Hawking radiation

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

  1. paddoboy Valued Senior Member

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    And the psychoanalysis continues.

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    I follow many things, RU and RL are just two of those things. Concepts in physics and cosmology is another, and keeping fools honest on a science forum is another.
    And you certainly are unable to meet my challenge! If you did your collective ignorance of GR and 21st century cosmology would be dazzling to say the least.
    Calm down sonny boy!.....Of course this is a forum.....and as such discussions and debates take place, but near certainly no new revelation in cosmology or physics will ever be forthcoming.
    You see the true scientists [which you claim to be

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    ] are out there gathering the data, examining same and making observations...they have their heads down and their arses up, nose's to the grindstone.


    Yep there are forum rules, and those same rules would be applied to your conceited self.
    Again, I believe the god is rajesh, and others do also.
    And I do have evidence for that. The similarities are astounding.
    I would suggest though you grow up, and learn to take what you dish out and stop acting like a big baby.
    To be refuted by a lay person may be hard to swallow, but you have already had one anti GR thread shifted to the fringes in which I played a part, and that makes it even harder to swallow.
    http://www.sciforums.com/threads/fr...-is-bs-or-dont-just-trust-authorities.142870/

    And of course speaking of accusations......who could forget this.....

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    Last edited: Oct 2, 2015
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  3. paddoboy Valued Senior Member

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    Very short GRBs may be Hawking radiation source A particular group of gamma-ray bursts, those of very short duration, have characteristics that suggest they may be the signature of an evaporating primordial black hole – the Hawking radiation proposed by Stephen Hawking in 1974. Very short gamma-ray bursts (VSGRBs) last less than 0.1second and have been detected by several GRB instruments including the BATSE experiment on the Compton Gamma Ray Observatory, the KONUS experiment, and NASA’s Swift gamma-ray burst mission. The evaporation of primordial black holes was postulated as a possible high-energy source for GRBs as a whole, but these events do not in general fit the characteristics of such an event. Hawking, in collaboration with Bernard Carr, proposed that the evaporation of black holes left over from the early universe would produce a burst of energy; GRBs in general are too bright and too uniformly spread over the sky to have come from primordial black holes. Now David B Cline and colleagues from the University of California in Los Angeles argue that these VSGRBs are a distinct population that does fit the characteristics of primordial black hole evaporation, notably their anisotropic distribution in the sky and lack of significant afterglows. Cline presented these results to the GRB2010 meeting in November. http://www.physics.ucla.edu/hep/vsgrb/ vsgrb_ichep2010.pdf
     
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  5. paddoboy Valued Senior Member

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    Your comment re "clear language" is of course correct, and as you recognised in my tutorial and my use of the words, "approx" "around" and "about"
    Not sure though that I agree fully with what you have said above.
    What we do know about quantum theory is near all unobservable...we just are not as yet technologically advanced enough to observe at those levels.
    But again, as per our differences in the past, one can invoke some level of certainty on certain issues based on likelyhood and logic and acceptance within the scientific mainstream community.
    We also do not directly observe BH's, but the indirect evidence can only be attributed to such an entity.
    Virtual Particle pair creation is essential to our limited understand of quantum theory. If we doubt that, we may as well shelve all of quantum physics that we have learnt.
    My own opinion then is that Hawking Radiation, seems to be an extension of virtual particle pair creation....I see it as a legit scientific theory, though certainly not in the class of SR/GR theories.
    And isn't this what mainstream have accepted....Isn't it far more certain that Hawking Radiation is a real entity, based on what we already know, and certainly more likely the any other alternative that has been offered on this forum?
    And does not the virtual particle pair creation theory, mean that while virtual, they are not contained by the laws of physics such as "c"?
    The debate and some nonsense in this thread appears to simply be about what mainstream accept as likely and what is proposed by others that are not generally accepted and what I see as anti GR agendas anyway.
    Does science really need to directly observe something for it to be a scientific theory? I don't believe so.
     
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  7. Q-reeus Valued Senior Member

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    It disgusts me that a mathematical illiterate and not even half a trick pony like paddoboy can get away with continually spewing out the sort of s**t displayed in #61. Why the hell does admin mollycoddle such a cretan rather than life ban it?
    [I seem to recall recall someone else suggesting why - as a chronic obsessive/compulsive poster, that cretan boosts the stats for this site. A triumph of quantity over quality - and certainly over morality. Sigh.]
     
    Last edited: Oct 3, 2015
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  8. brucep Valued Senior Member

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    Read the one I posted for you. Specifically the discussion. Why should I provide you with another reference that you won't actually read?
    Oh well here is the William Unruh paper on the results of the analog experiment to measure Hawking radiation. It's always cool when the theorist participate in the experimental side of physics.
    http://arxiv.org/abs/1401.6612
    Circa 2014.
     
    Last edited: Oct 3, 2015
  9. tashja Registered Senior Member

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    Hey, guys

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    Hi, Q. I just saw your posts this morning, so I got in touch with Prof. Unruh to see if he can help us with it. Below is his reply:


     
  10. brucep Valued Senior Member

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    Since this thread is about Hawking Radiation it begs the question about analog experiments and confirmation of theoretical predictions. Several other key contributers along the path to Hawkings revelation. Such as Jacob Bekenstein. May he rest in peace.
     
  11. Daecon Kiwi fruit Valued Senior Member

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    What?

    Black bodies aren't black holes, but a black hole is a black body, according to the Wikipedia article on black-body radiation.
     
  12. brucep Valued Senior Member

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    For somebody who doesn't know much about this science you sure have a lot of irrelevant opinions.
     
  13. brucep Valued Senior Member

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    You and the wiki are correct. Hawking radiation radiates in the black body spectrum.
     
  14. Daecon Kiwi fruit Valued Senior Member

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    Would Hawking radiation have a temperature of about 2.7 Kelvin, the same as the cosmic microwave background?
     
  15. paddoboy Valued Senior Member

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    Your opinion is just that...your opinion....My opinion of you is to grow up, stop being so falsely indignant and utterly pretentious and you may get some respect.
    In the meantime have a disprin and a good lay down and take an anger management course.
    As long as I'm being criticised by nuts, I must be doing something right.

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    And just like your previous GR thread, you should be in the fringes. Take it easy my friend.
     
    Last edited: Oct 3, 2015
  16. paddoboy Valued Senior Member

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    Thanks once more for a grand effort tashja.

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  17. brucep Valued Senior Member

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    The Hawking temperature. This is derived from the Unruh temperature and is part of the text Exploring Black Holes by Edwin F. Taylor and John A. Wheeler.




    T_Unruh = h*g_conventional/4(pi)^2*k_Boltzmann*c [eq.1]
    g_conventional/c^2 = (M*c^2/r^2)(1-2M/r)^-1/2
    g_shell = g_conventional/c^2 = (M_meters*c^2/r^2)(1-2M/r)^-1/2 [eq.2]
    Substituting [eq.2] into [eq.1]
    T_Unruh = [h*M_meters*c] / [4pi^2*k_B*r^2 (1-2M/r)^1/2)]
    Let r > 2M the Schwarzschild event horizon. Account for the redshift measured from remote coordinates(1-2M/r)^1/2 / 1-2M/r)^1/2 =1

    T_Hawking=[h*c*M_meters/4pi^2*k_Boltz*4M_meters^2]
    T_Hawking = h*c/16pi^2*k_Boltz*M_meter

    The only variable is the mass expressed in meters. The larger the mass the smaller the Hawking temperature. For one solar mass it would be M_meter=1477 meter. For the solar mass that works to a prediction around .000000061787 Kelvin. So they are really cold generally. With a little algebra you could predict the mass where the Hawking is around the 2.7 K.
     
    Last edited: Oct 3, 2015
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  18. Daecon Kiwi fruit Valued Senior Member

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    Ah, I see. So supermassive black holes are supercold.
     
  19. Q-reeus Valued Senior Member

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    Thanks for quietly working on this one tashja. As you will later see below, I would be interested in a follow-up from Prof. Unruh.
    So ok we choose the vantage point of a hovering observer not one in free fall. And yes given as taken an UE thermal bath seen by such an observer, it makes sense that lower frequency modes will be reflected, with a trickle escaping as HR. So far, so reasonable.
    Right here I have an issue. Not with the renormalization bit but with the assumption of zero net energy of thermal radiation. The picture has it that enormous tidal g gradients 'tear apart' zero-point EM fluctuations so as to create real photon quanta - yes? How is that not a net gain in energy - given as I pointed out earlier this thread, photons are their own anti-particle? Or put it another way, what *physical sense* can there be to the notion of real -ve energy EM quanta? Energy density is after all a parametric function of field strength - or it was when I went to school. I can see that mathematically putting an 'i' in front of an E or B could do such a trick, but is that not just mathematical trickery? Explaining what an actual -ve energy EM quanta 'looks like' seems problematical to me.
    Again, I question the 'must have' there. Take the case of Schwinger 'vacuum polarization' expected when very intense E fields are generated. Owing to the opposite signs of charge for electron-positron virtual pairs, just a uniform E of sufficient strength is all that's needed to 'tear apart' such virtual pairs so as to create real electron-positron pairs. No-one suggests there the net energy of such real pairs is other than large and positive. How then is that same general condition not true when the 'tearing apart' is owing to tidal g gradients rather than an applied E? Is it not so net positive energy is first required then created in such pairs in either case? Of course for Schwinger vacuum polarization, the resulting current quickly neutralizes the E source. In the BH case though, it gets back to that EM quanta don't surely have opposite 'gravitational charge'. And if one gives them such by mathematical fiat declaration, one is left to actually explain how '-ve gravitational charge' could logically allow such to be other than violently expelled - with only +ve energy quanta capable of being trapped inside EH. At the end of it, if you wish to insist the energy book is balanced and have real +ve energy quanta ejected, real -ve energy quanta have to be trapped/swallowed somehow - DESPITE THEIR IMPLIED NEGATIVE GRAVITATING MASS!
    See above.
    Well thanks for taking the time and effort there to 'unconfuse me', and maybe the fine details somehow add up to a sensible and consistent final picture. As per above comments though, I still have serious reservations.

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    Last edited: Oct 3, 2015
  20. Q-reeus Valued Senior Member

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    I admittedly jumped a little too soon on that one, and only later realized the reference to para 4 linked the two. But - so very strange. That you waited all this time to respond - not until after that reply from Prof. Unruh. How come - given you were on line during and for hours after I posted the original query? Spine issues?

    Incidentally, you give yourself away asking that inept question in #71:
    Might as well ask how long is a piece of string.
     
  21. paddoboy Valued Senior Member

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    Casimir Effect, Black Holes and Hawking Radiation.
    Featuring Professor Mike Merrifield from the University of Nottingham -
     
  22. paddoboy Valued Senior Member

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    Great question Daecon and admirably answered by bruce.
     
  23. Daecon Kiwi fruit Valued Senior Member

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    Spine issues? No. I just couldn't be bothered because you hadn't appeared to have read the Wikipedia article I linked to.

    Exactly how did I "give myself away" by asking a question?
     

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