# Neither black hole nor dark matter can be seen, what is the difference between them, is it the same thing?

2021-04-06 | Time and Space Communication Original |

In some people’s minds, black holes are considered “black” and therefore invisible; dark matter is “dark” and invisible. In this case, aren’t they the same thing? Invisible seems to be one of dark matter and black holes.Similarity.

This is a common misunderstanding. In fact, black holes and dark matter are two things with completely different properties. They are different in terms of source, generation conditions, expression methods, and mechanism of action. Let’s discuss and understand them together.These two things.

First talk about the conditions for the formation of black holes.

A black hole is a massive celestial body. Under its own extreme gravitational pressure, matter cannot support the visible form of existence. It is compressed to be smaller than the elementary particles, and finally becomes invisible mass, and infinitely collapses to the infinitely small singularity of the core.The singularity has the properties of "four infinity", namely, infinitely small volume, infinite density, infinitely high temperature, and infinitely large curvature.

The solution of the black hole was discovered by the famous physicist and astronomer Karl Schwarzschild in 1916. Based on the field theory of general relativity just published by Einstein, he obtained an accurate solution of the gravitational field, namelyAny object with mass has its own Schwarzschild radius, which is a spherically symmetrical space.

The formula for Schwarzschild radius is: R=2MG/c^2. R is the Schwarzschild radius, M is the mass of the object, G is the gravitational constant, and c is the speed of light. The meaning of this formula is that no matter what the object hasHow big, once compressed by a huge force to within the Schwarzschild radius of its own mass, it will become a black hole. The center is a singularity with the characteristics of "four infinity", and a singularity will be formed around the Schwarzschild radius.Spherical space, this space has infinite curvature, any matter entering this range will be eaten up, disappear in the invisible singularity, and light cannot escape.

How big is the Schwarzschild radius of this sphere? The mass of the sun is 1.9891*10^30kg, and the Schwarzschild radius is calculated according to the formula to be about 3000m meters; the mass of the earth is 5.965*10^24kg, and the Schwarzschild radius is onlyAbout 9mm millimeters. This is the sun, a sphere with a radius of about 700,000 km. If it is compressed to a radius of only 3km, the earth’s sphere with a radius of 6371km, compressed to a radius of 9mm, will become a black hole.

No matter how small the mass is, atoms, protons, neutrons, and electrons all have Schwarzschild radius. In theory, if they are compressed into their own Schwarzschild radius, they will all become a miniature black hole. But the black holes discovered by humans,They are all formed under natural conditions, and they are all formed by massive celestial bodies. The smallest black hole is about 3 times the mass of the sun.

Since black holes are "black", why can they be discovered?

The "black" of a black hole is not the kind of black that we usually think of as "fingerless", but completely "no" black, just like it doesn't exist, because light is "eaten" by it. In that case, whyCan it be discovered by scientists? This is because although the black hole is invisible, its own "aura" is too large, the entity is invisible, but the "aura" cannot be hidden.

This "aura" is the charge, mass, and angular momentum of the black hole. According to Einstein's field theory, mass will cause space-time to bend, that is, the formation of gravity. The black hole is gone, but its huge gravity still exists in the universe.Due to the small size of the black hole, celestial bodies or any matter close to the black hole will be captured by its strong gravity and gradually eaten.

This will form an accretion disk around the black hole. All celestial matter is rotated by the angular momentum of the black hole. The closer the matter is, the faster the rotation. At the junction of the Schwarzschild radius of the black hole, the rotation speed is even close.Speed ​​of light. In this extremely fast collision, matter bursts out huge energy and emits dazzling light, which not only emits visible light, but also bursts out energy rays, such as ultraviolet rays, X-rays, and gamma rays. These visible and invisible lights will be destroyed.The telescope and corresponding scientific instruments have captured it, so the black hole has appeared.

The existence of the huge gravitational force of the black hole will also cause disturbance to the surrounding celestial bodies. By observing the strange trajectory of the surrounding celestial bodies, even a black hole without an accretion disk will be discovered. For example, HR 6819 Samsung, which is only 1,000 light-years awayThe system above was discovered through two strange orbiting stars. The two stars circled an invisible space. After long-term observation and calculation, the scientists finally concluded that the middle one has 4 timesThe sun-mass black hole involves these "two brothers".

Let's talk about dark matter again.

The first Dutch physicist Jacobs Captain suggested that dark matter may exist. Scientists have discovered through a large number of astronomical observations that the motion of large-scale celestial bodies seems to violate Newton's law of universal gravitation, such as the total mass of galaxies in galaxy clusters., The gravitational force produced simply cannot constrain these galaxies to form such a cluster of galaxies. According to the law of universal gravitation, these galaxies will fall apart.

What force keeps these galaxies in an orderly cluster state? Is Newton wrong, or is there still something invisible and undiscovered in this world? After a lot of observation and research, scientists are inclined to Newton.There are still some things that have not been discovered or cannot be observed. People call this unobservable matter "dark matter".

According to calculations, this dark matter accounts for 85% of the total matter in the universe, that is to say, the visible matter in our universe only accounts for 5%, and the invisible matter accounts for 85%. Only in this way can it be in line with Newtonian gravitation.The law. Now, the scientific community has accurately calculated that the total mass energy of the universe includes 68.3% of dark energy, 26.8% of dark matter, and 4.9% of visible matter.

Calculations through observations of galaxy clusters in various directions in the universe show that as long as the dark energy ratio is substituted into the calculation, Newton's law of universal gravitation is back and accurate. From this, it can be considered that Newton is not wrong. In this vast universe,There is indeed a mysterious substance, which is not only not perceivable by our retina, but also not perceivable by any radio telescopes and scientific instruments so far.

Indirect evidence of the existence of dark matter.

Since human beings are currently unable to find "dark matter" through any instrument, what evidence is there to prove the existence of dark matter?

The main function of dark matter is mass and gravity. In the invisible space, dark matter exists everywhere. These dark matter have mass, and gravity is the basic attribute of mass. Everything with mass has gravity, so dark matterThe gravity of is everywhere. It is the action of dark matter that enables all kinds of celestial bodies to form and gather together to form a large-scale structure of the entire universe. It can be said that without dark matter, there would be no universe today, and there would be no you and me..

Because dark matter does not participate in electromagnetic interaction, and the interaction with photons is also very weak, so dark matter does not emit light, we cannot see; dark matter does not participate in strong interactions, otherwise the synthesis of nucleons in the universe will be disturbed at the beginning.The elemental composition of the universe would not be like this.

It is very likely that dark matter will exist soon after the explosion of the universe. It has been affecting the formation and evolution of the universe for more than 10 billion years. Therefore, the existence of dark matter is stable. Through computer modeling and simulation, the speed of dark matter is much lower than the speed of light., Otherwise the universe cannot form today's large-scale structure under the action of gravity, so dark matter is also called "cold dark matter".

These evidences for the existence of dark matter are all obtained indirectly. So far, people have not observed what dark matter looks like, how big and what kind of structure it has.

The clues of dark matter.

Someone once thought that neutrinos are dark matter. In fact, neutrinos have many properties similar to dark matter. For example, they cannot be directly observed. However, neutrinos are different from "cold dark matter" in two ways. One is that neutrinos are different from "cold dark matter".It travels at close to the speed of light, so it is called "hot dark matter"; secondly, the overall mass of neutrinos is far from enough to support the gravity of the entire universe, accounting for only about 0.0034% of the total universe.

Nowadays, people have built many facilities under the ground at a depth of one thousand meters, launched many detectors and satellites, and have done many experiments in large-scale colliders. Through this three-dimensional method, the sky and the earth are deployed in an attempt to find the dark matter.Clues, but so far, there has been almost no direct evidence. It is still unknown what this "ghost" looks like and whether it can be revealed.

Now, we can see the difference between black holes and dark matter.

First of all, the forms of their existence are different. Black holes are generally in the form of local existence, a single celestial body, and the scope of influence is only a region; dark matter exists diffusely, all over every corner of the universe, and the scope of influence is large-scaleCelestial structure, its existence cannot be measured in a single celestial system.

Secondly, their stealth methods are different. Black holes are only hidden in a certain corner, but they cannot cover their own "aura". They will have an observable impact on the surrounding celestial matter, and even swallow them vigorously.It is easy to be discovered; the influence of dark matter is difficult to determine on a large scale, and it is a silent penetration of the overwhelming moisturizing matter, which can be ignored on a small scale, but in the entire universe, all visible matter cannot escape its control.

Therefore, there are two kinds of existence, one is microscopic and the other is macroscopic. Although both can be observed indirectly, the observation of black holes can be visually visible observations, while the dark matter can only be understood and cannot be explained, mainlyIt is the result of mathematical modeling and logical operation.

Through this analysis, everyone should understand the difference between black holes and dark matter. You don’t think black holes are dark matter anymore? It is a great honor for space-time communication if you can solve your doubts. If you like it, please pay attention and like it.Well, thanks for reading, and welcome to discuss.

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