Chien-Shiung Wu
Born: May 31, 1912, Liuhe, Taicang, Jiangsu, China
Died: February 16, 1997, New York City, US
Chien-Shiung Wu was a Chinese American physicist who discovered that parity (handedness) is not conserved by the weak nuclear force. The asymmetry provided by this lack of parity of the weak force provides an explanation of why our universe contains matter and is mostly absent of anti-matter. If this were not the case there would be no matter or anti-matter in the universe, just radiation, and stars, galaxies, and planets and people would not exist.
Two of her colleagues, Tsung-Dao Lee and Chen-Ning Yang won the Nobel Prize for their subsequent work on parity, but Wu was omitted. She worked on the Manhattan Project, developing the gaseous diffusion process to separate the isotopes of uranium. She was so well accomplished that she was nicknamed the First Lady of Physics, the Chinese Madame Curie and the Queen of Nuclear Research.
Chien-Shiung Wu was born and raised in China during the turmoil of the tension between those who cherished traditional Chinese society and those who wished to replace it with a new culture. Her father, Zhong-Yi Wu, was an intellectual, a revolutionary and a feminist. She was an excellent student who exhausted the educational opportunities that China could provide for her. In 1936, at the age of 24 she came to America to study for a Ph.D. at the University of California, Berkeley, where she rapidly became a star student. Her dissertation on the fission products of uranium was swiftly classified.
After her Ph.D. graduation she had trouble finding a job. At that time, few universities had a woman in the physics faculty. She had to depend on her friends and mentors for research appointments. Obstacles to her employment included not only her gender but also her race. After Pearl Harbor, the West coast of the USA became strongly biased against anyone of Asian heritage. She moved to the East coast to a teaching position at Smith College and was later appointed to a position in the Princeton University physics faculty.
In 1944 Wu took a job at Columbia University and joined the Manhattan Project. Wu’s contribution to the project was to help determine the process for separating uranium into U-235 and U-238 isotopes by gaseous diffusion, a crucial step in producing uranium in large enough quantities for the atomic bomb. Her efforts with the project proved invaluable and she continued to lend her expertise in experimental physics after the war.
In 1956, Wu was approached by colleagues and theoretical physicists, Tsung Dao Lee and Chen Ning Yang, seeking her expertise in beta decay. They asked Wu to conduct a difficult experiment to prove their theory that there was no evidence of the law of conservation of parity, handedness, during beta decay. Wu’s experiments utilized radioactive cobalt at near absolute zero temperatures, which proved that identical nuclear particles do not always act the same way during beta decay. This finding contradicted the law of conservation of parity and supported Chen and Yang’s theory. Both men received a Nobel Prize in Physics in 1957 for their theory, but Wu did not receive the same recognition. However, in many textbooks it is referred to as the “Wu experiment.”
In 1949 two things happened that changed her life. The first was that Mao Zedong had established communism in the People’s Republic of China and travel home became impossible for her. She never saw her family again. Secondly, she and her student Irving Shaknov performed an experiment that showed entanglement for the first time. This result seems to have been mostly forgotten since. Entanglement, sometimes called spooky action at a distance, is one of the most active areas of modern quantum physics.
She married Luke Chia-Liu Yuan in 1942 and they had one child. In her later life Wu would spend most of her time visiting the People’s Republic of China, Taiwan, and different American states.
Regarded as a true heroine in her field, and as the “greatest female Chinese scientist in the twentieth century” in China, Wu has inspired future generations of physicists with her work. In 1990, the Nanjing Zijinshan Observatory of the Chinese Academy of Science named an asteroid after her. After retirement, Wu focused on encouraging young girls to pursue careers in the sciences through educational programs and spoke about her struggle to obtain recognition for her work, hoping to inspire women across the U.S. and China. She passed away at her home in New York on February 16, 1997. Her ashes were buried in the courtyard of Mingde School in China, the school her father started, and she attended as a young girl.