Women in Nuclear History: Chien-Shiung Wu

Dr. Chien-Shiung Wu (1912-1997) called also “the first lady in Physics” is our 4th installment of Women in Nuclear. Her life was unusual and her contributions to nuclear science are magnificent.

  • Wu was a Chinese-American particle/experimental physicist who made significant contributions in the fields of nuclear and particle physics. Wu is best known for conducting the “Wu experiment” which proved that parity in beta decay process is NOT conserved. The discovery of parity violation was a major contribution to particle physics and the development of the Standard Model.
  • She was born in Jiangsu province in China. Her father was an engineer who encouraged her interests, her mother was a teacher. Wu was always an excellent student not only in math and sciences but also in Chinese classics and Western literature. Her calligraphy was exceptional.
  • Before matriculating at the National Central University, Wu spent the summer self-studying mathematics since she was worried that her previous schools for girls did not prepare her sufficiently for the university.
  • For two years after graduation she worked as an assistant at Zhejiang University. Her supervisor was a female professor who graduated from the Michigan University, she encouraged Wu to do the same, so Wu embarked on a ship for the US in 1936. She never saw her parents again since she could not travel to China until the 1970s.
  • Wu was shocked that at Michigan University women were not even allowed to use the front entrance; she decided to move to Berkeley in California. Her decision was also influenced by superb facilities there that included the first cyclotron by Ernest Lawrence, who received a Nobel prize in 1939.
  • At the Lawrence Lab she worked with Emilio Segre on the bremsstrahlung and beta decay. She was considered the most talented and the most beautiful experimental physicist and completed her PhD in 1940 but she did not secure a faculty position, so she continued as a post-doctoral researcher.
  • In 1942 she married Luke Yuan in the house of Robert Milikan. They had a son Vincent in 1947. They moved to the East Coast, where Wu became an assistant professor at the private women Smith College. She found this work frustrating since she could not do any research.
  • Later she accepted a job at Princeton University as the first faculty woman in the Physics department. From 1944 she worked on the Manhattan project – she helped with the process of separation of uranium into radioisotopes U-235 and U-238. She also helped in the Manhattan project with her prediction from her PhD thesis that Xe-135 is a nuclear poison.
  • After the end of the war in August 1945, Wu accepted an offer for associate research professor at Columbia University. In the mid 1950s, two theoretical physicists, Lee and Chen Ning Yang, started questioning hypothetical law of parity in beta decay. Dr. Wu carried out a rigorous experiment (with cryogenic Co-60 source) to test this theory. She confirmed that the symmetry parity in beta/weak interactions is NOT preserved.
  • This discovery provided her two colleagues with a Physics Nobel Prize in 1957. The fact that she was NOT awarded a Nobel prize in spite of both of her colleagues praising her contribution caused a rift among the scientists.
  • She never complained about her pay, although it was discovered that she was paid much less than her male colleagues. In 1975 she became the first female president of the American Physical Society. Later in life Wu became more outspoken against injustices in China and Taiwan and against gender discrimination. She protested the crackdown in China that followed the Tiananmen Square massacre of 1989. In 1997, she died after a stroke and was buried in China according to her wishes.