In the era of "big data", humanity begins to generate huge amounts of information. And where can the accumulated knowledge of supercivilization be stored?
Sometimes remarkable discoveries owe their origin to ordinary … chatter. This turned out to be the result of a conversation between American physicist John Wheeler and his graduate student Jacob Bekenstein back in 1970. Mixing hot tea with cold tea, Wheeler reasoned, produces a liquid with an intermediate temperature. The thermal motion of water molecules is chaotic, and the degree of this chaos increases with increasing temperature. To measure randomness, a special quantity is used - entropy. The entropy of two poured 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 for the outside world. And in this case, the second law of thermodynamics is violated.
Save the Universe
Bekenstein tried to argue and two years later showed that the outer boundary (horizon) of the black hole behaves like a heated black body. Therefore, a hole can be assigned a nonzero temperature and, therefore, 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, which will increase the radius and, consequently, the entropy. In Wheeler's case, the added entropy of the hole would far exceed the increase in entropy after mixing hot and cold tea. This conclusion is saved by the second law of thermodynamics.
Georgy Dvali, professor of theoretical physics at New York and Munich universities. “The space inside the black hole is not empty at all. It is filled with gravitons - quanta of the gravitational field. For a hole of solar mass, 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, analogous to the Bose-Einstein condensate. When a hole absorbs an object, vibrations are excited in the graviton condensate, depending on the structure of the absorbed object. As a result, the information brought into the hole is simply rewritten on new media, and no paradox arises."
“The space inside the black hole is not empty at all. It is filled with gravitons - quanta of the gravitational field. For a hole of solar mass, 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, analogous to the Bose-Einstein condensate. When a hole absorbs an object, vibrations are excited in the graviton condensate, depending on the structure of the absorbed object. As a result, the information brought into the hole is simply rewritten on new media, and no paradox arises."
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Classics and quanta
The existence of black holes was originally predicted based on Einstein's theory of gravitation, which ignores quantum effects. Bekenstein and Hawking used quantum physics to analyze processes near the black hole horizon, solving the Wheeler puzzle. However, a new paradox emerged, affecting the very foundations of quantum mechanics. Let the hole swallow an object with a certain structure (and the structure carries information). The hole turns this object into thermal radiation, which carries no information. That is, information disappears, which contradicts quantum postulates. The information paradox of black holes was first realized back in the mid-1970s. In the late 1990s, famous scholars such as Stephen Hawking, Kip Thorne, and John Preskill were working on this topic. But even after heated discussions, the question of information destruction in a black hole remained open. However, perhaps, in fact, there is no paradox. In any case, this is the opinion of the professor of theoretical physics at New York and Munich Universities Georgy Dvali and his Madrid colleague Caesar Gomez. 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 persists. However, from the theory of Dvali and Gomez it follows that this is not the case. Vibrations of the graviton condensate change the Hawking radiation spectrum, and it ceases to be purely thermal. In deviations from the thermal spectrum, information is stored that an external observer, in principle, can read and decipher. Very important,that the time required for this is always less than the full lifetime of the hole, no matter how much information it swallows.
Hawking radiation
In 1974 Stephen Hawking, using a quantum approach, predicted that black holes are not so black - they should emit thermal radiation of the blackbody type, which occurs in the vicinity of the horizon due to the interactions of vacuum fluctuations with the gravitational field. The spectrum of this radiation depends on temperature and therefore reacts to any ingress of matter from the surrounding space. An outside observer can notice a change in the spectrum and thus register an increase in the hole's temperature and, consequently, an increase in its entropy. Due to Hawking radiation, black holes lose mass ("evaporate"), and eventually die, but the lifetime of holes of astronomical scales is tens of orders of magnitude longer than the present age of the Universe.
Due to the quantum fluctuations of various fields in a vacuum, many pairs of virtual particles are continuously born and destroyed, which move in opposite directions (according to the law of conservation of momentum). If such a pair appears on the very horizon, then the “internal” particle will fall into the hole, but the “external” particle, under favorable conditions, can leave. As a result, the hole turns into a radiation source, loses energy and, consequently, mass.
In 1974 Stephen Hawking, using a quantum approach, predicted that black holes are not so black: they should emit blackbody-type thermal radiation that occurs in the vicinity of the horizon due to interactions of vacuum fluctuations with the gravitational field. The spectrum of this radiation depends on temperature and therefore reacts to any ingress of matter from the surrounding space. An outside observer can notice a change in the spectrum and thus register an increase in the hole's temperature and, consequently, an increase in its entropy. Due to Hawking radiation, black holes lose mass ("evaporate") and eventually die, but the lifetime of holes on astronomical scales is tens of orders of magnitude longer than the present age of the Universe. Thus, black holes can be enormous storage capacity. The vibrations of the graviton condensate do not blur and do not damp for so long that they persist almost forever. Supercivilization can use black holes to store any amount of information absolutely securely. Who knows - maybe there are holes in the Universe that preserve information about long-dead worlds and their inhabitants.
Alexey Levin