Stories of Tsinghua’s History: Chi-Sun Yeh and Tsung-Dao Lee’s Friendship

Dr. Chi-Sun Yeh (1898-1977) was a famous Chinese modern scientist, educator and one of the initiators of the Chinese modern scientific careers. He was hailed as “the cornerstone of Chinese modern scientific careers”. He entered Tsinghua School in 1911, obtained a PhD from Harvard University in 1923 then came back to China the following year. He has taught in Southeast University, Tsinghua University, Southwest Associated University and Peking University, participated in the cultivation projects in the Department of Physics and College of Science at Tsinghua University, Magnetics Special Group at Peking University and the Chinese Physical Society. More than 50 academicians were fostered including Chen-Ning Yang, Tsung-Dao Lee, Wang Ganchang, Zhao Jiuzhang, Qian Sanqiang, and Deng Jiaxian. More than half of the 23 “Two Bombs and One Satellite” winners were his students. This article recorded the story between Chi-Sun Yeh and Tsung-Dao Lee.

In Sep 1938, Dr. Chi-Sun Yeh arrived in Kunming, which was where the Southwest Associated University had settled, later he went to Chongqing for business. While going back to Southwest Associated University in July 1943, he lived in the quarters for the single professors at Beimen Street in Kunming. He was already 40 years old and seemed a little bit numb in the picture. No matter if he wore long gowns or suits, he always looked the same—sincere and upright. Students reflected that he stammered and the tone was unemotional consisting of a Shanghai accent which was hard to understand. In the journal 8 years at Southwest Associated University edited by New Year’s Eve Supplement, students said he couldn’t talk fluently but had a kind heart.

In 1945, when Dr. Chi-Sun Yeh was giving electromagnetism lectures to sophomores at the Department of Physics, he noticed a transferred student—Tsung-Dao Lee, from Zhejiang University, who never skipped classes but always lowered his head and read books as if he wasn’t listening to his lecturer. If you asked him questions, he would answer confidently, apparently his theoretical level was distinguished from his peers. One day when Professor Chi-Sun Yeh finished class, he walked to Tsung-Dao Lee and asked him what book he was reading, it was an advanced course of electromagnetism, Professor Chi-Sun Yeh said: “It’s such a waste of time for you to come to my class since you are already reading advanced books. You don’t need to attend classes.”

Tsung-Dao Lee was shocked upon hearing this, “but you can’t miss laboratory course, it’s mandatory.” Say Yeh, who recognized Tsung-Dao Lee was talented and started to put extremely strict requirements on him.

There was a time once the final exam of electromagnetism ended, Tsung-Dao Lee got a great score in theoretical test (58 out of 60), all his answers were right, but he didn’t get a full mark, Tsung-Dao Lee felt very aggrieved and asked Professor Yeh why.

“Since you didn’t do well in the laboratory course you can’t get full mark in the theoretical test!” Tsung-Dao Lee only achieved 25 (out of 40) in the laboratory test, therefore Professor Chi-Sun Yeh wrote this on the test paper: “Tsung-Dao Lee: 58+25=83”.

Professor Chi-Sun Yeh was strict and also generous to the talented student. In the spring of 1946, the Republic of China’s government authorized Professor Loo-keng Hua, Wu Ta-you and Zeng Zhaolun to recommend two excellent young assistants each in Math, Physics and Chemistry; they would go on to America and study PhD. In the area of Physics, Professor Wu Dayou recommended assistant Zhu Guangya from the Southwest Associated University, and then he requested Professor Chi-Sun Yeh, the Dean of the School of Science at Southwest Associated University to recommend the other one. Nobody thought Professor Yeh would recommend the sophomore student Tsung-Dao Lee, who was not an assistant at all and had the “right” to skip class. You can imagine how much stir this event created during that time. When Tsung-Dao Lee reached America, due to lack of enough education and experiences, he didn’t enter a university until another joint recommendation from Professor Wu Ta-you and Chi-Sun Yeh. In the autumn of 1946, Tsung-Dao Lee entered the University of Chicago. 11 years later, he and senior fellow Dr. Chen-Ning Yang won the Nobel Prize in America, which was also the first Nobel honor for a Chinese.

In 1998, the 100th anniversary celebration of the birth of Chi-Sun Yeh was held in Shanghai Jingye middle school. Dr. Tsung-Dao Lee addressed: “Professor Chi-Sun Yeh told me that my laboratory skills are bad, due to which, I could never get a 100 in the theoretical test. These words left a deep impression on me. Professor Yeh was a mentor who opened my mind and also greatly influenced my entire life.”

Dr. Chi-Sun Yeh had a quiet personality, he leave a few words or materials before passing away, among these, there were three hand-made paper sheets which were Dr. Tsung-Dao Lee’s theoretical test papers with “Tsung-Dao Lee: 58+25=83” on it.

Note: This article was adapted from Huang Doumi’s article “Chi-Sun Yeh living at Beimen Street” published by the journal “Yunnan Daily” on 11 May 2014.

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