Black holes still remain among the most mysterious objects in the universe. Once in their existence, few believed. And the fact that they are in reality described only in a variety of physical models. The question is how to study what is at the distance of millions of light years away from our planet? Perhaps the answer can give a “sonic black hole”, which will also help to resolve one of the paradoxes that emerged during the research of Stephen Hawking. But what is the “audio black hole”? Let’s deal.

First we need a little dip into history. In 1974 Stephen Hawking conjectured that black hole is not actually black. Its black color is due to the fact that gravity in the area of the event horizon is so strong that even light rays can’t overcome this influence. Hawking was thus assumed that the structure of space-time on the event horizon will experience a “quantum fluctuations”. That is, at this point, pairs of particles and antiparticles can be freed from the effects of gravity and appear on either side of the event horizon.

This process was called “Hawking Radiation”. Due to “quantum fluctuations” that are born from the vacuum of a black hole pairs of particle-antiparticle occur near the event horizon of a black hole and one of them “falls” into a black hole, and the other “flies.” From the law of conservation of energy it follows that the “fallen” beyond the event horizon, the particle must have negative energy, at that time, as “flown away” must possess positive energy. In other words, black holes lose energy by radiation. They slowly evaporate and shrink, eventually disappearing completely.

## What is the paradox of black holes

The problem is that, according to the calculations of Hawking radiation the black hole will be random. This means that the evaporating black hole destroys the information, while quantum physics is based on the premise that information is never lost. This is the main paradox, the prisoner in the study of the nature of black holes.

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“the First ever actual photograph of a black hole”

## What is the “Audio black hole”

Many years ago, physicist bill Unruh argued that the idea of Hawking on the event horizon of black holes should also be applied to the “sound horizons”. The sound horizon is, roughly speaking, the analogue of the event horizon applied to sound waves the only difference is that in black holes as the unit of speed measurement uses the speed of light, and “sonic black holes” — the speed of sound.

In 2016 Jeff Steinhauer from the Technion (Israel Institute of technology) in Haifa, Israel, in one of the experiments recreated conditions for the emergence of the “sound horizon”, accelerating the fluid from the atoms of rubidium-87 to supersonic speed. In the same year managed to find the analogue of Hawking Radiation. Quantum units of sound, called phonons, appear in pairs, and a single phonon was going on within the moving fluid, while the other went upstream and “ran away”.

Now, three years later, an improved camera allowed “to test predictions of Hawking”. In his new work of Steinhauer and three of his employees found that their sound radiation carries no information.

“The discovery gives us hints on the information paradox. Thermal shape of the spectrum suggests that Hawking radiation carries no information. Thus, we must look for information elsewhere to solve it.”

*Compare the “sound” and “space” black holes*

The key question is whether it is possible to consider space-time on the event horizon of a black hole as a continuous. New data confirm that in the case of fluid flow which, as is known, continuously, the paradox still remains, since the energy of a “sonic black hole”, decreasing, leads to loss of information.

But there’s a catch: the condition is workable for liquids, may not work for space-time, which may not necessarily have a continuous progress in the area of the event horizon of a black hole. The presence of “interrupted” the flow of time in the area of the event horizon could explain the paradox associated with the loss of information, because in this case, pairs of particles formed as a result of Hawking Radiation, do not disappear, but simply “moving to another level” of space-time.

Thus, if we can simulate the “intermittent” during the course of experiments with “sonic black hole”, we can solve the paradox associated with the disappearance of the information emerging in the area of event horizon of black holes.

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