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If the moon suddenly vanished, what would people on earth experience?

  1. Apr 16, 2008 #1
    Would there be earthquakes and tsunamis, or would nothing odd happen at all apart from smaller tides?
    Last edited: Apr 16, 2008
  2. jcsd
  3. Apr 16, 2008 #2
    The earth would wobble like crazy. The seasons would be all out of whack. Life wouldnt survive for long.

    No tides either.
  4. Apr 16, 2008 #3
    I agree with your last point, no tides at all.

    but no life ? surely the moonlight brings the ladies into a romantic mood and makes it easier to seduce them (not that I would claim too much expertise here...), so:

    no moonlight -> no seduction -> no sex -> end of mankind

    but surely the animal kingdom as a whole should not be affected ?

    seriously, as for the wobble: OK, moon and earth are kind of synchronized, but I always thought this would mostly affect the moon (rotation about its own axis in sync with rotation around earth, therefore always pointing same side to us), but would earth really be affected that much ? no stable rotation around our own axis any longer ?
    Last edited: Apr 16, 2008
  5. Apr 16, 2008 #4
    We would only know about it a few seconds after it happened! :smile:
  6. Apr 16, 2008 #5


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    Why would the earth wobble?
  7. Apr 16, 2008 #6


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    There would still be tides, I think, only due to the sun's gravity, therefore much weaker and slower, than the lunar tides we experience. I don't remember what I read, but I seem to recall something detailing how our moon is actually extremely important to the development of life on Earth.
  8. Apr 16, 2008 #7


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    I've never heard of that, but it might make sense if low tides made it easier for our ancestors to transition from the ocean to land.
  9. Apr 16, 2008 #8
    I'm thinking that if the earth has a force pulling on it constantly and then that force is suddenly removed, you'd get vibration as the earth relaxed into a non-stretched state, like a rubber band vibrates after it's shot. Maybe that means huge earthquakes and tsunamis. I don't think the earth would wobble, just vibrate.

    The tides allowed sea animals living near the shore to be exposed to air for periods of time as they were left in the sand as the tide went out. That would acclimatize them over time to land life.
    Last edited: Apr 16, 2008
  10. Apr 16, 2008 #9
    So it wouldnt wobble? more than it already does, anyway.
  11. Apr 16, 2008 #10


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    Erm, I see no reason why the earth should suddenly feel a "spring force". Simply, the earth has two forces on it right now: due to the sun and moon. If the moon disappears we will simply accelerate due solely to the sun. There is no "resting position" for the earth that the moon took us out of...
  12. Apr 16, 2008 #11
    The gravitational force the moon exerts on the sun is approximately half that of the sun. The axis is tilted and so they both torque the Earth causing it to precess. With the moon gone there is no partial cancellation of the torques and so the net torque will be greater, and thus the precession will be greater.

    That's just speculation from me, I don't really know what I'm talking about.
  13. Apr 16, 2008 #12
    There would be no Earthquakes! The moon is 80 times lighter than the Earth and it's distance from the Earth is about 50 times Earth's radious. This gives only 1/200000 g of acceleration. In addition the Earth is deformed only by gradient of that gravity, since it is in free fall motion against the Moon: each atom on Earth is atracted with almost the same force as needed to maintain radial acceleration. If you remove both force and acceleration, then nothing happens (except the very small effect, because the near end of the Earth used to experience more attraction than the far end).
  14. Apr 18, 2008 #13
    we would have less light pollution at night for observing with telescopes. We would have no more Lunar or Solar Eclipses.
  15. Apr 18, 2008 #14
    We will no longer have 24 hour per day. It will be much faster. I could not recall the exact number. Anyone can help?
  16. Apr 18, 2008 #15
    If the Moon would vanish, we would still have 24 hours per day, since Earth's rotation frequency is determined by it's angular momentum. As far as the length of the day is concerned, Moon's dissapearance would be an advantage, since the torque of Moons gravity would cease and the rotation would not slow down anymore.
    But if there was no Moon in the history of the Earth, then the Earth would still rotate very fast and the life on Earth would probably be very different.
  17. Apr 18, 2008 #16
    If the moon vanished, NASA would get blamed, and it would turn out that there was never any moon at all, just a government conspiracy so NASA could fake the moon landings.
  18. Apr 18, 2008 #17
    ooops.... seems that my statement "no tides at all" was quite wrong. after some calculation I think that they would not even decrease that much:

    if we have a mass M, then a test mass in the distance r would experience an acceleration of

    a(r) = -GM / r^2

    to get the gradient, which is the cause of the tidal forces, we have to differentiate this and get

    a'(r) = 2GM / r^3

    now we are not interested in absolute values, but in the relative strength of the tidal forces from moon and sun. so 2G cancels and we get as the relation

    (Ms / Mm) * (rm / rs) ^ 3

    where Ms and Mm are the masses of sun and moon and rm and rs are the the distances earth-moon and earth-sun.

    putting in the numbers I get the result that the tidal forces of the moon are only stronger than those of the sun by a factor of 2.18

    so the tides would decrease significantly, but they would not at all vanish !

    these are the numbers I used:
    Ms = 1.9891 E 30 kg
    Mm = 7.3477 E 22 kg
    rs = 1.496 E 11 m
    rm = 3.84399 E 8 m
    Last edited: Apr 18, 2008
  19. Apr 18, 2008 #18


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    LOL...a government conspiracy somehow passed along amongst all world governments that have ever existed anywhere throughout recorded history. I'm impressed! I wonder how they pulled off the mass hallucinations...
  20. Apr 18, 2008 #19
    So that bright ball I used to observe on the sky was actually a product of my brain implant?
  21. Dec 15, 2010 #20
    No doubt about that! Haha
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