Is there dark matter in the universe, and why is there dark matter in the universe?

Dark matter is an invisible substance that may exist in the universe as theoretically proposed, and it may be the main component of the matter in the universe, but it does not belong to any of the currently known substances that constitute visible celestial bodies. The suspected violations found in a large number of astronomical observations can be well explained under the assumption of the existence of dark matter. Modern astronomy has shown that dark matter may exist in galaxies, star clusters and the universe in large quantities, and its mass is much greater than the sum of the masses of all visible objects in the universe.

Combined with microwave background radiation anisotropy observations and standard cosmological models in the universe, it can be determined that dark matter accounts for 85% of the total mass of all matter in the universe.

At present, a widely accepted theory holds that dark matter is composed of "weakly interacting mass particles", whose mass and interaction intensity are around the electroweak scale, and the remaining abundances observed so far are obtained through the process of thermal decoupling during the expansion of the universe. In addition, there are hypotheses that dark matter is made up of other types of particles, such as axions, inert neutrinos, etc.

Only the movement of dark matter in galaxies can be explained. There is circumstantial evidence suggesting the existence of dark matter and dark energy.

In 933, this is how the Swiss astronomer Zwicki estimated the mass of a galaxy cluster. He was surprised to find that the mass of some galaxy clusters "numbered" by luminous matter was much smaller than the mass "weighed" by the movement of galaxies, and the difference between the two was more than 10 times! This means that there are too few luminescent substances in the star cluster, and most of the substances may not emit light!

Zviki calls it "shortage quality" or "traceless quality", meaning that a part of the substance has disappeared without a trace.

At first, no one paid attention to the results of Zviki. Nearly 40 years later, as more and more similar cases occur, astronomers are beginning to understand that there may be non-luminous matter in the universe. They don't emit light, but they have a gravitational pull, so you can feel their presence.

Astronomers refer to this invisible, invisible, material collectively as "dark matter."

There is now more and more observational evidence, such as the morphology of galaxy clusters, the rotation of galaxies, gravitational lensing, the X-rays emitted by galaxy clusters, and the anisotropy of cosmic microwave background radiation, all of which indicate that there may be a large amount of dark matter in the universe.

There are two possible compositions of dark matter:

One is ordinary matter, which is the so-called baryonic matter, such as brown dwarfs, black dwarfs, neutron stars, black holes and other faintly luminous objects. They can participate in electromagnetic interactions, i.e., they can emit light or absorb light. But it is too small, too cold, or too far away to be detected by current telescopes.

However, according to theoretical research, it is not possible for baryonic matter to account for such a high proportion.

So the vast majority of dark matter is probably another substance – non-baryonic matter. Non-baryonic matter does not participate in electromagnetic interactions, does not emit light, and does not absorb light. According to the speed of motion, it is divided into hot dark matter and cold dark matter.

However, the large-scale structure of the universe suggests that there is not so much hot dark matter, so dark matter should be mostly cold dark matter. The most likely candidates for cold dark matter are neutrons, axons, gravitational neutrinos, etc. Neutrons are particles predicted by supersymmetry theory, which are so heavy that they can reach 1,000 times the mass of protons.

However, it is very sparsely distributed in the universe. The axon is also the particle predicted by theory, and its mass is very small, only one part of a hundred trillion protons, but the density is very large. At present, the detection of dark matter particles is still ongoing, and there are no conclusive results.

There are two possibilities, that is, dark matter has become bright matter, and the universe is still the universe, but human cognition has gone up; The other is that the person asking the question asks a question that does not exist, and laughs, the universe will not change by someone's thoughts!

Dark matter is one of the most mysterious things. Astrophysicists are almost certain that it must exist, as the circumstantial evidence from a whole set of independent measurements is overwhelming. Because we have never directly detected any particles that could be responsible for it, many experts and laymen still doubt its existence.

But if our universe didn't have any dark matter, then our universe would be a completely different place. Gravitational action causes the matter in the universe to collapse, while radiation pushes these dense structures back, tearing them apart. If all that the universe has is normal matter and this radiation, this will result in a large number of structures on some scales and the destruction of all structures at others.

This effect is maximized in a universe without dark matter.

When dark matter does not exist, the universe will be peaceful and peaceful, the air will be very good, and people will live very happily and happily, just as nature is beautiful.

Theoretically, there should be dark matter in the vicinity of the Earth, including around us. According to astronomers' measurements, one cubic centimeter, which is the size of our finger, has the mass of dark matter about the same as a hydrogen atom, and if we collect the dark matter of the entire earth, the total is less than one kilogram, so dark matter has almost no impact on our lives.

But even if dark matter is not found, it does not mean that our efforts are meaningless. It means that we need to break through Einstein's theory, and we need to make a leap forward in our understanding of the basic laws of the universe.