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Freeman Dyson, Math Genius Turned Visionary Technologist, Dies at 96

George Johnson, writing for The New York Times:

“Life begins at 55, the age at which I published my first book,” he wrote in From Eros to Gaia, one of the collections of his writings that appeared while he was a professor of physics at the Institute for Advanced Study — an august position for someone who finished school without a Ph.D. The lack of a doctorate was a badge of honor, he said. With his slew of honorary degrees and a fellowship in the Royal Society, people called him Dr. Dyson anyway.

What a mind, what a life:

Richard Feynman, a young professor at Cornell, had invented a novel method to describe the behavior of electrons and photons (and their antimatter equivalent, positrons). But two other physicists, Julian Schwinger and Sin-Itiro Tomonaga, had each independently devised a very different way. Each of these seemed to satisfy the requirements of both quantum mechanics and special relativity — two of nature’s acid tests. But which one was correct?

While crossing Nebraska on a Greyhound bus, Dr. Dyson was struck by an epiphany: The theories were mathematically equivalent — different ways of saying the same thing. The result was QED. Feynman called it “the jewel of physics — our proudest possession.”

Saturday, 29 February 2020