[oneshtein]

> > it looks like this accretion disk was below the «event horizon»

> No it doesn’t.

It is, because of the silence before the sudden «burp». Something consumed all the radiation produced by the accretion disk. I know the only one possible solution: the «event horizon».

Astronomers says that they are not sure:

> "Black holes are very extreme gravitational environments even before you pass that event horizon, and that's what’s really driving this," Cendes said. "We don’t fully understand if the material observed in radio waves is coming from the accretion disk or if it is being stored somewhere closer to the black hole. Black holes are definitely messy eaters, though."

but I can use this as evidence that the center of black hole contains a dense and cold crystal. Why not?

Moreover, if fractal theory is right, then we are inside infinite number of black holes of increasing sizes (or other objects). But, if we are inside a black hole, why sky is black and space is cold then?

[ben_w]

> but I can use this as evidence that the center of black hole contains a dense and cold crystal. Why not?

The definitional trait of an event horizon is that it is causally disconnected from the outside universe. It is the "horizon" beyond which "events" cannot be causally connected to some observer.

A consequence of this is that nothing we observe on the outside can definitely tell us what's going on inside.

Closest we can get is creating a complete and consistent set of laws of physics and asking those laws what happens — it's fairly trivial to show there's an infinite number of such laws (such a demonstration is why Occam's Razor is even a thing), even despite the fact that right now we don't have a single one of them.

> Moreover, if fractal theory is right, then we are inside infinite number of black holes of increasing sizes (or other objects). But, if we are inside a black hole, why sky is black and space is cold then?

I don't even know what you think you mean with "fractal theory", but the reason space is black and cold is that (1) the hot surface visible in every direction to the right telescopes is very far away, and (2) the universe is expanding, and the combination of (1) and (2) means (3) it's been red-shifted so hard you can't see it with the naked eye.

The question of if the entire visible universe is the interior of a black hole in a bigger universe, has no apparent relationship in either direction to 1, 2 or 3.

[oneshtein]

> The definitional trait of an event horizon is that it is causally disconnected from the outside universe. It is the "horizon" beyond which "events" cannot be causally connected to some observer.

It's just a theory. When theory doesn't match reality — we replace theory.

> I don't even know what you think you mean with "fractal theory",

Fractal theory is simple: Universe is a 3D fractal, which means that if we will zoom in or zoom out for long time, we will see similar structures again and again and again, for infinity.

Thus, if we will zoom out, we will find our Universe as part of an unknown object of giant size, such as a dust particle in space.

However, if we zoom long enough, we will see that we are also part of a known object of even larger size: a dust particle, a star, a black hole, an grain on a beach, etc.

> universe is expanding

Nope. Imagine that we are sitting at surface of a rubber balloon and it deflates. We also see lot of rubber balloons around us, which are doing the same. We will see that surfaces of all balloons are moving away from us, so you may think that this rubber Universe is expanding. Surfaces of larger balloons further away are moving away even faster that surfaces of smaller balloons near to us, so you may think that this rubber Universe is expanding with acceleration, but this is just an illusion. In reality, balloons are deflating, their centers are barely moving.

> but the reason space is black and cold is that (1) the hot surface visible in every direction to the right telescopes is very far away

Yep, but why? Look, I'm trying to guess our location in outer Universe. Our base space is very rigid, it able to withstand powerful forces without hitting it limits. Black holes are able to hit limits of the space, so I suspect that equally strong forces are holding our space, thus we are inside in a black hole. But where we are in the black hole? We don't see curvature of space, thus we are in a flat part of the black hole. Where this flat part can be? IMHO, we are near to center of black hole, in the north hemisphere.

[ben_w]

> It's just a theory. When theory doesn't match reality — we replace theory.

Sure.

But if you throw away the theory of relativity, you don't have any evidence that black holes exist in the first place — every observation of something that points to the concept of "a black hole" presupposes that relativity is close enough to correct for event horizons to be exactly as one-directional as time. (That't not a metaphor, literally).

If GR is not close enough to correct for the event horizon to be there, then black holes don't exist either, they are meaningless words.

Most actual researchers know there's a problem with GR specifically because of black holes' singularities, and at least one of GR and QM because of the EH — but nobody knows what to do about it as all the attempts to fix it either violate existing observations or have no testable consequences.

> Fractal theory is simple: Universe is a 3D fractal, which means that if we will zoom in or zoom out for long time, we will see similar structures again and again and again, for infinity.

Then it is false. The universe is not scale-invariant.

If anything, the opposite of your claim: at large scales even within the range we can sense, the "End of Greatness" scale is around 100 megaparsecs, at which point everything starts to look homogeneous and isotropic; conversely at the quantum scale, concepts of "position" and "momentum" cease to be independent. Electrons don't orbit their nucleus the way planets do, every measurement of position is random from the distribution of the corresponding "orbital".

There's nothing to even suggest what you say.

> Nope. Imagine that we are sitting at surface of a rubber balloon and it deflates. We also see lot of rubber balloons around us, which are doing the same. We will see that surfaces of all balloons are moving away from us, so you may think that this rubber Universe is expanding. Surfaces of larger balloons further away are moving away even faster that surfaces of smaller balloons near to us, so you may think that this rubber Universe is expanding with acceleration, but this is just an illusion. In reality, balloons are deflating, their centers are barely moving.

What do the balloons represent here? Because if it's space, and the more distant ones are bigger, you've just put a funny map onto an expanding spacetime.

> Yep, but why? Look, I'm trying to guess our location in outer Universe.

Meaningless.

> Our base space is very rigid, it able to withstand powerful forces without hitting it limits. Black holes are able to hit limits of the space, so I suspect that equally strong forces are holding our space, thus we are inside in a black hole. But where we are in the black hole? We don't see curvature of space, thus we are in a flat part of the black hole. Where this flat part can be? IMHO, we are near to center of black hole, in the north hemisphere.

Now I'm sure you're trolling.

These words do not seem to connect to anything tangible.

There is no testable interior of a black hole, so we cannot say if they "hit limits of space" or not — the singularity in the middle is a mathematical consequence of a divide-by-zero that no actual researcher in the field takes seriously, in part because the maths underpinning general relativity presupposes singularities never happen. (To be more precise, spacetime is presumed to be differentiable, and thus sufficiently small patches can be treated as if they were flat — singularities can never be treated this way).

Black holes get more curved, less flat as you get closer to where the maths says the singularity would be. Outside a black hole this can be directly observed, it was one of the initial tests of GR that meant it was ever taken seriously in the first place.

And "in the north hemisphere"? There's no universe-spanning magnetic field to give that meaning.

[nathan_compton]

Hardly.

One can see the dynamics like this: the star is tidally disrupted and produces energy discharge via frictional heating (basically). Then the remnant gas is sufficiently spread out so as not to radiate much, then the dynamics of the accretion disk concentrate the infalling matter enough to heat up again and some of the material is ejected.

Given our simultaneous understanding of GR and other physical phenomena this seems like the most likely explanation.

[JumpCrisscross]

> I know the only one possible solution: the «event horizon»

Try the unstable region between the ISCO and EH.

> Astronomers says that they are not sure

They’re not sure where outside the EH.

> I can use this as evidence that the center of black hole contains a dense and cold crystal. Why not?

You’re bordering on trolling, but simply, it’s because the evidence doesn’t work.