Chien-Shiung Wu

Chien-Shiung Wu was an experimental physicist whose work focused on testing the deepest assumptions of nuclear science. Known for her technical precision, she specialized in designing laboratory experiments capable of verifying - or challenging - theoretical physics.

In the mid-20th century, the law of parity stood as one of physics’ most trusted principles. It held that physical processes behaved identically when spatial orientation was reversed - that the universe, at its most fundamental level, followed mirror symmetry.

Physicists Tsung-Dao Lee and Chen-Ning Yang began to question this assumption. The idea required experimental proof. Wu designed and led the test. Working with a team at the U.S. National Bureau of Standards, she cooled radioactive cobalt-60 nuclei to extremely low temperatures and aligned their spin using a magnetic field. By observing the direction of electrons emitted during radioactive decay, the experiment revealed a striking result: the decay behaved differently depending on orientation.

Parity was violated.

The discovery overturned one of physics’ most trusted laws and transformed the understanding of subatomic forces. Lee and Yang received the 1957 Nobel Prize in Physics for the theoretical prediction. Wu’s experimental proof - the work that turned theory into physical reality - was not included.

Her work demonstrated something fundamental about science itself: even the most established laws must answer to evidence.