What causes black holes?

[Realitycheck]

What causes black holes, as opposed to just big conglomerations of mass? Maybe something like a specific condition such as when a star explodes and great masses of atomic schrapnel are flung apart, coalescing into a conglomeration of atomic particles, without reforming back into the constituent atoms? I guess the particles would be too ready to reassimilate, though maybe not necessarily. Time to read this book and get caught up. Any ideas?

 

Maybe if it had a binary of a specific makeup which it then collided with.

Edited August 13, 2011 by Realitycheck

[pantheory]

What causes black holes, as opposed to just big conglomerations of mass? Maybe something like a specific condition such as when a star explodes and great masses of atomic schrapnel are flung apart, coalescing into a conglomeration of atomic particles, without reforming back into the constituent atoms? I guess the particles would be too ready to reassimilate. Time to read this book and get caught up. Any ideas?

 

This is not speculation but a straight question As to what black holes are in the first place, I think, is still debatable but what causes them to form involves very well developed theory with lots of supporting evidence. There seems to be little theoretical divergence on this subject.

 

http://www.astronomycafe.net/qadir/q1808.html

[Realitycheck]

So you are asserting that the gigantic horizons of galactic cores are actually that big, superdense and all?

[pantheory]

So you are asserting that the gigantic horizons of galactic cores are actually that big, superdense and all?

Concerning galactic black-hole theory as to their origins, I think, are more speculative. The most prevalent black hole theory in general relates to vacuous points in space. I prefer the super-dense model something like a highly compressed form of dark matter of some kind. We can observe in a number of cases the approximate diameter of the black hole's event horizon. We can also observe the extent of a central Galactic black hole's gravity. Based upon a great number of these two types of observations, we know that whatever the make-up of a black hole, that it occupies a relatively small volume compared to its gravitational influence. Based upon all of our studies to date, a black hole seemingly could not be matter in any presently known or understood form.

/

Edited August 13, 2011 by pantheory

[ajb]

Gravitational collapse is the reason black holes form. Attempts at understanding all this lead to the Penrose-Hawking singularity theorems. If I recall, the theorems basically say that the formation of singularities is unavoidable in general relativity, under some reasonable physical assumptions.

Edited August 13, 2011 by ajb

[Pincho Paxton]

My personal theory says that a black hole is a negative version of mass. Mass can fold into negative form, and it does this because space has a pressure of its own, because it is infinite. And this fold creates Galaxies.. you don't even need a big bang. Just add Dark Matter, which I prefer to call Aether.

Edited August 13, 2011 by Pincho Paxton

[ajb]

My personal theory says that a black hole is a negative version of mass. Mass can fold into negative form, and it does this because space has a pressure of its own, because it is infinite. And this fold creates Galaxies.. you don't even need a big bang. Just add Dark Matter, which I prefer to call Aether.

 

The question seems posed in the context of general relativity, so lets keep answers there. If you wish to discuss your own theory of black holes then I suggest you open a new thread.

[Realitycheck]

Interesting, how much Hawking has flip-flopped on the issue of infinitely dense universal singularities, starting at infinitely dense, then not, then back to infinitely dense in his latest book, according to ajb. At least, we have a consensus on black holes. I wonder why he went back to infinitely dense. I wonder if it has a mythological component.

[pantheory]

Interesting, how much Hawking has flip-flopped on the issue of infinitely dense universal singularities, starting at infinitely dense, then not, then back to infinitely dense in his latest book, according to ajb. At least, we have a consensus on black holes. I wonder why he went back to infinitely dense. I wonder if it has a mythological component.

The basis of all theoretical physicist's verbiage today, that I am aware of, starts with their mathematical models. I'd much prefer it were the other way around and then I think there mathematical models would have at least some chance to represent reality, which I think is totally not the case today. For them to first conceive of a totally logic idea/ explanation, and then to develop a mathematical model to reflect it, I think would be far more fruitful of an approach.

/

Edited August 14, 2011 by pantheory

[ajb]

Interesting, how much Hawking has flip-flopped on the issue of infinitely dense universal singularities, starting at infinitely dense, then not, then back to infinitely dense in his latest book, according to ajb. At least, we have a consensus on black holes. I wonder why he went back to infinitely dense. I wonder if it has a mythological component.

 

Hawking also "run" is work with Penrose backwards, to show that in the context of general relativity the Universe must have stated from a singularity. Roughly, the expansion of the Universe is gravitational collapse in reverse. Being careful, this would assume some physically reasonable conditions and is in the context of general relativity.

 

Now the presence of singularities is seen as a breakdown of general relativity. That is general relativity cannot cope with the physics we are asking of it. This points to the need for "new physics".

 

The thing that general relativity misses is quantum mechanics. One would expect that at small enough scales quantum effects of the gravitational field to become significant. Around the Planck length (or energy) one would expect the quantum effects to be no longer negligible. However, we do not have a very good handle on quantum gravity, so we have to be very careful and the physics becomes more speculative.

 

Generically we expect quantum gravity to regulate the singularity at the centre of a black hole and the initial singularity of the Universe. By this I mean that quantum effects will in effect remove the singularities. No one really expects the singularities in general relativity to be physically realised. They are expected to be an artefact of our poor understanding of gravity on the smallest scales.

 

A parallel can be found in classical electrodynamics and the electron self-energy. Classically it takes an infinite amount of energy to "assemble" an electron. We have a singularity in the theory. Yet we see electrons around us. This apparent paradox was resolved with the development of quantum electrodynamics.

 

I'd much prefer it were the other way around and then I think there mathematical models would have at least some chance to represent reality, which I think is totally not the case today.

 

People do build phenomenological models. These are driven by the want to fit data rather than have any kind of mathematical elegance. The phenomenological modes should be able to be understood as limits or special cases of more fundamental models.

 

For example we have the MIT bag model of nucleons, which basically confines non-interacting quarks into a "bag". It provides a model of confinement and you can get at okay nucleon masses. (But it does fail at predicting other things).

 

The fundamental theory here is QCD, which is a real pain to work with, especially at low energies where perturbation theory is no so good. So you jump to phenomenological models, like the bag model, non-relativistic models and others.All these phenomenological models should be seen as special limits or approximations to QCD.