Princeton Portrait: Chien-Shiung Wu (1912–1997)

Illustration: Daniel Hertzberg

What distinguishes scientific genius from all other scientific thinking? When the physicist Galileo Galilei looked at a pendulum, he realized that, where his colleagues saw a weight that was trying to fall to the ground and a string preventing it from falling properly, he was looking at a weight that was trying to swing forever and a resisting force — friction — that dragged it to a stop. This way of understanding a pendulum’s movement opened up the discovery of new laws of motion. A scientific visionary is, in almost literal terms, a person who sees the world in a new way.

Genius can also consist of the ability to design clever experiments that make everyone see the world in a new way. This was the rare talent of Chien-Shiung Wu, a scientist famous, in the words of The New York Times, “as a meticulously accurate experimental physicist who was in demand to put new theories to the test.” Wu’s colleagues called her “the first lady of physics.” In February of this year, the United States issued a postage stamp honoring her.

Wu left China in 1934 to pursue a Ph.D. in the United States. She ditched the University of Michigan for the University of California, Berkeley, after she learned that Michigan forbade women from using the student union building. A decade later, she was teaching at Princeton University — the first female instructor in Princeton’s physics department — and working for the Manhattan Project at Columbia. After the war, she left Princeton and joined the faculty at Columbia.

Already, as a young researcher at Columbia, she was earning a reputation as a brilliant designer of experiments. When Enrico Fermi, a leader of the Manhattan Project, was trying to figure out why his uranium chain reactions kept breaking down, his colleagues told him, “Ask Miss Wu.” Wu explained: In Fermi’s tests, a gas was absorbing the neutrons that needed to penetrate the uranium atoms to keep the chain reaction going. She later ran an experiment that proved one of his theories, as he could not: Surmising that the original experiment failed because of the interference of a clumpy layer of copper sulfate, she mixed the sulfate with detergent to even it out. Wu once remarked, “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.” In this instance, she made the sink full of dishes pay off in the lab.

The universe is weird. For one thing, it’s left-handed. Wu proved this in 1957, after Tsung-Dao Lee, of Columbia, and Chen Ning Yang, of the Institute for Advanced Study, proposed that a basic law in physics — that atoms don’t distinguish between left and right — was mistaken. Wu worked up an experiment to test their thesis: By chilling radioactive cobalt to almost absolute zero, then running a magnetic field through it, she created a situation in which the cobalt atoms, if they treated direction as neutral, should throw off particles on all sides equally. They did not. Not only does the universe distinguish between left and right at the atomic level, but it favors the left. 

Lee and Yang won the 1957 Nobel Prize in Physics for the discovery. Historians argue that Wu should have received one, too. Wu was cavalier, telling the Times that year that she was already designing new projects: “These experiments are forgotten now. We’re looking ahead — that’s the excitement of basic research.” 

When she received an honorary doctorate from Princeton in 1958, President Robert Goheen ’40 *48 said, “Dr. Wu, renowned collaborator to Doctors Yang and Lee, has richly earned the right to be called the world’s foremost female experimental physicist. By her decisive demonstration that the law of the conservation of parity is no longer tenable, she has decisively reasserted the principle of intellectual parity between women and men.”

The difference between a crackpot theory and a breakthrough discovery is a successful experiment. In order to test unusual and hard-to-identify peculiarities of nature, Wu created new worlds in miniature. In so doing, she changed the world we inhabit.