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Hawking Radiation Claimed Created In a Lab
eldavojohn writes "In 1974, a young newcomer to the Royal Society named Stephen Hawking predicted that black holes emit Hawking Radiation. Researchers have been looking for it in space ever since. A new paper up for publication claims to have beaten searchers by observing it in a lab. Doing it wasn't easy. They say they brought light to a standstill by drastically increasing the refractive index of the material it was being fired at, creating a 'white hole.' This horizon, beyond which light cannot penetrate (event horizon), is the same between white and black holes, which caused the team to suspect they observed Hawking Radiation when light of a different uniform wavelength than the input laser was emitted. But, before you rejoice, the Tech Review article notes, 'Of course, the big question is whether the emitted light is generated by some other mechanism such as Cerenkov radiation, scattering or, in particular, fluorescence which is the hardest to rule out.'"
pics or it didn't happen
I read TFA and all I got was this lousy cookie
OK, either you're a troll and I'm wasting my time (most likely) or you're misunderstanding something. What Hawking admitted wasn't that the radiation didnt' exist but that the radiation did not in fact violate the principle of conservation of information. Previously Hawking had believed that it must violate said principle because there was no understood way for there to be a connection between the information about the matter that had fallen in and gone past the event horizon and the radiation that would be emitted. This was challenged by another physicist, whose name escapes me since I can't look it up at the moment, who reasoned (along with a more definite proof of course) that the information gets left at the event horizon also. This is because of the fact that from the perspective of anyone outside the event horizon any matter or energy falling in will never actually reach the event horizon it'll just appear to be slowing down further and further until it for all intents and purposes stops. This allows the virtual particles making up hawking radiation to be influenced by the information left at the event horizon without there being a need to have communication between the singularity at the center and the event horizon.
[citation needed]
As far as I know Hawking Radiation and black hole evaporation have not been ruled out. The effect is just so small that there is no experimental evidence of it.
Actually, you'd better hope black holes evaporate or the black holes the LHC might create may destroy the earth! I for one use a tin foil hat just to be safe.
Popular visualizations and even the notion of "virtual particles" do not allow very accurate reasoning with regards to Hawking radiation. In particular, the "promotion process" from "virtual" to "real" is just a crutch for proving something to all orders in perturbation theory. Shortly after Hawking-Bekenstein, Bill Unruh proved that simply being in a uniformly accelerated reference frame creates a perception of thermal background radiation coming from the background -- at a temperature equivalent to the pseudo-event horizon of the acceleration for the duration of the acceleration. You see, while if you move at a constant rate any photon will catch you just as quickly as if you were standing still (basic special relativity) if instead you accelerate forever, you asymptotically approach the speed of light, but there are photons far enough behind you that will never catch you. How far behind they need to be depends on how fast you are accelerating. So, every acceleration corresponds to a pseudo event horizon. As soon as one stops accelerating the photons can catch up to you. Unruh's result does *not* depend on the permanence of the horizon, but works for temporary accelerations. So, the horizon does not need to be "permanent" for the "promotion" to occur. A better way to think about Hawking radiation is any gravitation field (any curved space, that is) decaying via thermal radiation, or space itself providing some "resistance to acceleration" or intrinsic acceleration-only viscosity where the energy taken away from the acceleration is converted to thermal radiation. The image of a virtual pair around an event horizon is not, ultimately, how the result holds or is proven or even what the process is "about". It's more like an "inspiration to a derivation" than something to be taken so literally.
By the way, even if this experiment and their conclusions hold water, it is not a proof of black hole evaporation or Hawking radiation. It would be more like a proof of concept.
In the experiment, they've created a pseudo-event-horizon from which light can't escape. It's only a light event horizon though. Shoot a bullet through their material and you will definately see it go through the event horizon without any problems.
The similarities to a real black hole is that photon pairs created on the pseudo-event-horizon should create radiation if Hawkings reasoning about real black holes is correct. So, it would show that Hawkings thought experiment had some merit but not that black holes necessarily radiate.
Well, to get a proper explanation of 'white holes', we really need to go to the experts:
Cat: So, what is it? ... back into the Universe? ... back into the Universe?
Kryten: I've never seen one before - no one has - but I'm guessing it's a white hole.
Rimmer: A *white* hole?
Kryten: Every action has an equal and opposite reaction. A black hole sucks time and matter out of the Universe; a white hole returns it.
Lister: So, that thing's spewing time
Kryten: Precisely. That's why we're experiencing these curious time phenomena on board.
Cat: So, what is it?
Kryten: I've never seen one before - no one has - but I'm guessing it's a white hole.
Rimmer: A *white* hole?
Kryten: Every action has an equal and opposite reaction. A black hole sucks time and matter out of the Universe; a white hole returns it.
Lister: So, that thing's spewing time
Kryten: Precisely. That's why we're experiencing these curious time phenomena on board.
Lister: What time phenomena?
Kryten: Like just then, when time repeated itself.
Cat: So, what is it?
[Kryten, Rimmer, and Lister stare at Cat]
Cat: Only joking.
I am officially gone from
So they are actually going to make black holes at LHC without even knowing if it will evaporate?
For the LHC to create black holes at all would require a whole bunch of very speculative physics to be true, and a whole bunch of very well-established physics to be false.
In particular, if the LHC can create black holes then millions of black holes are being created every day by cosmic rays, which can have twenty orders of magnitude more energy than the LHC. No evidence of those black holes is seen anywhere, not in geochemical track analysis, not in the radiation signature of cosmic ray showers, no where. Ergo, either such black holes are not being created, or they are being destroyed with incredible rapidity.
For the beam dump of the LHC to behave any differently would require physics so arcane as to be basically magic, and anyone who is worried about it should also be terrified that a herd of flying elephants will trample them to death, because that's a far more probable event.
Blasphemy is a human right. Blasphemophobia kills.
...They say they brought light to a standstill by drastically increasing the refractive index of the material it was being fired at...
They tried to take pics but somehow there wasn't enough light..
Not quite, i was referring to this. i couldn't look that up earlier because i was on a really bad connection that was dropping packets left right and center.
'BTW, on a more serious note: a quick google search of "hawking radiation disproved" [google.com] doesn't seem to come up with much serious material.'
Well, you generally shouldn't come up with a lot of material for or against this theory; you need a black hole to really test it.
We all understand what Hawking radiation is, right? Its the run-off of actual particles created when a virtual particle pair "pops" into existence near the event horizon of a black hole; normally the two annihilate each other but in this case one of the two gets sucked into the black hole, the other shoots off into spacetime. This also gives the hole a little negative mass, leading to the other huge implication in this theory; black holes can evaporate.
Python: 'And then suddenly you have a language which says "we're all stuck with whatever the whiniest coder wants".'
Both particles and antiparticles escaping carry positive energy away from the black hole. The consumed virtual particles carry negative energy into the black hole. Therefore the mass decreases.
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It sounds like the light they see is monochromatic. Hawking radiation would be blackbody radiation. Unless they have a reason why this blackbody would only have one mode and an incredibly high effective temperature. I'm guessing that they've found an uninteresting fluorescence feature.
Technology review's arXiv blog is so difficult to get any details out of. It's hard to figure out what these people have done. "frequency of 1055 nm"? I guess I'll have to go to the full article.
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