# Is it possible to store information in a black hole

(ORDO NEWS) — In the era of “big data” humanity begins to generate huge amounts of information. And where can the accumulated knowledge of a super-civilization be stored?

Sometimes wonderful discoveries owe their origin to ordinary … chatter. This was also the result of a conversation between the American physicist John Wheeler and his graduate student Jacob Bekenstein back in 1970.

When hot tea is mixed with cold tea, Wheeler reasoned, a liquid with an intermediate temperature is obtained. The thermal motion of water molecules is chaotic, and the degree of this chaoticity increases with increasing temperature.

To measure randomness, a special quantity is used – entropy. The entropy of two merged cups of tea will be greater than the sum of the entropies of the hot and cold cups. As a result, the total entropy of the Universe will also increase, as required by the second law of thermodynamics.

However, what happens if you throw a cup of tea mixture into a black hole? In fact, the world entropy will even decrease, since its former carrier will completely disappear from the outside world.

### Save the universe

Bekenstein tried to object and two years later showed that the outer boundary (horizon) of a black hole behaves like a heated black body.

Therefore, a hole can be assigned a non-zero temperature and, consequently, a certain entropy, albeit a very peculiar one. The entropy of an ordinary body is proportional to its volume, while the entropy of a black hole is proportional to the area of ​​its horizon, that is, the square of the radius.

On the other hand, the radius of the horizon is proportional to the mass of the hole. If the hole swallows any material object, its mass will increase, due to which the radius and, consequently, the entropy will increase.

In the case that Wheeler was talking about, the added entropy of the hole would far exceed the increase in entropy after mixing hot and cold tea. This conclusion saves the second law of thermodynamics.

George Dvali, Professor of Theoretical Physics at New York and Munich Universities. “The space inside a black hole is not empty at all. It is filled with gravitons – quanta of the gravitational field. For a solar mass hole, their number is 1077 – this is only a thousand times less than the total number of atoms in the observable part of the Universe. All gravitons are in a state with the lowest possible energy and therefore constitute a single quantum system, similar to the Bose-Einstein condensate. When a hole absorbs an object, oscillations are excited in the graviton condensate, depending on the structure of the absorbed object. As a result, the information introduced into the hole is simply overwritten on new media, and no paradox arises.”

“The space inside a black hole is not empty at all. It is filled with gravitons – quanta of the gravitational field. For a solar-mass hole, their number is 10 77 – this is only a thousand times less than the total number of atoms in the observable part of the Universe.

All gravitons are in a state with the lowest possible energy and therefore constitute a single quantum system, similar to the Bose-Einstein condensate.

When a hole absorbs an object, oscillations are excited in the graviton condensate, depending on the structure of the absorbed object. As a result, the information introduced into the hole is simply overwritten on new media, and no paradox arises.”

### Classics and quanta

The existence of black holes was originally predicted on the basis of Einstein’s theory of gravity, which does not take into account quantum effects. Bekenstein and Hawking used quantum physics to analyze processes near the horizon of a black hole, solving the Wheeler riddle.

However, a new paradox has arisen that touches the very foundations of quantum mechanics. Let the hole swallow an object that has a certain structure (and the structure carries information). The hole turns this object into thermal radiation, which does not carry any information.

That is, information disappears, which contradicts the quantum postulates. The information paradox of black holes was first recognized in the mid-1970s. In the late 1990s, such famous scientists as Stephen Hawking, Kip Thorne and John Preskill dealt with this topic.

However, perhaps there really is no paradox. In any case, George Dvali, professor of theoretical physics at New York and Munich Universities, and his Madrid colleague Caesar Gomez think so. Together with their students, they built a microscopic model of information storage inside the black holes of our world.

It may seem that the information locked in the hole is lost to the outside world, and in this sense the paradox remains. However, it follows from the theory of Dvali and Gomez that this is not the case. The vibrations of the graviton condensate change the spectrum of Hawking radiation, and it ceases to be purely thermal.

In deviations from the thermal spectrum, information is stored that an external observer can, in principle, read and decipher. It is very important that the time required for this is always less than the total lifetime of the hole.

In 1974, Stephen Hawking, using a quantum approach, predicted that black holes are not so black after all: they should emit black-body thermal radiation that arises in the vicinity of the horizon due to interactions of vacuum fluctuations with a gravitational field.

The spectrum of this radiation depends on temperature and therefore reacts to any ingress of matter from the surrounding space. An external observer can notice a change in the spectrum and thus register an increase in the temperature of the hole and, consequently, an increase in its entropy.

Due to Hawking radiation, black holes lose mass (“evaporate”) and eventually die, but the lifetime of astronomical holes is tens of orders of magnitude longer than the current age of the Universe. Thus, black holes can be accumulators of information of monstrous capacity.

The vibrations of the graviton condensate are not washed out and do not decay for such a long time that they persist almost forever. A super-civilization can use black holes for absolutely reliable storage of any amount of information. Who knows – perhaps there are holes in the Universe that preserve information about long-dead worlds and their inhabitants.

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