First "Observation" of Hawking Radiation

KentuckyFC writes "Italian physicists are claiming the first observation of Hawking radiation, but not from a black hole. Instead they've spotted it streaming from a sonic horizon in a Bose Einstein Condensate (abstract on the arXiv). That's consistent with previous predictions but they're claiming the 'first' even though the experiment was only a numerical simulation. Does that really count?"

Comments

Re:Black holes should radiate anyway

[ExecutorElassus]

yes, but Hawking radiation is somewhat different, and requires no material in the vicinity. It works like this: there are always opposite particles (say, positron-electron pairs) that spontaneously appear at the subatomic level. But in the normal universe, they immediately re-collide, giving back to the local space whatever energy was used to create them. That's a bad explanation (because I'm not a physicist), but it gives a rough picture. At the edge of an event horizon, however, there is a small - though nonzero - chance that one or the other particle will get sucked down the gravity well before it can remerge with its opposite. Thus the one that survived ambles off into space, no doubt pondering its cosmic parthenogenesis. The energy of the particle is - for reasons unknown to me - taken from the black hole. Also, this process steadily accelerates as the black hole continues to lose mass through the process: it eventually pops out of existence in a burst of gamma radiation.

So, it's a little more complicated/interesting than you described; I'm sure it would be even better if someone here could describe it from an actual background in physics, instead of the armchair variety I can muster.

Re:Doesn't Count

[Beetle B.]

but you may argue that they have produced evidence that supports the theory. No, you can't.

Without knowing the details of both theories, it's hard for me to judge. Basically, if their formalism is more or less isomorphic to Hawking's (without their realizing it) - then all they've done is do Hawking's work over again.

If they used independent formalism to get Hawking radiation, then it's a good sign, and shows that their theory is consistent with Hawking's (and perhaps later someone will link the two).

In either case, they did not produce any evidence. At best, they're saying, "If you look at this our way, it is consistent with what Hawking predicted."