A Question About the Surface of a Black Hole Singularity In Kip Thorne's book, Black Holes and Time Warps, he states that the mass of the core of a star shrinks until quantum gravity takes over.  And then discusses that at this distance, the singularity cannot be distinguished from quantum foam.  I am confused.  Is he stating that the singularity is covered in quantum foam or does the mass shrink so small it becomes part of the quantum foam.  If it is the latter, how can the quantum gravity, affect the macroscopic world?
Is he discussing the surface is smooth, except for the fluctuations required by quantum gravity?
Sorry - I am not a scientist or student...
 A: In Thorne's book, on page 477, it says "Because all conceivable curvatures and topologies are permitted in side the singularity, no matter how wild, one says that the singularity is made from a probabilistic foam.  John Wheeler, who first argued that this must be the nature of space when the laws of quantum gravity hold sway, has called it quantum foam."
So what you are thinking of as a foam is really only a probabilistic foam.  This is just a way of saying that every possible state in the singularity is only a probability. (Takes you back to the probabilistic nature of any particle which is a discussion far beyond this answer).
But remember Thorne's central point of the chapter, that time does not exist at the singularity.  Space and time have separated from each other.  Time stops at the event horizon, but space continues to dilate all the way down to the singularity. This quantum foam is Wheeler's way of describing the situation of an unknowable, but only probabilistic, nature of the singularity.
