According to the previous explanation, he didn't feel anything special at first, even if he fell and crossed the invisible boundary-the event horizon of the black hole. But then, after a few hours, days or even weeks (as long as the black hole is big enough), he will feel that the gravity on his feet is greater than that on his head. He continued to fall and was ruthlessly taken to the depths of the black hole. The giant gravity difference tore his body to pieces. Eventually, his body will fall to the core of a black hole with infinite density.
But Bohr kinski's calculations show that this is not the case. Two of his students, Ahmed alm and James Sully, and his colleague Donald Marolf, a string physicist at the University of California, Santa Barbara, also participated in the calculation. In their results, the quantum effect will turn the event horizon of the black hole into a vortex formed by the flow of hot particles. Anyone who falls into the horizon of a black hole will encounter a wall of fire and be burnt to a scorched earth immediately.
In July 20 12, they published this result, which shocked the physics community. Because it violates the basic physical principle-equivalence principle, which was put forward by Einstein as early as a century ago as the basis of general relativity. According to the equivalence principle, under the action of gravity, the phenomenon seen by the falling observer is exactly the same as that seen by the observer floating in empty space, even in such a strong gravitational field inside the black hole. Without this basic principle, Einstein's theoretical framework would collapse.
Bohr kinski and his collaborators knew what this result meant, so they gave another possible result, that is, the fire wall could not be formed. However, this scheme also needs to pay a "high price", that is, physicists must give up another important pillar of physics-quantum mechanics. However, in the theory describing subatomic particle interaction, quantum mechanics is absolutely dominant.
This result of Bohr kinski led to a series of discussions on firewalls and a large number of related research papers. Every newspaper tries its best to get rid of the above deadlock, but none of them can satisfy everyone. Steve Giddings, a quantum physicist at the University of California, Santa Barbara, believes that "revolutionary theories are needed to solve the crisis facing the foundation of physics".
Troubled by this problem, experts studying black holes gathered in CERN, Geneva, Switzerland in April 20 13 to solve this problem face to face. They hope to find a unified theory that leads to "quantum gravity". This unified theory can unify all the basic forces of nature, which physicists have dreamed of for decades.
Raphael Bousso, a string physicist at the University of California, Berkeley, opened the report of this conference in this way: the view of fire wall "has shaken the theoretical basis of black holes that most people think. It fundamentally points out that the contradiction between quantum mechanics and general relativity does not indicate which direction to go next. "
Hawking's gambling
The firewall crisis can be traced back to 1974. At that time, Hawking, a physicist at Cambridge University in England, confirmed that quantum effects can make black holes have temperature. Even if it is completely isolated from the outside world, the black hole will slowly emit thermal radiation-that is, photons or some particles, gradually reducing its mass until it completely evaporates (see figure).
Of course, these particles cannot form a wall of fire, and astronauts who fall across the horizon will never notice this radiation, because the difference caused by relativity is quite small. But Hawking's results are still surprising-especially the equation of general relativity tells us that black holes will only devour matter and grow, but will not evaporate.
Hawking's conclusion basically shows that the "vacuum" in the world of quantum mechanics is not empty, but can be verified by observation. On the microscopic scale of the quantum world, the world is in eternal chaos, and particles and corresponding antiparticles are always producing, recombining and annihilating. Only in very fine experiments can this micro-scale chaos have an observable effect. Hawking noticed that when a particle-antiparticle pair happens to be produced on the surface of the black hole horizon, one particle will fall into the black hole horizon before recombination, and the rest will move outward as radiation. The swallowed particles carry negative energy-this is allowed by quantum theory, which only balances the positive energy taken away by radiation. The negative energy of particles will be deducted from the mass of the black hole, resulting in the shrinking of the black hole.
Hawking's initial analysis was later improved and expanded by many researchers, and his conclusion was widely accepted. But at the same time, the puzzling contradiction between black hole radiation and quantum theory has gradually surfaced.
Quantum mechanics believes that information cannot be destroyed. In principle, by measuring the quantum state of radiation particles, we can get all the information of objects falling into black holes. However, Hawking proved that the fact is far from simple: the escaping radiation is random. Whether you throw a kilo of stones or a kilo of computer chips, the result is the same. Even though we have been observing the disappearance of black holes, we can't know how black holes are formed and what objects fall into them.
This problem is called the information paradox of black holes, which divides physicists into two camps. One, like Hawking, thinks that when a black hole dies, all the information really disappears. If this goes against the principle of quantum theory, we need to find a better theory. Another, like John Preskill, a quantum physicist at the California Institute of Technology, is trapped by quantum mechanics. "I'm trying to build a theory that includes information loss," he said, "but I can't find a theory that makes any sense-no one can do it." The deadlock lasted for 20 years until 1997 put forward a famous conjecture. At that time, Preskill was betting with Hawking that the information would not be reduced, and the loser would buy a set of encyclopedias designated by the other party.
That year, the discovery of physicist juan maldacena, who was still at Harvard University, broke the deadlock. Marda Sinar's discovery is based on an earlier theory that any three-dimensional region in our universe can be described by the information contained in the two-dimensional boundary, just as laser can store three-dimensional images on a two-dimensional hologram. "We can use holograms as symbols," said Leonard Susskind, a string physicist at Stanford University, who was one of the first people to put forward this idea. He also said, "After doing more calculations, we found it meaningful to regard the universe as the projection of information on the boundary surface."
Marda Sinar expressed the hologram with concrete mathematical formula. This formula uses superstring theory, which regards elementary particles as tiny energy rings that keep vibrating. In his model, the three-dimensional universe containing strings and black holes is only dominated by gravity, and the basic particles and fields on the two-dimensional boundary surface follow the general laws of quantum mechanics and are not affected by gravity. Assuming that the boundary is infinite, creatures in three-dimensional space can't see the boundary, but it doesn't matter. Anything that happens in the three-dimensional universe can be well described by equations in the two-dimensional universe, and vice versa. Marthe Sinar said, "I found a math dictionary. With this dictionary, we can switch back and forth between the languages of the two worlds. ".
This means that even the evaporation of a three-dimensional black hole can be described in a two-dimensional world with no gravity, quantum mechanics first and information never decreasing. If information is conserved in the two-dimensional world, so is it in the three-dimensional world. Therefore, information must somehow escape from the black hole.
Relativity or quantum mechanics?
A few years later, Marrol's husband proved that every model of quantum gravity theory abides by the same rules, whether starting from string theory or not. Ted Jacobson, a quantum physicist at the University of Maryland, College Park, said, "The work of Marthe Cynar and Marrol changed my mind. For a long time, he always thought that the amount of information would decrease. In 2004, Hawking publicly admitted that he was wrong and kept his promise to give Preskill an encyclopedia of softball.
Marthe Sinar's findings are convincing. Although no one can explain how Hawking radiation takes away information, most physicists have begun to believe that the contradiction has been solved. Bohr kinski said, "I think everyone guessed there would be a straightforward explanation." .
But this is not the case. When Bohr kinski and his team began to solve the following problems in depth at the beginning of 20 12, they were quickly stumped by another contradiction, which eventually led them to a deadly fire wall.
Hawking has proved that the quantum state of any particle escaping from a black hole is random, so the particle will not bring out any useful information. However, in the mid-1990s, Suskind and others realized that if the particles radiated by a black hole were in entangled state, the information of the black hole might be encoded in the quantum state of these particles as a whole. Entanglement means that no matter how far apart a pair of particles are, the measurement of one particle will immediately affect the other particle.
But what puzzles the Bohr kinski team is, how is this possible? Any particles radiated must be related to the other half entering the black hole. If Suskind and others are right, then this particle must also be related to the previously radiated particles (because the black hole information is encoded in all radiated particles). This means that the irradiated particles are entangled with the particles falling into the black hole and the previously irradiated particles. But the strictly proved "monogamous quantum correlation" tells us that a quantum system cannot be completely entangled with two independent systems at the same time.
In order to avoid this contradiction, Bohr kinski and his collaborators realized that one of the two kinds of entanglement must be cut off. Unwilling to give up the entanglement of information encoded in Hawking radiation, they decided to cut off the connection between escaping particles and falling particles. But there is a price to pay. "This is a violent process, just like the breaking of molecular bonds will release energy," said Bohr kinski. When a pair of particles are decomposed, a lot of energy is released. The horizon of the black hole will become a ring of fire, and any falling matter will be burnt. In this way, the above results violate the equivalence principle and its inference, that is, the observer in free fall feels the same as the observer floating in empty space-how can the former feel the same when it is burned to ashes? Therefore, they put the paper on the arXiv website, and let physicists make a choice: either accept the existence of the fire wall, the general theory of relativity does not hold, or admit that black holes can lose information and quantum mechanics is wrong. Marrol said, "In our view, at least the firewall theory is crazy".
This paper can be said to be "a stone stirs up a thousand waves" in physics. "It is simply unacceptable that it should claim that giving up the equivalence principle of general relativity is the best choice," Jacobson said. Busso held a similar opinion and added, "A fire wall can't exist, just as you stand in an open field, a brick wall won't suddenly appear out of thin air and hit you in the face." If Einstein's theory is not applicable to the black hole horizon, cosmologists must test its universality.
Bohr kinski admits that he may have made some low-level mistakes. So he turned to Suskind, one of the founders of holographic theory, to help him find out his mistakes. "My first reaction was that their results might be wrong," Suskind said. But after careful consideration, he wrote in an article posted on the Internet: "My second reaction is that they are right, the third reaction is that they are still wrong, and the fourth reaction is that they are still right, which brings me a nickname-'yo-yo', but my reaction is exactly the reaction of most physicists."
Since then, more than 40 articles have been published on arXiv, but so far, no one has found any logical defects in the Bohr kinski Group. "This is really a beautiful job, which points out that our understanding of black holes cannot be justified," said Don Page. Page is now in university of alberta and worked with Hawking in the 1970s. However, many creative solutions have been proposed.
Confrontation with Einstein
In Saskind's view, the solution proposed by Daniel Harlow, a quantum physicist at Princeton University in the United States, and Patrick Hayden, a computer scientist at McGill University in Canada, is the most likely. They considered whether astronauts can use real-world means to detect the possibility of the contradictions discussed above. In order to do this, astronauts must first "decipher" a considerable proportion of Hawking radiation, and then jump into the black hole to detect falling particles. The calculation of particle pairs shows that the information in radiation is so difficult to decode that the astronauts are not ready to jump into the black hole, and the black hole evaporates. In theory, there is no basic theory that this contradiction is undetectable, but in fact, such detection is impossible.
However, Giddings believes that the contradiction between fire and wall needs a fundamental solution. He calculated that if the entanglement between particles radiated by Hawking and those swallowed by a black hole is broken only after the former escapes from the horizon of the black hole for a certain distance, less energy will be released, so a fire wall will not be formed. This explanation protects the equivalence principle, but it needs to make some amendments to the quantum theory. Because Giddings's model has the possibility of verification, scientists are interested in this model at CERN meeting: the model predicts that when two black holes merge, it will cause huge ripples in time and space, which can be detected by gravitational wave detectors on the earth.
There is another way to save the equivalence principle, but it is controversial and few people dare to support it: maybe Hawking is always right and the information is really lost in a black hole. Ironically, at the conference on fire wall held by Stanford University at the end of 20 12, the scientist who supported this idea was Preskill who had made a bet with Hawking. "Strangely, this method is not as crazy as firewall theory, but people have never seriously considered it," Preskill said, although he stressed that intuitively he would prefer information to stay.
From the point that physicists are unwilling to re-examine Hawking's past, we can see that they have great trust in Marda Sinar's Mathematical Dictionary. This "mathematical dictionary" linking gravity and quantum theory seems to indicate that information will not be lost. Bohr kinski compared Marda Sinar's theory (which has been cited 9 000 times) with19th century electromagnetic theory which unified light, electricity and magnetism, and thought that the former was the deepest understanding of gravity so far, and it could link gravity with quantum field theory. Busso thinks, "If the idea of firewall was put forward in the early 1990s, I think it would be strong evidence of information loss, but now no one wants to consider the possibility that Marda Sinar made a mistake".
In this direct confrontation with Einstein, most physicists are willing to support Marda Siner, which makes Marda Siner feel extremely honored. He said, "In order to understand the contradiction between fire and wall more thoroughly, we need to enrich the content of the' Mathematical Dictionary', but there is no need to abandon it."
So far, the only understanding that scientists have reached is that this problem will not be solved soon. In the meeting on firewall at the end of 20 12, Bohr kinski listed all the papers that tried to overthrow the firewall theory, and pointed out the loopholes of these papers one by one. Finally, he said, "It's a pity that none of these papers are valid, but we need to keep working hard."