Freeman Dyson, a physicist whose interests often took him to the edge of science fiction, has died at the age of 96. Dyson is probably best known for his idea of eponymous spheres that would allow civilizations to capture all the energy radiating off a star. But his contributions ranged from fundamental physics to the practicalities of using nuclear weapons for war and peace. And he remained intellectually active into his 90s, although he wandered into the wrong side of science when it came to climate change.

Degrees? Who needs ‘em?

It's difficult to find anything that summarizes a career so broad, but a sense of his intellectual energy comes from his educational history. Dyson was a graduate student in physics when he managed to unify two competing ideas about quantum electrodynamics, placing an entire field on a solid theoretical foundation. Rather than writing that up as his thesis, he simply moved on to other interests. He didn't get a doctorate until the honorary ones started arriving later in his career. His contributions were considered so important that he kept getting faculty jobs regardless.

That came after a fairly conventional start to his education: an undergraduate degree from the University of Cambridge. Like many other scientists at the time, his career was interrupted by World War II, with Dyson working at the Royal Air Force's Bomber Command, evaluating data from completed missions and finding ways of getting more out of the nation's aircraft. After the war, he returned to Cambridge to finish his degree, then started in a PhD program at Cornell University in the US.

It was during this time that the field of physics was struggling between two different ways of describing the behavior of particles interacting through electromagnetism. Two researchers, Sin-Itiro Tomonaga and Julian Schwinger, had independently developed a theory to explain how things like electrons and protons interacted (Tomonaga's ideas were earlier but didn't make it out of Japan due to the war). Richard Feynman, meanwhile, developed diagrams that formalized the math describing particles' behavior. Dyson was the first to recognize that the two very different approaches were mathematically equivalent.

Possibly because of the Nobel Prize's rules, which limit it to three recipients, the other three researchers ended up with the Nobel Prize. But Dyson did manage to secure a faculty job at Cornell without the need to finish his thesis. Eventually, he moved to the Institute for Advanced Studies and remained there for the rest of his career.

While his location was stable, his interests were anything but. Dyson contributed to both mathematics and other areas of physics, but he also ventured into both the practical and fanciful. He designed a civilian nuclear reactor for producing isotopes used in medicine and a rocket propulsion system that relied on the detonation of nuclear warheads. At the same time, he also evaluated the use of nuclear weapons on the battlefield for the US government.

Science fiction, entertainment and otherwise

At the same time, Dyson often mixed science fiction with practical science. An interest in the search for intelligent life led him to consider the growing energy needs of advanced civilizations. The results were taking an idea that had been floating in the science fiction world—a sphere that surrounds a star and captures much of its energy—put on firm mathematical footing and converted into a signal that could be searched for by telescopes.

Dyson's interest in spacefaring civilizations extended to humanity's future, and he thought a lot about how we might manage to make our way out into the galaxy. Some of the ideas, like the nuclear-powered rocket, were on firm scientific footing. But he also got a bit over-enthusiastic about our ability to genetically modify trees, proposing that we might get them to the point where they could grow in chambers in hollowed-out comets. That same sort of optimism led him to believe that we could simply engineer trees to control our carbon emissions, making climate change a non-issue.

Not content to promote science-fiction solutions to our problem, Dyson voiced poorly informed criticisms of climate models and went on to dismiss concerns about our warming planet. He even criticized the scientists who were producing that data. He eventually lent his name to a UK organization, the Global Warming Policy Foundation, that produces pseudo-scientific advocacy papers in favor of doing nothing about climate change. When the Institute for Advanced Study put on a series of talks to celebrate his career, one of the featured speakers was William Happer, who delivered a nonsensical rant about climate change (Happer eventually went on to attack climate scientists from within the Trump administration).

But the celebration also contained fantastic talks about the possibility that life on Earth actually originated on Mars and the bizarre chemistry that occurs at the extreme pressures inside gas giants. For the most part, those talks better captured Dyson's career: radical ideas that were mostly on solid scientific foundations.

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