Just as he was thinking about it, Hua Feng heard someone speak in his ear: "Boy, even if you have a little understanding, I can't hide it, I am the Monkey King of the Monkey King who once made trouble in the Heavenly Palace." As for now, my identity in Shuguang Academy is Sun Xing. I see that your physique is different from ordinary people, and it is quite similar to the Lingming stone monkey that grows in my world. ”

"Are you...... Sun Wukong?" Hua Feng said with a little incredible surprise.

Because no matter what, Sun Wukong is a superhero in the hearts of any Chinese person, and he never thought that one day he would really meet a mythical character in reality.

"Well, don't be so surprised, there's a lot more you don't know about this world, and now I need you to know something called dark matter. Sun Wukong then said.

Hua Feng felt a large amount of information rushing into his mind: dark matter (Da

k matte

) is an invisible substance that may exist in the universe and may be the main component of the matter in the universe, but it does not belong to any of the currently known substances that make up visible celestial bodies. Suspected violations of Newton's gravitational pull found in a large number of astronomical observations can be well explained by the assumption of the existence of dark matter.

Modern astronomy has shown that dark matter may exist in large quantities in galaxies, star clusters and the universe through observations such as the movement of celestial bodies, the gravitational lensing effect, the formation of large-scale structures of the universe, and the microwave background radiation, and its mass is much greater than the sum of the masses of all visible celestial bodies in the universe. Combined with the observation of the anisotropy of microwave background radiation in the universe and the standard cosmological model (ΛCDM model), it can be determined that dark matter accounts for 85% of the total mass of all matter in the universe.

A widely accepted theory is that dark matter is composed of "weakly interacting mass particles" (weakly i

te

acti

g massive pa

ticle, WIMP), whose mass and interaction intensity are around the electroweak scale, and the remaining abundance observed so far is obtained by thermal decoupling during the expansion of the universe. In addition, there are hypotheses that dark matter is composed of other types of particles, such as axons (axios

), inert neutrino (STE

ile

eut

i

o) etc.

The first to suggest the possibility of "dark matter" was astronomer Jacobus Kaptey

), he proposed in 1922 that the possible presence of invisible matter around a star could be inferred indirectly from the movement of a star system. In 1932, astronomer Ja

Oo

t) Dark matter studies were carried out on the movement of stars near the solar system. However, no conclusive conclusion has been drawn about the existence of dark matter. In 1933, astrophysicist F. Zwicky (F

Itz Zwicky measured the velocity of individual galaxies in the Comae Cluster relative to the cluster using spectral redshifts.

Using the potential force theorem, he found that the velocity dispersion of galaxies in a galaxy cluster is too high to be confined to the cluster by the gravitational pull generated by the mass of the visible galaxy in the cluster alone, so there should be a large amount of dark matter in the cluster, which has a mass at least 100 times that of the visible galaxy.

S. Smith Smith's observations of the Virgo Cluster in 1936 also support this conclusion. However, the groundbreaking conclusion of this concept failed to attract the attention of the academic community at that time. In 1939, astronomer Babcock (Ho

ace W. Babcock, by studying the spectral study of the Great Andromeda Nebula, showed that the rotational motion of stars in the outer regions of galaxies is much greater than expected by Kepler's law, corresponding to a larger mass-to-light ratio.

This suggests that there may be a large amount of dark matter in the galaxy. In 1940, Ault studied the speed of star motion in the outer regions of galaxies NGC3115, and pointed out that their total mass-to-light ratio could reach about 250. In 1959, F.D. Kah. Kane

) and L. Watt Woltje

Studying the relative motion between the Andromeda Nebula and the Milky Way, which are attracted to each other, it is deduced from the speed at which they approach each other and the distance from each other that the dark matter in our native cluster is about ten times greater than the mass of visible matter.

An important piece of evidence for the existence of dark matter comes from the 1970 study of Rubin (Ve

a Rubi

) and Ford (Ke

t Fo

d) A study of the rotational velocity of stars in the Great Nebula Andromeda. Using high-precision spectral measurements, they can detect the relationship between the speed and distance of the rotation of peripheral stars around the galaxy far from the region of the galactic nucleus.

According to Newton's law of gravitation, if the mass of a galaxy is mainly concentrated in the visible stars in the core region of the galaxy, the velocity of the stars on the outer part of the galaxy will decrease with distance.

But observations show that the velocity of the stars on the outer periphery of the galaxy is constant over a considerable area. This means that there may be a large amount of invisible matter in the galaxy that is not only distributed in the core of the galaxy, but also has a mass much greater than the sum of the masses of the luminous stars. 1973 M.S. Robe

ts) and A.H. Rots used a 21-centimeter feature line observation technique to detect the velocity distribution of the gas in the outer part of the Great Andromeda Nebula, which also confirmed this conclusion from another angle.

In the 1980s, a large number of new observations supported the existence of dark matter, including the gravitational lensing effect when observing background galaxy clusters, the temperature distribution of hot gases in galaxies and clusters, and the anisotropy of cosmic microwave background radiation. The theory of the existence of dark matter has gradually become widely accepted by the astronomical and cosmological communities.

According to the comprehensive analysis of the existing observational data, the main component of dark matter should not be any microscopic elementary particles that are currently known. Today's particle physics is striving to explore the properties of dark matter particles through a variety of means.

Although dark matter has not yet been directly detected, there is already plenty of evidence that it exists in large quantities in the universe, for example,

Galaxy rotation curve and diffusion velocity distribution:

The galaxy rotation curve describes the orbital velocity of a visible object in a spiral galaxy as a function of its distance from the center of the galaxy. Based on observations of the mass distribution of visible objects in spiral galaxies and calculations of the law of gravitation, peripheral objects should move more slowly around the center of the galaxy than those near the center.

However, measurements of the rotation curves of a large number of spiral galaxies show that the outer bodies are moving at almost the same speed as the inner ones, much higher than expected.

This implies the presence of massive invisible matter in these galaxies. Combined with the potential force theorem, the distribution of matter in a galaxy can be calculated from the distribution of the diffusion velocity of visible objects in the galaxy.

This method is equally suitable for measuring the distribution of matter in elliptical galaxies and globular clusters. The results show that, with the exception of a few exceptions, the material distribution of most galaxies and star clusters does not correspond to the observed distribution of visible matter, and the mass of visible matter accounts for only a small part of the total mass of galaxies and clusters.

Galaxy Cluster Observations:

The mass distribution of galaxy clusters can be derived by three different means:

1. Observe the motion of galaxies in a galaxy cluster, calculated by gravitational theory.

2. Observe the X-rays produced by galaxy clusters. The mass distribution of the cluster can be inferred from the temperature of the hot gas that emits X-rays, and when the gas reaches hydrodynamic equilibrium in the gravitational field of the galaxy cluster, the mass distribution of the galaxy cluster can be inferred from its temperature.

3. Gravitational lensing (g

avitatio

al le

si

g) Effects. According to the general theory of relativity, light rays from behind a cluster of galaxies bend as they pass through a massive cluster of galaxies, similar to a lens in optics. The distribution of matter in a galaxy cluster can be estimated based on the degree of bending of the background light. These three methods do not affect each other and corroborate each other, making galaxy cluster observation an important means to study dark matter. These observations have consistently shown that the total mass of matter in a galaxy cluster far exceeds the total mass of the material visible within it.

Cosmic microwave background radiation:

On a cosmic scale, this is done by microwave background radiation in the universe (co**ic mic

owave backg

ou

d

adiatio

Detailed observations of anisotropy can determine the total amount of dark matter in the universe. Current observations show that 26.8% of the total energy of the universe is contributed by dark matter, while only 4.9% of the conventional matter that makes up celestial bodies and interstellar gases is the remaining 68.3% is dark energy that drives the accelerated expansion of the universe.

Simulations of the N-body gravity of the evolution of the universe by large-scale computers show that low-velocity dark matter particles without collisions gradually aggregate into clumps under gravitational influence, a process that can form the large-scale structures we see today. The dark matter distribution of these structures has a universal mass distribution. Dark matter moving at low velocity is conducive to the formation of large-scale structures. Whereas, particles moving at high speed tend to smooth out the structure. Therefore, neutrinos are not supported as major candidates for dark matter particles.

The existence of dark matter has been widely recognized, but its properties are poorly understood. The currently known properties of dark matter include only a limited number of aspects:

1. Dark matter participates in gravitational interactions, so it should have mass, but the mass of a single dark matter particle cannot be determined.

2. Dark matter should be highly stable, and since there is evidence of dark matter at different stages of the formation of the structure of the universe, dark matter should be stable on the time scale of the age of the universe (10 billion years);

3. Dark matter basically does not participate in electromagnetic interaction, and the interaction between dark matter and photons must be very weak, so that dark matter basically does not emit light, and dark matter basically does not participate in strong interaction, otherwise the process of primordial nucleosynthesis will be disturbed, and the abundance of light elements will change, which will lead to inconsistency with current observations.

4. Through computer simulation of the formation of large-scale structures in the universe, it is known that the speed of dark matter should be much lower than the speed of light, that is, "cold dark matter", otherwise our universe will not be able to form the currently observed large-scale structure under the action of gravity;

Combine these essential attributes. It can be concluded that dark matter particles do not belong to any kind of elementary particles known to us. This poses a challenge to the highly successful Standard Model of particle physics.