Tony Rothman

“In any case, the theory of Brownian motion was independently developed in 1900 by a Frenchman, Louis Bachelier. Bachelier was not actually concerned with the motion of microscopic particles suspended in a liquid. He was concerned with prices on the French stock market. Prices on the Bourse, like particles in a liquid, are subject to a vast array of random forces, so many that the prices’ behavior can only be studied probabilistically. This is exactly what Bachelier did in his remarkable doctoral thesis, “The Theory of Speculation.” Yet although his paper is couched in terms of futures and stock options and “call-o-more’s” (whatever those are), the mathematics is identical to that of Brownian motion, and Bachelier’s equation explaining the drift of prices with time is the same as the one Einstein later derived for the position of particles. In his paper Bachelier anticipated the Black-Scholes approach to options trading, and for his prescient work he has in recent years been crowned the “father of economic modeling.” At the time, though, Bachelier seems to have been ignored, and he passed into obscurity. Could Einstein have known of his predecessor’s work and merely transplanted the mathematics to particles? I am aware of no evidence that this is the case.”
― Tony Rothman, Everything's Relative: And Other Fables from Science and Technology