Freeman J. Dyson, theoretical physicist and writer, who embraced the stunning diversity of the universe with unique spirit, died on February 28, 2020 in a hospital near Princeton, NJ at the age of 96.

Dyson generated revolutionary scientific insights, including calculations bridging the quantum and human worlds. His contributions stem from his work in numerous areas, including nuclear engineering, solid state physics, ferromagnetism, astrophysics, biology, and applied mathematics.

The Institute for Advanced Study (IAS), which was Dyson’s academic home for more than 60 years, announced his death.

“No life is more entangled with the Institute and impossible to capture—architect of modern particle physics, free-range mathematician, advocate of space travel, astrobiology and disarmament, futurist, eternal graduate student, rebel to many preconceived ideas including his own, thoughtful essayist, all the time a wise observer of the human scene,” stated Robbert Dijkgraaf, IAS Director and Leon Levy Professor. “His secret was simply saying 'yes' to everything in life, till the very end. We are blessed and honored that Freeman, Imme, and their family made the Institute their home. It will be so forever.”

“Freeman Dyson made fundamental contributions in an incredibly wide variety of fields in physics and mathematics,” stated Edward Witten, Charles Simonyi Professor in the School of Natural Sciences. “His contributions were so wide-ranging that it is virtually impossible for any one person to summarize them adequately. Quantum Electrodynamics, quantum statistical mechanics, Diophantine approximation of numbers, and random matrix ensembles are just a few of the fields to which Freeman contributed at the highest level. But really, he left his mark almost everywhere.”

In 1941, as an undergraduate at Trinity College in Cambridge, Dyson studied physics with Paul Dirac and Arthur Eddington and found an intellectual role model in the famed English mathematician G.H. Hardy, who had previously mentored the mathematical prodigy, Srinivasa Ramanujan. As a mathematician, Dyson published papers on number theory, analysis, and algebraic topology, developing the concept known as “Dyson’s transform” as part of his proof of Mann’s theorem, which serves as a fundamental technique in additive number theory.

“Freeman Dyson was truly a 'free thinker'—there were absolutely no bounds to what he was willing to imagine, no bounds of complexity, of conventional wisdom, of scope and time,” stated Charles Simonyi, IAS Board Chair. “His thoughts, just as the universe he was exploring, and expressed in the title of one of his many books, were truly 'Infinite in All Directions.'”

“A mathematician, physicist, writer, and explorer, who was never afraid to speak his mind, Freeman embodied the values of IAS and more importantly represented the principles that all great scientists aspire to uphold,” stated Jim Simons, IAS Trustee Emeritus and former Member in the School of Mathematics. “Freeman was a marvelous role model, bringing out the best in all those around him. He will be deeply missed.”

During the Second World War, Dyson worked for two years as a civilian scientist conducting operations research for the Royal Airforce’s Bomber Command. He then enrolled at Cambridge University and graduated with a B.A. in Mathematics in 1945.

Dyson was awarded a Commonwealth Fellowship in 1947, bringing him to Cornell University, where he continued to focus his mathematical acumen on theoretical physics, pursuing his graduate work with Hans Bethe and Richard Feynman.

In the spring of 1948, Dyson accompanied Feynman on a fabled cross-country road trip that culminated in one of the most remarkable breakthroughs of 20^{th} century physics. After being steeped in the work of Feynman for months and spending six weeks listening to Julian Schwinger’s ideas in Ann Arbor, Dyson was able to prove the equivalency of their two competing theories of quantum electrodynamics (QED), which describes how light and matter interact. Dyson recalled the moment of discovery as a “flash of illumination on the Greyhound bus.” He had been traveling alone for more than 48 hours, making his way to Princeton, NJ to begin his first Membership at the Institute for Advanced Study.

The seminal paper outlining Dyson’s discovery was published by *The Physical Review* in 1949 under the title, “The Radiation Theories of Tomonaga, Schwinger, and Feynman.” While this question was a central problem of physics, the solution was a mathematical one that Dyson was uniquely positioned to solve given his quantitative training. Dyson’s insights—a Rosetta Stone of physics—provided a more precise understanding of sub-atomic particles consistent with quantum mechanics and special relativity, enabled the first use of Feynman diagrams in calculating scattering amplitudes, and showed how perturbative QED could be logically understood. Shin'ichirō Tomonaga, Julian Schwinger, and Richard Feynman were jointly awarded the Nobel Prize in Physics in 1965 for their work in this area.

At the invitation of J. Robert Oppenheimer, the Institute’s longest-serving Director, Dyson joined IAS as a Member in 1948. Dyson returned to the Institute for a second Membership in 1950. The following year, he accepted an offer of a full professorship from Cornell University. Dyson was invited back to IAS for a third time in 1953 to take up a permanent appointment to the Faculty, joining a group of the century’s top physicists and mathematicians, including Albert Einstein, Kurt Gödel, Tsung-Dao Lee, Deane Montgomery, Marston Morse, Abraham Pais, Carl Ludwig Siegel, Atle Selberg, Oswald Veblen, John von Neumann, Hermann Weyl, and Chen Ning Yang.

The Institute provided Dyson the freedom and flexibility to follow his curiosity to new areas and fields that interested him. In 1956, Dyson began a three-year association with General Atomic, where he worked to design a nuclear reactor that would be inherently safe, or, as colleague Edward Teller put it, “not only idiot-proof, but PhD proof.” The TRIGA reactor is still in production today and used mostly by hospitals.

In 1958, he took a leave of absence from the Institute and moved to La Jolla, California to join General Atomic’s “Project Orion,” working with forty scientists to design an atomic spaceship capable of riding a wave of controlled nuclear pulses into deep space. Dyson recalled the fifteen months spent on the short-lived project as “the most exciting and in many ways the happiest of my scientific life.” The ambitious project had once set its sights on “Mars by 1965, Saturn by 1970.”

Dyson was engaged in the public debate regarding the nuclear test ban treaty and whether or not an exception should be made for purposes of experimentation. In 1960, he was elected to the council of the Federation of American Scientists, and selected as its chair two years later. From this post, he became an effective advocate for the creation of the Arms Control and Disarmament Agency, which existed until 1999 when it was merged with the U.S. State Department. Dyson’s work with this newly created agency gave him greater opportunities to examine the potential consequences of a nuclear war. Concluding that further nuclear testing was “wrong technically, wrong militarily, wrong politically, and wrong morally,” Dyson testified before the U.S. Senate in favor of the nuclear test ban treaty in 1963.

Dyson continued to educate the public on important questions of science, becoming a highly sought-after lecturer and frequent contributor to popular scientific publications on a wide variety of topics, including the relation of science to religion, the prospective colonization of the solar system, harnessing the energy of stars, and climate change. In turning from science to writing, Dyson often recalled the advice of his undergraduate mentor G.H. Hardy, “‘Young men should prove theorems, old men should write books.’ So I decided in 1975 to follow Hardy’s example. Like Hardy, I did not stop proving theorems altogether, but my output of theorems gradually diminished as my output of books increased. I have found, like Hardy, that the art of weaving sentences into a story can be as creative as the art of weaving ideas into a theorem.”

Dyson produced a steady stream of books geared for the scientifically curious among the general public. *Disturbing the Universe* (1979) is a portrait-gallery of people he had known during his career as a scientist. *Weapons and Hope* (1984), which won the National Book Critics Circle Award for Nonfiction in 1984, is a study of ethical problems of war and peace. *Infinite in All Directions* (1988) is a philosophical meditation based on Dyson’s Gifford Lectures on Natural Theology given at the University of Aberdeen in Scotland. *Origins of Life* (1986) is a study of one of the major unsolved problems of science. *From Eros to Gaia* (1992) is a collection of essays and lectures, starting with a science-fiction story written at the age of nine, and ending with a mugging in Washington at age fifty-four. *Imagined Worlds* (1997) is an edited version of a set of lectures given in 1995 at the Hebrew University in Jerusalem about human destiny, literature, and science. *The Sun, the Genome and the Internet* (1999) discusses the question of whether modern technology could be used to narrow the gap between rich and poor rather than widen it. *The Scientist as Rebel* (2006) is a collection of book reviews and essays, mostly published in the *New York Review of Books*. *A Many-colored Glass: Reflections on the Place of Life in the Universe* (2007) is an edited version of a set of lectures given in 2004 at the University of Virginia. *Maker of Patterns* (2018) is an autobiographical account of Freeman’s life through letters written to his parents.

For his contributions to science, mathematics, and public policy, Dyson has been honored with over twenty honorary degrees and has been elected to numerous learned societies, including the Royal Society and the National Academy of Sciences. Among Dyson’s accolades are the National Space Society’s Robert Heinlein Memorial Award (2018), the Henri Poincaré Prize of the International Mathematical Physics Congress (2012), the Templeton Prize for Progress in Religion (2000), the Enrico Fermi Award of the U.S. Department of Energy (1995), the Oersted Medal of the American Association of Physics Teachers (1991), the Wolf Prize in Physics (1981), the Harvey Prize (1977), the Max Planck Medal of the German Physical Society (1969), the Hughes Medal of the London Royal Society (1968), the Lorentz Medal of the Royal Netherlands Academy (1966), and the Dannie Heineman Prize for Mathematical Physics of the American Institute of Physics (1965).

Freeman John Dyson was born on December 15, 1923, in Crowthorne, Berkshire, in the United Kingdom. His father was the musician and composer Sir George Dyson; his mother, Mildred Lucy Atkey, a lawyer and social worker. Dyson is survived by his wife, Imme; children Esther, George, Dorothy, Emily, Mia, Rebecca, and step-daughter Katarina; and 16 grandchildren.

**About the Institute **

The Institute for Advanced Study is one of the world's foremost centers for theoretical research and intellectual inquiry. Located in Princeton, N.J., the IAS is dedicated to independent study across the sciences and humanities. Founded in 1930 with the motto "Truth and Beauty," the Institute is devoted to advancing the frontiers of knowledge without concern for immediate application. From founding IAS Professor Albert Einstein to the foremost thinkers of today, the IAS enables bold, nonconformist, field-leading research that provides long-term utility and new technologies, leading to innovation and enrichment of society in unexpected ways.

Each year, the Institute welcomes more than 200 of the world’s most promising researchers and scholars who are selected and mentored by a permanent Faculty, each of whom are preeminent leaders in their fields. Of the Institute’s current Faculty of twenty-six, two are Fields Medalists and five are MacArthur “Genius” Fellows. Comprised of four Schools—Historical Studies, Mathematics, Natural Sciences, and Social Science—IAS has produced an astounding record of introducing new understanding and is responsible for undeniable progress across disciplines and generations, from the development of one of the first stored-program computers to the establishment of art history as a discipline in the United States. Among its present and past Faculty and Members are 34 Nobel Laureates, 42 of the 60 Fields Medalists, and 18 of the 20 Abel Prize Laureates, as well as many MacArthur Fellows and Wolf Prize winners.