Professor Jeff Steinhauer stands with his model of a black hole. (Nitzan Zohar)
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Are black holes really all that black? A new study supports Stephen Hawking’s theory.
By Rachel Feltman
You know Stephen Hawking’s name, but do you know the theory that made him famous? Hawking radiation, which the physicist proposed back in the 1970s, is theoretical energy emitted by black holes. Instead of just consuming everything around them, tugging with such a fierce gravitational pull that not even light can escape their clutches, Hawking suggested that black holes might emit a tiny bit of radiation — a glow in the black void, if you will — that would slowly strip away their mass, shrinking them into eventual oblivion.
Now, Jeff Steinhauer of the Technion Institute of Technology in Haifa, said he has created an artificial black hole that produces Hawking’s proposed glow. His study, which could provide the most convincing evidence for Hawking’s theory to date, was published Monday in Nature Physics.
Steinhauer – notorious for doing most of his work solo, which is unusual in the sciences – created a black hole analogue that pulls in sound the way black holes are thought to pull in light. Now Steinhauer reports that his model black hole still lets out particles.
Hawking radiation is meant to be the result of the tricky nature of quantum mechanics, the way the subatomic particles that make up our universe interact with one another on the tiniest of scales. To make a long (and confusing) story short, the idea is that when the particles being pulled into the black hole are suddenly joined by corresponding, virtual antiparticles (particles do that) one half of the pair – which would usually be destroyed, the two halves canceling each other out almost instantly – might pop up on the outside of the event horizon and go out on its merry way.
Steinhauer’s study essentially shows this same phenomenon, or at least particles that seem to be emitted for this reason, but brings the action close enough for humans to observe the minute process.
“I think this work stands on its own as verification of Hawking’s calculations,” Steinhauer told Popular Science.
Other researchers aren’t so sure.
“This experiment, if all statements hold, is really amazing,” Silke Weinfurtner, a theoretical and experimental physicist at the University of Nottingham in England, told Nature. But an acoustical model of a black hole – no matter how well-designed – simply isn’t a black hole.
“It doesn’t prove that Hawking radiation exists around astrophysical black holes,” Weinfurtner added.
“Big results needs solid proof,” the University of British Columbia’s Bill Unruh told New Scientist.
Unruh was one of the first scientists to propose using a model like Steinhauer’s. Because black holes are so difficult to study, and the signatures of Hawking radiation so tiny, analogies like this are kind of the best science can manage right now. That doesn’t mean we can take the results as clear-cut evidence. “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,” he said.
The universe isn’t much less mysterious than it was when Hawking first proposed his theory more than 40 years ago. These latest results might not be definitive proof that Hawking radiation seeps out from black holes, but we’ll have to just keep chipping away at the secrets of the cosmos.
source : The Washington Post