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

Chapter 692 The Strongest Doctoral Dissertation

Wu Youxun’s problem is actually relatively easy to resolve. After all, as long as there are successful experimental results, it won’t take long to be recognized.

The other group had a more difficult time.

After Li Yu, Compton and Wu Youxun returned to the University of Chicago, they went to attend a very unpopular seminar about Wegener and Zhang Xiangwen's continental drift theory.

The relationship between these two people is much better than Li Yu imagined. It may be that they appreciate each other because almost no one believes in the fantastic theory of continental drift.

Every few words they say will lead to opposition or even ridicule.

"We can see exactly the same fossils on different continents, and they shouldn't be so similar... So we assume that tens or hundreds of millions of years ago, the Earth might not be what it is now, but a whole continent..."

"Nonsense!" said physicist Harold Jeffreys. "Your theory has obvious flaws. For example, what force drives the continents to drift? You can't say it's ocean currents, right?"

“We don’t know yet.”

"Don't know? That's science fiction and shouldn't be considered a scientific result!" said T. Chamberlin, a professor at the Department of Geology at the University of Chicago. "The theory of continental drift sounds more like an unrestricted and boundless guess. To achieve the result of drift, the earth needs to have a considerable degree of freedom. Compared with other theories, this theory is not bound by the real world, so it is absurd!"

Paleontologist Shukert said it more bluntly: "The theory of continental drift is just a beautiful dream. The evidence of a few paleontological fossils is not enough to overturn everyone's cognition. Moreover, you are not professional paleontologists. A layman transplanting the facts he has mastered from one discipline to another will obviously not get the correct results."

……

In short, I hardly hear anything I believe.

The seminar lasted less than an hour before everyone dispersed, except Li Yu who stayed.

"It seems that the conclusion is still far from enough." Li Yu said.

Zhang Xiangwen said bitterly: "It should be said that although there is a lot of progress, it is not recognized."

Wegener himself was equally frustrated: "The professor of paleontology even treated our discovery as a joke in class rather than a scientific deduction."

"And we really have no idea what's driving this continental motion," Zhang said.

"There are many unknowns, which means the theory is still developing," Li Yu encouraged. "As for the source of power, it is indeed a troublesome problem. Perhaps you can start from the perspective of volcanoes, magma, earth structure and even thermodynamics."

Wegener said: "Mr. Academician, your suggestion is very good, but your words involve several disciplines, and the difficulty of research has increased by several orders of magnitude. It seems that if we want to complete this task, it is not something that a few people can do in a few years or even more than ten years."

Li Yu smiled and said, "Every theory is like this. As long as there is hope, that's enough."

It wasn't until the 1950s and 1960s that more evidence began to emerge for the theory of continental drift, so we can only support it for now.

And even if the mainstream academic community does not support it, that does not necessarily mean that everyone is against it. There is still a small number of people who support it, but their voices are relatively small.

-

University of Paris, France.

"Professor, this is my doctoral thesis, please take a look at it," said de Broglie.

Lang Zhiwan looked at the manuscript in front of him and asked, "The formal paper has been completed so quickly?"

"With the foundation of the previous three short papers, my matter wave theory has become very mature," said de Broglie.

It has been circulated on the Internet that de Broglie's paper is only one page long. In fact, it is impossible to imagine. The original manuscript of the paper retrieved from the Internet is more than 100 pages long, and the translated English version is nearly 80 pages long.

The reason why everyone thinks only one page is needed is that they are looking at it from the perspective of a hundred years later, and in a not very rigorous way.

Because the core content of de Broglie's paper is easy to explain, it is obtained by combining the two equations of the photoelectric effect and the mass-energy equation. To put it this way, it will not take up a whole page, three lines are enough:

E=hν
E=mc2 (mass-energy formula, 2 is the square)
Then we get ν=h/mc2
“The theoretical derivation looks very good,” Langevin said.

De Broglie said: "Like Mr. Li Yu, Mr. Einstein and Mr. Bohr, I am biased towards theory. And my theory can perfectly explain why the orbit of electrons is discontinuous and can only be a specific orbit."

"Is it because electrons have wave properties?" Langevin said.

"Yes, professor," said de Broglie. "No matter whether the electron's orbit is circular or elliptical, because of its wave properties, the electron's orbit can only form specific standing waves, that is, integer multiples of certain specific values. And integer multiples are just borrowed from quantum theory."

Langevin pondered for a long time and said, "I can find no fault with your theory, but the University of Paris does not have a tradition of studying quantum mechanics, which is something the Germans love to do. If I go into the doctoral defense, I am worried that I will encounter problems."

"What's the problem?" asked de Broglie.

“The most direct issue is how to conduct experimental verification?” Langevin said. “Even if I agree to pass, there are still four other defense supervisors who may not agree. They may even wonder why you want to study this field that few people in France are exposed to.”

De Broglie said: "I just had this sudden idea after reading some literature."

Lang Zhiwan said: "Your sudden idea is so bizarre that I will also seek help from some professors and experts in this field."

I guess many people have discovered that many big names in quantum mechanics are German.

This does not mean that only Germans are excellent. It is simply because communications were too underdeveloped at that time and development in different regions was even more uneven, so many theories were confined to small circles.

Moreover, even in Germany, there is obviously a minority of college students pursuing scientific research, and subjects such as quantum mechanics and atomic spectrum lines seem to be extremely difficult to understand.

Quantum mechanics was born in Germany, but most people in the German physics community have never paid attention to quantum mechanics and atomic spectra.

For example, in 1920, only a tiny minority of all German university students - perhaps 8% - studied science, and even fewer studied physics.

In the year when quantum mechanics superstar Heisenberg graduated, the University of Munich awarded a total of 337 doctorates, of which only 19 were scientific degrees.

The Americans once funded a project to organize historical materials on quantum mechanics, the main purpose of which was to study the development of quantum mechanics from 1900 to 1930. It was found that it was sufficient to limit the sources of historical materials to just two hundred people.

You know, quantum mechanics is one of the two most brilliant fields of physics in the first half of the 20th century, but there are only such a small group of people. But it seems that it is this small group of people who have brought human understanding of physics to the next era.

With fewer people, the circle is smaller, and the research on quantum mechanics is concentrated in three places: Göttingen, Munich and Copenhagen.

People who work on quantum theory basically cannot escape this small range.

Even a country as strong as France is like a desert in the quantum field.

The appearance of de Broglie was very much like an "outsider" who accidentally entered the quantum world - at that time the focus of the French scientific community was not on the quantum field and relativity.

Lang Zhiwan is definitely not working in the quantum field. Although he can understand the paper, he cannot give more constructive suggestions.

"You can print a few more copies of the thesis and send them to Mr. Einstein and Mr. Li Yu respectively. If they say there are no problems, the chances of this doctoral thesis passing the defense will be greatly increased."

"Write in German and English?" asked de Broglie.

"You can translate it into English, it's not difficult; as for German, I can help you," said Lang Zhiwan.

-

A few days later, Li Yu received letters from de Broglie and Langevin.

De Broglie's letter was accompanied by an entire doctoral thesis, and Li Yu was fortunate enough to read the only doctoral thesis in history that won the Nobel Prize in Physics.

It's still very solid, but... it just seems like there's too much nonsense. Of course, this can't be blamed on de Broglie. After all, Li Yu is a time traveler, and many theories are obvious to him and don't need to be proven.

Langevin's letter is more interesting:

“Dear Mr. Li Yu, hello, one of my students, de Broglie, wrote a very interesting paper. He believes that particles are also a kind of wave. Since it involves quantum-related issues, I hope you can help review it.

"P.S.: This student comes from a duke family. His grandfather was the prime minister and his father was a minister. If you come to France again, I will invite you to enjoy the beautiful scenery of France."

Langevin's affirmation of Einstein was roughly the same.

Li Yu was immediately amused. Lang Zhiwan was indeed a man with high emotional intelligence.

In fact, after he accepted de Broglie as his doctoral student, he did not pay much attention to him and let him develop on his own, which is why de Broglie read articles in the quantum field without any focus.

At first, Langevin did not think much of this student, because de Broglie was not a pure physics major. He had previously obtained a bachelor's degree in history from the University of Paris, and his research was on medieval history, such as werewolves, witches, and vampires. Later, because his brother was a physicist, he was influenced by him and "changed his career".

Langevin would not demand too much from a son of an aristocratic family. Moreover, the dukedom of the de Broglie family can be traced back to the reign of Louis XIV, when France was the hegemon of continental Europe. The title of duke was of high value and could not be compared to the various titles of the scattered small states in Germany.

The period when Louis XIV was in power was close to the Kangxi period of the Qing Dynasty. If we make a forced analogy, the de Broglie family can be called the "iron-hatted king" of France.

Of course, Li Yu would not "look down" on someone just because of his family background. De Broglie's doctoral thesis was absolutely amazing and introduced many advanced ideas. For example, it profoundly revealed the universality of the core idea of ​​quantum mechanics, the wave-particle duality.

If quantum mechanics before de Broglie was the "old quantum era", then after the proposal of matter waves, quantum mechanics officially entered the "new quantum era".

Thanks to the work of Compton and Wu Youxun, the wave-particle duality of the special particle, photon, was fully verified in experiments, and de Broglie dared to continue thinking.

-

The day of de Broglie's doctoral thesis defense at the University of Paris.

Including Langevin, there were a total of five professors from the University of Paris who were responsible for the defense. Among them were two who were experimental physicists, and the other was Jean Perrin, who would soon win the Nobel Prize.

De Broglie first elaborated on several key points in the paper, and then, without waiting for others to ask questions, Langevin stood up and said, "I have two letters here, one from Mr. Li Yu and the other from Mr. Einstein. I would like to read them aloud.

"Mr. Li Yu said in his letter, 'De Broglie's paper is very forward-looking. I not only agree with it, but also think highly of it.'"

"And Einstein wrote, 'De Broglie's work seems to be the beginning of a new chapter.'

"..."

Several professors looked at each other. They had many questions they wanted to ask, but Lang Zhiwan suddenly brought up Li Yu and Einstein's opinions. What else could they say?

People who specialize in the quantum field have spoken. If you oppose it, doesn't it mean that you don't understand it?

So several professors said, "We all think there is no problem with this paper. You can pass the defense and get a doctorate degree."

Lang Zhiwan was very satisfied, "I knew you would not have any objections."

Jean Perrin was more rigorous. He said, "I only ask one question: how do you verify your idea that electrons also have wave properties through experiments?"

De Broglie came prepared and replied calmly: "We can use crystals to verify the diffraction of electrons. Because the wavelength of electrons is very short, it is difficult for us to make such a small grating, and neatly arranged crystals are the best tool."

Jean Perrin thought de Broglie's answer made sense, so he closed his paper and said, "Okay, I have no doubts. Your paper will pass!"

De Broglie's experimental idea was very accurate. Just two years later, Davis of Bell Laboratories in the United States completed an electron diffraction experiment using silicon crystals by accident. Almost at the same time, Thomson's son George Thomson also discovered the diffraction pattern through other methods.

As a result, these two people won the Nobel Prize in Physics - the Nobel Prize attaches great importance to both theory and experiment, which once again proved that there was nothing wrong with Wu Youxun winning the prize.

Moreover, the electron wavelength calculated by Davis and George Thomson through experiments was exactly the same as de Broglie's theoretical calculation.

As a result, de Broglie won the Nobel Prize in Physics for the first time with a doctoral thesis.

The application of matter wave theory is quite important. The later transmission electron microscope used the property of the relatively short wavelength of electrons: when the wavelength is short enough, the transmission electron microscope can achieve very high resolution.

In addition, the wave-particle duality is infinitely mysterious and has now been extended to massive particles and even macroscopic objects, so you... have also become light!
But having said that, although de Broglie opened up a new quantum field, he still believed in determinism. Later great philosopher Schrödinger also believed in determinism. Both of them stood in Einstein's camp and did not agree with Bohr's probabilistic explanation.