A woman who changed our world

Anniversary marks birth and celebrates achievements of physicist who was 'forever a Chinese', Yang Yang reports.

At the end of May, events were held both online and offline in Nanjing and Taicang, Jiangsu province, to honor the 110th anniversary of the birth of nuclear physicist Wu Chien-shiung. In mid-September, a global online symposium will be held also to mark this anniversary.

Compared with physicists such as Marie Curie or Richard Feynman, Wu is not a household name in China, where she was born and grew up, or in the United States, where she spent most of her life, but she was one of the most influential nuclear physicists of the 20th century, one that "radically" changed human's view of the universe.

Wu was born on May 31, 1912, in Liuhe town, Taicang, where the Yangtze River flows into the East Sea. It was a time when the feudal system in China, which spanned more than 2,000 years, came to an end and new thoughts rushed in as people sought to find ways to rejuvenate the country.

Wu's father, Wu Zhongyi, received a modern education in Shanghai, and in 1913, founded the first school for girls in Taicang. He aimed to break the old sexist advocacy that it was women's virtue to have no talents. Now, the school has become Mingde Senior Middle School.

The father, absorbing the merits of Western ideas while bearing the great thoughts rooted deep in Chinese culture in mind, exerted the most profound influence on Wu Chien-shiung's life.

She spent most of her life in the US, but always wore qipao, a traditional Chinese gown. Working in the scientific world dominated by men, she never gave up or lowered her standards even if unequally treated.

After graduating from the former National Central University in Nanjing in 1934, Wu enrolled at the University of California, Berkeley at the age of 24 to continue her study in physics.

During her 44-year career as a nuclear physicist, Wu's unprecedented achievements won her nicknames such as "Chinese Madame Curie", "queen of nuclear research "and "first lady of physics".

As the nickname indicates, Wu was "first" in many ways.

She was the first woman to be president of American Physical Society, the first female winner of the Comstock Prize in physics given by the US National Academy of Sciences, the first person to receive the Wolf Prize in physics, the first honorary doctorate awarded by Princeton University to a woman, and the first female professor of physics in the history of Columbia University.

Moreover, in 1990, the Purple Mountain Observatory of the Chinese Academy of Sciences in Nanjing named an asteroid after her (2752 Wu Chien-shiung).

Among her important contributions to physics, Wu was the first to confirm the theory of beta decay proposed by Enrico Fermi in 1933 about how radioactive atoms become more stable and less radioactive.

To get accurate results from experiments, she worked very hard day and night at a laboratory and gained a reputation for accuracy. There was a saying among physicists: If the experiment was done by Wu, it must be correct.

She was always cautious in experiments, spending a great deal of time calibrating instruments. She didn't start collecting data until she fully understood the instruments. Her experiments overturned many previous experimental results and theories, said Samuel Chao Chung Ting, American physicist and Nobel Prize winner, in a video for the anniversary events on May 31.

In 1956, theoretical physicists Tsung-dao Lee and C.N. Yang approached Wu to create an experiment to test their theory that questioned conservation of parity, a long-held foundational principle in quantum mechanics.

In an article Lee wrote for the anniversary events, he recalled that when he and Yang proposed the theory of parity non-conservation in weak interactions, "who should we invite to test it? I thought of Wu. She was one of the most authoritative scientists studying beta decay".

For this experiment, Wu did not hesitate to abandon a travel plan that was prearranged long ago.

At that time, almost all the scientists believed that the universe was symmetric. As a result, when Wu organized a team to test the theory in the summer of that year, her experiment became a source of derision among the big figures in physics, including Nobel Prize winners Wolfgang Pauli and Richard Feynman, Yang recalled in his article for the anniversary events.

However, Wu's ingeniously designed experiment showed that it was not the case. She observed in the decaying of the radioactive cobalt-60 that in weak interactions, parity was not conserved, which "radically changed our view of the universe", said Brian Greene, a professor of physics and mathematics at Columbia University, in a previous interview with CNN.

The next year, Lee and Yang won the Nobel Prize in physics for the theory.

"Why did Wu Chien-shiung have the courage to conduct an experiment that everyone regarded as hopeless? Was she hoping she might be lucky to discover that the left and the right (of the universe) were not symmetric? I don't think so! This was not her personhood or how she worked. Rather she thought whether cobalt-60 was symmetric was a foundational question, which was absolutely worth studying regardless of consequences! This was why she excelled," wrote Yang.

Despite her widely known achievements, she was not treated fairly due to gender inequality. She started working at Columbia University in 1944 but did not get the position of assistant professor until 1952. She was promoted to professor in 1958.

As a victim of gender inequality, in 1964, she asked her audience at a symposium at Massachusetts Institute of Technology "whether the tiny atoms and nuclei, or the mathematical symbols, or the DNA molecules have any preference for either masculine or feminine treatment".

On the International Day of Women and Girls in Science in 2021, the US Postal Service issued the Chien-shiung Wu "commemorative forever" stamp to honor her as "one of the most influential nuclear physicists of the 20th century".

She indeed had set a great model for women and girls to "see the limitlessness of life", and "what can be gained by pushing past the barriers around you", wrote Jada Yuan in an article when she recalled the time spent with Wu, her grandmother.

"She was fighting to be seen and respected at a time when women and Chinese people in America rarely were," Yuan wrote.

In 1973, Wu returned to China for the first time after departing the homeland 37 years previously. In the following years, she came back nine times, visiting her hometown, giving lectures and academic reports at universities about the latest scientific development.

In 1986, Wu set up a scholarship at Nanjing University (which developed from the National Central University) to reward students excelling in physics. In 1992, she established the Wu Chien-shiung Library in the school of physics there, which housed tens of thousands of academic books from around the world.

Wu lived a simple life, but she set up a funding program in homage to her father with her life savings, rewarding students and teachers at Mingde Senior Middle School, and donating money to build the school and buy computers.

On Feb 16, 1997, Wu died in the US. According to her will, she was buried in her hometown Taicang. Chiang Tsai-chien, the author of her biography, Madame Wu Chien-shiung: The First Lady of Physics Research, wrote the epitaph that starts, "Here's buried the most prominent female physicist Wu Chien-shiung", and ends, "she was a distinguished world citizen, and was forever a Chinese".

Contact the writer at yangyangs@chinadaily.com.cn