A black hole is a singularity with infinite density, infinite height curvature of space-time, infinite volume and infinite heat, and it is invisible in the center and part of the surrounding sky.

Black holes are celestial bodies existing in space in modern general relativity. The gravity of a black hole is so great that the escape velocity in the event horizon is greater than the speed of light.

19 16, the German astronomer karl schwarzschild got the vacuum solution of Einstein's gravitational field equation by calculation. This solution shows that if a large number of substances are concentrated in a space, there will be a strange phenomenon around it, that is, there is an interface around the particles-once the "horizon" enters this interface, even light cannot escape. This "incredible celestial body" was named "black hole" by American physicist john archibald wheeler.

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The process of a black hole is similar to that of a neutron star: a star is preparing to die, and its core rapidly contracts, collapses and explodes under its own gravity. When all the core materials become neutrons, the contraction process stops immediately and is compressed into dense stars, and the inner space-time is also compressed.

However, in the case of a black hole, because the mass of the star core is so great, the contraction process goes on endlessly, and even the repulsive force between neutrons can't stop. Neutrons themselves are ground into powder under the attraction of squeezing gravity itself, and the rest are substances with unimaginable density.

Due to the gravity generated by high mass, anything near it will be sucked in by it. When a star ages, its thermonuclear reaction has exhausted the fuel in the center and the energy generated in the center is running out.

In this way, it no longer has enough strength to bear the huge weight of the shell. Therefore, under the heavy pressure of the shell, the inner core begins to collapse, and the matter will move inexorably to the center, until finally a star with nearly infinite volume and density is formed.

After a long period of speculation, the definition of black hole has been gradually accepted by people. However, Hawking denied the existence of black holes at the beginning of this year, and instead put forward the theory of "grey holes", which caused quite a stir in physics.

Today, Mercini Horton bluntly said that "there is no such thing as a black hole", which undoubtedly became a blockbuster again-although Mercini Horton's fame is far less than Hawking's. Of course, it is not so easy to overthrow the existing theory by our own efforts, and more convincing evidence is needed to support it.

Scientists believe that black hole engines are driven by magnetic fields. With the help of the horizon telescope, astronomers have detected the magnetic field outside the horizon of the supermassive black hole in the center of our galaxy.

It is found that some areas near the black hole are chaotic, with chaotic magnetic circles and eddies, just like spaghetti mixed together. On the contrary, the magnetic field in other areas is much more orderly, which may be the area where the material jet is produced.

It is also found that the magnetic field around the black hole will change obviously in a short time of 15 minutes. Reference link: Baidu Encyclopedia-Black Hole.

What is a black hole?

General relativity is a theory of gravity founded by Einstein, which is applicable to planets, stars and "black holes".

This theory put forward by Einstein in 19 16 shows how space and time are distorted by the existence of massive objects. In short, general relativity says that matter will bend space, and the bending of space will in turn affect the motion of objects passing through space.

Let's see how Einstein's model works. First of all, consider that time (the three dimensions of space are length, width and height) is the fourth dimension in the real world [2] (although it is difficult to draw another direction beyond the usual three directions, you can try to imagine it).

Secondly, consider that time and space is the bed surface of a huge taut spring bed for gymnastics performance. Einstein's theory holds that mass bends time and space.

We might as well put a big stone on the bed surface of the spring bed to illustrate this scene: the weight of the stone makes the tight bed surface sink a little. Although the surface of the spring bed is basically flat, its center is still slightly concave. If more stones are placed in the center of the spring bed, it will have a greater effect and make the bed surface sink more.

In fact, the more stones there are, the more the spring bed surface bends. Similarly, massive objects in the universe will distort the structure of the universe.

Just as 10 stone can bend the spring bed better than 1 stone, celestial bodies with much greater mass than the sun can bend space better than celestial bodies with mass equal to or less than one sun. If a tennis ball rolls on a tight spring bed, it will move in a straight line.

On the contrary, if it passes through a concave place, its path is arc. Similarly, celestial bodies will continue to move in a straight line when crossing the flat area of time and space, while celestial bodies crossing the curved area will move in a curved trajectory.

Now let's look at the influence of black holes on the surrounding space-time. Imagine putting a very heavy stone on a spring bed to represent a very dense black hole.

Stones will naturally have a great influence on the bed surface, which will not only bend and sink its surface, but also cause the bed surface to break. A similar situation can also happen in the universe. If there is a black hole in the universe, the cosmic structure there will be torn apart.

The rupture of this spatiotemporal structure is called singularity or spatiotemporal singularity. Now let's see why nothing can escape from a black hole.

Just as a tennis ball rolls over a spring bed and falls into a deep hole formed by a big stone, an object passing through a black hole will be caught by its gravity trap. Moreover, saving unlucky objects requires infinite energy.

As we have said, nothing can enter a black hole and escape from it. But scientists believe that black holes will slowly release energy.

Hawking, a famous British physicist, proved in 1974 that a black hole has a non-zero temperature, and the temperature is higher than its surroundings. According to the principle of physics, all objects whose temperature is higher than the surrounding environment will release heat, and black holes are no exception.

A black hole will emit millions of trillion years of energy, and the energy released by a black hole is called "Hawking radiation". When a black hole dissipates all its energy, it will disappear.

Black holes between time and space slow down time, make space elastic, and devour everything that passes through it. 1969, American physicist John Artie Wheeler named this insatiable space "black hole".

We all know that a black hole is invisible because it can't reflect light. In our minds, black holes may be distant and dark.

But Hawking, a famous British physicist, believes that black holes are not as black as most people think. Through the observation of scientists, there is radiation around the black hole, and it is likely to come from the black hole, which means that the black hole may not be as black as imagined.

Hawking pointed out that the radioactive material source of black holes is a kind of solid particles, which are produced in pairs in space and do not follow the usual physical laws. Moreover, after these particles collide, some will disappear into the vast space.

Generally speaking, we may not have a chance to see these particles before they disappear. Hawking also pointed out that when black holes are produced, real particles will appear in pairs accordingly.

One of the real particles will be sucked into the black hole, the other will escape, and a bunch of escaped real particles will look like photons. For the observer, seeing the escaping real particles is like seeing the light from a black hole.

When the radius of a star is less than a certain value (called "schwarzschild radius" in astronomy), it will even capture the light emitted from the vertical plane. At this time, the star becomes a black hole.

To say it is "black" means that once anything falls in, it can't escape, including light. In fact, black holes are invisible. (In fact, black holes are not invisible, because "invisible" means that light can pass through objects.

Light cannot pass through a black hole. According to the latest research, scientists believe that black holes may be wormholes leading to other universes.

If this theory is correct, it will help to explain quantum problems such as information paradox of black holes, but critics point out that it will also create new problems, such as how wormholes are formed. A black hole is an object with strong gravity, and no object, even light, can escape after entering its event boundary.

According to Einstein's general theory of relativity, a black hole can be made of any substance as long as it can collapse into a small enough space. Although black holes cannot be seen directly, astronomers can infer the location of some black holes by observing the surrounding matter.

However, Thibault Damour, a physicist from the Institute for Advanced Studies in Bourget-on-Yvette, Paris, and Sergey Solodukhin of the Bremen International University, Germany, put forward a new view that these so-called black holes are actually wormholes. Wormholes are curved channels connecting two different places in the space-time structure.

If you imagine the universe as a two-dimensional paper, a wormhole is a small passage connecting this paper with another paper. In fact, this theory holds that wormholes; Connected to another universe with its own stars, galaxies, etc.

An example of a small ball that causes space distortion in our three-dimensional world is a black hole. Black holes are actually a phenomenon existing in four-dimensional space, or black holes are connected.

What is a black hole in the universe? Black holes in the universe are mysterious. What is a black hole? An object or part made of a certain material

A "black hole" can easily be imagined as a "big black hole", but it is not. The so-called "black hole" is such a celestial body: its gravitational field is so strong that even light cannot escape. According to the general theory of relativity, the gravitational field will bend space-time. When a star is large, its gravitational field has little influence on space-time, and the light emitted from a certain point on the surface of the star can go in any direction. The more it bends the surrounding space-time, the light from some angles will return to the surface of the star along the curved space. A black hole is invisible, so people can't directly observe it, and even scientists can only make various guesses about its internal structure. So how does a black hole hide itself? The answer is-bending space. As we all know, light travels in a straight line. This is a basic common sense. But according to the general theory of relativity, under the action of gravitational field, space will bend. At this time, although light still propagates along the shortest distance between any two points, it is no longer a straight line, but a curve. Figuratively speaking, it seems that light should travel in a straight line, but strong gravity pulls it away from its original direction. On earth, because the gravitational field has little effect, this bending is very small. Around the black hole, this space deformation is very large. In this way, even if part of the light emitted by the star blocked by the black hole will fall into the black hole and disappear, the other part of the light will bypass the black hole in the curved space and reach the earth. Therefore, we can easily observe the starry sky on the back of the black hole, as if the black hole did not exist. This is the invisibility of black holes. Some stars not only send light energy directly to the earth, but also send light in other directions, which may be refracted by the strong gravity of nearby black holes and reach the earth. In this way, we can see not only the "face" of this star, but also its side and even its back! .

What is a black hole?

A black hole is a very mysterious celestial body.

Its volume is small, but its density is amazing, with tens of tons or even higher per cubic centimeter. Because of its high density, gravity is particularly strong.

No matter what it sucks in, it can't "climb" out. Even the fastest light can't escape the great gravity of a black hole. Because the black hole itself does not emit light, it can't be seen with any powerful telescope.

Nevertheless, most scientists still believe that there are many black holes in the universe. When a massive star evolves into old age, it may collapse into a black hole after a supernova explosion.

In the early days of the universe, some small black holes also formed. The volume of a small black hole is only the size of a nucleus, and its mass is almost the same as that of a mountain, reaching hundreds of millions of tons. The energy contained in it is equivalent to 10 large power stations.

A black hole is like a mystery, no one can see it. However, the strong attraction of black holes will affect the nearby celestial bodies. These celestial bodies will emit X-rays or γ-rays in the process of being attracted and swallowed by black holes, and once they fall into black holes, they will disappear without a trace.

It was by observing these rays that scientists found clues to black holes. For example, the companion star of Cygnus X- 1 may be a black hole.

Some scientists believe that there is also a huge black hole in the center of the Milky Way.