The Left Hand of Nature

For most of the history of physics, every law of nature seemed to work exactly the same in a mirror. Then, in the winter of 1956, Chien-Shiung Wu cooled a sample of cobalt-60 to a hundredth of a degree above absolute zero, watched which way its electrons flew, and showed that the weak force can tell left from right.

This video follows the idea from start to finish: what a mirror really does to physics, the puzzle that made two theorists ask whether anyone had checked, the experiment that settled it, and what it would take to send the meaning of "left" across the galaxy.

What it covers

1. What a mirror does: parity, axial vectors and pseudoscalars
2. The theta-tau puzzle, and Lee and Yang's question
3. Wu's cobalt-60 experiment
4. Helicity, and why neutrinos are left-handed
5. The pion's lopsided decay and V−A theory
6. CP violation in kaons
7. Electroweak theory and the precision tests of the 1970s
8. Martin Gardner's Ozma problem, and its loophole

Animated with Manim. The narration is a synthetic voice.

Watch on YouTube