Wu experiment

The Wu experiment was a particle and nuclear physics experiment conducted in 1956 by the Chinese American physicist Chien-Shiung Wu in collaboration with the Low Temperature Group of the US National Bureau of Standards. The experiment's purpose was to establish whether conservation of parity (P-conservation), which was previously established in the electromagnetic and strong interactions, also applied to weak interactions. If P-conservation was universal, a mirrored version of the world would behave identically to the mirror image of the current world. If P-conservation were violated, then it would be possible to distinguish between a mirrored version of the world and the mirror image of the current world (where left is mirrored to right and vice versa).

The experiment established that conservation of parity was violated (P-violation) by the weak interaction, thus providing a way to operationally define left and right. This result was not expected by the physics community, which had previously regarded parity as a symmetry that applied to all forces of nature. Tsung-Dao Lee and Chen-Ning Yang, the theoretical physicists who originated the idea of parity nonconservation and proposed the experiment, received the 1957 Nobel Prize in Physics for this result. While not awarded the Nobel Prize, Chien-Shiung Wu's role in the discovery was mentioned in the Nobel Prize acceptance speech of Yang and Lee, but she was not honored until 1978, when she was awarded the first Wolf Prize.