by lordfrito | 2025-05-28 19:22:37+00:00
I very much appreciate your response... you clearly work in this field, and as I said I'm a total layman. So my musings could be utter nonsense.

That said... (bear with me)

> As long as whatever falls in also stays in, the approach is good. But what stops black holes from completely evaporating? In that case, what the hell is supposed to come out of the singularity / deep region / puncture region / excised region?

This is the rub isn't it?

First off, there's a lot of math, and the implications of said math (and GR model), which I'm absolutely not qualified to talk about (and you are). GR makes great (and testable) predictions on the outside of the horizon -- so we have immense confidence in the model, at least as far as we can observe and test.

Singularities in GR present all sorts of problems and paradoxes to us outside of the event horizon (here in the "testable" part of the universe).

I accept that that if we jumped into and found we could probe the interior behind the event horizon of, say, a sufficiently supermassive black hole where tidal forces are small enough we can continue to measure for a little while, then many of the things GR predicts should/would continue to be true. However that's a load bearing if, because it's untestable to an outside whether or not the observer jumping in actually made it inside... GR says that from the jumper's perspective and in their proper time they will cross over, but GR also breaks down in there. We have many reasons to believe the GR model is correct on the outside, but what confidence do we have that a "broken down" GR can be trusted to make predictions on the inside? Maybe things continue as expected, but maybe things don't?

The issue I have is that, from the outside of an event horizon (the rest of the universe), observers can't put together a coherent (and testable) timeline of events for an object falling in that includes a singularity. My understanding is that, due to infinite red-shift, it takes "till the end of time" for any outside observer to see an object cross the horizon. For these observers, the singularity creation event of course take place after the horizon crossing event. If the observer continues to wait for a very long time, they eventually observe the black hole evaporating. This evaporation must occur before the observer sees the object actually cross the horizon, and therefore must occur before the singularity can be said to form. So for all observers on the outside of the horizon, there is never a singularity that exists, or ever exists/existed, or can be interacted with, for all time.

Knowing GR breaks down, who's to say what form the inside of a black hole takes, if there is an "inside" to a black hole at all? The star could collapse into a new form of degenerate matter.. causality could stop... the immense gravity could create a degenerate or infinitely expanding space time where nothing can interact with anything, etc... the point is it's unknowable, and the breakdown of math suggests we're missing something. So we should be skeptical of anything the GR model predicts that's happening on the inside.

So, what I know is that:

1) I don't have confidence GR predictions of what happens on the inside of the horizon, not just because they're essentially untestable, but especially in light of the fact the GR model breaks down 2) I do trust the series of GR events that occurs on the outside of the horizon, in the testable part of the universe, which says a singularity makes no sense.

So I have confidence in the belief that in our universe, until the end of time, singularities can't form. Whatever happens "for real" can likely only be explained by a theory that unifies GR and quantum mechanics.

I suspect that whatever the truth behind it is, the answer would tell us a lot about entanglement/entropy, the "speed of causality", and the computational limits of the universe.

I'm a layman, I'm not just not right, I'm not even wrong on most things. Feel free to shoot all of this down!