AN INFORMATIVE ACCOUNT OF THE WORK OF THESE TWO MEN
Paul Halpern is Professor of Physics at the University of the Sciences in Philadelphia. He wrote in the Introduction to this 2017 book, “More than seventy-five years ago… a quiet revolution began here in our understanding of the nature of time. Discussions between two brilliant physicists, Richard Phillips ‘Dick’ Feynman and John Archibald ‘Johnnie’ Wheeler set off a chain of events that fundamentally recast the notion of time and history in quantum physics. Ultimately, their ideas transformed the concept of time from a single stream flowing inalterably in one direction into a labyrinth of alternatives extending backward as well as forward. By probing Princeton’s past, we wish to unravel how this radical change was born and understand its impact on the contemporary search for a complete explanation of physical reality.” (Pg. 1)
He recounts, “When admitted to Princeton, Feynman had originally been assigned as Wigner’s teaching assistant… At the last minute, Feynman was switched to assisting Wheeler instead. In retrospect, each considered the substitution one of the most auspicious moments in his career… Feynman and Wheeler’s collaboration… would lead to a rethinking of the fundamentals of quantum physics through the concept of ‘sum over histories,’ introduced by Feynman and named by Wheeler. That revolutionary approach sees actuality as a composite of all possibilities… The two physicists would prove the perfect team: Feynman cautious and thorough in his brilliant calculations, Wheeler bold and imaginative in his far-reaching notions. Honing and reworking bizarre hypotheses into workable solutions would become their joint specialty. A lifetime journey of intrepid explorations would launch in Wheeler’s Princeton office.” (Pg. 7-8)
Later, he notes, “Wheeler… loved bringing up with Feynman (and others) abstruse philosophical questions and thinking of ways to test them. Feynman disliked abstractions but relished the testing part. That’s one reason they were well matched.” (Pg. 25)
He explains, “Wheeler had thought deeply for years about the idea of replacing the field approach to electromagnetism with the more direct concept of action at a distance… Action at a distance, Wheeler thought, would make particle physics simpler by making electrons sole masters of their own fate. They would govern their own actions without an intermediary… Part of the motivation for resurrecting action at a distance in quantum electrodynamics stemmed from a growing understanding that many quantum phenomena coordinate their features remotely. Such remote interplay, called ‘entanglement,’ transpires when two particles with complementary values of a quantum number … such as spin are linked in the same system, no matter how distant they are physically.” (Pg. 59)
He states, “Wheeler found Feynman’s path integral method truly remarkable… To help promote what he saw as a revolutionary new concept, he decided to nickname it ‘sum over histories.’ … As his excitement for Feynman’s method grew, Wheeler thought he might even be able to persuade Einstein of its brilliance. He stopped by Einstein’s house again and had a deep discussion with him in his upstairs study. Wheeler asked if Feynman’s novel technique might persuade him to drop his opposition to quantum theory. However, Einstein, eyeing the theory’s chance component, couldn’t be swayed. ‘I can’t believe that God plays dice,’ said Einstein. ‘But maybe I’ve earned the right to make my mistakes.’” (Pg. 75-76)
He observes, “Wheeler and Feynman’s paper thus ends… imagining a world in which the future influences the past, and vice versa. By removing any distinction between forward and backward causality… it makes the future and past equally relevant to the future… In the Wheeler-Feynman absorber theory… particles feel the impact of events taking place in the future… From … Wheeler and Feynman’s concept… an entirely novel approach to electrodynamics would sprout… allowing the past, present, and future to speak to each other.” (Pg. 107)
He notes, “General relativity soon became Wheeler’s canvas. He aspired to craft anything in physics out of warped spaces and energetic fields. He dropped the concept of ‘everything is particles’ and adopted ‘everything is fields.’ It was a complete turnabout. Once he thought fields were an illusion; now he started to feel the same about material things. Once he believed in action at a distance; now all happened locally. Seeing how the brave new world of geometry and fields panned out would be an exciting adventure.” (Pg. 177)
Of the ‘Schrödinger’s Cat’ thought experiment, he says, “[Hugh] Everett’s interpretation made a completely different prediction. Once the system was set up such that the cat’s fate was entangled with that of the sample, reality would bifurcate. In one branch, the sample would decay… the cat would be poisoned… In the other, the cat would live… [The two versions] would know nothing of each other … They’d live in two slightly different alternative branches of reality---separated in an abstract realm of all possibilities. There would be no ‘bump’ when reality split, so neither would find anything unusual.” (Pg. 191)
He explains, “Everett’s hypothesis remained little known until 1970, when [Bryce Seligman] DeWitt penned a popular description of it for ‘Physics Today.’ He re-dubbed it the ‘many worlds interpretation’ (MWI) of quantum mechanics… DeWitt was the MWI’s most ardent advocate and popularizer… Nevertheless, he could fully see why others would doubt the idea that reality split ceaselessly into myriad copies… the MWI has become a respected alternative (in some circles at least) to the Copenhagen interpretation. Wheeler maintained mixed feelings about the MWI… he was… very uncomfortable with terms such a ‘many worlds,’ ‘parallel universes,’ and ‘splitting.’ Why bring in more than one universe? Feynman largely ignored the MWI interpretation… Such alternate realities seem too ‘science-fictiony’ for many hard-nosed physicists. Even for someone like Wheeler, who relished ‘crazy ideas,’ the notion of … .actual parallel universes was a bridge too far. For him, untestable assertions bordered on religious credos rather than representing authentic physics.” (Pg. 196-198)
He records, “surprisingly, John Wheeler would come to adopt an information-centered viewpoint… linked to quantum measurement theory. In the final stage of his research career, he would abandon ‘everything is fields’ for ‘everything is information.’ … Among the catalysts for Wheeler’s transformation were his interactions with a new generation of students far more familiar with computers and their workings… The notion of time entered strongly into Wheeler’s new approach… gaining an understanding of the flow of information is another way of trying to model time.” (Pg. 231)
He recounts, “Wheeler explained to his former students his vision that the laws of physics were forged in the Big Bang. Other universes might be out there with completely different laws. There must be some reason our universe has the particular laws it has. Perhaps if it didn’t, there would be no life and no conscious entities to experience it. Wheeler’s arguments were a variation of the ‘anthropic principle’… Such abstract reasoning was anathema to Feynman, as it couldn’t be proven or disproven… no one could assemble an array of universes and see what happened. So why talk about it?” (Pg. 234)
Ultimately, “Wheeler’s speculative notions, always a bit on the fringes, had become almost unfathomably abstract. They were so philosophical that no one could imagine how to test them… Yet Wheeler had no desire to be known as a New Age guru or pseudoscientist… He complained vehemently … when at a meeting of the American Association for the Advancement of Science, he found himself seated on a panel with parapsychologists. Neither did Feynman want such associations, but in 1984 he did give a talk … updating his views on nanotechnology, as the Esalen Institute… a New Age haven for hot-tubbers. He also experimented with flotation tanks, seeing what isolation and sensory deprivation would do to his thoughts.” (Pg. 253)
This book will be of great interest to anyone studying Wheeler and Feynman, as well as the development of contemporary physics.