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Offline LeeE

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Can Black Holes initiate matter creation?
« on: 06/08/2008 19:26:24 »
It seems to me that a photon intersecting the event horizon of a black hole at a perfect tangent should go into orbit around it, at the radius of the event horizon.  If there should happen to be two suitable photons in such orbits, and they eventually collide, it could result in the creation of a matter/anti-matter pair where, unless the two particles were perfectly aligned along the event horizon, one would fall into the BH while the other could escape it.

At first thought, it might seem that the number of photons hitting the event horizon at a perfect tangent would be vanishingly small but if you think of the photons as a wave front it then seems inevitable.  Every wave front that passes over a BH should result in a 'ring' of photons going in to orbit around it (or alternatively, at least one photon being captured in orbit).

As the BH is floating in space, and surrounded by stars, it therefore seems that it should have quite a lot of photons orbiting it, in it's event horizon, and in view of this, matter/anti-matter producing collisions should be quite common.

If we then say that the BH has a charge, it seems to me that if the particle (of the pair) that is created outside the event horizon has the opposite charge to the BH, it'll be even more likely to escape.  If this process actually occurs, a side effect would be to reduce the charge of the BH.

There's also the issue of time dilation at the event horizon and how this might affect the energy of the photons, but I haven't thought about that very much yet.


 

Offline LeeE

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Can Black Holes initiate matter creation?
« Reply #1 on: 08/08/2008 00:09:08 »
Aw come on folks - does any of this seem plausible?
 

Offline JP

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« Reply #2 on: 08/08/2008 04:09:16 »
I'm not sure how this works with photons coming in from the outside, but this sounds similar to Hawking radiation, where the black hole loses mass by sucking in only 1/2 of a particle/antiparticle pair, while the other particle escapes.  The difference here is that you have energy being injected to create the particle/antiparticle, where Hawking radiation is based on virtual particles created from the vacuum. 

I'm not quite sure if I buy that the opposite-charge to the black hole will get sucked in.  Since electromagnetism can't escape a black hole (it sucks light back in), electromagnetic forces shouldn't be able to pull things into a black hole from outside.
 

Offline DoctorBeaver

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Can Black Holes initiate matter creation?
« Reply #3 on: 08/08/2008 09:27:19 »
I agree with jpetrucelli (for what little my agreement is worth :( ). As EM cannot escape the black hole, how can it attract an oppositely-charged particle from outside? I'd have thought that the probablitity is that you would get equal amounts of positively & negatively charged particles being sucked in, thus maintaining the BH's overall charge.
 

Offline graham.d

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Can Black Holes initiate matter creation?
« Reply #4 on: 08/08/2008 10:44:02 »
The Event Horizon of a BH is not a tangible surface. It is a surface defined such that the energy required to move from that surface to infinity is infinite. If you approach a black hole this surface shrinks, and crossing the EH (as viewed from a long way off) could occur without you being aware of it. There would be visual spacial distortions and extreme tidal forces but nothing specific to the EH itself.

The idea of a photon approaching the EH needs a clearer definition; for instance, as seen by a distant observer. In this case I don't believe it is possible to have a particle (at least a classical particle) approach such a surface (as seen from said distant observer) exactly tangentially unless emitted from a source close to the EH. The particle would have a very high energy indeed at this point but I cannot think of any trajectory that could take such a particle exactly to this surface, as Lee alludes to. The idea that this very high enery particle may be a photon and then would behave differently because of considering it as a wave may have some validity, but I would guess this would also apply to particles with finite rest mass too, because they would have their probability amplitude waves giving uncertainty to their position and trajectory.

The matter - anti-matter creation is right. With all the high energy photons about you should get plenty of electron-positron pair creation. I think you are right that, over time, any charge on the BH will then be neutralised. I think this could happen because of spontaneous electron-hole pair creation too. This is interesting because this would mean, for a charged BH, a reduction in the total energy of the BH (wouldn't it?) and so its mass decreasing. This is not unlike Hawking radiation but of a different form. It begs the question of where the mass of a body is "contained" - is it within the body or in its gravitational field, or in both? For an electron it is certainly the case that its mass is considered to be partly within its electrical field.

BTW I don't think it is correct that because EM radiation cannot escape a BH that it cannot be charged and have an electric field. I think the mathematical arguments are rather complex but can be seen by analogy: a BH has a gravitational field but cannot produce Gravitational waves.

 

Offline LeeE

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Can Black Holes initiate matter creation?
« Reply #5 on: 09/08/2008 14:30:36 »
Thanks for the comments folks.  It seemed as though it might be plausible and I wanted to run it by some people who would have a clue.

I thought it was interesting that there might be another particle creation process going on, in addition to Hawking Radiation.  Presumably, if particles created by Hawking Radiation can escape the BH then particles created by photon collision could escape too.  I'm also wondering if particles created by photon collision could potentially be much more energetic than particles created by Hawking Radiation.

The main significance of referring to the Event Horizon is that I believe that it's the orbital radius where the orbital velocity is 'c', so any orbiting photons would have to be in that exact orbit, making collisions inevitable.  Particles with mass though, could have any orbit outside the EH.  As to the possibility of long-distance photons intersecting the EH radius at an exact tangent - if you consider photons from a star passing by the BH, some of them will fall into it and some will just be diverted, or lensed.  The possible range of paths therefore must include one that results in a perfect tangent intersection, or so it seems to me.

I wasn't sure about BH charges but apparently they are a valid property, and as they can't be detected from inside (in so far as any test results couldn't be communicated back to the outside) it seems that the charge must be detectable outside the BH.  I'm not at all sure how much repulsive effect the BH charge would have over similarly charged particles, but as before, if Hawking Radiation particles can escape a BH then a repulsive charge can only accelerate the escaping particles.  I'm not sure what the effect would be of reducing any charge on the BH - there does seem to be a potential energy aspect to it though, which is interesting (but then this process is about supplying external energy anyway).

Thanks again for your comments and thoughts.
 

Offline Alan McDougall

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Can Black Holes initiate matter creation?
« Reply #6 on: 09/08/2008 16:48:06 »
Well my take on this is that there is no such thing as creation. Everything that exists has always existed only changing form and state is an everlasting cycle
 

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Can Black Holes initiate matter creation?
« Reply #7 on: 09/08/2008 17:18:55 »
I think your understanding of the word 'creation' is at variance with that of the other people posting here.
 

Offline LeeE

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Can Black Holes initiate matter creation?
« Reply #8 on: 12/08/2008 00:05:43 »
After a bit more thought...

Arguments against:

Re the charge issue - I can't think of any mechanism whereby the charge of the BH could influence which one of the matter/anti-matter particle pair is created inside the EH and which one is created outside it, so the likelyhood of oppositely charged particles falling in to the BH is likely to be balanced by the number of similarly charged particles falling in to it.

Re photons being captured in an orbit where the orbital velocity is 'c' - this only works if the photon has a zero-sized cross-section, which then doesn't work with the inverse-square law (it's an area law), so if a photon has a non-zero sized cross-section, part of it must be inside the EH (if it is centered on the EH radius) and part must be outside.  Dunno what happens to photons straddling the EH - perhaps they have to split ???

However, there does still seem to be the possibility of matter/anti-matter pair creation due to lensing.  If one thinks of the double-slit experiment, the distance between the two slits isn't critical and this is analogous to photons being lensed around the periphery of the BH cross-section, so lensing still seems likely to result in photon collision.  Collisions closer to the BH should have more energy (due to time dilation effects), and therefore would be more likely to produce matter/anti-matter pairs, but as the photons focus further away from the BH they should lose energy.

Thanks again for the comments.
 

Offline graham.d

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Can Black Holes initiate matter creation?
« Reply #9 on: 12/08/2008 11:40:24 »
Lee, you did not address the issue I raised about what the EH is. It is not a tangible surface and its position (radius) depends from where it is viewed. The normal definition is as viewed from infinity (practically, a long way off). To a particle or photon (or observer) nearby, the EH will have a smaller radius and, when approached, will recede completely. You probably should just consider how a particle or photon would behave as viewed from infinity. The particle cannot have fallen from infinity. If it had then it would have infinite energy at the observed EH. This would be interesting as this particle would also then add an infinite mass to the BH. So assuming the accretion is from local sources, anything approaching the EH (even if some way off) will have insufficient energy to escape whatever the trajectory. If they get close they can only fall in. Anything else with similar energy that is to escape will have a hyperbolic trajectory some distance away from the EH.

I think that anything that could be in orbit at exactly the EH (as defined above) would have to have infinite energy.

I believe that your first assumption that a charged BH will gradually become neutral is a fair one. I don't think it needs any postulates about where the matter-anti-matter pair are created. It is sufficient to note that a charged BH will be more attractive to oppositely charged matter than to similarly charged matter. This would make a difference over sufficient time and the charge would eventually be neutralised.
 

Offline Alan McDougall

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« Reply #10 on: 12/08/2008 13:13:20 »
I do not think anything new is ever created out of nothing, Everything that exists has always existed, just changing form in the constant cyclic process of cosmic evolution.

Or everything in its fundamental essence is energy

Regards

Alan
 

Offline LeeE

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Can Black Holes initiate matter creation?
« Reply #11 on: 12/08/2008 13:17:43 »
Hi Graham.d

The main significance of referring to the Event Horizon is that I believe that it's the orbital radius where the orbital velocity is 'c'...

Perhaps I should not have referred to the Event Horizon at all and instead referred only to the orbital radius where the orbital velocity is 'c'.  It just seemed quicker and easier to say 'EH'.

I agree that to an object approaching it, the EH will appear to recede but is this not due to time dilation effects?  i.e. as the body drops down the gravitational gradient it's local rate of time slows, so it will seem to take longer to reach it.  There is a difference though, between particles with mass and massless particles falling into the BH (and I was only considering massless photons) - the particles with mass will accelerate but the zero mass particles won't(can't).  Instead, their frequency increases, so I would agree that if a photon could orbit a BH at the EH it's energy would indeed be infinite (infinite frequency in zero time, so the energy should be infinity^2  ;D).

Re the charge issue:  We have gravity playing off against opposing charges and although the EM force is much stronger than the Gravity force I wouldn't want to bet that the opposing charge force is stronger than the gravitational force in the case of BHs.
 

Offline LeeE

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Can Black Holes initiate matter creation?
« Reply #12 on: 12/08/2008 13:19:56 »
Alan - it's as though you're debating whether tea exists or not, while we're discussing how to make it and whether we should put the milk in first.
 

Offline graham.d

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« Reply #13 on: 12/08/2008 13:44:47 »
Milk first, definately :-)

Lee, I think the issue about the EH is not just an observational one or to do with time dilation. Even classically the radius of an EH can be defined as the point at which you need infinite energy to escape to infinity. The radius to get to somewhere closer than infinity is a smaller radius.

I just had an interesting thought about this but have no time right now. Get back later.
 

Offline graham.d

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Can Black Holes initiate matter creation?
« Reply #14 on: 12/08/2008 15:22:30 »
I did not have time to consider this earlier, but it is an interesting thought experiment...

I was thinking about two cases: one where you were a long way from a BH where you could define and measure the EH and another where you were much closer to the BH so that the EH that you perceive would be smaller. With some initial vector you could, in both cases, plot a course which would allow you to free fall and get back to the same position. Neither case can involve crossing the position of the EH that you perceive from your initial position. By definition this would be impossible. However, it is possible that, from the nearer start position, that you could pass below the proper EH (as seen from infinity) but above the one viewed from your starting position. Such an elliptical orbit would be perfectly OK (as long as you did not hit anything). What is interesting is that it would mean that even from your starting position you do not have enough energy to escape to infinity. The energy you have is only the same energy that you would have when you passed below the proper EH so you cannot escape to infinity. So why is this the case when you start from a position well outside the proper EH.

I think the answer to this paradox may lie in the fact that the initial position is not a stable one unless from a position of orbit and therefore having considerable kinetic energy to start with. To fall towards the BH in an elliptical orbit you have to shed a lot of this kinetic energy; this would have to be enough to mean that you could no longer escape to infinity. What do you think?
 

Offline DoctorBeaver

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« Reply #15 on: 13/08/2008 10:19:06 »
Milk first, definately :-)


By God, you're a MIF (Milk In First). DeBrett's would have you ostracised if they found out!
 

Offline Alan McDougall

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« Reply #16 on: 13/08/2008 11:59:42 »
LeeE,




1)
Quote
Alan - it's as though you're debating whether tea exists or not, while we're discussing how to make it and whether we should put the milk in first.

2)
Quote
I thought it was interesting that there might be another particle creation process going on, in addition to Hawking Radiation.  Presumably, if particles created by Hawking Radiation can escape the BH then particles created by photon collision could escape too.  I'm also wondering if particles created by photon collision could potentially be much more energetic than particles created by Hawking Radiation

 1)No you don't understand where I am coming from in this debate. You cant make your particle hypothetical tea unless the energy that makes up tea exists in some other form before you attempt this combination on the fundamental scale.

2) In quote 2) you talk about particle creation when there is no such thing. Particles have always existed in some prior form and in the ultimate prime form "pure uncreated energy"

The colossal forces in a black hole of course combine fundamental particles into newer particle, just like you tea, made from tea, milk and sugar. These elements if you like exist before this combination, into your nice maelstroms of cosmic tea.

Therefore the term "created is not really true but there is nothing wrong with it in this debate. Everything is created from something else and at the end we have to abandon the term created, with EXISTED that is my point.

I think when we use the term "Created" we should acknowledge that we mean put together of formed. Existence is that which always was and uncreated prime something I call primorial energy

Regards

Alan

 

Offline graham.d

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Can Black Holes initiate matter creation?
« Reply #17 on: 13/08/2008 14:01:30 »
Quote
By God, you're a MIF (Milk In First). DeBrett's would have you ostracised if they found out!

I'm a scientist and engineer. It saves having to stir it!
 

Offline Alan McDougall

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« Reply #18 on: 13/08/2008 17:01:12 »
graham

Quote
I'm a scientist and engineer. It saves having to stir it!

And so am I.
 
 
 

Offline graham.d

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« Reply #19 on: 13/08/2008 17:05:26 »
And a MIF man too I trust?
 

Offline Alan McDougall

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« Reply #20 on: 13/08/2008 17:48:33 »
Graham

Quote
Milk first, definately :-)

A scientist and engineer that "definitely" can not spell!!
 

Offline LeeE

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« Reply #21 on: 13/08/2008 19:50:50 »
Hi Graham.d,

That's an interesting idea.  The problem I have with it is that the true radius of the EH is absolute and not dependent on the observer.

Also, I'm not sure that an observer sees the EH getting smaller or whether it just seems to be further away in relation to their locally perceived speed.  If it were to appear to get smaller as they approach it, it would eventually appear to have zero size and then any path not directly through it would miss it.

Perhaps we should go back to an observer directly approaching a BH - this observer would never actually experience reaching the EH because of the time dilation factor - the last instant before they crossed the EH would seem to take forever, but to a distant observer, they're irretrievably gone - do we agree on that?

Speaking of which, I have to scoot now too.  I'll check back in later though.
 

Offline syhprum

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« Reply #22 on: 13/08/2008 20:04:11 »
"Definitely" is definitely the most frequently misspelt word on message boards even those that have built in spell checkers
 

Offline LeeE

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Can Black Holes initiate matter creation?
« Reply #23 on: 15/08/2008 00:39:43 »
Comment overheard just before the Big Bang:  "Better late than never"

This [the elliptical orbit that dips below the EH as seen by a distant observer but not by the local observer, who sees themselves as remaining outside the EH] seems like a good paradox.  It hints towards an absolute space-time-frame, which can only be seen by an observer who is  infinitely far away, which is impossible - nice  ;D
 

Offline graham.d

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Can Black Holes initiate matter creation?
« Reply #24 on: 15/08/2008 13:37:38 »
I never spellcheck my posts and just write them straight in to the quick reply box. I definItely will get spellings wrong occasionally. I'm quite good by average science/engineering standards though :-)

Lee, thanks for taking the time to think about this. Interesting isn't it? The problem is I lack the knowledge (and the time) to do a proper mathematical treatment using General Relativity. There is definitely a limit as to how far you can understand these things by just reasoning.

I am not sure about whether time dilation plays a role or not here. If you take the fall from a large distance straight into a black hole then, as far as you are concerned, the black hole EH (that you observe) will get smaller as you get closer. Just before you get to the position where the theoretical EH would be (as viewed from infinity) the universe would seem a small place (in the direction of you travel) because of the Lorentz contraction. When you get to the theoretical EH the universe would have got to zero size in the direction of travel and the centre of the BH (a naked singularity??) and the EH are coincident. I suppose if the distance you fall into the BH from is not infinitely far off and/or you are not really in free fall to the BH because of all the other gravity fields around, your speed will not be so high as to Lorentz contract the universe and BH so much. Still, the perceived EH must always recede from you. I imagine that it is possible that the distance from the perceived EH to the singularity gets could converge to zero when you actually hit it. Not that this matters as the gravitational forces would have long since turned you into a pulp of fundamental particles long before.

There may be an issue though with how the mass of the BH increases with your relative velocity which may change this view and also solve the paradox. As you get close to the theoretical EH (in free fall from infinity OR IF IN ORBIT) the mass of the BH will rise as you perceive it because it is moving at great speed relative to you. This would mean that the EH would also not shrink in the way I suggested. What do you think?
 

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Can Black Holes initiate matter creation?
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