable climate, I would agree that smaller planets better turn slower.
I think you would have to make a number of assumptions about the event that formed the Moon to know what Earth's original rotation rate was. Although, I agree that it must have slowed since then.

Also, tidal forces would have little effect on Mars (two very small moons), and none on Venus (no moons) - although something must have happened to Venus to make it rotate "backwards". It's generally thought that terrestrial planets with a satellite as large as the Moon are very rare. However, Mercury's rotation is very strongly determined by tidal forces from the Sun.
Venus's odd rotation (very slow retrograde) combined with the entire surface being only ~500 million years old (evenly random distribution of craters over entire planet = same age for entire surface, the number of craters gives the rough age estimate) adds up to one known cause: a huge farking impact event.
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