Imagine being an expert in a very specialized area, such as beta-decay radiation, going and solving a problem with the standard model of particle physics because it relies heavily on your speciality, beta-decay radiation, sharing your results with your colleagues, and then being “forgotten” when those same colleagues win the Nobel Prize for solving that problem with the standard model. If that sounds unfair to you, the woman who is credited today as the queen of nuclear research faced this type of issue time and time again in her life. She was passed over for the Nobel Prize, denied a research position at UC Berkely, and fought to make the same salary of her male counterparts.
Wu was born in China in 1912, and attended a girls’ school founded by her father, who would go on to encourage his daughter to always strive for excellence and the best education. At age 11, Wu was sent to Suzhou Women’s Normal School, and while the option for the less competitive normal curriculum was available to her, Wu chose to enter the teacher training program, intending to continue her studies in university after finishing secondary school.
Graduating at the top of her secondary school class, Wu enrolled in China’s National Central University (later renamed Nanjing University) after completing her mandatory year of teaching from the teacher-training program in 1930. First studying mathematics, Wu quickly transferred to physics. Not only was she one of the star pupils of the school, she was very active in student politics, leading multiple protests against her government’s laissez-faire attitude to the high tensions between China and Japan, as well as other major issues of 1930s China.
Graduating (again) at the top of her class, Wu remained in China, completing 2 years of graduate-level studies in physics, and worked as an assistant at Zheijang University. She became a researcher at Academia Sinica’s Institue of Physics, where she worked under the mentorship of Professor Gu Jing-Wei. Her supervisor had studied in America, earning her PhD at the University of Michigan, and persuaded Wu to do the same. Wu’s application was accepted, and with funding from her uncle, Wu set sail for America in August 1936, seen off by her parents and uncle. Between a world war, civil uprising in China, and restrictions on travel, she would never see her parents again.
Landing in San Franciso, Wu was told that at the university of Michigan, her intended institute of graduate study, women were not even permitted to use the front entrance. Being the outspoken feminist that she was, Wu was having none of it and decided to study at Berkely, where she had been introduced to the Radiation Laboratory by physicist Luke Chia-Lu Yuan, instead.
Wu’s research and studies progressed quickly, producing a 2-part thesis. The first explored bremsstrahlung, the electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. This became her first work with beta-decay, a topic on which she would later be considered an authority. The 2nd part of Wu’s thesis investigated the production of radioactive xenon isotopes, produced by the nuclear fission of uranium. This would later secure her a position in the Manhattan Project’s Substitute Alloy Materials (SAM) Laboratory at Columbia University.
Being unable to secure a position at a university on the completion of her PhD in 1940, Wu remained as a post-doctoral fellow at the Radiation Laboratory. In 1942, she moved to the east coast of the United States with her colleague (and now-husband), Yuan, where Wu accepted a faculty position Smith College, a private women’s college in Massachusetts, while her husband worked on radar technology for RCA.
In 1944, during World War II, Wu joined the Manhattan Project’s SAM Laboratory, which supported the Manhattan Project’s gaseous diffusion program for uranium enrichment. In September 1944, a newly commissioned reactor had run into an unexpected problem; periodically shutting down. Another physicist on the project, John Archibald Wheeler, suspected that a fission product, xenon-135, was the root of the problem, being a potential neutron poison. Wu’s thesis work at Berkely on the radioactive isotopes of xenon was found to confirm this suspicion.
In her post-war research years, Wu continued her investigations into beta-decay. At Columbia, Wu had established connections with the Chinese community, and met theoretical physicists Tsug-Dao Lee and Chen Ning Yang. Lee and Yang’s work led them to question a law predicted by the Standard Model, the law of conservation of parity. Essentially, this law said that two particles that were so similar, theta and tau, that would ordinarily be considered the same particle decayed into two different states in different modes of decay. Lee and Yang’s research agreed with the law that parity was conserved for electromagnetic and strong interactions, but disagreed with the general assumption that it would also hold true for the weak interaction. Lee and Yang went to Wu for her expertise in experimental applications and Beta decay, as their model predicted that the Beta decay emitted from their sample material would violate the conservation of parity. While Lee and Yang eventually confirmed their theory (and Wu’s results) through experimentation, Wu had designed and conducted for them the experiment which would go on to earn them the Nobel Prize.
In later life, Wu became far more outspoken, protesting Taiwan taking political prisoners and fighting for gender equality. She spoke at a symposium at MIT, asking her mostly male audience if they thought nuclei had preferences for masculine or feminine treatment. When referred to by her husband’s name, Wu would either not respond or correct them to “Professor Wu.” After 30 years and numerous achievements to her name, Wu’s salary was finally adjusted to be the same as that of her male colleagues, 4 years before her retirement at age 70. She continued to be politically active until her death in 1997, protesting the Chinese communist government’s crackdowns on the people after incidents such as the Tiananmen Square massacre of 1989.
For being the first ever person awarded the prestigious Wolf Prize in physics, holding the position of President of the American Physical Society, and having received the Pupin Medal, National Medal of Science, Comstock Prize in physics, American Association of University Women’s Woman of the Year award, and John Price Wetherill Medal (I could go on here, but you get the idea), Chien-Shung Wu has received so little recognition in the STEM community for her contributions.
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