💡 Feynman Diagrams

What This Simulation Shows

Feynman diagrams are pictorial representations of mathematical expressions describing the behaviour of subatomic particles. Each diagram represents a term in a perturbation series expansion of the interaction amplitude. The lines represent particle propagators, and the dots (vertices) represent interaction terms — in QED, each vertex contributes a factor of the coupling constant α ≈ 1/137.

How to Use

• Select an interaction from the list to see that diagram animated.
• Watch how particles move from the initial state (left/bottom) through interaction vertices to the final state (right/top).
• The wavy line represents a photon or virtual photon — virtual particles carry energy and momentum but are not directly observed.
• Adjust speed or restart to replay the animation.

Did You Know?

Richard Feynman invented these diagrams in 1948 as a bookkeeping tool for calculating scattering amplitudes in quantum electrodynamics. Each additional vertex in the diagram adds a factor of α ≈ 1/137 ≈ 0.007, making higher-order diagrams progressively smaller contributions — this is why QED predictions match experiment to better than 1 part in 10¹⁰, the most precisely tested theory in all of science.