Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is a graviton?

  1. Apr 3, 2009 #1
    is a graviton some kind of energy quantum? how does that reconcile with gravity as the geometry of curved spacetime? Is it energy with little quantum packets? or is it geometry? or is it somehow both? or is it neither and that's just the way we describe it's effects?
  2. jcsd
  3. Apr 3, 2009 #2


    User Avatar
    Science Advisor

    I'd say it's the quantum of geometric perturbations. As those contain energy in some way, the graviton does also.
  4. Apr 3, 2009 #3


    User Avatar
    Science Advisor

    The complete answers to a number of your questions remain unknown, particularly how quantisation is reconciled with space-time curvature. For the details we need to work out a decent qauntum gravity theory. There is no empirical proof of the existance of 'gravitons' and maybe they won't even be needed by whatever theory (hopefully!) one day answers your interesting questions.
  5. Apr 3, 2009 #4


    User Avatar
    Homework Helper
    Gold Member

    This is subject of a number of threads. On the one below I tried to get an answer at my level, for both the possibility of an understandable and not too mathematical explanation, and because of the striking confidence of physicists that they know at least one property of this particle which they are not expecting to see any time soon.

    In summary no one was very positive about the possibility of explanation satisfying my criteria, but it can surely be left open for any attempts. :smile:

  6. Apr 15, 2009 #5
    As noted, there is no absolute experimentally verified complete theory of gravity....general relativity and quantum field theory, quantum gravity,etc is about as good as it gets ....Wikipedia does a decent job of describing gravitons at


    and also references experimental efforts to detect gravitational waves
  7. Apr 16, 2009 #6
    sorry for a stupid question. Is it the quantum for Scalar perturbation or tensor perturbation?
    I guess they should be treated differently?thank you.
  8. Apr 16, 2009 #7


    User Avatar
    Science Advisor
    Gold Member

    The graviton is the only* particle predicted by the standard model which has not yet been detected. It is theorized to be a spin 2 particle that mediates the gravitational "force". As noted, QM and General relativity have not been reconciled with each other, and we don't have a good quantum theory of gravity.

    *Disclaimer: I'm not sure about this statement, I think it's true but I may be wrong.
  9. Apr 16, 2009 #8
    no,sir. standard model does not include graviton. Or else most people here should pack up and looking for new jobs. :-)
  10. Apr 16, 2009 #9


    User Avatar
    Science Advisor

    Tensor, like gravitational waves. Spin 2.
  11. Apr 16, 2009 #10
    thank you!
    But why scalar mode perturbation quantum do not have a name ? They do exist in the calculation of primodial perturbations.for example, quanta of mukhanov variable.
    Can we call it gravikachu ? pikachu pikachu 1228036664928.jpg
  12. Apr 17, 2009 #11


    User Avatar
    Science Advisor
    Gold Member

    'Particalizing' forces of nature enjoyed great success in the early days of QM, and led to string theory. Neither proposition has accomplished much more than obfuscation. Useful predictions do not necessarily validate the model. See Ptolemy.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook