7 months ago
Last edited at 10:50AM on 8/20/2013
Gravity does not cause spin. Initial centrifugal forces that are present during an object's creation (like a planet) are what causes spin.
Earth's gravity exists due to its mass, and has nothing to do with Earth's rotation. Earth's rotation is due to the speed of which Earth was given during the 'settling down' phase 4.5 billion years ago. Earth's gravity isn't slowing down Earth's rotation (the Moon's gravity is, though). Even if Earth stopped rotating, we would still have gravity (mind you, there would be slight changes in gravity at the poles vs the equator; but in general, gravity would still exist because Earth would still have mass).
Gravity does not cause spin. If you use the Newtonian model for gravity, then the force of gravity is only dependent on the mass of the two bodies and their separation of their centers of mass. Therefore, gravity is a universal property of all objects and is not considered in ordinary.