Chien-Shiung Wu

Hayeon Kwak
Sep 25, 2023
4 min read

"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!" - Chien-Shiung Wu

DOB: May 31, 1912

Nationality: Chinese-American

On May 31, 1912, Chien-Shiung Wu was born in Liuhe, China. Her mother, Fanhua Fan, was a teacher, and her father, Zhon-Yi Wu, was an engineer.

Her parents were intellectuals, revolutionaries, and feminists. At a time when girls were expected to be obedient and delicate shadows, her parents' name for her translated to “strong hero.”

Zhong-Yi Wu founded one of the first girls’ schools in China, Mingde Women’s Vocational Continuing School. Chien-Shiung Wu attended her father’s school and developed a love for learning, especially in science and mathematics. Chien-Shiung Wu went on to attend Nanking University, one of the most prestigious schools for higher learning in China. Later, she recalled that being able to collaborate with other women in the field and reading about their successes, such as Marie Curie, inspired her to pursue ambitious goals. In 1934, Chien-Shiung graduated with a Bachelor of Science degree at the top of her class.

After graduation, Wu taught at the National Zhejiang University from 1935 to 1936 and worked under the mentorship of female professor Jing-Wei Gu in a physics laboratory where she conducted her first experimental research in X-ray crystallography. Dr. Gu encouraged Chien-Shiung Wu to study further in the US, and Chien-Shiung enrolled at the University of California at Berkeley in 1936.

A leading physicist and Nobel prize recipient Professor Ernest Lawrence taught her, and she was also able to learn from other renowned physicists such as Robert Oppenheimer. Wu graduated in 1940 with a Ph.D. and eventually went on to teach physics at Smith College and later became the first female instructor in Physics at Princeton University. Despite her impressive education, research, and experience, she struggled to find a job after her graduation and depended on mentors for research appointments for two years.

Her applications were turned down time after time by research universities because, at the time, no prestigious school had women on the physics faculty. Furthermore, gender bias was not her only obstacle. Anti-Asian sentiment in the US grew only one year after her arrival, triggered by Japan’s attack on Pearl Harbor and escalation in World War II even cut off communication with China. Even during her years as a student at UC Berkeley, she faced discrimination from teachers and staff. When Oppenheimer left to lead the Manhattan Project, he invited many of his Berkely students with him but left Wu, arguably the most acclaimed among her peers, behind.

Undeterred, Wu continued to pursue her interests and grow her career. In 1944, Wu was finally accepted by the Manhattan Project at Columbia University, a classified gathering of the country’s leading nuclear scientists by the government with the mission to produce the first atomic weapons in the United States. Her contributions to the Manhattan Project were invaluable in determining the process for separating uranium into U-235 and U-238 isotopes, unlocking a crucial step in the large-scale uranium production needed for the atomic bomb.

But far more famous than her contributions to the Manhattan Project and her entanglement experiments, was her work on the reversal of the law of conservation of parity in nuclear physics.

Conventional scientific thought believed symmetry would be an immutable and consistent pattern across most building blocks of our universe. This long-established law of symmetry was challenged by Wu’s colleague T. D. Lee and his research partner Chen Ning Yang, when they theorized that nuclear particles in beta decay may behave in a symmetrical pattern, breaking the law of symmetry. When Lee and Yang reached out to Wu for advice, she was willing to question mainstream thinking and designed and led an experiment to prove her colleagues' hypothesis.

For months Wu worked in laboratories between New York City and Washington, studying experiments with the National Bureau of Standards (NBS). To observe whether the daughter particles of nuclear decay shot out in a symmetrical pattern or had “right-handed” or “left-handed” behaviour, Wu and her partners used a strong magnet at temperatures of near absolute zero to align the magnetic spins of cobalt 60 nuclei which caused electrons to shoot out from the nuclei.

According to mainstream physics, reversing the nuclei’s spin should have produced a mirror image of the same spin. Instead, experimenters found the nuclei kept emitting electrons in one direction relative to their spin, showing beta-decay particles were not symmetrical but were “left-handed.”

Soon after Wu’s findings were published, Yang, Lee, Wu, and other experimentalists who participated in the experiment were published across papers. In the same year, Wu, Yang, Lee, and others presented their findings at the New York Hotel in front of the American Physical Society, where so many people were drawn by Wu’s groundbreaking findings that the New Yorker recalled “so immense a crowd that some of its members did everything but hang from the chandeliers.”

Although the Nobel Prize allowed up to three recipients, Wu was excluded and only Yang and Lee received the honor in 1957. This scandal only highlighted the prevalence of gender inequality in science. Many physicists who knew of Wu’s experiments criticized the institution’s prejudice against women. In his Nobel lecture, Yang boldly emphasized the crucial role Wu’s experiments had in disproving the principle of parity, and Lee pushed the Nobel Committee to recognize Wu’s work. Even Oppenheimer publicly pointed out that Wu should have received the Nobel Prize as well. In 1991, a group of scientists organized by Douglas Hofstadter wrote to the Nobel Committee advocating for Wu to receive a physics prize.

After disapproving the principle of parity, Wu was finally promoted to full professor at Columbia University, became the first woman to receive the Comstock Prize from the National Academy of Science, and the first physicist to receive the Wolf Prize. She was also the first female president of the American Physical Society and the first physicist to have an asteroid named after her before her death. Her work opened doors for women and people of colour in science and teaching in the US.

Today Wu’s name is invoked as an example of sexism in sciences and challenges current sexism in science. Just as learning of Marie Curie’s work inspired Wu in her youth, she is revered in China and encourages a new generation of young girls.