“The strangest man” – this is how Paul Dirac was thought of by many of his friends and this how the great physicist’s biography, “The Strangest Man: The Hidden Life of Paul Dirac, Quantum Genius”, authored by Graham Farmelo, is entitled. Pathologically reticent and introverted, almost autistic, and at the same time a genius compared by his contemporaries to Newton and Einstein – this is how the author portrays him, leading us through Dirac’s life, from his unhappy family life, through the “golden 1920s” of 20th century physics, when quantum mechanics was born, to mature life and decline, when the applauded physicist retired from mainstream physics.
It is not uncommon for mathematicians and physicists to exhibit, to some extent, character traits typical of autism or its milder version, Asperger syndrome: narrow and obsessive interests, social ineptness, poor empathy, preference for predictable situation, literal-mindedness, visual thinking. While the borderline between “Asperger” and only “more nerdy than the norm” is not clear cut, Dirac demonstrated the whole range of autistic syndromes; “Dirac stories” concerning his peculiar or eccentric behavior were widely circulated among his friends. While it is not clear whether these traits were innate or shaped by his upringing (despotic father and overbearing mother), without doubt autistic-type mind strongly influenced, positively and negatively, his scientific output and style of doing physics.
A main figure in the foundations of quantum mechanics, Dirac shone as a very young star, similar to other creators of quantum theory (Born, Heisenberg, Jordan, Pauli, and Schroedinger and Bohr from the older generation), who brought about the revolution before they were even 30. It is safe to say that late 1920s and early 1930s were the “Golden Age” of 20th century physics, when the progress was lightning-fast and new discoveries lay like low-hanging fruits. In the 1940s Dirac commented bitterly, in view of problems quantum field theory was having at the time: “Then, a second-rate physicist could do first-rate work – now, it takes a first-rate physicist to do second-rate work”. Every physicist would love to live in such “interesting times”, when a new unexplored scientific territory opens up. However, the times were also “interesting” in the political sense, which, especially in Germany, did not bode well. For me, the period when quantum mechanics emerged remains the paradigm of “golden youth”, later overshadowed by dark clouds, both in science (when devising quantum field theory proved much more challenging than pioneer discoveries) and individual life, when politics and history divided erstwhile friends: Pyotr Kapitsa was imprisoned in Soviet Union, Bohr and Schroedinger fled Germany, Heisenberg worked for Hitler on nuclear bomb, Oppenheimer directed the Manhattan Project, finally, Ehrenfest shot himself.
The apex of Dirac’s brilliant career comes in the Nobel Prize of 1933. Soon afterwards Dirac marries Wigner’s sister and starts a family. Receiving the prize makes Dirac wonder whether he too will be afflicted by “Nobel disease”, the feeling that after the Nobel Prize, the best years are gone and it will be only downhill from then. Sadly, this is what happened to Dirac – after his groundbreaking work he never made a comparable contribution to theoretical physics. He wasted his talent, struggling to construct field theory not marred by infinities (he rejected renormalization as abhorrent), trying his luck in cosmology and relativity, where did not score major successes, and finally drifted away from the mainstream, remaining isolated from the new discoveries in particle physics.
Looking for reasons of Dirac’s decline, the first candidate would be his approach to physics, based on “top-down” approach, where one starts from elegant mathematical structure and uses it to predict experimental facts, as opposed to “bottom-up” methodology, fitting the theory to known experimental results. Dirac’s style brought dazzling outcomes when, based on purely mathematical considerations, he found the relativistic equation describing the electron, which predicted the existence of antimatter, found experimentally within years of his audacious prediction. Later on, however, attempts at developing relativistic theory based solely on mathematical beauty led nowhere and lead was taken by physicists inspired mostly by experimental discoveries. Dirac never acknowledged any other method than seeking beautiful theories, whose correspondence to reality was only a secondary consequence, so he never came to terms with renormalization, at best a sort of patch on quantum field theory – however, his efforts to build field theory purely axiomatically eventually failed.
Regrettably, some part of Dirac’s failures could be blamed simply on psychology and life events – after starting a family he had, naturally, less time for work and after first successes he could have, even unconsciously, rested on laurels, knowing he had already secured a foremost place in the pantheon of great physicists (or, brutally speaking, got old, since blunting of one’s ambition is the first symptom of senility). Moreover, Dirac shared his ideas very reluctantly, a true loner – without intellectual contact with peers, even the greates genius might eventually burn out. It is unfortunate that even though after marriage Dirac opened up to people around him and led a life more balanced than from the time of his obsessive work on quantum mechanics, he almost grew more passive, satisfied with his family and social position.
A closer look at Farmelo’s book provokes a few questions. When describing relationships between physicists, the author pays much attention to competition, yearning for prestige and acclaim, oneupmanship etc. It is interesting whether the prevalence of such motivations is common to all men or stems from the fact that at the time, physics was a male occupation – the academic community, as well as e.g. the political system, ran by women could look entirely different. For a long time I’ve been puzzled what makes mountain hiking and climbing so popular among physicists – Dirac was an avid climber and I feel that this popularity of climbing is not just a coincidence or subjective feeling. Also, studying the origins of quantum mechanics invites the question of describing the dynamics and structure of newly emerging scientific fields as well as factors which contribute to scientists’ achievements and failures in given time and place – although it is debatable whether the history of science up to now yields any discernible patterns (on the individual level – how to choose the most promising field, on the social plane – how to create an environment fostering the qualitative development of science).