Freeman had no particular hobbies, played no sports. He and his family seldom went to church. Freeman had played violin as a child, and all his children took some kind of lessons, but otherwise music was not a big part of the life at Battle Road Circle. Freeman would attend concerts if invited.10 The children would practice their instruments on an old wooden music stand once owned by Einstein. Sometimes Freeman and Imme would play recorder duets.11
Freeman liked to read books to his kids, sometimes poetry. The Laura Ingalls Wilder Little House on the Prairie books were the favorite. They’d play the occasional board game such as Scrabble. Family vacations often consisted of summertime trips to Jason meetings, usually in California. Imme would take the kids (sometimes without Freeman) to visit her mother in Germany. Freeman’s days during the week were pretty regular: breakfast at seven, off to the Institute at eight, and back for dinner at six or seven. Freeman didn’t cook but would regularly help with the cleanup.12 Dinner would sometimes go on a bit if Freeman was holding forth on some topic. The children were expected to stay and listen.13 On snowy days Freeman might use the kids’ sled to get to work going downhill. Esther, if she wanted the sled, would have to fetch it back from the Institute.
Overall, domestic life was pretty comfortable. At the time of Freeman’s divorce from Verena he admitted to her that perhaps he hadn’t been prepared for marriage.14 With Imme, things were different. He was happy to be married to a German wife, he said, since he appreciated the warmth of a German family.15 Esther remembers as a child reading The Diary of Anne Frank and being charmed by the fact that Peter and Anne, who fell in love, should be living in the same attic (hiding from the Nazis). Freeman told her that sometimes you love the one you’re with. Esther felt at the time that this was an unromantic view, but later she saw wisdom in the remark.16
FRIENDS SECOND
In a professional life crowded with research, attendance at international meetings, and contributions to journals and books, Dyson had many opportunities for friendship. Start with those who had stood as mentor figures: Dyson and Feynman were still friendly in the 1960s but didn’t see much of each other. In 1965 Dyson spoke at a special birthday celebration for Hans Bethe. In the summer of 1969 he worked with Rudolf Peierls at the University of Washington. He saw a fair amount of Ted Taylor, especially since the two were both becoming more interested in arresting the spread of nuclear weapons.
And Robert Oppenheimer? Was he a friend? When Dyson first came to the Institute for Advanced Study in the fall of 1948, aflame with his ideas for making QED work, Oppenheimer had been an enemy, or at least a severe critic. Even after Oppie had come around to accepting QED (“Nolo Contendere”), and indeed becoming one of Dyson’s biggest boosters, he never was much of a mentor to Dyson in the way that Bethe or Peierls had been.
Following the debacle of Oppenheimer’s security clearance hearings in 1954, and with more time to devote to his duties as Institute director, he and Dyson saw a lot more of each other. The Dysons and Oppenheimers grew closer socially as the years went by. Dyson, along with several Institute colleagues, nominated Oppenheimer for the Enrico Fermi Award of the Atomic Energy Commission, the highest award (now bestowed by the Department of Energy) by the U.S. government for nuclear work.*
Dyson also helped to arrange a grand party for Oppie’s sixtieth birthday in 1964, including a commemorative series of essays published in the Review of Modern Physics.17
Oppie died in 1967, and Dyson helped with the funeral arrangements.18 He also participated in a sort of annual memorial for the man in the form of a small by-invitation gathering of scientists at the home of Oppenheimer’s widow, Kitty, for a number of years on the anniversary of Oppie’s death. At one of these Steven Weinberg presented an early description of his theory unifying the weak nuclear force and the electromagnetic forces into a single mathematical framework. At the end of his talk Weinberg was a bit nervous when he saw Dyson begin to make a remark. Years before, when Weinberg was a graduate student at Princeton, he had come over to Dyson’s office to ask the professor some questions. Dyson, usually polite, was on this occasion cold to Weinberg and dismissive of his work. The student left very disappointed. Now, years later, Dyson was about to comment again on Weinberg—this time not to criticize but instead to ask the moderator that Weinberg, who had made such a brilliant presentation, be allowed to speak beyond his allotted time.19
Oppenheimer’s death marked a new phase in the life of the Institute for Advanced Study. A new jurisdiction within the Institute, the School of Natural Sciences, was created in 1966. For most of the years covered in this chapter (mid-1960s to mid-1970s) the faculty of this school consisted of Dyson, Tullio Regge, Roger Dashen, Stephen Adler (all particle theorists), John Bahcall (astrophysics), and Marshall Rosenbluth (nuclear and plasma physics). This permanent faculty was supplemented by a perpetually changing succession of young scientists, “members,” who would visit for a year or two, often collaborating or just consulting with the faculty. This suited Dyson. He could provide important advice to a novice theorist, but was not tied down for years of overseeing dissertation research. At the Institute, seminars were frequent, and impromptu hallway encounters were fruitful. But no formal courses were offered and no degrees awarded.
Besides his academic year work at IAS and his summertime work with Jason, Dyson was an active member of the physics community. He frequently published articles in a diverse range of journals. He often attended meetings of the American Physical Society and served on a committee of the American Institute of Physics overseeing the translation of physics journals (mostly Russian) into English. He traveled to numerous meetings or seminars or award ceremonies abroad, including those in Holland, Russia, France (1966), Australia (1967), Britain (1968), Germany and Austria (1969), Italy and Britain (1970), Armenia (1971), Britain (1972), Scotland, Germany, and Spain (1974), Russia (1975), Israel (1977), and so on.
As the need arose, Dyson could help teach a course at nearby Princeton University. The most notable of these was Nuclear Weapons, Strategy, and Arms Control, in the spring of 1976, taught with historian Martin Sherwin (who would with Kai Bird later write an impressive biography of Oppenheimer, American Prometheus) and Harold Feiveson, on the faculty of Princeton’s Woodrow Wilson School of Public and International Affairs.
One of the enrolled undergraduates, John Phillips, came to Dyson for tutelage. For his term paper in the class, Phillips attempted to design an atom bomb. Without revealing any of the restricted nuclear knowledge in his own head, Professor Dyson tried to steer his young protégé in the right direction. Phillips’s personal observations of Dyson include the following: Dyson wore oversize galoshes in the snow, had sympathetic eyes, was patient, and wanted to be called by his first name.20
From nonclassified government documents, freely available to anyone, Phillips proceeded to gather a primer of frightening specificity, showing step by step how to build a nuclear bomb. Dyson was appalled at the amount of dangerous information freely available, and suggested, perhaps jokingly, that the paper be burned. He gave Phillips an A in the course.21
Only months later, when the Trenton Times ran a story about Phillips’s project, did the whole affair flash into prominence. Phillips, and Dyson too, were suddenly thrust into a flood of publicity, with journalists and several shady individuals with undisclosed affiliations from around the world seeking interviews. Dyson was proud of Phillips for responsibly handling his short-lived fame as “The A-Bomb Kid.” Dyson was not proud of the way newspapers pumped up the drama.22
COLLABORATORS
The exercise of mathematics is often a solitary pursuit. Indeed some of Dyson’s happiest intellectual labors were performed alone—as a boy in a tree reading, in the family cottage near the Isle of Wight solving equations, or on a bus crossing Nebraska imagining electron-photon interactions.
But for two important rounds of mathematical physics research, Dyson was to pair up with just the right collaborator. The first of these partnerships
helped establish a new branch of statistical mechanics. Pioneered in the nineteenth century by Ludwig Boltzmann and James Clerk Maxwell, statistical mechanics is a method for deriving average properties of a large ensemble of objects. A good example is Maxwell’s calculation of the spectrum of velocities for molecules in a bottle of gas at a given temperature. Raise the temperature a bit, and the velocities also shift upward.
The statistical problem Dyson now tackled was how to calculate the energies of nucleons (protons and neutrons) inside an atom’s nucleus. Princeton physicist Eugene Wigner got Dyson started on the problem in 1959, just as Dyson was leaving Project Orion. One cannot calculate the velocity of every single molecule in a warm gas, and analogously one cannot calculate the quantum energy of nucleons in an excited nucleus. Wigner, however, had attempted an approximate description of the nucleus in the form of an array of parameters—a matrix of numbers, or a spreadsheet—that represented the complicated relations among the energy levels of the nucleus. As a start to understanding those relations one can do no better than guess the relative spacings of nuclear energy levels. These guesses appear as random numbers arranged in the matrix.
Dyson enthusiastically embraced the mathematical beauty of random matrices. In the summer of 1961, working at Brookhaven National Laboratory on Long Island, he wrote a series of papers on this topic in quick succession. In 1962 Dyson invited one of the world’s experts on this subject, Madan Lal Mehta, to join him for a year at the Institute. Together they helped firm up the mathematical framework for this kind of statistical mechanics—not unlike what Dyson had done for quantum electrodynamics years before—so that it could be used for other physics topics in addition to the problem of nuclear energy levels.23 In later decades other theorists were to apply the random matrix approach to such things as disordered solid materials, quantum gravity, and quantum chaos.
The subject of random matrices held Dyson’s interest over several decades. The potential mathematical meaning behind random matrices Dyson compares to an iceberg.24 Above is the tip—the theory is concerned with things like nuclear energy levels. But beneath the surface, he suspects, is much more. One of the most intriguing aspects of random matrix theory is that it seems to be tied to a mathematical issue that has fascinated Dyson since he was a teenager, namely the so-called Riemann zeta function, whose behavior is related to the spacing of prime numbers.25
Dyson was invited to spend time in the summer of 1970 at the Scuola Normale Superiore in Pisa, Italy, where an astronomy meeting was scheduled to coincide with his stay. There he was gripped by an impetuous desire to work again on statistical mechanics, the subject that had consumed so much of his time years earlier. Whenever he had the chance he snuck away from his astronomer friends for his illicit tryst with the forbidden topic. He stole to a quiet place, the farthest nook of the library, where he stealthily wrote about his true love—random matrix theory.26 As late as 2010, Dyson’s articles on random matrices were still among the most downloaded of papers from The Journal of Mathematical Physics. One corner of this research bears his name in the form of “The Dyson Conjecture.”
The Dyson-Mehta partnership was to be followed by a fruitful collaboration between Dyson and Andrew Lenard, a young physicist who visited the Institute during the 1965–66 year. The problem they addressed was one of the most basic in all of science: why is matter stable? They tried to show mathematically, as if they were proving some theorem of geometry, that all the positively and negatively charged particles, all the protons and electrons, in all the atoms that make up a solid object like a bowling ball, should conspire to remain solid and not collapse into a puddle. The explanation also had to account for the fact that two bowling balls could not occupy the same place at the same time.
You’d think by the 1960s that scientists would have worked out the exact explanation, but they hadn’t. The mathematics seemed too complicated. Chemical forces, in the form of electromagnetic interactions binding atoms and molecules to each other, naturally keep things stable. But subtle quantum effects were also expected to play a role, and these ideas hadn’t yet been formulated into a mathematical model. Two physicists, Michael Fisher and David Ruelle, offered a prize, consisting of a bottle of champagne, to anyone who could deliver a convincing argument.
Lenard brought the stability problem to Dyson’s attention. The two men worked together, usually with Dyson trying out ideas standing at a blackboard and with Lenard asking occasional questions.27 After some months they had themselves the first formal explanation for the stability of matter.
Dyson and Lenard laid out their explanations in two lengthy papers in The Journal of Mathematical Physics. The work was good enough to win the champagne. Years later, looking back on this bit of research, Dyson remarked upon the advancing nature of scientific knowledge and how most efforts are eventually superseded. Characteristically, he apologized for him and Lenard taking forty pages of text to say what two later physicists, Elliott Lieb and Walter Thirring, did more elegantly and rigorously in four pages.28
A FRIENDLY UNIVERSE
Freeman Dyson was interested in just about every physics problem with a mathematical angle. It’s not surprising then that Dyson should add “astronomer” to his résumé. He had, of course, demonstrated a serious interest in things celestial—work on Orion, adaptive optics, Dyson spheres. But now he would become more professionally involved.
In 1962 he wrote a paper describing a hypothetical “gravitational machine,” consisting of large masses, such as a pair of stars, surrounded by numerous orbiting lighter objects. The idea behind this paper was to show how gravitational energy could be extracted from such a system and to study the emission of gravity waves. Dyson submitted the article to the Gravity Research Foundation competition. It finished in fourth place that year.
Dyson’s growing interest in astronomy was facilitated by a sabbatical year he spent (1967–68) at Yeshiva University in New York City. There he learned astrophysics even as he taught it. Pulsars were a particular area of interest for Dyson and for many other astronomers. Pulsars were mysterious points in deep space casting out bursts of light at regular intervals ranging from seconds all the way down to milliseconds. One of Dyson’s first pulsar papers discussed the chance that they could be emitters of measurable gravity waves. The waves, Dyson thought, would be too weak to register at any one moment in terrestrial detectors. But he figured that over time the arriving gravity waves from a powerful pulsar might leave some accumulative trace in the Earth. So he sought access to long-term seismic records from a station in Montana that for many years had monitored nuclear test explosions. Unfortunately for Dyson’s scheme, the monitoring data corresponding to actual explosive events had been retained while the much more voluminous and apparently useless monitoring data corresponding to “quiet” times when explosions had not been occurring, exactly what Dyson wanted, had been discarded.29
His roving curiosity brought him to question whether the constants of nature are really constant. You’d expect that things like the charge of all electrons, e, or the universal gravitational constant, G, would stay the same. But as we saw with the overthrow of mirror symmetry (parity violation), scientists scrupulously keep looking for discrepancies from prevailing knowledge. Dyson looked into the matter but concluded that over the life of the Earth, e and G couldn’t have changed by more than an infinitesimal amount.30
When Dyson wasn’t doing astronomy he was writing about it. An essay in the September 1971 issue of Scientific American is an excellent example of his manifesto-style writing: determined but not dogmatic, thorough but not exhausting. The piece is about the flow of energy through the cosmos and it begins, not surprisingly, with a quote from Dyson’s favorite poet, William Blake, including the line, “Energy is the only life and is from the Body; and Reason is the bound or outward circumference.”
The article is concerned mainly with explaining why, if gravity is apparently so dominant in the universe, all the visible objects in the sky—stars, plane
ts, galaxies—didn’t long ago shrink and merge into nothingness. The answer is that many countervailing forces, what Dyson calls “hang-ups,” hold off awhile what seems like an inevitable slide into collapse. Examples include the nuclear reactions inside stars that keep the stars inflated, or the angular motion of planets tracing out orbits around stars, or the revolution of pinwheel galaxies around their own centers.
One of the most important themes of the article, and one that would become an abiding principle for Dyson in coming years, is the status of living things in a universe that appears indifferent to what happens on Earth. Yes, Dyson says, the existence of life on our planet is shaped by the local physical circumstances, such as the fact that we would not be here thinking about all this if the Earth were a bit closer or further from the sun or if those nuclear reactions fizzing away in the sun were a little stronger or weaker.
Life depends on energy, but in some sense maybe energy depends on life:
It would not be surprising if it should turn out that the origin and destiny of the energy in the universe cannot be completely understood in isolation from the phenomena of life and consciousness.31
Dyson was not yet exactly subscribing to what has come to be known as the Anthropic Principle, since he was not restricting his proposition to thinking creatures, or at least not to Homo sapiens, but to life in general.
Speaking from the secure position of a tenured spot at the Institute for Advanced Study and holding a consummate scientific reputation, Dyson was here tentatively launching a career as a science prophet, not in the sense that he could accurately foresee the future but rather that he was pointing to some kind of reality that hadn’t properly been appreciated. In the Scientific American piece he allowed himself to say such things as “I believe the universe is friendly,” and that he can “look to the sky with hopeful eyes.” These were to become typical Dyson nostrums. He wanted to do more than inform his readers. At the risk of being saccharine he sought to persuade and inspire.
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