The Strangest Man
The Strangest Man
The Hidden Life of Paul Dirac,
Quantum Genius
GRAHAM FARMELO
To my mother and the memory of my late father
Contents
Prologue
The Strangest Man
Abbreviations in Notes
Notes
Bibliography
List of Plates
Acknowledgements
Index
[T]he amount of eccentricity in a society has generally been proportional to the amount of genius, mental vigour, and moral courage which it contained. That so few now dare to be eccentric, marks the chief danger of the time.
JOHN STUART MILL, On Liberty, 1869
We are nothing without the work of others our predecessors, others our teachers, others our contemporaries. Even when, in the measure of our inadequacy and our fullness, new insight and new order are created, we are still nothing without others. Yet we are more.
J. ROBERT OPPENHEIMER, Reith Lecture, 20 December 1953
Prologue
[A] good deal of unkindness and selfishness on the part of parents towards children is not generally followed by ill consequences to the parents themselves. They may cast a gloom over their children’s lives for many years.
SAMUEL BUTLER, The Way of All Flesh, 1903
All it took was a single glass of orange juice laced with hydrochloric acid. A few minutes later, it was clear that his digestive problems were due to a chronic deficiency of stomach acid. For months, he had been admitted to hospital every few weeks to be fed vitamins intravenously, but the doctors had no idea why his digestion was so poor. Now, following the orange-juice experiment, a laboratory test on the chemical contents of his stomach confirmed the conclusion that his stomach contained far too little acid. The simple prescription of a pill to be taken after every meal ended almost eight decades of digestive problems. As a result, Kurt Hofer, the friend who suggested the experiment and made the correct diagnosis, became the reluctant health guru to Paul Dirac, one of the most revered – and strangest – figures in the history of science.
Hofer and Dirac both worked at Florida State University but otherwise appeared to have little in common. Hofer – just over forty years of age – was a top-drawer cell biologist, a spirited raconteur who told all comers of his early family life among Austrian mountain farmers and his moment of cinematic glory as a well-paid extra in The Sound of Music. Hofer’s eyes glittered when he told his stories, his thickly accented voice swooped and surged for emphasis, his hands chopped and shaped the air as if it were dough. Even in this lively company, Dirac was unresponsive, speaking only when he had a pressing question to ask or, less often, a comment to make. One of his favourite phrases was: ‘There are always more people who prefer to speak than to listen.’1
Dirac was one of the pre-eminent pioneers of quantum mechanics, the modern theory of atoms, molecules and their constituents. Arguably the most revolutionary scientific breakthrough of the twentieth century, quantum mechanics uprooted centuries-old prejudices about the nature of reality and what can, in principle, be known for certain about the universe. The theory also proved to be of enormous utility: it underpins the whole of modern microelectronics and has answered many basic questions that had long defied straightforward answers, such as why electricity flows easily through wire but not through wood. Yet Dirac’s eyes glazed over during talk of the practical and philosophical consequences of quantum physics: he was concerned only with the search for the fundamental laws that describe the longest strands in the universe’s fabric. Convinced that these laws must be mathematically beautiful, he once–uncharacteristically– hazarded the unverifiable conjecture that ‘God is mathematician of a very high order.’2
The ambitions of Kurt Hofer were more modest than Dirac’s. Hofer had made his name in cancer and radiation research by carefully carrying out experiments and then trying to find theories to explain the results. This was the conventional, bottom-up technique of the English naturalist Charles Darwin, who saw his mind ‘as a machine for grinding general laws out of large collections of facts’.3 Dirac, a classic example of a top-down thinker, took the opposite approach, viewing his mind as a device for conjuring laws that explained experimental observations. In one of his greatest achievements, Dirac used this method to arrange what had seemed an unlikely marriage – between quantum mechanics and Einstein’s theory of relativity – in the form of an exquisitely beautiful equation to describe the electron. Soon afterwards, with no experimental clues to prompt him, he used his equation to predict the existence of antimatter, previously unknown particles with the same mass as the corresponding particles of matter but with the opposite charge. The success of this prediction is, by wide agreement, one of most outstanding triumphs of theoretical physics. Today, according to the cosmologists’ standard theory of the early universe – supported by a wealth of observational evidence – antimatter made up half the material generated at the beginning of the Big Bang; from this perspective, Dirac was the first person to glimpse the other half of the early universe, entirely through the power of reason.
Hofer liked to compare Dirac with Darwin: both English, both uncomfortable in the public eye, both responsible for changing the way scientists think about the universe. A decade before, Hofer was amazed when he heard that Dirac was to move from one of the world’s leading physics departments, at the University of Cambridge in England, to take up a position at Florida State University, whose physics department was ranked only eighty-third in the USA. When the possibility of his appointment was first mooted, there were murmurings among the professors that it was unwise to offer a post to an old man. The objections ended only after the Head of Department declared at a faculty meeting: ‘To have Dirac here would be like the English faculty recruiting Shakespeare.’4
Around 1978, Hofer and his wife Ridy began to pay visits to the Diracs on most Friday afternoons, to wind down for a couple of hours after the week’s work. The Hofers set off from their home near the campus in Tallahassee at about 4.30 p.m. and took the two-minute walk to 223 Chapel Drive, where the Diracs lived in a modest, single-storey house, a few paces from the quiet residential street. At the front of the house was a flat, English-style lawn, planted with a few shrubs and a Pindo palm tree. The Hofers were always welcomed warmly by Dirac’s smartly dressed wife Manci, who laughed and joked as she dispensed sherry, nuts and the latest faculty gossip. Dirac was painfully spare and round-shouldered, dressed casually in an open-necked shirt and an old pair of trousers, content to sit and listen to the conversation around him, pausing occasionally to sip his glass of water or ginger ale. The chatter ranged widely from family matters to local politics at the university, and from the earnest utterances of Mrs Thatcher on the steps of Downing Street to the most recent sermon from Jimmy Carter in the White House garden. Although Dirac was benign and receptive during these conversations, he was so reserved that Hofer often found himself trying to elicit a response from him – a nod or a shake of the head, a few words, anything to make the conversation less one-sided. Just occasionally, Dirac would be moved to contribute a few words about one of his private enthusiasms – Chopin’s waltzes, Mickey Mouse and any television special featuring Cher, the brassy chanteuse.
During the first two years or so of these visits, Dirac showed no sign of wanting to talk about himself or of having any deep feelings, so Hofer was ill prepared when, one Friday evening in the spring of 1980, Dirac’s vacuum-packed emotions burst into the open. ‘I remember it well. It was pretty much like all my other visits except that I was alone,’ Hofer says. ‘My wife decided not to come as she was tired, heavily pregnant with our first child.’ At the beginning of the visit, Dirac behaved normally and looked alert a
nd ready to absorb the conversations around him. After the customary pleasantries, the Diracs took Hofer by surprise when they ushered him through the formal front room – where they always talked during their Friday chats – to the less formal family room at the rear of the house, adjoining the kitchen and overlooking the garden. The Diracs’ pre-war taste was reflected in the decor of this room, dominated by the wood of the floorboards, the panelling on all four walls, and the huge 1920s sideboard covered with framed photographs of Dirac in his prime. A mock-Baroque chandelier hung from the ceiling and, on most of the walls, there were paintings with no trace of modernity.
As usual, Manci and Hofer chatted convivially while the frail Dirac sat motionless in his favourite old chair, occasionally looking through the glass sliding doors to the garden. For the first half an hour or so of the conversation, he was, as usual, mute but came vibrantly to life when Manci happened to mention his distant French ancestors. Dirac corrected one of Manci’s historical facts and began to speak about his family origins and his childhood in Bristol, talking fluently in his quiet, clear voice. Like a well-rehearsed actor, he spoke confidently, in carefully articulated sentences, without pausing or correcting himself. ‘I was startled – for some reason, he had decided to take me into his confidence,’ Hofer says. ‘I’d never seen him talk so eloquently in private.’
Dirac described his roots in the rural villages of Bordeaux, in western France, and how his family migrated to the Swiss canton of Valais at the end of the eighteenth century. It was in Monthey, one of the region’s industrial towns, that his father was born. As soon as Dirac began to talk about his father, he became agitated, and he turned away from his wife and Hofer, adjusting his pose so that he was staring straight into the fireplace. Hofer was now looking directly at the profile of the top half of Dirac’s body: his hunched shoulders, his high forehead, his straight and upward-pointing nose, his white smudge of a moustache. The air conditioning and television were switched off, so the room was silent except for the occasional rumblings of traffic, the barking of neighbourhood dogs, the rattling of the lid on the simmering casserole in the kitchen. After spelling out his ancestry with the precision of a genealogist, Dirac reached the part of his story where his father arrived in Bristol, married Dirac’s mother and started a family. His language remained simple and direct, but, as he began to talk about his childhood, his voice tightened. Hofer, watching Dirac’s silhouette sharpen with the fading of the early evening light, was transfixed.
‘I never knew love or affection when I was a child,’ Dirac said, the normally neutral tone of his voice perceptibly tinged with sorrow. One of his main regrets was that he, his brother and younger sister had no social life but spent most of their time indoors: ‘we never had any visitors’. The family was dominated, Dirac recalled, by his father, a tyrant who bullied his wife, day in, day out, and insisted that their three children speak to him in his native French, never in English. At mealtimes, the family split into two: his mother and siblings would eat in the kitchen and speak in English, while Dirac sat in the dining room with his father, speaking only in French. This made every meal an ordeal for Dirac: he had no talent for languages, and his father was an unforgiving teacher. Whenever Dirac made a slip – a mispronunciation, a wrongly gendered noun, a botched subjunctive – his father made it a rule to refuse his next request. This caused the young Dirac terrible distress. Even at that time, he had digestive problems and often felt sick when he was eating, but his father would refuse him permission to leave the table if he had made a linguistic error. Dirac would then have no option but to sit still and vomit. This did not happen just occasionally, but over and over again, for years.
Hofer was aghast, scarcely able to believe his ears. ‘I felt extremely embarrassed, like I was witnessing a friend pouring out his most terrible secrets to his psychiatrist,’ he recalls. ‘Here he was, a man famous for equability and his almost pathological reticence, openly talking of the demons that had haunted him for nearly seventy years. And he was as angry as if these awful events had happened yesterday.’
Manci barely stirred, except once to bring food and alcohol and to slow down the preparations for dinner. She knew that on the very rare occasions her husband chose to tell his story, it was best to keep well out of his way and to let him get it off his chest. As the evening turned colder, she brought him a blanket and draped it over his legs, covering him from his lap down to his ankles. Hofer braced himself as Dirac resumed and explained why he was so quiet, so ill at ease with normal conversation: ‘Since I found that I couldn’t express myself in French, it was better for me to stay silent.’
Dirac then moved on to talk about other members of his family: ‘I was not the only one to suffer,’ he said, still agitated. For thirty-seven years, his mother was locked in a disastrous marriage to a man who treated her like a doormat. But it was Dirac’s brother who felt the brunt of their father’s insensitivity: ‘It was a tragedy. My father bullied him and frustrated his ambitions at every turn.’ In what appeared to be a change of tack, Dirac mentioned that his father always appreciated the importance of a good education and that he was respected by his colleagues as a conscientious, hard worker. But this was only a brief respite. Seconds later, Dirac was struggling to control his rage when he spelt out the conclusion he eventually reached about the extent of his debt to his father: ‘I owe him absolutely nothing.’ That final rasp made Hofer flinch; he could not help but grimace. Dirac hardly ever spoke an unkind word about anyone, but here he was, denouncing his own father with a vehemence most people reserve for the cruellest abusers.
Dirac stopped talking abruptly, just after nightfall. His monologue had lasted over two hours. Hofer knew that any words from him would be inappropriate, so he said his subdued goodbyes and walked home, numb and drained. Soon to be a father himself, he reflected on his own youth as part of a close and loving family: ‘I simply could not conceive of any childhood as dreadful as Dirac’s.’5 Time tends to embellish, distort and even create childhood memories: could it be that Dirac – usually as literal-minded as a computer – was exaggerating? Hofer could not help asking himself, over and again: ‘Why was Paul so bitter, so obsessed with his father?’
Later that night, after talking with his wife Ridy about Dirac’s account of his young life, Hofer made up his mind to find out more about it. ‘I thought he might open up again during our later get-togethers.’ But Dirac never mentioned the subject again.
Notes-Prologue
1 A version of the ‘more people who prefer to speak than to listen’ remark, one of Dirac’s favourites, is cited by Eugene Wigner in Mehra (1973: 819).
2 Dirac made the ‘God is a mathematician’ remark in his Scientific American article in May 1963.
3 The quote from Darwin is taken from Part VII of his autobiography. The words were written on 1 May 1881.
4 The author of the quote relating to Shakespeare was the late Joe Lannutti, a leading member of the Physics Department at Florida State University when Dirac arrived. The source of the quote is Peggy Lannutti, interview 25 February 2004. Lannutti also tells the story in J. Lannutti (1987) ‘Eulogy of Paul A. M. Dirac’ in Taylor (1987: 44–5).
5 This account is taken from interviews with Kurt Hofer on 21 February 2004 and 25 February 2006, and many subsequent e-mails. The account was checked in detail via e-mails on 22 September 2007. Hofer’s recollections are consistent in every detail with the account given by Dirac in Salaman and Salaman (1986), in his interview, AHQP, 1 April 1962 (pp. 5–6), and in the account he gave of his early life to his friends Leopold Halpern and Nandor Balázs. I spoke to these former colleagues of Dirac on 18 February 2003 and 24 July 2002, respectively. Dirac’s wife gives her recollections of his experiences at the dining table in her letter to Rudolf Peierls, 8 July 1986, Peierls archive, additional papers, D23 (BOD).
One
English home life to-day is neither honorable, virtuous, wholesome, sweet, clean, nor in any creditable way distinctively English. It is
in many respects conspicuously the reverse […].
GEORGE BERNARD SHAW, Preface to Getting Married, 1908
As Kurt Hofer had seen, the elderly Paul Dirac was fixated on his father Charles. But most of Dirac’s acquaintances knew nothing of this: at home, he allowed no photographs of his father to be displayed, and he kept his father’s papers locked in his desk. Dirac examined them from time to time and talked with distant relatives about his father’s origins, apparently still trying to understand the man he believed had blighted his life.1
Dirac knew that his father had endured a childhood no less miserable than his own. By the time Charles Dirac was twenty, in 1888, he had done three stints of national service in the Swiss army, dropped out of university in Geneva and left home, without telling his family where he was heading.2 He became an itinerant teacher of modern languages – the subject he had studied at university – and held posts in Zurich, Munich and Paris, before he fetched up two years later in London. English was one language that he did not speak well, so it is not clear why he chose to live in Britain; perhaps it was because it was the world’s wealthiest economy, with plenty of teaching jobs at relatively high salaries.
Six years later, Charles Dirac had acquired a sheaf of complimentary references. One, written by the headmaster of a school in Stafford, stated that Monsieur Dirac ‘is possessed of very great patience combined with firmness […] I believe he is much liked both by his colleagues and pupils.’ His employer in Paris had praised ‘his capacity to analyze and generalize, which enabled him to point out my mistakes and help me to ascertain scientifically why they were mistakes’. Charles settled in Bristol, a city famous for the high quality of its schools, and he became Head of Modern Languages at the rapidly expanding Merchant Venturers’ School on 8 September 1896, contracted to teach thirty-four hours a week for an annual salary of one hundred and eighty pounds.3 He stood out among the teachers because of his conscientiousness, his thick Swiss-French accent and his appearance: a short, stocky, slow-moving man with a drooping moustache, a receding hairline and a face dominated by a huge forehead.