When it comes to black holes, the first thing people think about is that they can swallow all the gravity. Imagine how terrible and desperate it would be to encounter black holes while traveling through interstellar. However, for the “Grottoes” that even light cannot escape, scientists want to “extract” energy from it for my use. Recently, an international team of researchers has tried to solve the problem that has plagued scientists for more than half a century through physical experiments – can we get energy from black holes? The results of the study have been published in the Journal of natural physics recently. In 1969, Roger Penrose, a British mathematical physicist, proposed a bold guess to obtain energy from black holes, known as the Penrose process. Black holes are actually a large family, which can be divided into different types according to different classification criteria. According to the three parameters of black hole, namely, the schwarzey black hole, which is free of charge and does not rotate, lesner black hole, with charge but not rotating, Kerr black hole, rotates but does not have charge; Kerr Newman black hole can be both charged and rotated. The Penrose process is aimed at the two types of black holes, namely, rotating black holes. “The Penrose process is to get energy by dropping an object into the energy layer of a black hole.” Goulijun, a researcher at the National Observatory of the Chinese Academy of Sciences, said in an interview with the science and technology daily. The energy layer is a special structure of a rotating black hole, which is located outside the boundary of the black hole, the event horizon. The energy layer has an amazing property that there can be negative energy particles in the energy layer, which is opposite to the direction of black hole rotation. Gouli explained that in Penrose’s process, objects or particles thrown into the energy layer were split into two under certain conditions, one absorbed by black holes, and the other escaped black holes. Energy is conserved. In view of the characteristics of energy layer, if the absorbed material energy is negative, the escaping material energy will be higher than that at the beginning. That means that we get energy from black holes. “< p > P > the energy extracted by Penrose process is derived from the rotational energy of the black hole.” Yuan Yefei, a professor of astronomy at the University of science and technology of China, told the science and Technology Daily that the escape material energy will increase and the energy of black holes will inevitably decrease. In fact, the black hole will rotate slowly and the rotating energy will be lost. It can be predicted that the direction of rotation of the inhaled material will be opposite to that of the black hole. The black hole is not a mouse in the laboratory, so it can not be studied in a simple way. So the Penrose process has always been a guess, and no one can say if this crazy idea can be realized. In 1971, two years after the Penrose process was proposed, Soviet physicist zeldovic proposed a possible test method. He suggested that a cylinder of material that can absorb energy be used to simulate a rotating black hole and then emit light waves to it. He predicted that light waves would be “amplified” by the cylinder, that is, the rotating metal cylinder would absorb the negative energy of light waves. After hitting the cylinder, the frequency of the emitted light wave would increase, and the total radiation energy would increase, that is, the so-called SUPERRADIATION. “< p > < p > if this is to be achieved, the cylinder must be rotated at a rate sufficient to be at least equal to the frequency of the incident light.” Yuan further explained that the frequency of light waves is generally megahertz (MHz) or gigahertz (GHz). This means that the cylinder will rotate one million or even one billion revolutions in a second, which is impossible for the real mechanical motor. In this latest study, researchers skillfully use sound waves instead of light waves to simulate this experiment. The radiated sound waves are indeed “amplified” and the energy increased by more than 30%. Yuan told reporters that this is because of the wide range of frequencies of sound waves, researchers can choose far lower frequency than light waves, so that the “black hole alternative” speed can be reduced to the speed that can be achieved artificially. “The study is actually simulating the physical nature behind the Penrose process, which does not mean that the Penrose process can be realized. Because black holes are so far away from us that they cannot be tested in the existing conditions. ” Yuan said. Curiosity and imagination are the wings of science development. Although the Penrose process is not yet verified, it can not stop scientists from pursuing the energy of “extracting” black holes. One is to extract the rotational energy of black holes. Of course, this idea is about rotating black holes. According to the law of conservation of energy, if we get energy successfully, the speed of black hole will decrease and lose some of the rotating energy, just like Penrose process. Another way of thinking is to extract the gravitational potential energy of black holes. This idea does not require the type of black hole, because all black holes have huge gravity. In daily life, if an object is thrown from a high building, the object will be faster and faster, which is a common example of the transformation of gravitational potential energy into kinetic energy of objects. The same is true of black holes. If the gas in plasma body is thrown into the black hole, as the distance from the black hole is closer and closer, the gas will move faster and faster. Particles in the plasma collide with each other, thus heat and radiate photons carrying energy. The process of energy extraction is actually that the gravitational energy of black hole is converted into kinetic energy of object, then into heat energy, and energy is “transported” from black hole. This is the energy source of accretion disk radiation around black holes as we usually know. Yuan Yefei added that the energy extraction rate of black hole gravitational energy is estimated to be about 5.7%. Don’t think this is very efficient, but it is important to know that the energy people have extracted from fusion is only 0.7%. According to Einstein mass energy equation, the energy obtained by 1 g of matter transferred through the gravitational energy of black hole is 5.7% higher than that of the static mass, which is very considerable. “In the vast universe, there are countless black holes. Previously, scientists have estimated that the number of black holes with a mass greater than 10 times the mass of the sun should be more than 100 million. If you can transform these black holes into energy supply stations, it will be a very shocking thing The army was deeply moved. Imagine that, in a long interstellar journey, people are on the verge of despair because of the fuel shortage, and suddenly find a black hole nearby. Fear will be turned into joy at this time – energy issues are solved, and the spacecraft “full of blood is resurrected” and goes further into space and more unknown! However, the ideal is full and the reality is very bone. Due to the limitation of many practical conditions, the idea of “black hole energy station” can only be kept in the science fiction world. First, “we don’t have a high-resolution telescope that can carefully observe black holes. If the nature of the object is not clear, what to use. ” “Said Gou Li Jun. “Black holes are very far away from us. It is only a concept to use this remote object to generate electricity. It is difficult for us to design a specific method and process.” Yuan Yefei admitted. But the future is always full of unknown, just as the dream of flying in ancient times has become a reality in modern times. “Many times, science fiction will bury a seed for science, and we look forward to it to take root and sprout in the future.” “Said Gou Li Jun. Spontaneous combustion at a Guangzhou Motor vehicle intersection and other traffic lights in Shenzhen