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A graviton is a spin 2 boson, thus is traveling at the speed of light? If so,how can it escape a black hole?

Stephen Hawkings postulated that black holes can lose energy by the uncertainty principle allowing energy to leak away via a process similar to quantum tunneling. Can this explain how black holes will allow for gravitons to escape and thus create a gravitational field? If so, how do we reconcile the graviton to the so called bending of space-time?


  1. Who says the graviton goes at the speed of light? Nobody fully understands any of this, and it may very well be that gravitons, if they even exist, go faster than light, which is why nobody can find any of them.
    What happens to the space-time gravity well if the gravitational mass winks out of existence? Does this disappearance come as gravity waves, or does space time return to “normal” much more slowly. What is the speed of this, and what is the amplitude of any propagating waves….interesting things to try and figure out.

  2. Good question, but a graviton is an hypothetical particle. People think that gravitons can ignore the usual laws that govern mass and energy, possibly by jumping into another dimension.
    We are hoping that the large hadron collider will shed some light on this.

  3. Gravitons are the postulated exchange particles for gravitational force in a yet to be formulated successful theory of quantum gravity. As such, gravitons may be what discretized portions of space-time turn out to be. Right now however, these are hypothetical constructs that haven’t yielded a working theory.
    You point out one of the problems with a quantum description of gravity namely the existing of a particle for the exchange of force. Gravity is not a force like the strong force – it is really the curvature of space-time. So developing a theory that uses exchange particle to describe the curving of space time leads to all sorts of issues – you have hit on just one of them.
    Hawking was referring to the tunneling of matter from the black hole to the outside universe. I don’t think he woried about gravitons.

  4. Gravitons as a virtual particle that communicates the gravitational force are themselves NOT affected by the force they are communicating. Hence, they will and do escape the blackhole. Similarly, if a blackhole has a net charge, this information would also be communicated via virtual photons that will escape the blackhole.
    Only real particles can not escape the blackhole.

  5. If gravitons exist, and they behave as theorised, then gravitational attraction is caused by the exchange of virtual gravitons. Any two massive bodies will exert a gravitational force on one another. It is incorrect to think of these virtual particles as emanating from inside the black hole: they are the vector bosons corresponding to the gravitational potential field between the objects, just as virtual photons mediate the electromagnetic force.
    Real gravitons on the other hand are postulated to derive from massive objects in motion about one another. If two very massive objects are in orbit about one another, it is hypothesised that they should be radiating gravitational energy away in the form of gravitons (this is true for any orbiting objects but in most cases the effect is negligible). However in the case of the two massive bodies it is believed that this radiation of gravitational energy will cause the two bodies to spiral in towards one another until they collide with catastrophic consequences (a plausible mechanism for the most energetic phenomenon in the universe, a gamma ray burst, is two colliding neutron stars or black holes).


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