Stanisław Ulam

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Stanisław Ulam
University of Colorado
University of Florida
Doctoral advisorKazimierz Kuratowski
Włodzimierz Stożek
Doctoral studentsPaul Kelly

Stanisław Marcin Ulam ([sta'ɲiswaf 'mart͡ɕin 'ulam]; 13 April 1909 – 13 May 1984) was a Polish Jewish mathematician, nuclear physicist and computer scientist. He participated in the Manhattan Project, originated the Teller–Ulam design of thermonuclear weapons, discovered the concept of the 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

PhD in 1933 under the supervision of Kazimierz Kuratowski and Włodzimierz Stożek.[1] 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

Teller–Ulam design
, which became 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 nonlinear science. He is probably best known for realizing 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.

Poland

Ulam was born in

Austrian partition. In 1918, it became part of the newly restored Poland, the Second Polish Republic, and the city took its Polish name again, Lwów.[5]

The Ulams were a wealthy

Polish Jewish family of bankers, industrialists, and other professionals. Ulam's immediate family was "well-to-do but hardly rich".[6] His father, Józef Ulam, was born in Lwów and was a lawyer,[5] and his mother, Anna (née Auerbach), was born in Stryj.[7] His uncle, Michał Ulam, was an architect, building contractor, and lumber industrialist.[8] From 1916 until 1918, Józef's family lived temporarily in Vienna.[9] After they returned, Lwów became the epicenter of the Polish–Ukrainian War, during which the city experienced a Ukrainian siege.[5]

Picture of the building that used to house the Scottish Café
The Scottish Café's building in Lviv, Ukraine now houses the Szkocka Restaurant & Bar (named for the original Scottish Café).

In 1919, Ulam entered Lwów Gymnasium Nr. VII, from which he graduated in 1927.

Wilno (Vilnius), Vienna, Zürich, Paris, and Cambridge, England, where he met G. H. Hardy and Subrahmanyan Chandrasekhar.[12]

Along with Stanisław Mazur, Mark Kac, Włodzimierz Stożek, Kuratowski, and others, Ulam was a member of the Lwów School of Mathematics. Its founders were Hugo Steinhaus and Stefan Banach, who were professors at the Jan Kazimierz University. Mathematicians of this "school" met for long hours at the Scottish Café, where the problems they discussed were collected in the Scottish Book, a thick notebook provided by Banach's wife. Ulam was a major contributor to the book. Of the 193 problems recorded between 1935 and 1941, he contributed 40 problems as a single author, another 11 with Banach and Mazur, and an additional 15 with others. In 1957, he received from Steinhaus a copy of the book, which had survived the war, and translated it into English.[13] In 1981, Ulam's friend R. Daniel Mauldin published an expanded and annotated version.[14]

Move to the United States

In 1935,

G. D. Birkhoff, who suggested that he apply for a position with the Harvard Society of Fellows.[9] Following up on Birkhoff's suggestion, Ulam spent summers in Poland and academic years at Harvard University in Cambridge, Massachusetts from 1936 to 1939, where he worked with John C. Oxtoby to establish results regarding ergodic theory. These appeared in Annals of Mathematics in 1941.[10][15]
In 1938, Stanislaw's mother Anna Hanna Ulam (née Auerbach) died of cancer.

On 20 August 1939, in

lice at Rudolf Weigl's typhus research institute. In 1963, Adam Ulam, who had become an eminent kremlinologist at Harvard,[16] received a letter from George Volsky,[17] who hid in Józef Ulam's house after deserting from the Polish army. This reminiscence gave a chilling account of Lwów's chaotic scenes in late 1939.[18] In later life Ulam described himself as "an agnostic. Sometimes I muse deeply on the forces that are for me invisible. When I am almost close to the idea of God, I feel immediately estranged by the horrors of this world, which he seems to tolerate".[19]

In 1940, after being recommended by Birkhoff, Ulam became an assistant professor at the

United States citizen in 1941.[9] That year, he married Françoise Aron.[10] She had been a French exchange student at Mount Holyoke College, whom he met in Cambridge. They had one daughter, Claire. In Madison, Ulam met his friend and colleague C. J. Everett, with whom he collaborated on a number of papers.[20]

Manhattan Project

A mug shot style ID photo, with the serial H 0
Ulam's ID badge photo from Los Alamos National Laboratory

In early 1943, Ulam asked von Neumann to find him a war job. In October, he received an invitation to join an unidentified project near

Robert Oppenheimer, its scientific director.[21] Knowing nothing of the area, he borrowed a New Mexico guide book. On the checkout card, he found the names of his Wisconsin colleagues, Joan Hinton, David Frisch, and Joseph McKibben, all of whom had mysteriously disappeared.[9] This was Ulam's introduction to the Manhattan Project, which was the US's wartime effort to create the atomic bomb.[22]

Hydrodynamical calculations of implosion

A few weeks after Ulam reached

fissile material suitable for use in bombs. To respond, Oppenheimer implemented, in August, a sweeping reorganization of the laboratory to focus on development of an implosion-type weapon and appointed George Kistiakowsky head of the implosion department. He was a professor at Harvard and an expert on precise use of explosives.[23]

The basic concept of implosion is to use chemical explosives to crush a chunk of fissile material into a critical mass, where neutron multiplication leads to a nuclear chain reaction, releasing a large amount of energy. Cylindrical implosive configurations had been studied by Seth Neddermeyer, but von Neumann, who had experience with shaped charges used in armor-piercing ammunition, was a vocal advocate of spherical implosion driven by explosive lenses. He realized that the symmetry and speed with which implosion compressed the plutonium were critical issues,[23] and enlisted Ulam to help design lens configurations that would provide nearly spherical implosion. Within an implosion, because of enormous pressures and high temperatures, solid materials behave much like fluids. This meant that hydrodynamical calculations were needed to predict and minimize asymmetries that would spoil a nuclear detonation. Of these calculations, Ulam said:

The hydrodynamical problem was simply stated, but very difficult to calculate – not only in detail, but even in order of magnitude. In this discussion, I stressed pure pragmatism and the necessity to get a heuristic survey of the problem by simple-minded brute force, rather than by massive numerical work.[9]

Nevertheless, with the primitive facilities available at the time, Ulam and von Neumann did carry out numerical computations that led to a satisfactory design. This motivated their advocacy of a powerful computational capability at Los Alamos, which began during the war years,

Otto Frisch remembered Ulam as "a brilliant Polish topologist with a charming French wife. At once he told me that he was a pure mathematician who had sunk so low that his latest paper actually contained numbers with decimal points!"[26]

Statistics of branching and multiplicative processes

Even the inherent statistical fluctuations of neutron multiplication within a chain reaction have implications with regard to implosion speed and symmetry. In November 1944, David Hawkins[27] and Ulam addressed this problem in a report entitled "Theory of Multiplicative Processes".[28] This report, which invokes probability-generating functions, is also an early entry in the extensive literature on statistics of branching and multiplicative processes. In 1948, its scope was extended by Ulam and Everett.[29]

Early in the Manhattan project,

Teller's "Super" bomb group, of which Ulam was a part, was transferred to a new division headed by Fermi.[31] Fermi and Ulam formed a relationship that became very fruitful after the war.[32]

Post war Los Alamos

In September 1945, Ulam left Los Alamos to become an associate professor at the

Los Angeles. In January 1946, he suffered an acute attack of encephalitis, which put his life in danger, but which was alleviated by emergency brain surgery. During his recuperation, many friends visited, including Nicholas Metropolis from Los Alamos and the famous mathematician Paul Erdős,[33] who remarked: "Stan, you are just like before."[9] This was encouraging, because Ulam was concerned about the state of his mental faculties, for he had lost the ability to speak during the crisis. Another friend, Gian-Carlo Rota, asserted in a 1987 article that the attack changed Ulam's personality: afterwards, he turned from rigorous pure mathematics to more speculative conjectures concerning the application of mathematics to physics and biology; Rota also cites Ulam's former collaborator Paul Stein as noting that Ulam was sloppier in his clothing afterwards, and John Oxtoby as noting that Ulam before the encephalitis could work for hours on end doing calculations, while when Rota worked with him, was reluctant to solve even a quadratic equation.[34] This assertion was not accepted by Françoise Aron Ulam.[35]

By late April 1946, Ulam had recovered enough to attend a secret conference at Los Alamos to discuss thermonuclear weapons. Those in attendance included Ulam, von Neumann, Metropolis, Teller, Stan Frankel, and others. Throughout his participation in the Manhattan Project, Teller's efforts had been directed toward the development of a "super" weapon based on nuclear fusion, rather than toward development of a practical fission bomb. After extensive discussion, the participants reached a consensus that his ideas were worthy of further exploration. A few weeks later, Ulam received an offer of a position at Los Alamos from Metropolis and Robert D. Richtmyer, the new head of its theoretical division, at a higher salary, and the Ulams returned to Los Alamos.[36]

Monte Carlo method

A smiling balding man in a suit and tie holds a strange device that looks like a frame
Stan Ulam holding the FERMIAC

Late in the war, under the sponsorship of von Neumann, Frankel and Metropolis began to carry out calculations on the first general-purpose electronic computer, the ENIAC at the Aberdeen Proving Ground in Maryland. Shortly after returning to Los Alamos, Ulam participated in a review of results from these calculations.[37] Earlier, while playing solitaire during his recovery from surgery, Ulam had thought about playing hundreds of games to estimate statistically the probability of a successful outcome.[38] With ENIAC in mind, he realized that the availability of computers made such statistical methods very practical. John von Neumann immediately saw the significance of this insight. In March 1947 he proposed a statistical approach to the problem of neutron diffusion in fissionable material.[39] Because Ulam had often mentioned his uncle, Michał Ulam, "who just had to go to Monte Carlo" to gamble, Metropolis dubbed the statistical approach "The Monte Carlo method".[37] Metropolis and Ulam published the first unclassified paper on the Monte Carlo method in 1949.[40]

Fermi, learning of Ulam's breakthrough, devised an

Monte Carlo trolley, later dubbed the FERMIAC. The device performed a mechanical simulation of random diffusion of neutrons. As computers improved in speed and programmability, these methods became more useful. In particular, many Monte Carlo calculations carried out on modern massively parallel supercomputers are embarrassingly parallel applications, whose results can be very accurate.[25]

Teller–Ulam design

On 29 August 1949, the Soviet Union tested its first fission bomb, the RDS-1. Created under the supervision of Lavrentiy Beria, who sought to duplicate the US effort, this weapon was nearly identical to Fat Man, for its design was based on information provided by spies Klaus Fuchs, Theodore Hall, and David Greenglass. In response, on 31 January 1950, President Harry S. Truman announced a crash program to develop a fusion bomb.[41]

To advocate an aggressive development program, Ernest Lawrence and Luis Alvarez came to Los Alamos, where they conferred with Norris Bradbury, the laboratory director, and with George Gamow, Edward Teller, and Ulam. Soon, these three became members of a short-lived committee appointed by Bradbury to study the problem, with Teller as chairman.[9] At this time, research on the use of a fission weapon to create a fusion reaction had been ongoing since 1942, but the design was still essentially the one originally proposed by Teller. His concept was to put tritium and/or deuterium in close proximity to a fission bomb, with the hope that the heat and intense flux of neutrons released when the bomb exploded, would ignite a self-sustaining fusion reaction. Reactions of these isotopes of hydrogen are of interest because the energy per unit mass of fuel released by their fusion is much larger than that from fission of heavy nuclei.[42]

A mushroom cloud lights up the dawn sky
Ivy Mike, the first full test of the Teller–Ulam design (a staged fusion bomb), with a yield of 10.4 megatons on 1 November 1952

Because the results of calculations based on Teller's concept were discouraging, many scientists believed it

computers" who carried out laborious and extensive computations of thermonuclear scenarios on mechanical calculators, supplemented and confirmed by Everett's slide rule. Ulam and Fermi collaborated on further analysis of these scenarios. The results showed that, in workable configurations, a thermonuclear reaction would not ignite, and if ignited, it would not be self-sustaining. Ulam had used his expertise in combinatorics to analyze the chain reaction in deuterium, which was much more complicated than the ones in uranium and plutonium, and he concluded that no self-sustaining chain reaction would take place at the (low) densities that Teller was considering.[45] In late 1950, these conclusions were confirmed by von Neumann's results.[35][46]

In January 1951, Ulam had another idea: to channel the mechanical shock of a nuclear explosion so as to compress the fusion fuel. On the recommendation of his wife,

Teller–Ulam design".[50]

Teller-Ulam
principles of staged radiation implosion.

In September 1951, after a series of differences with Bradbury and other scientists, Teller resigned from Los Alamos, and returned to the University of Chicago.[51] At about the same time, Ulam went on leave as a visiting professor at Harvard for a semester.[52] Although Teller and Ulam submitted a joint report on their design[48] and jointly applied for a patent on it,[22] they soon became involved in a dispute over who deserved credit.[47] After the war, Bethe returned to Cornell University, but he was deeply involved in the development of thermonuclear weapons as a consultant. In 1954, he wrote an article on the history of the H-bomb,[53] which presents his opinion that both men contributed very significantly to the breakthrough. This balanced view is shared by others who were involved, including Mark and Fermi, but Teller persistently attempted to downplay Ulam's role.[54] "After the H-bomb was made," Bethe recalled, "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."[55]

With the basic fusion reactions confirmed, and with a feasible design in hand, there was nothing to prevent Los Alamos from testing a thermonuclear device. On 1 November 1952, the first thermonuclear explosion occurred when Ivy Mike was detonated on Enewetak Atoll, within the US Pacific Proving Grounds. This device, which used liquid deuterium as its fusion fuel, was immense and utterly unusable as a weapon. Nevertheless, its success validated the Teller–Ulam design, and stimulated intensive development of practical weapons.[52]

Fermi–Pasta–Ulam–Tsingou problem

Main article: Fermi–Pasta–Ulam–Tsingou problem

When Ulam returned to Los Alamos, his attention turned away from weapon design and toward the use of computers to investigate problems in physics and mathematics. With John Pasta, who helped Metropolis to bring MANIAC on line in March 1952, he explored these ideas in a report "Heuristic Studies in Problems of Mathematical Physics on High Speed Computing Machines", which was submitted on 9 June 1953. It treated several problems that cannot be addressed within the framework of traditional analytic methods: billowing of fluids, rotational motion in gravitating systems, magnetic lines of force, and hydrodynamic instabilities.[56]

Soon, Pasta and Ulam became experienced with electronic computation on MANIAC, and by this time, Enrico Fermi had settled into a routine of spending academic years at the University of Chicago and summers at Los Alamos. During these summer visits, Pasta, Ulam, and Mary Tsingou, a programmer in the MANIAC group, joined him to study a variation of the classic problem of a string of masses held together by springs that exert forces linearly proportional to their displacement from equilibrium.[57] Fermi proposed to add to this force a nonlinear component, which could be chosen to be proportional to either the square or cube of the displacement, or to a more complicated "broken linear" function. This addition is the key element of the Fermi–Pasta–Ulam–Tsingou problem, which is often designated by the abbreviation FPUT.[58][59]

A classical spring system can be described in terms of vibrational modes, which are analogous to the harmonics that occur on a stretched violin string. If the system starts in a particular mode, vibrations in other modes do not develop. With the nonlinear component, Fermi expected energy in one mode to transfer gradually to other modes, and eventually, to be distributed equally among all modes. This is roughly what began to happen shortly after the system was initialized with all its energy in the lowest mode, but much later, essentially all the energy periodically reappeared in the lowest mode.

partial differential equations that have soliton solutions. This means that FPUT behavior can be understood in terms of solitons.[60]

Nuclear propulsion

A painting of a spacecraft passing a Jupiter-like planet
An artist's conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion

Starting in 1955, Ulam and

John O. Pastore at a congressional committee hearing on "Outer Space Propulsion by Nuclear Energy", on January 22, 1958, Ulam replied that "the future as a whole of mankind is to some extent involved inexorably now with going outside the globe."[63]

Ulam and C. J. Everett also proposed, in contrast to Rover's continuous heating of rocket exhaust, to harness small nuclear explosions for propulsion.[64] Project Orion was a study of this idea. It began in 1958 and ended in 1965, after the Partial Nuclear Test Ban Treaty of 1963 banned nuclear weapons tests in the atmosphere and in space.[65] Work on this project was spearheaded by physicist Freeman Dyson, who commented on the decision to end Orion in his article, "Death of a Project".[66]

Bradbury appointed Ulam and

John H. Manley as research advisors to the laboratory director in 1957. These newly created positions were on the same administrative level as division leaders, and Ulam held his until he retired from Los Alamos. In this capacity, he was able to influence and guide programs in many divisions: theoretical, physics, chemistry, metallurgy, weapons, health, Rover, and others.[62]

In addition to these activities, Ulam continued to publish technical reports and research papers. One of these introduced the

chaotic behavior".[68][69]

Return to academia

A lot of dots, but forming diagonal lines
When the positive integers are arrayed along the Ulam spiral, prime numbers, represented by dots, tend to collect along diagonal lines.

During his years at Los Alamos, Ulam was a visiting professor at Harvard from 1951 to 1952,

University of Colorado at Boulder from 1961 to 1962 and 1965 to 1967. In 1967, the last of these positions became permanent, when Ulam was appointed Professor and Chairman of the Department of Mathematics at the University of Colorado. He kept a residence in Santa Fe, which made it convenient to spend summers at Los Alamos as a consultant.[70] He was an elected member of the American Academy of Arts and Sciences, the United States National Academy of Sciences, and the American Philosophical Society.[71][72][73]

In Colorado, where he rejoined his friends Gamow, Richtmyer, and Hawkins, Ulam's research interests turned toward biology. In 1968, recognizing this emphasis, the University of Colorado School of Medicine appointed Ulam as Professor of Biomathematics, and he held this position until his death. With his Los Alamos colleague Robert Schrandt he published a report, "Some Elementary Attempts at Numerical Modeling of Problems Concerning Rates of Evolutionary Processes", which applied his earlier ideas on branching processes to evolution.[74] Another, report, with William Beyer, Temple F. Smith, and M. L. Stein, titled "Metrics in Biology", introduced new ideas about numerical taxonomy and evolutionary distances.[75]

When he retired from Colorado in 1975, Ulam began to spend winter semesters at the University of Florida, where he was a graduate research professor. In 1976, he was awarded the Commander's Cross with the Star of the Order of Polonia Restituta by the Polish government-in-exile in London.[76] Except for sabbaticals at the University of California, Davis from 1982 to 1983, and at Rockefeller University from 1980 to 1984,[70] this pattern of spending summers in Colorado and Los Alamos and winters in Florida continued until Ulam died of an apparent heart attack in Santa Fe on 13 May 1984.[3] Paul Erdős noted that "he died suddenly of heart failure, without fear or pain, while he could still prove and conjecture."[33] In 1987, Françoise Ulam deposited his papers with the American Philosophical Society Library in Philadelphia.[77] She continued to live in Santa Fe until she died in 2011, at the age of 93. Both Françoise and her husband were buried with her family in Montparnasse Cemetery in Paris.[78][79]

Challenge to economics

Alfred Marshall and his disciples dominated economic theory until the end of WWII. With the Cold War, the theory changed, emphasizing that a market economy was superior and the only sensible way. In Paul Samuelson's "Economics: An Introductory Analysis", 1948, Adam Smith's "invisible hand" was only a footnote. In later editions, it became the central theme. As Samuelson remembers, all this was challenged by Stanislaw Ulam:

[Y]ears ago... I was in the Society of Fellows at Harvard along with the mathematician Stanislaw Ulam. Ulam, who was to become an originator of the Monte Carlo method and co-discoverer of the hydrogen-bomb,... used to tease me by saying, 'Name me one proposition in all of the social sciences which is both true and non-trivial.' This was the test that I always failed. But now, some thirty years later ... an appropriate answer occurs to me: The Ricardian theory of comparative advantage ... That it is logically true need not be argued before a mathematician; that it is not trivial is attested by the thousands of important and intelligent men who have never been able to grasp the doctrine for themselves or to believe it after it was explained to them.[80][81]

Impact and legacy

Ulam participated in the creation of a

Los Alamos Laboratory nuclear project. From the publication of his first paper as a student in 1929 until his death, Ulam was constantly writing on mathematics. The list of Ulam's publications includes more than 150 papers.[10] Topics represented by a significant number of papers are: set theory (including measurable cardinals and abstract measures), topology, functional analysis, transformation theory, ergodic theory, group theory, projective algebra, number theory, combinatorics, and graph theory.[82]

Notable results of this work are:

Ulam played pivotal role in the development of thermonuclear weapons. According to Françoise Ulam: "Stan would reassure me that, barring accidents, the H-bomb rendered nuclear war impossible."[35] In 1980, Ulam and his wife appeared in the television documentary The Day After Trinity.[83]

A square containing the numbers 1 to 120. Numbers are initially grey but go purple as they are eliminated; the lucky numbers then remain, and are highlighted in red.
An animation demonstrating the lucky number sieve. The numbers in red are lucky numbers.

The Monte Carlo method has become a ubiquitous and standard approach to computation, and the method has been applied to a vast number of scientific problems.[84] In addition to problems in physics and mathematics, the method has been applied to finance, social science,[85] environmental risk assessment,[86] linguistics,[87] radiation therapy,[88] and sports.[89]

The

solitons, and dynamical systems.[90] In 1980, Donald Kerr, laboratory director at Los Alamos, with the strong support of Ulam and Mark Kac,[91] founded the Center for Nonlinear Studies (CNLS).[92] In 1985, CNLS initiated the Stanislaw M. Ulam Distinguished Scholar program, which provides an annual award that enables a noted scientist to spend a year carrying out research at Los Alamos.[93]

The fiftieth anniversary of the original FPUT paper was the subject of the March 2005 issue of the journal Chaos,[94] and the topic of the 25th Annual International Conference of CNLS.[95] The University of Southern Mississippi and the University of Florida supported the Ulam Quarterly,[96] which was active from 1992 to 1996, and which was one of the first online mathematical journals.[97] Florida's Department of Mathematics has sponsored, since 1998, the annual Ulam Colloquium Lecture,[98] and in March 2009, the Ulam Centennial Conference.[99]

Ulam's work on non-

cellular automata theory, population biology, pattern recognition, and biometrics generally (David Sankoff, however, challenged conclusions of Walter by writing that Ulam had only modest influence on early development of sequence alignment methods.[101]). Colleagues noted that some of his greatest contributions were in clearly identifying problems to be solved and general techniques for solving them.[102]

In 1987, Los Alamos issued a special issue of its Science publication, which summarized his accomplishments,

Wisconsin, and Pittsburgh.[9]

In 2021, German film director Thorsten Klein made a film adaptation of the book Adventures of a Mathematician about Ulam's life.

Ulam is the grandfather of Rebecca Weiner, the New York Police Department’s deputy commissioner of intelligence and counterterrorism.[105][106]

Bibliography

See also

References

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External links

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