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...wait.
So something like Gauss's law is only a law if it doesn't always apply?
So what do you call something that always applies without exception?

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It depends on the expansion scenario. A black hole in a de Sitter type universe (Λ>0) would be stable in that sense. The geometry is that of two distinct horizons--the black hole's event horizon and the cosmological horizon of the de Sitter space. There is a radius at which the expansive effect of Λ>0 exactly balances the gravitational attraction of the black hole. Although this trajectory is unstable, the fact that it is there means the black hole itself is stable. (A less hand-wavy proof of this is possible, but not really illuminating.)

A positive cosmological constant Λ could also be modelled as matter with energy density ρ and pressure p<0, with w = p/ρ = -1. This is insufficient for a "big rip" scenario, which requires w < -1. In that case, the acceleration will destroy black holes as well as the cosmological horizon shrinks to a point.


After crossing the event horizon, the singularity is inevitable. At that point, classically the infalling object stops existing--its worldline simply ends. Semi-classically, well, things are a lot less clear. That is the so-called black hole information paradox.


A sort of "new universe seeding" was actually one of proposed solution to the above paradox. I would say it is in some sense possible, but I would not call it plausible.

The large-scale structure of black holes should be describable by standard GTR just fine. It's only the fine structure, particularly near the singularity, that would be in doubt. As an aside, methinks you should review anatomy. Don't confuse GUTs with TOEs.

Hah. Last sunday, I was at church, which I attend only because I have a friend that calls me up and heckles me into attending. During the sermon, I did a proof of the fact that if A,B are real symmetric matrices, then AB-BA has only imaginary eigenvalues in my head. Ironically, the sermon was about not listening to God.


In GTR, black holes can be of arbitrary size, although quantum effects will be very significant for small sizes--it is likely that black holes cannot be smaller than a Planck mass. For a Schwarzschild black hole, light can theoretically orbit at 3/2 Schwarzschild radii, but that orbit is unstable--any pertubation will destroy it. I've covered the reasons for this here, although it is unlikely that anyone not already familiar with at least calculus will understand it. Since you are a high school freshman,


It defines black hole size in the first place: Schwarzschild radius r = 2GM/c². In that sense, I guess you can think of it as a scaling parameter.


It gets crushed. It is unclear what happens at the singularity, but according to classic GTR alone (which is not good for physics on this scale), anything encountering a singularity simply stops existing--it is no longer anywhere in spacetime.


A black hole already has the smallest possible volume for a given mass, if the size of a black hole is defined by its event horizon.


There is no reason to seriously doubt the existence of event horizons, since they are an ordinary prediction of GTR, which is an extremely well-established theory. If GTR fails, it would near the singularity. Most physicists expect that to be the case.


Could you clarify this question? I'm not certain what you're asking. Nonrotating black holes (Schwarzschild, Reissner-Nordström) are perfect spheres, in the sense that in space, their event horizons are spherical. Or are you asking about the singularity? Rotating black holes have a circular "ring" singularity rather than a point-like one found in nonrotating black holes.