today’s scientist is a physicist named chien-shiung wu. wu is most famous for her work on beta decay and uranium fission—she was involved in the manhattan project and famously disproved the law of parity in her namesake experiment.
wu attended university at the university of nanjing, did a graduate-level study of physics at zhejiang university, and became a researcher at the academia sinica. her supervisor encouraged her to study abroad at the university of michigan, so she set off for the united states. however, she was shocked at the sexism in american academia, and decided to enroll at the much more liberal university of california, berkeley, instead. at school, wu quickly became known for her brilliance and beauty. in 1940, she presented her thesis, which had two parts. the first was on bremsstrahlung, electromagnetic radiation produced by the deceleration of a charged particle upon deflection by another charged particle, which marked the beginning of wu’s work on beta decay. the second was on the production of radioactive isotopes of xenon by the nuclear fission of uranium. she was particularly noted her knowledge of neutron adsorption cross sections, something that would lead to her later involvement with the manhattan project.
despite her outstanding thesis and enthusiastic recommendations from her supervisors, wu was unable to secure a research position, and her achievements were frequently played down because of her gender and race. wu became an instructor first at smith college, and then at princeton university, becoming the first female faculty in princeton’s physics department. in 1944, she joined the manhattan project’s substitute alloy materials laboratories at columbia university.
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slightly later that year, the b reactor, the first practical nuclear reactor, encountered some difficulty, where it would shut down and start up at random intervals. wheeler and fermi speculated that the problem was poisoning by xenon-135. to confirm this, emilio segrè recommended looking at wu’s thesis. wu’s paper revealed that xenon-135 has an unexpectedly large neutron adsorption cross section, unknowingly confirming wheeler and fermi’s hypothesis. a few months later, wu joined on the manhattan project and published a full paper on this phenomenon with segrè. her work in radioactive uranium separation helped build the standard model for producing enriched uranium, and she also worked on building improved geiger counters.
wu eventually distanced herself from the manhattan project because of its destructive effects, and became a research professor at columbia. here, she became the first to establish and experimentally prove the phenomenon of quantum entanglement, which had been proposed in the earlier epr paradox. her experiment confirmed pryce and ward’s hypothetical calculations on two entangled photons. wu also continued her earlier work in beta decay. fermi’s 1934 theory of beta decay was at odds with the results of an experiment by alvarez, so wu set out to redo the experiment. she was able to prove that alvarez’ discrepancies were the result of experimental errors, and produced results consistent with fermi’s theory, confirming his theory of beta decay.
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wu’s most famous experiment, however, disproved a long-accepted hypothetical law of elementary particle physics, the law of the conservation of parity. two other physicists, lee and yang, had performed calculations disproving the law for the weak interaction, but were unable to experimentally prove it. wu was the first to experimentally show that the weak interaction did not follow the law of the conservation of parity. her work was an instrumental discovery in particle physics, and eventually led to the general cp violation. otto frisch called the wu experiment the most influential since michelson-morley. lee and yang were awarded the nobel prize for this discovery in 1957. wu was not recognized for her role in the discovery until 1978, when she won the inaugural wolf prize. however, both lee and yang felt she should been awarded the nobel prize, and mentioned her in their acceptance speeches. yet another woman being robbed of a nobel prize that was instead bestowed upon her male colleagues! i wonder where we’ve seen this before…
in 1963, feynman and gell-man approached wu, asking for her to use her experimental prowess to confirm one of their hypotheses about beta decay. she then conducted a series of experiments on double beta decay, sickle cell disease, magnetism, and the mössbauer effect. in her later years, wu took to strong social advocacy, speaking out against human rights issues and gender discrimination in various forms. she became the first female president of the american physical society and met with president gerald ford to produce the office of science and technology policy.
wu is given many nicknames, including “first lady of physics”, “the chinese madame curie”, and “queen of nuclear research”. for good reason, too—her list of discoveries and achievements just goes on and on. yet, she is too often overlooked and unrecognized. being both chinese and a woman in the 1900s was a lethal combination that led to many of her achievements being downplayed and under-appreciated. while we can’t go back in time and award her that nobel prize, we can make sure her name is properly remembered today.
fun fact: chien-shiung wu has a stamp now! it was released on feb 11
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"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.”
-Chien-Shiung Wu
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(written 3/18/21)
