Black Hole Analogue...

Victor De Schwanberg/SPL

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.

Hawking radiation relies on a basic tenet of quantum theory — large fluctuations in energy can occur for brief moments of time. That means the vacuum of space is not empty but seethes with particles and their antimatter equivalents. Particle-antiparticle pairs continually pop into existence only to then annihilate each other. But something special occurs when pairs of particles emerge near the event horizon — the boundary between a black hole, whose gravity is so strong that it warps space-time, and the rest of the Universe. The particle-antiparticle pair separates, and the member of the pair closest to the event horizon falls into the black hole while the other one escapes.

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.

Nature: Hawking radiation mimicked in the lab, Ron Cowen