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Black hole and graviton's ?

  1. Mar 15, 2010 #1
    If light can't escape a black hole , then can a graviton escape i am assuming it can this is why it gravitates , but I know we havn't observed them yet . But I am curious why can a graviton with no mass but I assume it has energy, escape a black hole but a photon cannot.
    or maybe for some weird reason a graviton can't escape a black hole.
  2. jcsd
  3. Mar 15, 2010 #2


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    Hi cragar! :smile:

    When two electrons repel each other electromagnetically, they don't actually exchange photons.

    Similarly, when two bodies attract each other gravitationally, they don't actually exchange gravitons.

    The photons or gravitons are only virtual particles , which are mathematical fictions designed to help in calculations (in perturbation theory in quantum field theory) of the electromagnetic or gravitational field.

    In other words, no graviton leaves the black hole to attract something else, the attraction is done by the field, and the field is calculated mathematically with the help of non-existent "virtual gravitons". :wink:
  4. Mar 15, 2010 #3
    i see , thanks for the answer .
  5. Mar 16, 2010 #4
    so, we really have no idea what happens when two electrons interact, and we have no idea how a field communicates with particles...
  6. Apr 7, 2010 #5
    Here is an interesting quote

    The notion of virtual particles mediating static forces comes from perturbation theory, and if there is one thing we know about quantum gravity, it's that the usual way of doing perturbation theory doesn't work.​

    see http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html

    In other words, all we know about gravity is that it is not like electromagnetism.
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