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Questions about gravity

  1. Oct 30, 2003 #1
    I'm apologize if this has already been adressed in other posts, but what is gravity. I know that it is the attractive force between masses, but what causes this attraction?
     
  2. jcsd
  3. Oct 31, 2003 #2

    Integral

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    Good question. Unfortunatly Physics cannot provide an answer. We can quantify and decribe but we cannot explain why.
     
  4. Oct 31, 2003 #3

    pmb

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    The short answer is - Nobody knows.

    Pete
     
  5. Oct 31, 2003 #4
    Yep - nobody knows.
    In an effort to make this thread worth while - I'll toss something up.

    I've been bouncing the idea around that a gravitational field works on a strictly mechanical basis. That an encounter with any gravitational field is the equivalent to an encounter with the particles themselves. That the field is the particle and the particle is the field? Yipes!!! Send this guy some prozak!!

    In other words - A particle is a collection of localized fields .. where half of a field is localized (particle), while it's other half progresses outward as a gravitational field. This happens because the fields are in orbit as opposed to say a free ranging photon field that is not. A gravitational field would eminate outward in a spiral fashion (due to it's orbit). Within this spiraled gravitational field are waves. These waves are the equivalent of gears. When gravitational fields momentarily interact - the gears mesh...thereby pushing or pulling accordingly.
     
  6. Oct 31, 2003 #5

    chroot

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    Arc_central,

    Don't post your crackpot nonsense in this forum, ESPECIALLY not in response to a bona fide question.

    - Warren
     
  7. Oct 31, 2003 #6

    pmb

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    chroot - Friendly request - Please don't respond in this manner. He's clearly stating that this is something that his something he's been 'bouncing around" and is tossing out there for lack of a better answer. There's no reason to chastize someone for thinking out loud and telling someone his idea.

    Pete
     
  8. Oct 31, 2003 #7

    russ_watters

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    Well, there is always the warping of space-time like a bowling ball on a trampoline (except in 3d). But then, is that just a model that works or a real representattion of a physical reality? And that still of course doesn't explain HOW mass warps space.
     
  9. Oct 31, 2003 #8

    turin

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    I don't like this model. You have to assume gravity exists in the model in order for other objects to be motivated to roll down hill (or even for the bowling ball to warp the trampoline in the first place). If the trampoline is in deep space, there would be no sensible model, and the reason is that the model already assumes gravity exists to show why it exists. You could say that the trampoline is accelerating upwards, and anything on its surface will warp it. This is pretty close to the model of GR, but, it still has the problem of "why is the trampoline accelerating?"
     
  10. Oct 31, 2003 #9
    An object rolling on a trampoline (accelerating or not) is not a direct physical model of gravitation in curved spacetime. If you model space as a curved surface like a trampoline, objects in free fall don't generally roll "downhill".

    Anyway, in general relativity, objects in free fall move in the absence of force, so they obey Newton's law: an object in motion travels in a straight line when not acted upon by an outside force. It's just that a "straight line" in curved spacetime isn't a Euclidean line. None of this requires the notion of some force that makes things roll down hills or anything.
     
  11. Oct 31, 2003 #10

    pmb

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    The mathematics of general relativity is identical to that of curved spaces. So visualing tidal forces as a ball on a rubber sheet is often used.

    However not all gravitational fields have curvature. For example: There is zero spacetime curvature associated with a uniform gravitational field.


    Pete
     
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