Book Review The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom Reviewed by Brian E. Blank bizarre, genially mad, unworldly, and completely, The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom decidedly difficult in their behavior toward their Graham Farmelo fellow man.” Even in that eccentric company, Dirac Basic Books, 2009 stood out. In a conversation with Kurt Gottfried US$29.95, 560 pages in 1959, Bohr remarked that, of all the visitors to ISBN-13: 978-0-465-01827-7 his institute, “Dirac was the strangest man.” Graham Farmelo, Senior Research Fellow at London’s Science Museum and Adjunct Professor In September 1926 Paul Dirac began a five-month of Physics at Northeastern University, has cleverly visit with Niels Bohr at the Institute for Theo- co-opted Bohr’s characterization of Dirac for the retical Physics in Copenhagen. Dirac, then barely title of his recently published biography. With twenty-four years old, had been in possession of his Ph.D. since only May of that year. Bohr was a spareness that would meet Dirac’s approval, middle aged and already a Nobel laureate, but The Strangest Man does double duty as a title: he was accustomed to working with junior col- it intrigues the reader who is only moderately leagues. Nevertheless, collaboration between the interested in Farmelo’s subject, and it announces two physicists proved to be impossible. Whereas a trait of Dirac that the reader will find relentlessly Dirac was taciturn, Bohr was voluble: his habit stressed. Farmelo’s subtitle, The Hidden Life of of thinking out loud produced a constant stream Paul Dirac, Mystic of the Atom, may also be an of sentences in need of revision or retraction. By effective hook, but it is a deceptive one: the phrase bouncing half-baked ideas off Dirac, Bohr elicited “hidden life” suggests a kinky, shady, or salacious little more than the response, “At school I was side of Dirac that did not exist. He did not deal in always taught not to start a sentence until I knew nuclear secrets, he abstained entirely from alcohol how to finish it.” When Bohr bemoaned to Ernest and tobacco, and he accepted only the weakest Rutherford, “Dirac never says anything,” Ruther- doses of caffeine. His love life was conventionally ford replied with a story about a shop owner proper. When an incredulous physicist asked Dirac assuaging a dissatisfied customer who had pur- if he had any vices, the reply was, “No obvious chased a parrot that would not speak. “Please ones.” Nothing in Farmelo’s book contradicts that. forgive me. You wanted a parrot that talks, and I Of course, Dirac did keep many aspects of gave you the parrot that thinks.” his life private, and, as a conscientious biogra- Dirac departed Copenhagen in January 1927 pher, Farmelo has made every effort to ferret to stay with Max Born in Göttingen. In doing so, them out. Dirac could, for example, spend a he joined the steady flow of promising young day at the cinema watching Mickey Mouse films, physicists who traveled between those two cen- a vice he kept secret from his Cambridge col- ters of quantum physics in the 1920s. According leagues.He also concealedhis romance with Margit to Max Delbrück, one of Born’s students and a Balázs (née Wigner), Eugene Wigner’s younger future Nobelist, these peripatetics were “highly sister. When anyone knocked at his door, the Brian E. Blank is associate professor of mathematics at thirty-three-year-old bachelor took down a pic- Washington University in St. Louis. His email address is ture of Margit and hid it in a drawer. For [email protected]. Dirac, keeping a photograph of his swimsuited 1278 Notices of the AMS Volume 58, Number 9 future wife on the mantelpiece was as lurid the University of Bristol arranged for him to pur- as it got. sue a mathematics degree free of charge. On the Paul Adrien Maurice Dirac was born in Bristol completion of those studies, Dirac was awarded a on August 8, 1902, to a Cornish mother and more substantial scholarship to Cambridge, which francophone Swiss father. Paul’s childhood was he entered in October 1923. not a happy one. In interviews he gave late in By 1923 the atom had been actively studied his life, Paul portrayed his father, Charles, as a for over a quarter century. Two constituents of cold tyrant who psychologically abused him and the atom were then known: the electron, discov- his older brother. It is this family dynamic that ered in 1897, and the proton, discovered in 1919. Farmelo highlights in the prologue with which he For more than two decades, beginning with Max begins his work. The setting for the prologue is an Planck’s derivation of blackbody radiation in 1900 evening in 1980 when Margit and Paul entertained and Einstein’s explanation of the photoelectric a friend in their home. In the course of this social effect in 1905, quantum theory had been used to occasion, an innocuous detail Margit mentioned elucidate atomic phenomena. An important con- triggered a two-hour monologue during which Paul firmation of quantum physics was provided by unburdened himself before his startled guest. “I Arthur Holly Compton when, in 1923, he pub- never knew love or affection when I was a child,” lished his observations of collisions between the Paul volunteered. He also spoke of the tragedy of photons of incident electromagnetic radiation and his brother, who, in 1925, bullied and frustrated the free electrons of an irradiated target, thereby by Charles at every turn, took his own life. Paul’s demonstrating the particle nature of light. And visitor, aware ofhis host’s reputationfor equability yet, when Dirac arrived in Cambridge, he consid- and pathological reticence, was shocked to hear ered atoms to be “very hypothetical things”. It was him angrily unleash the demons that had haunted his research supervisor, Ralph H. Fowler, a rising him for seventy years. theoretical physicist in close contact with both Farmelo precedes his prologue with a brief Bohr and Born, who introduced atomic theory to extract from Samuel Butler’s novel, The Way of Dirac. All Flesh: “Unkindness and selfishness on the Despite its successes, quantum theory was then parts of parents towards children…may cast a in an unsatisfactory state: the Bohr-Sommerfeld gloom over their children’s lives for many years.” quantization rules for the spectroscopy of the This self-evident observation, expressed without hydrogen atom were puzzling, and the theory the wit or elegance usually found in a quota- was completely inadequate for the treatment of tion, is actually an ingenious reference. Butler’s complex atoms. A radically new approach was semi-autobiographical story of Ernest Pontifex needed, and Werner Heisenberg, then a Privat- happened to be published a few months after Paul dozent at Göttingen, hesitantly supplied it. On Dirac’s birth. Charles Dirac might as well have July 9, 1925, he completed the final draft of the used Ernest’s father, Theobald, as a model for paper that would introduce quantum mechanics. becoming a cruel, miserly, domineering paterfa- Among his innovations was a multiplication of milias. Whereas Ernest was forced to sing hymns atomic quantities, the noncommutativity of which before Theobald, Paul was forced to speak French he considered to be “a significant difficulty”. Be- to Charles. Just as Ernest was beaten when he fore departing Göttingen for visits in Leiden and mispronounced a word of a hymn, so was Paul Cambridge, Heisenberg, worried that his paper punished for every error he made speaking French. was “crazy”, deposited the manuscript with Born, When such slips occurred at dinner, Paul was re- who was to determine whether it was publication fused permission to leave the table, even if he worthy. was sick. Time and again, Paul, who suffered from On July 28 Heisenberg, still uncertain of the digestive problems all his life, was forced to stay value of his recent work, lectured about the old put and vomit. In Paul’s mind, this treatment was quantum theory in Cambridge. He did, however, the basis of one of his trademark idiosyncrasies: discuss his new approach with Fowler in private to avoid punishment, he learned to say nothing. and, a few weeks later, mailed his English host After graduating with a first-class honors de- the proofs of his article, which Born had, in the gree in electrical engineering from the Merchant meantime, submitted. Fowler scribbled “What do Venturers’ Technical College, an antecedent insti- you think of this?” on the first page and for- tution of the University of Bristol, Dirac won a warded Heisenberg’s paper to Dirac, who received small scholarship to Cambridge. Because Charles it in Bristol early in September. Dirac’s initial im- was unwilling to provide the remaining funds pression was that Heisenberg’s work was “of no necessary for attendance, Dirac searched for a interest”. It was in October, when he was back job instead. At the time, England was suffering in Cambridge, that Dirac recognized the similar- from its worst economic slump since the Indus- ity between the Poisson bracket he remembered trial Revolution, and Dirac joined the ranks of the from classical dynamics and the commutator of two million unemployed. His luck turned when two of Heisenberg’s variables. Very quickly, Dirac October 2011 Notices of the AMS 1279 reformulated Heisenberg’s quantum mechanics, yet allowed that there was still room to doubt simplified the mathematics, clarified the break the foundations on which Dirac and Pauli were with classical theory, and significantly extended building.