September 29, 2021 marks the 120th anniversary of Fermi's birth. Fermi was one of the masters of physics of the 20th century and made significant contributions to both theoretical and experimental physics. In Yang Zhenning's eyes, Fermi is also unique in terms of personality - he is always down-to-earth, does not abuse influence, and is a standard Confucian gentleman. This article was written on the occasion of the 100th anniversary of Fermi's birth in 2001. This year marks the 120th anniversary of Fermi's birth, and we honor the memory of this great physicist.
Written by | Yang Zhenning
Force can harm and disdain,
The most obvious can do not do;
Can move others like stones,
Firm and calm;
If he allows it to be blessed,
Natural abundance does not wave;
As after the beauty of the other,
Others are consumed as beautiful labor. [1]
Enrico Fermi was one of the most revered and admired of all the great physicists of the 20th century. He is revered and admired because of his contributions in both theoretical and experimental physics, because the work under his leadership has discovered powerful new sources of energy for mankind, and more importantly because of his personality: he is always reliable and trustworthy; he is always down-to-earth. He is extremely capable, but he does not abuse influence, nor does he sensationalize or demean people. I always thought he was a standard Confucian gentleman.
Fermi's earliest interest in physics seems to have been in the field of general relativity. Around 1923 he began to delve into the "Gibbs paradox" and "absolute entropy constant" in statistical mechanics. Then, as E. Segrè wrote:
When he read Pauli's article on the principle of incompatibility, he immediately realized that he had mastered all the elements of the ideal gas theory. This theory satisfies the Nernst theorem at absolute temperature zero, providing the correct Sackur-Tetrode formula for absolute entropy at low densities and high temperature limits. This theory has no arbitrary assumptions of all kinds that had to be introduced in previous statistical mechanics to find correct entropy values. [2]
This study derived Fermi's first monumental work, deriving concepts such as "Fermi distribution", "Fermi sphere", "Fermi liquid", "Fermion" and so on.
According to the characteristics of Fermi's research style, after making contributions to this theory, he then applied this theory to the structure of heavy atoms and derived the Thomas-Fermi method, which is now commonly known as the Thomas-Fermi method. For the differential equations in this method:
Fermi used a small, primitive slide rule to find its numerical solution. The calculation may have taken him a week. Majorana (E. Majorana) is a person who calculates extremely quickly and does not trust people's words. He decided to verify Fermi's results. He converted the equation to the Riccati equation and solved it numerically. The result is exactly the same as what Fermi got. [3]
Fermi likes to use calculators. He loves to use both small and large calculators. Those of us in Chicago saw this trait and were convinced. Apparently early in his career, he had fallen in love with calculators. This hobby continued into his later years.
Fermi's next major contribution was in quantum electrodynamics, where he successfully ruled out longitudinal fields, resulting in the Coulomb interaction. Students in Chicago between 1946 and 1954 knew he was extremely proud of his work (but today few theoretical physicists under the age of 65 seem to know about Fermi's contribution). This work, again, was very Fermi's style: he saw through the complex formal field theory, saw its basic inclusion, the set of harmonic oscillators, and then turned the problem into a simple Schrödinger equation. This work was first presented in Paris in April 1929 and again in the summer of 1930 at the famous summer seminar in Ann Arbor. In the late 1950s, G. Ullenbeck Uhlenbeck once told me that before Fermi's work, no one really understood quantum electrodynamics. This work made Fermi one of the few top field physicists in the world.
Now I'll skip Fermi's brilliant work in ultrafine structure theory in 1920 to talk about his β decay theory. According to Segerre, Fermi considered this theory to be his most important contribution to theoretical physics throughout his life. I've read Segerer's comments on this, but I'm confused. One day in the 1970s, I was with E. Wigner. Wigner) had the following conversation in the Rockefeller University cafe.
Yang Zhenning: What do you think is Fermi's most important contribution to theoretical physics?
Wigner: Β decay theory.
Yang Zhenning: How could it be? It has been replaced by more basic concepts. Of course, his β decay theory is an important contribution, and it has dominated the entire field for more than forty years. It put aside the parts that could not be understood at that time and focused on the parts that could be calculated at that time. The results are wonderful and in line with the results of the experiment. But it is not eternal. Rather, the Fermi distribution is eternal.
Wigner: Otherwise, otherwise, you don't understand its impact at the time. John von Neumann and I and others have been talking about β decay for a long time, and we just don't know how an electron can come out of the nucleus.
Yang Zhenning: Didn't Fermi know how to do it after using quadratic quantization?
Wigner: Yes.
Yang Zhenning: But you and P. Jordan Jordan) was the first to invent quadratic quantized Ψ.
Wigner: Yes, yes, but we never imagined that it could be used in the physical theory of reality.
I do not intend to continue to speak of Fermi's subsequent contributions, nor of his relationship with his students. The latter, I've written about before. [4] I will tell only two stories about Fermi.
Joan Hinton (Han Chun) was one of Fermi's assistants at Los Alamos during World War II, after which he became a graduate student at the University of Chicago. When I started working for Samuel King Allison in late 1946, she was also a graduate student in the lab. In the spring of 1948 she went to China, married her boyfriend Sid Engst (Yang Zhao), and settled in China to work in agriculture (her experience is an interesting story that should be written down). I hope she can do this soon). In the summer of 1971, I visited New China for the first time, half a year before Nixon's visit to China. I met her by chance at a guest house in Dazhai, Xiyang County. Dazhai was a model example of an agricultural commune at that time. We were, of course, amazed and delighted, and reminisced together about those days in Chicago: how clumsy I was in the lab; how I inadvertently nearly subjected her to a fatal electric shock; how I taught her a few Chinese; how I borrowed a car to drive her to La Salle station and begin her long journey to China, and so on. She asked me if I remembered the farewell party that the Fermis had for her before she left, and I remembered it. She asked me again if I remember the camera they gave her that night, and I don't remember. Then she said that a few days before the farewell party, she felt she should tell Fermi that she planned to go to the Chinese Communist Party-controlled areas. After thinking about it for a few days she finally told Fermi. What does Fermi say? "He didn't object, and I'm forever grateful for that." I knew the weight of her words,[5] and immediately after returning to Stony Brook I called Mrs. Fermi in Chicago and told her about the whole process of my meeting Joan in Dazhai. A few years later, Joan herself traveled to Chicago and had the opportunity to visit Mrs. Fermi and her daughter, Nella Femi.
I would like to conclude with a passage from page 48 of my Anthology (1983).
Whether as a physicist or as a human being, Fermi is revered by all men, and I believe that he is awe-inspiring because he is a solid man. All his performances exude the charm of his character. In the early 1950s, J. Oppenheimer, chairman of the U.S. Atomic Energy Commission's most important advisory board, was a member of the U.S. Atomic Energy Commission. R. Oppenheimer told me that he had tried to persuade Fermi to remain on the advisory board after his term expired. Fermi was reluctant. Oppenheimer insisted. Finally Fermi said: "You know I don't believe that my own views on these political issues are always correct. ”
It is often said that Fermi (1901-1954) was unique among all 20th-century physicists, making first-rate contributions both theoretically and experimentally. I would like to point out that on the other hand he is also unique: he has never consciously or unconsciously tried to inflate his prestige and influence beyond the confines of reality or his true self. To emphasize this, I chose eight of Shakespeare's 94th sonnets to introduce Fermi. Unfortunately, when the above article was published in 2004 in Fermi's Memoirs, the last line was left out by the typesetters. In contrast, Oppenheimer (1904-1967) and Tehler (E. Teller) Teller, 1908-2003) both enjoyed and sought power and influence. I believe this is the main reason for the conflict between them, and the tragic lives that are very different from them.
When I wrote about Fermi in the above article, I said:
He was always down to earth. He is extremely capable, but he does not abuse influence, nor does he sensationalize or demean people. I always thought he was a standard Confucian gentleman.
I think such a character is rare in america today. American society seems to be pushing its illustrious people in the opposite direction. Oppenheimer, Teller, R. Finnmann P. Feynman), T. Kuhn Kuhn) has its own set of ways to please the audience and flaunt itself.
Science in the United States is advancing by leaps and bounds, and successful American scientists are often extremely aggressive and sharp. Are these two things related?
But I know that the model of Chinese Confucianism, even today, is very dynamic. Zhou Guangzhao, former president of the Chinese Academy of Sciences, as an ordinary person and physicist, I wrote the following paragraph:
Zhou Guangzhao is a top physicist. He has a broad vision, is far-reaching, and is quick to see new ideas. His style of doing physics reminds me of Lev Davidovich Landau, Mohammad Abdus Salam and Teller. But from my personal perspective, Zhou Guangzhao was a perfect practitioner of Confucianism, not as aggressive as many famous physicists in the United States, Europe, and Russia.
[This article was written in 2001 to commemorate the 100th anniversary of Fermi's birth, and was included in the Shuguang Collection (by Yang Zhenning, compiled by Weng Fan, Sanlian Bookstore, 2008 edition).] In 2013, when the English version of Selected PapersII., with Commentary (World Scientific Publishing, 2013) was re-included, the author added an afterword and submitted it to this journal for publication, and the afterword was translated by Yang Jianye into Chinese. When the journal was published, a small amount of word processing was done according to the style of this journal, and it was approved by the author. ]
This article was published in Science Magazine, Issue 4, 2013
exegesis
[1] See: Sonnets of Shakespeare, 94.
[2] 参见：Segrè E. Collected papers of Enrico Fermi. Chicago: Univ of Chicago Pre, 1962：178.
[3] 参见：Rasetti E. Collected papers of Enrico Fermi. Chicago: Univ of Chicago Press, 1962: 277.
[4] 参见：Yang C N. Collected papers of Enrico Fermi. Chicago: Univ of Press, 1962: 673.
[5] Hanchun was in China in 1948, when the Chinese Communist Party had not yet defeated Chiang Kai-shek and the Korean War broke out two years later. If she wanted to go to China after the outbreak of the Korean War, I am sure the U.S. government would not allow her to leave the United States.