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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.
So when the virtual particle pair is created at the event horizon, one is trapped stationary beyond the horizon, and the other escapes (becoming real).
In this experiment obviously the event horizon doesn't persist indefinitely, so when the horizon collapses, do the 'trapped' photons escape? and hence is there a time delayed double emission of the hawking radiation? Would this provide a testable signature?
Any physicists know?
Windows in 6 Bytes (IA-32) : 90 90 90 90 CD 19
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
umm, is this what you're talking about?
weinersmith
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.
As I mentioned above, one does not need a black hole for this -- all curved space should release thermal energy, though the rate is usually immeasurably small. Google Unruh effect and read about it in relation to the Sokolov-Ternov effect which has been observed since the 1970s. There is not perfect interpretational consensus about all this, though.
...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..
Now, its creation is a quantum state transition which has a "magical" quality in the same way that, say, a photon escaping an atom's electron shell does. There is no extended energy transport process at all. The electron makes a quantum jump simultaneously with the photon field of the world gaining a new photon traveling away. Indeed, with visible light, the wavelength of the photon -- hundreds of nanometers -- can easily exceed the spatial scale of the atoms electron shell, usually a few nm. So, the photon kind of just "appears".
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".'
i was on a really bad connection that was dropping packets left right and center.
So, you're saying that your information was falling into a black hole and you couldn't retrieve it from the event horizon???
Nichelle Nichols: "It's about that rip in space-time that you saw!"
Stephen Hawking: "I call it a Hawking Hole."
Fry: "No fair! I saw it first!"
Stephen Hawking: "Who is the Journal of Quantum Physics going to believe?"
Why would the black hole diminish? Shouldn't the same amount of virtual particles and virtual anti-particles cross the event horizon?
- Raynet --> .
Although, the black holes that can currently evaporate due to this mechanism are (as I understand it) well below stellar mass. The amount of hawking radiation that larger black holes emit is below the amount of energy they receive from the cosmic microwave background, thus they cannot evaporate.
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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Leonard Susskind was the guy and the problem wasn't originally an "information" problem, but instead an entropy problem. The information questions came in after they sorted out the holographic principals of information representation along the surface area of the event horizon.
Sean M Carroll has a good book about what that means for time if you are interested...
America is all about speed. Hot, nasty, badass speed. -Eleanor Roosevelt, 1936
An electron's classical radius isn't zero, but more to the point, you can't use just classical physics at that scale.
While I too am not a physicist, my understanding is that, while normal particles are falling into the black hole, it is increasing its mass faster than it is losing it. However, for black holes that do not have an accretion disk or other inflow of matter, Hawking radiation would cause a slow but net decrease in mass of the black hole.