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Why do planets, stars and moons spin? Are there any that don't?
by hackaflocka 13y ago
Why do planets, stars and moons spin? Are there any that don't?
- wellboy 13y agoMy armchair attempt would say that a star/moon would only NOT spin if at their creation, the clouds of material came 100% from all sides equally. Normally though, stars or planets are caught from clouds catching and revolving around each other for a couple of million years until the condense to a solid object. Thus the spin.
- teamonkey 13y agoClassically, mathematically, the answer is conservation of angular momentum. As matter falls on to the body the body needs to rotate faster to conserve the energy of the system. A rotation happens if there is even a tiny asymmetry in the accreting matter. In the case of our own Moon, one side is more massive than the other and over the course of millions of years became tidally locked so that the heavier side always points towards the Earth.
- TheCoreh 13y agoIt has to do with the total angular momentum of a system composed of multiple smaller bodies. (Like the dust/debris cloud during solar system formation) This minute physics video (about the shape of the solar system) explains it probably better than I can put into words myself: http://www.youtube.com/watch?v=tmNXKqeUtJM http://www.youtube.com/watch?v=tmNXKqeUtJM The relevent part starts at about 1:03, but I recommend watching the whole thing.