Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Dave Fangrow on 11/11/2009 09:30:02
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Dave asked the Naked Scientists:
My rudimentary understanding of quantum mechanics suggests “quantum foam” is happening all the time everywhere, even in the vacuum of space where particle / anti-particle pairs are created and annihilated. I also understand that this foamy nature of our universe is the mechanism behind Bekenstein-Hawking radiation when it happens at the event horizon of a black hole.
My question is; if one of the virtual particles is released and one is
sucked into the black hole why would this be considered ‘evaporation’ of the black hole? Were the virtual particles definitely created from mass of the black hole and if so how do we know this and where does the mass/energy come from when it happens in a vacuum?
If one of the particles was added to the black hole why wouldn’t it be accreting rather than evaporating?!?
Dave
What do you think?
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Hmm... I don't know the answer to this but it seems to me that the consequence of virtual particles associated with non-BH masses appearing at the EH would be for the BH to acquire the particle, as you suggest, and for the non-BH mass to evaporate as a consequence.
Furthermore, the rate at which a BH is supposed to evaporate is linked to its temperature, which is in turn related to its size; the larger the BH, the colder it is (which is why the tiny BHs that might be created by the LHC are expected to evaporate instantly, as being created from just two sub-atomic particles they'll be just about as small, and consequently as hot, as it's possible to get).
In view then, of the number of super-massive and therefore very cold black holes in the universe, it would seem likely then that many more virtual particle pairs should be created by the relatively warm non-BH mass than created by the BH's themselves.
I suspect that although the virtual pairs can appear anywhere in the universe, they're more probable to appear closer to their 'parent' mass rather than further away from it i.e. the distance from their parent is down to probability and is not entirely random.
Some of the other folk here are pretty good on QM, so hopefully one of them has the answer.
An interesting question.
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My question is; if one of the virtual particles is released and one is
sucked into the black hole why would this be considered ‘evaporation’ of the black hole? Were the virtual particles definitely created from mass of the black hole and if so how do we know this and where does the mass/energy come from when it happens in a vacuum?
These virtual particles are slated to annihilate each other, which is why they are said to be virtual. This creation and annihilation results in the conservation of energy in the surrounding space. In Hawking radiation, one of the particles falls into the black hole and one streams away from the black hole. The particle that falls into the black hole annihilates particles inside the event horizon. In the net, however, the particles streaming away are carrying away half of the energy from a region that overlaps the event horizon.
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The Naked Scientists asked the Naked Scientists:
My rudimentary understanding of quantum mechanics suggests “quantum foam” is happening all the time everywhere, even in the vacuum of space where particle / anti-particle pairs are created and annihilated. I also understand that this foamy nature of our universe is the mechanism behind Bekenstein-Hawking radiation when it happens at the event horizon of a black hole.
My question is; if one of the virtual particles is released and one is
sucked into the black hole why would this be considered ‘evaporation’ of the black hole? Were the virtual particles definitely created from mass of the black hole and if so how do we know this and where does the mass/energy come from when it happens in a vacuum?
If one of the particles was added to the black hole why wouldn’t it be accreting rather than evaporating?!?
Dave
What do you think?
Because particles consumed by the black hole is not a loss in information, and are tunneled back into the vacuum. It's an evaporation because black holes have a temperature. The larger the temperature, the faster the radiative evaporation.
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Keep in mind that the quantum foam speculation has no experimental verification. I think it was John Wheeler who first suggested it. The notion of a quantum foam does not have a role to play in any major theory. The idea that virtual particles can pop into and out of existence with impunity so long as they don't exist for a time great enough to be detected, is another of Quantum Theory's collisions with philosophical reason.
The notion that energy which constitutes the totality of a particle is a property that particle and the particle can rid itself of that energy and continue to exist is preposterous. When such a particle rids itself of its energy by sending it off into space as radiation, that particle can no longer exist. No experiment has ever found a remnant piece of any kind of real thing after such an event.
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The notion that energy which constitutes the totality of a particle is a property that particle and the particle can rid itself of that energy and continue to exist is preposterous. When such a particle rids itself of its energy by sending it off into space as radiation, that particle can no longer exist.
This is not how Hawking radiation works. The energy comes from a region of space and this energy is carried off in the form of a particle. The particle does not rid itself of energy, the region of space rids itself of energy via the particle.