HENRY CAVENDISH (1731-1810)
Every evening in the last years of the eighteenth century, at precisely the same hour, a solitary figure stepped forth from the most unusual house on Clapham Common to take his nightly constitutional. To avoid the prying eyes of his neighbours, he stuck to the middle of the road, never hailing those who recognized him or touching his hat to acknowledge passersby. Dressed in fussy clothes that had last been in fashion decades earlier, he walked with a distinctive slouching gait, his left hand held behind his back. His route, like his departure time, never varied. He would proceed down Dragmire Lane to Nightingale Lane and walk for another mile, past quiet townhouses and rows of oak and hawthorn trees until he arrived at Wandsworth Common. Then he would walk back the way he came.
He had made only one revision to this itinerary in a quarter of a century, after attracting the attention of two women who planted themselves at a corner where they were likely to catch sight of him. Spotting them from some distance away, he abruptly launched himself in the perpendicular direction, making an undignified but effective escape through the muck of a freshly plowed field. After that, he scheduled his walks after dusk, when he was least likely to be seen.
He guarded his precious solitude within the boundaries of his estate as rigorously as he did outside them, communicating with his household staff in notes left on a hall table. A maid wielding a broom once made the error of surprising him in a stairwell, and his swift response was to order the construction of the second set of steps at the rear of the residence to prevent such an incident from ever happening again.
His neighbours in this rustic London suburb knew little about his solitary labour in the shed beside his house that would one day make his name immortal. Rumours were going around Clapham that he was some sort of wizard. Admittedly, the most striking feature of his estate did not help to dispel those rumours. From a little hillock in the yard, an eight-foot pole projected into the sky, like a ship’s mast rising from dry land.
By declining to sit for a formal portrait – usually a de rigueur concession for a man of his station – he nearly managed to block out the inquisitive gazes of historians from the future. The sole image of Henry Cavendish captured in his life shows an aristocratic-looking man in a frock coat, frilled shirt-wrists, and white stockings, wearing a knocker-tailed periwig under a black three-cornered hat. This was s defiantly unchic style of dress even in the late 1700s, and he wore the same outfit every day of his adult life. Each year, when his coat – always the same shade of grey-green or violet – was on the verge of fading, he would prompt his tailor to sew up another one, identical to the first.
He was equally consistent in his dining habits. Though his personal fortune could have afforded him an ever-changing banquet of exotic delicacies shipped from the farthest reaches of the empire, he subsisted for decades on the same humble dish at nearly every meal: leg of mutton. Once a week, when he took supper with his colleagues at the Royal Society Club, he invariably sat at the same chair, after hanging his hat and coat from a peg that may as well have had a plaque beside it engraved with his name.
That’s how a sly young draftsman named William Alexander finally succeeded in capturing his portrait – by acting like the Georgian equivalent of a paparazzo. After talking his way into the club, Alexander parked himself unobtrusively in a corner and sketched Cavendish’s hat and coat dangling from the inevitable peg. At a subsequent meal, he drew his subject’s face as he prepared to tuck into his dish of mutton. Then the artist combined the two images, yielding a composite portrait of the complete man.
Cavendish’s inflexible routines and unvarying timetables were no more subject to amendment than the tides of the Portsmouth harbour. On one rare occasion when he invited four Royal Society colleagues to dine with him in Clapham, a cook boldly ventured to suggest that a leg of mutton would hardly provide an adequate repast for five men. He replied, with a characteristic terseness, “Well, then, get two.”
Despite his eccentric couture and the strange totem rising from his backyard, Henry Cavendish was not a wizard. He was, in eighteenth-century terms, a natural philosopher, or what we now call a scientist. (The word scientist wasn’t coined until the nineteenth century when it was proposed as a counterpart to the artist by oceanographer and poet Willian Whewell.) He was not only one of the most ingenious natural philosophers who ever lived, he was one of the first true scientists in the modern sense.
His tireless explorations ranged across an entire university’s worth of disciplines, encompassing chemistry, math, physics, astronomy, metallurgy, meteorology, pharmacy, and a few fields that he pioneered on his own. In an age when data mining the Lord’s creation was not yet regarded as a legitimate profession but more like an enlightened hobby, he defined the scope, conduct, and ambition of the scientific method for centuries to come.
The first surviving account of his work in the lab, a sheaf of papers dated 1764, details his study of arsenic and its metamorphosis into an off-white powder called “arsenical salt,” now known as potassium arsenate. Like most of his peers, Cavendish. believed that the hidden agent of this transformation was phlogiston, an element akin to fire. By understanding this element, he hoped to discover a key to many types of chemical reactions. The phlogiston hypothesis turned out to be bunk – and he quickly abandoned it – but his observations in the lab were so astute that he anticipated the synthesis of potassium arsenate in ten years, using a simpler method that the man given credit for that discovery, pharmacist Carl William Scheele. Unlike Scheele, however, Cavendish neglected to issue the equivalent of a press release, so he got none of the credit – while Scheele became famous by popularizing an inferior method of synthesis.
Cavendish’s next major breakthrough was in the study of the atmosphere. A late bloomer in the journals compared to his peers, he didn’t even submit his first paper for publication until age thirty-five, chronicling his discovery of an unstable gas he called “inflammable air” – the element now known as hydrogen, the basic building block of the universe. He then determined the composition of water by using a spark of electricity to combine this new gas and “dephlogisticated” air – oxygen. When he removed the nitrogen and oxygen from a flask in his lab, he noticed that a tiny bubble of a third gas remained. In that bubble was the element argon, which wouldn’t be officially discovered for another hundred years.
Scores of equally bold experiments followed. Cavendish analyzed the mathematics of musical intervals, formulated the theory of electrical potential, and was the first scientist to realize that a solution’s electrical conductivity varies with its concentration. He proposed that a long-tailed fish called the torpedo was able to generate its current like a living battery, and then proved it by sculpting an artificial fish in his lab out of shoe leather, pewter plates, glass tubes, and sheepskin and hooking it up to Leydin jars, creating a perfect simulation of the fish’s electrical organs.
In 1769, lightning struck the steeple of the church of San Nazaro in Brescia, an ancient Roman city built at the foot of the Alps. The massive high-voltage pulse was conducted through the walls of the sanctuary to the basement, where the Venetian army had inconveniently stored one hundred tons of gunpowder. The resulting blast killed 3,000 people, knocking one-sixth of the city flat. To prevent a similar fate from befalling the British army’s powder cache in its arsenal at Purfleet, the Royal Society appointed Lord Henry to the “lightning committee” assigned to studying ways of insulating it. Among the foreign dignitaries who came along on that trip was a natural philosopher from the thirteen colonies who knew a thing or two about electricity himself – Benjamin Franklin.
The lightning committee devised a crafty plan, based on Cavendish’s prescient theories of electricity, to surround a warehouse with metal rods, tipped with copper conductors, to draw impertinent discharges away from the unstable powder. While his paper on electrical theory was dismissed as too abstruse during his lifetime, two years after his death, a Royal Society historian declared it “the most rigid and satisfactory explanation of the phenomena of electricity . . . beyond dispute, the most important treatise on the subject that has ever been published.”
Cavendish submitted only a fraction of his work to the Royal Society journal, Philosophical Transactions. But he was an exhaustive chronicler of his research, churning out an endless stream of carefully annotated tables, charts, graphs, and notebooks that only a small circle of his colleagues ever saw. He prized the open and egalitarian sharing of data but felt no compulsion to take credit for his discoveries. He preferred to avoid competition and controversy and simply wanted to perform his experiments in peace.
As a result, the formula that describes the flow of electrical current as a function of resistance is known as Ohm’s law rather than Cavendish’s law, though he anticipated the Bavarian physicist by a century. Likewise, a law describing the electrostatic interaction between charged particles – the foundation of modern electromagnetic theory – is synonymous with the name of the French physicist Charles Augustin de Coulomb, though Cavendish thought of it first. His seminal discovery that water was not a monolithic element but composed of hydrogen and water is usually attributed to Antoine Lavoisier. Once again, Cavendish had figured this out earlier but neglected to make a fuss about it, unlike the grandiose Lavoisier, who invited members of the Royal Academy to assist him in a public demonstration. Thus it is Lavoisier, rather than Cavendish, who is hailed as the father of modern chemistry.
Cavendish may have dressed like a man from the past, but he lived like one from the future. If he had been born three centuries later, he would have been hailed as a visionary “maker” – a hacker who isn’t afraid to get his hands dirty in a machine shop.
To say that Cavendish’s distaste for hype and self-promotion extended to his personal life would be an understatement. The statesman Lord Henry Brougham observed in 1845 that his taciturn colleague “uttered fewer words in the course of his life than any man who lived to fourscore years, not at all excepting the monks of La Trappe.”
The source of this apparent shyness was social anxiety so intense that it nearly immobilized him in certain situations. Brougham described his face as “intelligent and mild, though, from the nervous irritation which he seemed to feel, the expression could hardly be called calm.” At weekly gatherings of his colleagues hosted by the Royal Society president Joseph Banks, he would pause outside on the stoop, hesitant to knock on the door, until the arrival or departure of another guest forced him to go in.
On one such occasion, he was introduced to a fan from Austria who regaled him with fulsome praise. Cavendish stood silent, eyes downcast until he spotted an opening in the crowd, at which point he bolted from the room and leaped into his carriage, which carried him directly home. His anxiety may have been exacerbated by the fact that the intonations of his voice struck others as odd and displeasing – “squeaking,” and “even to articulate with difficulty.” Another colleague described him uttering a “shrill cry” at Royal Society meetings as he “shuffled quickly from room to room” to avoid being directly engaged. Cavendish was particularly discomfited if anyone tried to catch his eye.
It is not true, however, that he wanted to remove himself entirely from the company of his peers; he just wanted to stand off to the side, soaking everything in, a hunched figure in a gray-green coat lurking in the shadows, listening intently. Eager to solicit his appraisal of their work, his fellow natural philosophers devised a devious but effective method of drawing him into an exchange.
“The way to talk to Cavendish is never to look at him,” said astronomer Francis Wollaston, “but to talk as it were into a vacancy, and then it is not unlikely but you may set him going.” Once he was set going, it turned out that he had plenty to say. “if he speaks to you, continue the conversation. He is full of information, particularly as to chemistry.”
One of the few people that Lord Henry welcomed into the innermost precincts of his life was Charles Blagdon. He was relentlessly curious, was scrupulous in the conduct of his experiments, and had an indelible memory for facts. But Blagdon was also an avid reader, linguist, and conversationalist who maintained a thriving correspondence with researchers and explorers all over the world.
Together, the two men forged a mutually indispensable alliance. Cavendish became Blagden’s human Google, answering any query that came up in his work. The elder scientist’s guiding hand was visible in six of the ten papers that Blagdon published. In return, the reclusive lord was able to keep up with the state of his art without having to schmooze his way through the 18th-century equivalent of TED conferences. Through Blagdon, his life was richly interwoven with the lives and work of a global community of thinkers who were kept at a safe and comfortable distance.
Partly owing to Cavendish’s great wealth, his preference for solitude was often confused with arrogance, selfishness, or disdain. A fellow scientist once described him as “the coldest and most indifferent of mortals,” while others characterized him as insensitive, blind to the emotions of others, or mean. But he was not a nasty or vindictive man; he simply had no idea how to conduct himself in public. Cavendish described his behaviour by saying that some men lack “certain feelings.” Blagden sympathetically described his mentor as a man of “no affections” who nonetheless “always meant well.”
The chemist George Wilson wrote the first full-length biography of Cavendish in 1851. Appraising his subject’s seeming lack of interest in anything but science, he painted Cavindish’s emotional life as a series of negations: “He did not love, he did not hate, he did not hope, he did not fear . . . His brain seems to have been but a calculating engine . . . He was not a Poet, a Priest, or a Prophet, but only a cold, clear intelligence, raying down pure white light, which brightened everything on which it fell, but warmed nothing.”
Cavendish’s reserve made it possible for him to conduct his research with single-minded intensity. He was not self-absorbed, he was the opposite. He was wholly engaged in his study of nature, which provided its own form of communion – if not with the souls of other people, then with the hidden forces behind the visible face of things.
The kingdom of natural philosophy that Cavendish built at Clapham Common was an extraordinary resource for any scientist in any century – a house transformed into a vast apparatus for interrogating the mysteries of existence.
First noticed would be the 80-foot pole aimed at the sky, supported by huge struts near the base. It was a towering mount for one of Cavendish’s telescopes, part of his plan to convert the upper floor into an astral observatory, complete with a transit room for recording the positions of stars as they traversed the meridian.
He turned the downstairs drawing room into a lab, installing a furnace, crucible, and fume hood, and stocking it with hundreds of beakers, flasks, pipes, and balances. In an adjoining room, he built a forge. Cavendish’s passion for precision was manifest in the astonishing variety of measuring instruments – barometers, clocks, sundials, compasses, and rain gauges – arrayed throughout the house and grounds. When he took a road trip with Blagdon, say to visit a factory to take notes on the production of iron, he affixed a primitive odometer called a “way-wiser” to the wheels of his carriage, so they would know precisely how many miles they had travelled. He also brought along a thermometer to take the temperature of any wells they happened to pass.
The thermometers of the day could differ by their readings of the boiling point of water by two or three degrees. To the roster of the servants at Clapham, he added a dedicated instrument maker. His cabinets were filled with custom-made rulers, scales, triangles, maps, and other measuring devices fashioned of wood and brass. Scaffolding outside the house served as a mount for meteorological instruments. No potential source of data on the estate was wasted – not the wind, the rain, the passages of sunlight through the garden nor the weight of damp air collecting in the branches of the oaks.
Even the front yard had a wooden stage, from which access could be had to a large tree, to the top of which Cavendish, in the course of his astronomical, meteorological, electrical, or other researches occasionally ascended. Six years after his death, when the last of his gear went on auction after being thoroughly picked over by his colleagues, eleven telescopes and forty-four thermometers were still available.
His emotional life was out of view – no revealing diary entries, telling admissions, or confessions of unrequited yearning have come to light in his letters which are predictably focused on the science and the minutiae of his mundane affairs. With colleagues, anything beyond a working relationship was perpetually out of reach. He encouraged no intimacy with anyone but was still described as “a great man, with extraordinary singularities.”
Yet he can hardly be considered barren or bereft of fulfillment. He transformed his whole environment into a playground for his keenly focused senses and intellect. Charles Darwin once described his own brain as a machine for churning out hypotheses. Cavendish’s was an engine for generating finely calibrated distinctions: this, but not that. His analysis of a single substance could yield volumes of rhapsodic description.
His modern-day biographers, Christa Jungnickel and Russell McCormack wrote in Cavendish: The Experimental Life:
By smell, he distinguished between the various acids and their products. He felt and observed textures: dry, hard, thin jelly, gluey, thick, stiff mud, lump. With colours, he made the greatest number of distinctions: milky, cloudy, yellow, pale straw, reddish-yellow, pale Madeira, red, reddish-brown, dirty red, green, bluish-green, pearl colour, blue, transparent, turgid, and muddy. No poet paid greater attention to his sensations than Cavendish did to his.
One house-sized laboratory alone turned out to be insufficient to meet his research needs. He also turned a handsome three-story brick residence at No. 11 Bedford Square in London into a private library worthy of his alma mater, Cambridge. Contrary to the notion that he was an ungenerous man, Cavendish made his library’s holdings freely available to fellow scholars. Visitors were furnished with a catalogue, an on-site librarian to help them navigate the stacks, and a ledger for keeping track of checked-out items. (He dutifully entered the books he took home himself into the ledger.) Decorated in green like his founder’s beloved coat – with jade curtains, jade slipcovers, and fireplace screens of emerald silk – the library even boasted a prototype copier machine designed by James Watt. Etchings of the moon’s surface were featured on the walls, like an exhibit from the 20th century. There was even a special “museum” hall where he showed off his beloved collection of rare minerals.
Predictably, what was not on offer at No. 11 was an audience with the proprietor himself. Prospective borrowers were instructed not to disturb Cavendish and to promptly hasten home with their selections. Obviously, he wasn’t much for people, as another socially inept genius, Albert Einstein, observed about himself.
But to describe Cavendish as a man of no affections, or a passionless man also misses the mark. His life was devoted to one single, all-consuming passion: the slow and patient increase in the sum of human knowledge. His mind was like a mirror held up to nature, unclouded by bias, rationalization, lust, jealousy, competition, pettiness, rancour, ego, and faith. The vocation to which he considered himself called was, to weigh, number, and measure as many objects as he could in a lifetime.
The virtuoso act of measurement that inscribed his name indelibly into history is now known simply as the Cavendish experiment. Its goal was as lofty as the apparatus it required was simple. Using four lead spheres, some rods, and a length of wire, he built a device to measure the density of Earth. The key to its cunning design was the correspondence between the mass of an object and its gravitational force.
Two of the spheres weighed 350 pounds, while the others 1.6 pounds each. By attaching the lighter spheres to the ends of a wooden rod suspended on a wire, mounting the heavier spheres a few inches away, and setting the rod in motion like a pendulum, Cavendish contrived to gauge the torque of the wire as it oscillated. He hoped this would enable him to calculate the magnitude of the force acting on the spheres using Newton’s law of universal gravitation and thus determine the density of the planet. It was an ambitious scheme, and Newton himself was doubtful as the attraction between the two spheres would be so minute that it would be swamped by the tidal attraction of Earth’s mass. Newton was correct that the attraction between the spheres was very slight (just one part in 10 compared to the Earth’s gravity), but he underestimated what a man like Cavendish could pull off through sheer dogged persistence. First, he built a stand-alone shed in his backyard to isolate the delicate oscillations of the mechanism from stray drafts and vibrations. Then he sealed the apparatus itself in a mahogany box and rigged up a system of pulleys so he could set the pendulum going without touching it. To calculate the forces acting on the spheres, he installed telescopes at both ends of the box, focusing them on vernier scales inside the chamber that enabled him to calculate torque to within 0.01 inch.
Working solo, he began his rounds of measurements at the height of summer on August 5, 1797. (He was 66 at the time). Over and over, he set the pendulum swinging, took his position at the telescopes, and recorded observations in a notebook. For months, he diligently applied himself to this single task, finally wrapping up his epic series in May.
Ironically, Cavendish made a minor error of addition in his report throwing off the results by a fraction of a percent. But the figure he came up with was so close to the actual density of Earth that no researcher could best it for another hundred years. As a side benefit, his experiment indirectly provided the first estimate of the gravitational constant, known among physicists as “Big G,” which also turned out to be astonishingly accurate. Cavendish’s experiment is now recognized as the inaugural moment of modern physics, laying the groundwork for centuries of breakthroughs to come, including Einstein’s theories of relativity.
It was also his last major foray into science. On February 24, 1810, Cavendish succumbed to an inflammation of the colon with no panic or drama, leaving the lion’s share of his fortune to his nephew, George. Even in death, he guarded the solitude that had enabled him to accomplish so much. His final instructions to his servants were to summon his young heir only after he had drawn his last breath and to leave him alone so that he could spend his final moments in peace.
A few days after Cavendish’s death, Blagden paid tribute to his mentor by describing him as a s “true anchor” who could “always depend on knowing what was right for him.” It was a fitting eulogy for a man who lived completely on his own terms but benefited everyone by doing so. The great house on Clapham is gone now, replaced in 1905 by rows of brick villas.
His last experiment brought him more fame after death than he ever sought in his lifetime. For decades after his internment in the family crypt in the All Saints’ Church north of London, mothers would pause reverently before his yard, point to his abandoned shed, and tell their children, “On this spot, a man called Henry Cavendish weighed the world.”
The extraordinary singularities of this solitary pioneer were a source of perpetual puzzlement and frustration to his colleagues. But the theories proposed to explain his eccentricities over the years have often felt provisional or incomplete as if some crucial data point was missing.
The word invoked most often to make sense of his behaviour is shy. His contemporaries described him as “excessively shy,” “peculiarly shy,” and even “shy and bashful to a degree bordering on disease.” But mere shyness doesn’t explain the overall oddity of his conduct, such as his adherence to rigid timetables, his insistence on wearing only one outfit for decades, and his habit of listening obliquely to conversations rather than talking face-to-face.
In Jungnickel and McCormmach’s magisterial biography “The Problem with Cavendish,” it was a knotty conundrum and never did lay the enigma to rest. “He appears simply strange, an object of curiosity at best, of moral judgment at worst, drawing pity or scorn. To leave him that was unnecessary is a shame. He was an outstanding scientist and one of the most baffling personalities in the history of science. A fuller understanding of him benefits both his biography and the history of science.
Some of his peers ventured to suggest that he had a pathological fear of women. Psychoanalytically minded pundits speculated that Cavendish may have been traumatized as a child by the death of his mother. But she died before his second birthday, and his brother, Frederick, grew up to become an affable extrovert. The peculiarities must be referred much more to original conformation, than to anything else.
Blagdon said his preference for solitude had been established at a very young age. Some historians have proposed that he didn’t get along with his father, Lord Charles, a prominent Whig and noted natural philosopher himself. But he showed every sign of being lovingly devoted to his son. As a boy, Charles encouraged him to conduct measurements of Earth’s magnetic field in the garden of the house they shared for 30 years. After Henry returned from Cambridge, his father built him a lab so that his life’s work could begin in earnest. Charles surrounded him with potential mentors by hosting Royal Society dinners, channelling his son’s intellect into science. Finally, his last gift to him – a sizable fortune – enabled Henry to live for the rest of his life in a private world that was perfectly suited to his needs.
Cavendish was clearly an extraordinary man, fortunate to be born into a family of extraordinary means. Otherwise, one of the greatest scientists in history might have ended up in a ward at Bethlem Royal Hospital (commonly known as “Bedlam”), enduring the regimen of cold baths in vogue for the treatment of “withdrawn” patients at the time.
Few Nobel laureates have much resembled the Renaissance ideal – the suave and supremely well-rounded human being equally accomplished in the rigours of the lab, the aesthetics of the atelier, and the art of scintillating conversation. Instead, they have tended to be persnickety oddballs in ill-tailored suits, sensible dresses, and rumpled cardigans, ruling deep domains of expertise with slide rules and unwavering commitments to accuracy. In many ways, the father of modern physics and the awkward prodigy who helped lead the field into the quantum era were kindred spirits born two centuries apart.
In 2001, neurologist Oliver Sachs proposed that he had uncovered the elusive solution to the problem of Cavendish in a condition that had fascinated him for decades. Writing to his peers in the journal Neurology, he observed that accounts of the reclusive lord are seemingly inexplicable idiosyncrasies – his “striking literalness and directness of mind, extreme single-mindedness, [and] passion for calculation and quantitative exactitude . . . coupled with a virtual incomprehension of social behaviours and human relationships” – closely resembled descriptions of adults with a type of autism called Asperger’s syndrome, first described in the 1994 edition of the Diagnostic and Statistical Manual of Mental Disorders. Sacks also pointed out, however, that it was precisely these qualities that made Cavendish such a brilliant and prolific researcher. His singularities were inextricable from his genius.
Sachs stated firmly that he was not just jumping on the bandwagon of retro diagnosing famous geeks from history with a trendy disorder. In the case of Cavendish, he found the evidence for an Asperger’s diagnosis “almost overwhelming.”
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PAUL DIRAC (1902-1984)
Raised in humbler circumstances than his posh Georgian predecessor, Paul Dirac grew up in Brighton, the son of a librarian and a tyrannical strict French teacher. His classmates remember him as a tall, quiet, “un-English-looking” boy in unfashionable knickerbockers who virtually lived in the library, maintaining a “monomaniacal focus” on science while seeking refuge from his father’s pedantry in adventure novels and comic books.
His uncanny aptitude for math showed itself early. A teacher once sent young Dirac home with a set of problems designed to keep him occupied all evening and was shocked when he had solved them by the afternoon. Even as a boy, he preferred a life of contemplation to the hurly-burly of the schoolyard. When he was nine, his teachers at the Bishop Road School awarded him with a telling prize: a copy of Daniel Defoe’s Robinson Crusoe, the fictional autobiography of a castaway marooned for twenty-eight years on a remote island.
Lacking an aristocratic father to introduce him to potential mentors in science, Dirac trained at a technical school to become an electrical engineer. In his first year, he distinguished himself so highly that Cambridge offered him a scholarship to its prestigious math program. At St. John’s College, his diffidence and taciturnity became “the stuff of legend,” writes Graham Farmelo in a biography of the physicist The Strangest Man. The newly matriculated Dirac would sit stiffly in the dining hall, hesitant to ask the person eating beside him to pass the salt and greeting every question posed to him with blank silence or a stark yes or no. Incapable of bluffing his way through the protocols of polite conduct, he came across as cold, rude, disinterested, or uncaring, though he didn’t intend to.
A classmate once tried to break the ice with him by casually remarking, “It’s a bit rainy, isn’t it?” Dirac’s strictly empirical response was to march over to the window, peer out, return to his chair and reply “It is not now raining.” Inspired by his extreme verbal parsimony, his fellow students at St. John’s invented a unit of measurement for the number of words that a person might utter in conversation, christening the minimum rate one “Dirac” – one word per hour. But like Cavendish lurking in the shadows at the Monday Club, he would often eavesdrop inconspicuously as his peers swapped stories.
Oblivious to contemporary modes of dress, Dirac wore cheap, unstylish suits in all weathers until they were threadbare, even after securing a generous salary as the Lucasian Chair of Mathematics at Cambridge (the position later held by Steven Hawking). His mother practically had to beg him to buy a winter coat so she could stop fretting about his health. Though he seemed impervious to freezing temperatures, he was acutely sensitive to sounds – particularly the barking of dogs, which were permanently banned from his household. Dirac’s motor skills were notoriously poor; a classmate described his method of wielding a cricket bat as “peculiarly inept.” Yet he was as devoted as Cavendish was to taking long walks on a regimented timetable, holding his hands behind his back as he efficiently ticked off the miles in his “metronomic” stride.
In an era when physicists like Einstein and Max Planck were feted as international heroes in the press, Dirac had no interest in being a public figure. He routinely turned down honorary degrees because he felt they should be awarded strictly on merit, and he refused a knighthood because he didn’t want strangers chummily referring to him as “Sir Paul” rather than “Mr. Dirac.” Upon winning the Nobel in physics with Erwin Schrodinger in 1933, he told a reporter from a Swedish newspaper, “My work has no practical significance.”
His life path diverged from Cavendish in at least one important way: he married a bubbly Belgian extrovert named Margit Wigner – nicknamed “Manci” who urged him to supplement his pop-culture diet of comic books and Mickey Mouse cartoons with novels and occasional foray to the ballet. (As Farmelo puts it, “He had wed his anti-particle.”)
The newlyweds honeymooned in Brighton where the love-struck groom rigged up a camera with a string so he could click the shutter himself. In one shot, the gawky physicist reclines beside his bride on the beach, attired in his usual three-piece suit, with a thicket of pencils sprouting from his pocket. “You have made a wonderful alteration in my life. You have made me human,” Dirac gushed shortly after the wedding. This turned out to be an ongoing job. When Manci complained that he habitually ignored her questions, he pasted her queries into a spreadsheet and filled it in with his replies.
As a theoretical physicist, Dirac didn’t need a lab to do his work; all he needed was a pencil because his most finely calibrated instrument was his mind’s eye. When he was young, a teacher told him that she felt he was cogitating not in words but in “another medium of forms and figures.” He once described his own thoughts as essentially “geometrical.” While visiting an art gallery in Copenhagen, he turned to fellow Nobel laureate Niels Bor and said that he liked a certain painting because “the degree of inaccuracy is the same all over.” He told journalists who asked him to make sketches of his highly abstract concepts for their readers that they would melt away like “snowflakes” if he tried.
The breakthrough that assured him of his own eponymous place in history is known as the Dirac equation. Worked out on a scrap of paper at a schoolboy’s desk in his sparsely furnished room at St. John’s in less than a month in 1927, his formulate bridged a seemingly impassable gulf in physics by reconciling quantum mechanics and Einstein’s special relativity in a single concise line of variables. His equation also implied the existence of a previously unsuspected form of particle – antimatter – three years before a scientist named Carl Anderson glimpsed the ghostly arcs of positrons passing through a lead plate in his lab.
Dirac made only one miscalculation in the course of his career: understanding the practical applicability of his work. The relationships between matter and energy that he described made possible the development of semiconductors, transistors, integrated circuits, computers, handheld devices, and the other innovations in microelectronics that ushered in the digital age. By capturing the ephemeral snowflakes in his mind in the universal language of mathematics, this man who found communication so arduous a task made it much easier for everyone else to communicate.
But even in a field in which absentminded professors are the rule rather than the exception, Dirac’s colleagues were left unsettled and confused by his behaviour. Einstein confessed, “I have trouble with Dirac. This balancing on the dizzying path between genius and madness is awful.” Bohr claimed that Dirac was “the strangest man” he had ever met, finishing Farmelo with a title for his biography. Like Cavendish, he was a walking riddle to everyone who crossed his path.
Addition from Wikipedia:
Family. In 1937, Dirac married Margit Wigner (Eugene Wigner’s sister). He adopted Margit’s two children, Judith and Gabriel. Paul and Margit Dirac had two children together, both daughters, Mary Elizabeth and Florence Monica.
Margit, known as Manci, visited her brother in 1934 in Princeton, New Jersey, from their native Hungary and, while at dinner at the Annex Restaurant, met the “lonely-looking man at the next table”. This account from a Korean physicist, Y. S. Kim, who met and was influenced by Dirac, also says: “It is quite fortunate for the physics community that Manci took good care of our respected Paul A. M. Dirac. Dirac published eleven papers during the period 1939–46… Dirac was able to maintain his normal research productivity only because Manci was in charge of everything else”.
Personality. Dirac was known among his colleagues for his precise and taciturn nature. His colleagues in Cambridge jokingly defined a unit called a “dirac”, which was one word per hour. When Niels Bohr complained that he did not know how to finish a sentence in a scientific article he was writing, Dirac replied, “I was taught at school never to start a sentence without knowing the end of it.” He criticized the physicist J. Robert Oppenheimer’s interest in poetry: “The aim of science is to make difficult things understandable in a simpler way; the aim of poetry is to state simple things in an incomprehensible way. The two are incompatible.”
Dirac himself wrote in his diary during his postgraduate years that he concentrated solely on his research, and stopped only on Sundays when he took long strolls alone.
An anecdote recounted in a review of the 2009 biography tells of Werner Heisenberg and Dirac sailing on an ocean liner to a conference in Japan in August 1929. “Both still in their twenties, and unmarried, they made an odd couple. Heisenberg was a ladies’ man who constantly flirted and danced, while Dirac—’ an Edwardian geek’, as biographer Graham Farmelo puts it—suffered agonies if forced into any kind of socializing or small talk. ‘Why do you dance?’ Dirac asked his companion. ‘When there are nice girls, it is a pleasure,’ Heisenberg replied. Dirac pondered this notion, then blurted out: ‘But, Heisenberg, how do you know beforehand that the girls are nice?'”
Margit Dirac told both George Gamow and Anton Capri in the 1960s that her husband had said to a house visitor, “Allow me to present Wigner’s sister, who is now my wife.”
Another story told of Dirac is that when he first met the young Richard Feynman at a conference, he said after a long silence, “I have an equation. Do you have one too?”
After he presented a lecture at a conference, one colleague raised his hand and said: “I don’t understand the equation on the top-right-hand corner of the blackboard”. After a long silence, the moderator asked Dirac if he wanted to answer the question, to which Dirac replied: “That was not a question, it was a comment.”
Dirac was also noted for his personal modesty. He called the equation for the time evolution of a quantum-mechanical operator, which he was the first to write down, the “Heisenberg equation of motion”. Most physicists speak of Fermi–Dirac statistics for half-integer-spin particles and Bose–Einstein statistics for integer-spin particles. While lecturing later in life, Dirac always insisted on calling the former “Fermi statistics”. He referred to the latter as “Bose statistics” for reasons, he explained, of “symmetry”.
Views on religion. Heisenberg recollected a conversation among young participants at the 1927 Solvay Conference about Einstein and Planck’s views on religion between Wolfgang Pauli, Heisenberg, and Dirac. Dirac’s contribution was a criticism of the political purpose of religion, which Bohr regarded as quite lucid when hearing it from Heisenberg later. Among other things, Dirac said: I cannot understand why we idle discussing religion. If we are honest—and scientists have to be—we must admit that religion is a jumble of false assertions, with no basis in reality. The very idea of God is a product of the human imagination. It is quite understandable why primitive people, who were so much more exposed to the overpowering forces of nature than we are today, should have personified these forces in fear and trembling. But nowadays, when we understand so many natural processes, we have no need for such solutions. I can’t for the life of me see how the postulate of an Almighty God helps us in any way. What I do see is that this assumption leads to such unproductive questions as to why God allows so much misery and injustice, the exploitation of the poor by the rich, and all the other horrors He might have prevented. If religion is still being taught, it is by no means because its ideas still convince us, but simply because some of us want to keep the lower classes quiet. Quiet people are much easier to govern than clamorous and dissatisfied ones. They are also much easier to exploit. Religion is a kind of opium that allows a nation to lull itself into wishful dreams and so forget the injustices that are being perpetrated against the people. Hence the close alliance between those two great political forces, the State and the Church. Both need the illusion that a kindly God rewards—in heaven if not on earth—all those who have not risen up against injustice, who have done their duty quietly and uncomplainingly. That is precisely why the honest assertion that God is a mere product of the human imagination is branded as the worst of all mortal sins.
Heisenberg’s view was tolerant. Pauli, raised as a Catholic, had kept silent after some initial remarks, but when finally he was asked for his opinion, said: “Well, our friend Dirac has got a religion and its guiding principle is ‘There is no God, and Paul Dirac is His prophet. ‘” Everybody, including Dirac, burst into laughter.
Later in life, Dirac’s views towards the idea of God were less acerbic. As an author of an article appearing in the May 1963 edition of Scientific American, Dirac wrote:
It seems to be one of the fundamental features of nature that fundamental physical laws are described in terms of a mathematical theory of great beauty and power, needing quite a high standard of mathematics for one to understand it. You may wonder: Why is nature constructed along these lines? One can only answer that our present knowledge seems to show that nature is so constructed. We simply have to accept it. One could perhaps describe the situation by saying that God is a mathematician of a very high order, and He used very advanced mathematics in constructing the universe. Our feeble attempts at mathematics enable us to understand a bit of the universe, and as we proceed to develop higher and higher mathematics we can hope to understand the universe better.
In 1971, at a conference meeting, Dirac expressed his views on the existence of God. Dirac explained that the existence of God could be justified only if an improbable event were to have taken place in the past:
It could be that it is extremely difficult to start life. It might be that it is so difficult to start a life that it has happened only once among all the planets… Let us consider, just as a conjecture, that the chance of life starting when we have suitable physical conditions is 10−100. I don’t have any logical reason for proposing this figure, I just want you to consider it as a possibility. Under those conditions … it is almost certain that life would not have started. And I feel that under those conditions it will be necessary to assume the existence of a god to start off life. I would like, therefore, to set up this connection between the existence of a god and the physical laws: if physical laws are such that to start off life involves an excessively small chance so that it will not be reasonable to suppose that life would have started just by blind chance, then there must be a god, and such a god would probably be showing his influence in the quantum jumps which are taking place later on. On the other hand, if life can start very easily and does not need any divine influence, then I will say that there is no god.
Dirac did not commit himself to any definite view, but he described the possibilities for scientifically answering the question of God.
Dirac biographer Graham Farmelo came to the same conclusion as Sachs did with Cavendish. “Nearly all” of the Dirac stories that physicists have been telling each other for years, he wrote in The Strangest Man, “might also be called ‘autism stories.'” After interviewing 30 people who knew Dirac very well (including two members of his close family) he concluded that his behaviour was so singular that he very clearly passed every criterion for autistic behaviour.
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It’s hard to imagine the state of the modern world if these two remarkable scientists had never lived. Many aspects of life that we currently take for granted might never have been invented. Both men have wondered at times if they had accidentally been born on the same planet, among chatty, well-intentioned creatures who wasted precious time trying to impress, flatter, outwit, and seduce each other. But their atypical minds were uncannily suited to the work they were born to do. They lived their lives in ways that were as precise, ritualized, and methodical as their experiments.
