Seventy-Five Years of QED

Looking back from 2023 at the history of quantum physics through the traditional frame of quarter-century anniversaries, neither the 100th anniversary nor the 50th stand out as particularly prominent. 1923 was solidly in the "Old Quantum Theory" era, before Heisenberg's matrix mechanics and Schrödinger's wave equation, and by 1973 the theory had long since reached its full modern form. 2023 is, however, the 75th anniversary of a significant milestone: the 1948 Pocono Conference at which Julian Schwinger and Richard Feynman first presented their theories of quantum electrodynamics (QED), followed closely by the receipt of Sin-Itiro Tomonaga's independently developed version from Japan. This talk will look back at that moment in quantum history, and reflect on the rapidity of the development of quantum mechanics between 1923 and 1948.