# B Condensed matter in a Black Hole

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1. Sep 6, 2017

### mpolo

I am wondering if there is some type of matter in the core of the Black Hole. Is it possible to compute the distance from the surface of the Black Hole Core to the Event Horizon? Oh that would be fun to calculate.

2. Sep 6, 2017

### Orodruin

Staff Emeritus
No. There is no such thing as "the core of a black hole".

3. Sep 7, 2017

### Demystifier

There is no such thing in classical general relativity, but there could be in the quantum theory. See
https://arxiv.org/abs/1505.04088

4. Sep 7, 2017

### Orodruin

Staff Emeritus
While true, I did not see a real point in bringing it up in a B-level thread. I think that words such as "could be" are too easily dropped for "is" by laymen when passing on this type of information.

5. Sep 7, 2017

### Demystifier

You are right, this is not appropriate for a B-level thread. But still, someone reading it may find it interesting.

6. Sep 7, 2017

### mpolo

@Orodruin So what is inside of a Black Hole if there is no core matter? I was under the impression that know one really knows what is underneath the event horizon. If know one really knows what is in there then there is a possibility that it could be made up of some strange type of ultra dense matter. At any rate for discussion sake lets just say there is a sphere of some type of matter. I think it would be fun to take a guess at the density and mass of the sphere mathematically speaking and then calculate the distance from that sphere which is most likely rotating rapidly to the event horizon. That would really be fun to put into a computer program.

7. Sep 7, 2017

### Orodruin

Staff Emeritus
It is very easy (and common among laymen) to think of a black hole as if it occupies some part of Euclidean space. Unfortunately, doing so is not very appropriate. What you would be dealing with is a curved space-time and much of your intuition of what it means "to be somewhere" flies right out the window.

Looking at the simplest case of a classical Schwarzschild black hole, it is actually a vacuum solution - there is no matter anywhere, the Schwarzschild mass is a property of the space-time. The singularity is not so much "located in the middle" as it more related to a moment in time than to a position in space.

8. Sep 7, 2017

### mpolo

When the Big Bang happened was that the result of a Black Hole that expanded or exploded?

9. Sep 7, 2017

### Orodruin

Staff Emeritus
No. Regardless of what you might read in popular literature, the Big Bang was not an explosion in the usual sense of the word.

10. Sep 7, 2017

### Orodruin

Staff Emeritus
No, it is not the radius, at least not in the sense that you would recognise it. If you look at the Schwarzschild solution inside the black hole, it is actually a time coordinate. Regardless of that, the definition of the r coordinate in the Schwarzschild solution is that the area of the corresponding sphere in the spherically symmetric solution should be $4\pi r^2$. Note that this does not mean that this sphere has a "radius" $r$, since it is a hypersurface in 4-dimensional curved space-time.

This nomenclature is a bit toxic. Physics deals with observations and describing them. What is subjectively "real" is a matter of philosophy.

The total energy of the universe is not very well defined in GR and if you manage to define it it will not be conserved in an expanding universe. One of the more popular theories about what happened before the hot big bang is inflationary models. Such models leave the universe completely empty, spatially flat, and cold apart from the presence of an inflaton field that by decaying to matter and radiation reheats the universe.

11. Sep 7, 2017

### Staff: Mentor

The OP question has been answered, and a number of overly speculative posts have been deleted. The thread will remain closed.

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