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Qed and gravity

  1. Sep 2, 2004 #1
    There are two protons in the gravitational field of the Earth, one directly above the other.They experience the electric force through exchange of virtual photons.A virtual photon travelling vertically upwards from the lower proton towards the higher proton would be redshifted and so exert a smaller force on the higher proton than it would if there was no gravitational field present.
    A virtual photon travelling vertically downwards towards the lower proton would be blueshifted and exert a bigger force on the lower proton than it would if there was no gravitational field present.
    Has gravity given the higher proton a bigger effective charge (since the magnitude of a charge can be determined by the force it exerts on other charges)
    and the lower proton a smaller effective charge.The sum of the charges would still be the same so we could say that charge is conserved still.
  2. jcsd
  3. Sep 2, 2004 #2


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    Science Advisor

    No. The virtual photon by definition is the mediator of the electromagnetic force.

    Gravitons mediate the gravitional force.

    The correct question would be, how much is the net potential going to vary between the protons if you take gravity into account. And the answer is, not much, assuming they are fairly close together.

    Now, ok, ok.. You can draw a feynman diagram where there is vacuum graviton loops in the virtual photon line.. But again the contribution is so vanishingly small no one cares about it.
  4. Sep 3, 2004 #3
    The contribution may be small but if the effective electric charges change that is significant.And reversing the situation and putting the protons in an electric field
    (where gravitons would have their energy changed by interaction with photons)
    we could conclude that mass is created by placing a particle higher up in an
    electric field where the potential energy is greater.Note also that rotating the
    protons in the gravitational field through any angle will leave total electric charge conserved.
  5. Sep 5, 2004 #4
    Mass Cannot Be Created!!!!!!!!!!!!
  6. Sep 6, 2004 #5
    um... yeah, it can be. You'll understand when you're older, veryyoung :smile:
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