“The sudden liberation of our thinking on the very structure of the physical world was overwhelming.”
Chien-Shiung Wu (1912–97)
ScD 1982 (hon.)
In 1956 and early 1957, physicist C. S. Wu and her colleagues conducted an ingenious experiment showing that—at least in the case of radioactive decay—nature knows left from right. Wu’s work verified a hypothesis put forth in 1956 by her Columbia colleague Tsung-Dao Lee and Chen-Ning Yang that, unlike all other known physical forces, the "weak" interactions among decaying particles are not always symmetrical in nature. Before Wu’s measurements, the laws of physics had always shown complete symmetry between left and right—the world reflected in a mirror appeared no less possible than the world in front of it. As a result of her measurements, on the afternoon of January 15, 1957 the Department of Physics at Columbia University called a press conference to announce the dramatic overthrow of this basic law of physics, known as conservation of parity. The next day, The New York Times carried a front-page headline, “Basic Concept in Physics Reported Upset in Tests,” and the news quickly spread.