Stanisław Ulam

Stanislaw Ulam
Ulam's ID badge photo from Los Alamos.
Born	(1909-04-13)April 13, 1909 Lwów, Galicia (now Lviv, Ukraine)
Died	May 13, 1984(1984-05-13) (aged 75) Santa Fe, New Mexico
Alma mater	Lwów School of Mathematics
Known for	nuclear pulse propulsion Teller–Ulam design Manhattan Project Fermi–Pasta–Ulam experiment Fermi–Ulam model Borsuk-Ulam theorem Mazur–Ulam theorem Ulam spiral Ulam conjecture in (Number Theory) Ulam's Conjecture (in Graph theory) Ulam numbers
Scientific career
Fields	Mathematics
Institutions	Manhattan Project University of Wisconsin–Madison Los Alamos National Laboratory
Doctoral advisor	Dr. Stefan Banach

Stanislaw Marcin Ulam (April 13, 1909 – May 13, 1984) was an American mathematician of Polish-Jewish origin, who participated in the Manhattan Project and originated the Teller–Ulam design of thermonuclear weapons. He also invented nuclear pulse propulsion and developed a number of mathematical tools in number theory, set theory, ergodic theory and algebraic topology.

Biography

Stanislaw Ulam was born in Lwów (Ukrainian: Lviv ; German: Lemberg), Galicia to a wealthy Polish-Jewish banking and timber-processing family who were part of the large Jewish minority population of the city. Lwów (now Lviv, Ukraine) was then in the Austro-Hungarian Empire until 1918 when it became the Second Polish Republic (until the start of World War II).

His mentor in mathematics was Stefan Banach, a great Polish mathematician and one of the moving spirits of the Lwów School of Mathematics (and more broadly of the interwar Polish School of Mathematics). Ulam himself came to figure among the mathematicians of the Lwów School, playing a significant role in their meetings at the Scottish Café. In the 1950s he translated the group's famous "Scottish Book" into English and published it in the United States.

Migration to the United States

Ulam went to the United States in 1938 as a Harvard Junior Fellow. He visited Poland in summer 1939 and together with his brother, Adam, escaped from Poland on the eve of the Second World War; the rest of their family died in the Holocaust. When his fellowship was not renewed he served on the faculty of the University of Wisconsin–Madison (UW).

Manhattan Project

When a single neutron collides with a uranium nucleus, in nuclear fission experiments, the final products are fission fragments and "new" neutrons. If a target-mass of solid uranium is bombarded with neutrons those "new" neutrons might collide with other uranium nuclei and again cause those nuclei to fission. Ulam realized that, if the target-mass was sufficiently large, a chain reaction would occur and fission could be either continuous—or even more importantly it could increase exponentially.

Ulam's realization was the break-through. Once this concept existed the search for a successful implementation could be started and led to the "Maude project" in England and the "Manhattan project" in America. Key experimental issues were the determination of the cross-sections, for the various processes, and the determination of the average number of emitted neutrons in each fission.

While at the University of Wisconsin–Madison during the Second World War several of Ulam's colleagues and peers had disappeared from campus. Ulam's friend John von Neumann invited him to a secret project in New Mexico which Ulam researched by taking out a book on New Mexico from the university library. He found on the book's check-out card the names of all those who had successively disappeared from the campus at UW. Ulam then joined the Manhattan Project at Los Alamos.

While at Los Alamos he also suggested the Monte Carlo method for evaluating complicated mathematical integrals that arise in the theory of nuclear chain reactions (not knowing that Enrico Fermi and others had used a similar method earlier). This suggestion led to the more systematic development of Monte Carlo by Von Neumann, Nicholas Metropolis, and others.

Development of thermonuclear devices

Ulam, in collaboration with C.J. Everett who did the detailed calculations, showed Edward Teller's early model of the hydrogen bomb to be inadequate. Ulam then went on to suggest that all the H-bomb's components could be placed inside one casing. His idea was to put a fission bomb at one end, thermonuclear material at the other and use mechanical shock from the fission bomb to compress and detonate fusion fuel. This idea was probably an outcome of Ulam's initial ideas for 'staging' a conventional fission device where the neutron flux from one fission bomb would compress the fuel in another one—thus increasing its efficiency.

Teller–Ulam Design

Teller at first resisted this idea, then saw its merit and suggested the use of a plutonium "spark plug", located at the center of the fusion fuel, to initiate and enhance the fusion reaction. Teller also modified Ulam's idea of compression by realizing that radiation from the fission bomb would compress the thermonuclear fuel much more efficiently than mechanical shock. This design, called staged radiation implosion, has since been the standard method of creating H-bombs. Although this approach was long believed to have been worked out independently by Soviet physicist Andrei Sakharov, it is often referred to as the "Teller–Ulam design". Ulam and Teller jointly applied for a patent on the hydrogen bomb.

Nuclear pulse propulsion

Ulam also invented nuclear pulse propulsion and, at the end of his life, declared it the invention of which he was most proud.

Mathematics

He was an early proponent of using computers to perform "mathematical experiments." His most notable contribution here may have been his part in the Fermi–Pasta–Ulam experiments, an early numerical study of a dynamical system.

Another dynamical system he introduced is the well-known Fermi–Ulam model (FUM), that is a variant of Fermi's primary work on acceleration of cosmic rays, namely Fermi acceleration. FUM became over the years a prototype model for studying non-linear dynamics and coupled mappings.

In pure mathematics, he worked in set theory (including measurable cardinals and abstract measures), topology, ergodic theory, and other fields. After World War II he largely turned from rigorous pure mathematics to speculative work, posing problems and making conjectures often concerning the application of mathematics to physics and biology. His friend Gian-Carlo Rota ascribed this change to an attack of encephalitis in 1946 that Rota claimed changed Ulam's personality (though detail had never been Ulam's strong point). This suggestion is believed by many but rejected by Ulam's widow, Françoise, among others.

Singularity quote

Ulam was among the first to refer to the technological singularity—and possibly the originator of the metaphor itself—in May 1958, while referring to a conversation with John von Neumann:

One conversation centered on the ever accelerating progress of technology and changes in the mode of human life, which gives the appearance of approaching some essential singularity in the history of the race beyond which human affairs, as we know them, could not continue.

Post-Manhattan Project career

Ulam took a position at the University of Colorado in 1965. As he remained a consultant at Los Alamos, he divided his time between Boulder, Colorado, USA and Santa Fe, New Mexico, from which he commuted to Los Alamos. Later he and his wife spent winters in Gainesville, Florida, where he had a position with the University of Florida. He died in Santa Fe on May 13, 1984.

Bethe on Ulam

• "After the H-bomb was made, reporters started to call Teller the father of the H-bomb. For the sake of history, I think it is more precise to say that Ulam is the father, because he provided the seed, and Teller is the mother, because he remained with the child. As for me, I guess I am the midwife." (Hans Bethe, 1968, as quoted by Schweber, p. 166.)

See also

• Borsuk-Ulam theorem
• Mazur–Ulam theorem
• Fermi–Ulam model
• Lucky number (1955)
• Ulam spiral (1963)
• Ulam conjecture (in Number Theory)
• Ulam's Conjecture (in Graph theory) aka the Reconstruction conjecture
• Ulam's game
• Ulam numbers
• Scottish Café
• Adam Ulam, Stanislaw's brother, a noted Kremlinologist at Harvard University
• The Day After Trinity (1980)

Books

• Stanisław Ulam, The Scottish Book: a Collection of Problems, Los Alamos, 1957.
• Stanisław Ulam, A Collection of Mathematical Problems, New York, Interscience Publishers, 1960.
• Mark Kac and Stanisław Ulam, Mathematics and Logic: Retrospect and Prospects, New York, Praeger, 1968. Dover paperback reprint edition ca. 1990.
• Stanisław Ulam, Sets, Numbers and Universes, Cambridge, Massachusetts, 1974.
• Stanisław Ulam, Adventures of a Mathematician, New York, Charles Scribner's Sons, 1983 (autobiography).
• Stanisław Ulam, Analogies Between Analogies: The Mathematical Reports of S.M. Ulam and his Los Alamos Collaborators. Berkeley: University of California Press, 1990 [1].

Further reading

• Necia Grant Cooper, Roger Eckhardt, Nancy Shera, editors, From Cardinals to Chaos, Cambridge University Press (1989). Reminiscences by people close to Ulam, memorial articles on aspects of his work, and previously unpublished informal work by him.

External links

• O'Connor, John J.; Robertson, Edmund F., "Stanisław Ulam", MacTutor History of Mathematics Archive, University of St Andrews
• Annotated bibliography for Stanislaw Ulam from the Alsos Digital Library for Nuclear Issues
• A biographical article on Ulam by Gian-Carlo Rota
• Stanisław Ulam at the Mathematics Genealogy Project
• Ulam Quarterly Journal ISSN 1071-7021
• Stan Ulam's Biography – from LANL
• Stanislaw Ulam’s Contributions to Theoretical Theory in Letters in Mathematical Physics, 1985. Ulam's contributions to theoretical biology are reviewed in terms of his work in cellular automata theory, population biology, Fermi-Pasta-Ulam results, pattern recognition, and biometric spaces.