Why is it when you spin something, it stays on the plane that you spin it on? Does gravity not affect it? I would think that it would... in b4 gb2/4th grade science/
As you probably know, back before the sun was a star it was just a big cloud of dust left over from when another star exploded. The dusk cloud was spinning as one large mass, and so all the particles were moving in the same direction. Over time, as these particles accreted into planets they kept their same counter-clockwise(?) direction.