What is inside a black hole?

Assorted nitpicks:

Quoth Stranger on a Train:

A giant fundamental particle. Composite particles have hair.

Actually, if the hole is maximally rotating (believed to be a good approximation for almost all astrophysical black holes), then the ring is of order a kilometer in diameter, and there are geodesics which pass cleanly through it. You’re still going to hit it if you fall in, though: Any nonzero test mass will, as it’s falling, perturb the hole in such a way as to close up the ring just in time for the test mass to hit it.

Quoth Ring:

I suspect that you didn’t have a very good teacher. Taught well, the index notation makes tensor problems far, far easier. I always cringe when I see engineers (who haven’t learned the Einstein summation convention) doing tensor problems the hard way.

On white holes, meanwhile, there’s nothing in the laws of physics that says that they can’t exist, but they can’t form. So for a white hole to exist, it would have to have existed since the beginning of the Universe. Since our Universe apparently started without any white holes, without white holes it shall remain.

Could you expand on that without making most of our heads explode?

Or you could say that one white hole has existed since the beginning of the universe: the universe.

Chronos wrote:

I have an electrical engineering degree and an MBA. Over the years I bought about a zillion dollars worth of physics and math texts and taught myself.

So I can guarantee you that I didn’t have a very good teacher. In fact he sucked canal water. If it weren’t for sci.physics and the internet he and I would still be sucking it.