What is the cause of the planets (and the Suns) rotation
I think it's due to the conservation of angular momentum, i could be wrong though.
vincentm is correct. Particles falling into a gravity well travel in a spiral path. It is not unlike flushing a toilet. Traveling in a spiral path allows them to preserve momentum until absorbed. This imparts spin to the accreting body [star, planet, etc.].
Furthermore, the natural state of affairs is that rotating objects will continue to rotate until something comes along to stop it. For the larger bodies in the solar system, there aren't any significant effects on their rotation. But for the smaller bodies....
The main effect on rotation is tidal forces, which don't work to stop rotation, but to synchronize it with revolution. The Earth is big enough and near enough (and has had enough time) to coerce the moon into making one rotation once per revolution. Similarly, the Sun has locked Mercury into making 3 rotations per 2 revolutions. You also see this with many (most?) of the moons in the solar system.
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