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

Chapter 696 Unsolved Case
Doing research is a really boring process.

Dirac was immersed in the research of PQ-QP and seemed even more withdrawn. He went back and forth between the library and the cafeteria every day and had no time to talk to other people. He also did not attend Kapitsa and Blackett's seminars.

Recently, Kapitsa was preparing for a single-photon experiment and invited Li Yu to come over for some guidance.

Li Yuke couldn't guide the experiment and could only give a supporting performance.

Kapitsa said happily: "Professor Rutherford approved the experimental funds for me!"

Blackett on the side said: "And let me be your assistant!"

Kapitsa laughed and said, "Don't act so unhappy!"

Rutherford had no son, and to some extent, sometimes he even treated Kapitsa as his own son and was very kind to him.

"Have you seen Dirac recently?" Li Yu asked.

"Of course I did," Kapitsa said, "but don't expect to hear another word from him now."

Blackett said: "The Department of Mathematics and Physics at Cambridge now has a new mathematical unit. If you say one word per hour on average, it is called 'one Dirac'."

Li Yu didn't know whether to laugh or cry. It turned out that the measurement units such as "one Kun" created by students in the 21st century had historical origins!
Be literate!
Li Yu said: "In Cambridge, being frugal with words has become a synonym for Dirac."

Kapitsa took a notebook from Blackett and said, "Don't worry, I won't ask you to do too much work."

Blackett seemed to be still in fear: "I don't know how the hospital will deal with Oppenheimer."

"Oppenheimer?" Li Yu asked, "What happened?"

Blackett said: "A few days ago, I arranged for Oppenheimer to continue some laboratory work. He suddenly put an apple on my desk. I felt a little strange because he had never done this before. Later, I accidentally discovered that the apple was smeared with several chemicals."

"..."

Oppenheimer was indeed a little depressed at this time. After being assigned to do experimental work that he disliked many times, he somehow did this neurotically.

The consequences are very serious. According to regulations, the minimum penalty is dismissal.

After leaving the laboratory, Li Yu went straight to the hospital office.

Oppenheimer's parents are lobbying Thomson: "We are willing to give ten times the financial compensation. In addition, Mr. Dean, you should know that if he is indeed diagnosed with mental problems, the hospital will still be held responsible if it still fires him."

Thomson was very conflicted. He had brought Oppenheimer here, and if he fired him, he would lose face. After hesitating for a long time, he said, "He can stay on campus, but the prerequisite is that he must go to London once a week to receive treatment from a psychiatrist."

Oppenheimer's parents naturally had no objection to this.

After the two left, Li Yu suggested to Thomson: "Mr. Dean, maybe we should transfer him out of the laboratory. Even I can see that Oppenheimer is not cut out for experiments."

Thomson just wanted him to stay away from the dangerous agents in the laboratory: "I agree, let him switch to theoretical physics and be with Dirac!"

Fortunately, Master Di won’t care.

And Oppenheimer's evaluation of Dirac was quite high, which is suitable for many geniuses:

"Dirac was not a person who was easily understood, and he did not care whether he was understood or not. I think he was definitely too strong inside."

By the way, the psychiatrists in London finally determined that Oppenheimer had a mental illness and made a very magical diagnosis: "precocious dementia"!
Yes, you read that right, this was the serious diagnosis made by psychiatrists at the time.

Moreover, the psychiatrists believed that Oppenheimer was beyond help and that psychoanalysis would do more harm than good...

In this day and age, once diagnosed with a mental illness, it seems that it is really impossible to prove that you are not ill.

-

Two days later, Li Yu met Dirac during morning exercise, and his pace was still very fast.

Li Yu stopped him and asked, "How is your paper going?"

"I am stepping up my research. The mathematics and physics involved in this paper are too profound," Dirac became interested when talking about professional matters. It was probably because there were not many people studying quantum theory in Cambridge. He continued to say to Li Yu, "Not satisfying the commutative law of multiplication seems to be the most wonderful thing."

Li Yu said: "It is indeed wonderful. I once heard a pastor say that there was a smoker who often had a craving for cigarettes, even when he was praying. So he asked the pastor if he could smoke while praying. The pastor told him, no! But if you pray while smoking, there is definitely no problem."

Dirac was amused: "What a wonderful metaphor."

Li Yu said: "In the same way, if a female student attends classes during the day and goes to a nightclub to hostesses at night, everyone will definitely think it is not okay; but if it is a nightclub hostess who insists on attending classes during the day, it is really inspiring. So sometimes order is really important."

"No wonder people like your class more and more," said Dirac.

"I wouldn't dare say that in class." Li Yu said with a smile.

Dirac said: "I have heard Kapitsa and Blackett talk less about politics recently. It seems that everyone has something to do."

Li Yu said: "I guess there is nothing left to talk about politically."

"It seems so," Dirac said. "The only thing that everyone is happy about is that the peace will continue after the signing of the Locarno Treaty, so the school has been closed for three days."

At this time, most European countries believed that war would not happen again, because they seemed to have reached a consensus: war was no longer a means of resolving disputes.

Well, that sounds fake.

The Locarno Treaty was a non-aggression treaty signed between France, Germany and Belgium, and was also guaranteed by the powerful countries Italy and Britain.

Italy is a strong country!
It was not easy to listen to Dirac talk so much, so he said goodbye and continued to go to the library.

During this period, Li Yu also talked with several great scholars such as Bohr and Einstein on the phone to discuss their views on the papers of Heisenberg and de Broglie.

Einstein was looking forward to Heisenberg's paper. In his reply to Li Yu, he said: "Heisenberg has sown a big quantum seed!"

Li Yu smiled in his heart and said: When this seed grows up, God of Love, you won’t be so expectant!

After nearly a week of hard work, Dirac produced his first paper with an ambitious title: "The Fundamental Equations of Quantum Mechanics".

Ordinary papers do not dare to use the term "basic equation" casually, not to mention that the adjective is directly "quantum mechanics".

In this paper, Dirac calculated what PQ-QP is equal to.

After reading it, Li Yu, even though he knew the result, still suggested: "It's better to send it to Heisenberg himself to have a look."

Dirac also felt it was necessary.

Correspondence with Germany was rapid, and before long Dirac received an enthusiastic reply from Heisenberg.

In the letter, Heisenberg was very happy about Dirac's in-depth discussion of his paper, but the following content made Dirac feel depressed: "In fact, someone here has discovered part of your work earlier. I hope you will not be bothered by this fact." Jordan, the student commissioned by Born, had already obtained the mathematical results of PQ-QP, but did not know the physical meaning yet.

This achievement was two months faster than Dirac's.

In other words, Dirac's paper might not be published.

Dirac was somewhat disappointed, but fortunately he was just trying out the technique. After the valve was opened, there were continuous results.

-

Denmark, Copenhagen.

Heisenberg was walking with Bohr as a visiting scholar, a habit that the two had maintained for decades.

The relationship between Heisenberg and Bohr is somewhat similar to that between Rutherford and Kapitsa. They were both teachers and friends, and as close as father and son. Moreover, they were both in different hostile camps afterwards, which was quite dramatic.

The two's last walk is a very famous unsolved case in the history of physics.

In 1941, Germany had occupied Denmark, and Heisenberg came to Copenhagen to visit Bohr.

At that time, Heisenberg was the leader of the German Uranium Club and helped Little Mustache research the atomic bomb.

The atomic bomb is quite complicated to talk about. If we sort out some core contents, it is nuclear fission: use a thermal neutron to bombard uranium 235, and the uranium 235 will fission into two smaller nuclei + neutrons + energy; the neutrons produced by fission continue to bombard other uranium 235, forming a chain reaction.

In order to ensure that a fission reaction can occur, the amount of uranium 235 cannot be too small, that is, there must be a critical mass.

This number is critical.

Most uranium ore in nature is uranium 238, and only 0.7% is the key uranium 235. Refining uranium 235 can be said to be the most basic step in making an atomic bomb. The process is very troublesome and consumes a lot of energy.

The critical mass was first calculated by Otto Frisch and Rudolf Peiers, two scientists who fled from Germany to England, and was approximately 5kg.

This result was quickly told to the United States in a top-secret manner.

To be honest, 5kg is not a small number, it is just acceptable. After Oppenheimer launched the Manhattan Project, the uranium 235 refining plant in Oak Ridge, Tennessee and the plutonium manufacturing plant in Hanford, Washington, DC each used more water and electricity than an entire city, and even used 6000 tons of silver.

As for Heisenberg, the critical mass he calculated was several tons! Such a huge number was simply impossible to achieve, so Germany gave up the atomic bomb project.

In 1941, Germany was unstoppable on the battlefield. Half of Europe was occupied by Germany, and the war on the Soviet-German front was extremely successful.

This resulted in the identities of Heisenberg and Bohr becoming very special: Heisenberg was the scientific leader of sodium embrittlement, while Bohr, who was in occupied Denmark, opposed sodium embrittlement from beginning to end.

In the past, the teacher and student had a relationship like that of father and son, but this meeting was different from the past.

Copenhagen was very resistant to Heisenberg's arrival, so he stayed for less than a day. But out of their long-term friendship, Bohr still had three conversations with him.

The second time, the two talked about the uranium project.

The most mysterious is the third private conversation that Bohr invited Heisenberg to have, which was also the last walk recorded in the history of science.

As for what the two of them talked about, no one knows.

Bohr later wrote several letters to Heisenberg, but they were not sent out until 2002, when they were declassified. The letters still did not mention the content of the last walk.

Both of them took this secret to their graves.

The only thing that is certain is that when Heisenberg told Bohr during their walk that he had calculated the approximate mass to be several tons, Bohr's expression changed drastically and he became very excited. He quickly ended the conversation and the two went their separate ways from then on.

People in later generations made many speculations, but they were just speculations.

There is a story circulating on the Internet that says Heisenberg deliberately miscalculated the critical mass, but it is actually a rumor.

This story originally came from one of Heisenberg's students, who wanted to protect Heisenberg's reputation.

After the successful explosions of the atomic bombs in Hiroshima and Nagasaki, German scientists such as Heisenberg, who had been imprisoned by the Allies, were shocked when they received the news and thought it was impossible.

Heisenberg's student used this to make up a story that Heisenberg deliberately made a mistake in his calculations.

In addition, Bohr did not know the value of the adjacent mass in 1941, so it was impossible for him to ask Heisenberg to deliberately make a mistake in calculation.

However, it is precisely because of the suspense of this story that people are more interested in the conversation between Bohr and Heisenberg. Unfortunately, we will never know.

Let’s get back to this moment.

Heisenberg said to Bohr while walking, "Sir, Professor Born and Jordan have completed the second paper on matrix mechanics. They wrote to ask me to go back to Göttingen."

Bohr could guess the importance of this work: "I heard that a graduate student in Cambridge also independently obtained very accurate results."

Heisenberg said: "So Professor Born thinks we need to speed up our research and make sure we get ahead of Cambridge."

Heisenberg was quite confident about this. After all, Dirac was alone, while he could get help from Born and Jordan in Göttingen:

Heisenberg's first paper is generally known as "A Man's Article";
After Born and Jordan solved the matrix problem and calculated PQ-QP, they also published a paper called "Two People's Article";
Heisenberg returned to Göttingen, and the three of them collaborated on research again, publishing a new paper called "Three People's Article."

Born's greatest contribution was in the field of matrix mechanics.

Born and Jordan were excellent in mathematics, and Heisenberg was impeccable in physics, so the collaboration between the three was extremely effective.

Although Dirac was very strong, he was just reading other people's papers and then continuing his research, so he was not as fast as the three of them.

But Dirac had his own advantages. He had a good mathematical foundation and physical intuition. He was not restricted by academic exchanges and could solve many problems on his own.

In addition, Heisenberg and Dirac had some different ideas about quantum mechanics. Dirac believed that quantum mechanics was an extension of classical theory, while Heisenberg believed it was revolutionary.

Heisenberg's papers all used existing experimental results; while Dirac focused more on the theory itself, especially mathematics, and then used theory to speculate what experimental results would occur.

Heisenberg had been traveling back and forth between Göttingen and Copenhagen for the past two years, and Bohr had gotten used to it, so he said, "Don't forget to visit Pauli before you leave Copenhagen."

Heisenberg definitely had to go and see this older brother from his days at the University of Munich.

Pauli was working on Bohr's theory in the library, but it wasn't going well and he kept running into obstacles, probably because he didn't have hay fever and was on vacation.

Heisenberg asked, “Have you read the recent papers?”

"Of course I have," Pauli said. "I feel that physics is all wrong again at the moment. It's just too difficult for me anyway. I wish I were a comedian or something like that and had never heard of physics!"

Heisenberg laughed and said, "If you say that, then I'd like to invite you to watch a Charlie Chaplin movie."

Pauli threw the book away and said, "I have studied this more deeply than you!"