The value of Einstein’s mistakes

Steven Weinberg’s love for and knowledge of history inform his instructive sampling of Albert Einstein’s mistakes (Physics Today, November 2005, page 31 ). One mistake, or at least one tantalizing omission, seems worth adding to the collection. In a May 1905 letter to Conrad Habicht, Einstein wrote that he thought his revolutionary contribution was the hypothesis that light consists of particles. ¹

Consider his lifelong passion for unification, as in his resolution of the clash between Isaac Newton’s mechanics and James Clerk Maxwell’s electrodynamics (with the special theory of relativity modifying the former). It is hard to believe that Einstein did not worry about reconciling the well-established wave aspects of light with his new particle hypothesis. If he had pursued that connection, he could have developed one-photon quantum mechanics in 1905 or shortly afterward, by combining the Poynting-vector expression for the power intensity of light with his own relation between frequency and energy of a particle to obtain the photon-number intensity of a light beam. The wave equation is the Maxwell equations, and the probability interpretation pops up immediately.

Many observers have said that general relativity was one advance that would have taken a very long time without Einstein, but we have no direct test for that statement. However, if you accept my argument that Einstein could have developed the first true quantum mechanics, then we can say exactly how long it took the physics community to catch up—20 years for Heisenberg’s matrix mechanics and Schrödinger’s mathematically equivalent wave mechanics.