1900: A physics genius wandering around Europe

Chapter 664 "You, go and kill the brute force!" A groundbreaking topic! Meson theory! The prelude to particle physics!

Inside the Wuya Pavilion.

Li Chengdao looked excited and was breathing rapidly.

Even though he is usually very composed, he couldn't control himself at this moment.

The ambition of young people to soar to great heights cannot be suppressed by willpower.

He knew all too well what the task his father had given him meant.

Zhao Zhongyao, who is currently enjoying unparalleled success, is the best proof of this!

"No wonder I had that strange dream; it was a premonition for today."

Li Chengdao's brain was working frantically.

Seeing his son's excited expression, Li Qiwei was filled with emotion.

He went to great lengths to cultivate the other person, and the topic he chose was also carefully considered.

"You're still in school, you don't have time to do experiments."

"Therefore, I am giving you a topic in pure theoretical physics, which does not require experiments."

"You can think anytime, anywhere after you finish your schoolwork."

Li Chengdao's eyes are bright; this is definitely good news.

He was very moved. Without a doubt, this was a topic that his father had carefully selected for him.

"Okay, Father."

Then, Li Qiwei raised another question:
"You should know about my previous publications on quantum field theory and quantum electrodynamics."

What is your understanding of this theory?

hiss!
Li Chengdao gasped, his heart trembling uncontrollably.

God!

Does my father want me to study quantum field theory?
This is too scary.

However, this was not the time to be shocked. He quickly regained his composure, thought for a moment, and said:
"I have read commentary articles written by Professor Bohr, Professor Einstein, and others."

"They believe that quantum field theory is a theory that aims to encompass all existence."

"Under this idea, the field is the highest existence, all matter is born from the field, and the world model becomes simpler and clearer."

Li Qiwei nodded.

The eldest brother has a decent understanding of quantum field theory.

However, Li Chengdao then changed his tone, saying:

"However, I personally believe that quantum field theory seems to involve a kind of helpless compromise."

“Father, you once raised the remaining questions of classical physics at the first Bruce Conference.”

"One of the problems is the existence of the field."

"It's too special. It has absolutely nothing to do with classical physics, quantum mechanics, or relativity."

"So you wanted to incorporate fields into quantum mechanics, and that's how quantum field theory came about."

Ok?
Li Qiwei's expression shifted.

It seems that the eldest brother has indeed made progress during this period and has even developed his own independent insights.

Incorporating fields into quantum mechanics was a last resort, but the results were surprisingly pleasant.

"Not bad!"

"The fact that you can think like this proves that you usually pay close attention to the development of physics."

Hearing his father's praise, Li Chengdao smiled happily.

Li Qiwei said quietly:

"Physics requires constant experimentation."

"No one can guarantee that a new theory is right or wrong."

"What we can do is keep using theory to describe the world, modify and patch it until it is perfect."

"Quantum field theory is no exception."

Li Chengdao nodded.

He said wistfully:

"Everyone says that quantum field theory is the most promising ultimate theoretical framework!"

Upon hearing this, Li Qiwei smiled slightly, and an aura of boundless loftiness spread out.

Li Chengdao was immediately startled, sensing a supreme and sacred meaning within it.

Then, Li Qiwei finally said seriously:
"The topic I'm giving you is related to quantum field theory."

"My quantum electrodynamics can now explain the interaction between electromagnetic force and charged particles very well."

"However, there is no suitable and corresponding theory for the three forces of gravity, strong force, and weak force."

"This topic is related to strength."

"I hope you will use the ideas of quantum field theory to study how the strong force works."

hiss!
Li Chengdao was completely dumbfounded!
He thought he was about to take off, but the result was a huge surprise.

His father actually wanted him to use the ideas of quantum field theory to research power?

What's the difference between this and the Nine-Headed Insect telling Benboerba: Go and get rid of Tang Sanzang and his disciples?
In today's physics community, probably all the big names are studying this problem.

Not only the strong force, but also the weak force and gravity have been explored.

Any breakthrough, however small, would make a Nobel Prize a certainty.

Faced with such an enticing prospect, who wouldn't want it?
But wanting to do something is one thing; being able to actually do it is another.

Li Chengdao swallowed hard and said embarrassedly:

"Father, isn't this a bit too difficult?"

He obediently admitted defeat in front of his father; there was nothing shameful about it.

Li Qiwei smiled and said:
"Haha, don't worry, your father is here."

“I have some ideas, but I don’t have time to think about them in depth, so I thought I’d hand them over to you.”

"If you're afraid it'll be difficult, then I'll give it to someone else."

Wow!
Li Chengdao was immediately startled!
Now that the father has a direction, what is he afraid of?

Even if there's a book of cryptic knowledge right in front of him, he'll still try to understand it.

So he quickly changed his words:
"no no!"

"I can overcome any difficulty!"

"Father, please leave it to me!"

Li Qiwei was just teasing him on purpose, and laughed:
"it is good."

Then he began to explain:

"In quantum electrodynamics, I proposed a model of electromagnetic interaction, which is that two charged particles interact by exchanging photons."

"This is also the core idea of ​​quantum electrodynamics."

"So, is the situation similar for 'powerful'?"

"The atomic nucleus is composed of protons and neutrons. Is it possible that the interactions between protons, between protons and neutrons, and between neutrons are also achieved through the exchange of some kind of particle?"

"You can continue your research along this line of thought."

Wow!
Li Chengdao was deeply shocked!
He knew very well what kind of earthquake these few words would cause if they reached the physics community!
This is absolutely the best and most cutting-edge prediction of power in the world today!
Now, his father has told him this idea in person.

It's fair to say that the door to the Nobel Prize is right in front of us.

Whether he can push the door open and get in depends on his own skill.

This was a test from his father, a test imbued with boundless expectations.

At this moment, Li Chengdao's expression was solemn, and he said firmly, "Father, I will do my best to study this problem."

Li Qiwei nodded in satisfaction.

This topic is extremely important, as it is the precursor to the Standard Model of particle physics.

In real history, after Dirac, Heisenberg and others created the idea of ​​quantum field theory, it immediately became popular in the physics community.

In the 1930s and 40s, the strong and weak forces also began to come into the view of physicists.

Therefore, it is natural that some people want to use quantum field theory to explain the strong and weak forces.

As mentioned earlier, the theory explaining the strong force in the Standard Model is quantum chromodynamics, which is based on quarks.

However, quarks had not yet been discovered at that time, so quantum chromodynamics could not have been born.

Therefore, the strong force is described by another theory: the meson theory, which is the precursor to quantum chromodynamics.

The proposer of the meson theory was Hideki Yukawa (Hideki Ogawa), who came from the Sakura clan.

He studied under Hantaro Nagaoka and Yoshio Nishina, and was hailed as a physics genius of the younger generation of the Sakura clan.

In 1935, 28-year-old Hideki Yukawa published a paper entitled "On the Interaction of Elementary Particles" in a magazine in Sakura Province.

The paper's title was unremarkable, but its content was shocking.

In the article, Hideki Yukawa proposed the existence of a "meson" that can transmit the interaction between nucleons.

The term "nucleon" refers to the protons and neutrons that make up the atomic nucleus.

In the Standard Model of particle physics, we often hear about various "particles," each with its own special historical significance.

(A detailed explanation will follow later; this is just a brief introduction.)
In the early days, before the Standard Model was fully developed, as more and more particles were discovered, physicists divided all particles into two types: baryons and leptons.

As the name suggests, baryons are particles with relatively large masses, such as protons and neutrons.

Leptons are particles with relatively small mass, such as electrons and neutrinos.

Hideki Yukawa calculated from his theory that the particle that transmits the strong force has a mass 273 times that of the electron (the mass of the proton is 1836 times that of the electron).

This mass is neither too large nor too small, so it is called a "meson," meaning a particle between a baryon and a lepton.

The meson theory shocked the physics community as soon as it was proposed.

Many experimental physicists have embarked on the search for mesons.

In 1936, Anderson discovered a new particle in cosmic rays with a mass approximately 207 times that of an electron.

At the time, he was excited, thinking that this was the meson that Hideki Yukawa had predicted, since the quality difference wasn't that significant.

Therefore, he named this particle "muon".

However, it was soon discovered that the interaction between this muon and the atomic nucleus was extremely weak, and it was impossible for it to transmit the strong force.

It was later proven that the muon was not a meson at all, but a completely new type of lepton, and was therefore renamed "muon".

To put it simply, a muon is a larger version of an electron, and it is one of the 61 fundamental particles in the Standard Model.

The search for mesons has not stopped.

In 1947, British physicist Powell finally discovered a new particle with a mass 273 times that of an electron in cosmic rays.

This mass is exactly the same as the theoretical calculation, and this new particle will interact strongly with the atomic nucleus.

It was soon proven to be the meson predicted by Hideki Yukawa, and was named the "π meson".

With this, Hideki Yukawa's meson theory was widely recognized, and he was awarded the Nobel Prize in Physics in 1949, becoming the first member of the Sakura clan to win a Nobel Prize.

Powell, who discovered the π meson, was awarded the Nobel Prize in Physics in 1950.

Furthermore, the π meson officially opened up a branch of particle physics, and Powell is known as the father of particle physics.

This demonstrates the importance of meson theory.

At this point, some people may have questions:
"Wait a minute, didn't we say that gluons are the ones that transmit the powerful force?"

"How come it's become a wasp again now?"

This is the difference between meson theory and quantum chromodynamics.

The latter was developed based on the former.

We know that each proton or neutron is composed of three quarks.

The reason why protons and neutrons can remain stable individually is due to the interaction between the three quarks, and the particle that transmits this interaction is the gluon.

To put it simply, a triangle is the most stable shape.

You can think of gluons as particles like photons; they have no mass.

But some people have a question: if quarks are inside protons, then the attraction between protons, that is, the strong force, is on the outside. How do quarks affect it?

This is the situation.

The interaction between quarks produces a "dispersion effect".

That is, this force can penetrate a very small distance outside the proton, which is exactly the range of the strong force.

It is precisely because of this dissipated force that the protons and neutrons are firmly bound together, exhibiting the effect of the strong force.

During this process, mesons are produced.

Therefore, Hideki Yukawa's meson theory essentially describes the portion of force that dissipates when gluons transmit the strong force.

Therefore, it is the foundation of quantum chromodynamics.

After all, quarks didn't exist in Hideki Yukawa's time, so he could only consider the transmission of the strong force from the perspective of protons and neutrons as a whole.

Even though it was eventually replaced by quantum chromodynamics, the importance of meson theory is undeniable.

It was because of its emergence that particle physics began to develop rapidly, with various new theories and phenomena emerging one after another.

As for the weak, that's a completely different story.

Because the weak force is a phenomenon occurring within a single neutron or proton, it is very different from the strong force.

At this moment, the topic that Li Qiwei assigned to his boss was Hideki Yukawa's meson theory.

Once Li Chengdao can overcome this problem, he will instantly become a top physicist.

His father's name will no longer be a burden for him, but a legacy and an honor!
Hideki Yukawa: You father and son have such a deep bond, has anyone considered my feelings?

Li Chengdao saw expectation and affection in his father's eyes.

He had a happy smile on his face and was full of energy, wishing he could sleep only 2 hours a day.

Having a goal completely changes a person's spirit and energy.

Li Qiwei noticed his excitement and smiled as he advised him:
"Don't be anxious, take your time."

"The mathematical knowledge involved may be quite profound."

"You need to expand your math skills outside of class."

Based on what he's learned over the past few days, he believes that Li Chengdao's math skills are still lacking.

"This is also an essential path for any outstanding theoretical physicist."

"You can ask your fifth senior brother for more advice. His math skills are excellent, and he is good enough to be your teacher."

Li Chengdao nodded vigorously.

In terms of starting point for academic research, he claims to be second to none in the world.

He was not a pedantic person who would ignore a mountain of gold.

"However, Senior Brother Qian is very busy lately, so I won't bother him unnecessarily."

Li Qiwei nodded.

"In the early stages, you must figure things out on your own, and never give up no matter how difficult it is."

"Only when you are completely clueless should you ask for help, and that is when it will be most effective."

"If even the Fifth Master doesn't know, then come find me."

Li Qiwei thus taught Li Chengdao his experience step by step.

He believed that the other party would definitely be able to overcome his limitations!
"Dao'er, I really like you!"

(End of this chapter)