I’d try to fill airtime — and trigger his silent but shoulder-bobbing laugh — with trivial bits, like recounting a tale relayed by his son, George Dyson, an author and historian of technology, regarding an email the elder Dyson once received from a woman with a cleaning business. Subject line: “vacuum — unsatisfied.” Cindy had spent $500 on the DC14 model and had come to hate it with a passion, she explained in great detail. The suction on the rug was so strong that it threw “my shoulder out (NO LIE) having to push so hard.” She signed off, defeated: “I know that I will not hear from Dyson.”
Dr. Dyson, ever the reliable correspondent, hit Reply: “Thank you for the hate mail which I enjoy reading. I get quite a lot of it because my name is Dyson. But I am sorry to tell you that I am the wrong Dyson. My name is Freeman and not James. I suggest that you take the trouble to find James’s address and send the message to him. I wish you good luck and good health.”
Sara Seager, an astrophysicist and planetary scientist at M.I.T., lunched with Freeman when she was a long-term member of the institute. Sometimes, they talked about exoplanets and the underlying physics. Dr. Dyson was generous with his time and insight, she said: “He was kind even when he asked very tough questions!” And long after his lunches with other postdocs were over, she noticed, he would still be there, reading.
At our lunches, Dr. Dyson always bestowed something unexpected. One day it was a problem he was toying with, which he called “Rank, Crank and Prank.” It dated back to his undergraduate days and pertained to “partitions” — sums of all the positive integers that add up to a desired integer, for example 4, which has five partitions: 4, 2+2, 3 +1, 2 + 1 + 1 and 1 + 1 + 1 + 1. (The order of “summands” doesn’t matter.) “The Prank isn’t yet discovered,” he said. “The Rank exists and the Crank exists. The Prank is just a dream” — the prank was just his playing around with renewed investigations.
Another day, jumping off the question of truth versus beauty in science, he mentioned an essay he had just finished on a related dichotomy, “Is Science Mostly Driven by Ideas or by Tools?” The essay, published in 2012, marked the 50th anniversary of “The Structure of Scientific Revolutions,” by the theoretical physicist and historian Thomas Kuhn. Dr. Kuhn’s favorite word, Dr. Dyson reckoned, was “paradigm,” a system of ideas that dominate a scientific era. “A scientific revolution is a discontinuous shift from one paradigm to another,” he added. “The shift happens suddenly because new ideas explode with a barrage of new insights and new questions that push old ideas into oblivion.” As a counterpoint, Dr. Dyson mentioned Peter Galison, a physicist and historian at Harvard, whose work focused more on experiments and instruments. Dr. Galison had published “a fatter but equally illuminating book” called “Image and Logic” — a history dominated by tools, whereas Kuhn’s was a history dominated by ideas.
“Roughly speaking, Kuhn stands for beauty and Galison for truth,” Dr. Dyson said. “My answer is that we need them both.”
