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byron178
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Has hawking radiation ever been observed?
Vanadium 50 said:No, it has not.
Vanadium 50 said:First, why did you ask the question if you just wanted to argue about the answer.
Second, this is not a black hole. Read what you posted - this is an analog of a black hole.
No it isn't.byron178 said:so this is not evidence of hawking radiation?
Demystifier said:No it isn't.
Demystifier said:About analogue Hawking radiation, not about true Hawking radiation. Do you know what "analogue" means?
byron178 said:i would also like to hear other people's opinion.
danR said:You could say it is Hawking radiation in the sense that you could have 'real' Hershey bars cranked out of a fake machine. They look and taste the same as those coming from the Hershey company.
If the researchers have produced radiation with the/a predicted signature, and by the production of virtual photons (this is a big claim, incidentally) then half of the conceptual framework of Hawking radiation is established.
The 'analogue' part of the thing is that intense gravitational fields cannot be generated in labs. So they use other fields: electric and magnetic fields, and try to use these in a way (hopefully an analogous way) to generate these 'virtual' photons.
That's the fake part of this 'Hawking' radiation. Genuine Hershey bars come out of the Hershey bar company, and imposters will be sued. If (If!) Hawking radiation is real, Black-holes own the patents and the process. That is why there are many skeptics in the article:
Hawking radiation = Hawking radiation + black holes. So they have not produced Hawking radiation. But they claim they have shown that the actual output that a BH supposedly produces can actually exist, so it gives interest in furthering the search for it by looking at Black Holes themselves.
http://en.wikipedia.org/wiki/Analog_models_of_gravitybyron178 said:No,what does it mean?
Demystifier said:
byron178 said:what about the article? what does that talk about?
danR said:I can't give a full synopsis. That's my opinion on the article and the topic. The OP only needs a nuanced answer to the question: have they found Hawking radiation? Yes and no. And even that opinion is arguable. For example, having determined what it was that Hawking was claiming comes out of a BH, researchers have set up conceptual and physical apparatus that bears absolutely no resemblance to the extremely vacuous locale of an event horizon. It's as though I dreamed of Io emitting drunk purple elephants, and someone devised an apparatus that bears almost no resemblance to the surface of Io, that emits actual drunk purple elephants. Then I can say, 'there, part of my dream ('theory') about Io is realized.'
And Hawking proposed his radiation at a time when even BH' existence were denied by reputable physicists: Philip Morrison, for example. Hawking posited BHs, claimed they retained all information that fell into them, and then invented something coming out of them, not excluding the possibility of full sets of the leather-bound volumes of Marcel Proust.
byron178 said:so how is hawking radiation explained without virtual particles?
danR said:It isn't. Hawking radiation entails virtual particles. The researchers appear to have that much covered.
byron178 said:I meant to say is that is there an interpretation of hawking radiation without virtual particles? also do virtual particles time travel?
danR said:Q1 No! It would be like having a fission-bomb without neutrons. It's a package deal. Accept no substitutes. Take it back to the store. Demand a refund. Ask for the manager. Call the Better Business Bureau. Don't take wooden nickels.
Q2 I don't believe in time travel, a fortiori: it doesn't even have a meaning, except in the very restricted sense of t-invariance in particle physics. For that, you will have to go to the particle forum and look for Feynman diagram experts, because I have no knowledge about it.
byron178 said:is there debate as to weather hawking radiation exists? also can hawking radiation be explained without virtual particles?
Actually, it doesn't. The standard derivation of Hawking radiation is based on Bogoliubov transformation, which does NOT involve virtual particles.danR said:Hawking radiation entails virtual particles.
Demystifier said:Actually, it doesn't. The standard derivation of Hawking radiation is based on Bogoliubov transformation, which does NOT involve virtual particles.
As far as I am aware, only POPULAR "explanations" of Hawking radiation involve virtual particles. The true calculations of it don't.
danR said:"One might picture this negative energy flux in the following way. Just outside the event horizon there will be virtual pairs of particles, one with negative energy and one with positive energy." (emphasis added)
Particle Creation by Black Holes
S. W. Hawking
Commun. math. Phys. 43, 199—220 (1975)
________
Without requiring virtual (pairs of) particles, perhaps Hawking is putting things in a way easy to view. Or perhaps he's hedging.
Naty1 said:... Hawking radiation cannot occur until the universe becomes cooler than black holes, so it has NEVER been observed.
Hawking radiation cannot occur until the universe becomes cooler than black holes, so it has NEVER been observed.
...No astronomical black hole is currently evaporating. Quite the opposite, they are all absorbing energy and growing...The emptiest regions of instellar space are still far warmer than a stellar mass black hole...thermal energy always flows from hot to cold...so it follows that radiation from the warmer regions of space flow into the colder black holes...
Wikipedia says: Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter
Naty1 said:In fact Hawking radiation cannot occur until the universe becomes cooler than black holes, so it has NEVER been observed.
phinds said:I still do not understand this statement and would appreciate knowing how/why you believe this. I can understand that if Hawking radiation is not thermal radiation or the equivalent, your statement might be true, but why would it be?
Thanks