Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Andrew Pestell on 17/01/2009 23:44:47
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Andrew Pestell asked the Naked Scientists:
Q1: If you had a X kg of matter such that adding 1 kg of matter would cause it to make a black hole and you added the 1 kg of matter to form a black hole, waited a while, then added 2 kg of anti matter (opposite spin) so that it anihilates with 2kg of matter giving a total of X-1 kg of matter (x 1 -2) what would happen?
Q2: Would an anti matter black hole bend space the other way to a matter black hole?
What do you think?
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Q1 Nothing much because the event horizon had already formed and what was inside had already collpsed If there was an effective reduction in gravitational mass the black hole might get a bit smaller but that's about all.
Q2 No the gravitational effects of matter and antimatter are identical.
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"No the gravitational effects of matter and antimatter are identical"
Is this confirmed from experiment or is it from theoretical considerations ?
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"No the gravitational effects of matter and antimatter are identical"
Is this confirmed from experiment or is it from theoretical considerations ?
Its probably just theory; but there is nothing to suggest anti-matter would behave differently toward gravity. It is simply matter with a reverse electric charge.
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Theoretical considerations imply that both matter and antimatter are gravitationally identical
I believe it to be also true from measurements because in high energy storage rings of electrons and positrons gravitational effects have to be allowed for and if they were different the beams would diverge. However low temperature experiments with antimatter are also being planned to try to confirm this.
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Thankyou Soul Surfer.
From your answer to my first question that would mean that a black hole could be formed from less than the limitinng mass X in effect then ? Also from discussion I've had in the past on the subject it has been suggested that the spin direction of the particles becomes important in this scenario (hence my opposite spin) despite the compression of the mass to an an infinite density dot or what ever. Any comments?
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"No the gravitational effects of matter and antimatter are identical"
Is this confirmed from experiment or is it from theoretical considerations ?
Many years ago, in the 90', there was some excitation in the physics community because of an alleged discovery of "antigravity" (also called "fifth force"), that is a difference in gravity between normal matter and antimatter. Some laboratories around the world tried to replicate the experiment, one of these was a laboratory of nuclear physics in Florence (I was studying there at the time) but they didn't find anything and the same in the other laboratories. If I remember correctly, they made measurements on a floating ball of nylon; another laboratory made measurements on a flow of antiprotons going up against the grav. field. They didn't find any difference with normal matter.
http://books.google.it/books?id=55KEjjGK3fgC&pg=PA263&lpg=PA263&dq=antiprotons+fifth+force+%22Bizzeti%22&source=bl&ots=Ipf9_NAaM6&sig=QyqLfbHM6Z57NZSOMuIoTgG9iTo&hl=it&sa=X&oi=book_result&resnum=1&ct=result#PPA264,M1
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A black hole can be formed from any mass of material greater than the plank mass to once the event horison has formed the loss of some mass would only cause the horizon to shrink a bit. The larger the mass the easier it is to form a black hole. It has been seriously suggested that the first large mass concentrations after the bib bang collapsed straight into black holes without forming stars and are currently the billion solar mass black holes at the middle of the largest elliptical galaxies.
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see http://www.newscientist.com/article/dn16204-does-antimatter-fall-up.html for a new experiment to test if gravity effects anti-matter the same way as matter.
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If the materiel that goes to form a black hole is compressed to an infinite density or more likely a quark soup is it meaningful to refer to it as either matter or antimatter ?
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First of all, what do you mean by 'antimatter'?
In physics 'antimatter' is something that exists "It’s now understood that all particles have an equivalent antimatter particle with opposite charge and quantum spin – although some are their own antiparticle." http://www.physics.org/article-questions.asp?id=105
Was that what you were thinking of? Then a 'black hole' will behave the same way, no 'matter' what it consists of as I see it. If you by it mean something 'taking out' something else without leaving a trace, no form of residual 'energy' released etc, then I don't know if such particles exist.
The simplest way to think of it is in the form of energy released, that 'energy' can 'bend SpaceTime' too if I understand it rightly. What we now would need to propose for it to be correct seems to be two kind of 'energies', one that act one way, the other opposite. Do that make sense to you?
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Hmm, rereading it I notice that the thread is quite old. Which makes my answer rather meaningless as the questioner surely must have moved on to greener pastures :)
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Consider that we had matter particles the size of the Planck mass. Two of these then combine to form a black hole. We would also have antimatter particles the size of the Planck mass. What if one of those entered the event horizon? Surely it would depend upon whether the particles were elementary or composite. Composites could form a confined plasma. If it is also a condensate the addition of the third particle would make no difference. For elementary particles something else must be the case.
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For elementary particles something else must be the case.
Two thoughts come to mind:
1. If the antimatter particle annihilates with one of the matter particles, the energy must still remain within the BH, so its matter/energy remains unchanged.
2. Since the BH "singularity" is shorthand for a situation about which we have no information, and in which, as far as we are aware, our current theories no longer apply; the best we can say is "dunno".