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I know that we can't actually see a black hole form, because of time dilation, and we would see a frozen image just before the final collapse past the event horizon, slowly redshifting to nothing... but lets imagine that we were falling in with it. As we crossed the event horizon, we wouldn't see anything special, we just wouldn't be able to get out...

I know some of our laws of physics break down, and make mathematical nonsense, but surely some things still work as they should. For example, atoms that are pressed close enough together are forced to fuse. This would be the case even more as the star collapsed more and more, after attaining black hole status and it was shrinking into an ever increasing tiny point.

I know that normally, fusion stops as the core of a star gets to iron because past that, fusion is endothermic. But if the star is collapsing towards infinite pressure, then the fact that it isn't energetically favorable doesn't really matter anymore. It can't not fuse simply because it doesn't "want" to, right? I mean it has no choice but to fuse, its collapsing and getting higher pressure and temperature whether it likes it or not.

So how far would that go? Would it collapse into elements so large that normally they are so radioactive that they only exist for a nanosecond or less? It would seem that under the extreme pressure of a black hole, radioactivity, even with extremely unstable elements, would become so energetically unfavorable, that it wouldn't be able to happen, thus the weak force would break down? I mean think of a pressure a billion times higher than the core of a star... At some point, ejecting a neutron would be impossible, it would require too much energy... Then it would fuse into even heavier elements, elements that we normally think of as impossible to exist... I mean what choice would it have?

Also, one more thing... I know that a black hole has a temperature, and its usually in the nanokelvin range, emitting nothing but tiny bits of Hawking radiation. But that is the temperature that we measure from the outside (kind of like saying the Sun is only 5,000 Kelvin, because that's the photosphere's temperature, even though it's 15 million in the core)... But inside the black hole, under greater and greater pressures and densities, the temperatures in the middle of the matter would be trillions, or more, right? Maybe even as hot as the Big Bang?

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  • $\begingroup$ If you mean by fusion that the constituents get closer and more dense, then the answer is surely yes. On the other hand if you mean by fusion that nuclear energy is released in the process, then the answer is surely no. Black holes form because the nuclear fusion fuels are all exhausted and the gravitational attraction is no longer balanced by the elevated temperatures associated with nuclear energy release. As the core collapses the nuclear force switches from being attractive to repulsive and becomes even more repulsive as the density increases. Either a black hole or a neutron is formed. $\endgroup$ – Lewis Miller Jul 7 '16 at 15:27
  • $\begingroup$ That would be a neutron star. $\endgroup$ – Lewis Miller Jul 7 '16 at 17:35
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The study of quantum mechanics has taught us that asking questions about things that "really" happen even though they can't be observed is a recipe for making nonsensical or physically meaningless statements. Physics, like all healthy sciences, is an attempt to describe things that can (at least in principle) be observed.

Numerous valid general-relativistic arguments show that no information can escape to the outside world from within the event horizon. Therefore questions about what happens inside the event horizon are moot.

Sorry --- this is the world we live in.

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  • $\begingroup$ Almost everything that physicists study these days "can't be observed." The difference between things happening inside the beamline of an accelerator and things happening inside a black hole, is that we can't even observe the consequences of the consequences of the consequences of whatever it was that our theory says might have happened inside the black hole. No experiment, no physics! $\endgroup$ – Solomon Slow Jul 7 '16 at 13:13

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