KEYWORDS: Parity violation, Weak interactions, Conservation of vector current, Beta decay, Double-beta decay, Uranium-enrichment process
SHE THOUGHT IT
Chien-Shiung Wu was a Chinese-born American experimental physicist who significantly contributed to the research and development of nuclear and particle physics in the twentieth century. With the immense research that she had undertaken on beta decay, she established herself as a recognised authority on this type of radioactive decay1 (p. 363). She confirmed Enrico Fermi’s theory of beta decay, according to which most of the electrons should come out of the nucleus at high speeds. The speeds of the electrons that were commonly produced in experiments were significantly slower2 (p. 267). She proved his theory in a series of carefully designed experiments which enabled her to discover that the discrepancy sprang from the uneven thickness of radioactive materials used by previous researchers, and not from theoretical flaws1 (p. 366). Even though this and other experiments that Wu carried out emphasised her reputation of being extremely precise and striving for technical refinement1 (p. 366), the one that truly shook modern physics was the experiment that proved parity violation1 (p. 367).
Following the suggestion of two theoretical physicists, T. D. Lee and C. N. Yang, to test the so-called “law of conservation of parity” in weak interactions with possible experiments3 (p. 179), Wu proposed an experiment using a cobalt isotope (60Co) as beta source3, 4 (p. 179 & p. 70, resp.), which was extremely difficult to carry out. In order to maintain the radioactive source in a polarised state for a sufficient amount of time through the application of a strong magnetic field, she had to minimise the thermal vibration of the atoms of the cobalt-60 sample. To do so, the source had to be cooled down close to absolute zero temperatures which subsequently evoked the challenge to keep the detectors functioning under those extreme conditions5 (p. 127, 131, 133).
Besides this experiment that overthrew the hypothetical physical law, Wu conducted other significant experiments; e.g. a significant step toward the unification of electromagnetic and weak forces had been made thanks to her experiment on the conservation of vector current in beta decay, which practically confirmed the theory proposed by Feynman and GellMann1 (p. 367). Moreover, she had done research on double-beta decay, carried out on muonic atoms, in which, other than in normal atoms, electrons are replaced by muons1 (p. 367).
Nevertheless, Wu did not focus exclusively on beta decay over the course of her scientific career. During World War II, Wu participated in the Manhattan Project where she joined Harold Urey’s group, which was developing a process for separating U-235 from U-238 by gaseous diffusion6 (p. 45). Wu was therefore working on two main tasks; on the uranium-enrichment process using gas diffusion and on the development of a very sensitive gamma detector5, 6 (p. 94 & p. 45, 46, resp.). Towards the end of her career, she turned to biophysics and made important contributions to that field by conducting a series of investigations on haemoglobin in connection to the disease called sickle-cell anemia4 (p. 98).
Even though Chien-Shiung Wu was born in China while the country transitioned from the Qing dynasty to a republic, she had a happy childhood thanks to the encouragement of her father, who was a supporter of women’s rights, emancipation and equality, and, therefore, had founded the first school for girls in the region of Liuhe1, 2 (p. 363 & p. 257, resp.), Ming De Women’s Vocational School5 (p. 6). After receiving her elementary education there, Wu enrolled at age eleven in a teacher’s training programme at the boarding school in Suzhou – the Suzhou Women’s Normal School, but soon realised that the students, attending the regular high school programme, were taught more about science1, 7 (p. 364 & p. 1409, resp.). Eager for knowledge, she borrowed their books and studied mathematics, physics, and chemistry on her own2 (p. 258). She graduated with the best grades in her class in 1930 and, all the while being the representative of the underground student movement, continued her academic path at the elite National Central University in Nanjing, where she first studied mathematics and later, with the encouragement of her father, transferred into physics2 (p. 258, 259). After her graduation in 1934 and a year of teaching at Zhejiang University in Hangzhou, Wu started working on research on X-ray crystallography at the Academia Sinica in Shanghai under Zing-whai Ku, a Chinese female physicist, who had received her PhD from the University of Michigan and urged Wu to get additional training in the United States1, 2 (p. 365 & p. 259, resp.). Despite Wu’s plans to return to China as soon as possible, after her departure, she never saw her family again2 (p. 259).
Upon her arrival in San Francisco, she met Luke Chia-Liu Yuan, a Chinese student in physics at Berkeley, whom she would later marry. Despite her original plans, Wu decided to study at the University of California at Berkeley, namely under the supervision of Ernest O. Lawrence7 (p. 1409). She also collaborated with Julius Robert Oppenheimer and Emilio Segrè; she impressed them all and made a lot of progress in her research, despite constantly worrying about her family in China, which was at the time invaded by Japan1 (p. 365). Wu completed her PhD thesis in 1940: the first part of the thesis, which examined the bremsstrahlung (braking radiation) by using radioactive phosphorus 32P, was her first work on beta decay; while the second part presented her experiments with Segrè on the production of radioactive xenon and marked her entrance in the field of nuclear fission1 (p. 365).
After two more years at Berkeley, Wu and her husband moved to the East Coast, since more work opportunities were available there; she became the first female instructor at Princeton University. However, she only stayed there for a few months, because in March 1944 the Division of War Research at Columbia University in New York recruited her to help with the development of the radiation detectors as part of the Manhattan Project. After the war was over, she was one of the few physicists working within the Manhattan Project who were offered a position at Columbia University2 (p. 265). She became a senior investigator, gained more academic titles during her career and eventually, in 1952, became an associate professor with tenure. After the birth of their son Vincent Weichen Yuan in 1947, Wu and her husband considered returning to China, because the National Central University offered them professorships, but rather than living in a communist country, they decided to become US citizens in 19542 (p. 266).
Between 1952 and 1964, when her research was focused on beta decay, Wu confirmed Fermi’s theory of beta decay through experiments. Even though she also dealt with other topics after 1952, her passion for that field was rekindled in 1956, when two physicists, Lee and Yang, asked her to carry out the famous experiment which proved the parity violation in beta decay1 (p. 366). In the 1960s and 70s, she conducted several investigations which solidified her authority and reputation in the field1 (p. 367), such as the experiments on the conservation of vector current in beta decay, double-beta decay, haemoglobin regarding the sickle-cell anaemia, and also on Bell’s theorem. Besides this, she became more outspoken about the inequality experienced by women scientists, while trying to increase the funding for research and education. She also spoke out about other social and political issues in United States, as well as about issues in China and Taiwan – she was finally able to visit the mainland in 19731, 2 (p. 367, 368 & p. 278, resp.). After her retirement in 1981, Wu often travelled to China and Taiwan, lecturing and advising on science policy, and therefore became a role model for many young female scientists1, 2 (p. 368 & p. 277, resp.).
SCIENTIFIC COLLABORATION AND RECOGNITION
During her career, Chien-Shiung Wu collaborated with many well-known physicists, among them several Nobel laureates. While at Berkeley, she was doing research under the supervision of Ernest O. Lawrence, who would receive the Nobel Prize for the invention of cyclotron in 1939, and was mentored by Emilio Segrè, recipient of the Nobel Prize in 1959 for the discovery of antiproton. In spite of their recommendations and Wu’s growing reputation, which derived from the significance of her research, as well as from her contribution in solving the problem of the first nuclear reactor in Hanford in 1942 by recognising that xenon was the gas responsible for the poisoning of the reactor2, 3 (p. 264 & p. 178, resp.), Wu faced difficulties to obtain a stable position at a university due to the fact that she was both a woman and a Chinese immigrant, especially in a time of sexism at universities and general Anti-Asian sentiment in the USA4 (p. 28, 29). However, she got a position at Princeton University, in part because most male physicists were collaborating in projects regarding war3 (p. 178). When Wu was eventually called for an interview by the Division of War Research regarding the Manhattan Project, she showed such excellent knowledge that she was invited to join the project immediately2 (p. 265).
Her breakthrough in research, the parity experiment, which she carried out on the suggestion of Lee and Yang and in collaboration with the National Bureau of Standards, was instantly recognised by the scientific community1 (p. 367), but the Nobel Prize went only to Lee and Yang, namely for their theoretical work. The fact that Wu was not among the recipients has been subject to debate and is sometimes used as an example of gender injustice within the Nobel Prize awarding committee3 (p. 180). Nevertheless, during her lifetime, Wu received numerous awards for her outstanding contribution to proving the parity violation in weak interactions and for her other achievements. In recognition of her work, she was also honoured as “The First Lady of Physics Research”, “The Chinese Madame Curie”, “Queen of Nuclear Research”, and “The Most Distinguished Female Experimental Physicist in the World”5 (p. ix).
SHE SAID IT
There is only one thing worse than coming home from the lab to a sink full of dirty dishes, and that is not going to the lab at all.
cited in Cosmic Radiations: From Astronomy to Particle Physics (2001), eds. Giorgio Giacomelli / Maurizio Spurio / Jamal Eddine Derkaoui, NATO Science Series II, vol. 42, Boston, Kluwer Academic Publishers, p. 344.
I have always felt that in physics, and probably in other endeavors, too, you must have total commitment. It is not just a job. It is a way of life.
cited by Bertsch McGrayne, Sharon (2002), Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries, Washington DC, Joseph Henry Press, p. 263.
I was a woman when it paid to be and wasn’t one when it paid not to be […].
cited by Bertsch McGrayne, Sharon (2002), Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries, Washington DC, Joseph Henry Press, p. 269.
I wonder whether the tiny atoms and nuclei, or the mathematical symbols, or the DNA molecules have any preference for either masculine or feminine treatment. […] I sincerely doubt that any open-minded person really believes in the faulty notion that women have no intellectual capacity for science and technology. Nor do I believe that social and economic factors are the actual obstacles that prevent women’s participation in the scientific and technical field. […] The main stumbling block in the way of any progress is and always has been unimpeachable tradition.
cited by Bertsch McGrayne, Sharon (2002), Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries, Washington DC, Joseph Henry Press, p. 278.
It is shameful that there are so few women in science […]. In China there are many, many women in physics. There is a misconception in America that women scientists are all dowdy spinsters. This is the fault of men. In Chinese society, a woman is valued for what she is, and men encourage her to accomplishments — yet she remains eternally feminine.
cited by Krauss, Lawrence M. (2017), The Greatest Story Ever Told—So Far: Why Are We Here?, New York City, Atria Books.
THEY SAID IT
Her will power and devotion to work are reminiscent of Marie Curie, but she is more worldly, elegant, and witty.
Emilio Segrè (1980), From X-rays to Quarks: Modern Physicists and Their Discoveries, San Francisco, W. H. Freeman and Co., p. 260.
Her beta decay work was important for its incredible precision […]. Our lab was working in the same field. She did rather better than we did […]. She established a brilliant reputation. Those who tried to repeat her experiments and those who were competing with her found that she was always right. She always chose to do the significant and important experiments—no matter how difficult they were. And they were very difficult to do.
William A. Fowler cited by Bertsch McGrayne, Sharon (2002), Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries, Washington DC, Joseph Henry Press, p. 268.
Frau Wu is as obsessed with physics as I was in my youth. I doubt whether she ever even noticed the light of the full moon outside.
Wolfgang Pauli cited by Bertsch McGrayne, Sharon (2002), Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries, Washington DC, Joseph Henry Press, p. 277.
PRIZES, ACHIEVEMENTS, HONOURS
The following is a selection of Chien-Shiung Wu’s most relevant prizes, achievements and honours. Chien-Shiung Wu holds honorary degrees from more than twelve universities, including degrees from Yale University and Harvard University.
1958: Elected the seventh female member of the National Academy of Sciences (USA)
1958: The first woman awarded an honorary ScD by Princeton University (USA)
1958: Honorary ScD from Smith College (USA)
1959: Achievement Award, American Association of University Women (USA)
1959: The first female recipient of the Research Corporation Award (USA)
1959: Honorary ScD from Goucher College (USA)
1962: John Price Wetherill Medal, The Franklin Institute (USA)
1962: Woman of the Year Award, American Association of University Women (USA)
1963: Honorary ScD from Rutgers University (USA)
1964: The first female recipient of the Comstock Award, National Academy of Sciences (USA)
1965: Achievement Award, Chi-Tsin Culture Foundation (Taiwan)
1967: Honorary ScD from Yale University (USA)
1969: Elected an Honorary Fellow of the Royal Society of Edinburgh (UK)
1969: The first female recipient of the Honorary LLD from the University of Hong Kong (China)
1971: Honorary ScD from Russell Sage College (USA)
1971: Golden Anniversary Award, Delta Epsilon Sigma (USA)
1972: Endowed professorship from Columbia University (USA)
1973: first recipient of the title of Pupin Professor of Physics, initiated by Columbia University (USA)
1974: Scientist of the Year Award, Industrial Research Magazine (USA)
1974: Honorary ScD from Harvard University (USA)
1974: Honorary ScD from Bard College (USA)
1974: Honorary ScD from Adelphi University (USA)
1974: Boris Pregel Award, New York Academy of Sciences (USA)
1975: Tom Bonner Prize, American Physical Society (USA)
1975: Honorary ScD from Dickinson College (USA)
1975: Became the first female President of the American Physical Society (USA)
1976: Received the National Medal of Science from US President Gerald Ford (USA)
1978: First recipient of the Wolf Prize in Physics (Israel)
1980: Honorary ScD from the University of Pennsylvania (USA)
1981: Woman of the Year Award, St. Vincent Culture Foundation, sponsored by UNESCO and given by the President of Italy
1982: Honorary ScD from Columbia University (USA)
1982: Honorary ScD from the University of Southern California (USA)
1982: Honorary ScD from the State University of New York in Albany (USA)
1982: Honorary professorship from Nanjing University (China)
1982: Honorary professorship from the University of Science and Technology of China
1982: Honorary professorship from Peking University (China)
1983: Lifetime Achievement Award, Radcliff College, Harvard University (USA)
1984: Golden Plate Award, American Academy of Achievement (USA)
1984: Women’s Achievement Award, New York City Municipal Government (USA)
1984: Honorary ScD from the University of Padova (Italy)
1985: Blue Cloud Award, Institute of China (USA)
1986: Mayor’s Award of Honor for contributions to science and technology, Edward Koch, Mayor of New York (USA)
1986: Ellis Island Medal of Honor (USA)
1989: Honorary ScD from National Central University (Taiwan)
1990: The first living scientist to have an asteroid (2752 Wu Chien-Shiung) named after her by Purple Mountain Observatory of the Chinese Academy of Sciences (China)
1991: Pupin Medal for Service to the Nation in Science, Columbia University (USA)
1994: Achievement Award, Institute of China (USA)
1994: Ettore Majorana Prize – Erice – Science for Peace, Ettore Majorana Foundation and Centre for Scientific Culture (Italy)
In addition to her scientific research, later in life, Wu became active in science policy advising and various activities related to this, such as promotion. As the president of the American Physical Society, she wrote a letter to the president of the USA in order to explain the significance of research and the need for funding. The letter had great impact on presidential support for science and the re-establishment of the Office of Science and Technology Policy5 (p. 184, 185). Wu was also mobilizing the physics community by discussing issues that sciences were facing and possible solutions in the editorial of Physics Today5 (p. 184, 185). Besides this, Wu was teaching, lecturing and engaging in the development of science policies in China and Taiwan; for example, after her retirement she contributed to the progress of the Taiwanese synchrotron radiation programme and often travelled to Taiwan as she was not only a member of the Planning Board of the Synchrotron Radiation Program, but also part of the Technical Advisory Board5 (p. 213, 214).
Fida, Adriano (2010/2011), Chien-Shiung Wu, oil on canvas, 40 × 60 cm, <https://www.adrianofida.com/works/2010-2011> (last accessed 5 Jun. 2017).
Willoughby, Ele (2012), History of Physics – Madame Wu and the Violation of Parity, 2nd edition, linocut print on ivory Japanese kozo paper, 31.2 × 31.8 cm.
Weinstock, Maia (curator) (2014), Go Ahead and Do It: Portraits of Women in Science, Art.Science.Gallery., Austin, exhibition. Maia Weinstock’s LEGO minifigure of Chien-Shiung Wu was also exhibited among works of several other artists.
Hsieh, Angela (illus.) (2015), “A Scientific Pantheon [animated]”, animation, in “A Scientific Pantheon [animated]” (18 Oct. 2015), Rhode Island School of Design: Portfolios, Rhode Island School of Design, <http://portfolios.risd.edu/gallery/30434183/A-Scientific-Pantheon-animated> (last accessed 5 Jun. 2017). Three animated portraits of women scientists, including one of Chien-Shiung Wu.
DeBakcsy, Dale (2015), The Illustrated Women in Science: Year One, Castro Valley, The Gentleman-Scholars Publishing. Literary portraits of women scientists accompanied by comic strips; tenth is the portrait of Chien-Shiung Wu titled “Parity Girl: The Experimental Physics of Chien-Shiung Wu”.
Mondfrans, Jennifer (2016), Chien Shiung Wu, acrylic and oil on canvas, 18 × 24 cm, <http://www.jennifermondfrans.com/home/at-least-i-have-you/chien-shiung-wu> (last accessed 5 Jun. 2017). Portrait of Wu, accompanied by a fictive letter about her work and challenges she faced.
WORKS BY CHIEN-SHIUNG WU
The following is a selection of Chien-Shiung Wu’s most relevant works.
“Identification of Two Radioactive Xenons from Uranium Fission” (1940), Physical Review, 58 (10), 926.
with Emilio Segrè (1940), “Some Fission Products of Uranium”, Physical Review, 57 (6), 552.
“The Continuous X-Rays Excited by the Beta-Particles of 15P32” (1941), Physical Review, 59 (6), 481–88.
with Richard D. Albert (1948), “The Beta-Spectrum of S35”, Physical Review, 74 (7), 847–48.
with Richard D. Albert (1949), “The Beta-Ray Spectra of Cu⁶⁴”, Physical Review, 75 (2), 315–16.
with Richard D. Albert (1949), “The Beta-Ray Spectra of Cu64 and the Ratio of N + /N –”, Physical Review, 75 (7), 1107–08.
with Charles H. Townes / Leonard Feldman (1949), “Radioactivity of Chlorine³⁶”, Physical Review, 76 (5), 692–93.
“Recent Investigation of the Shapes of β-Ray Spectra” (1950), Reviews of Modern Physics, 22 (4), 386–98.
with Irving Shaknov (1950), “The Angular Correlation of Scattered Annihilation Radiation”, Physical Review, 77 (1), 136.
with Ernest Ambler / Raymond W. Hayward / Dale D. Hoppes / Ralph P. Hudson (1957), “Experimental Test of Parity Conservation in Beta Decay”, Physical Review, 105 (4), 1413–15.
with Luke C. L. Yuan (eds.) (1961), Nuclear Physics, Methods of Experimental Physics, vol. 5, part A, New York, Academic Press.
with Luke C. L. Yuan (eds.) (1963), Nuclear Physics, Methods of Experimental Physics, vol. 5, part B, New York, Academic Press.
with Y. K. Lee / L. W. Mo (1963), “Experimental Test of the Conserved Vector Current Theory on the Beta Spectra of B12 and N12”, Physical Review Letters, 10 (6), 253–58.
“The Universal Fermi Interaction and the Conserved Vector Current in Beta Decay” (1964), Reviews of Modern Physics, 36 (2), 618–32.
with Steven A. Moszkowski (1966), Beta decay, New York, Interscience Publishers.
with Lawrence Wilets (1969), “Muonic Atoms and Nuclear Structure”, Annual Review of Nuclear and Particle Science, 19, 527–606.
with Vernon W. Hughes (eds.) (1975), Muon Physics: Electromagnetic Interactions, vol. 1, New York, Academic Press.
with Vernon W. Hughes (eds.) (1975), Muon Physics: Weak Interactions, vol. 2, New York, Academic Press.
with Vernon W. Hughes (eds.) (1975), Muon Physics: Chemistry and Solids, vol. 3, New York, Academic Press.
Cooperman, Stephanie H. (2004), Chien-Shiung Wu: Pioneering Physicist and Atomic Researcher, New York, Rosen Publishing Group.
Gilbert, Lynn / Gaylen Moore (1981), Particular Passions: Talks with Women Who Have Shaped Our Times, New York, C. N. Potter – Crown Publishers.
Mattfeld, Jacquelyn A. / Carol G. Van Aken (eds.) (1965), Women and the Scientific Professions: The MIT Symposium on American Women in Science and Engineering, Cambridge, MIT Press.
Segrè, Emilio (1980), From X-rays to Quarks: Modern Physicists and Their Discoveries, San Francisco, W. H. Freeman and Co.
Swaby, Rachel (2015), Headstrong: 52 Women Who Changed Science – and the World, New York, Broadway Books.
Yost, Edna (1959), Women of Modern Science, New York, Dodd, Mead.
Zhu, Yuelin (2001), “Chien-Shiung Wu: An Intellectual Biography”, PhD dissertation, Department of the History of Science, Harvard University.
- Wang, Zuoyue (2008), “Wu Chien-Shiung”, New Dictionary of Scientific Biography, ed. Noretta Koertge, vol. 7, 363–68.
- Bertsch McGrayne, Sharon (2002), Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries, Washington DC, Joseph Henry Press.
- Hargittai, Magdolna (2015), Women Scientists: Reflections, Challenges, and Breaking Boundaries, Oxford University Press.
- Hammond, Richard (2010), Chien-shiung Wu: Pioneering Nuclear Physicist, New York, Chelsea House Publishers.
- Chiang, Tsai-chien (2014), Madame Wu Chien-Shiung: The First Lady of Physics Research, Singapore, World Scientific Publishing.
- Howes, Ruth H. / Caroline L. Herzenberg (1999), Their Day in the Sun: Women of the Manhattan Project (Labor and Social Change), Philadelphia, Temple University Press.
- Ogilvie, Marilyn Bailey / Joy Dorothy Harvey (2000), “Wu Chien-Shiung (1912–1997)”, The Biographical Dictionary of Women in Science: Pioneering Lives from Ancient Times to the Mid-20th Century, eds. Marilyn Bailey Ogilvie / Joy Dorothy Harvey, vol. 2, 1409–10.