Chien-Shiung Wu (1912-1997)

---

“Beta decay was...like a dear old friend. There would always be a special place in my heart reserved especially for it.”
–Chien-Shiung Wu

---

National Medal of Science (NMS) recipient in 1975 “for her ingenious experiments that led to new and surprising understanding of the decay of the radioactive nucleus.”

Chien-Shiung Wu grew up in Liuhe, in the Jiangsu province of China. After receiving her bachelor’s degree in 1934 from the National Central University in Nanking, Wu came to the United States to pursue graduate studies at the University of California, Berkeley. She earned her Ph.D. in physics and then taught briefly at Smith College and Princeton University before accepting a position in the Division of War Research at Columbia University in 1944. Wu joined the Manhattan Project, the secret U.S. Army laboratory set up for the purpose of developing the atomic bomb, and was involved in research on radiation detection and uranium enrichment.

After the war, Wu remained at Columbia, where she developed expertise in radioactive beta decay and earned a reputation as a meticulous experimental physicist. In the mid-1950s, Wu was approached by two of her colleagues in the field, Tsung-Dao Lee of Columbia and Chen Ning Yang of the Institute for Advanced Study in Princeton, N.J. Lee and Yang had proposed that conservation of parity, a law stating that nature does not differentiate between left and right, did not hold for weak nuclear reactions. The physicists asked Wu to determine a way to carry out an experiment that would test their hypothesis.

Using a laboratory at the National Bureau of Standards (now the National Institute of Standards and Technology) in Washington, D.C., Wu placed colbalt 60 in a strong electromagnetic field and observed what happened when the nuclei broke down. She found that more particles flew off in the direction opposite the spin of the nuclei, thereby confirming that the conservation of parity law was invalid. Though Wu did not share in the Nobel Prize that Lee and Yang received for this work, the NMS recognized her achievements and she was also awarded the first Wolf Prize in Physics from the Wolf Foundation in Israel.

Wu remained an influential member of the physics community until her retirement from Columbia in 1981. Her 1965 book, “Beta Decay,” is still a standard reference text and, in 1975, she became the first female president of the American Physical Society. Wu died of a stroke in 1997, and is survived by her husband, Luke C.L. Yuan, a retired experimental physicist, and her son, Vincent, a research scientist at Los Alamos National Laboratory. Tsung-Dao Lee called Wu “one of the giants of physics.”