The most powerful formula in physics starts with a slender S, the symbol for a sort of sum known as an integral. Further along comes a second S, representing a quantity known as action. Together, ...

Mark Barrett correctly points out that in Richard Feynman's path-integral formulation of quantum mechanics, a particle is in a sense everywhere at once (Letters, 13 October). On the same page, Koos ...

Richard Phillips Feynman was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the ...