Stanislaw Marcin Ulam ([stä'?iswäf 'märt??in 'uläm]; 13 April 1909 – 13 May 1984) was a Polish scientist in the fields of mathematics and nuclear physics.
He participated in the Manhattan Project, originated the Teller–Ulam design of thermonuclear weapons, discovered the concept of cellular automaton, invented the Monte Carlo method of computation, and suggested nuclear pulse propulsion.
In pure and applied mathematics, he proved some theorems and proposed several conjectures.
Born into a wealthy Polish Jewish family, Ulam studied mathematics at the Lwów Polytechnic Institute, where he earned his PhD in 1933 under the supervision of Kazimierz Kuratowski.
In 1935, John von Neumann, whom Ulam had met in Warsaw, invited him to come to the Institute for Advanced Study in Princeton, New Jersey, for a few months.
From 1936 to 1939, he spent summers in Poland and academic years at Harvard University in Cambridge, Massachusetts, where he worked to establish important results regarding ergodic theory.
On 20 August 1939, he sailed for the United States for the last time with his 17-year-old brother Adam Ulam.
He became an assistant professor at the University of Wisconsin–Madison in 1940, and a United States citizen in 1941.
In October 1943, he received an invitation from Hans Bethe to join the Manhattan Project at the secret Los Alamos Laboratory in New Mexico.
There, he worked on the hydrodynamic calculations to predict the behavior of the explosive lenses that were needed by an implosion-type weapon.
He was assigned to Edward Teller's group, where he worked on Teller's "Super" bomb for Teller and Enrico Fermi.
After the war he left to become an associate professor at the University of Southern California, but returned to Los Alamos in 1946 to work on thermonuclear weapons.
With the aid of a cadre of female "computers", including his wife Françoise Aron Ulam, he found that Teller's "Super" design was unworkable.
In January 1951, Ulam and Teller came up with the Teller–Ulam design, which is the basis for all thermonuclear weapons.
Ulam considered the problem of nuclear propulsion of rockets, which was pursued by Project Rover, and proposed, as an alternative to Rover's nuclear thermal rocket, to harness small nuclear explosions for propulsion, which became Project Orion.
With Fermi, John Pasta, and Mary Tsingou, Ulam studied the Fermi–Pasta–Ulam–Tsingou problem, which became the inspiration for the field of non-linear science.
He is probably best known for realising that electronic computers made it practical to apply statistical methods to functions without known solutions, and as computers have developed, the Monte Carlo method has become a common and standard approach to many problems.