[spwa4]

Layman opinion here: If a black hole forms, the point where it forms is an event horizon, but not a singularity. Then, while things get worse, it disappear from the universe.

So why would a singularity ever form? And what can't be formed, can't exist.

[mr_mitm]

Cosmologist here, the event horizon is not a true singularity. There is a singularity in certain coordinates, but it goes away when doing a coordinate transformation. There is nothing physically strange going on at the event horizon. The physical singularity is only at the center.

[rbanffy]

I have the (layman) impression that there is no inside - that spacetime is so stretched around the event horizon that there is no spacetime beyond it.

But, then, I've never seen anywhere that the mass of the black hole (which is very much a real thing that exists in spacetime) is distributed over the event horizon, which would be at the biggest amount of mass a given region of spacetime can hold, and is not concentrated on a point with infinite density inside it.

[nh23423fefe]

black holes have an interior, you wouldn't notice if you passed the event horizon of a large enough black hole.

[spwa4]

Wouldn't you?

1) you'd see infinite space dilation. Distance between you and anything would increase to infinity. It doesn't even matter if it's closer to the black hole from you or further away. I wonder if it even occurs with things that fall into the black hole with you.

2) You'd see time pass infinitely fast. I'd say "behind you", but not really of course: anything already fallen in you wouldn't see, and you wouldn't see anything exactly at the same position as you do, so anything you can see would see time pass infinitely fast. You'd be "transported to the end of time".

3) You'd see the whole universe compress into a single point (like in a lens I presume)

I wonder if this wouldn't present problems. The whole point of Hawking radiation is that the black hole will stretch out the wave function of light, in both ways (it "transports energy" from the virtual photon falling in to the particle escaping. The particle falling in loses energy, and keeps losing energy forever, while the particle escaping gains energy and since gravity has infinite range, it also keeps gaining energy forever, it's just that the amount decreases exponentially, never quite reaching zero. The particles never quite become real particles, however virtual particles do interact, so I'm not quite sure what makes them virtual, aside from their origin). Wouldn't it stretch out the wave function of any particle? And if you stretch out the wave function of a particle, you reduce it's energy. If you stretch it out infinitely you reduce it's energy, in the limit (but the limit is the event horizon), to zero. And the particles themselves aren't zero size: they would "see" this happen. Even the famous "point-particle" that is the electron has a wave function that occupies a portion of space (in fact, it occupies a surprisingly big volume)

So the mass of black holes could be in these frozen particles being teleported to the end of time, while losing energy.

[ndsipa_pomu]

> You'd see time pass infinitely fast

I've often wondered about that - whether you'd see to the end of the universe. However, I've seen various descriptions using Penrose diagrams that show that events from far enough in the future would never be able to reach the intrepid explorer before they hit the singularity at the middle of the black hole (assuming that one exists).

[GoblinSlayer]

You won't. Infinitely fast time means infinitely strong Hawking radiation that will just burn you instantly before you reach event horizon, but you will first catch a glimpse of heat death of the universe.

[ndsipa_pomu]

> but you will first catch a glimpse of heat death of the universe

That doesn't seem to be possible as information/light from the end of the universe would not be able to reach you.

There's a discussion of it here: https://physics.stackexchange.com/questions/82678/does-someo...