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Where Does The Hawking Radiation Go?

  1. Oct 30, 2006 #1
    When a black hole evaporates it gives off Hawking Radiation. Where does the Hawking Radiation? Is it recycled into dark matter or new stars or what? Since mass and energy cannot be destroyed, it goes somewhere in the universe, correct?
     
  2. jcsd
  3. Oct 30, 2006 #2

    LURCH

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    Correct. In fact, it goes everywhere. Just like radiation emmitted by a star, it travels outward radially (as radiation is wont to do) in all directions, becoming weaker by the square of its distance from origin, and most of it becomes part of the non-zero temperature of space.
     
  4. Oct 30, 2006 #3
    Considering that the escape velocity from within the schwarzchild radius is greater than the speed of light, how could any matter or energy possibly escape from within a black hole of any type? Would this not contradict the theory of relativity?
     
  5. Oct 30, 2006 #4

    LURCH

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    That was the entire breakthrough of Hawking Radiation. Mass escapes the BH without ever travelling >c.
     
  6. Nov 3, 2006 #5
    its due to virtual particles. you have a virtual photon pair come into existence with one photon on one side of the event horizon and the other on the ...well other. this means one falls in and one 'evaporates' as if the black hole were a black body.
     
  7. Nov 4, 2006 #6

    Labguy

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    That was already answered this week over here.
     
  8. Nov 7, 2006 #7
    Hi Silverlabguy,

    The simple answer to your question is "nowhere". It remains in Hawking's head. Hawking radiation is a purely conceptual construct, and has no empirical foundation whatsoever.

    Kind regards
    Hilton Ratcliffe
    Astronomical Society of Southern Africa.
     
  9. Nov 7, 2006 #8
    Oops! Sorry, my post should have been addressed to Silverbackman. Apologies.
    Hilton
     
  10. Nov 7, 2006 #9

    Chronos

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    Hawking radiation is too faint to detect [a scant few high energy photons are enough to balance the scales] until a black hole shrinks far below a solar mass - unless, as Hawking suggested, there are a fair abundance of sub solar mass black holes [primordial black holes] cavorting around the universe. The universe is otherwise not nearly old enough for their presence to be noticeable.
     
  11. Nov 7, 2006 #10

    LURCH

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    As indeed are black holes themselves.
     
  12. Nov 7, 2006 #11

    Hurkyl

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    TMK, there is plenty of empirical foundation for them. :confused:
     
  13. Nov 7, 2006 #12
    Hi Hurkyl,
    Thank you for your comment.
    There is no empirical evidence for black holes. They have not been observed, not even by eclipsing. They are inferred from concentrations of hyper-gravity, but that is model-dependant filtering of observational data. The notion of black holes can be sustained only by mathematical sophistry. We do not need black holes to explain anything we see. Gravitational concentrations can be adequately explained by other means, notably compact objects and electro-magnetic fields. As for singularities, they are physically impossible for many reasons, not the least of which is that they require divide-by-zero. To entertain divide-by-zero, we have to invoke universal geometry other than the one we observe. This is clearly not empirical science.
    Please see my post in the "thoughts on black holes" thread elsewhere in PF for a quotation of Einstein's opinion on singularities in terms of GR's field equations.
    regards
    Hilton
     
  14. Nov 8, 2006 #13

    Garth

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    Hilton, It might be argued there is plenty of evidence for BHs: viz: the energy output of quasars, the mass concentrations at the centre of most galaxies, the X-ray emissions of Cygnus-X1 and other X-ray binaries. The Cygnus-X1 collapsed object of 20–35 solar masses has been well studied critically and it is concluded that a BH seems to be the only possibility.

    All you need for a BH is a mass concentration of
    [tex]\frac{2GM}{rc^2} = 1[/tex]
    which can be quite dispersed for a mass of the order of a globular cluster.

    What happens at the core is another matter. Although you may be correct in objecting to "divide-by-zero", it does depend on how you take the limit. Remember ordinary differentiation ends up with "divide-by-zero" in the limit [itex]\delta x \rightarrow 0[/itex], but there is no problem if the limit is taken correctly.

    On the other hand, if the objection is a finite mass being concentrated into a zero volume, then we ask the question: "What prevents all objects from collapsing into zero volume?" and realise the answer is the internal nuclear and e-m forces that give the atom and its components structure. In a BH singularity gravity is seen to overwhelm all such other forces.

    Do you propose a fifth force able to withstand such a crushing gravitational field?

    Garth
     
    Last edited: Nov 8, 2006
  15. Nov 8, 2006 #14

    Chronos

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    Any mass possessing object can condense to its Swarzschild radius without reaching zero volume. There is no known force, as Garth noted, sufficiently strong, in theory, to prevent such an object from shrinking to zero volume. Singularities exist in the math, but this does not assure their physical reality. There may indeed be yet unknown forces that prohibit the existence of absolute singularities. I favor the Planck density as a candidate limit on matter density.
     
  16. Nov 8, 2006 #15

    Labguy

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    I agree with that 100% and have never "bought" the idea of a zero size or infinite density for a so-called singularity.

    I think the Planck length or Planck density would be a minimum for any amount of collapsed matter, but actually think that any "singularity" would be even larger than that. I would also rule out a ring singularity of zero "thickness". But, zero size is part of the definition of singularity, so perhaps we simply need a new name or description of such extremely condensed matter.

    But, as others have noted, there is a fair bit of evidence for objects with R<=2Gm/c2. So, unless we require the term and existence of a zero size and infinite density for there even to be a Black Hole, we would need a new term for those collapsed concentrations of matter too..(?) It gets too mixed up with semantics, but I can (and do) still believe there are Black Holes that happen to have a matter concentration with a finite size and large, but not infinite, density. Everyone has to keep in mind that the matter/mass is still there in some form and that it doesn't just "blink" out of existence. It "has to be there" or we wouldn't be able to measure its effect (mostly gravity) on outside objects.

    Chronos: Was your comment also meaning that there are no compressed objects with R<=2Gm/c2, therefore no Black Holes, or just that there are no infinite densities??
     
  17. Nov 8, 2006 #16
    Thank you Garth and Chronos for your comments.
    All the evidence cited is inferred evidence, and does not connect unambiguously to any empirical model. We have no tested, reliable way to measure galaxy masses, and the results we have are anomalous, hence MOND and dark matter. In my opinion, any attempt to measure and extrapolate from rotation of astrophysical objects without taking into account the vast galactic electrical fields will give significantly skewed results. Quasars are highly controversial objects, and most standard descriptions simply ignore Arp's meticulously recorded observations. X- and gamma ray emissions can be explained in a variety of ways without invoking black holes. Attempting to explain Cygnus-X1 using as "the only possibilty" a model which is itself physically impossible is not good science. It would be better and more productive in the long run to simply admit that we do not know. Apart from a purely visceral objection to material objects having zero volume (quite impossible in my judgement), it appears unlikely that gravitation could cause the type or degree of collapse you refer to. Firstly, electro-magnetic force is ~10^38 times stronger than gravitation. Coulomb repulsion alone could easily resist sub-atomic gravitational collapse. It's a loop: Gravitation is not strong to compress matter enough so that gravitation becomes strong enough...etc. Electrophysicists Don Scott and Wal Thornhill argue that when the sums are done, even neutron stars are not possible in reality. Secondly, Oliver Manuel at the University of Missouri has shown convincingly that neutrons repel each other. This further resists gravitational compression, and supplies an energy source for compact objects. (I can supply references if you require them).
    Garth, you raise a very interesting point regarding differentiation. The calculus was invented as a very neccessary and useful tool to cope with extremes of scale. Differentiation and integration allow us to effectively ignore infinitesimals. Something that tends to zero is not really zero. A pseudo-tensor is not a tensor. Divide-by-zero is admissable only if we approximate zero. This may be splitting hairs, but since we are arguing about mathematical approximations of reality, we need to be aware that the calculus is to some degree a convenience. Rather than let this discussion become an excercise in semantics and an endless exchange of definitions, I would prefer to deal with things that can be observed, or directly related to an observation.
    That said, I really do appreciate and respect your well-considered opinions.
    Best regards
    Hilton
     
  18. Nov 8, 2006 #17

    Labguy

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    I would like the reference on that one, please. It could let me understand what type of object could rotate 716 times per second.
    http://www.nrao.edu/pr/2006/mspulsar/
     
  19. Nov 8, 2006 #18

    Garth

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    Hilton let me make myself clear.

    I think there are two separate but connected issues here, these are the question of the existence of Black Holes and the question of the existence of singularities at the centre of BHs.

    Black holes are not neccesarily artifacts of GR: Black Holes
    It is not unreasonable to postulate that such massive and condensed objects do exist in our universe, and the X-ray emission expected from matter falling into such has been observed.

    Of course what happens at the centre - the singularity - has never been and probably can never be observed. Whether the Planck length is the limit or not is a matter for a future quantum gravity theory to resolve.

    Garth
     
    Last edited: Nov 8, 2006
  20. Nov 8, 2006 #19

    Labguy

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    Do you have the reference, ..please ??..:confused: ..:confused:
     
  21. Nov 9, 2006 #20
    Hi Labguy and Garth,

    Labguy, the beauty is that that this model does not propose a "lighthouse effect" and therefore does not require such unlikely rotational rates. Have a look at:
    Donald E. Scott Electro-Magnetic Fields and Plasma in the Cosmos in E. J. Lerner and J. B. Almeida, Eds. 1st Crisis in Cosmology Conference, CCC-1 (American Institute of Physics Conference Proceedings Vol. 822 2006).

    and www.electric.cosmos.org

    wal Thornhill: www.holoscience.com

    Thank you for that historical perspective, Garth. What I meant was that the formalism on which standard black hole theory is based was derived from the GR solutions of Schwarzschild, communicated by letter to Einstein from the Russian front in 1916 some weeks before his death.
    Regards
    Hilton
     
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