What is a black hole?

A black hole is an area in time and space from which even light cannot escape. The mass of a black hole is unimaginable, which makes the gravitational field so strong that once any matter and radiation enter the region, they can never get out, and even the fastest light can't escape from it, so people can't see it. Because it is similar to a blackbody that does not reflect light at all in thermodynamics, American physicist Wheeler gave it an interesting name "black hole".

The formation process of black holes?

When a star ages, its thermonuclear reaction will exhaust the fuel (hydrogen) in the center, and the energy generated in the center is not much. In this way, it is not strong enough to bear the huge weight of the shell. Therefore, under the heavy pressure of the shell, the core began to collapse, until finally a small and dense star was formed, which could balance the pressure again. Thereby forming a denser celestial body, and the high temperature and high pressure generated by it can press all electrons into the nucleus.

When the mass of an object is M3.2m sun, there will be no force that can compete with its own gravity, thus causing another big collapse. According to scientists' guesses, matter will move inexorably towards the central point until it becomes a "point" with zero volume and infinite density. When its radius shrinks to a certain extent (schwarzschild radius), the huge gravity makes it impossible to shoot out even light, thus cutting off all the connection between the star and the outside world-a "black hole" was born.

Scientists generally believe that supernova explosion in astronomical observation is one of the important ways to produce black holes. Supernovae were called guest stars in ancient China. This star suddenly appeared in the starry sky, and then suddenly disappeared after a while, visible to the naked eye. Because it comes and goes without a trace, it is called a guest star, like a distant visitor, who lives for a while and then returns to a distant place.

Black holes have strong gravity, constantly devouring a lot of interstellar matter; Some substances run around it quickly, and the trajectory will change, forming a circular material ring; There is huge energy radiation around, constantly emitting extremely strong X-rays and γ-rays. In addition, the huge gravity of the black hole makes the light bend strongly near it; There is not even a ray of light in it.

Interesting Paradox of Black Hole Information

Hawking expounded the black hole in a paper from 65438 to 0976: Because pure thermal radiation can hardly bring any information, if the black hole really radiates to the end and all of it is converted into heat, the information brought in by the matter that forms the black hole will disappear from the universe. In other words, the black hole radiation does not contain any information inside the black hole. After the black hole is completely lost, all information will be lost. This will not only destroy the conservation of physical laws such as lepton number and baryon number, but also make the theory of quantum gravity that is being created not meet the conservation of unitary and probability, which is the "black hole information paradox".

The significance of studying black holes

At present, there are two pillar theories in modern physics. One is general relativity, which mainly describes the interaction among macroscopic objects, space-time and matter. The other is quantum theory, which describes the laws of motion in the micro-world. In general physics research, these two theories do not interfere with each other. However, in order to make physics continue to develop, we must combine these two theories and finally get a unified theory. Black hole is a celestial body that has some characteristics of macroscopic object morphology and microscopic quantum theory. It can be said that the two theories meet on this celestial body. So studying black holes can promote the development of two theories.