The cause was complications from a fall, said a son, George Dyson.
Mr. Dyson, born in England between the world wars, spent most of his professional life as a kind of genius-in-residence at the Institute for Advanced Study in Princeton, overlapping in his early years with Albert Einstein.
In a career spent traversing fields as diverse as physics, biology, astronomy, nuclear energy, arms control, space travel and science ethics, Mr. Dyson was always obliging when a journalist called him for a grabby quote about the trajectory of humanity. His ideas were reliably unorthodox; the Pulitzer Prize-winning classical composer Paul Moravec once called him “the world’s most civil heretic.”
Of all his notions, his most famous was that alien civilizations, seeking to maximize their supply of energy, would build elaborate megastructures around their parent stars to capture much of the solar radiation. Astronomers periodically see something they speculate might be one of these “spheres” — although Mr. Dyson freely admitted he lifted the idea from science-fiction writer Olaf Stapledon.
Long before he became an oracle, he labored in the trenches of mathematics and physics. He succeeded in the late 1940s in developing an early landmark synthesis of the latest thinking in the theory known as quantum electrodynamics. His resulting paper, “The Radiation Theories of Tomonaga, Schwinger and Feynman,” was regarded as an instant classic and gave Mr. Dyson lifelong credibility in the sciences even as he went on to tackle more speculative interests.
That included the interplanetary spaceship. Project Orion, initiated in the late 1950s, was an effort to design a spacecraft powered by nuclear explosions, rather than traditional fuels, and capable of carrying people throughout the solar system.
A one-meter tall model seemed to work fine, and the Orion team decided they could send humans to Mars by 1968 and to the moons of Jupiter and Saturn two years later. But the government was not keen on nuclear bombs as a form of propulsion and the project, taken over by the Air Force, was eventually terminated.
He contributed to the design of what became known as neutron bombs, work he later regretted bitterly, to the point of describing an article he had written on tactical nuclear warfare as “a desperate attempt to salvage an untenable position with spurious emotional claptrap.” He became an advocate for arms control and served as outside counsel to decision-makers in Washington.
At age 45, Mr. Dyson told The Washington Post in 2014, he had a midlife crisis because he was surrounded by “all these bright kids down the hall who are writing papers faster than you can read them.” He decided to do science as a hobby and become more of a sage, writing books and magazine articles on science, technology and the future. He often contributed to the New Yorker and, later, the New York Review of Books.
His primary job, it seemed, was to think big thoughts — such as this one, from his 1988 book “Infinite in All Directions”:
“As a working hypothesis to explain the riddle of our existence, I propose that our universe is the most interesting of all possible universes, and our fate as human beings is to make it so.”
Depression, war, brainstorm
Freeman John Dyson was born in Crowthorne, England, on Dec. 15, 1923, the son of George Dyson, a composer who was later knighted, and the former Mildred Atkey, a lawyer.
The England of his childhood and teenage years was bleak, ravaged by war and pessimistic about its future.
“Things were really black at that time,” he told The Post in 2014. “We had Hitler coming along. We had horrible memories of World War I. My childhood was so dominated by this disaster of World War I and we saw World War II coming, and it was almost certainly going to be worse. And of course there was this economic depression and England was tremendously polluted. Every evening, my shirt collar was black.”
Small of stature, almost elfin, he endured bullying at his English boarding school but found escape in science fiction, including the works of Stapledon, H.G. Wells and Jules Verne. Poring over an Encyclopaedia Britannica entry, he taught himself calculus by the time he was 15, knowledge that served him well in World War II when he became an analyst for the Royal Air Force Bomber Command.
To his dismay, he calculated that experienced bomber crews had no better chance of surviving a mission over Germany than inexperienced ones, and he saw the futility of loading bomber crews with tail gunners who rarely had anything to shoot at and merely increased the number of British casualties. But in his 1979 memoir, “Disturbing the Universe,” he rued his youthful timidity and conformism and consequent failure to take action to change policies.
Mr. Dyson witnessed how technology had “made evil anonymous,” as the bombers dropped incendiary explosives that ignited firestorms, destroying whole cities. He wondered later “how it happened that I let myself become involved in this crazy game of murder.”
“I sat in my office until the end,” he wrote, “carefully calculating how to murder another hundred thousand people most economically. After the war ended, I read reports of the trials of men who had been high up in the Eichmann organization. They had sat in their offices writing memoranda and calculating how to murder people efficiently, just like me. The main difference was that they were sent to jail or hanged as war criminals and I went free.” (Adolf Eichmann was a key architect of the Nazi Holocaust.)
In 1947, Mr. Dyson journeyed to the United States to study as a graduate student at Cornell University, doing research under the physicist and future Nobel laureate Hans Bethe. He took a cross-country trip by car with a young, brilliant scientist named Richard Feynman. During this period, he spoke to, collaborated with or attended lectures by many other leading scientists, including Edward Teller, Julian Schwinger and J. Robert Oppenheimer.
These were people who had built atomic bombs while simultaneously probing the secrets of the atom. Mr. Dyson had a knack for engaging them in long conversations, sometimes over weeks or months. One day in September 1948, while riding on a Greyhound bus across the plains of Nebraska and spending his vacation deep in thought about the various theories he had been busily absorbing, he had a revelation about how he could combine some of the ideas.
He arrived in Princeton and took up a position, working under Oppenheimer, at the Institute for Advanced Study, where Einstein had been spending his years in exile in vain pursuit of a grand unified theory. The first thing Mr. Dyson did was write down the conclusions he had reached on his cross-country bus ride, and those concepts evolved into his paper on quantum electrodynamics.
A raging intellectual battle took place amid Oppenheimer’s seminars regarding Mr. Dyson’s brainstorm. Until one day, he wrote, “I found in my mailbox Oppenheimer’s formal note of surrender, a small piece of paper with the words ‘Nolo contendere. R.O.’ scrawled on it in his handwriting.”
Peacenik and fringe thinker
In the 1960s, Mr. Dyson changed his mind about atomic bombs. He had been opposed to a ban on atomic testing and had earned a reputation as a military hard-liner — a status that gave him credibility with conservatives in Congress when he later became a peacenik. His conversion came in part from a simple exercise in calculation: He looked at all the atomic explosions starting in 1945 and, to his horror, saw them increasing in number exponentially.
In 1960, he was elected to the council of the Federation of American Scientists, a leading voice for disarmament; he became chairman in 1962 and wrote often for the Bulletin of the Atomic Scientists. In 1962, he also went to work for a new government department called the Arms Control and Disarmament Agency; he later testified in Senate hearings that led to the ratification of a treaty banning atmospheric tests of nuclear weapons. His book on the subject of nuclear war, “Weapons and Hope,” won a National Book Critics Circle Award in 1984.
The same innovations that made atomic bombs and long-range missiles could potentially open space to human exploration, and Mr. Dyson believed humans would find their destiny in the stars. He believed genetic engineering would make it easier.
“Probably we’ll be a million species before long,” he said in a 1998 interview. “For example, if you want to run around naked on Mars, you’d need a thick skin. I can imagine our descendants on Mars will be more like polar bears.”
He was a full-throated humanist without being fully secular. In “Infinite in All Directions,” he sought to reconcile science and religion, or at least create space for them to work congenially in their own orbits. That attitude propelled him to the 2000 Templeton Prize for Progress in Religion.
Mr. Dyson said he was raised in a conventional Christian environment and did not reject that, although as a scientist he could not embrace dogma. Scientists insist all propositions remain open to doubt and refinement.
“I do not make any clear distinction between mind and God. God is what mind becomes when it has passed beyond the scale of our comprehension,” he wrote.
His technophilia may explain his apostasy on global warming. In the early 2000s, he drew furious criticism from other scientists and environmentalists for his views on climate change. Although he did not deny the Earth was warming — he was not a global warming denier in the strictest sense — he thought the environmental movement had overstated the threats to the planet.
“I just don’t see any evidence that global warming is particularly dangerous,” he said.
That view is not shared by the overwhelming majority of scientists. Mr. Dyson’s fringe position reflected a deeper philosophy: that change is coming, inevitably, and we should embrace it and not fear it. His scenarios for the future always involved a completely different sort of human existence.
In Mr. Dyson’s expansive cosmos, our destiny is to spread intelligence everywhere.
“The universe is like a fertile soil spread out all around us, ready for the seeds of mind to sprout and grow,” he wrote. “Ultimately, late or soon, mind will come into its heritage.”
Mr. Dyson’s first marriage, to mathematician Verena Huber, ended in divorce. Survivors include his wife since 1958, the former Imme Jung of Princeton; two children from his first marriage, George Dyson of Bellingham, Wash., and Esther Dyson of Manhattan; four daughters from his second marriage, Dorothy Dyson of Redding, Calif., Emily Dyson-Scott of La Jolla, Calif., Miriam “Mia” Dyson of Freeport, Maine, and Rebecca Dyson of Ashland, Ore.; and 16 grandchildren.
“In some ways, my lifetime has been amazingly quiet and stable. My mother lived through much bigger changes,” Mr. Dyson told The Post. “She started her life riding around in a pony cart and finished up flying in jet planes. I haven’t had any changes as big as that.”
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