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Question on Virtual Particles

  1. Jul 29, 2003 #1
    For the purposes of this question, assume there are gravitons and they are the carrier of the gravitational force. I could use one of the other forces and leave out gravitons, but it's easier for me to envision this question using a very low strength force.

    Q1) -- For gravity to deflect the path of a photon, does it take many-many interactions with gravitons to do the trick? I mean, the angle a photon is deflected is related to mass (other things the same) and I would think the more the gravitational field is to deflect the photon, the more gravitons it would have to interact with to get the job done .. no one graviton interaction could do the job.

    Q2) -- If that is true, (and this is really my question), I envision the Universe awash in virtual gravitons. So many more of them than virtual photons, and other virtual particles. I know someone could say "well, it depends on where you are in space .. it might not hold true with very little mass in this part of space". But that's not what I mean .. you might also have to assume all matter/energy/forces pretty evenly distributed thoughout the Universe. Wouldn't there then be upteen magnitudes more virtual gravitons around per volume than virtual photons?

    I'm going to use the answers as the basis of another question, later.
  2. jcsd
  3. Jul 29, 2003 #2


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    It's of course perfectly alright to view directional changes in the paths of photons moving in a curved spacetime as a result of successive interactions with gravitons. But in terms of single scattering events, it's the energy of interaction that's important: Large deflections result from the emission or absorption of a single high energy graviton.
  4. Jul 29, 2003 #3


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    I suppose that if we dealt with gravity as a radiative force, like EM, it would be rational to assume that gravitons would be more abundant than photons (throughout the cosmos as a whole). Photons are emited by energetic phenomina like stars and quasars and so forth, but gravitons (in some quantity) are emited by everything that has mass. The dark matter that appears to make up the vast majority of the mass of the universe "emits" large amounts of gravity, but no detectable amounts of EM.
  5. Jul 30, 2003 #4
    Hmmm, you brought up a good point. I guess until now, I've always considered/looked at it as if gravitons, or at least virtual gravitons, would have a sort of "fixed energy" and thus a fixed wavelength. That is, to transfer a higher value of energy it would take many gravitons interacting. Or that for a large mass to communicate its presense, there would essential be exact duplicate gravitons sent out from many discrete parts of that mass.

    Looking back at that, it is a stupid way for me too look at it .. LOL. But for the life of me, I can't come up with a vision of how virtual gravitons of different energy could be sent out.

    ("sent out" is not very good terminology here I know, but I can't think of better terminology to use)
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