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Orbiting Planets' Direction

  1. Jan 1, 2010 #1
    Happy New Year Everyone!
    Anyways, I have an interesting question. I have no background on astronomy, but came across some of it while studying for AP Physic C - Mechanics, where it covers Kepler's law and such. Although this was random, I wondered about this: If there are a lot of planets orbiting around the sun, do they all rotate in the same direction? If so what direction (e.g. clockwise) and why that direction? Would that direction be chosen initially be caused by the direction everything by the Big Bang and stay that way since every planet seems to be in "equilibrium" now? As I have mentioned I have no background in astronomy, so it would be nice if you could explain some of the technical terms or link it to some analogy. Thanks :)
  2. jcsd
  3. Jan 1, 2010 #2
    They all orbit the Sun in the same direction even though they rotate on their own axes in different directions. The main reason for the common direction of orbital motion is because the Sun and planets exchanged angular momentum and now all orbit, more or less, in the same direction. There is a certain amount of tilt/inclination to the orbits of the planets so the alignment isn't perfect, but that's believed to have come from mutual interactions between the planets. The motion of the whole system doesn't have anything to do with the Big Bang - that was too long ago - but may have something to do with the Galaxy's gravitational field and the Sun's orbit around it.
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