Chinese American experimental physicist Chien-Shiung Wu was honored with a postage stamp issued by the U.S. Postal Service in virtual ceremonies on February 11, 2021. Wu, who came to the United States in 1936 to do graduate work, received her doctorate at UC Berkeley (under E.O. Lawrence and Emilio Segrè), and spent most of her career at Columbia University. She was a world authority on beta decay, coauthoring the standard reference work on the topic, and was known for her experimental prowess.

She worked on the Manhattan Project during World War II in the laboratories of Harold Urey in the gaseous diffusion (K-25) program for uranium enrichment.  She became a U.S. citizen in 1954 and a full professor at Columbia in 1958.  

Wu proposed and carried out the experiment necessary for theoretical physicists T-D Lee and C.N. Yang to demonstrate that the law of conservation of parity was invalid under weak nuclear interactions. This discovery of parity violation was a major contribution to particle physics and the development of the Standard Model. 

In his classic book The Ambidextrous Universe (first published in 1964), Martin Gardner noted that at the time Wu was already considered one of the world’s leading physicists and respected for the “care and elegance for which her experiments were always designed,” and he referred to this specific experiment of hers as “revolutionary” (Gardner 1979, 203–204). “Everybody expected Madam Wu to find a left-right symmetry in the process of beta-decay. Nature sprang a surprise.” Gardner compared her discovery to the Michelson-Morley experiment that paved the way for Einstein’s theory of relativity. The results of both were great surprises. “Madam Wu’s experiment may well prove to be equally historic” (Gardner 1979, 207–208).

Lee and Yang were awarded the Nobel Prize for Physics in 1957, but Wu’s role in the discovery was not publicly honored until 1978, when she was awarded the inaugural Wolf Prize in Physics.

Another important experiment of Wu’s was the first experimental confirmation of quantum results relevant to a pair of entangled photons as applicable to the Einstein-Podolsky-Rosen (EPR) paradox.

She was a member of the National Academy of Sciences, a 1975 recipient of the National Medal of Science, and a recipient of many other awards and medals.

In 1975, she became the first woman elected president of the American Physical Society. She was a determined advocate for women in science, becoming more outspoken late in her career.

Wu retired from Columbia in 1997, becoming a professor emerita, and died in New York City at the age of eighty-four.  

Columbia physics professor Brian Greene and Wu’s daughter spoke at the ceremonies announcing the commemorative postage stamp. It is a Forever stamp always equal in value to current first-class-mail one-ounce postage.

Reference

Gardner, Martin. 1979. The Ambidextrous Universe (revised edition). New York, NY: Charles Scribner’s Sons.