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The forces of gravity theory

  1. Jul 18, 2012 #1
    Can anyone explain to a layman (Me) the following paradox?

    Einstein's general theory says that gravity is not a force or a field but a distortion of time and space. Therefore the pull between the earth and the moon is an interaction of this distortion on time and space.
    My question is what 'force or field' causes this distortion. In other words if both the earth and the moon are not producing any fields or forces then how does time (my clock) and space (my ruler) 'know' they are even there in order that they change compared to time and space not near a massive object?

    If the answer is not understandable without immersing ones self in heavy mathematics then I apologize for the question.

    Thank You

  2. jcsd
  3. Jul 18, 2012 #2


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    Mass causes the distortion in spacetime, spacetime tells mass how to move
  4. Jul 18, 2012 #3


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    There is no "field" in GR. The "field" is the background space-time itself.

    This is one reason GR is so difficult to quantize. There is no "field on top of a background", but only the background.
  5. Jul 18, 2012 #4
    What force does 'Mass' use to cause this distortion?
  6. Jul 18, 2012 #5
    Actually, this isn't true for GR. Energy-momentum determines the strength of gravity, not mass. Mass makes, by far, the largest contribution to the energy, which is why Newton's law of gravity was such a good approximation.

    Matter curves space-time, that's just the way it is. Some particles have electric charge. Some have color charge. Similarly, curving space-time is just something matter does.
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