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I am very sad about the passing of Tsung-Dao Lee. As an old friend, I can't help but recall some of the past times when I interacted with him...

The first time I heard the name of the famous physicist Professor Tsung-Dao Lee was one morning in the 1950s. That morning, the then head of the International Department of Xinhua News Agency came excitedly with a telegram from a foreign news agency and asked the duty director to review and publish the news that Tsung-Dao Lee and Chen-Ning Yang had won the Nobel Prize in Physics.

The president on duty was reading the manuscript while discussing with the head of the International Department what "parity conservation" and "parity non-conservation" meant. The news that Professors Tsung-Dao Lee and Chen-Ning Yang overturned the law of parity conservation on the other side of the ocean and won the Nobel Prize in Physics spread throughout China after being broadcast by Xinhua News Agency.

Afterwards, with a feeling of admiration and curiosity, I repeatedly read this telegram published by Xinhua News Agency on February 23, 1957:

Chinese physicists studying in the United States, Tsung-Dao Lee and Chen-Ning Yang, discovered a major problem in nuclear physics.

In the summer of 1956, when conducting theoretical research on atomic nuclei and elementary particles, Chinese professors Tsung-Dao Lee of Columbia University and Chen-Ning Yang of Princeton Institute proposed a new concept: the "Law of Conservation of Parity", which has been considered a basic physical law of the microscopic world for more than 30 years, is not applicable under weak interactions between atomic nuclei and elementary particles and between elementary particles. This law is only correct under strong interactions and electromagnetic interactions. It was wrong to regard it as a universal law and to extend its application to weak interactions.

“Who are Tsung-Dao Lee and Chen-Ning Yang? How did they accomplish this great achievement? Is there any chance for them to talk about their path to success, their joys and sorrows, their pursuits, and their life experiences?”

Since I heard their names and their outstanding contributions to science, I couldn't help but have the above idea. However, the ocean is vast and the years are long. My wish to meet the great scientists was fulfilled 22 years later when I entered the science and technology community as a reporter to interview.

Lead by example

It was a day in the spring of 1979. When I was interviewing at the Graduate School of the Chinese Academy of Sciences, the director of the institute, Wu Tang, said to me: The famous physicist Tsung-Dao Lee's just started lecture at the Beijing Science Hall has received a warm response both inside and outside the Graduate School, and Lee has made careful preparations for this lecture.

"You've come at the right time. Can you interview Mr. Li and write a report?" Wu Tang asked me.

After returning to the editorial office, I reported the above situation to the relevant responsible comrades and said that I was going to spend some time to interview at the Beijing Science Hall and write about the grand occasion of Li Zhengdao's lecture. After the editorial office agreed, I went to the Beijing Science Hall every day to listen to Li Zhengdao's lectures. During the breaks, I talked with the scientists and professors who attended the lectures. Through watching and listening, I interviewed a lot about Professor Li Zhengdao. For 7 weeks, the lecture hall of the Beijing Science Hall was full every day. Many people simply sat on the floor close to the podium. People in the back seats held telescopes while listening and watching the handouts projected on the wall by the projector. In the basement of the lecture hall and the Graduate School of the University of Science and Technology of China, people gathered around a broadcast TV and listened carefully. Among the audience were Li Zhengdao's early teachers, classmates, and good friends, as well as a new generation of young physicists trained after the founding of New China. During the interview, the audience's evaluation of Professor Li Zhengdao's lectures was: profound knowledge, scientific methods, rigorous scholarship, and tireless teaching.

“As a professor, he is very connected to his students. He is always concerned about the level of understanding of his students.”

During the interview, everyone believed that it was no accident that Professor Tsung-Dao Lee's lectures won unanimous praise. He lectured for three hours every day, but it took him five or six hours to prepare for the class. Sometimes he was too tired to lecture, so he would rest his head on the pointer with his hand. Sometimes he was sweating profusely and simply took off his coat and continued to lecture. For three hours, he talked about the history of the development of strong and weak interactions, the past, present and future of particle physics. The audience inside and outside the classroom were fascinated and entered the mysterious world of particles.

During the interview, someone told me that Tsung-Dao Lee only lectured 28-30 hours a year on average abroad, and these two courses usually took two to three years to teach. This time, he felt that China urgently needed scientific and technological talents to achieve modernization, so he decided to finish several years of courses in two months. In order to do a good job of this lecture, he started preparing for it a year ago and sent a large number of documents and books to his Chinese colleagues.

When the peripheral interviews were almost done, I decided to interview Tsung-Dao Lee directly. Unexpectedly, he arranged the interview during the short break between classes. That day, Tsung-Dao Lee looked very tired. He kept stuffing lozenges into his mouth while answering my questions in a hoarse voice. In just 20 minutes, he talked about how he left China for the United States in 1946 and studied under the famous physicist Fermi at the University of Chicago. He also talked about his cooperation with Professor Chen-Ning Yang and how he discovered the "Law of Parity Non-Conservation".

At the same time, I also accompanied Tsung-Dao Lee to visit the Graduate School of the University of Science and Technology of China and the Junior Class of the University of Science and Technology of China, and learned about his concern for China's training of scientific and technological talents. On May 17, 1979, Xinhua News Agency broadcast the report I wrote entitled "Professor Tsung-Dao Lee on the Chinese Lecture Platform". Afterwards, Chinese newspapers in mainland China, Hong Kong, Macao and all over the world published it in a prominent position.

CUSPEA Trees become forests

Since the 1970s, I have participated in many activities of Professor Tsung-Dao Lee during his visits to China. I have also recorded and reported on his academic activities such as his lectures, training of graduate students for China, active advocacy and assistance in establishing a postdoctoral system in China, and helping China build the Beijing Electron-Positron Collider in the form of news, correspondence and reportage.

During these activities, I was deeply impressed by Professor Tsung-Dao Lee's deep affection for his motherland.

Year after year, although Tsung-Dao Lee was far away overseas, he never forgot that his roots were deeply rooted in our ancient land.

After returning to China in 1979, he was very happy to hear that the University of Science and Technology of China had established a junior class. On April 20 of that year, he gave up his weekend and made a special trip from Beijing to Hefei, Anhui, to visit the children in the junior class.

While engaging in scientific research and teaching, over the years, Tsung-Dao Lee has also insisted on doing two things for China: one is to help China develop high-energy physics and synchrotron radiation, and the other is to train scientific and technological talents for China.

He said: "As long as we can cultivate high-level talents for China, it is worth it for me to sacrifice some time and even do some work like 'sending and receiving liaisons'."

When he was lecturing in Beijing in 1979, he came up with the idea of ​​a joint China-US Physics Examination and Application (CUSPEA) program for training physics graduate students.

He said to the person in charge of the relevant Chinese department: "Why not send formal graduate students? This way, the students can get degrees. If you agree to send graduate students, I can help mobilize all the top private universities in the United States to accept Chinese students, fund and train them."

After returning to the United States, he was still concerned about this matter. Although he had been teaching and doing scientific research in the United States for more than 30 years, he had never done administrative work such as admissions. One day, he invited Professor Sachz, the head of the Department of Physics at Columbia University, to ask him, "Please tell me about the admissions procedures of American universities."

After listening to the introduction, Li Zhengdao said: "Oh, so complicated! I have been teaching in the United States for 30 years, and I didn't expect the admissions procedures to be so complicated!" After thinking for a while, he took a piece of paper, drew a grid, and wrote in English: "Let's do this. Today I will create a new admissions method for Chinese physics students. There is no need to take the GRE or TOEFL test, and there is no need to apply to the admissions office first. The name of this method is called CUSPEA!"

After that, Tsung-Dao Lee spent a year and a half working day and night, paying for postage and phone calls, to contact the physics departments of American universities, hoping that they would accept and train scientific and technological personnel for China. The relevant domestic departments had repeatedly offered to pay for him, but Professor Tsung-Dao Lee firmly refused. He said, "This is a little gift from me. It is meaningful to train talents for China!" The Sino-US joint training program for physics graduate students went smoothly. After completing all the formalities, he personally sent a letter full of eager expectations from New York to his classmates who were preparing for the exam. In the letter, he wrote in neat Chinese:

Dear students,

Thanks to the strong support from the Chinese Academy of Sciences, the Ministry of Education, the leaders and professors of various universities and research institutes, CUSPEA's preliminary work has achieved very good results. Of course, the most important thing is your own efforts.

After coming to the United States, please do not immediately decide on a major. In addition to your own interests, please also consider your future use and the needs of the country. Generally speaking, you should do more experiments than study theory. Asking you to enter the graduate school is just the beginning of learning, and getting a doctorate is just the beginning of employment. Your test results this time fully demonstrate that China's colleges and universities have a very good level. In the future, when you return to China after completing your studies, you can improve the quality of universities and research institutes more quickly, so that they surpass the world's scientific foundation, and industry and agriculture can also develop accordingly.

Wish you

bright future!

Tsung-Dao Lee

December 13, 1980

Why is Tsung-Dao Lee so enthusiastic about cultivating talents for China?

On May 25, 1985, at a gathering with Chinese graduate students in New York, he said:

Today we have every reason to believe that Chinese scientists will be the main figures in the future. Therefore, you must shoulder this historical responsibility together and share common goals and ideals. This is also one of the main reasons why we are gathered here today.

The future of Chinese science is the future of world science. Helping each other is helping ourselves and your entire generation. Your destiny is in your own hands. The final success depends on the collective efforts of your generation.

During my interview with Professor Tsung-Dao Lee, I deeply felt that although he was on the other side of the ocean, his heart was always concerned about China's affairs in order to train scientific and technological talents for China and for the development and progress of China's scientific undertakings.

One day in May 1984, Tsung-Dao Lee met me. After several years of getting to know me, he was no longer as "wary" of journalists as he had been before. He talked to me candidly like an old friend. During this wide-ranging conversation, he introduced me to the situation of graduate students studying in the United States.

He said: "The Sino-US joint training program for physics graduate students is going very smoothly. At the beginning, I promised to hold six classes, with a total of about 700 people. Now, the enrollment scale has been held for four classes in China, and there have been three classes in the United States, with a total of 362 people. Among the 285 people who have selected majors, 231 are engaged in research with major application prospects such as new materials, lasers, plasma physics, atmospheric physics, biophysics, medical physics, nuclear physics, semiconductors, and magnetism. The majors selected by the remaining graduate students are all related to the future development of science and technology."

"What do American scientists and professors think of the level of these Chinese graduate students?" I asked Tsung-Dao Lee.

A gratified smile immediately appeared on his face: "The work of training graduate students is progressing smoothly, mainly due to the excellence of Chinese youth."

"In the past, there were no Chinese graduate students in the physics departments of many first-class universities in the United States. This was because the schools did not understand or trust the level of Chinese students. The performance of Chinese graduate students recruited in the United States in recent years shows that: first, Chinese youth are excellent; second, the fact that so many high-level students can be trained proves that the level of Chinese universities is world-class. Now, American universities have no doubts about the excellence of Chinese students and have established trust." Li Zhengdao said with a smile while gesturing. He compared these young people who will get doctoral degrees to seedlings. But he believes that it will take more effort to make these "seedlings" successful.

At this point, Tsung-Dao Lee smiled and said to me, "I have suggested to the relevant Chinese authorities to set up a 'postdoctoral' mobile station. We will select research institutes and universities with excellent conditions to set up 'mobile stations' across the country. Each station will have a fixed number of personnel. The station members are all young people who have just obtained their doctoral degrees. They can move between several different (including domestic and foreign) units for 2-6 years, so that they can come into contact with scholars and work in various fields in different environments to broaden their horizons, increase their knowledge and experience. Then, through international competition, they can obtain relatively fixed positions. Only talents who have passed such rigorous tests can become the leaders of the new generation of science and technology."

Xiaoyang Radiation Science

In the spring of 1988, Tsung-Dao Lee returned from his travels. On May 26, I interviewed Tsung-Dao Lee again in a room next to the experimental hall of the Beijing Electron-Positron Collider, which was about to be built at the Institute of High Energy Physics of the Chinese Academy of Sciences in the western suburbs of Beijing.

Tsung-Dao Lee, wearing a blue shirt, showed me a painting with great interest. In the painting, a shepherd boy sat on the ground, concentrating on gazing at the radiant nebula in the distant sky. It turned out that this painting was created by Mr. Li Keran, a famous Chinese painting master, at the request of Tsung-Dao Lee, specifically for the International Symposium on Synchrotron Radiation Applications. As I was admiring the painting and praising it, Tsung-Dao Lee said to me: "China is an agricultural country, and the shepherd boy represents today's young scientists." He pointed to the two lines of words on the painting and said to me with a smile: "Please read them, I wrote two lines of poetry."

"The shepherd boy looks into the distance in pursuit of knowledge, and the dawn radiates the light of science." After I finished reading this, everyone present laughed happily.

Tsung-Dao Lee said: "Artists also place great hopes on young Chinese scientists. Science and art are equally important. For the development of China's synchrotron radiation science, Mr. Li Keran made a special painting in his busy schedule to express his thoughts. This is very commendable. We have hung this painting on the left side of the rostrum of tonight's reception. The glowing nebula in the picture is likely to be a supernova discovered in the Northern Song Dynasty, or it may be synchrotron radiation in the future. Mr. Wu Zuoren also created a very wonderful painting for another discussion on two-dimensional space physics, which will be hung on the right side of the rostrum tonight. His painting cleverly borrowed the concept of the ancient Chinese Tai Chi diagram and used art to express the theme of the discussion. It is full of highly scientific and dynamic artistic conception, which is especially appropriate for high-temperature superconductivity. I also wrote two sentences for his painting - the ancient Tai Chi style takes on a new form, and the two-dimensional Yin and Yang solves superconductivity." Everyone laughed again after hearing this.

Li Zhengdao also told me that: "Mr. Huang Zhou also painted to celebrate a similar 'particle and cosmology' work discussion meeting to be held in Nanjing in August this year. His paintings will be exhibited at the meeting in August. His paintings are magnificent and imaginative, fully demonstrating the future of scientists in the motherland. After the meeting, these three paintings will be hung in the building of the China Advanced Science and Technology Center, which is about to be completed, as a permanent memorial."

After that, I was invited to attend the international academic conference held by the China Center for Advanced Science and Technology. The center is headed by Tsung-Dao Lee. Every year, it selects several cutting-edge topics in world science and invites 10 first-class experts and scholars to come to China to introduce the progress, difficulties and development prospects of their respective fields at the conference. They also live and work with 90 Chinese scholars for a period of time, so that Chinese experts and scholars can quickly stand at the forefront of the research field and carry out more world-class work. The activities of this year are: international seminars on synchrotron radiation applications and two-dimensional strongly correlated electron systems.

In the middle of the meeting, Tsung-Dao Lee said excitedly: "The two-week international symposium on synchrotron radiation applications that starts today is different from ordinary international conferences. This conference is held to improve the level and academic status of Chinese scientists in the field of cutting-edge science and to provide young scientists with good learning opportunities."

"What is synchrotron radiation?" I asked.

After thinking for a while, Tsung-Dao Lee introduced that Professor Winick showed a slide of the Crab Nebula at the meeting today. Did you see it? As early as the Northern Song Dynasty in China, there were records of supernovas, namely the Crab Nebula. Astronomers in the Northern Song Dynasty recorded its brightness every day. According to records, a strange star as big as a chicken egg suddenly appeared in the sky in the first few days, and then its brightness gradually weakened. A month later, it was still as bright as Venus and shone for more than 300 days. This is the most complete record of supernovas in the world. The light emitted by supernovas is synchrotron radiation. At present, the synchrotron radiation light produced by electron synchrotron accelerators has a very broad application prospect. It is called "tomorrow's laser" in the world. It can be said that it has a wider range of uses than lasers. Due to its advantages such as high intensity and good collimation, it is an extremely powerful research tool in the research of condensed matter physics, medicine, biology, materials science and other disciplines.

Li Zhengdao said that this conference brought together outstanding synchrotron radiation experts from all over the world. The purpose of holding this symposium is to invite experts from all over the world in this field to come together to publish academic papers and conduct discussions. It is also good to know what others do and then do it, otherwise you can only follow behind them forever. What is more important is to know what others have not done yet, so as to find the right direction to make a breakthrough. If you can do it, you can get ahead of others.

During this meeting, Tsung-Dao Lee spoke eloquently. He said enthusiastically that the construction of the Beijing Electron-Positron Collider also promoted the development of China's high technology. He also told me happily that now, China-made accelerator tubes have been exported to the United States. Last year, the Brookhaven National Laboratory in the United States bid for the purchase of two more accelerator tubes from countries around the world. In the end, the Institute of High Energy Physics of the Chinese Academy of Sciences won the bid. The goods have been delivered this year.

"This is the export of high-tech products. Because the finished product is of excellent quality, during this seminar, the Brookhaven National Laboratory in the United States expressed its intention to order eight more accelerator tubes from China. It is estimated that the contract can be signed in June, with a total sales price of US$2.07 million and a net profit of approximately US$600,000. This morning, the director of the Stanford Synchrotron Radiation Laboratory also told me that he wanted to order some main components of accelerators made in China. In Shanghai dialect, this is a 'head-on collision'. If the quality of the accelerator tubes made in China is not good, people will not buy your products!" said Tsung-Dao Lee with a smile.

Li Zhengdao also said: "The accelerator tubes made by the Chinese have reached the highest international level, attracting countries around the world to buy them, and more people will come to buy them in the future. It can be said that this has greatly increased the self-confidence and self-esteem of the Chinese people. In addition, due to the need to build the Beijing Electron-Positron Collider, many factories also assisted in the work, which improved China's high-tech industrial level. Other technical levels such as vacuum, power supply, and high-frequency have also been greatly improved. With the improvement of the national industrial level, we can compete with the world level and strive for a larger foreign market."

Before this meeting, Tsung-Dao Lee also talked about the progress of postdoctoral work in China. He told me: "In 1984, Deng Xiaoping discussed with us the relevant issues of the postdoctoral system. Deng Xiaoping asked: The title of doctor probably existed in the Han Dynasty. Obviously, the knowledge of a doctor is very "extensive", so why do we need a postdoctoral? I explained that in college, the teacher gave him a problem with a solution, and then the teacher guided him to solve the problem. The college student solved the problem given by the teacher according to the courses he learned in school. If the solution is consistent with the correct solution known by the teacher, the student can complete his college studies and get a bachelor's degree. In the graduate school, the teacher gives the students a problem, but the teacher does not know how to solve it. The graduate student solves the problem given by the teacher according to the knowledge he has learned, and the solution is judged by the teacher himself and his peers. If the solution is considered correct, he can graduate from the graduate school and get a doctorate. However, real research and real development requires one to set the problem by oneself and conduct research independently. This stage of cultivating independent work is the process of postdoctoral study, so there must be postdoctoral students."

Li Zhengdao said: "In 1987, there were more than 120 PhDs who returned from abroad, and less than half of them became postdoctoral fellows. Let's study this number of more than 120 who returned from abroad."

He said: "In foreign countries, the average time to study for a doctorate in a research institute is 6 years. Some students work as postdoctoral fellows for one or two years after obtaining their doctorate abroad. It can be seen that they studied abroad for 6-8 years. This year is 1988. These young scholars who have returned from abroad refer to those who were sent abroad from 1980 to 1982. In those two years, the main people sent out from China were visiting scholars, not students. Students were mainly sent out after 1982, so more than 120 people who returned from abroad are quite a lot, which means that most of the students who went abroad will come back. In recent years, our first batch of doctoral students (CUSPEA) in the Department of Physics at Columbia University have been admitted. The first batch admitted five Chinese students, and the second batch admitted three. Four of the eight have returned to China after completing their studies. China has sent tens of thousands of students abroad, and the vast majority went abroad after 1982. In a year or two, more young scholars will return to China, and we must be fully prepared for their arrangements. How can we actively create conditions in China to care for the PhDs who return to China, and value the PhDs trained in China and those who return from abroad equally; encourage the outstanding ones to go abroad for further studies after working in China for a few years; insist on open exchanges, unite foreign and domestic scholars, and work together. These tasks are very urgent and should be paid attention to. If we do these tasks well, we will attract more people to return to China. "

During the interview, Tsung-Dao Lee also told me that he was full of confidence in the future of young doctors: "Not only me, but many foreign scholars, including many of my friends, believe that in the next 10 to 20 years, the vast majority of the world's science and technology fields will be of Chinese descent. In the Department of Physics at Columbia University, the top four are almost every year Chinese students from my CUSPEA program. The same is true for other universities such as Harvard, Princeton, and Yale. Therefore, most of the leaders in science and technology in the next 10 to 20 years will be Chinese, there is no problem with that. Our competition is not only in the economy, but also in the development of science and technology. We not only need to catch up with others, but also to lead. To lead, we must have an elite team that is independent, creative, and capable of breakthroughs."

He predicted that today's postdoctoral talents will be the team of the future. By then, the situation in the world's science and technology field will be greatly changed.

(The author is a former senior reporter of Xinhua News Agency. Her reports on scientific masters such as Deng Jiaxian, Chen Jingrun, Hua Luogeng, Li Zhengdao, and Yang Zhenning have influenced several generations of Chinese people. To this day, middle school students can still read her writings about Deng Jiaxian and Hua Luogeng in Chinese textbooks. She has published books such as "Spring of Science" and "Face to Face with 20 Great Scientists".)