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I have one last rant about this. Black holes may not exist in the sense that everyone thinks of them.
Relativity is very very hard to work with. Einstein's equations have only been solved in a couple of simple cases. The first of these solutions was in fact the simplest black hole. It was perfectly spherically symmetric, static, and in perfect vacuum exccept at its exact center. Generalizations were eventually found to rotating and electrically charged holes, but there were still stationary, isolated, and in vacuum almost everywhere.
These solutions are very interesting to play with, and are widely studied because its so hard to do anything else. Most of the things we say we "know" about black holes come from these solutions. But it has to be asked whether its reasonable to assume that just because these things could exist that they actually do. Assume that the universe didn't start with these things. Then we say a star collapses to form one. There's been a lot of work trying to show that this actually happens, but what I've seen of it is not entirely convincing.
It ignores cosmology for example. There are some tricks done whereby an infinite amount of time measured by one observer is finite to another. After "infinite time," however that may be defined, I think the external universe could have an influence. On top of that, Hawking radiation is supposed to be happening etc. The leap from collapsing star to black hole with singularity is a massive one.
If you've ever taken a physics course in high school or college, you've dealt with singularities. Except we call them "point charges," or "point masses" in Newtonian physics. Just because they solve the equations doesn't mean they exist. (Actually, a complete classical description does not allow point charges, but that's a whole other discussion. Nobody has been able to transfer the relevant arguments to GR anyway.)
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