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It was one of the late theoretical physicist Stephen Hawking’s most famous predictions, made all the way back in 1974: At some point, black holes in space eventually disappear, evaporating into nothingness. But it had never been proven scientifically until now.
Specifically, according to Live Science, Professor Hawking speculated:
Black holes are not perfectly “black” but instead actually emit particles. This radiation, Hawking believed, could eventually siphon enough energy and mass away from black holes to make them disappear. The theory is widely assumed to be true but was once thought nearly impossible to prove.
But how exactly can such a hypothesis be proven? After all, we can’t just travel to a black hole and perform experiments.
That’s where Physicist Jeff Steinhauer and his colleagues at the Technion – Israel Institute of Technology in Haifa come into the picture.
Steinhauer and his fellow researchers came up with a novel way of testing Hawking’s 1974 prediction using an exceptionally cold gas known as a Bose-Einstein condensate that modeled the event horizon of a black hole:
“In a flowing stream of this gas, they placed a cliff, creating a ‘waterfall’ of gas; when the gas flowed over the waterfall, it turned enough potential energy into kinetic energy to flow faster than the speed of sound.
Instead of matter and antimatter particles, the researchers used pairs of phonons, or quantum sound waves, in the gas flow. The phonon on the slow side could travel against the flow of the gas, away from the waterfall, while the phonon on the fast side could not, trapped by the ‘black hole’ of supersonic gas.
Professor Steinhauer explained the experiment:
“It’s like if you were trying to swim against a current that was going faster than you could swim. You’d feel like you were going forward, but you were really going back. And that’s analogous to a photon in a black hole trying to get out of the black hole but being pulled by gravity the wrong way.”
According to Hawking’s theory, the radiation of particles emitted from a black hole would be in a “continuous spectrum of wavelengths and energies.” And he also predicted that it “could be described by a single temperature that was dependent only on the mass of the black hole. Steinhauer’s experiment has now proven both of those to be true.
Physicists around the world were delighted to see someone finally prove Hawking right, with Renaud Parentani, a theoretical physicist at Laboratoire de Physique Théorique of Paris-Sud University commenting:
“These experiments are a tour de force. It’s a very precise experiment. From the experimental side, Jeff [Steinhauer] is really, at the moment, the world-leading expert of using cold atoms to probe black hole physics.”
Somewhere in the universe, Professor Hawking is probably smiling.
Featured Image Via BBC News