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The Earth, Moon and Sun's gavity game.

  1. Mar 23, 2006 #1
    The Earth, Moon and Sun's "gravity" game.

    Hi all,

    I was thinking today that even though the moon is orbiting the Earth, because we are its nearest body mass, is it affected in any way by the Sun? In other words, to me it seems strange that just because the Moon is under the direct pull of the Earth, for lack of a better word, is it because the Earth is so close to the Moon that the Sun does not have that extra pull to make the Moon's orbit wobble? I mean if the Sun's "gravity" is so strong to hold Pluto in orbit, why would it not have an effect on bodies like the Moon, even though its in orbit about the Earth.

    It leads me to think that space is truly warped and the Earth and Moon together, are more of following an easy, warped space "path" than there are mystery gavitational waves hitting us from the Sun and holding or pulling at us. I would think that if there were these strong waves, they would have an impact on the orbits of smaller bodies, like the Moon, pulling or pushing always at it.

    Randy the student.
    Last edited: Mar 23, 2006
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  3. Mar 23, 2006 #2


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    If you track the path of the Moon as it goes around the Sun (of course it does! It goes around the Earth, yes? And the Earth goes around the Sun) you find that it is everywhere convex. That is to say the "going around the Earth" is just a small perturbation in the Moon's going around the Sun.

    From the point of view of Earth, the Moon has a highly variable orbital motion. Both its speed in orbit and the orbit's inclination and orientation change constantly. Newton was never able to master it, because he was fixated on central forces. He kept trying to find some trick that would reduce the force on the Moon to a single central value. But he couldn't, because the Moon's motion is caused by two different central forces. And every time the Moon moves it changes its relation to one or the other or both of them. The problem was only solved in the 20th century by G. W. Hill, at the U.S. Naval Observatory. He had to use infinite dimensional determinants to do it.
  4. Mar 23, 2006 #3


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    In actuality, the Sun's pull on the Moon is stronger than the Earth's.
    This does not mean that the Sun is pulling the Moon away from the Earth, since the Earth is also pulled on by the Sun. As a result, the Earth and Moon co-orbit the Sun.

    But you are right, the Sun does have an effect on the Moon's orbit around the Earth. This is because the Moon is sometimes a little closer or further from the Sun than the Earth. At these times, the Sun's pull on it is a little stronger or weaker. As a result, the Moon's orbit is "stretched" along the line joining the Earth and Sun. Since the Moon's orbit is not a perfect circle, it is sometimes stretched even more eliptical and sometimes more circular.
  5. Mar 23, 2006 #4
    I know that at a certain point in time the sun and moon are both pulling on the Earth in the same direction and during the cycle, both sides of the Earth get pulled in the opposite direction, causing Geo stress. We're lucky we have a moon the size we do, we wouldn't have tides to stir the water or seasons/ (Axis) without it. Also I believe I read that the moon used to be 15 times bigger(view) than it is now! What an awesome view that would be! Which would cause bigger waves I presume, which is why we have sand stone in land locked states?
    Last edited: Mar 23, 2006
  6. Mar 24, 2006 #5
    I hope I am posting to the right box here to reply.
    Thanks to you all for the fast replys also.

    From what you are all saying, it seems that everything is just the right amounts of this and thats, as to ensure what we see happening, works. There might of been years (billions) ago other maybe moons or masses floating around here that, because they just did not fit that "groove" just right, either blew up or shot out to deep space or burned up into the Sun or collided with one of the planets we have here now. Everything in our solar system we see now, works together to "exist" within the forces encountered.
  7. Mar 24, 2006 #6
    Check out the computer model of the "Big Slpash".


    There is a formula for Earth like planets, just H2O (latex)does not mean life, if that's what you're getting at.
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