Is a black hole a true black hole if it devours sound waves instead of light waves? Will Stephen Hawking care as long as it proves once-and-for-all his theory on black hole radiation? Can sonic black holes be used to get rid of bad music?
According to his report in Nature Physics, experimental physicist Jeff Steinhauer spent seven years working alone in his lab at Technion-Israel Institute of Technology in Haifa on his idea for creating a sonic black hole. His goal was to prove Stephen Hawking’s 42-year-old theory that black holes emit weak radiation – now called ‘Hawking radiation’ – as matter-antimatter pairs of photons become trapped on opposite sides of the event horizon and cause the black holes to shrink and eventually disappear. Since we can’t get close enough to a real black hole, Hawking radiation remained an interesting but unproven concept.
Enter Bill Unruh, a physicist with the University of British Columbia. In the early 1980s he proposed that not-quite-black-holes could be created in a lab to safely simulate a real one and test Hawking’s theory. It took over 30 more years, but Steinhauer finally created a sonic black hole by using super-cooled rubidium atoms (interesting factoid – rubidium was co-discovered by Robert Bunsen, the burner guy). The rubidium atoms were then super-accelerated to a speed faster than sound, thus creating a sonic black hole where no sound can exist. Steinhauer was then able to measure sonic radiation (phonon pairs) on either side of the black hole’s soundless event horizon.
Does this prove the existence of Hawking radiation? Kind of. Some physicists are waiting for the results to be duplicated in independent experiments. Ulf Leonhardt, a physicist at the Weizmann Institute of Science in Rehovot, Israel, wants to see low-energy radiation in the sonic black hole, not just the high energy phonon pairs found by Steinhauer.
Bill Unruh is excited despite the critics.
In any case, I regard this as a very beautiful experiment, one that people have thought of doing for 10 years now, but he is the first to do so. That he has seen the correlations of emissions by the horizon, whether entangled or not, is a real coup.
And Hawking? He hasn’t made any public comments yet (he’s probably rehearsing for his next appearance on The Big Bang Theory). Leonard Susskind, a theoretical physicist at Stanford University, thinks this may be Nobel-worthy if solidly proven.
[It would be] a triumph for Hawking, perhaps in the same sense that the expected detection of the Higgs boson was a triumph for Higgs and company.
It would be even bigger if sonic black holes could get rid of Justin Bieber’s music.