1900: A physics genius wandering around Europe

Chapter 624 The universe is not a lawless place! Dark matter should also be included in the Big Bang theory! Three verification schemes!

The proposal of dark matter deeply shocked everyone present.

The name reflects its properties that are completely different from ordinary matter.

It is like a ghost floating beyond human perception, mysterious and unpredictable.

Many people think that dark matter is a concept that only appeared in later generations.

actually not.

In real history, as early as 1922, Dutch astronomer Kapteyn proposed the theory of "invisible matter" based on the anomalies in the movement of stellar bodies.

But it knows nothing about the properties of this substance, it is just a concept.

Then, in 1932, Oort proved Kapteyn's conjecture while studying the rotation of the Milky Way.

But he also did not give any further description of dark matter.

In 1933, Zwicky once again verified the dark matter hypothesis while studying galaxy clusters.

Moreover, he is quite radical and has been widely promoting the existence of dark matter, causing a stir in the astronomical community!

In later generations, some people called Zwicky "the most neglected astronomer."

Some even think he is the Einstein of astronomy!

He subverted people's inherent cognition.

But unfortunately, few people in the astronomical community at that time supported the dark matter hypothesis.

Because it is so bizarre and totally incomprehensible.

How is it possible for there to be matter in the universe that does not emit, reflect, or absorb electromagnetic waves?
Even Einstein discussed the possibility of dark matter with astronomers.

However, no definite conclusion was reached in the end.

After the 20s, astronomy developed rapidly.

As various observation methods become more and more advanced, astronomers can observe more and more phenomena.

Although dark matter does not participate in electromagnetic interactions, it participates in gravitational interactions.

Its existence can be indirectly proved through some special mechanical methods.

This is already the consensus in the scientific community.

But what exactly is the nature of dark matter?
What are the particles that make it up?
Still no one knows.

Physicists have found a number of candidate particles for dark matter, but they were all ultimately proven to be wrong.

To date, it remains one of the most mysterious phenomena in the universe.

At this moment, Li Qiwei's status and position are not comparable to Ort and Zwicky.

Moreover, he also combined the development of atomic physics, which made the dark matter theory very credible.

Recalling the predictions Professor Bruce had made before, almost half of the people present supported the dark matter theory.

At this time, the bosses gradually came to their senses.

They sincerely hope that dark matter exists because it will subvert people's understanding of the universe.

So, what the big guys are thinking about now is not questioning dark matter, but how to prove it?
And in a sense, proof is questioning.

If it cannot be proved, then the conjecture will be defeated.

Of course, it still has extremely strong theoretical reference value, at least it can explain the problem of galaxy mass.

So Haier asked:
"Professor Bruce, since the dark matter you mentioned cannot be perceived by humans at all, how can we prove its existence?"

Everyone immediately focused and looked excited.

Just kidding, if someone can perfectly prove the existence of dark matter, it will definitely be no less than other great achievements such as proving the expansion of the universe and discovering black holes.

After hearing this, Li Qiwei thought for a moment and said:

"The motions of galaxies and galaxy clusters are the most direct verification scheme."

"The next step, I think, is to do the same thing with a large number of galaxies."

"If dark matter exists, it is most likely distributed throughout the universe."

"So, phenomena like the Milky Way and the Coma Cluster are definitely not isolated cases."

"With more research, perhaps we will be able to estimate the true ratio of dark matter to ordinary matter in the universe."

Wow!
Everyone nodded.

This is another huge infrastructure project that is difficult for an individual to complete alone.

Everyone suddenly admired Professor Bruce very much for his foresight in calling for the establishment of the International Astronomical Union.

A global collaboration to explore this mysterious substance.

Under the leadership of Professor Bruce, everyone continues to unveil the mystery of the universe.

In 2006, astronomers observed the strongest evidence yet for the existence of dark matter.

It is also through mechanical methods, but it is different from galaxy spin and galaxy cluster motion.

It is a completely new mechanical phenomenon.

That was a collision between two galaxy clusters, also known as the "Bullet Cluster Collision."

This phenomenon is extremely rare and happened to be recorded by a space telescope.

The process and results of this collision perfectly prove the existence of dark matter.

The process is simply understood as follows:
Scientists have discovered a galaxy cluster they named the Bullet Cluster, which contains tens of thousands of galaxies.

Inside the Bullet Cluster, that is, between the galaxies, there is a large amount of gas matter.

After calculations, scientists discovered that the mass of these gases is more than 7 times the mass of stars.

Therefore, the material composition of the Bullet Cluster mainly includes three items: stellar matter, gas matter, and dark matter.

When the Bullet Cluster collides with other galaxy clusters, different phenomena will occur due to the differences in the properties of the three types of matter.

First, there is stellar matter.

When two galaxy clusters collide, it sounds like there will be a huge explosion that will shake the world.

For example, 50 billion years from now, the Milky Way and the Andromeda Galaxy will collide, and many people are worried that the Milky Way will be destroyed.

In fact, this is impossible.

Because the universe is too vast!

The nearest star to the Sun is 4 light-years away.

After two galaxies collide, the probability of their stars meeting each other is extremely small, and the final result is that they will pass through each other.

The effects of galaxy clusters and galaxy collisions are similar.

So, when the Bullet Cluster collided, there was almost no change in the stellar matter.

But gaseous substances are different.

It is diffuse throughout the interior of a galaxy cluster, and when a collision occurs, it interacts violently with matter in another galaxy and releases strong X-rays.

Therefore, by observing the X-ray situation, it will be found that after a period of collision, the gas matter obviously lags behind the stellar matter.

This is easy to understand, right? Stars hardly collide, so they pass through first.

Finally, there is dark matter.

Although dark matter, like gaseous matter, is diffused throughout the entire galaxy cluster.

But because it has no electromagnetic interaction, even though dark matter also undergoes violent collisions, it does not stagnate at all.

It passes through the matter of another galaxy just as easily as stellar matter, and of course is ahead of the gaseous matter in position.

With the above differences in properties, we can determine whether dark matter exists.

If dark matter does not exist, then after the collision of the Bullet Cluster, the position of its gravitational center should be consistent with the position of the gas matter.

But if dark matter exists, then after the Bullet Cluster collision, the location of the gravitational center should be consistent with the location of the stars. Finally, scientists saw the photo of the Bullet Cluster collision through the space telescope:
The red area represents gas matter, and the blue area represents the gravitational center.

Obviously, the blue area only contains stellar matter, and its gravity should be much smaller than that of the red area.

But the reality is that the gravity in the stellar region is stronger, which means there must be invisible dark matter.

At this moment, when Ridgway proposed this completely new method of galaxy cluster collision.

Everyone was shocked!

"My God!"

“This method is really ingenious.”

"If this is true, it would absolutely prove the existence of dark matter perfectly!"

But soon, everyone became a little dejected.

"But this kind of astronomical phenomenon is probably rare in a century, right?"

"Not only that, the entire collision process must be continuously observed."

“This is another huge astronomical project!”

At this moment, everyone felt emotional.

The era of working alone in astronomy will soon be over, and if we want to achieve results in the future, we must work together.

Then, Li Qiwei said:
"In addition to the above methods, I have thought of several other verification schemes."

"The first is the cosmic microwave background radiation I mentioned earlier."

"No matter how magical dark matter is, it and ordinary matter all come from the Big Bang."

"Because dark matter does not interact with photons, we can use this to directly calculate the distribution of dark matter by studying the cosmic microwave background radiation."

Wow!
Everyone was surprised again.

I didn’t expect that dark matter is actually related to the cosmic microwave background radiation.

But it’s right to think about it.

As the first light in the universe, the cosmic microwave background radiation can be said to carry all the information in the universe.

In later generations, scientists used this method to accurately measure the distribution of dark matter.

If all matter and energy in the universe are converted into energy. (excluding vacuum zero-point energy)

Then, ordinary matter accounts for about 5% of the total energy of the universe, and dark matter accounts for about 27% of the total energy of the universe. (Guess what the remaining 68% is)
The amount of dark matter is exactly 5 times that of ordinary matter.

In addition, the distribution of dark matter in the universe is not uniform, but in "clumps".

It's possible that some parts of a galaxy have a large cloud of dark matter, while other places have a lower density of dark matter.

This is also a very peculiar property of dark matter.

"Second, dark matter is likely involved in the formation of large-scale structures in the universe."

“For example, the Coma Cluster observed by Zwicky contains countless galaxies.”

"But these galaxies follow the same motion and combine to form galaxy clusters."

"Through simple simulation analysis, we know that without dark matter, it would be difficult for ordinary matter to form such a large structure."

"Because dark matter does not interact with photons, it can aggregate first on a small scale, thus promoting the formation of material structure."

After that, Li Qiwei directly carried out complex mechanical mathematical model calculations.

Everyone was stunned!

In later generations, scientists even simulated the formation process of galaxies, galaxy clusters, and larger-scale structures on computers.

The method is also simple.

After setting the parameters of the simulation program, we see how much ordinary matter and how much dark matter to add.

Then, let the program evolve naturally according to the law of gravity and see what the final result is.

The data shows that if dark matter is not added, the simulated universe will not match the observed facts.

However, after adding 5 times the dark matter, the simulation results are the same as the actual observation results.

It looks just like a chemical reaction. Perhaps the universe is a chemical reaction.

Moreover, scientists have used this method to obtain another very important property of dark matter.

That is, the speed of dark matter should be much lower than the speed of light, which is the so-called "cold dark matter".

The cold here does not mean "low temperature" in the traditional sense.

Dark matter has no concept of temperature, and you cannot feel its temperature with your hands.

Humans perceive temperature through the emission of electromagnetic waves by matter, which conducts heat away and is then picked up by human sensory organs.

Dark matter has no electromagnetic interaction, so naturally it will not transfer heat.

But after all, it is made up of material particles, and these particles are also constantly moving.

Then, based on the speed of its movement, we can "equivalently" calculate its temperature relative to that of ordinary matter.

But even if the temperature of dark matter is 1 degrees Celsius, if you hold it in your hand, you will not feel any burning sensation at all.

This property of dark matter is obtained through the study and simulation of large-scale structures.

Before computers were invented, Li Qiwei did not have the ability to tear apart this level of simulation by hand.

So, all he gave were ideas and methods.

However, this alone was enough to shock everyone beyond measure.

Finally, Li Qiwei said:
"The above are the three major verification schemes I summarized."

"Even if just one of them is achieved, I think it would be enough to prove the existence of dark matter."

"If all of this is realized, then dark matter must exist!"

Everyone's heart was boiling with excitement. What a confidence!

With Professor Bruce's amazing intuition, dark matter must exist even if it doesn't exist!
"As for what the constituent particles of dark matter are, that is a matter for physicists."

"Everyone rest assured, I will urge Professor Rutherford to study dark matter."

Everyone smiled knowingly.

Astronomy and physics are becoming increasingly connected.

Young people like Ort who have both kinds of backgrounds will become more and more popular in the future.

Hai Er suddenly sighed deeply:

"When Professor Bruce proposed dark matter, I thought it would be a challenge to the Big Bang theory."

"I didn't expect that he would perfectly integrate dark matter into the Big Bang theory and make it a part of it."

"Even if the existence of dark matter is proven, it would be equivalent to proving the Big Bang theory in disguise."

“It’s just so clever!”

Haier's words shocked everyone.

If you think about it carefully, this is indeed the truth.

At this moment, everyone had a new understanding of the Big Bang theory.

It is simply the ultimate framework for astronomy.

Planets, stars, galaxies, galaxy clusters; matter, antimatter, dark matter; time, space.
Everything is included in the Big Bang Theory.

The two pillars of modern physics: relativity and quantum mechanics, only explain the effects of the aftermath of the Big Bang.

Suddenly, the big guys present looked excited:
"The end of physics is astronomy!"

"Astronomy is the first of natural sciences!"

(End of this chapter)