# Ulam, Stanislaw M. (Stanislaw Marcin), 1909-1985

## Biographical notes:

Stanislaw Ulam was gifted mathematician who, during the course of his career, made significant contributions to set theory, topology, ergodic theory, probability, cellular automata theory, the study of nonlinear processes, the function of real variables, mathematical logic, and number theory. Perhaps his greatest achievement was the development of the Monte Carlo method for solving complex mathematical problems by electronic random sampling, but he made equally noteworthy contributions in hydrodynamics (three-dimensional fluid flow), the development of nuclear propulsion for space flight (Project Orion), and in fields as disparate as physics, biology, and astronomy. Yet despite the breadth of his scholarship, Ulam is most often remembered for the central role he played in the early development of the American hydrogen bomb.

Stanislaw Marcin Ulam was born in Lwów, Poland on April 13, 1909. The son of Jozef Ulam, a lawyer, and Anna Auerbach, the daughter of an industrialist, Ulam developed an enthusiasm for astronomy and physics while still in his teens that led him into the serious study of mathematics. Enrolling at the Lwów Polytechnic Institute in 1927, he received his bachelor's (1931), master's (1932), and doctoral degrees in rapid succession (1933), intending on an academic career. Following receipt of his degree and a tour of Europe during which he visited mathematicians and scientists in Vienna, Zurich, Paris, and Cambridge, Ulam received an invitation from fellow mathematician, John von Neumann, to become a visiting scholar for three months at the Institute for Advanced Study in Princeton. There, he met G. D. Birkhoff, who brought him to Harvard to become one of the earliest members of the Society of Fellows (1936-1939) and later, lecturer (1940). During his five years in Cambridge, Ulam traveled back and forth between Poland and the States, and shortly after he suffered the death of his mother, his younger brother, Adam, was sent to join Stan in America. Adam was encouraged to enroll at Brown University, where Stanislaw was engaged in substitute teaching a graduate course on the theory of functions of several real variables.

In 1940, Ulam accepted a position as instructor at the University of Wisconsin, and quickly earned promotion to assistant professor. Both personally and professionally, his years in Wisconsin were eventful, beginning more than a decade of intense activity and life change. In an effort to enlist in the military in 1943, Ulam became a U.S. citizen, and in that same year, he married Françoise Aron, a French exchange student at Mount Holyoke College, whom he had met in Cambridge. The Ulams had one child, Claire, born in 1944. Although he taught mathematics courses to Army and Navy recruits, Ulam believed that he could contribute more directly and significantly to the war effort, and early in the autumn, 1943, John von Neumann again interceded in Ulam's life. Meeting furtively at a railroad station in Chicago, von Neumann convinced Ulam to join an unidentified, war-related project, and with the added urging of physicist Hans Bethe, Ulam agreed. Within a few months, he and his family moved to Los Alamos Scientific Laboratories (LASL), N.M., to begin work on the Manhattan Project.

Assigned to physicist Edward Teller's group, a unit of the scientific corps led by Enrico Fermi, Ulam set to work on the hydrodynamics of implosion, in preparation for construction of the atomic bomb. His key insight into the development of the fusion bomb may have been the recognition that compression of the nuclear material was necessary to produce an explosion, and that mechanical shock waves generated by a fission bomb could produce the force necessary. He later also struggled through the mathematical physics that set the stage for theoretical work in preparation of a "super" bomb - Teller's proposed thermonuclear hydrogen bomb. After this initial work on Teller's problem, Ulam co-authored a report on multiplicative branching processes with David Hawkins -- a philosopher and non-professional mathematician and physicist at Los Alamos -- and C. J. Everett, a professor from the University of Wisconsin. This important paper marked some of the earliest work in branching process theory, a sub-field of probability theory. Yet as often proved true in his life, his academic successes were accompanied by personal misfortunes. While Ulam contributed to the completion of work at LASL in 1945, he learned of the loss of his entire immediate family in Poland at the hands of the Nazis: his father, uncle, sister, and brother-in-law were killed. Only his brother Adam, who had matriculated at Brown University in 1940, survived.

With the war ended, Ulam hoped for a return to a more conventional academic career. Doubting his chances for promotion and tenure at Wisconsin, he accepted a teaching position at the University of Southern California during the fall, 1945. Shortly after his arrival in Los Angeles, however, he was struck by a mysterious illness -- later diagnosed as viral encephalitis - which was treated by a highly risky surgical procedure. Friends and colleagues noted that the illness and treatment seemed to affect Ulam's personality, and more profoundly, his approach to mathematical problem solving. After his recovery, they noted, he appeared to use his imagination more when searching for new mathematical ideas, and to rely less on his own technical solutions, and more on the hard work of others. The increasing fertility of his imagination was counterbalanced by a reluctance to delve into the technical details. Ulam's convalescence required a leave of absence from USC, during which he was invited to attend a secret conference at LASL in April, 1946, to discuss the development of Teller's thermonuclear bomb. Having played an important role in solving the technical problems associated with the development of the atomic bomb, he was asked to resume work at LASL on the development of the H-bomb. Associating Los Angeles with his illness, Ulam was willing to leave, and he once again resumed his work in the desert. While involved in research at LASL, he developed the Monte Carlo method, by which solutions to mathematical and physical problems are solved through random sampling. The Monte Carlo method became known as one of Ulam's most significant achievements, and he lectured on the subject frequently.

The reputation that surrounds Edward Teller and Ulam as "fathers of the hydrogen bomb" was solidified by their work during the early 1950s. In February, 1950, Ulam conclusively demonstrated that the amount of tritium Teller had estimated as necessary for his "classic super" design was insufficient, suggesting that only limited progress was possible within the parameters of the original super plan. Von Neumann confirmed Ulam's results through calculations run on the Princeton computer, one of the earliest electronic computing machines of its kind, and by April, 1950, Ulam had developed an alternative configuration, which he published jointly with Teller as a classified paper. Ulam's configuration proved to be a turning point in the development of the H-bomb, making possible the first thermonuclear reactions and the "Mike" test at Bikini Atoll in November, 1952.

After completing this phase of work at Los Alamos, Ulam was employed at Harvard, the Massachusetts Institute of Technology, and the University of California as a visiting professor from 1951-1956, before returning to LASL in 1957 to become research advisor to the director of the laboratory. He remained in that position until his retirement in 1965, though until his death in 1984, he continued to consult for Los Alamos. From 1965-1975, Ulam also held the chair of the mathematics department at the University of Colorado at Boulder, and for a portion of his tenure there, he was professor of biomathematics at the University of Colorado Medical School. Ulam continued to be actively involved in government science after the completion of his work on the H-bomb. His involvement with Project Rover at LASL resulted in the design of a nuclear-reactor rocket, while his work with Project Orion focused on the nuclear propulsion of a space vehicle. Under the Kennedy administration, he became involved in the nation's space program as a member to the President's Scientific Advisory Committee, the Air Force Space Planning Committee, and General Twining's Air Force Committee. He was also retained as a consultant by such companies as IBM, General Atomic, the North American Aviation Corporation, and Hycon Corporation, as well as the Neurosciences Institute of the Rockefeller University. Among Ulam's professional publications are several books and more than 150 articles in professional journals reflecting his diverse work in mathematics, theoretical physics, and mathematical biology. Among these are A collection of mathematical problems (N.Y., 1960), a collaboration with fellow mathematician Mark Kac entitled Mathematics and Logic (N.Y., 1968), Stanislaw Ulam: sets, numbers, universes (Cambridge, 1974), and his autobiography Adventures of a mathematician (N.Y., 1976). The Scottish book was finally edited by R. Daniel Mauldin and published in 1982 after Ulam had distributed typescripts of the notebook to colleagues in the scientific community as early as 1957. This collection of unsolved mathematical problems was initially compiled in the Scottish Cafe in Poland before World War II by Ulam and fellow mathematicians, including his former graduate advisor, Stefan Banach. Works in progress at the time of Ulam's death in 1984 included "Problem Book II," the second volume to his Collection of mathematical problems . These number and breadth of these publications underscore Ulam's influence on many branches of twentieth century mathematics, as well as his signature application of theoretical and technological research to the sciences.

Ulam's memberships in professional and learned societies included the National Academy of Sciences, the American Academy of Arts and Sciences, the American Philosophical Society, the American Physical Society, the American Mathematical Society, the Mathematical Association of America, the Polish Mathematical Society, and the American Association for the Advancement of Science. He was also asked to serve on the board of governors for the Weizmann Institute of Science in Rehovot, Israel, and the Jurzykowski Foundation in New York. Ulam was honored with such awards as the Sierpinski Medal, the Polish Millennium Prize, and the Polish American Congress Heritage Award, and was named the John von Neumann Lecturer of the Society of Applied and Industrial Mathematics. In recognition of his mathematical and scientific achievements, Ulam was awarded honorary degrees by the University of New Mexico (1965), the University of Pittsburgh (1978), and the University of Wisconsin (1978). Stanislaw Marcin Ulam died in Santa Fe, New Mexico, on May 13, 1984. He was seventy-five.

From the guide to the Stanislaw M. Ulam Papers, 1916-1984, (American Philosophical Society)

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#### Subjects:

- Atomic bomb