The one-electron universe hypothesis proposes that all electrons and positrons are manifestations of a single entity moving backward and forward in time. It was proposed by theoretical physicist John Wheeler in a telephone call to Richard Feynman in the spring of 1940. A similar concept was independently developed by E.

C. G. Stueckelberg around the same time.

The idea suggests that the world lines of electrons form a single tangled knot in spacetime, with each moment in time intersecting this line many times—each intersection representing an electron or positron depending on the direction of time travel. Wheeler argued that backward-moving sections appear as positrons. Feynman later credited Wheeler with the insight that antiparticles could be represented by reversed world lines, calling it a key inspiration for his 1949 paper "Theory of Positrons" paper.

Yoichiro Nambu extended the idea to all particle-antiparticle pairs, framing creation and annihilation as mere changes in direction of motion through time.