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Tsung-Dao Lee

Tsung-Dao Lee

Tsung-Dao Lee (born 1962) disproved the principle of parity.

Tsung-Dao Lee and his colleague physicist Chen Ning Yang developed the revolutionary theory that the unusual behavior of the K-meson (a subatomic particle) is a result of its violating a supposedly inviolable law of nature, conservation of parity, which defines the basic symmetry of nature. A few months after their theory had been announced, fellow physicist Chien-Shiung Wu obtained experimental confirmation of their remarkable discovery. For their work, Lee and Yang were awarded the 1957 Nobel Prize in physics.

Lee was born in Shanghai, China, on November 24, 1926. He was the third of six children born to Tsing-Kong Lee, a businessman, and Ming-Chang Chang. Lee attended the Kiangsi Middle School in Kanchow and, after graduation, entered the National Chekian University in Kweichow. After the invasion of Japanese troops in 1945, Lee fled to the south, where he continued his studies at the National Southwest Associated University in Kunming.

In 1946, Lee was presented with an unusual opportunity. One of his teachers at Kunming was the theoretical physicist Ta-You Wu. When Wu decided to return to the United States (where he had worked toward his Ph.D. degree), he invited Lee to accompany him. Lee accepted the offer, but found himself in a somewhat peculiar position. He had not yet received his bachelor's degree and found that only one American university would accept him for graduate study without a degree. He therefore decided to enroll in that institution, the University of Chicago.

At Chicago, Lee selected a topic in astrophysics for his doctoral research. Working under physicist Enrico Fermi, he completed that research and was awarded his Ph.D. in 1950 for his dissertation, on the hydrogen content of white dwarf stars. While at Chicago, Lee also renewed his friendship with physicist Chen Ning Yang. Lee and Yang had been acquaintances at Kunming, but they became very close friends after both reached the United States. They were separated in 1950 when Lee went to the Yerkes Astronomical Observatory at Lake Geneva, Wisconsin, and Yang went to the Institute for Advanced Studies at Princeton University. Lee then spent the next year (1950-51) as a research associate at the University of California at Berkeley. The two friends were reunited in 1951, however, when Lee accepted an appointment at the Institute for Advanced Studies.

Lee's departure from Princeton in 1953 for a post as assistant professor of physics at Columbia University seems to have had little effect on his collaboration with Yang. The two worked out a schedule that allowed them to continue meeting once a week, either in New York City or in Princeton. By the spring of 1956, these regular meetings had begun to focus on a particularly interesting subject, a subatomic particle known as the K-meson. Discovered only a few years earlier, the K-meson puzzled physicists because it appeared to be a single particle that decayed in two different ways. The decay schemes were so different that physicists had become convinced that two distinct forms of the K-meson existed, forms they called the tau meson and theta meson.

The single difference between these two mesons was that one form had even parity and the other form had odd parity. The term parity refers to the theory that the laws of nature are not biased in any particular direction. That is, if one has two sets of interactions that are mirror images of each other, the physical laws describing those interactions are identical. This concept is known as the conservation of parity, a concept long held by physicists.

The problem that Lee and Yang attacked was that vast amounts of experimental evidence suggested that the theta and tau mesons were one and the same particle. The only contrary evidence was that the two mesons had opposite parity and, therefore, supposedly could not be identical. During an intense three-week period of work in the spring of 1956, Lee and Yang solved this puzzle. Their solution was to suggest, simply enough, that in some types of reactions, parity is not conserved. The beta decay of the (one and only) K-meson was such a reaction. They then devised a series of experiments by which their theory could be tested. The fundamental elements in the Lee-Yang theory were announced in a paper sent to the Physical Review on June 22, 1956 and later given the title, "Question of Parity Conservation in Weak Interactions."

About six months later, the experiments suggested by Lee and Yang were carried out by one of their colleagues, Chien-Shiung Wu, first at Columbia and then at the National Bureau of Standards. The experiments confirmed the Lee-Yang prediction in every respect. Less than a year later, the two theorists were awarded the 1957 Nobel Prize in physics for their work.

After promotions to associate professor (1955) and professor (1956) at Columbia, Lee returned to the Institute for Advanced Studies in 1960 for three years. He then was appointed Enrico Fermi Professor of Physics at Columbia in 1963. In 1984, he was made University Professor at Columbia. Beginning in 1981, Lee held appointments as honorary professor at a number of Chinese universities, including the University of Science and Technology (1981), Jinan University (1982), Fudan University (1982), Quinghua University (1984), Peking University (1985), Nanjing University (1985), and Zhejiang University (1988). He married Hui-Chung Chin (also known as Jeanette) on June 3, 1950, while they were both students at Chicago. The Lees have two sons, James and Stephen.

Further Reading

Crease, Robert P., and Charles C. Mann, The Second Creation, Macmillan, 1986, pp. 205-7.

McGraw-Hill Modern Scientists and Engineers, Volume 2, McGraw-Hill, 1980, pp. 215-16.

Nobel Prize Winners, H. W. Wilson, 1987, pp. 615-17.

Weber, Robert L., Pioneers of Science: Nobel Prize Winners in Physics, American Institute of Physics, 1980, pp. 167-68.

Bernstein, Jeremy, "A Question of Parity," in New Yorker, May 12, 1962, pp. 49ff. □

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Lee, Tsung-Dao

Tsung-Dao Lee

Born: November 24, 1926
Shanghai, China

Chinese-born American physicist

Chinese-born physicist (specialist in the relationship between matter and energy) Tsung-Dao Lee was a cowinner of the 1957 Nobel Prize in physics. Lee and his colleague physicist Chen Ning Yang (1922) developed a theory about behavior of the K-meson (a particle that is smaller than an atom), which resulted in major changes in the science of particle physics.

Early life

Tsung-Dao Lee was born in Shanghai, China, on November 24, 1926. He was the third child of businessman Tsing-Kong Lee and his wife Ming-Chang Chang. Lee attended the Kiangsi Middle School in Kanchow, China. After graduation he entered the National Chekian University in Kweichow, China. When Japanese troops invaded the area in 1945, Lee fled to the south, where he continued his studies at the National Southwest Associated University in Kunming, China.

Leaves for the United States

In 1946 Lee was presented with an unusual opportunity. When one of his teachers at Kunming, a physicist named Ta-You Wu, decided to return to the United States (where he had worked toward his doctorate degree), he invited Lee to accompany him. Lee accepted the offer but found himself in a somewhat peculiar position. He had only completed two years of college and found that only one American university, the University of Chicago, would accept him for graduate study without a degree. He decided to enroll there. Lee married Hui-Chung Chin (also known as Jeanette) in 1950, while they were both students at Chicago. The couple eventually had two sons.

In Chicago, after working under physicist Enrico Fermi (19011954), Lee was awarded his doctorate in 1950 for his study of the amount of hydrogen in white dwarf stars (stars of low brightness with a mass similar to that of the sun). Lee also renewed his friendship with physicist Chen Ning Yang, whom he had known in Kunming. The two began working together. In 1950 Lee went to the Yerkes Astronomical Observatory at Lake Geneva, Wisconsin, and Yang went to the Institute for Advanced Studies at Princeton University in Princeton, New Jersey. Lee then spent the next year as a research assistant at the University of California at Berkeley before accepting an appointment at Princeton in 1951, again reuniting with Yang.

Revolutionary theory

Even after Lee left Princeton in 1953 for a post as assistant professor of physics at Columbia University, he continued to work with Yang. The two worked out a schedule that allowed them to continue meeting once a week, either in New York City or in Princeton. These meetings had begun to focus on a subatomic (smaller than an atom) particle known as the K-meson. Discovered only a few years earlier, the K-meson puzzled physicists, because it appeared to be a single particle that decayed in two different ways. The decay patterns were so different that physicists had become convinced that two different forms of the K-meson existed, forms they called the tau-meson and theta-meson.

The single difference between these two particles was that one form was conserving parity and the other form was not. Following a concept long held by physicists, if the properties of a particle and its mirror image are the same, it is said to be "conserving parity." The problem that Lee and Yang attacked was that all other evidence suggested that the theta-and tau-mesons were one and the same particle. During a three-week period of work in 1956, Lee and Yang solved the puzzle by suggesting that, in some types of reactions, parity is not conserved. The decay of the (one and only) K-meson was such a reaction. They then created a series of experiments by which their theory could be tested.

The basic elements in the Lee-Yang theory were announced in a paper sent to the Physical Review in June 1956. Six months later another physicist, Chien-Shiung Wu, carried out their suggested experiments, first at Columbia and then at the National Bureau of Standards. The Lee-Yang prediction was found to be correct in every respect. Less than a year later, the two friends were awarded the 1957 Nobel Prize in physics for their work.

Career after the Nobel Prize

After a promotion to professor (1956) at Columbia, Lee returned to the Institute for Advanced Studies in 1960. He then was appointed Enrico Fermi Professor of Physics at Columbia in 1963. In 1984 he was made University Professor at Columbia. In 1980 Lee created a program to give talented Chinese physics students the opportunity to earn graduate degrees in American schools, as he had. In 1989 he helped create the China Center of Advanced Science and Technology World Laboratory, and he continues to travel to China every year to encourage scientists there. In 1994 Lee became a member of the Chinese Academy of Sciences. In 2000 the World Journal (a Chinese newspaper in North America) included Lee in its list of the "Most Notable 100 North American Chinese of the Century." The Nobel Prize winner continues to work as a professor at Columbia and is involved in a variety of physics research projects.

For More Information

Bernstein, Jeremy. "A Question of Parity." New Yorker (May 12, 1962): p. 49.

Crease, Robert P., and Charles C. Mann. The Second Creation. New York: Macmillan, 1986, pp. 2057.

McGraw-Hill Modern Scientists and Engineers. vol. 2. New York: McGraw-Hill, 1980, pp. 21516.

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Lee, Tsung-Dao

Tsung-Dao Lee (dzŏŏng´-dou´ lē´), 1926–, American physicist, b. China, Ph.D. Univ. of Chicago, 1950. He was a member (1951–53) of the Institute for Advanced Study, Princeton; and professor of theoretical physics there (1960–63). He also served as professor at Columbia (1953–60, 1963–). Lee is known for his studies in statistical mechanics, elementary particles, and astrophysics. He shared with Chen-ning Yang the 1957 Nobel Prize in Physics for researches refuting the law of conservation of parity.

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Lee, Tsung-Dao

Lee, Tsung-Dao (1926– ) US physicist, b. China. He and his colleague, Chen Ning Yang, showed that among the weak interactions of subatomic particles, the law of conservation of parity (that nature, in effect, makes no distinction between right- and left-handedness) does not always hold. Lee and Yang received the 1957 Nobel Prize in physics.

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