# Black hole density infinite or finite?

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#### Mordred

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I was trying to puzzle out the disnities of a black hole singularity. I searched for the answer and read several articles on it. but want to make sure I understand if my undertanding is correct.
the Swharzchild raduis describes the mass of the blackhole which is based on no momentum and the size of the event horizon correct?
Now for inside the event horizon. In this case mass becomes infinite due to general relativity so the density would also become infinite, am I correct on this?

I was also curious on one other thing neutron stars compress electrons into protons to form neutrons. What would a black hole compress neutrons into? Is it possible that it compresses all the fundamental particles (6 gluons and 6 leptons) into one particle?

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#### Mee_n_Mac

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As I understand it the Schwarzschild radius describes the radius of a sphere such that if all of the mass of the object were to be contained within said sphere, it would collapse to become a black hole. Thus the SR varies with the amount of mass being considered. The Sun has an SR of ~3 km, which is not to say the Sun could become a BH but rather that if (hypothetically) all of the mass of the Sun could somehow be packed into a 3 km (radius) sphere then there's no known force that will counteract gravity to stop the collapse into a BH.

As for infinite density, yes, that's what's predicted but most people think it means that General Relativity no longer adequately describes what happens at those sizes, temps and densities. We need new physics to describe that regime. As for infinite mass ... no, the mass all stays there and remains the same as before the collapse. It's the size that (theoretically) goes to zero causing infinite density.

As to what particles (may) exist at the "singularity" ... I haven't a clue.

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#### ramparts

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Mee_n_mac's post is on the money. I'd add that black holes are (as he says) a prediction of general relativity, which is a theory of gravity, an attractive force. So when you compress matter inside its Schwarzschild radius, there's nowhere for it to go but down, if you're just looking at gravity.

But we don't entirely know how gravity interacts with physics at the smallest scales, so it's entirely possible that once you take those forces into account, something would pop up to prevent a true infinite density singularity from forming. After all, infinite densities are just weird and very difficult to imagine physically So the answer really is: we don't know. Yet.

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