A Triumphant Fist Pump for Stephen Hawking, Because He Cannot for Himself

We now have some experimental verification of the existance of Hawking radiation:

Scientists have come closer than ever before to creating a laboratory-scale imitation of a black hole that emits Hawking radiation, the particles predicted to escape black holes due to quantum mechanical effects.

The black hole analogue, reported in Nature Physics1, was created by trapping sound waves using an ultra cold fluid. Such objects could one day help resolve the so-called black hole ‘information paradox’ - the question of whether information that falls into a black hole disappears forever.

The physicist Stephen Hawking stunned cosmologists 40 years ago when he announced that black holes are not totally black, calculating that a tiny amount of radiation would be able to escape the pull of a black hole2. This raised the tantalising question of whether information might escape too, encoded within the radiation.

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Hawking radiation, the result of attempts to combine quantum theory with general relativity, comprises these escaping particles, but physicists have yet to detect it being emitted from an astrophysical black hole. Another way to test Hawking’s theory would be to simulate an event horizon in the laboratory.

To this end, Jeff Steinhauer, a physicist at the Technion-Israel Institute of Technology in Haifa, used a collection of rubidium atoms chilled to less than 1-billionth of a degree above absolute zero. At such temperatures, the atoms are tightly packed and behave as a single, fluid quantum object and so can be easily manipulated. The cold temperature also ensures that the fluid, known as a Bose-Einstein condensate, provides a silent medium for the passage of sound waves that arise from quantum fluctuations.

Using laser light, Steinhauer manipulated the fluid to flow faster than the speed of sound. Like a swimmer battling a strong current, sound waves travelling against the direction of the fluid become ‘trapped’. The condensate thus becomes a stand-in for the gravitational event horizon.

Pairs of sound waves pop in and out of existence in a laboratory vacuum, mimicking particle-antiparticle pairs in the vacuum of space. Those that form astride this sonic event horizon become the equivalent of Hawking radiation. To amplify these sound waves enough for his detectors to pick them up, Steinhauer established a second sonic event horizon inside the first, adjusting the fluid so that sound waves could not pass this second event horizon, and are bounced back. As the soundwaves repeatedly strike the outer horizon, they create more pairs of soundwaves, amplifying the Hawking radiation to detectable levels.

I would also note that this is a wicked cool experiment.

Using a moving fluid and sound as an analogue for an event horizon is completely sick.  (In a good way)

Science, Bitches!