as CP (the product of parity and charge parity) invariance and vector current conservation in ß-decay. Wu's experiment was a milestone in nuclear physics. For the theoretical work that had prompted the experiment, Yang and Lee were awarded the Nobel Prize.
After the parity experiment, Wu moved on to other areas. She returned occasionally to ß-decay, for example, to confirm Feymnan and GellMann's theory of conservation of vector current in ß-decay. This theory, which was developed in the burst of research that followed Wu's discovery of parity violation, is expressed in a formula that describes observed phenomena of weak interactions that are charged. Wu was recognized on numerous occasions for her outstanding work, including many awards, acceptance into the National Academy of Sciences, a full professorship (and later an endowed professorship) at Columbia, and many honorary degrees. After her retirement in 1981 she lectured and taught in many places, addressing issues of policy as well as science. Concerning the lack of women in science, she maintained that "unimpeachable tradition," rather than women's intellectual capacity or socioeconomic factors, was the reason that there were so few women in science. It is characteristic of Chien-Shiung Wu to formulate the problem with such clarity. As in her scientific endeavors, Wu sought to identify the real question and seek a definitive answer.
With a keen ability to find fundamental questions and with no fear of the difficult, Chien-Shung Wu carried out many difficult and important experiments that shaped modern physics, particularly in the area of nuclear physics. Like her idols, Marie Curie and Lise Meitner, Wu combined her love of physics and an incredible determination to change the way we understand nature. Although she could be completely absorbed by her work, she never lost her sense of wonder at the interesting world she sought to understand. As Wu later said of the parity conservation experiment, "These were moments of exhilaration and ecstasy! A glimpse of this wonder can be the reward of a lifetime. Could it be that excitement and ennobling feelings like these have kept us scientists marching forward forever!"6