An Easy Intro to Feynman's QED, Part 2: Adding Alternative Histories - Livestream

In his February 21, 2026, talk, Terry discussed how Nobel Laureate Richard Feynman devised a radically new way to represent quantum mechanics mathematically by fully accepting both Einstein’s controversial insistence that photons must be localized particles of energy and that all wave-like behaviors of those particles are real and must also be explained using such particles. The result was a mathematically powerful and predictive theory that discarded the idea that a photon follows a single, unique path through space and time between emission and absorption, and replaces it with an infinitely detailed cloud of possible paths. The model then adds these alternative histories using simple rules to obtain a final prediction: an integral of all possible histories. In this Part 2 talk, I look at Feynman’s many specific examples of why his strange-sounding discarding of classical path concepts results in exquisite predictability of how photons actually travel.

Speaker: Terry Bollinger, computer scientist