Re: Gravitons and black holes

Hello, David -

Actually, gravity is best understood using general relativity, which is not a quantum theory (and so does not involve gravitons). There is at the moment no successful theory of quantum gravity (which is where you would get gravitons); it may or may not be possible to describe gravity as a quantum theory. In any case, the type of theory which gives rise to virtual particles such as photons is what's called a perturbative theory (where you use a series of approximations, the terms of which get smaller and smaller); this is exactly what doesn't work when trying to make a quantum theory of gravity. So even if there is eventually a consistent quantum theory of gravity, it may very well not have gravitons in it.

Further information can be found in the sci.relativity FAQ, at http://math.ucr.edu/home/baez/physics/relativity.htm - see especially the question under "Black Holes", "How does the gravity get out of the black hole?" and the reference in it to virtual particles. At the end of the virtual particle FAQ is a discussion of the question, "I hear physicists saying that the 'quantum of the gravitational force' is something called a graviton. Doesn't general relativity say that gravity isn't a force at all?". This will shed further light on your question.

There is a long, but nontechnical, introduction to quantum gravity at http://www.weburbia.demon.co.uk/pg/qugrav.htm ; finally, an extensive set of links to all sorts of information about both general and special relativity is at http://www.phy.syr.edu/research/relativity/rel-link.html .