I understand that photons, even when traveling at the speed of light, cannot escape the event horizon of a black hole. Are gravitons and other virtual particles traveling at the speed of light also confined by event horizons?

If so, it seems that the gravitational field created by the black hole would result only from the mass of the black hole beyond the event horizon, where gravitons are capable of escaping. As a result, would there would be a disparity between the apparent mass of the black hole due to its gravitational field on other celestial bodies and the total amount of matter contained within the black hole?

Also, I was reading this question: Nature of gravity: gravitons, curvature of space-time or both?, which suggests that gravitons and curved space may be indistinguishable. However, if gravitons are bound by the event horizon it seems that a black hole would act differently based on whether gravity results from gravitons or curved space-time. The existence of bound gravitons would negate the gravitational field of mass within the event horizon, resulting in a significantly lower gravitational field outside of the black hole. Would this occur, or am I neglecting some effect of relativity upon the gravitational field?


Found this interesting read on this website:

In a classical point of view, this question is based on an incorrect picture of gravity. Gravity is just the manifestation of spacetime curvature, and a black hole is just a certain very steep puckering that captures anything that comes too closely. Ripples in the curvature travel along in small undulatory packs (radiation---see D.05), but these are an optional addition to the gravitation that is already around. In particular, black holes don't need to radiate to have the fields that they do. Once formed, they and their gravity just are.

In a quantum point of view, though, it's a good question. We don't yet have a good quantum theory of gravity, and it's risky to predict what such a theory will look like. But we do have a good theory of quantum electrodynamics, so let's ask the same question for a charged black hole: how can a such an object attract or repel other charged objects if photons can't escape from the event horizon?

The key point is that electromagnetic interactions (and gravity, if quantum gravity ends up looking like quantum electrodynamics) are mediated by the exchange of virtual particles. This allows a standard loophole: virtual particles can pretty much "do" whatever they like, including traveling faster than light, so long as they disappear before they violate the Heisenberg uncertainty principle.

The black hole event horizon is where normal matter (and forces) must exceed the speed of light in order to escape, and thus are trapped. The horizon is meaningless to a virtual particle with enough speed. In particular, a charged black hole is a source of virtual photons that can then do their usual virtual business with the rest of the universe. Once again, we don't know for sure that quantum gravity will have a description in terms of gravitons, but if it does, the same loophole will apply---gravitational attraction will be mediated by virtual gravitons, which are free to ignore a black hole event horizon.

  • $\begingroup$ Thanks for the article. If a force-carrying particle travels faster than the speed of light, won't that enable the transmission of information to exceed light speed? I was under the impression that force-carrying particles can only travel at light speed. Also, could event horizons exist for velocities greater than the speed of light, trapping virtual particles within their radius? $\endgroup$ – Alekxos Apr 7 '14 at 5:16
  • $\begingroup$ Virtual particles are called virtual because they violate a lot of laws. They can travel faster than light, they violate conservation of energy, but they can live only for a very short time. $\endgroup$ – PhotonBoom Apr 7 '14 at 7:13
  • $\begingroup$ Hi PhotonicBoom, this is pretty darn close to plagiarism. Next time please provide a basic summary in your own words and provide a link to the more detailed information. $\endgroup$ – Brandon Enright Apr 10 '14 at 20:56

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