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Black Holes: singularities or distributed?

 
Rancher
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I've been doing some reading on black holes (as you do) and there's something I'm trying to work out: From the outside it makes no difference whether the mass is concentrated at a point or distributed within the region inside the event horizon or even some intermediate size, but which is it?

Sure, it's all inside the event horizon and officially none of our business, but what is our best guess?
 
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Originally posted by David O'Meara:
...which is it? ...


Well, it's been a long time since I've been even remotely up on these topics, but I won't let that stop me from sharing (or even propagating) my ignorance by asking the following question:

Are we certain these options are mutually exclusive? That is, can we really say that the mass is either concentrated at a point or distributed...? Since perceptions of space/time get a little "bent" under these conditions, might there be a (seemingly) pluralistic nature here, akin to light's apparent wave/particle behavior?
[ July 17, 2006: Message edited by: marc weber ]
 
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If the mass were made up of units smaller than the black hole itself, and if they were somehow arranged inside the event horizon, then would it be possible that they were arranged in a non-uniform fashion? Perhaps quantum mechanics would even suggest that they must be, although nobody seems to know whether QM applies there.

Anyway, let's suppose they might be. Then they might rearrange themselves at some time -- but why? To get into a configuration of lower energy? This would reduce the mass of the black hole. This change could conceivably be observed, as for example "starquakes" in neutron stars have been observed. So there's a research project for somebody.
 
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Yes, I think QM (to the extent it has been or will be integrated with GR) would strongly suggest there won't really be a pure point-singularity in the center, so much as a fuzzy spike in density. However I think it would much more strongly resemble a point mass than it would a uniform distribution over the interior. Consider: inside the Schwartzchild radius, the mass is still mutually attractive, right? Are there any forces that would keep the mass apart? One of the main points of a black hole is that gravitational forces overpowered strong and weak nuclear forces (and EM forces) a long time ago. So other than fuzzy QM effects, is there anything that would prevent the masses from accumulating at the center? For a rotating black hole, I suppose the internal mass may be orbiting itself in a ring or disk. I know there would be an accretion disc outside the event horizon, but I'm not sure what happens inside. I imagine this has already been analyzed carefully by many people though.

I suppose a proper physics answer is that if we can't observe it, it's irrelevant.
[ July 17, 2006: Message edited by: Jim Yingst ]
 
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Is it even possible to go pass the event horizon? I am thinking that it is possible, but due to relative time, the outside observer will see that you take infinite time to do it.... Doesn't that mean that everything that entered the backhole is still at the event horizon?

Henry
 
Jim Yingst
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[Henry]: due to relative time, the outside observer will see that you take infinite time to do it

I think that's backwards. The outside observer will see that you appear to be aging very slowly as you are quickly being ripped apart by tidal forces and then sucked in. I could be misremembering though; it's easy to get turned around in relative time discussions.
 
David O'Meara
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The distribution of matter was actually the little thought. The bigger thought follows from this:

The gravity of the Earth measured on the surface of the earth is due to the sum total of the attraction of the mass of the earth. No surprises here. But if you travel beneath the surface of the Earth, the effect of gravity decreases. This new value is as if the entire outer shell had been removed and you only need to include actual mass between you and the center. (I hope that's clear)

Applying the same logic to a black hole with a distributed mass, at some external point is the event horizon. No problems there: nothing goes in, nothing goes out, bad 80's movies all round.

But internally the gravitational effects decrease as you move towards the center until you get to a region where there is no longer an event horizon. That is, there is the possibility of a bubble of real space inside the black hole. Now my reasoning suggests the region must be void - ie no matter at all. I get this from assuming that the matter in the 'event horizon' area cannot exert pressure on it, or it would imply transfer of data. Also, if there were matter in the area it would still count against the mass of the black hole, it would still exert gravitational forces on external masses and would therefore be subject to gravity itself. An gravitational force would pull this mass back into the 'blackhole propper', leaving the internal region real but void.

It's actually the tonsilitis keeping me awake, this is just to pass the time.
 
Henry Wong
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Originally posted by Jim Yingst:

I think that's backwards. The outside observer will see that you appear to be aging very slowly as you are quickly being ripped apart by tidal forces and then sucked in. I could be misremembering though; it's easy to get turned around in relative time discussions.



Jim,

I am not sure if I agree... When you say "quickly", I am assuming that you mean "fast", but not as fast as seen from the event horizon. (Multiple meaning for relative time here)

Since the outside observer sees the person age slowly implies that the observer sees everything happening slowly -- including how "quickly" the person is being ripped apart.

Henry
 
David O'Meara
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If the person (or object) travelling towards the black hole emits a pulse every second, from the frame of reference of the person outside the pulses will get further and further apart, and will also be spread over a longer time (ie the pulse itself will take longer and the gaps between them will be larger) and will get dimmer. This continues until the object almost reaches the horizon but never appears to get there, and the time between pulses becomes infinite. I believe that the object also dims until it is no longer visible but I won't swear on it.
 
Jim Yingst
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All right, I had a feeling I was probably answering that too quickly, and I was right. I agree with Henry and DOM; I had it backwards.
 
Henry Wong
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I believe that the object also dims until it is no longer visible but I won't swear on it.



IMHO, I think this is another issue. I believe how bright an object is, is based on how light reflects off of it. Unfortunately, time also effects the frequency of light itself. So what appears as one color will change color, and ultimately, become invisible to the naked eye, as the object approaches the event horizon.

Henry
 
David O'Meara
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That rings a bell, it's a color shift.
 
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Does black hole exist or it is just an assumption like what we are doing in this thread.
 
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Probably singular.

...makes it seem that it will eventually gain much power, that it can explode.

Why singular? We see only a point. Most likely thats what it is - one thing.
 
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A Brief History Of Time has some pretty interesting bits about black holes, although I must admit that much of it is highly confusing.
 
Henry Wong
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Originally posted by Sameer Jamal:
Does black hole exist or it is just an assumption like what we are doing in this thread.



IMHO, the existence of black holes have pretty much been proven since Hubble. Most of the theoretical effects of black holes have been observed -- you just can't actually see one itself.

Years ago, some colleague tried to explain to me the theory on why blackholes emits x-rays. I barely understood it. And I can't imagine the mathematics involved in this theory, which came before the observations itself.

Henry
 
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