Physicists from the Israel Technical University found confirmation of the theory put forward as early as 1974 by Stephen Hawking that black holes emit radiation. To do this, specialists in the laboratory modeled a black hole analogue and in a series of experiments proved the prediction of a famous theoretical physicist.
According to the general theory of relativity, a black hole does not emit electromagnetic radiation. But Stephen Hawking suggested that this is not the case if, in addition to the general theory of relativity, the laws of quantum mechanics are also taken into account. This possible type of electromagnetic radiation was called Hawking radiation and it was extremely difficult to prove its existence. In addition, for confirmation, it was necessary to measure the temperature of the black hole, which so far is beyond the power of scientists.
In order to study the nature of black holes, researchers create their analogues in laboratories. In one embodiment, a cluster of ultracold rubidium atoms, cooled to several billion degrees above absolute zero, is used. They are called Bose-Einstein condensates. When this condensate begins to flow, it generates a so-called acoustic black hole that catches sound (phonons) instead of light (photons). On the high-energy side of the experiment, the condensate flows slowly, and on the low-energy side – faster. What happens between them is the sound horizon of events.
In 2016, researchers at the Israeli Technical University found that when a pair of entangled phonons appeared on the event horizon in a simulated black hole, one of them is repelled by low-velocity condensate, which is analogous to Hawking radiation. In this case, the high-velocity condensate moves faster than the second phonon, because of which it is absorbed by the black hole. Later, scientists concluded that this is a statistical anomaly. In the course of the repeated experiment, it turned out that one phonon is pushed into the hypothetical space, and the other is absorbed by the hypothetical black hole.
According to mathematician Silke Weinfurtner of the University of Nottingham, the main achievement of the work done was the detection circuit that was used to extract the temperature of the emitted radiation — Hawking’s supposed radiation.
After repeating the experiment 7400 times, the scientists came to the conclusion that their study, both qualitatively and quantitatively, confirms the thermal nature of Hawking radiation.