Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Jon Francis on 26/08/2010 19:16:57
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Is there a limit to the size of a black hole?
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No, but it can be infinitely small.
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My guess is that quantum effects will eventually prevent it to be infinitely small (or singularity).
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No, but it can be infinitely small.
Actually, it can't, whether you're thinking in terms of mass or spatial size.
In terms of mass, a BH cannot have any less mass than the lowest mass sub-atomic particle and this in turn sets a lower limit on the spatial diameter of its Event Horizon.
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I was referring to the size of the event horizon which I take as the measure of the size of a black hole. The diameter of the event horizon would be related to the amount of mass that the BH has consumed. I wondered if the event horizon would always remain stable no matter the mass of the BH. When mass passes the event horizon it must still continue its journey towards the singularity. This would take time and as gravity slows time. The more mass the slower the time. Inside the event horizon the environment must be extremely volatile. Therefore immense forces must be at work which would increase relative to the amount of mass being compressed. I wondered would there come a point at which this activity would become to volatile and break the event horizon? Maybe even threatening the stability of the BH itself?
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the surface of the event horizon is supposed to be proportional to the energy inside the black hole. Inside the black hole, there is no space time as we know it because gravity is so intense that space time collapse.
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The diameter of the event horizon of a black hole increases linearly with the mass of the black hole As I mentioned above a black hole with a mass equal to that of the sun has an event horizon diameter of about one mile. The monster billion solar mass black holes at the centre of large galaxies are about as big as our planetary system i.e the orbit of uranus or neptune.
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No, but it can be infinitely small.
Actually, it can't, whether you're thinking in terms of mass or spatial size.In terms of mass, a BH cannot have any less mass than the lowest mass sub-atomic particle and this in turn sets a lower limit on the spatial diameter of its Event Horizon.
I'm not referring to the event horizon, I'm saying the mass is compressed into an infinitely small point.
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I understand there is a lower limit to stability for a BH. Below this the BH rapidly evaporates? What I was interested in was whether there is an upper limit to its size. A limit where above this the BH would become unstable and explode or dissolve in some way? It seems to me that the universe is constantly changing. Energy continuously strives to achieve stability in constantly evolving structures. Is a black hole the final state? It seems to me that although the universe is expanding all matter is also contracting. Will the universe eventually be just black holes with cold empty space between. Or will eventually all matter, dark and normal, and all energy, dark and normal fall into one black hole?
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Energy continuously strives to achieve stability in constantly evolving structures.
Perhaps. The ultimate stability is total chaos (entropy wins), at which point there will be no structures.
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Below this the BH rapidly evaporates? What I was interested in was whether there is an upper limit to its ...
A possible view is that a BH does not have an upper limit on how much stuff can get into it. Our whole universe may be trapped into a super-gigantic black hole and the microwave background radiation may be Hawking radiation.
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What I was interested in was whether there is an upper limit to its size.
Ah - right. The rate at which Black Holes 'evaporate' via Hawking radiation is dependent upon their temperature, the higher the temperature, the quicker it will evaporate. However, the larger a BH is, the cooler it is, so the slower it will evaporate. As a BH gets larger then, it will become cooler and therefore evaporate more slowly, implying that there is no upper limit to the size of BHs.
Nothing can ever actually reach 0K though, so no BH can ever be entirely 'stable', regardless of its size.
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According to the Schwarzschild solution of Black Holes the net inertial rest mass(m)of a gravitational system is direcly proportional to the distance (d); and without this solution we might not even be discussing black holes.
d = 2mG/c².
If more mass is added to the gravitational system, the Black Hole increases in size or space. If mass is ejected or removed from the gravitational system, the Black Hole decreases in size or space.
So the size limit of the Black Hole is determined solely by the quantity of the matter of the gravitational system.
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Nice question, but I would expect it impossible to answer. How big is the universe :) and how much 'normal' matter do it contain,uh uh, not percentages now, some 'real numbers' please :) what are the distances from all that matter to the super-big black holes we know of? As well as to those we don't know of??
As for how small they can be? Plank size I believe to be the limit.
Take a look here. Micro black holes (http://en.wikipedia.org/wiki/Micro_black_hole)
And can they create worm holes? if so, do they need to go to another universe? Why not ours :) A line of black holes connected at the metaphorical navel, via their worm holes :) Like mothers bringing forth their off springs, well, not really. Girls have an unbroken lineage through their umbilical cords going all the way to that first mother. We males on the other hand, ah well..
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CPT, the space inside the event horizon will be space too. There are several theories discussing the possible size inside, as observed when having passed the event horizon.
Take a look here first.
Dark flow. (http://news.nationalgeographic.com/news/2010/03/100322-dark-flow-matter-outside-universe-multiverse/) And then read this Black Holes. (http://news.nationalgeographic.com/news/2010/04/100409-black-holes-alternate-universe-multiverse-einstein-wormholes/) and here is the paper he wrote on it Cosmology with torsion - an alternative to cosmic inflation (http://arxiv.org/pdf/1007.0587v1)
In fact, I've read several propositions in which space inside a black hole is expected to be a whole universe in itself, although without any communication possible between ours and the one inside. As for Hawking radiation.
"" Hawking predicted that energy fluctuations from the vacuum causes the generation of particle-antiparticle pairs near the event horizon of the black hole. One of the particles falls into the black hole while the other escapes, before they have an opportunity to annihilate each other. The net result is that, to someone viewing the black hole, it would appear that a particle had been emitted. Since the particle that is emitted has positive energy, the particle that gets absorbed by the black hole has a negative energy relative to the outside universe. This results in the black hole losing energy, and thus mass (because E = mc2).
Smaller primordial black holes can actually emit more energy than they absorb, which results in them losing net mass. Larger black holes, such as those that are one solar mass, absorb more cosmic radiation than they emit through Hawking radiation. "
I don't agree to the view that a black hole can communicate myself as it would mean that it no longer would be a singularity. And this makes perfect sense to me, but if you see the particle-pairs as entangled, and then assume that it is the one destroyed that somehow will imprint the information on its entangled surviving twin, we will have a problem calling it a singularity. And then all bets are off.
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read this... no time maybe no space? Can someone explained in what the holographic principle change the Hawking radiation? According to the conservation of information there is no Hawking radiation or what?
http://en.wikipedia.org/wiki/Holographic_principle
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Susskind and Hawking were at "at war" over this point - so I don't think there is an easy answer. If string theory is proved to be correct - then it looks as if holographic theory might be shown to be correct. BTW Hawking no longer claims that info is lost in a black hole and has conceded the bet he made with preskilt - Hawkings reasoning explaining the maintenance of information is beyond me.
The holographic theory is just one theory that explains the problems with loss of information in a black hole. Hawking radiation hasn't been disproved by the perceived need for conservation of information; in fact, if I understand it correctly, it is the idea that Hawking Radiation cannot "carry back out" the information that is lost to a black hole coupled with the fact that hawking radiation puts a finite life span on small black holes that partially creates the need for a theory to cover the loss of information.
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Thanks to you, Yor_on "the viking hidden under the table" for your articles... Nice reading it.
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if there is no Hawking radiation, maybe the first black hole created by the Large Hadron Collider will be the first and the last for mankind... Maybe it will happened in December 2012... [:0] [xx(]