When Chien-Shiung Wu (1912–1997) was a student at the prestigious Suzhou Girls’ High School in the Chinese city of Suzhou, she encountered a biography of Marie Curie, the great chemist and physicist who became the first woman to win a Nobel Prize and the only woman to win it twice.
Curie’s achievements ignited a lifelong passion in a teenager who was already so devoted to science that she spent her free time teaching herself physics from textbooks borrowed from friends. But Wu probably never imagined that she would grow up to be a scientific pioneer just like her hero, or that her contributions would earn her the nickname “the Chinese Madame Curie”.
Born in 1912 to two politically progressive parents, Wu came to symbolise their hopes for the future of the country. With the overthrow of the weak and corrupt Qing dynasty and the inauguration of the Republic of China, her parents saw an opportunity to challenge the long-held prejudice against women’s education. They founded the Mingde School for Girls together, with Wu’s father taking on the job of principal and her mother tasked with persuading families in the region to enrol their daughters. Wu was one of their first students, and she whizzed through the elementary grades on offer and left home at the age of 10 or 11 to continue her education at Suzhou Girls’ High, some 80 kilometres away from her birthplace of Liuhe.
Her grades in high school were so impressive that she was immediately offered a place at the National Central University in Nanjing, the usual entrance examination requirement having been waived.
By the time she graduated with top marks in 1934, her chosen subject of physics had become one of the liveliest and most exciting disciplines in the world: breakthroughs like Albert Einstein’s theory of relativity had revolutionised the field and each year promised ever more astounding discoveries. But China had no graduate programme for aspiring physicists and she quickly realised that she would have to fly the nest to pursue her dream.
In August 1936, she waved goodbye to her family and friends from the President. It was the last time she saw her mother and father.
After switching from the University of Michigan to the University of California, Berkeley, Wu immersed herself in her graduate degree, only to receive news a year in that Japan had invaded China. She didn’t hear from her parents for eight years and the conflict between the two nations would later merge into the Second World War with the bombing of Pearl Harbour in 1941.
Wu was extremely worried about her family, but work provided a much-needed distraction. She carved out a reputation as a meticulous and dogged experimental physicist of the highest calibre. When future Nobel Prize winner Enrico Fermi had trouble with his experiments, he was told to call on Wu.
Among physicists, the saying went: “If the experiment was done by Wu, it must be correct.” In his autobiography, her mentor Emilio Segrè recalled: “Wu’s will power and devotion to work are reminiscent of Marie Curie, but she is more worldly, elegant, and witty.”
In 1944, Wu was invited to join the top-secret Manhattan Project under the auspices of her former professor, Robert Oppenheimer, to work on crucial problems including uranium enrichment and radiation detection at Columbia University. She was the only Chinese person to work in the war department and one of the only women among its senior researchers.
In 1945, she saw the culmination of her efforts with the development of the atomic bomb. Though she later expressed regret over its use on Hiroshima and Nagasaki, the work that she did helped to usher the Second World War to a much earlier close and allowed her to finally receive word that her family was safe.
She expressed the hope that the devastating bomb was a one-off: “Do you think that people are so stupid and self-destructive? No. I have confidence in humankind. I believe we will one day live together peacefully.”
When the war ended, Wu stayed on at Columbia University to teach and continue her research into beta decay, a radioactive process in which the nucleus of an atom emits beta particles, forcing the atom to change into a new element.
Nobody actually knew how beta decay worked and Wu was on the cutting edge of this new science. Her expertise brought her to the attention of Tsung-Dao Lee and Chen-Ning Yang, two scientists who were investigating a law in physics known as the conservation of parity. It was believed that fundamental symmetry governed everything in nature, including the behaviour of atomic particles. But Lee and Yang theorised that parity might not exist with beta decay; they just needed someone to prove it.
Enter Wu. Using super-cooled radioactive cobalt, she devised a series of experiments that later proved this so-called fundamental law of science wrong. If the law of parity was true, the cobalt nuclei would break down and jettison the same number of electrons in symmetrical directions. After months of operating on only a few hours of sleep a night – she even cancelled a long-awaited return visit to China – Wu was able to prove that this wasn’t the case.
The explosive news landed Wu on the cover of the New York Times. “We learn one lesson,” she later said, “never accept any ‘self-evident’ principle.”
Lee and Yang were later awarded the Nobel Prize in Physics in 1954, but Wu’s efforts in proving their theory right went unacknowledged.
“Although I did not do research just for the prize, it still hurts me a lot that my work was overlooked for certain reasons,” she wrote to Jack Steinberger, a fellow physicist who steadfastly maintained that Wu should have shared in the Nobel triumph.
She was decorated with honours in every other way, including the National Medal of Science and the Wolf Prize in Physics (the latter is considered the second most prestigious award in the sciences, after the Nobel Prize). She even had an asteroid named after her in 1990. But as she told a biographer, the glory of scientific discovery was its own award.
“These are moments of exaltation and ecstasy,” she said of her findings about parity. “A glimpse of this wonder can be the reward of a lifetime.”
This is an extract from Forgotten Women: The Scientists by Zing Tsjeng. Published by Hachette Australia, RRP $27.99.
Related reading: This week in science history: Marie Curie dies