Chen Ning Yang | Biography

Chen Ning Yang was born in the city of Hofei, in Anhwei province, China, on September 22, 1922, to Ke Chuan Yang and the former Meng Hwa Loh. When Yang finished high school, he entered the National Southwest Associated University, where he majored in physics and earned his B.S. degree in 1942. He then continued his studies at Tsinghua University, where his father was a professor of mathematics, and earned his M.S. in 1944. He then taught high school for one year before deciding to begin work on a Ph.D. in physics. Because doctoral programs in physics were not then available in China, Yang decided to come to the United States, where he particularly wanted to study with physicist Enrico Fermi. Yang traveled to New York City (by way of India, the Suez Canal, and Europe) under the impression that Fermi was still at Columbia, where he had come upon his arrival in the United States in 1938. When Yang heard that Fermi had only recently left for a new post at the University of Chicago, he followed Fermi and enrolled in the doctoral program at Chicago. When Yang received his doctorate in 1948, he remained in Chicago as an instructor for a year, and then took a job at the Institute for Advanced Study in Princeton, New Jersey.

While in Chicago, Yang developed a friendship with fellow student Tsung-Dao Lee. Yang and Lee had attended Southwest University in China at the same time, but Yang was a year ahead of Lee, and the two were not particularly close. The situation at Chicago was very different. The two compatriots shared housing at the university's International House and soon became close friends. They began to spend time together, talking almost every day about issues in physics. By the spring of 1956 they had settled on a problem of particular interest to both of them, the decay of the K-meson (a subatomic particle) and the question of parity conservation.

The law of parity conservation, first proposed in 1925, defines the basic symmetry of nature, referring to the theory that the laws of nature are not biased in any particular direction. Consequently, nature is unable to distinguish between right- and left-handedness in particles--the smallest building blocks of energy and matter. Any reaction that involves a right-handed particle would be the same for a left-handed particle. By the 1950s, however, one particular kind of nuclear reaction had raised some questions about the validity of that law. That reaction involved the decay of an elementary particle called the K-meson.

Experiments appear to have shown that K-mesons can decay in one of two ways. The explanation that had been postulated for this observation was that two kinds of K-mesons exist; Yang and Lee suggested another possibility. Perhaps only one form of the K-meson exists, they said, and it sometimes decays in such a way that parity is conserved and sometimes in such a way that parity is not conserved. In June of 1956 Yang and Lee formulated their thoughts on the K-meson puzzle in a now-classic paper titled "Question of Parity Conservation in Weak Interactions." They not only explained why they thought that parity conservation might not occur, but they also outlined experimental tests by which their hypothesis could be evaluated.

Within a matter of months, the proposed experiments were under way. They were carried out by a group of researchers under the direction of Chien-Shiung Wu, a compatriot of Yang and Lee at Columbia University. Wu assembled a team of colleagues at Columbia and at the National Bureau of Standards to study K-meson decay along the lines suggested by Yang and Lee. By January of 1957, the preliminary results were in. The evidence confirmed that Yang and Lee were correct: Parity was not conserved in the decay of K-mesons. For their work on this problem, Yang and Lee were awarded the Nobel Prize for Physics only ten months after Wu's experiments had been completed--almost record time for recognition by a Nobel Prize committee. In addition to the Nobel Prize, Yang was awarded the 1957 Albert Einstein Award, and the 1980 Rumford Medal of the American Academy of Arts and Sciences.

In 1950, Yang married Chih Li Tu, a former high school student of his in China. They have two sons, Franklin and Gilbert, and a daughter, Eulee. In 1965, Yang ended his long affiliation with the Institute for Advanced Study to accept an appointment as Albert Einstein Professor of Physics and Director of the Institute of Theoretical Physics at the State University of New York at Stony Brook.