Black Holes

But the event horizon is a result of the singularity - if that in fact exists. So there is a direct dependence there that can't be ignored.

The physics used to predict the existence of the singularity are the very physics we know don't work once you cross over the boundary of the event horizon. Relativity, spacetime, the four forces being seperate simply don't apply once you pass the event horizon. So saying if they did you'd get a singularity is a very sloppy inference IMHO.

I would be happier to say an event horizon is a boundary between relativistic spacetime and one or more layers of non relativistically governed existence. Its simply a transition layer, use different rules on the other side of that transition boundary - not the rules of relativity operating in spacetime.

There appears to be a string theory answer to blackholes to be published in March http://researchnews.osu.edu/archive/fuzzball.htm

This theory provides a mechanism for any matter or energy falling into a blackhole to be preserved - if jumbled. Its a major piece of work given the is one of Hawkings and Throne's research bets and a millennium problem to boot!

Hi G_Day,



I know, but doesn't change the fact that from an escape point of view, it's the event horizon which produces all external effects (more to the point, it's the whole system, represented by the event horizon).



This isn't exactly correct. In large black hole systems, the event horizon is virtually undetectible, both on approach and beyond it. It's the singularity itself where our math begins to break down, not the horizon boundary itself.

As a matter of fact, if our entire universe were inside the event horizon of a super super massive black hole, we would not be able to detect it (or so I've read).

I am pretty certain relativity and space time breaks down at the threshold of the event horizon, whether you have instrumentation to exactly detect this transition or not. But my point was the physics used to support the notion of there being a singularity are General Relativity itself. GR also implies that time and space theoretically seem to invert their properties if one crosses and event horizon. Distance from the singularity is really just a measure of time and space has no directions. Its wierd.

General Relativity implies the singularity arises because the enormous forces of gravity overcome the nuclear forces that normally prevent an endless collapse and implosion of matter or energy - with no regard to what changes may be happening to the force carriers themselves, nor spacetime at such ultra high energy levels. This is flawed because at such high energy levels the force carriers themselves may re-combine and this could readily lead to a definite changing of the laws of physics underpinned by General Relativity. The Big Bang itself - up to the moment of inflation may indicate that the four forces can combine - otherwise the Big Bang shouldn't have been able to occur given it would have had to overcome its own crushing gravity field if GR was what governed it. To the LHC operating in 2007 may show the first proof of the four forces combining into 3 forces at around 200 GeV.

At energy densities that high I prefer to intuit that the four forces start to combine again - like the big bang just at inflation but played in reverse. I'll check the maths but I expect you'll find at the event horizon you are getting close to the threshold energies of the heirarchial problem needed to study the recombination of the 4 forces - 10 ^ 14 GeV.

If the forces recombine then eventually at 10 ^ 19 GeV gravity itself is swallowed into quantum gravity - meaning the science used to say GR (which then doesn't apply there) assert a singularity is mis-used. Quantum Gravity will control the inside of the event horizon, not gravity or nuclear forces or electromagnetism!

* * *

Also we don't "know" that all the effects are the cause of the event horizon layer, and not what is beyond this layer. We have no data nor theorums to say what is caused by the event horizon layer versus what is the structure and external implications of any supposed internal layer/s. We can't yet say what effects do we predict and how do these layers if they exist interact with the event horizon layer. Nor do we have enough finely distinguished raw data to rule competing theories in or out.

The jury is still definitely out on all the competing theroies.

huh
If a black hole is the result of an imploding star, wouldn't an exploding black hole simply produce a star again. With all the extra matter and energy it's taking in, the thing could be huge, almost as fat as eric cartman himself.

Is a black hole 2 or 3 dimensional. If its 3D, then its more a black sphere, but that doesn't explain the vortex effect like how matter is spiralling around it as opposed to a random orbit like an electron around a nucleus. If it's 2D then it's hard to see how anything in our 3 dimensional universe can interact with t, but it could be like an inter-dimensional portal.

The Event Horizon encloses a sphere, and things orbit it just like any other gravitational well.



The Singularity itself is probably considered to be one dimensional. And Yes; nothing in our universe can interact with it. Strictly speaking, nothing in our universe can interact with anything inside the event horizon either, because once something has crossed that horizon, no information about it can ever reach us.

I thought there was debate about information escaping the event horizon in the form of Hawking radiation or something like that.

Re: huh

Black holes don't explode, so no.

It's a 3D phenomenon.

That part is pretty esoteric, and I'm not sure I can define it precisely, but my general impression is that "information" can't escape, whether it be ordered electromagnetism, or ordered matter.

The Hawking radiation is just virtual particles which have become disassociated from their counterparts by the event horizin. My impression of this is that the resulting virtual particle leakage bears no structure related to anything inside the horizon because it's an elementary "virtual particle" (whatever that is exactly?).

Maybe Brandon can explain this part better. He seems better at the details than I am.

Well, quantum gravity is a little over my head, but this is what I know. Hawking radiation is only significant for very small black holes. Virtual particle-antiparticle pairs are sometimes created outside the event horizon of a black hole, just as in ordinary pair production here on Earth. I believe that the black hole supplies the energy from the gravitational potential energy of its field.

Three things can happen to a pair of particles just outside the event horizon:

1. Both particles are pulled into the black hole.
2. Both particles escape from the black hole.
3. Before the pair can annihilate one another, one or the other of the pair is pulled beneath the event horizon, while the other particle escapes.

For the third possibility, the particle that has escaped achieves a positive energy and can be observed. The particle that was pulled into the black hole remains virtual and has a negative mass-energy. The black hole absorbs this negative mass-energy and as a result, loses mass and appears to shrink. The rate of energy emission is inversely proportional to the square of the black hole's mass. Hawking radiation includes all sorts of particles - both particles and antiparticles of all kinds, and photons. Photons can be produced in pairs, although a photon is its own antiparticle. They are produced in pairs with complimentary spins. I believe that the question of whether the radiation can carry information from within the event horizon is not yet well understood.

Maybe Eric Brown or g_day knows more.