Quantum Electrodynamics (QED) was an extraordinary success—but quickly ran into serious trouble. Shortly after Dirac formulated QED in the late 1920s, physicists realized that key calculations, like the electron’s self-energy, resulted in infinite values. Something fundamental seemed broken: how could a physical theory produce predictions that made no sense? 🔴 The 1940s brought a radical solution: renormalization. Feynman, Schwinger, and Tomonaga independently developed ways to systematically a