Graham Farmelo applauds a study on the productive friendship of two very different physicists.
The Quantum Labyrinth: How Richard Feynman and John Wheeler Revolutionized Time and Reality
By Paul Halpern
Richard Feynman and John Wheeler, both consummate theoretical physicists, approached their subject in different ways. Feynman was a doer, Wheeler a dreamer. So Paul Halpern aptly describes them in The Quantum Labyrinth, his book about their lives, work and friendship, and the virtues of their complementary styles.
The two men met in 1939, probably in the physics department of Princeton University, New Jersey. Wheeler was then 28, an assistant professor — quiet, measured and with impeccable manners. Feynman was seven years younger, a new and extremely promising PhD student and something of a rough diamond, raised in the borough of Queens, New York City. He became Wheeler's research assistant and they got on well, beginning what Halpern describes as “a long, productive — but often silly — friendship”.
Amid all the larking around, Wheeler and Feynman did useful work. They came up with a new interpretation of the theory of moving electrically charged particles that yielded useful but not revolutionary results. Bursting with creativity, Feynman made his deepest contribution to physics while working alone. Picking up on a profound but under-developed idea by theoretician Paul Dirac, he found a way of reformulating quantum mechanics in terms of a 'sum over paths' between points in space-time. It was mathematical nonsense, as Feynman's friend Freeman Dyson observed. But it worked unfailingly, perfectly reproducing the results of conventional quantum techniques and providing a host of invaluable insights into the theory. This was all that mattered to Feynman, who was unconcerned that mathematicians found the successes of his method baffling. (They still do.)
Building on this success, Feynman came up with an ingenious way of doing calculations about the interactions of subatomic particles using what are now universally known as Feynman diagrams. They, too, were soon essential to the toolkit of particle physicists.
Although Feynman was not short of self-regard, he readily acknowledged his debt to Wheeler: “You might say that my success was a result of things I learned from him.” Wheeler was even more generous: “I am eternally grateful for the fortune that brought us together.” Wheeler's own accomplishments, which Halpern does a good job of highlighting, included a brilliant insight into the fission of uranium nuclei, conceived with the great Danish scientist Niels Bohr. This advance was fundamental to the development of nuclear weapons in the Manhattan Project, which drew in both Wheeler and Feynman. After the Second World War, Feynman dropped military-related work, unlike Wheeler, a nuclear hawk.
Although Wheeler was superficially stolid, he had an imagination arguably even more vivid than Feynman's. During the renaissance of gravity theory, beginning in the 1950s, Wheeler was perhaps its most energetic intellectual leader, willing to entertain even the most adventurous ideas. He enthusiastically supported research into black holes (a term he successfully promoted) and coined the word 'wormhole' to describe hypothetical tunnels in space-time.
Later, Wheeler was no less imaginative in his thinking about information theory. He believed that information is not a secondary concept, but fundamental to the Universe. He coined the shorthand “it from bit” for the concept that every entity — every particle, every field and even space-time — derives its meaning from ideas in information theory. His view is now becoming part of the physics orthodoxy. In later life, Feynman told his colleague Kip Thorne that if you “unwrap the layers of craziness” from Wheeler's ideas, “you will often find a powerful kernel of truth”.
Halpern admires Wheeler and Feynman so much that the narrative is occasionally cloying. As usual, Feynman is portrayed as a popular and generous-spirited figure. Yet I have often heard that he was sometimes unpleasantly aggressive to physicists who might claim to be his peers, several of whom have told me privately that they didn't much like him. Freeman Dyson is an exception to this, although even he told me: “Conversations with Feynman were mostly all about him.”
At first, I doubted the depth of Feynman and Wheeler's friendship, but Halpern eventually convinced me. In one delightful passage near the end of the book, he describes a conference organized by Wheeler and held in Austin, Texas, in 1981 at a venue much too “fancy-schmanzy” for Feynman, as Halpern puts it. Feynman checked out of the room and slept in nearby woods, even though he was in remission from cancer. After one night of al fresco slumber, Wheeler invited him to stay in his home. Shortly afterwards, Feynman told a local reporter: “One of the biggest regrets of my life is that I am not as nice as [Wheeler] is.” Feynman died 7 years later; Wheeler outlived him by 20 years.
The Quantum Labyrinth confirms the received opinion that Feynman was one of the greatest intuitive problem-solvers in twentieth-century physics, a world-class doer. But I suspect that many readers will take most pleasure from the account of Wheeler's inspired dreaming. As Dyson told me: “Posterity has given Feynman his due, but Wheeler has been cruelly underrated.”