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This page contains a single entry from the blog posted on May 13, 2008 8:45 AM.

The previous post in this blog was Einstein's Mistakes.

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Nearly seeing Hawking radiation?

Astrophysicists have known for more than three decades that black holes shouldn't be totally black — they should emit a certain amount of "Hawking radiation" from the production of particle–antiparticle pairs around their event horizons. But detecting Hawking radiation has so far proved tricky, mostly because its temperature would be at least eight orders of magnitude lower than the cosmic microwave background left over from the Big Bang.

One way round this problem, as Ulf Leonhardt and colleagues from the University of St Andrews, UK, demonstrated earlier this year, might be to create systems that are analogous to black holes in the lab in which the temperature of the radiation is much higher. The researchers showed that a pulse of light travelling through a fibre can behave like a black hole, and, although they didn't actually detect Hawking radiation, they showed that in principle it should be possible.

Now, in a paper published today in the New Journal of Physics, is seems as though Leonhardt's group are one step closer. Rather than use pulses of light as an analogous system to a black hole, they have built a system of water waves. I confess that I haven't yet studied this paper carefully enough to describe with any certainty what the researchers have done, suffice it to say they claim to have observed "negative-frequency" waves, the classical analogue of anti-particles which are the hallmarks of Hawking radiation.

In a brief email conversation last week, Leonhardt told me that they are not yet sure whether this is enough to constitute an observation of a classical analogue of Hawking radiation: "Hawking's effect is a quantum phenomenon, a spontaneous quantum process, but like all spontaneous processes it can be stimulated. This is what we did, we sent in waves and saw a tiny bit of stimulated negative-frequency waves, but there are quantitative differences between experiment and theory that we do not understand yet."

Of course, if and when Leonhardt's group do find negative-frequency waves that agree with theory, there will be a debate as to whether they are "real" Hawking radiation. No doubt you will be seeing more of this on physicsworld.com soon.

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Comments (3)

  • 1 Andrei Kirilyuk May 13, 2008 5:42 PM

    Ah, that "reminiscence science", where everything resembles everything else and this certainly justifies realisation of otherwise useless but expensive experiments... It wouldn't actually need any comment but everything is so closely related in this world, and while our "officially great" scientists (by their own judgement) are amusing themselves in that way, we have catastrophically accumulating and persistently unsolved real problems, in both fundamental physics and its urgently needed new applications (e.g. clean, efficient and practically inexhaustible energy sources). Whereas there are very serious, well-known doubts in real existence of "black holes" as such (as opposed to simply massive star remnants and galaxy cores) and "Hawking radiation" is a highly speculative, basically useless subject full of its own contradictions (including the absent understanding of quantum, gravity, and quantum gravity), these guys need to advance yet much further on the road of absurdity and try to "confirm" those at least doubly doubtful "mind games" by yet more doubtful analogies between "assumed" cosmic-scale phenomena we cannot observe directly and completely different experimental systems from their lab. Yeah, that's it, "life after death", science after the end of science... That's probably why it's so strange. But I want to preserve a grain of optimism here and believe that British science is completely independent of the opinion of British public providing its entire financial support. Although... the happy subjects of Her Majesty are known to be proud of their eccentricity: they just like it in that ultimately strange way! And maybe one doesn't even need to drink too many pints of beer in a pub (in a British pub!) to start believing in a mysterious link between "negative frequency water waves" (or were they beer waves?!) and hypothetic quantum radiation in the heart of an esoteric black hole millions of light years away... After all, in good enough life conditions, one seems be ready to believe in an arbitrary fairy tale, from the official version of 9/11 to the deeply rooted resemblance of everything to everything else. Before people called it religion (and it was consistent because a blind faith should remain irrational) and now they call it science (and it is inconsistent because science should be rational). But these are minor changes on the background of the main common factor: the reason why "lay" people should work and nourish their self-designated "priests" ... without reason, i.e. without any meaningful result of the latter. And this is indeed reminiscent ... of parasites and their victims! God save Her Majesty... She'll need it, with such priests...

  • 2 Zephir May 13, 2008 9:12 PM

    The hydraulic jump or sink model of black holes are pretty old, in fact. The AWT proposes an optical analogy of "white hole" concept.

    The common black hole is "black" because of giant vacuum density gradient, which is behaving like glass sphere or semitransparent mirror due the total reflection phenomena near the event horizon. The larger the black hole is, the larger is curvature of space around it. But every space-time curvature has its own energy density by Einstein field equations, and such energy density is equivalent to additional matter density of vacuum due the E=mc^2 equivalence. This dense vacuum is surrounding black hole and it's balancing its internal mass density by such way, it decreasing surface density gradient.

    If the black hole become sufficiently large, then the mass density of vacuum above black hole will compensate the mass density below event horizon, so nearly no density gradient can appear here. Therefore the vacuum density gradient will not reflect the energy from inside anymore and whole the object will change into giant glowing star, emanating both energy, both matter from inside, so called the quasar. We can compare the negative capillary waves of the sink model, which are getting faster for shorter wavelength, so they can penetrate the event horizon as well. The similar conclusion results from Yilmaz and Heim theories, you can find some transparent derivation for example here: http://arxiv.org/ftp/arxiv/papers/0712/0712.1110.pdf

    By Aether Wave Theory most of sufficiently large galaxies inside of our Universe were created by evaporation of quasars, and the Milky Way is no exception. The black hole siting at the center of most of galaxies is cold remnant of quasar, which has evaporated the excessive matter. This is because only black holes larger then certain mass limit can evaporate their matter by the above mechanism.

  • 3 acer July 3, 2008 2:09 AM

    By Aether Wave Theory most of sufficiently large galaxies inside of our Universe were created by evaporation of quasars, and the Milky Way is no exception. The black hole siting at the center of most of galaxies is cold remnant of quasar, which has evaporated the excessive matter. This is because only black holes larger then certain mass limit can evaporate their matter by the above mechanism.

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