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Gravity - particle

  1. Nov 25, 2008 #1
    Is the force of gravity transmitted by a particle or is gravity due to the shape of space (of some sort).

    If gravity is due to the shape of space, why isn't this similar to the aether concept?
  2. jcsd
  3. Nov 26, 2008 #2
    Quantum theory indicates that gravity should be quantized, which would mean having an associated particle. This does not, as far as I know, eliminate spacetime curvature.

    This is completely different from aether theory. The aether is a postulated substance acting as a universal frame of reference against which everything could be measured. Modern physics has demonstrated that no such frame of reference exists.
  4. Nov 26, 2008 #3
    Quantum theory indicates that gravity should be quantized, which would mean having an associated particle. This does not, as far as I know, eliminate spacetime curvature.

    I don't understand why the force of gravity would be transmitted by a particle if gravity is thought of as a curvature. Do the particles curve spacetime?
  5. Nov 26, 2008 #4
    Something I personally have never understood about gravitons. Will they themselves have energy and so cause curvature? I'm not qute sure about how massless particles affect spacetime, my understanding of GR is crude at best (though improving slowly =]).
  6. Nov 26, 2008 #5
    Spacetime curvature might be graviton density at that point in space. (speculation)
  7. Nov 26, 2008 #6
    If spacetime is a matrix of gravitons of differring density, it sort of sounds like an aether like substance.
  8. Nov 26, 2008 #7
    differing density?
  9. Nov 26, 2008 #8
    I might have misunderstood the other poster (speculating that the density of gravitons is what curves spacetime).
  10. Nov 26, 2008 #9


    Staff: Mentor

    Because you cannot assign a velocity to curved spacetime.
  11. Nov 28, 2008 #10
    Curvature being graviton density (one assumes that means number of gravitons per unit spacetime i guess?) then would this mean that something producing a gravitational field would have to emit gravitons at a constant rate? so as to keep the curvature at a point the same, and thus the force the same?

    Gravity confuses me, i need to go read a book.
  12. Nov 28, 2008 #11
    Different theories "see" (interpret) gravity differently:

    Netwon: an instantaneous force , three dimensions of space, space and time is fixed

    Einstein: curvature of space time, not a force, wave field like theory,continuous smooth, cosmic sizes, four dimensions of spacetime with variable space and time

    Quantum theory: gravitons are the carrier of gravity, discrete picture, atomic realm

    Trying to precisely compare all these is difficult: The first two are quite complementary and Einsteins picture simplifies to Newtons in many cases; Nobody knows how to "unify" the last two..it's been one of the major objectives since the 1920's. Einstein shows that gravity occurs due to mass, energy and pressure.

    String theory has a slightly different view from any of the above: It views all particles, gravitons included, as vibrating bits of two dimensional energy...different vibrational patterns cause different particles in 11 dimensional spacetime.

    Gravity is also related to the other three forces (strong,weak, electromagnetic) but nobody knows exactly how. And Maybe Higgs bosons (field) are also related to gravity since they theoretically cause mass and mass in turn causes gravity.

    In some vague sense you might consider curvature of space and aether "similar" in that both are "something". But curvature of spacetime is far more fundamental and subtle than "aether". Aether was postulated to carry light; it had nothing to do with any other force, such as gravity. gravitational curvature is unnecessary for the other forces; aether has been pretty well proven to be no existent.

    "We know a lot, we understand little."
    Last edited: Nov 28, 2008
  13. Nov 28, 2008 #12
    quantum theory sees space as consisting of a vast number of quantum oscillators. these can be thought of as tiny masses connected by springs. its easy to imagine how a mass could distort such a fabric. its not so easy to see how one gets an inverse square law out of that distortion.
  14. Dec 1, 2008 #13
    "We know a lot, we understand little."[/QUOTE]

    Thanks, that gives me the sense of it.
  15. Dec 1, 2008 #14
    As massless particles, gravitons must move at the speed of light.
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