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If the earth started spinning clockwise

  1. May 3, 2012 #1
    If the Earth started spinning clock wise but still in the same orbit it is in now. What would some effects be? Also if the Earth started orbiting in the opposite direction would there be any side effects? And does the Earth even spin counter clockwise? I suppose looking down from the north pole it does but if you look at it from the south pole it would be clockwise?
     
  2. jcsd
  3. May 3, 2012 #2
    the sun would rise in the west and set in the east

    all Coriolis effects would be reversed

    nothing too interesting
     
  4. May 3, 2012 #3

    Drakkith

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    I want to say that the Moon would begin to lose orbital angular momentum due to tidal effects and it's distance from Earth would slowly diminish over a few billion years. And yes, looking at the Earth from the south pole it would be spinning clockwise.
     
  5. May 3, 2012 #4
    If the Earth spun different, why would that effect the moon? The gravity from earth would still be the same. Also that means that every single planet spins counter clockwise and clockwise correct?
     
  6. May 3, 2012 #5

    Drakkith

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    The rotation of the earth causes the tidal bulges to move ahead of the moon and to pull it forwards just a little bit. This results in a gradual climb away from the earth. If the earth spun backwards the bulges would pull the moon from the other side, against its orbital motion. This is one reason why most moons orbit in a direction that is with their planets rotation, the opposite direction is very unstable.
     
  7. May 3, 2012 #6

    Janus

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    It's a tidal force effect. Right now the interaction between Earth and Moon causes a transfer of angular momentum that slows the Earth's rotation while moving the Moon further away.

    However, if the Earth rotated in the opposite direction than the Moon orbited this effect would have the opposite effect, causing the Moon to draw closer to the Earth.

    On another note, if the Earth rotated in the opposite direction, days would be ~18 minutes shorter, resulting in about 5 more days to a year, requiring a new calendar and new clocks.
     
  8. May 4, 2012 #7

    haruspex

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    I thought it would be exactly 2 more days, each day being about 8 minutes shorter.
     
  9. May 4, 2012 #8
    Kind of off subject but how did Galileo record Jupiter's moons in consecutive days for about 5 days and each drawing one of the moons orbited to the other side of the planet?
     
  10. May 4, 2012 #9

    Janus

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    Oops. Right.
     
  11. May 4, 2012 #10

    sophiecentaur

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    Interpolation?
     
  12. May 4, 2012 #11
    Whether you call the current rotation clockwise or counterclockwise is arbitrary and depends on whether you are looking down from the North pole or up from the South pole. If you changed the rotation suddenly, there would be massive transient effects, but if you somehow ignored the transient effects, I don't think there'd be too much long term effect. I'm guessing the transient effects (hurricanes like the world has never seen) would kill us all.
     
  13. May 4, 2012 #12

    sophiecentaur

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    Problem with these scenarios is setting up the conditions under which they could actually occur (even just in thought). Most of the large objects in the Solar system rotate in the same sense, because of the way things started off and settled down. The Moon is tidally locked to the Earth and the Earth is heading that way with the Moon too (enormous time scale). If the Earth's rotation were to be reversed then the moon would be dragged closer and closer until it crashed. But any event that could cause the original change would need to be immense and extremely well orchestrated to avoid nudging the Moon in some way. Would you use enormous rockets? In which case the ejecta would probably affect the Moon too. It might be easier to set the Moon off in a reverse orbit and discuss what happens then. (Crash, again)

    God knows what the tides would be like near the end.
     
  14. May 4, 2012 #13
    Angular momentum has to be conserved, it will not change direction. So the only possibility is that the Earth's body orientation changes without changing the angular momentum vector. As long as the Earth is spinning about either its major (maximum moment of inertia) principal axis or its minor (minimum moment of inertia) principal axis, the Earth is stable. But if for some reason, the Earth body principal moments of inertia shifted (e.g., by major earthquake) such that the Earth were spinning about its intermediate principal moment of inertia, then the Earth's north and south poles could flip without affecting the angular momentum vector. In short, "the polhode will continue rolling on the herpolhode in the invariable plane without slipping". A good youtube demonstration of pole flipping was recently carried out on the International Space Station. See
     
    Last edited by a moderator: Sep 25, 2014
  15. May 4, 2012 #14
    What equation would one use to calculate the time it would take for the Moon to crash into Earth, if the Earth reversed its spin.
     
  16. May 4, 2012 #15
    The effect would be negligible, as long as the angular momentum vector of the Earth is unchanged.
     
  17. May 4, 2012 #16
    Someone earlier said the tides of the ocean would change the Moons orbit.
     
  18. May 4, 2012 #17
    Thanks, that is just too cool. Plus guys like newton could see that in minds eye, without the ISS or YouTube. We are lucky today...
     
    Last edited by a moderator: Sep 25, 2014
  19. May 4, 2012 #18
    Maybe i'm lost but what is the significance of the rotating book?
     
  20. May 4, 2012 #19
    If the Earth's angular momentum is unchanged, and the Earth's body axis flipped say over in a year (365 revolutions), an observer on Earth would see the east→west direction of the tides change by ~3 degrees per day to west→east. An observer in space would say that the Earth's tides did not change direction, but would say that the north and south poles flipped.

    By the way, the vector sum of the Earth's and Moon's angular momentum is conserved. When the Earth's rotation slows due to tidal forces, down, the Moon's angular momentum increases due to tidal forces, and moves to a higher orbit.

    Read ".........First there is a real retardation of the Moon's angular rate of orbital motion, due to tidal exchange of angular momentum between the Earth and Moon. This increases the Moon's angular momentum around the Earth (and moves the Moon to a higher orbit with a slower period). Secondly there is an apparent increase in the Moon's angular rate of orbital motion (when measured in terms of mean solar time). This arises from the Earth's loss of angular momentum and the consequent increase in length of day.[8]" in http://en.wikipedia.org/wiki/Tidal_acceleration
     
  21. May 4, 2012 #20
    Watch very carefully when the book is rotating about its intermediate principal moment of inertia axis. Note that the book binding is flipping from the left side to the right side, and back.
     
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