Chapter 403 A day recorded in the history of human science (Part 2)
"...."
In the laboratory.
Looking at Lu Chaoyang with a solemn expression.
Xu Yun swallowed hard and turned to look at everyone in the room.
Zhang Han, Tang Fei, Guo Ping... even Ye Zhi, the tool man in charge of ordering takeout, looked solemn and shocked at this time.
Then he looked at Lu Chaoyang again, with a hint of hoarseness in his voice:
"Professor Lu, what you said...is true?"
Lu Chaoyang smiled bitterly when he heard this and handed the document to Xu Yun:
"See for yourself."
Xu Yun lifted off the blanket on his body, took the document, sat up straight and started reading.
"Quadratic divergence parameter 3.445...."
"The columnar orientation is at right angles to the electron parallel orientation..."
"The parity difference is 226.5 points/billion...."
at last.
Xu Yun's eyes paused on an item labeled U Group.
This project is divided into four columns: U1, SU2, SU3 and SL(2,C).
Among them, SL(2,C) displays [ ], and below the U1, SU2 and SU3 columns is...
【X】.
See this situation.
Xu Yun's breath suddenly stopped.
It was introduced a long time ago.
In the current particle theory, the particles that transmit "force" are all bosons with spins of one or two.
So what boson is transferred is called a force.
There are several types of these bosons, so they need to be classified.
The criterion for classification is symmetry, which is expressed mathematically as a group.
Since the theory describing forces is called a "gauge field theory", these groups are called gauge groups.
Generally speaking.
The bosons discovered so far can be divided into four groups, which correspond to the four basic forces mentioned before.
Respectively, the U1 group corresponds to electromagnetic force and photons.
The SU2 group corresponds to the weak force, which corresponds to W and Z bosons.
SU3 corresponds to the transmitted strong interaction, which corresponds to gluons.
And the SL(2,C) group corresponds to the transfer of gravitational interaction, which corresponds to the graviton.
In addition to gravitons, three other particles have been discovered.
See here.
There may be children's boots who will say that I understand. What Xu Yun and others discovered was gravitons.
Unfortunately, it is not.
Because the graviton will theoretically participate in electromagnetic interactions, and because its spin is 2, the field theory involves a limit energy scale, which is obviously not in line with today's experimental conditions.
So what does this report mean?
The first point to emphasize is...
These four groups can coexist in actual situations, that is, a certain particle can participate in multiple functions at the same time.
To give an example that is not quite appropriate but easier to understand:
An author is hung up by a reader. The rope has electromagnetic interaction with him, the gravity of the earth has gravitational interaction with him, and the small universe in his body also has weak interaction...
Therefore, when these four groups detect certain particle characteristics, the reports generally show that the effect of a certain column is strong or weak, not 0.
For example, if a particle is in the U1 group... that is, the degree of electromagnetic interaction is relatively weak, it will be represented by [-].
Strong is [ ].
If the corresponding behavior does not occur, then it is [X].
All current particles will participate in the gravitational interaction, so under the gravitational interaction...that is, under the SL(2,C) group, there will only be [-] or [ ].
As for strong and weak forces, you can occasionally see [X].
For example, lepton.
In the U1 group, which is the column of electromagnetic interaction, only one particle will appear [X].
That's the neutrino.
And just today.
In front of Xu Yun and the others, another brand new U1 group [X] particle appeared.
More importantly...
A solitary point particle, its movement mode is "flickering".
In other words, its kinetic energy is much smaller than the corresponding static energy - this sentence was once explained by a fat man running 100 meters.
On this basis.
Solitary point particles also have electrical neutrality and no definition of static mass...that is, they have no entity in the microscopic world, so they only participate in gravitational interactions...
In the current scientific community, this kind of particle or substance has a special and exclusive name.
Think of this.
Gulu——
Xu Yun swallowed and looked at Lu Chaoyang in shock:
"So...Professor Lu, we discovered a...dark matter?"
Lu Chaoyang took a deep breath and nodded vigorously:
"Yes, according to the teacher's results, the probability is infinitely close to 100%."
Xu Yun stared blankly at the document in his hand. After a long time, he sat back down.
yes......
I should have thought of it a long time ago.
Doesn’t an undetectable particle meet the definition of dark matter?
Dark matter.
This is something that is widely spread, but many people know little about it.
The prototype of dark matter can be traced back to 1922.
At that time, astronomer Kaptan indirectly inferred that there might be invisible matter surrounding the stars through the motion of the star system.
Then in 1933.
Astrophysicist Zwicky used the spectral redshift method to measure the motion speed and state of each star cluster in the Coma galaxy cluster.
It was found that the velocity dispersion of galaxies is too high. If the gravity generated by the visible mass of galaxies alone cannot bind these galaxies into galaxy clusters, these galaxy clusters will fall apart.
However, the real ‘battle for fame’ of dark matter took place in 1970.
At that time, a female professor named Vera Rubin, who had the same name as the well-known rich woman from Qidian, conducted a measurement of the rotation curve of the Andromeda Galaxy, a neighbor of the Milky Way... that is, the M31 galaxy.
The so-called galaxy rotation curve refers to the function curve of the rotation speed of stars at a certain distance from the galaxy around the center of the galaxy.
In human terms, it is the revolution speed.
If the gravity of the galaxy is provided only by visible matter, then it can be calculated that the rotation curve should show such an effect:
The farther a star is from the center of a galaxy, the slower it should rotate.
However, when Vera Rubin observed the Andromeda Galaxy, she discovered...
The actual rotation curve is after exceeding a certain distance.
The farther away the stars are from the center of the galaxy, the rotation speed and interior remain almost unchanged.
What does this mean?
Anyone who has taken high school physics should know this.
at the same distance from the center of the galaxy.
The centrifugal forces of V1 (which is the theoretically slower speed) and V2 (the rotation speed observed by Vera Rubin) are completely different.
The former is low and the latter is high.
So if the gravity of the galaxy is provided only by visible matter, then theoretically the stars rotating with V2 will be thrown out of the galaxy.
unless......
Those stars are attracted to something unseen and are thus bound to the galaxy.
In other words, the actual mass of the galaxy is greater than the mass calculated from observations.
This is the root of all evil in dark matter.
By 2022, there will be a lot of evidence for dark matter.
For example, the total mass of a galaxy (or galaxy cluster) obtained through multiple independent measurement methods is much greater than the mass of ordinary matter in it.
Another example is the observation of the cosmic microwave background radiation.
Another example is the simulation of the number of galaxy clusters formed at different ages of the universe, etc...
Another thing to mention is.
The current calculation method for galaxy mass is very mature and will not cause too much error. (For specific methods, see Chapter 281)
so what.
The above situations are real. To explain these anomalies, people have two ways:
One is to adhere to the correctness of the known gravity theory, that is, the general theory of relativity, but introduce some electrically neutral substance to provide an additional source of gravity.
This kind of particle only participates in gravity but does not participate in electromagnetic interaction. It cannot be detected by electromagnetic means, so it is called "dark matter".
The second is not to introduce the concept of dark matter, but to modify the gravity theory so that the revised theory is consistent with astronomical measurement results on the large-scale structure of the universe.
Particle physicist option one.
Because after all, introducing new particles is a more economical and tried-and-tested method, and many of the earlier models introduced were later proven correct, such as the Higgs particle.
But general relativity theorists mostly prefer option two.
Because I can eat and grow happily again.
Currently, the number of scientists who hold view 1...that is, the existence of dark matter is much higher than the latter.
For example, our country has launched the Wukong dark matter detection satellite into the sky for exploration, and there are many related projects abroad.
The more accurate statement in the scientific community now is this:
Of the total mass and energy in the universe, only 4.9% is visible matter.
That is to say, the galaxies, nebulae, dust, stars, planets, etc. that we can see only account for 4.9% of the total mass and energy of the universe, and the remaining 95.1% is 26.8% dark matter and 68.3% dark energy - this is not Minkoha,
It is a relatively unified view of cosmology today. (For example, this article in "Science" 10.1126/science.1146676 and this?/10.1093/mnras/staa3016)
But what needs to be clear is.
Although there is a lot of theoretical evidence to support the existence of dark matter, the probability of the existence of dark matter is countless times greater than that of "gravitons" - the countless times here is not an exaggeration, but it is true.
But so far, humans have still not discovered any dark matter that is not a broad concept.
In a sense, this thing is like a black hole:
Everyone knows that black holes exist, but it was not until the Event Horizon Telescope photographed the accretion disk in 2019 that humans actually confirmed the existence of black holes for the first time.
Until then, the physics and astronomy communities could only use phenomena to demonstrate the existence of black holes.
The same goes for dark matter.
Before the discovery of neutrino oscillations, the scientific community had always believed that neutrinos were most likely dark matter.
But after the discovery of neutrino oscillations, this possibility was passed.
Because neutrino oscillation proves that neutrinos move relativistically when galaxies are formed in the universe. If they are the main component of dark matter, they will hinder the formation of large-scale structures of galaxies and even the universe, so they cannot be the main component of dark matter.
Neutrinos are now classified as thermal dark matter...that is, a part of dark matter that moves at a speed close to the speed of light in a vacuum and does not participate in electromagnetic interactions.
This is just like the theory of evolution has been looking for the standard "human ape", that is, the evolutionary intermediate between primitive people and apes.
But after searching and searching, we couldn't find the ape, so we had no choice but to classify the chimpanzees into the concepts of "half-step ape", "peak ape perfection" and "can take a hit from the ape without dying".
In other words, it can be included in the hard calculation, but it has no real meaning.
Today, there are only five particle models that theoretically meet the conditions for dark matter:
Weakly interacting massive particles (WIMPs),
axion,
sterile neutrinos,
supermassive particles,
Ultra-light vector particles.
The most interesting of them are WIMPs and supermassive particles.
WIMP is also called cold dark matter. If such particles existed, they would have been produced in large quantities at the beginning of the Big Bang.
Then, after the temperature of the universe drops to the mass energy scale of the WIMP particles, they will quickly annihilate each other.
In the end, the remaining part is left to this day and becomes dark matter.
Xu Yun met an old professor at the Academy of Sciences who liked fairy novels very much. He even gave WIMP a nickname that was very fairy-like:
signpost.
This is also the model with the most researchers and the highest topic at present.
As for supermassive particles... they are also called Godzilla particles and ear root particles.
This chapter is not finished yet, please click on the next page to continue reading the exciting content! It refers to a type of particle with a mass greater than the inflation energy standard...about 10^13 GeV.
The operating mechanism of this thing is not the point, but once it is discovered, it will be a lot of fun:
Because this thing can be produced through the "freeze in" mechanism of annihilation of other hot particles, it is a propagator of gravitons.
So the discovery of supermassive particles is almost a buy-one-get-one-free discovery of gravitons.
Since these five types of particles cannot be found so far, the industry also calls this phenomenon "Five Particles".
Of course.
In addition to these five models, primordial black holes are also candidates for celestial-type dark matter.
This kind of black hole is very different from the black hole formed by the collapse of stars. It is not formed by the evolution of astrophysical processes, but is formed directly from the density fluctuations of the very early universe.
Students who have participated in the Big Bang should know this.
In the very early days of the birth of the universe, cosmic inflation brought original density disturbances to the universe.
If the density perturbation amplitude in some space-time regions is large enough.
Then as the horizon expands, it will contain enough matter to directly collapse this space-time region into a black hole. This is the so-called primordial black hole.
As we all know.
The greater the mass of the black hole, the slower the evaporation rate.
It can be seen from calculations that primordial black holes with a mass greater than 10^9 tons can still survive to this day after 13.8 billion years of evolution, thereby acting as dark matter.
One of the purposes of future space gravitational wave detection experiments, such as LISA or my country's Tai Chi Project, is to search for such black holes.
I just didn't expect it...
Dark matter, which the entire scientific community has been eagerly anticipating, was unexpectedly discovered like this?
This is no less a treasure than the Pirate King...
Now let’s look back carefully along the timeline.
There is no static mass definition, no entity, and no interaction with any particles in non-ground states...
Even in the process of ground state treatment not long ago.
Xu Yun and others also found that the results of high-energy photons were not obvious and the constant mass distribution was irregular....
There is also one of the important characteristics of dark matter. The kinetic energy is much smaller than the corresponding static energy...
It can be said like this.
Except that it has not been determined whether the solitary point particle has been left over to this day after 13.8 billion years of evolution.
All the properties previously exhibited by solitary point particles are all standard dark matter characteristics!
Should this be said to be a result of people searching for him countless times, or should it be said to be an unintentional intervention?
Think of this.
Xu Yun's mind reappeared in his mind when he discovered the solitary point particle...that is, the original formula that deduced the motion orbit:
The original formula can be divided into three parts...or deciphered in stages.
Among them, the orbits of isolated point particles are only the first one-third of the deciphering results, and Xu Yun still has no clue about the remaining two-thirds.
It seems.
The value of that original formula far exceeded Xu Yun's expectations.
In fact, after the 1850 copy ended, Xu Yun had always had a vague confusion in his heart:
Compared with 1850, what I did in 1100 should have a greater impact.
Let alone history.
It changed the demise of the Northern Song Dynasty, expanded China's territory all the way to Europe, and nearly conquered the world.
In terms of science and technology, microscopes and telescopes were developed, unlocking the microscopic realm a thousand years in advance.
But in terms of rewards, the 1100 copy seems to be much inferior to the 1850 copy.
Although the 1100 copy rewards a national fortune, 1850 also rewards the Yongle Grand Ceremony - this thing is not like the Jade Seal, which requires a specific task to be activated, but can be dug out and eaten immediately.
So the two are barely equivalent.
Except for the national destiny.
The gravity gradient meter, MR technology, hemostatic gelatin, computing power module and microbial battery rewarded in the 1850 copy are undoubtedly much more than the technology rewards in the 1100 copy.
It's just that Xu Yun has never been very clear about the specific judgment logic of halo, so he can only bury this doubt in his heart.
Now it seems...
Perhaps the most valuable reward of 1100 copies is not technology, but...
That original formula is so complex that it’s hard to understand.
Dark matter has been discovered in one-third of it, but what about the remaining two-thirds?
At least from a mathematical perspective.
The difficulty of the last two-thirds is dozens of times higher than that of the first third.
I'm afraid that's the real treasure...
It's unclear whether or not it's possible to guess that once all the deciphering is completed, gravitons can really be produced?
Of course.
These are Xu Yun's conjectures, without any actual evidence to support them.
Compared to the original formula.
What Xu Yun needs to pay attention to at this time is still this lone particle.
If their previous results can be divided into ordinary areas, CNS.
So the discovery of dark matter...
I'm afraid it's not as simple as a certain main magazine.