The “One Electron” Hypothesis

 This is an anecdote about physicist John Archibald Wheeler and his student Richard Feynman.

The “One Electron” Hypothesis

One day, Wheeler is said to have told Feynman over the phone:
“Richard, there is really only one electron in existence.”

The bold idea suggested that this single electron moves back and forth through time, making it appear to us as the countless electrons we observe.

Background of the Idea

In the Feynman diagrams later developed by Feynman, an electron moving backward in time can be interpreted as a positron.
Thus, by regarding electrons and positrons as the same entity—an electron traveling both forward and backward in time—the symmetry between particles and antiparticles can be explained.

Feynman’s Reaction

Feynman found this idea fascinating, and it became one of the inspirations for a unified framework treating electrons and positrons in a consistent way.
Of course, physicists do not literally believe that there is only one electron; it was a playful, thought-experiment-like hypothesis with a touch of humor.

If you are interested, I can also explain how this “one-electron universe” hypothesis later connected to the development of quantum electrodynamics (QED) and the use of Feynman diagrams.