Stanislaw Ulam

Stanislaw Ulam

Ulam's ID badge photo from Los Alamos
Born April 13, 1909(1909-04-13)
Lwów, Galicia (now Lviv, Ukraine)
Died May 13, 1984(1984-05-13) (aged 75)
Santa Fe, New Mexico
Fields Mathematics
Institutions Manhattan Project
University of Wisconsin–Madison
Los Alamos National Laboratory
University of Florida
Alma mater Lwów School of Mathematics
Doctoral advisor Kazimierz Kuratowski
Włodzimierz Stożek
Doctoral students George Estabrook
Leonard Gallagher
Edward Howorka
Celestino Mendez
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

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.

Contents

Biography

Stanislaw Ulam was born in Lwów (Ukrainian: Lviv ; German: Lemberg), Galicia to a wealthy Polish-Jewish banking and timber-processing family[1] who were part of the large Jewish minority population of the city. Lwów (now Lviv, Ukraine) was then in the Austro-Hungarian Empire; from 1918 until 1939 it was in the Second Polish Republic,

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.[2]

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[3] 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

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

References

  1. ↑ Anxiously from Lwów: Family Letters to Stanislaw M. Ulam A website dedicated to the Ulam family, part of which perished in the holocaust.
  2. ↑ Matematyk z bombą, Rzeczpospolita, 21 May 2009
  3. ↑ Ulam, S., Tribute to John von Neumann, Bulletin of the American Mathematical Society, vol 64, nr 3, part 2, May, 1958, p1-49.

Further reading

External links