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Is it true that the earth's rotation is slowing down?

  1. Dec 23, 2011 #1
    If it is true, could anybody tell me how it is happening?
  2. jcsd
  3. Dec 23, 2011 #2


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    IIRC it's down to the Moon. The Moon slows down the Earth's spin and at the same time this boosts the Moon into a higher orbit.
  4. Dec 23, 2011 #3
    But using the same argument, isn't the Earth also slowing down the Moon's spin and thus pulling it in to a closer orbit?
  5. Dec 23, 2011 #4
    maybe they are trying to reach a state of equilibrium over time.
    my thoughts are that it is not going to happen forever, am I right??
  6. Dec 23, 2011 #5


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    Since the Moon is tidally locked now, that means we already slowed it's rotation down almost as far as it can go. As the Moon's orbital period gets longer so does it's day. Also, since the rotation of the Earth is in the direction of the Moons orbit it pushes the tide nearest to the moon forward, meaning that there is now a slight amount of mass ahead of the Moon, applying torque to it. This would speed up the Moons orbit, but that energy is used to extend it further out of the Earth's gravitational pull a little bit. So the result is the Moon gets further away from us and our rotation slows.
  7. Dec 23, 2011 #6
  8. Dec 24, 2011 #7

    We can compare the situation between earth and our moon to a merry go round and a rider on a horse circling it in the same direction on a track.

    Let's say that the merry go round is earth and the horse and rider are the moon.

    The rider has a lasso = gravity

    If he lassoes one of the merry go round's horses he will gain speed.
    Conversely the merry go round will experience drag and will lose velocity.

    Another way that earth rotation is slowed is via the friction of currents on the ocean floor which have a braking effect..
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