Every electron in the universe is perfectly identical. Swap any two and nothing changes. In 1940, John Wheeler called Richard Feynman with a wild explanation: maybe they're identical because there's only one electron, zigzagging back and forth through time. When it moves backward in time, we see it as a positron.
Richard Feynman explaining atoms and stars in this ‘Fun to Imagine’ BBC series, recorded at Feynman's home in Altadena, California, ca. 1983 🧠
-📹 BBC Archive