In fact, a black hole is not a hole, nor is it black. The matter sucked into a black hole is not absolutely unable to return to the outside world, and the black hole is definitely not black (black holes are colored, but they are invisible to the naked eye, which will be mentioned later when talking about black holes and accretion disks).
The black hole theory originated from a priest named John Lin Kewei in18th century. He combined the theory of light speed and Newton's escape velocity to calculate an interesting celestial model.
If we throw a stone up to the earth, no matter how hard it is, it will fall back to the earth. If we fly out of the earth at a high enough speed, we can fly out of the gravity control range of the earth like a rocket. This speed is the so-called escape speed. For the earth, the escape velocity is 1 1.2 km/s, which is related to gravity, and gravity is related to mass. Therefore, if the mass of a celestial body is greater, the corresponding escape velocity is higher.
Suppose a celestial body has a huge mass and needs to escape faster than light. At this time, even if we throw a stone at it at the speed of light, the speed of the stone can't reach the escape speed from the celestial body, so it will eventually turn around and return to the celestial body.
Thus, there is the most primitive concept of a black hole-a celestial body from which even light cannot escape.
But the concept was so horrible that the church and astronomical society at that time resisted this monster. How did God create such Satan? So people stop studying it.
However, everything changed again before Einstein's great theory of relativity.
Let's talk about Einstein here. He doesn't study very well in college, he doesn't study hard, and he doesn't like his teachers. Minkowski, one of the greatest mathematicians, even called Einstein a "lazy dog"!
But Einstein was not lazy. He was just not interested in the research and conclusions that his predecessors had done. 1905 was a glorious year for Einstein. He abandoned the concepts of absolute space and absolute time that had been established since Newton, and re-established a new set of relative concepts in his independent research.
In front of Einstein, there are four concepts, space, mass, time and the speed of light. Newton's classical physics holds that space, mass and time are absolute, while the speed of light is relative. However, with a very keen sense of touch, Einstein felt that only the speed of light was absolute, and space, mass and time were relative.
Therefore, Einstein created the foundation of the greatest theory in human history-special relativity.
Special relativity is a theory of principle, which consists of two basic principles:
The absolute principle of the speed of light, no matter in any direction or space, the speed of light is absolutely constant.
According to the principle of relativity, all motions in physics must be treated from the same point of view.
That is-my so-called space must be a mixture of your space and your time, and your so-called space must be a mixture of my space and my time.
And from the special theory of relativity, a more surprising conclusion is drawn. The faster the relative speed of a moving object, the shorter its length, the slower its time and the greater its mass.
Suppose I am on the train and you are watching the train pass by on the ground. At this time, you will find that I am shorter, slower and more massive.
But this is not enough to solve the deeper problems, the nature of space-time and gravity. Einstein knew that gravity was the key to all laws. 1908, Minkowski, who once called Einstein a lazy dog, discovered an important theory, the absolute theory of four-dimensional time and space. This is a mathematical language to describe the special theory of relativity, but Einstein didn't care about this theory at that time and laughed at this complicated mathematical description.
What led to Einstein's next success was a very famous astronomical problem, the perihelion of Mercury. According to Kepler's elliptical orbit, Mercury should orbit the sun in an elliptical orbit. However, hundreds of years of observation have proved that every time Mercury orbits, it is impossible to return to its original position, but there is a slight deviation. This is the movement of mercury at perihelion. This movement has 1.38 arc seconds.
Newton's law of gravity can explain 1.28 arc seconds in 1.38 arc seconds, which is the result of the gravitational force of Jupiter and other planets on Mercury, but it can't explain the remaining 0. 1 arc seconds, and the measurement error is only 0.0 1 arc seconds.
First of all, Einstein established an "equivalence principle", which can be simplified by the primary school textbook "Two iron balls touch the ground at the same time".
Suppose you are on the edge of a cliff, and a shell in the distance jumps off the cliff at the moment it is hit. At this time, people who are relatively still on the ground see that the motion of the shell is parabolic. And you are falling off the cliff. Look at the movement of the shell, which is a straight upward movement with uniform change!
Why? Because you and the shell are in the same frame of reference under the action of gravity, the effect of gravity on the shell and the effect of gravity on you cancel each other out. In this frame of reference, your motion and the motion of the shell are not affected by gravity, which is called weightlessness.
Then, Einstein got a more amazing theory, that is, gravity causes time to expand.
Suppose we have two very accurate watches, one on the ground and the other in the sky. After a period of time, the watch in the sky must go faster than the watch on the ground!
19 12 years, after a period of struggle, Einstein was finally forced to accept Minkowski's concept of absolute time and space-there is only one absolute four-dimensional time and space in our universe. In this way, he can explain the curl of time and space in the new theory. That is to say, space-time near the earth has a larger curl curvature, while space-time far from the earth has a smaller curl curvature. The watch on the earth is affected by the curl of time and space, and it goes slowly!
In the following three years, Einstein finally realized the significance of mathematics, especially Riemann geometry, to his new theory, so he described his theory in mathematical form again when he lectured between several universities. After calculation, on1915165438+1October 25th, one of the greatest physical theories in human history-general relativity was born.
In fact, the first person who worked out the complete form of general relativity was not Einstein, but the mathematician Hilbert who worked with him for some time. )
At this point, Einstein's contribution to physics has been completed. Later, there were not many achievements, even a clear-cut opposition to quantum physics and black hole theory. The most famous is his refutation of the famous saying of quantum mechanics, "God can't roll dice!" "To refute the uncertainty principle in quantum mechanics.
Now, let's look at the black hole theory put forward at the beginning with the principle of general relativity. Gravity is not a force, it is very different from the "force" we use to push and pull things. The essence of gravity is the curl of time and space. In other words, the earth does not "pull" or "attract" us, but our time and space are curled and distorted by the gravity of the earth. Therefore, we need a new geometry to calculate the state of spatial distortion, so as to know what kind of distortion will make the light inexhaustible.
On June191June 65438+1October 13, Schwarzschild calculated the solution of the first Einstein equation and established Schwarzschild geometry. Schwarzschild analyzed the stars that don't rotate at all, and obtained the curvature of spacetime except any spherical stars that don't rotate. But four months later, Schwarzenegger died in the Russian front.
Schwarzschild predicted that every star has a critical perimeter, which depends on the star's mass, that is, the perimeter calculated by Lin Kewei in18th century-18.5km multiplied by the star's mass in the unit of solar mass. In other words, if the circumference of the sun is reduced to 18.5km, then the sun will become a black hole.
But the black hole mentioned here is not that light can't escape, but that the gravity is so great that the space-time on the surface of the star can be strongly distorted that time stops flowing there-it is "frozen"!
Therefore, the curl of time and space is the cause of the formation of black holes, and the curl of time and space is also the essence of gravity. It is more accurate to describe black holes with the concept of space-time curl, rather than a simple description of gravity.
However, black holes are not "black". They are not absolutely invisible to the outside world. On the contrary, black holes are very, very beautiful! Especially accretion disks and jet black holes, are very spectacular. Among the black hole candidates that have been discovered, there is a jet black hole, which emits high-energy jets for billions of light years!
A black hole is not completely black, it radiates outward, which is the energy fluctuation mechanism I explained in that post. However, some black holes rotate very fast, and the surrounding gas is quickly sucked into the horizon, resulting in huge eddy currents.
Some black holes are binary systems, and the main star is usually a black hole, so the hot gas of the companion star will be sucked into the black hole, forming a very spectacular accretion disk. At the same time, the space-time distortion near the black hole is very huge, which makes the light strongly deflect and forms an unprecedented "optical disk" scene.
Finally, the description of vacuum fluctuation is supplemented. Mass and energy are two forms of the same thing, so the fluctuation of energy in vacuum can lead to the formation of elementary particles. The energy of elementary particles is quite small, that is, calculated by E = MC 2, so small mass can produce a reaction, even a cell can't be broken. 1928, paul dirac described this phenomenon and founded the so-called Dirac Ocean. A pair of positive and negative particles will be automatically generated and annihilated within 10-2 1 second, and particles with larger mass may also be generated in a vacuum, but according to the uncertainty principle of quantum mechanics, they can only survive for a shorter time.
Evaporation of black holes-Although black holes will evaporate, the evaporation of black holes is very slow. If the horizon evaporates, it will take us a long time to see the center of the black hole-the most mysterious singularity in the universe. It takes 10 15g for a black hole to evaporate.
So Peng, one of the greatest mathematicians today? The theory of cosmic censorship was put forward by Pen Rose, who believed that the singularity of black holes could not be seen because of cosmic censorship. Even if you want to see it, you have to pay the price. You can't take its information out of the black hole. To this end, Hawking made fun of Einstein. He said, "God not only rolls the dice, but also throws them out of our sight!" "