Why did Hawking say that black holes don't exist?

Being around is like a deep well, I don't know where the bottom of the black hole leads, only know that the journey ahead is the stars and the sun. Haruki Murakami

Today, we will talk about some common problems about black holes, from shallow to deep. I hope this article will help you understand and understand black holes. What is a black hole?

our definition of a black hole is actually very simple at first, which mainly refers to a space area from which no matter, even light, can escape. This space area is a black hole, and the edge of this area is called? Event horizon? Any substance or information that falls into the visual interface will fall into the center of the black hole and will never escape, which means that the information inside and outside the visual interface is completely disconnected, so it is impossible for us to know what is happening inside and what is inside will never come out.

However, Hawking put forward the theory of black hole radiation according to quantum fluctuations in vacuum, arguing that black holes are slowly releasing energy and losing mass, so when a black hole disappears completely, all the information of the substances that fell into the black hole before will be lost. This is the paradox of black hole information loss, which is inconsistent with the information conservation thought by quantum mechanics.

Hawking immediately suggested (this is his guess, but it has not been confirmed) that the information between the black hole and the outside world is only temporarily disconnected, which is called? Apparent horizon? This? Apparent horizon? It will disappear in the future, and the information trapped in the black hole will not be lost, and it will return to the universe, but this temporary isolation may be even older than the universe, which means that the difference between complete disconnection and temporary disconnection cannot be observed. Personally, I think Hawking is talking nonsense!

how big is the black hole?

We can imagine a black hole as a sphere, and its diameter is directly proportional to the mass of the black hole, that is, the more mass that forms a black hole at first or falls into the black hole later, the larger the black hole volume. But compared with celestial bodies of the same mass, black holes are still very small. This is because the black hole has compressed its mass to a very small volume under the great gravity. For example, a black hole with the mass equivalent to that of the earth has a radius of only a few millimeters, and the radius of the earth is about 1 billion times that of a black hole with the same mass.

the radius of a black hole is called schwarzschild radius, which is expressed by Karl? Named after Schwarzenegger. Because of Carl? Schwarzschild first proposed black holes as the solution of Einstein's general theory of relativity. But don't forget that there are tens of billions of times the mass of the sun in the universe, and these black holes are still very large.

what happens when you fall into the viewport?

When approaching a black hole, we will see that the background starlight is severely distorted. However, if there is no starlight in the background area where the black hole is located, we will not see any changes in the surrounding environment when approaching the black hole or even crossing the visual interface. You don't even know that you are falling, accelerating or being influenced by gravity. This is because of an inference of Einstein's equivalence principle.

We can't tell the difference between the acceleration in a flat space and the gravitational field that leads to the curvature of the space. Because there is no starlight in the background of the black hole, it is all black, and we can't even find a reference system to tell us that it is accelerating.

However, if an observer who is far away from the black hole sees someone fall into the black hole, he will notice that the closer he is to the visual interface, the slower he moves. Because the time near the black hole horizon is much slower than the time away from the black hole horizon. But for people who fall into a black hole, they will cross the visual interface in a short time.

Another point is that the experience of people falling into a black hole on the visual interface depends on the tidal force of the gravitational field. The tidal force on the apparent interface is inversely proportional to the square of the mass of the black hole. That is, the greater the mass of a black hole, the smaller the tidal force. If the mass of the black hole is large enough, it will not have any influence on us, and we can safely cross the visual interface. If the tidal force is large enough, the head and feet will feel a huge gravitational difference, and our bodies will be stretched. What is the technical term in physics? Pasta? .

what's in a black hole?

No one knows about this problem, but it is almost certain that what is inside a black hole is by no means any material form we have ever seen. In the language of general relativity, there is a singularity inside a black hole, a point where gravity becomes infinite. Once any object crosses the visual interface, it will quickly hit the singularity, but general relativity can't tell us what the singularity is, and it also collapses at the singularity, which means it is not applicable and understandable.

what we need is a quantum gravity theory. It is generally believed that this theory will replace the singularity with something else.

how are black holes formed?

we know that black holes may form in four different ways. The easiest to understand is the stellar collapse type black hole. A star with enough mass will collapse to form a black hole after the nuclear fusion stops, because when the radiation pressure generated by the fusion stops, the matter will start to fall to its own gravity center, and the density will increase. Finally, nothing can overcome the gravity on the surface of the star, so a black hole is created. These black holes are called? Stellar mass black hole? , is the most common black hole.

what is the next common type of black hole? Supermassive black hole? It is usually located in the center of a galaxy, and its mass is about billions to tens of billions times that of a solar mass black hole. To be precise, the formation of these supermassive black holes is not completely clear at present. However, we generally think that they were originally a stellar-mass black hole, and they grew into supermassive black holes by merging with each other and devouring other stars in the center of galaxies with dense stars and black holes.

The more controversial view is primitive black holes, which were probably formed under high-density fluctuations in the early universe. Although this is possible, it is difficult to find a model that can produce primitive black holes without forming too many primitive black holes.

finally, there is a very speculative black hole, that is, a tiny black hole with the mass similar to the Higgs boson can be produced in the Large Hadron Collider. This situation only works if there are extra dimensions in our universe. But so far we haven't found any extra dimensions.

how do we know the existence of black holes?

We have a lot of observational evidence about black holes from theory to reality. At first, we discovered black holes through gravity. For example, in the center of the Milky Way, we found that a large number of stars are running at high speed around a non-luminous point. According to the gravitational theorem, we can know that the mass of this central point is millions of times that of the sun.

Like the massive black holes in the center of some galaxies in the universe, due to their unusual activity, some observable optical effects can be produced. For example, after accretion, the black holes will radiate X-rays in the accretion disk, and an obvious radio source will be formed in the center. It is by using these properties of black holes that we obtained the first black hole photo in history.

Why did Hawking once say that black holes don't exist?

This sentence is a bit out of context. In fact, what Hawking wants to express is not here. Black holes are real. What he wants to say is that he thinks that a black hole does not have an eternal event horizon, but a short apparent horizon, in order to solve the problem of information loss of black holes. But this is what he guessed.

how does a black hole emit radiation and lose its mass?

black holes emit radiation through quantum effects. It should be noted that this is the quantum effect of matter, not the quantum effect of gravity. Quantum mechanics holds that the vacuum is not empty, and there are positive and negative virtual particle pairs in a very short time, and the energy is returned to the universe. However, if this quantum effect occurs at the edge of the black hole's visual interface, one of the virtual particles will fall into the black hole, while the other virtual particle will steal energy from the black hole, become a real particle and escape, and annihilate nearby anti-real particles to release energy.

the radiation emitted by a black hole was originally emitted by Stephen? Hawking put forward, known as? Hawking radiation? . The radiation temperature is inversely proportional to the mass of the black hole. The smaller the black hole, the higher the radiation temperature. As far as we know, the radiation temperature of stars and supermassive black holes is much lower than that of cosmic microwave background radiation, so it is impossible to detect such effects at all. It is no exaggeration to say that we humans may not be able to verify Hawking's statement in the future. What is the paradox of information loss?

The paradox of information loss is caused by Hawking radiation. This radiation is a purely thermal process, which means that the radiation is completely random except for a specific temperature. Moreover, these radiations don't contain any information about the formation of black holes and objects that have fallen into black holes before, but when a black hole emits radiation, it will lose its mass and gradually shrink. Eventually, the black hole will be completely transformed into random radiation. That is, information about how the black hole formed before and the objects falling into the black hole will be lost, but quantum mechanics does not allow this to happen.

Therefore, the evaporation of black holes is inconsistent with the quantum theory we know, and we must make some concessions. This inconsistency must be eliminated in some way. Most physicists believe that the solution is that Hawking radiation must contain this information in some way, or this information can escape from the black hole in other ways.

how to solve the problem of black hole information loss?

This is a frontier problem in physics, and it can't be falsified by science. Many hypotheses have been put forward, such as: black holes may be connected by white holes in another dimension, and the material information entering from black holes will be spit out from the white holes; And the black hole is actually the entrance of a wormhole, which connects with another time and space, and material information can also come out. These are completely beyond the scope and ability of our human beings to verify and observe. At present, these speculations are meaningless.

Moreover, in order to fill his hole, Hawking suggested that black holes actually have a way of storing information, which has been neglected before. In fact, material information is stored in the event horizon of the black hole, which can cause tiny movement of particles in Hawking radiation. In these small changes, there may be information about disappearing substances. It's mysterious, but it can't be confirmed.

These are some questions about black holes. At present, we can be sure that black holes exist. We can find them in the universe, and we also know how they formed and finally disappeared. However, the specific destination of the information entering the black hole remains to be studied!