TL;DR

Veritasium digs into how Paul Dirac’s quest to marry quantum mechanics with relativity led him to embrace “impossible” negative-energy solutions. By tweaking the Schrödinger and Klein–Gordon equations, Dirac stumbled on predictions of anti-electrons (positrons) and even a mirror “anti-universe” where particles effectively run time backwards.

Along the way you’ll meet the brilliant (if eccentric) Dirac, see why the old wave equations fell short, and learn how Heisenberg’s uncertainty principle and the famous Dirac equation together make sense of antimatter—even hinting at a cosmic world flipped in charge, parity, and time.

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