Can black holes convert matter into antimatter?

[Mr Skeptic]

From what I understand, producing antimatter would be a very expensive proposition by most means. But if you had a small black hole, and fed it only or mostly with protons, you could get a highly charged black hole. If the black hole were to shed its charge, my guess is that it would do so with the lightest positive particles -- positrons. So would it be possible to throw protons into a black hole and get back energy and positrons via Hawking radiation?

[Klaynos]

Does charge effect hawking radiation?

 

I honestly don't know the answer to that one...

 

But a comment I would like to make is how could this EVER be cheaper than creating it the way we do now on earth?

 

You'd ahve to go there, devise some method to stop anything other than protons going in and then some method for harnessing the positrons coming out.... and then confine and transport them...

[Mr Skeptic]

Ideally, you would want to make your own black hole, so that it would be small enough to have more Hawking radiation. That could be done with a large dense ball, or a very high energy collision. I'd imagine the black hole would eventually have to shed its charge, as eventually the electric field on it would overcome the gravitational field if it did not lose charge as it lost mass.

 

And, of course, the bigger reason you would want a tame black hole is so you can harness its Hawking radiation for power, as it would be much more efficient than say a fusion reaction and is not at all particular as to what fuel it burns. If it could produce antimatter as well, it might be worth doing just for that.

[Klaynos]

The blackholes we think we might make at the moment evaporate very quickly, shorter than fempto seconds, this is VERY energy intencive. If the bh lasted longer how would we possibly contain it?

 

Where do you think the energy to create hawking radiation comes from? It's not magical the energy comes purely from the massenergy that formed the original blackhole. If you input 10MeV of massenergy to create a blackhole the most hawking radiation you could ever get out of it is 10MeV. But the radiation would form (at least in part) massive particles from which you could not harness their full mass energy. I fail to see how this could EVER be more efficient than a fusion reactor. Or how this could be better than the current methods for creating anti-matter.

[Mr Skeptic]

Small black holes evaporate because they emit more massenergy than they take in. Most black holes are large, and for now they take in more energy in the form of cosmic background radiation, than they emit as Hawking radiation. They're too bulky and unenergetic to be of much use. But the small ones emit more Hawking radiation than they take in, making them evaporate. All you need to do to prevent it from evaporating is to toss in more matter (or energy). It doesn't matter what you toss in, you can toss in iron that would be worthless for fission or fusion, and it will add to the black hole's mass. Then it converts to energy as the black hole evaporates. For the theorized black holes that might be made in a particle collider, it may prove difficult to throw in even a single atom before it evaporates, but if it were a little bigger, that would not be a problem.

 

It would be more efficient than fusion, because it would use 100% of the mass, not a tiny fraction like with fission or fusion. It would be better than the current methods of creating antimatter (if it even works), because it would be about 100% efficient, if you consider that the remainder of the mass used would be converted into energy, rather than having to use energy to create the antimatter.

[Klaynos]

Right, you've got a bh that is massive enough to not evaporate, how do you stop it swallowing up the earth?

 

But it wouldn't use 100% of the mass because hawking radiation can contain massive particles, you claim this yourself because you say it can give off antimatter...

 

And it wouldn't be 100% efficient because you have to put energy in to create the bh... ignoring confinement etc...

[Mr Skeptic]

Right, you've got a bh that is massive enough to not evaporate, how do you stop it swallowing up the earth?

 

Ideally, by keeping it way the hell away from earth, using momentum from the particles fed to it, or electromagnetically levitating the charged black hole.

 

But it wouldn't use 100% of the mass because hawking radiation can contain massive particles, you claim this yourself because you say it can give off antimatter...

 

I'm actually asking if that would be possible. I don't know for sure that black holes actually can convert matter into antimatter; I'm just guessing it would do that because I think it would eventually have to loose charge to keep evaporating. In any case, I don't think Hawking radiation has even been confirmed or if it is still hypothetical.

 

And keep in mind that when I said it would be about 100% efficient, I'm comparing it to fission and fusion which are about 0.5% or less efficient in terms of matter to energy conversion. If the black hole emitted matter that you don't want, you can just toss it back in.

 

And it wouldn't be 100% efficient because you have to put energy in to create the bh... ignoring confinement etc...

 

The confinement should be easy energy-wise, especially if the black hole is charged; even arbitrarily small using electrostatics. The energy to create the thing might be enormous, but so long as you don't let it evaporate, the black hole will last as long as you feed it, without wear and tear. So just keep it around long enough and the energy to create the black hole will become negligible.

 

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Did I put this in the wrong place? Is Klaynos the only one reading Modern and Theoretical physics?

[uncool]

Actually, what does happen when you throw a charged particle into a black hole? Doesn't the black hole basically "swallow up" the charge, because the electrical force works through photons?

 

Shouldn't it also do that for gravitons, if they exist? As in, wouldn't this be a proof that gravity is a change in spacetime rather than by particles?

=Uncool-

[Klaynos]

Ideally, by keeping it way the hell away from earth, using momentum from the particles fed to it, or electromagnetically levitating the charged black hole.

 

This would take massive amounts of energy, making it a bad idea again, better to do stuff on earth, we have enough problems just landing things on mars...

 

I'm actually asking if that would be possible. I don't know for sure that black holes actually can convert matter into antimatter; I'm just guessing it would do that because I think it would eventually have to loose charge to keep evaporating. In any case, I don't think Hawking radiation has even been confirmed or if it is still hypothetical.

 

From my understanding there is an equal probability of getting matter and antimatter from hawking radiation.

 

As for evidence there is no direct experimental evidence according to:

 

http://en.wikipedia.org/wiki/Hawking_radiation#Experimental_observation_of_the_Hawking_radiation

 

But I know I read the other day of a light 'event horizon' which should allow for this to be investigated... It was in a recent new scientist...

 

And keep in mind that when I said it would be about 100% efficient, I'm comparing it to fission and fusion which are about 0.5% or less efficient in terms of matter to energy conversion. If the black hole emitted matter that you don't want, you can just toss it back in.

 

Urmmm ok, this is a bit unclear to me as 100% efficient means well 100% efficient, it's like saying 1kg of lead, but meaning only a few grams of it...

 

If you "toss it back in" you'd have to decelerate it then accelerate it towards the black hole again, taking energy... This would be lossy even if you tried to harness the deceleration energy.

 

The confinement should be easy energy-wise, especially if the black hole is charged; even arbitrarily small using electrostatics. The energy to create the thing might be enormous, but so long as you don't let it evaporate, the black hole will last as long as you feed it, without wear and tear. So just keep it around long enough and the energy to create the black hole will become negligible.

 

I somehow doubt you can do it using electrostatics, because as uncool suggests the photons telling the rest of the universe that the bh is charged can't escape the bh... this leads us onto the question of, is charge conserved for blackholes?

 

You're right about the creation energy becoming negligable but you've got to maintain it as well... and as you suggest putting it far away from the earth this would also use ALOT of energy... taking all of this into account I somehow feel earth based fusion would be better...

 

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Did I put this in the wrong place? Is Klaynos the only one reading Modern and Theoretical physics?

 

I'd probably say it should go into speculations but *shrug* Sometimes only a few people reply to threads...

 

Actually, what does happen when you throw a charged particle into a black hole? Doesn't the black hole basically "swallow up" the charge, because the electrical force works through photons?

 

Shouldn't it also do that for gravitons, if they exist? As in, wouldn't this be a proof that gravity is a change in spacetime rather than by particles?

=Uncool-

 

The first bit I mention above....

 

The second bit, as I understand it given comments in other threads by people I trust, gravitons would interact very very weakly with other gravitons, in a similar way to photons interacting very weakly with other photons, so the problem of gravitons escaping bh's is non-existent.

[uncool]

Hrm...gravitons interact weakly with other gravitons? Because I'd think that would falsify General Relativity in a way - you would be able to distinguish between acceleration and gravity simply by watching the effect on gravitons, wouldn't you?

=Uncool-

[Klaynos]

Hrm...gravitons interact weakly with other gravitons? Because I'd think that would falsify General Relativity in a way - you would be able to distinguish between acceleration and gravity simply by watching the effect on gravitons, wouldn't you?

=Uncool-

 

My knowledge of this is flaky, but neither quantum mechanics or GR are complete, and I know there are issues between them when to comes to the graviton and gravity, this might be one of them...