Biography of Chen Ning Yang a Chinese-born American theorectical physicist.
Chinese-born American theoretical physicist Chen
Ning F. Yang, born in Sept. 22, 1922, Hofei, Anhwei, China whose research with Tsung-Dao
Lee showed that parity—the symmetry between physical phenomena occurring in
right-handed and left-handed coordinate systems—is violated when certain
elementary particles decay. Until this discovery it had been assumed by
physicists that parity symmetry is as universal a law as the conservation of
energy or electric charge. This and other studies in particle physics earned
Yang and Lee the Nobel Prize for Physics for 1957.
Early Life of Chen Ning Yang
Yang's father, Yang Ko-chuen (also known as Yang
Wu-chih), was a professor of mathematics at Tsinghua University, near Peking. At
a tender age, Yang read the autobiography of Benjamin Franklin and adopted
“Franklin” as his first name. After graduation from the Southwest Associated
University, in K'unming, he took his B.Sc. in 1942 and his M.S. in 1944. He
studied in the United States, enrolling at the University of Chicago in 1946.
He took his Ph.D. in nuclear physics with Edward Teller and then remained in
Chicago for a year as an assistant to Enrico Fermi, the physicist who was
probably the most influential in Yang's scientific development. Lee had also
come to Chicago on a fellowship, and the two men began the collaboration that
led eventually to their Nobel Prize work on parity. In 1949 Yang went to the
Institute for Advanced Study in Princeton, N.J., and became a professor there
in 1955. He became a U.S. citizen in 1964.
Career of Chen Ning Yang
Almost from his earliest days as a physicist,
Yang had made significant contributions to the theory of the weak
interactions—the forces long thought to cause elementary particles to
disintegrate. (The strong forces that hold nuclei together and the
electromagnetic forces that are responsible for chemical reactions are
parity-conserving. Since these are the dominant forces in most physical
processes, parity conservation appeared to be a valid physical law, and few
physicists before 1955 questioned it.) By 1953 it was recognized that there was
a fundamental paradox in this field since one of the newly discovered
mesons—the so-called K meson—seemed to exhibit decay modes into configurations
of differing parity. Since it was believed that parity had to be conserved,
this led to a severe paradox.
After exploring every conceivable alternative,
Lee and Yang were forced to examine the experimental foundations of parity
conservation itself. They discovered, in early 1956, that, contrary to what had
been assumed, there was no experimental evidence against parity nonconservation
in the weak interactions. The experiments that had been done, it turned out,
simply had no bearing on the question. They suggested a set of experiments that
would settle the matter, and, when these were carried out by several groups
over the next year, large parity-violating effects were discovered. In
addition, the experiments also showed that the symmetry between particle and
antiparticle, known as charge conjugation symmetry, is also broken by the weak
decays. (See also CP violation.)
In addition to his work on weak interactions,
Yang, in collaboration with Lee and others, carried out important work in
statistical mechanics—the study of systems with large numbers of particles—and
later investigated the nature of elementary particle reactions at extremely
high energies. From 1965 Yang was Albert Einstein professor at the Institute of
Science, State University of New York at Stony Brook, Long Island. During the
1970s he was a member of the board of Rockefeller University and the American
Association for the Advancement of Science and, from 1978, of the Salk
Institute for Biological Studies, San Diego. He was also on the board of
Ben-Gurion University, Beersheba, Israel. He received the Einstein Award in
1957 and the Rumford Prize in 1980; in 1986 he received the Liberty Award and
the National Medal of Science.
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