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Floating Objects Affected by the Moon

  1. May 30, 2013 #1
    This seems like a pretty simple question, but I haven't been able to find an answer yet. It has to do with gravity, so even though it's not really about special relativity, this seems like the best place to post it.
    My question is; if an object were free-floating in perfectly still water, without currents, would it move in a circular patter due to the Moon's gravity? If not; under what conditions, if any, could the Moon's gravity move a solid object?
    (p.s. I already know that the Moon moves the Earth's tectonic plates, I was wondering about smaller objects.)
    Last edited: May 30, 2013
  2. jcsd
  3. May 31, 2013 #2

    Simon Bridge

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    Welcome to PF;

    Are you thinking of tides here?
    That would be classical physics.

    The Moon's gravity affects the motion of everything just as the Earth and the Sun do... or anything with mass.
    The details depend on the situation... under gravity the water, your example, would not be perfectly still ... as the moon passes you get a tide - everything gets tides.
  4. May 31, 2013 #3


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    The water would show some tides, so the object could be dragged along with the water.
    It does not have to be a circle - tidal patterns are often complicated.

    If you manage to let an object float over a perfectly balanced surface (magnetic levitation?), it could move in a bigger circle - at least in theory.
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