## The Earth moves in an approximately circular orbit around the sun. Therefore, the centripetal force must point towards the sun. Where does?

Question

The Earth moves in an approximately circular orbit around the sun. Therefore, the centripetal force must point towards the sun. Where does the centripetal force come from?

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General Physics
4 years
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## Answer ( 1 )

This was what was behind the famous story of Newton and the apple.

What force COULD attract things to the earth?

The apple fell and he realized that it MIGHT be gravity.

On analyzing Kepler’s laws he concluded that it could be gravity if and ONLY if gravity a) passed through space and b) reduced with distance according to 1/R^2 and c) was proportional to each of the masses involved.

Latter experiments by Cavendish supported this proposal.

It is now known as the Universal theory of Gravitation.

F = GMm/ R^2

Gravity hold planets, moons, suns and galaxies in a perpetual state of orbits.