Chien-Shiung Wu
May 31, 1912 — February 16, 1997 — Liuhe, Jiangsu Province, China / New York, New York
Chien-Shiung Wu was a Chinese-American experimental physicist — nicknamed the "First Lady of Physics" — who contributed to the Manhattan Project, made major experimental contributions to beta decay theory, and designed the 1956 experiment that disproved the law of conservation of parity, one of the most startling discoveries in twentieth-century physics, for which two theorists won the Nobel Prize but she did not.
From China to Berkeley to Columbia
Born on May 31, 1912, in Liuhe, Jiangsu Province, China, Wu grew up in a family that actively encouraged her education at a time when that was unusual for women in China. She studied physics at National Central University and came to the United States in 1936 to pursue graduate work, earning her Ph.D. from UC Berkeley in 1940 under eminent nuclear physicist Emilio Segrè. After brief academic appointments, she joined the faculty of Columbia University in 1944, where she remained for the rest of her career. During World War II she contributed expertise to the Manhattan Project's development of radiation detection equipment.
Disproving Parity Conservation
In 1956, theoretical physicists Tsung-Dao Lee and Chen-Ning Yang proposed that the law of conservation of parity — the assumption that physical processes behave identically in mirror image — might not hold in weak nuclear force interactions. They were so confident in Wu's experimental skill that they approached her specifically to design and run an experiment to test this. Working with the National Bureau of Standards, Wu created an extremely challenging experiment involving cobalt-60 atoms cooled to near absolute zero in a magnetic field, observing the direction of electrons emitted during beta decay. The results were unambiguous: parity was not conserved. The law that had been assumed for decades was wrong. Lee and Yang won the Nobel Prize in Physics in 1957. Wu did not receive it, despite designing and executing the experiment.
Did You Know?
When Chien-Shiung Wu's parity experiment was confirmed, Nobel laureate Isidor Rabi — who had helped bring her to Columbia — said: "The experimentalist who demonstrated it with such elegance was Wu." Wolfgang Pauli, the theorist who had been most certain that parity must be conserved, reportedly said "That is total nonsense" when first told of the proposal — and then was silent for a long time when the experimental result was confirmed. Wu's exclusion from the Nobel Prize has been cited repeatedly in discussions of gender bias in science award selection, and she is considered one of the clearest cases of a Nobel oversight in physics history.
Legacy
Wu received numerous honors including the Wolf Prize and the National Medal of Science, and was the first woman to serve as president of the American Physical Society. She died on February 16, 1997. In 2021, the State of California renamed a middle school in San Francisco's Chinatown after her. Her story has become both a scientific and an equity narrative: a scientist whose experimental gifts were world-class, whose career was defined by producing results that others won prizes for, and who continued working with the same precision and professionalism regardless — a model of scientific integrity that transcends the inequities of her recognition.