How are gravitons supposed to work?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by geordief, Jul 6, 2019.

  1. geordief Valued Senior Member

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    I understand they are hypothetical objects theorized to mediate a gravitational force ,presumably between objects of mass.

    If they were to be compared to the photon in their em fields how might they work?

    Since em can be an attractive or a repulsive force would that allow one to hypothesize that gravity too might have a repulsive side to it also?

    How might that work?

    Or is it out of the question?

    Would supersymmetry require their to exist an "anti graviton"?

    Well I have no real understanding of supersymmetry ( or much else) so that might be balderdash ;-)
     
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  3. Janus58 Valued Senior Member

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    They are quanta of gravitational radiation(waves) just like photons of electromagnetic radiation(waves). As such, they are not directly responsible for the gravitational field, anymore than photons are directly responsible for the electromagnetic field. In QED, its the exchange of virtual photons that mediates the field. In a quantum theory of gravity, virtual gravitons would mediate the gravitational field. Now while the idea that QM applies to gravity is pretty much expected to be true, It has proven exceedingly difficult to actual formulate a quantum gravity theory.

    There would be no repulsive side to gravity due to the expected spin of the graviton, which is 2, as compared to the spin 1 photon. Quantum spin is a bit of an odd duck in many respects, For example, if you rotate a spin 1 particle 180 degrees, it is in a new quantum state, and you have to rotate it another 180 degrees to return it to the original state, However rotating a spin 2 particle 180 degrees returns it back to the original state. This difference in spin leads to the graviton only mediating an attractive force.

    There is no such thing as an "anti-graviton as, like the photon, the graviton would be its own anti-particle.
     
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  5. geordief Valued Senior Member

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    Thanks that is helpful

    From another forum I understand that these virtual objects are not "real" as we might be expected to imagine them but more like mathematical objects

    Would that be right?

    Does the exchange of virtual photons create the em field or just mediate it? (If there is a difference)
     
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  7. RainbowSingularity Valued Senior Member

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    when you collect a large amount of photons in one place does it turn into a collective single field ?
    its that timey-wimey thing i think
    the higgsboson of gravity
    if gravity is only ever a field then why is the cat sitting on the TV remote all the time

    theorhetically ...
    light doesnt create gravity/gravitons
    where as gravity eats light
    from my very poor understanding, the light would need another factor of exchange action to create a gravitational effect, be that a plasma or such like containing essential mass which by-err is the graviton already in a neatly packaged concept.

    musing...
    dark energy combined with photons ... may cause some type of entropic cascade to form a graviton in some state.
    what we do not yet see is dark energy interacting with photons directly.
    is dark energy free of gravitons ?
     
    Last edited: Jul 7, 2019
  8. Q-reeus Valued Senior Member

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    BS. Do some basic research before making false assertions. Here, I'll kick start:
    http://www.desy.de/user/projects/Physics/Relativity/SR/light_mass.html
    Unlike some lazy sods that infest this site, I'll save some time and direct your attention to the last main para.
    The rest of your musings are too crazy to bother commenting on.
     
  9. DaveC426913 Valued Senior Member

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    "Real" is kind of meaningless in physics. Our equations describe what happens; that's all it is meant to do.

    Our equations for quantized gravity describe what happens pretty well. Whether they're "real" is a question for the philosophers.


    Neither.

    The exchange of virtual photons is the EM field.

    In relativity, EM is a field (a field is continuous. It has a value for every point in space.)
    In QM, EM is an exchange of virtual photons. (photons are quantized, discrete)
    They both describe the same thing, using different models.
     
  10. Q-reeus Valued Senior Member

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    You surely know better than that. EM is the discipline that unites electricity and magnetism, not a field. An EM field otoh can be either static (in a particular frame), or dynamic - one example being EM radiation. The latter in a QED picture entails propagation of real not 'virtual' photons. While some speak of static fields as being 'virtual photon exchanges', you must be aware at PF of Arnold Neumaier's long running articles dealing with that pop-sci picture, e.g.:
    https://www.physicsforums.com/insights/misconceptions-virtual-particles/
     
  11. paddoboy Valued Senior Member

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    Gravitons are of course just hypothetical at this time.
     
  12. paddoboy Valued Senior Member

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    Actually light/photons do create a gravity field, by warping spacetime, ever so slightly. Entirely due to its momentum...but again, that tiny it isn't really worth worrying about.
    Of course the momentum of light'photons can be put to practical use, as in light sails.
     
  13. RainbowSingularity Valued Senior Member

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    i see your point
    i was pondering the Schrodinger perspective of the particle wave duality.
    if the light is a particle then it is not a field
    visa versa
    once it becomes(is observed) the field then it is the particle etc...

    is solar wind only photons ?
     
  14. Q-reeus Valued Senior Member

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    Wrong. Quit muddying the waters with your stabs at 'explanations' that add to confusion.
     
  15. paddoboy Valued Senior Member

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    I would ignore if I was you, the more emotional replies.
    The solar wind in actual fact are simply charged particles so no, not photons.
     
    RainbowSingularity likes this.
  16. paddoboy Valued Senior Member

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    No correct q-reeus. Please do some study and bring yourself up to scratch.
    https://www.google.com/search?q=doe...s warp space time&aqs=chrome..69i57j33.16127j
    "Photons can bend space-time and can create gravitational attraction force. However, the bending and the force are so little that they are overridden by quantum uncertainty. ... according to General Relativity everything that has momentum and energy causes warping of space time..so do photons.."

    Of course as it says, this is as per GR which you sadly ignore.
     
  17. Q-reeus Valued Senior Member

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    Brazen fool. Too vain to concede. As usual. And btw that excerpt you quoted is still missing something. But why bother elaborating to a parrot.
     
  18. paddoboy Valued Senior Member

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    Your insults don't phase me q-reeus and are simply painting yourself further into a childish corner. Again, Light/photons do warp spacetime ever so slightly due to its momentum, and of course as does energy in general....
     
  19. Q-reeus Valued Senior Member

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    Nothing outstanding, but this episode filed away for future reference.
     
  20. geordief Valued Senior Member

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    That surprises me. I was under the impression that theories for quantised gravity were very much at an exploratory stage and didn't really amount to much more than a wish list.
     
  21. DaveC426913 Valued Senior Member

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    This is silly, even for Q-reeus:
    :cuffs Q in the back of the head:
     
    Last edited: Jul 7, 2019
  22. DaveC426913 Valued Senior Member

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    I guess it's a matter of perspective. YMMV.

    I'd say we understand the theory, but no physical evidence forthcoming.
     
  23. sweetpea Valued Senior Member

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    Q-reeus, I found the following in the link you provided for Rainbow post #5.
    http://www.desy.de/user/projects/Physics/Relativity/SR/light_mass.html
    So why are you saying paddo is wrong?
     

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