Hawking radiation

Discussion in 'Physics & Math' started by hardalee, Sep 16, 2015.

  1. Q-reeus Banned Valued Senior Member

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    And in turn thanks tashja for that well balanced and positive message - refreshingly entirely free of the invective and bluster others seem wedded to.

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    As per an earlier post, I could have kept it going by pressing one or more of the 3 Profs with further probing questions - especially trying to tie down the elusive nature of the assumed physically real -ve energy quanta. Which must according to HR models be 'physically there' in precisely the same sense as the predicted +ve quanta HR received externally are 'there'. And whether modelling of such is in terms of particle or field is unimportant. Similarly for trying to fit it all into the perspective of a near-horizon observer. Any final 'accounting balance' must be able to be performed from the coordinate perspective of a distant observer. Only Prof. Helfer acknowledged there was a problem with all that. Anyway one gets to be able to predict the direction kicking the can further along would all take - going from courteous to curt - at best.

    In a way it was stupid of me to participate at all, given my overall position as per 2nd para in #135. Sometimes the temptation gets too much.

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    And yes I liked at least the spirit of much of RJB's postings, but haven't seen him around for quite some time. Wouldn't blame him for having gotten jack of SF and just moved on to more pleasant pastures!
     
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  3. Farsight

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    It's a fairy tale. Virtual particles are field quanta, particle pairs do not pop into existence, there are no negative-energy-particles. But what there is, is time dilation, in spades. Only Hawking radiation is seemingly immune to general relativity.
     
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  5. Daecon Kiwi fruit Valued Senior Member

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    And why do you think that?
     
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  7. John Connellan Valued Senior Member

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    Isn't Hawking radiation a consequence of the application of both QM and relativity?
     
  8. Farsight

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    Daecon : I think that because virtual particles are virtual. They aren't real particles. People think they're short-lived real particles that pop into existence like magic, then obligingly pop out of existence liek magic. It isn't true. They are instead field quanta. They are abstract mathmatical "chunks of field". When an electron and a proton attract one another they "exchange field" such that the hydrogen atom has very little in the way of a field. But they weren't actually throwing photons back and forth. Hydrogen atoms don't twinkle. Note though that vacuum fluctations are rela, but they aren't the same thing as virtual particles. Instead they're the electromagnetic equivalent of the little ripples on the surface of the sea.

    John: no, it isn't. Hawking radiation totally ignores general relativity. See Wikipedia where you can read that at the event horizon the coordinate speed of light is zero. Hawking radiation occurs at the event horizon. So the coordinate speed of Hawking radiation, the speed at which it emanates from the black hole, is zero too. Black holes are black because the coordinate speed of light is zero at the event horizon. See the second paragraph here. Einstein said speed of light rather than coordinate speed of light, but the meaning is clear enough. See this Baez article for more.
     
  9. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    it's usually refereed to as energy phasing.

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    shakes head.
     
  10. John Connellan Valued Senior Member

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  11. Farsight

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    Interesting maybe, but again Hawking ignores general relativity, which is one of the best-tested theories we've got. See Clifford M Will's paper for details: http://arxiv.org/abs/1403.7377. Meanwhile there's no evidence whatsoever for Hawking radiation, even though it's been kicking around for forty years. But we have some very good scientific evidence that black holes exist. There is something very small and very very massive at the centre of our galaxy. Stars move round it:

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    To all extents and purposes, it is a black hole. And if black holes exist, event horizons exist. The event horizon is a place where the speed of light is zero. If it wasn't, black holes wouldn't be black. Or small and massive. Perhaps the point to bear in mind is that Hawking has never ever been associated with any physics that has ever been proven to be correct. See this physicsworld article for a hint of what people think of him in the physics community.
     
  12. paddoboy Valued Senior Member

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    Hawking radiation is a quantum effect, and as such it's existence depends on particle pair creation that is generally accepted.
    Most of what is claimed about quantum theory is just that.
    http://srikant.org/core/node12.html
    BH's are a prediction of GR.
    In effect then Hawking radiation and BH's are a sort of TOE, something which our questionable friend Farsight says he had on his last foray into this forum.

    On the sensationalistic headlines re Hawking and no BH's

    http://www.pbs.org/newshour/updates/hawking-meant-black-holes/
    “There is no escape from a black hole in classical theory, but quantum theory enables energy and information to escape.”
     
  13. paddoboy Valued Senior Member

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    The speed of light is always "c" from within one's own FoR...From an external frame, gravitational time dilation comes into effect
    From this same outside FoR any light approaching the EH of a BH will gradually be further and further redshifted until faded from view.
    Light at the EH within its own frame will cross the EH, unless emitted directly radially away, when in that case it will appear to hover just above the EH, never seccumbing and never getting away.


    That is a blatant lie Farsight and you know it. But irrespective, please inform this forum of what you have achieved in physics, other than getting yourself banned from other forums.
     
  14. brucep Valued Senior Member

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    It's strictly a quantum prediction. Prior to the discovery that relates black hole physics to thermodynamics and the subsequent Hawking prediction, and Unruh prediction, folks actually believed that the black hole had to be the classical object GR predicts. These were really important predictions on the path to a quantum theory of gravity. But yes it is a marriage of GR and QM for this case and I believe this marriage, whatever that means, is present in the original inflation idea by Alan Guth and Andrie Linde.
     
    Last edited: Oct 13, 2015
  15. Schmelzer Valued Senior Member

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    To all extends, if GR is true, or, even more, if the spacetime interpretation of GR is true. There exist other theories of gravity, in particular Logunov's RTG, but similarly also my ether theory of gravity, which make similar predictions about the existence of "very small and very very massive" objects which, for all observable effects, look like black holes.

    And even if we change only the interpretation of GR toward an ether interpretation, with harmonic coordinates as the preferred coordinates, it does not follow that event horizons exist.
     
  16. Schmelzer Valued Senior Member

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    No, it does not depend on such an animal as particle pair creation. Only popular explanations use this, I haven't seen any serious scientific paper using them.

    Hawking radiation depends, in its standard presentation, on some assumption Unruh has correctly named absurd, and in Unruh's version on an inconsistent variant of an ether-theoretical analogy. That it is generally accepted is a bad sign in regard of the scientific character of the actual mainstream, but not really a surprise given the sociological (instead of physical) success of string theory.
     
  17. paddoboy Valued Senior Member

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    Hawking radiation as detailed by our professional replies is and can be interpreted by particle pair creation, despite your objections.
     
  18. Schmelzer Valued Senior Member

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    I would not recommend you to use the combination "our professional".

    But, in fact, it cannot. Because it is related with a modification of the very notion of a particle. Roughly, you have the energy (defined by the Hamilton operator) of a field. And this energy operator has, BTW in some approximation only, eigenvalues which remember those of a lot of particles/antiparticles flying around. With such an energy operator, you can define the creation and annihilation of particle/antiparticle pairs. And whenever there is an interaction between particles - which is what makes the particle picture only an approximation - you need such operators.

    What happens in Hawking radiation and related questions is that the energy operator itself changes. With another energy operator, you obtain another definition of what is the minimal energy state, which is named "vacuum", as well as the state which defines, say, what is a single particle flying with some momentum.

    So, there is no "creation of particles", but, instead, a change in the very definition of what is a particle. The former lowest energy state, named vacuum, is no longer the lowest energy state, thus, no longer named vacuum. But it is the same state, nothing has changed in the state itself, it is only the energy operator which assigns this state a different energy.
     
  19. paddoboy Valued Senior Member

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    I'm not talking about you, I'm speaking of the professional replies we have had as obtained by tashja.
     
  20. Schmelzer Valued Senior Member

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    I haven't seen there anything which contradicts my objections. Else, I would have made a reply.
     
  21. Farsight

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    But Schmelzer, GR is an ether theory of gravity. See the Einstein digital papers.

    I think it does. But not point singularities.
     
  22. paddoboy Valued Senior Member

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    Probably because they were not aware of your objections, and/or see them as rather contrived.
     
  23. brucep Valued Senior Member

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    The Hawking radiation totally ignores GR. LOL. That's even dumber than usual from you. GR doesn't have anything to say about quantum effects since GR isn't a quantum theory. Your lack of scholarship is monumental.
     

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