CONCEPT
The Feynman Diagram
Richard Feynman's pictorial notation for particle interactions — a representational invention that changed physics by making the structure of quantum electrodynamics visible to human perception, admired by Tufte as a model of evidence design.
Before Feynman, quantum electrodynamics was calculated through pages of dense integral equations that obscured the physical process they described. A calculation predicting whether a photon would be absorbed or scattered by an electron required manipulating mathematical expressions so lengthy and abstract that even the physicists performing the calculations could lose sight of what was physically happening. Feynman's diagrammatic notation, introduced in the late 1940s, changed both the calculation and the understanding simultaneously. Each diagram represents a physical process: a line for a particle moving through space-time, a vertex for an interaction, a wavy line for a photon. The diagrams are rigorous — each element corresponds to a precise mathematical term — and they are also intuitive. A physicist looking at a Feynman diagram can see the physical process, see the electron moving, see the photon being emitted, see the interaction occurring at the vertex.
In The You On AI Field Guide
Tufte has admired Feynman's diagrams enough to include