(This chapter is too much of a theory, and it bothers everyone.) Pen × fun × Pavilion www. ｂｉｑｕｇｅ。 ｉｎｆｏ）

What exactly are the mysterious dark matter and dark energy?

Since the theory of dark matter was proposed by scientists, there has been a variety of speculations about dark matter particles. Although scientists do not yet know what dark matter is, they have selected many candidates (including: inert neutrinos, neutrinos, asymmetric dark matter, matter in mirror worlds, matter in other dimensions) and are trying to identify them one by one.

One of the hypotheses that scientists at the Interstellar Exploration Alliance has put forward during the Earth era: dark matter is made up of "weakly interacting massive particles" that are 100 times more massive than protons, but they interact in a similar way to neutrinos. Such particles were produced in the hot, dense early universe and have maintained their mass and density to this day. ”

Yuan Haochen looked at the black treasure green meteorite in his hand, and casually knocked the button of the virtual computer in the air, and introduced the artificial intelligence Wali by the way.

"So, what exactly is the progress made by the IEA's scientific team?" Vali asked.

"According to the theory of supersymmetry, [weakly interacting massive particles] annihilate each other and produce a range of particles and radiation, including moderate-intensity gamma rays. However, the IEA, including the scientific team of the Sunrise Galaxy, was unable to find any concrete evidence of the existence of such particles in their experiments. It is not possible to look for clues (such as gamma rays, neutrino and cosmic rays) that arise when such particles are annihilated, either directly with powerful particle colliders or in neighboring galaxies and galaxy clusters. Yuan Haochen said.

"That's no progress at all?" Wall-E's phantom spread his hands in the air, simulating a look of disappointment.

"All in all, in the course of hundreds of years of research, scientists have put a lot of effort into using various experimental methods to find dark matter particles, but in the end nothing has been found, so this theory has been questioned by most scholars." "But in terms of the current state of scientific research, the cosmic science team of human civilization cannot rule out the possibility that dark matter is a 'weakly interacting massive particle'." ”

Vali didn't know what to say.

"Why are all the particles known to mankind so light? Especially with respect to the gravitational scale of nature (Note 1). "Scientists speculate that if the mass of dark matter particles were present near the Planck scale, there would be no hierarchy problem, which would also explain why we don't see any signs related to 'weakly interacting massive particles.'" ”

In the past, the special project team of the IEA Institute of Astrophysics has developed a variety of new mathematical models to explore the upper limit of the mass of dark matter.

On the Planck scale, one mass unit is equal to 2.17645×10^-8 kilograms, which is roughly equivalent to 1 microgram, or 10^19 times the mass of a proton. Based on this calculation, the mass of each "Planck-interacting dark matter" elementary unit is close to the limit of the particle's mass, and if it is heavier, it will become a mini-black hole.

"Sorry boss, I don't really understand these theories." Vali said with some writ.

"It doesn't matter, you can slowly decipher these conjectures and theoretical models." Yuan said disapprerovingly, "There are also scientific teams that believe that in the cosmic timeline, these dark matter were formed in large quantities in the very early days of the universe - the "reheating period". This period occurs at the end of the "inflationary phase", roughly between 10^-36 seconds and 10^-33 seconds after the "Big Bang". ”

"Reheat period?" Vali asked rhetorically.

"This period is called reheat because during inflation, the temperature of the universe drops by a factor of about 100,000. Once the inflation is over, the temperature begins to rise back to the pre-inflation level (about 10^27 K). At this moment, the enormous latent energy in the inflation field begins to decay into Standard Model particles that are spread across the universe, and dark matter may be included in it. Yuan Haochen introduced while reviewing the information on the virtual computer screen.

"If dark matter does exist on the Planck scale, inflation must occur at extremely high energy levels, which means that it can not only fluctuate in the temperature of the early universe, but also cause space-time itself to fluctuate and produce gravitational waves. Second, it tells us that inflationary energy must decay into matter very quickly, because if it lasts too long, the cooling of the universe will make it difficult to produce dark matter on the Planck scale. ”

"Boss, what do you mean by this passage that future research on the microwave background of the universe may tell us the truth about dark matter?" WALL-E asked.

"The existence or absence of such gravitational waves can indeed be confirmed or ruled out in future studies of the cosmic microwave background." Yuan Haochen paused for a moment, and then continued, "Actually, there is no harm in such research. If we discover such gravitational waves, it will be a happy outcome, and the greatest mystery in cosmology will be solved; If we don't see it, then we will know that dark matter is not such a thing, and that other unknown matter must interact with ordinary matter, which will also give us a lot of expectations. ”

"Boss, your words made me realize that our understanding of the universe is really very limited, and there are still many secrets waiting for us to discover!" Vali said.

"That's what happened!" Yuan Haochen replied indifferently.

"Physicists have envisioned a wide range of possibilities to solve these elusive problems." At this moment, WALL-E's computer system had received the message that Yuan Haochen had transmitted to him.

"Yes, no one knows which experimental model will ultimately solve the problem of dark matter and dark energy." Yuan Haochen nodded and said.

"Boss, I can understand inert neutrinos, neutrinos and other particles. However, do you think that dark matter really exists in a mirror world (a world that is completely isolated from our current universe, and dark matter is the substance of this world. These "dark protons" "dark neutons" almost do not interact with our space except through gravity, so they seem to us almost no trace) or matter that exists in high-dimensional space? Vali asked, somewhat incredulous.

"We have reached out to high-latitude space, but they are still not observable in four-dimensional space, and perhaps dark matter still exists in higher latitudes."

"And the mirror world or the multiverse is still ethereal at the moment......."

Yuan Haochen did not, and could not answer this question head-on.