A Man of Science and Engineering in Troubled Times Wandering in the Late Qing Dynasty

Chapter 705 Goodbye, Great Gods

" GENERAL CHIANG KAI-SHEK
Rose out of the Sun-set. ”

Li Yu was reading the cover article of Time magazine on the ship and knew that the biggest historical turning point of the Republic of China was about to come.

Since Chiang Kai-shek entered Shanghai as the commander-in-chief of the Northern Expedition, he immediately attracted worldwide attention and appeared on the cover of Time for the first time.

Unlike the article about Wu Peifu published at that time, Time's introduction to Chiang Kai-shek was relatively concise. The two sentences in English above are Time's concise comments on Chiang Kai-shek.

The first line means General Chang (Wei's spelling) Kaishen;
The second line means that Chiang Kai-shek rose after Mr. Sun fell. The word "Sun" is a pun, referring to both Mr. Sun and the sun.

This time, Time's vision was more accurate. Unlike the last time, when it reported on Wu Peifu, he fell from power within a few months.

Chiang Kai-shek at this time had an army of more than 200,000. Even after the Ning-Han split with Wuhan, his strength was not affected in the slightest.

Europe and the United States were very optimistic about him and were at the same time prepared to give up Zhang Zuolin in the north.

In short, the storm is coming.

-

Zhao Zhongyao, who was standing by, saw Li Yu in a daze and asked, "Mr. Academician, what are you thinking about?"

Li Yu said: "Nothing, I just feel that the sea breeze is colder this year."

Zhao Zhongyao said with emotion: "I don't know much about meteorology, but I am afraid that abnormal astronomical phenomena will cause another severe drought in the country. The North-South War is imminent. If a major disaster occurs at this time, I don't know how many people will die."

In fact, a serious disaster will occur next year, and millions of people will starve to death across the country. The worst hit is Shaanxi, where nearly 70% of the population will be displaced.

Li Yu said: "I bought a lot of food, hoping to at least reduce some unnecessary casualties."

Disasters are inevitable, and they happen every ten years or so. But before Li Yu traveled through time, even if there were severe floods or droughts in some years, no one had ever starved to death, because there were a lot of grain reserves, and even if there was a disaster in the country that caused a significant drop in grain production, more grain could be purchased from the international market. Disaster resistance is incomparable.

Li Yu then asked, "Which university in the United States do you want to attend?"

Zhao Zhongyao said: "My overseas study expenses are provided by your foundation, and I will listen to your advice."

Li Yu thought for a moment and said, "Let's go to Caltech and join Professor Millikan. He is now the most powerful physics professor in the United States."

The current strength of Caltech is not very strong, but Zhao Zhongyao still nodded and said, "I like California, too."

When the ship arrived in Los Angeles, Li Yu went to California Institute of Technology with him.

Millikan readily accepted Zhao Zhongyao as his doctoral student.

Li Yu smiled and said, "The student Wu Youxun whom I recommended last time has been nominated for the Nobel Prize in Physics. Maybe the same will happen to Student Zhao."

"It's not that simple. In my opinion, the Nobel Prizes in recent years have all been won by those Europeans!" Millikan complained again, "The Nobel Committee is paying more and more attention to theory, which is not good for the development of physics."

Li Yu spread his hands and said, "This suggestion is that Professor Millikan should file a complaint directly with the Swedish Academy of Sciences."

"Forget it!" Millikan said helplessly.

"Professor, you can learn about the currently popular quantum theory. Maybe you will like it," said Li Yu.

"I don't like those lengthy mathematics and formulas," Millikan said firmly. "I share the same philosophy as the Cavendish Laboratory. Experiments are the tool to uncover the mystery of nature."

"Well, of course this sentence is not wrong." Li Yu said.

After signing the admission documents, Zhao Zhongyao couldn't wait to ask Millikan about his doctoral research topic.

Millikan picked up a notebook on the table without hesitation: "You should try this thesis on optical interferometer first. As long as you can measure the annual change of the pattern on the optical interferometer, you can get a doctorate in two years."

Millikan actually intended to give Li Yu face by choosing a simple topic. After all, after decades of research by Michelson, optical interferometer had become a very mature direction, which allowed Zhao Zhongyao to easily obtain a doctorate degree.

But Zhao Zhongyao himself seemed to not understand and suddenly said, "Professor, this kind of research is too simple. I came to the United States not just for a diploma, I want to learn some real skills. So... can we change to a more difficult and cutting-edge topic?"

Millikan was surprised and asked, "Change the subject?"

According to the practice of universities and workplaces in Europe and the United States, students have to do whatever topic the instructor assigns them, especially if it is the first assignment.

Similarly, when receiving the first recommendation letter in the workplace, job seekers generally cannot refuse the content arranged in it.

This is an old tradition of human relationships in Europe and the United States that has been around for hundreds of years.

Zhao Zhongyao didn't know this and said resolutely, "Yes, Professor."

Li Yu smiled and said, "Mr. Millikan, it doesn't matter if it's a little difficult."

Seeing that Li Yu had spoken, Millikan said, "Okay, but the other experiment will be much more difficult to do."

He changed to another notebook. "This topic is to study the measurement of the absorption coefficient of gamma rays passing through matter and verify the Klein-Nishina formula. It involves a lot of the latest physics content, and there is not much material to use for reference."

Zhao Zhongyao knew that he couldn't refuse Millikan twice, and this sounded difficult, so he said, "Thank you, Professor."

Li Yu's eyes lit up. It was through this experiment that Zhao Zhongyao discovered the annihilation phenomenon of positrons and electrons two years later. It was also the first time that humans discovered the positron.

This time was even earlier than Dirac's prediction of the positron. But because it was too early, Zhao Zhongyao and Millikan could not believe it.

——In fact, even after Dirac made his prediction, experimental physicists would basically not read the papers of theoretical physicists in time.

Moreover, the theoretical physics that Dirac was working on was considered very basic by theoretical physicists, so it is indeed quite difficult to understand his papers.

People always say that different fields are like different worlds. In the current physics community, this even applies to experimentalists and theoretical researchers.

Historically, it took 15 months for the positron to be discovered after Dirac made his prediction. If the person who made the prediction was an experimental physicist, it might have happened much faster.

As for the so-called Klein-Nishina formula, you don't need to care too much about it. You just need to know that it is used to study whether electrons and protons are the components of atomic nuclei in atomic physics, as well as some theoretical verifications about β decay.

This formula is a further derivation of Dirac's formula. Anyway, it is quite complicated and the experiment is difficult to do. Zhao Zhongyao has worked hard in the past two years.

-

After arriving in New York, Li Yu first looked for the latest physics journals in the bookstore, and finally saw Heisenberg's article "On the Perceptual Content of Quantum Theory Kinematics and Mechanics".

Heisenberg had by then figured out the physics of PQ-QP, and this 27-page paper from Copenhagen outlined Heisenberg’s most famous and influential contribution to physics: the uncertainty principle (formerly known as the uncertainty principle) in quantum mechanics.

It basically completes the overall framework of quantum mechanics.

It was originally called the uncertainty principle because the example Heisenberg gave was also a thought experiment:

If you want to measure the exact position of an electron, you need an electromagnetic wave with a very short wavelength to illuminate it, but the energy of such electromagnetic waves is relatively high. According to the law of conservation of energy, the momentum of the electron will deviate greatly after the collision.
However, if you want to measure the momentum of an electron, you have to use electromagnetic waves with a longer wavelength. Such electromagnetic waves have low energy and the measured position will be inaccurate.

Anyway, it is a contradiction. If you want to measure one accurately, you cannot measure the other one accurately.

These two quantities are called "conjugate physical quantities" in physics. In addition to speed and momentum, time and energy are also conjugate physical quantities. That is, the more accurately the time is measured, the less accurate the energy, and vice versa.

The uncertainty principle has risen to a philosophical level and is extremely important to the theoretical foundation of quantum mechanics.

At present, Heisenberg is still having a small-scale quarrel with Schrödinger. The two of them have been arguing fiercely over the past year over which one is the best in the world, matrix mechanics or wave mechanics.

It seems that most physicists now stand on the side of wave mechanics. After all, differential equations are much more useful than matrices.

Heisenberg himself was quite depressed about this, especially when he found that some physicists were actually rewriting old matrix mechanics papers using the language of wave mechanics!
Heisenberg often complained publicly: "Now for every matrix paper there are physicists writing a corresponding 'conjugate' wave paper, and this annoys me. I think they had better learn both!"

This is also quite rare in physics: theoretical resources are beginning to overflow.

In most similar situations in the past, physicists had to make do with the lack of a theory; but now it is different, they have discovered that there is actually a spare theory!
However, the argument about this was about to be put to an end by another great figure - the taciturn and silent Dirac, who developed the transformation theory.

It just so happens that everyone is in urgent need of a theory that combines wave mechanics and matrix mechanics, while also integrating the different interpretations of the two.

In addition, although Heisenberg's matrix mechanics and Schrödinger's wave mechanics are slightly different in mathematical form, they are another matter in terms of the understanding of quantum mechanics.

Heisenberg must have been a staunch supporter of the theory of discontinuity.

But Schrödinger still insisted on continuity, that is, he tended towards volatility.

In this regard, more people stood on Heisenberg's side. After Li Yu gave the probability explanation, more people supported Heisenberg.

For example, Pauli, the "God of Disagreement". Pauli wrote directly to Schrödinger, telling him that he must introduce a kind of discontinuity into the understanding of quantum physics, and that continuous physics alone would not work. Although he would be tortured by this, it was unavoidable.

Pauli's status at this time was not as important as Schrödinger's, but since he was Heisenberg's classmate, he had to help him.

(One additional point: Born did not give a probabilistic explanation on his own in history. His original interpretation was that the Schrödinger wave function was a probability wave, not a matter wave as Schrödinger said; the square of the wave function represents the probability of a transition to a certain quantum state in the collision of two electrons.

Later Pauli reinterpreted Born's interpretation, arguing that it represents not only the probability of the outcome of a collision, but also the probability of finding the electron in a certain quantum state of the atom at a certain moment.

Pauli was the first to say to Heisenberg: "It is therefore impossible to speak of the exact path of a particle, nor to determine both momentum and position at the same time."

I almost forgot the contribution of the great god.

All I can say is that Pauli was really very capable. It is no exaggeration to say that he was extremely talented among all the top physicists. Unfortunately, his strong abilities and even stronger personality led him to miss out on many great discoveries.)
In short, the love-hate relationship between Schrödinger and Heisenberg was the main theme in the physics community in the past one or two years - but it was overshadowed by another major debate at the fifth Solvay Conference a few months later.

But Schrödinger and Heisenberg undoubtedly provided both camps with extremely powerful theoretical weapons.

In terms of positions, the two are not much different - Schrödinger is a little higher, having become the highest-ranking theoretical physicist in Europe, professor of physics at the University of Berlin.

Heisenberg also received many offers. Among them, Sommerfeld most wanted him to go to the University of Munich, first as an associate professor, and then to succeed him in the future. Heisenberg himself also liked Munich.

However, Heisenberg had already become famous at a young age. If he did not want to be an associate professor for two years, he could have gone to other universities to be a full professor first, and then become a full professor at the University of Munich in the future.

So Heisenberg chose to be a professor of theoretical physics at the University of Leipzig, and he should be the youngest full professor of physics in Germany.

-

Before going to continental Europe, Li Yu passed through the UK as usual, after all, there is a group of big names in Cambridge.

The "Kapitsa Squad" still welcomed Li Yu very much. Dirac, Oppenheimer, Kapitsa and others warmly greeted him at the dock. Among them was Kapitsa's newlywed wife, an exiled Russian artist, the black-haired beauty Anna.

"Have you two returned from Göttingen?" Li Yu asked Dirac and Oppenheimer. He had always kept in touch with them via telegrams and letters.

"I have defended my doctorate in Göttingen and am returning to Cambridge," Oppenheimer said.

"It went so smoothly." Li Yu said.

Kapitsa was the talkative one: "Actually, the defense teacher couldn't stand Oppenheimer anymore! Haha!"

James Franck and Born presided over Oppenheimer's defense. Franck asked questions for only 20 minutes before the defense was over. Afterwards, Franck said to Born, "I'm so glad the exam is over. If it hadn't ended, he would have asked me questions instead."

Born was actually relieved, because he really wanted to get rid of this smart but troublesome student. In the letter to Ehrnfest (who was also in the photo of the Fifth Solvay Conference) and Thomson, Born deliberately added a paragraph at the end:
"I must let you know what I think of him (Oppenheimer). I openly admit that no one has ever given me as much headache as he has, and of course I don't want this to affect your personal judgment of him. He is undoubtedly talented, but he lacks psychological control. He appears easy-going, but is very stubborn and arrogant inside. ... For three semesters in a year, he made all of us very frustrated. Only after he left did I feel I could breathe and have the courage to continue working."

As for Dirac, he was certainly a good student who was likable.

Dirac rarely spoke unless he took the initiative to talk to him, so Li Yu asked, "Mr. Dirac, I heard that you plan to combine quantum theory with Einstein's special theory of relativity?"

Dirac said, “Yes, I want to use this to describe the behavior of isolated electrons.”

Li Yu rubbed his chin. "The quantum theories of Heisenberg and Schrödinger both have flaws because their theories do not follow the special theory of relativity. If the observers move relative to each other at different speeds, the results will be inconsistent with the results derived from the equations of the two theories."

“I’ve got some ideas about this,” Dirac said.

Li Yu smiled and said, "Then you'd better hurry up, otherwise you will be one step behind others and won't even have the chance to share in their success."

Dirac trembled: "I'll go back now!"

Kapitsa immediately reached out and grabbed him: "Then you have to go together!"