What is dark matter and why do scientists try every means to catch it?

On December 12, 2010, China’s first deep underground ” dark matter” laboratory was put into operation. Speaking of dark matter, do you know what dark matter is?

Astrophysics research found that in the vast space, the mass of luminous stars ( including stars emitting X – rays and gamma rays ) that we can observe is only a small part of the total mass of matter in space. A large part of the quality comes from what we haven’t found out yet. We call this invisible and real thing ” dark matter”.

Scientists’ understanding of dark matter can be traced back to the early 1930s. In 1933, Swiss astronomer Zvecchi used two different methods to estimate the total mass of the Posterior Cluster of Galaxies: photometric method and kinetic method. Results The mass calculated by kinetic method is 400 times larger than that calculated by spectrophotometry. There is only one explanation for such a huge error: the mass of luminous stars is only a small part of the mass of galaxy clusters, and a large part of the mass is lost somewhere. So he called this ” shortage of quality.”

At that time, this discovery did not attract much attention until 1978, when some radio astronomers systematically measured the rotational curves of spiral galaxies, they found that objects at different distances from the center of galaxies had the same linear velocity. This observation is completely contrary to the familiar situation of the solar system. The further away from the center in the solar system, the smaller the linear velocity. This is what Kepler’s famous law tells us. The motion of objects around galaxies, which are also affected by universal gravitation, should also follow Kepler’s law! For this reason, some scientists have proposed that only assuming that dark matter still exists around galaxies, can the observed galaxy motion be consistent with the calculation results of Kepler’s law. Therefore, the idea that there must be a large amount of invisible dark matter besides the luminous objects of galaxies is gradually accepted by people. Under the guidance of this view, scientists have discovered many evidences for the existence of dark matter. For example, R15 star 200,000 light-years away from the galactic center was discovered in 1983 with an apparent velocity of 465 meters per second. To produce such a large speed, the total mass of the Milky Way galaxy must be at least 10 times greater than that of the luminous region.

In addition, scientists do feel that there should be dark matter in their theoretical research on the origin of the universe in order to justify their theory.

So, what exactly is dark matter? In response, scientists have made many conjectures: some people say that dark matter is a gas dispersed in space, others say that it is dust in the universe, and still others guess that it is a ” death star” that has darkened, and even a black hole. Although all these conjectures have their causes, they lack strong evidence and cannot be accepted by the academic community.

Among the many candidates for dark matter, neutrinos are the most popular. Because it is known to exist in the universe, and a very large number of particles. Especially in 1980, after the Soviet Institute of Theoretical and Experimental Physics announced that the quiescent mass of neutrinos might not be equal to zero, it gave people plenty of imagination about the relationship between neutrinos and dark matter. Due to the extremely large number of neutrinos, the total mass of neutrinos is still considerable even though their quiescent mass is very small. In addition, most neutrinos do not emit light, only have weak electromagnetic effects, etc. These properties make them very similar to dark matter.

Of course, particle physicists have also predicted a number of new particles to be candidates for dark matter, such as graviton, photon, gluon, Z, etc. Unfortunately, none of these hypothesized new particles has been found so far. It seems that it is still a long way to go to reveal the true face of dark matter.