The laboratory’s analogue of the black hole has provided new indirect evidence that these mysterious space objects really emit gas streams of charged particles, according to the Science Alert portal, which refers to a new scientific study published in the journal Nature. Physicists claim that the black hole analogy created by them has a temperature that is a necessary prerequisite for the radiation of the same name, predicted by Stephen Hawking.
Black holes emit nothing. Or does it radiate?
According to the general theory of relativity (GTR), nothing can escape a black hole. Their gravitational force is so great that even light, the fastest thing in the Universe, is not capable of developing sufficient speed to break out of its influence. Thus, according to GR, black holes cannot emit any electromagnetic radiation.
Nevertheless, the theory proposed in 1974 by Hawking said that if the rules of quantum mechanics are added to the question, then black holes can actually radiate something. This is a theoretical type of electromagnetic radiation, named after Hawking himself.
This hypothetical radiation resembles blackbody radiation produced by the temperature of a black hole, which is inversely proportional to its mass. Scientists have not been able to find it directly. Recently, the first real pictures of the black hole were taken, so everything is still ahead. Nevertheless, physicists believe that this radiation, if it exists, would be too weak to be found using our modern scientific instruments.
Measuring the temperature of a black hole is also not an easy task. The black hole with the mass of the Sun will have a temperature of only 60 nano Kelvin. The cosmic microwave background radiation, which it will absorb, will be much higher than the Hawking radiation, which it would emit. Moreover, the larger the size of a black hole, the lower its temperature will be.
To test Hawking’s assumption, physicists from the Israel Technical University conducted an experiment with the closest “analog” of the black hole, which has so far been created in laboratory conditions.
Is Hawking radiation real?
It was invented by Israeli physicist Jeff Steinhauer in 2016 and is a Bose condensate of cold rubidium atoms (cooled almost to absolute temperature), in one region of which atoms move at supersonic speeds and in the other move very slowly. When moving, the condensate creates a so-called acoustic black hole that catches sound (phonons) instead of light (photons). Quanta of sound that fall into this area intersect a kind of “acoustic event horizon”, since they can no longer leave it. Studying the characteristics of the acoustic analogue of a black hole, experts concluded that they were close to theoretical models, implying the presence of Hawking radiation.
In addition to the experiment in 2016, Steinhauer and his colleagues were able to demonstrate that a pair of entangled phonons can appear in the acoustic horizon of events of their black hole analogue, one of which is repelled by atoms of a slowly flowing Bose condensate into space, creating the Hawking radiation effect. At the same time, another phonon of a pair can be absorbed by a black hole analog due to high-speed condensate.
It should be noted that at the beginning of this year another group of Israeli physicists from the Weizmann Institute under the leadership of Ulf Leonhardt created its own analogue of the black hole, where fiber optic technologies were used as a base for the event horizon. Then scientists considered a similar observable result a statistical anomaly. However, the new experiment of the Steinhauer group proved that it is not. The result of the new experiment showed once again that one photon can be thrown into a hypothetical space, and the other absorbed by a hypothetical black hole. Leonhardt has already commented on the success of the Steinhauer Group:
“I congratulate Jeff on this result. This is a very important step for our entire scientific community. This is something to be really proud of, ”said the scientist in an article in the journal Physics World.
“The main innovation of the work of scientists is a well-thought-out detection scheme, which they use to extract the temperature of the emitted radiation. The result obtained by them using a quantum simulator provides the first proof of the existence of radiation by Hawking, ”Silke Weinfurtner commented on the result of the work of Israeli scientists and mathematician of the University of Nottingham.
Evidence that Hawking was right is growing, but this new method for determining the temperature of an analog black hole can help get a deeper understanding of the thermodynamics of a black hole.