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What kind of force would be needed to push the Moon into the Earth?

  1. Jun 22, 2011 #1
    I'm not very fluent in how astral bodies are affected be gravity yet, or else I'd punch some numbers myself.

    But, what would be needed to knock the moon out of its current orbit and start it on an eventual collision course with the Earth? And what could (theoretically) cause this force?
  2. jcsd
  3. Jun 22, 2011 #2


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    Well it's not a force that you're concerned with. It depends how long you apply the force, in what direction you apply the force and how big the force is.
  4. Jun 22, 2011 #3

    I like Serena

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    I'm wondering if a number of coincidental orbital resonances of venus, mars and jupiter with the moon could cause some harm.
    As yet I can't find evidence on the internet whether someone has done the numbers....
  5. Jun 24, 2011 #4

    M=mass of moon.
    A=change in velocity per second.

    Thus, to push the moon into the earth, 1 Newton of force applied over nearly infinite time would yield nearly infinite acceleration.

    The right question is how much energy would be required. Express this in Newton-meters per second.

    V(i) = Start with orbital velocity of the moon
    V(f) = 0 (stop the moon, it will fall gravitationally into the Earth).

    ... etc.
  6. Jun 24, 2011 #5


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    I doubt it. At least on the time scale of several billion years. After all, the moon has been around almost as long as the earth has and there hasn't been a collision yet! And in fact, the moon has been getting further away from the earth as time passes.
  7. Jun 24, 2011 #6


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    Note that the Moon could cause substantial harm without colliding with the Earth. If it were knocked into a different orbit that got much closer to Earth, we'd experience much higher tides which could cause devastating flooding and big climate changes.
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