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I Why does the Earth rotate?

  1. Mar 27, 2017 #1
    When I googled it, I wasn't satisfied with the answers from various sites...some sites like universetoday.com gave me a glimpse but it was totally theoretical and based on assumption.
    Also I would like to know why some planets have retrograde rotation; what might have caused them to and why do they not return to their original rotation? I assumed they originally rotated anticlockwise...
     
  2. jcsd
  3. Mar 27, 2017 #2

    mfb

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    Our solar system started with a (more or less random) total angular momentum. As result, all the planets orbit in nearly the same plane, and most planets also rotate in this plane and with the same direction.
    The rotation of planets only changes if something hits them or if something leads to a significant torque.

    Something slowed down Venus - probably tidal interactions with its dense atmosphere, but impacts could have contributed.

    Uranus has a weird axial tilt - probably from impacts.
     
  4. Mar 27, 2017 #3

    BvU

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    If it was specifically this link that triggered
    then I don't think much can be done to improve your satisfaction ...:frown:
    It seems quite plausible to me and I assume that's about the best you can get -- after all there aren't any witnesses. I'm not sure we have enough info from planets in other solar systems to improve on this.
     
  5. Mar 27, 2017 #4
    Would a moon of Uranus that rotates in the opposite direction of Uranus be considered to have progade rotation because it rotates the same way as the Sun?
     
  6. Mar 27, 2017 #5

    mfb

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    The naming scheme follows the rotation of Uranus. The five big moons and the smaller inner moons all orbit in the same plane as Uranus' rotation. The outer irregular moons mainly orbit retrograde.
     
  7. Mar 27, 2017 #6
    Retrograde orbit or retrograde rotation?
     
  8. Mar 27, 2017 #7

    mfb

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  9. Mar 28, 2017 #8
    Retrograde rotation
     
  10. Apr 16, 2017 #9

    Chronos

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    Moons and planets sometimes get 'bumped' off their original axis off rotation. Uranus, for example, evidently had a fender bender in the past that left it tilted sidewise. It is essentially impossible to pin down when these nudges may have occurred. The early solar system is believed to have been a very busy place. Numerous planetesimals were vying for promotion and coalescence was the means. These events were not necessarily gentle.
     
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