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Q & A: gravity and planets' spin

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Most recent answer: 04/17/2014
Why does earth or any other planet rotate about its axis under the influence of gravity of star? I thought gravity only affected its revolution.
- saroj (age 18)
biratnagar, nepal

Gravity from the star doesn't play a direct role in creating the spin. The spin is left over from accidental angular momentum of the cloud that formed the planet.  Gravity between parts of the planet is important in causing the planet to form and then holding it together while it spins.

Mike W.

(published on 04/17/2014)

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