Scientists recreate a sonic black hole and confirm a Hawking theory

Scientists recreate a sonic black hole and confirm a Hawking theory
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A team of Israeli scientists confirmed one of the most audacious theories of the mythical astrophysicist Stephen Hawking by creating an artificial black hole. It is the so-called sonic black hole, also nicknamed a mute hole, capable of trapping sound in the same way that gravitational black holes attract and contain light.

During the experiment, which lasted about four months, the team, led by physicist Jeff Steinhauer of the Technion Institute of Technology, put Hawking’s theory to the test, according to which black holes not only trap matter but are also capable of emitting light in the form of so-called virtual particles – which are in fact real, although they come out and disappear in a fleeting period of time – that form pairs and destroy each other. However, Hawking suggested that in some cases, the hole can attract one of the particles and repel the other. The flow of these particles is called static Hawking radiation, although it is almost impossible to detect.

To explore the phenomenon, astrophysicists cooled 8,000 rubidium atoms to near absolute zero and bound them with a laser beam, resulting in a rare state of matter known as a Bose-Einstein condensate (BEC). In this state, the atoms form a kind of super-atom and act in unison.

The study authors then used the second laser beam to create a flow of potential energy that caused the BEC to flow.

As a result, at the boundary between the area where half the gas flowed faster than the speed of sound and the other half the event horizon of the sonic black hole was formed. The phonons – what the quasiparticles of sound are called like that, in analogy to photons of light – present in the faster half of the gas, outside the event horizon, were attracted by the flow and could no longer return to the other side.

“Basically, the event horizon is the outer sphere of a black hole, but it has a small sphere inside it called the inner horizon,” Steinhauer explained.

It took 97,000 iterations of this experiment over 124 consecutive days for physicists led by Steinhauer to confirm Hawking radiation. Fortunately for them, their patience was rewarded.

The expert in general relativity and black holes Amos Ori called the results of the experiment “very important and interesting.” The researcher noted that Steinhauer’s team measured the stationary Hawking radiation emitted by a sonic black hole, which “provides significant experimental support” for the legendary astrophysicist’s analyzes.

Now, Israeli scientists plan to carry out more experiments to see what is happening beyond the approximations used by Hawking, in which radiation is quantum, but spacetime is classical.

The results of the study were published in the journal Nature Physics.