View Full Version : Could a black hole explode??
10-06-00, 01:39 AM
Plato has strongly suggested in a previous post that gravitational attraction severely overcomes the expansion of gasses caused by heat. If a black hole has such a great gravitational pull that not even light may escape its grasp...how could it EVER explode?
Exploding is maybe a violent word, swetting would be a better way of putting it :)
There is a theory, put forward by Stephen Hawking which says that a black hole radiates out elementary particles like electrons, protons, neutrinos and such.
A black hole is defined by its event horizon, an other name for it would be the point of no return. Once you come this close to the center of the black hole there is no way you can return to normal space: you are doomed.
In quantum theory the vacuum is far from empty, it boils and bursts with an endless creation and absorption of elementary particles. The net result is zero and this is way the vacuum seems to look empty to us.
Hawking asked himself what would happen with this process of creation and absorption at or very close to an event horizon of a black hole. Suppose a proton/anti-proton pair was created close to the event horizon so that the anti-proton would end up in the black hole while the proton would end up outside the black hole.
What has happened ? Well, the black hole has actually last a tiny bit of mass, represented by the exiting proton.
This process happens all the time and if the black hole has not enough influx of particles to withstand this loss it will slowly but surely evaporate all its mass. This can take some time of course, like for a black hole with the mass of our sun it would take 'a number with fifty zeros' years which is a lot longer then the age of our universe ;)
10-06-00, 11:16 PM
You are much deeper in this stuff than I am. Does this theory hold weight with you or do you submit it as just that, a theory?
10-12-00, 11:14 PM
In otherwords Plato you die!!!. If there are such things as black holes then their must be light holes?
[This message has been edited by Epitectus (edited October 12, 2000).]
11-01-00, 03:59 AM
One thing that's made me wonder is that Hawking's theory of evaporating black holes is so based on the chance of quantum mechanics. If the particle /antiparticle pair is created, aren't the chances equal that one or the other will fall in and the other escape. Wouldn't there only be a fifty percent chance that the black hole would absorb the antiparticle? After a long time, the 50/50 chance would just even out the evaporation leading to an average energy loss of zero.
Since Hawking is smarter than me, there must be some physical law causing the antiparticle to fall in more times than the regular particle. (or maybe I just debunked his entire theory, yeah right)
Actually it doesn't matter which of the two particles gets absorbed in the black hole; either way you can say the black hole has lost mass: to use Plato's example of the antiproton-proton pair, the two particles are created right at the event horizon of the black hole, and one of the two is pulled into the black hole. The other one can no longer annihilate with its counterpart, so it continues its trajectory, away from the black hole.
To an outside observer, it would look like the black hole has emitted a proton (or an anti-proton, depends on which of the two got absorved) and hence that observer would say the black hole has lost mass.
Note: I also don't know the exact mechanism of how you can deduce that the outgoing protonmass/energy had to come from the black hole itself. I suppose Hawking has a decent enough explanation for this :).
"The best thing you can become in life is yourself" -- M. Eyskens.
Crisp is entirely correct on this.
About the mechanism, that would be simply the conservation law of mass/energy.
The virtual particles that are created all the time in the vacuum are virtual because they exist only for a limited amount of time, a period that short that the two particles can't fly further then their own wavelength. (as weird as that might sound)
What the black hole does is make one of the virtual particles real, bestow it with energy as it were. The only place it can get that energy is its own gravitational energy, that is what is reduced.
I err, therefore I exist !
Good to see you back up and posting here :).
About the time interval these virtuql particles live in; the maximum lifetime is probably determined by the energy-time uncertainty limit, no ?
"The best thing you can become in life is yourself" -- M. Eyskens.
02-27-01, 10:25 PM
Mr. Hawking should shift his logic away from the clasical macroscopic basis. The event horizon is a gravatetic/energy gradient not some thin shell. The clasical e=mv^2 determines where the event is for each mass. A more reveiling approch: think of the event horizon where light is frozen--becomes a standing wave as e' for a given m' increases the event horizon increaces in frequency, so is closer to the core. Clasical again higher energy, smaller orbit, shorter period. There is no limit to this effect. We reconize only a limited scale of EM. We as yet have neither theory or proof of some top or bottom to the scale. Hence claming that event horrizon even exists::: is not reletive.
18 April 2001 Reply to nefasdeux (Oct. 2000)
I agree with you, there is a 50/50 chance the anti particle will be absorbed or the particle.
Now if the particle is absorbed, it seems to me that the
anti particle in its travel would sooner or later meet up with a real particle. And woosh ! it would disapear. The net result would be the black hole gained a tiny bit of mass.
Sighned "apolo" new member
That would violate the conservation of energy: if the black hole gains mass and it emits a particle at the same time, mass would be created out of nothing.
The only way to preserve energyconservation is to assume that the energy used to create the "escaping" particle came from the black hole itself. Hence the blackhole will have lost energy and evaporates over time.
From apolo 20 April 2001 11^19 pm MST
Thanks for your reply Crisp. You are saying that if the black hole absorbes the proton and the anti proton escapes, the black hole cant gain mass (one proton) because that would contradict the law of mass/energy conservation by creating something out of nothing.(Whats one little proton when the BIG BANGERS can create a whole universe out of nothing) But thats not my point.
The black hole gains the proton, but the anti proton sooner or later meets a real proton -of which there is many floating around in the universe- and anihilates it. End result the black hole gains one proton, the universe loses one proton. Everything is in ballance.
BTW I dont beleive the theory of Hawking Radiation, it is too contrived (fantastic) I am not even sure that black holes even exist. Fred Hoyle in his latest book "A Different Approach to Cosmology" appears to agree with me.
That's only one side of the problem: it could also be that the antiproton is absorbed by the blackhole and that the real proton escapes.
In this scenario, the black hole would have gained mass (that of the antiproton) and the universe would have an extra proton. Violation of energy conservation. (Unless you also take in account that the real proton could eventually wind up meeting an antiproton and annihilate.. But that is not what Hawking radiation is about anyway).
The reason this doesn't work out is the origin of the two particles: from the moment the virtual particles become real particles, the energy of the black hole decreases by the amount of energy required to create a proton/antiproton pair. The black hole regains some (but not all) of this energy when one of the two particles falls back into the black hole. The net result then is: black hole's mass has decreased by one (anti)-proton and the universe has gained one (anti)proton.
No violation of energy conservation.
I must agree fully with Crisp here.
The quatum vacuum is boiling with virtual particles that never really become real because they don't exist long enough. However strong fields be they electromagnetic or gravitational in nature can provide the energy nescessary to make some of the virtual particles real. This happens for example when an unstable atom decays while emitting an electron an an anti neutrino through the weak force.
Where do the electron an anti neutrino come from ? Out of the vacuum, a neutron turned into a proton and created the other two particles in the process to conserve charge and momentum. Where does the energy come from : the proton has slightly less mass then the neutron.
Same goes for the black hole, in this case the strong gravitational field does the trick.
If you don't accept the existence of black holes, then I would love to hear your explanation of how something the size of 1 A.U. can contain a mass of more then a million suns like the object we seem to find in the centre of our galaxy (Saggitarius alfa I think it is called)
From apolo Reply to Crisp and Plato. 29 April
You dont seem to get my point. ( BTW my last post didn't appear on screen) I do agree that if the anti proton goes to the black hole and the proton goes to the universe, it will look like Hawking Radiation.But; if the opposite happens !
The proton goes to the BH and the anti proton goes to the universe, the BH gains a proton and the universe loses one.
And how can you possibly argue that there is not a 50% chance that either possibility happens. That would average
out the BH gaining and losing mass over time !
Your question ? what do I call a 1AU mass at the centre of the galaxy? I call it a great concentration of mass.
Or to borrow from Fred Hoyle a" Near Black Hole"
But I don't accept that the clacical definition of a BH exsist in nature.
You may consider me a maverick, but mavericks changed the history of science. Galileo, Newton, Einstein ! no one beleived them at first.
OK. Give me your best shot. Signed Apolo
No, we do get your point allright :). But I think I have a clue where your reasoning conflicts with ours.I can't find any other way to formulate this without repeating the whole scenario again, so here it goes:
Step 1: A virtual proton/antiproton pair is created near the event horizon.
At this moment the easiest would be to state that the energy needed for the creation of the two particles is "borrowed" from the black hole's mass. That means that during that very short time, the black hole's mass has decreased with 2 protonmasses (mass of antiproton equals mass of proton).
I *think* that is what happens. The truth is that noone knows because the particles annihilate faster than anybody can ever possibly measure (this has to do with the energy-time uncertainty relation). So in a way the previous sentence is incorrect.
Step 2: The proton or anti-proton is absorbed.
Blackhole: minus two proton masses (from step 1) and now plus one proton mass (step 2). Net result: black hole minus one proton mass. From this moment on, the remaining antiproton or proton has no partner to annihilate with, so it becomes a real antiproton or proton.
I agree that there probably is a 50% chance that either of the two scenarios happens. However, in both situations the black hole loses mass.
You take this one step further and argue that if the remaining particle is an antiproton, that it will annihilate when it encounters another proton. On the other hand, you can also argue that if a proton escapes, it could meet an antiproton and annihilite as well. This has however nothing to do with the mass of the black hole. From the moment one of the two virtual particles has crossed the event horizon, you are forced to conclude (within the current theoretical framework that I am awar of, how crappy it might appear) that the black hole has lost mass. Whatever happens afterwards is irrelevant to the black hole.
I hope this clarifies the situation. Corrections/suggestions are welcome (I am not a fieldtheory expert ;).
such calculations may seem incredibly rarefied and esoteric.but they are certainly a far cry from the stark reality of the stars and neb clouds,i think in the future centuries we will explore black holes in close ups.when that day arrives we will need the guidence of hawking,wheeler,to keep us from the perils of the cosmic death trap.theres one thing for sure,i wouldnt like to be there,i leave u this question,what would happen if a black holes gravity weakens?is it enough to kick start a new theory?
A black hole's gravity weakens as it slowly evaporates matter into space, using the mechanisms described above (assuming they are right ofcourse :)).
Reply to CRISP. It seems that no one gave an answer to my last post 23 April even though I asked you to give me your best shot. I will expand further on my theory. You said that if a proton anti proton is created near the event horizon and the proton goes in to the BH and the anti proton escapes and eventually annihalate a real proton in the universe. The BH has somehow lost a bit of it's
mass (energy) Why ? the BH has nothing to do with the creation of the 2 virtual particles, they were created outside the event horizon ! The BH gained a proton, and the anti proton (which can be considered as anti mass) is sooner or later going to run in to a real proton in space which it will annihilate. Ergo; the BH has gained mass (one proton).
If you have a "logical" counter argument, please let me know.
Okay, forget about the annihilation of the anti-proton. It has absolutely nothing to do with a black hole evaporating. Protons can also annihilate (sooner or later they will run into an antiproton that exists in the universe).
It doesn't matter whether the antiproton or proton exits the black hole: both have the same mass.
Just because the particles are created outside the event horizon doesn't mean that they don't feel the gravitational influence of the black hole. In a normal situation, the proton-antiproton pair would be created and annihilated (Hawking would say that for a tiny timefraction the black hole loses 2 proton masses here, but it gets them back through the annihilation). If one of the particles disappears into the black hole, you are left with a particle that suddenly popped into existence. It must have borrowed that energy somewhere, and it is common to say that it got it from the black hole's gravitational field. Since the gravitational field is related to the mass of the blackhole, you can say that the black hole lost mass through its gravity (the BH had to give 2 proton masses of energy to form the particle pair, but one particle escapes and the BH only gets one back... Net loss: one proton mass).
From apolo. Thanks crisp for your speedy reply last night. . I read it several times and I understand what you are saying. However you are making the assumption, that if a virtual particle pair is ceated just outside the event horizon then the BH loses energy equivalent to 2 protons before anything else happens (the absorbtion of one of the 2 particles) What logical line of reasoning leads you to that assumption?? Virtual particle pairs are created all over the universe all the time with no help from BHs. So why would the creation of a pair near the event horizon take energy away from the BH. You also treat anti protons as particles having mass. I realize that anti particles are poorly understood by scientists, actualy they are purely hypothetical. But my understanding is, that if they do exist they are "negative mass" that is why they can annihilate a real particle and nothing is left.
Thanking you for your patience. Regards apolo
The exact mechanism of how the 2 proton masses are borrowed from the black hole is not known to me. I am still to receive a course on Quantum Field Theory (which explains this phenomenon). Perhaps Plato can be of some help here ?
Concerning the antiproton: quite a lot is known from antimatter. One thing we do know for sure is that antiprotons have the same mass as protons (about 938 MeV/c2), so no "negative" mass. This has been experimentally verified, and is also theoretically predicted (for the techies: because of the CPT invariance theorem). The difference between a regular proton and an antiproton is in the quantumnumbers (these are numbers used to describe the characteristics of a particle).
Proton : charge +e , baryonnumber +1 , isospin +1/2 , ...
Antiproton: charge -e, baryonnunber -1, isospin -1/2, ...
For the exact annihilation proces, I'll have to refer you to a QFT expert once again. The basic elementary particles courses I took did not cover that subject (unfortunately) ;).
06-12-01, 08:46 AM
I do not believe there is any energy 'borrowed' from the BH. But I also do not believe that there will be a mass leak from the BH. The main reason is that in the extreme environment within or near the 'event horizon' -let alone in the singularity where everything ends- of the BH, concepts like protons, matter and the like lose their meaning.
Try this, it is a simple explaination. Maybe to simple.