Los Alamos, New Mexico, USA. The first Monte Carlo simulation, running on the ENIAC computer and begun on April 28, is completed. The Monte Carlo method was devised by John von Neumann and Stanislaw Ulam to solve otherwise intractable problems (or problems difficult to solve in a timely manner) using the laws of chance. A first use case is the diffusion of neutrons inside a nuclear device. A complex situation can therefore be made tractable with a model run repeatedly to arrive at the most probable result. The Monte Carlo method made it possible to simulate nuclear chain reactions. In March 1947, von Neumann sent an 11-page letter to Robert Richtmyer, head of the Los Alamos theoretical division, asking him to run the Monte Carlo method on his electronic computer to simulate nuclear reactions in an atomic bomb. The first Monte Carlo simulation began at Los Alamos on April 28, 1948, using the ENIAC computer and concluded on May 10 with the creation of 25,000 punched cards. The program was written by Klari (Klara Dan), John von Neumann’s wife.
