7

Mephistopheles

God’s whip

PAULI never failed to give full rein to his sardonic humor and caustic wit. He ruthlessly criticized people who he thought did not think clearly. In 1926 he was at a lecture given by the Dutch physicist Paul Ehrenfest. Ehrenfest, a senior figure whose circle included Einstein and Bohr, was famous for his profound understanding of physics and his excellence at explaining difficult concepts. A charismatic teacher, he had motivated a succession of brilliant young students, but he seemed never to make great discoveries to match those of his famous colleagues, and the comparison tortured him. To him Pauli was one of those young “smart alecks…. Always so clever they were! And nobody understood anything.”

After his lecture Pauli offered a string of critical comments. Finally Ehrenfest retorted, “I like your publications better than I like you.” “Strange. My feeling about you is just the opposite,” Pauli countered. The two later became good friends and Ehrenfest came to admire Pauli’s critical acumen. “There is in rebus physicus only ONE God’s whip (Thank God!!!),” Ehrenfest wrote to Pauli a couple of years later. Pauli was delighted with the title Ehrenfest had bestowed on him and there after often signed himself “God’s whip.”

Other acid quips have since become part of Pauli’s lore. When students or colleagues tried out a new theory on him, he would sometimes shout, “Why, that’s not even wrong,” meaning that it was so far from correct it wasn’t even possible to judge it by the normal standards of right and wrong. Other favorite one-liners of his included, “You’re no more interesting drunk than sober,” and “So young and already so unknown.” Colleagues remember that Pauli liked to dream up a cutting remark, keep it in mind, and then, at the appropriate time, use it.

Pauli even criticized Bohr, who sometimes took offense. To Einstein, “I will not provoke you to contradict me, in order not to delay the natural death of [your present] theory,” he wrote, about one of Einstein’s attempts at a unified theory of gravitation and electromagnetism. Einstein, conversely, was quick to compliment the younger man on pointing out an error in another attempt at a unified theory. “So you were right, you rascal.”

The one person Pauli never criticized was his mentor Sommerfeld. Pauli once wrote of the “awe you instilled in me…not even accorded Bohr.” In his presence Pauli was a completely different person. Whenever Sommerfeld visited the Swiss Polytechnic Institute, later referred to as the ETH, in Zürich, where Pauli was working, Weisskopf recalled Pauli would always be saying, “Yes, Herr Geheimrat [Honored Teacher], yes, this is most interesting, but perhaps you would prefer a slightly different formulation, may I formulate it this way.”

At base, Pauli’s razor-edged criticism arose from his dislike of shoddy thinking. As a child he had been raised in a house in which everything from science to politics was pulled apart and criticized. “Obedience to authority was not sung to me in the cradle,” he once wrote. But he simply said what was on his mind. He did not mean his criticisms to be taken personally and he was hardest of all on himself. In a letter to Pauli asking his advice, Heisenberg referred to him as the “master of criticism,” and later recalled that “I have never published a work without having Pauli read it first.” He was often called the “conscience of physics.”

Fresh start

In professional terms, 1927 was a year of immense achievement for Pauli. He had been instrumental in helping Bohr and Heisenberg straighten out quantum theory and was engaged in working with Heisenberg in developing the field that Paul Dirac had initiated, quantum electrodynamics. Then came a shock.

Pauli’s father had always been a womanizer. It was a situation that his mother, the brilliant intellectual journalist, Bertha, had had no choice but to resign herself to. Late that autumn, Wolfgang Sr. finally left her. He had fallen in love with a woman Pauli’s age, a sculptor named Maria Rottler whom Pauli referred to caustically as his “wicked stepmother.” No doubt the younger woman with her artistic ambitions offered Pauli’s father a new lease on life, but to Pauli the desertion of his mother was an unforgivable act of treachery and betrayal.

It was more than Pauli’s poor mother could bear. Not long after her husband left, on November 15, 1927, she took poison and died. Clearly for Pauli it was an unbearable trauma. He closed up and said not a word about it to his friends or colleagues. The extent to which it affected his mental well-being only became clear much later, when he began analysis with Jung.

The same month that Pauli received news of his mother’s death, he also received another, more welcome, communication: the offer of a position at the prestigious ETH. The new job would mean leaving Hamburg for Zürich.

It happened that both the ETH and the University of Zürich were about to lose their most formidable theoretical physicists. Peter Debye, at the ETH, had accepted a position at the University of Leipzig while Schrödinger, at the university, had agreed to succeed Max Planck at the University of Berlin. Debye had been a student of Sommerfeld’s. His main interest was investigating the structure of molecules by studying how they behaved when struck by x-rays, work that was later to earn him a Nobel Prize. The ETH decided to offer the vacant post to one of the two rising stars of theoretical physics—Pauli and Heisenberg. First Heisenberg was offered a position at the ETH, one of several offers he had that year. In the end, however, Debye lured him to Leipzig where he became a professor.

Next the ETH turned to Pauli. The eccentricities of his teaching style were well known. Valentine Telegdi remembered them as “pedagogically maladroit, but full of gems of wisdom which one had to find (and polish) oneself.” Only the most brilliant students could understand anything—though for them it was a lesson not only in physics, but also in how to think critically about the subject. As Markus Fierz, later Pauli’s assistant and then close friend, described it:

His presentation was more like a soliloquy than a lecture. He spoke with an unclear twangy voice, and he wrote with small untidy letters on the blackboard. Sometimes he would lose the thread or, doubting the correctness of a derivation or a statement, shake his head or gaze noddingly into the air. He then continued, mumbling unintelligible words or saying “yes, yes, yes,” though nobody knew what had disturbed him in the first place. This seemed to me extremely mysterious, and it contributed to intensifying the demonic aura surrounding this queer man.

The president of the ETH went personally to Hamburg to assess Pauli’s performance. He decided that Pauli was young enough to improve and immediately offered him a position, starting on April 1, 1928, with a contract for ten years.

Zürich

“In April 1928 I arrived in Zürich as a new professor, dressed like a tourist with a rucksack on my back.” Pauli went straight to his office in the imposing physics building at number 35 Gloriastrasse, a broad street off the main avenue, Rämistrasse, on which sits the principal building of the ETH. There he met his new colleague Paul Scherrer, who had had the office spruced up for the new professor’s first day.

At twenty-eight, Scherrer, a debonair experimental physicist, was Pauli’s exact contemporary. He had carried out important research on the x-ray analysis of crystals with Debye before joining the ETH in 1920 and, by 1927, had been promoted to head of the physics department. Besides his brilliance in research Scherrer was a charismatic lecturer. Twice a week he gave lectures to explain difficult concepts in physics to both scientists and laypeople, backed up by an array of spectacular demonstrations. The auditorium was always packed for what became known as the “Scherrer circus.” On one occasion Scherrer tried out one of his simplified explanations on Pauli, who replied in his caustic way, “Ja, simple it is all right, but also wrong.”

Pauli rented a flat on Schmelzbergstrasse, 34, a steep, narrow, tree-lined road, in a pleasant three-story house set back amidst trees, a few minutes walk from the physics department.

He immediately hired Kronig, who had been the first to realize that Pauli’s fourth quantum number was the spin of the electron, as his assistant. “Every time I say something, contradict me with detailed arguments,” Pauli told him. Next Pauli convinced his closest friend, the physicist Gregor Wentzel, to take the position vacated by Schrödinger at the University of Zürich. Like Pauli, Wentzel had been a student of Sommerfeld’s in Munich. When Pauli was a student Wentzel had been Sommerfeld’s assistant and joined in their café conversations. Two years Pauli’s senior, he had already made important contributions to the new atomic physics. He had an easy-going manner, enhanced by his ever-present cigar and readiness for a good time. In letters Pauli addressed him as “Dear Gregor” and signed himself “Wolfgang”—in those days an extraordinary degree of informality.

Pauli had barely settled into the ETH when he was back at work with Heisenberg. But as the two resumed their research on quantum electrodynamics, they encountered such difficulties that Pauli began to lose heart. He lapsed into the state of mind he had had when previous problems proved intransigent—like in 1924, when his frustration over the anomalous Zeeman effect drove him to seek solace in the bars and whorehouses of the Sankt Pauli district, and again in 1925, when the Bohr theory of the atom collapsed and he daydreamed about giving it all up and becoming a film comedian. This time he played with the idea of dropping out to write a utopian novel. In reality he just needed a rest from physics.

He wrote to Bohr that he was having trouble concentrating. He wished he could say that he had no time for research or that he was tired, he added, but neither was true. “I am only stupid and lazy. I think that somebody ought to give me a daily thrashing! But since unfortunately there is no one around to do it, I must seek other means to reinvigorate my interest in physics.” On the weekends he often went to Leipzig, where regional meetings of the German Physical Society were held. Heisenberg, too, was there and he and Pauli had endless discussions about issues holding up their progress in quantum electrodynamics.

One problem was that Pauli was distracted by the entertainment Zürich offered. He also had just the right mix of colleagues to share it with—Kronig and Scherrer. On warm Sundays the three friends swam at the Strandbad, a beach on Lake Zürich, a ten-minute drive from the city. To cap off the afternoon they would then go back to the city and walk along the elegant Bahnhofstrasse to Paradeplatz where they went to Sprüngli’s café for ice cream and coffee. The rotund Pauli assigned Kronig the task of monitoring his ice cream intake.

In the evenings, after work, they walked down Rämistrasse to Bellevue Square, at the intersection of the Limmatquai, which runs alongside the river Limmat, and the Utoquai, to their favorite restaurants. The most elegant was the Kronenhalle, usually reserved for after-concert dinners. The dining room still retains its old-world flavor with its high ceiling, tables covered with white tablecloths, and waiters gliding around in black trousers, white shirts, black ties, and long white aprons tied at the back. Across the street and around the corner on Limmatquai is the Café Odéon. A masterpiece of art deco design, it was the meeting place for artists, poets, and intellectuals of every persuasion, even the occasional anarchist such as Lenin, who brooded and plotted there until the Allies returned him to Russia in a sealed train in 1917, as if he were a plague bacillus.

Across the Limmatquai is the Café Terrasse where the physics department took its colloquium speakers for dinner. It had a more intellectual atmosphere than the Kronenhalle and the discussion often continued there. In those days the now-enclosed dining room was an outdoor garden. Another spot Pauli and his friends frequented with some regularity was the Bauschänzl beer garden, just across the river Limmat from the Café Terrasse, today a rather garish and pricey restaurant. Other bars and cafés where they spent time, such as the Café Voltaire, the headquarters for dadaism, are gone.

One warm summer’s night after a day of swimming in the lake, ice cream at Sprüngli’s, and dinner at Café Terrasse, the three friends sat in the Café Odéon, penning a postcard to Pauli’s friend and successor in Hamburg, Pascual Jordan, who had worked with Heisenberg to crack the puzzle of the anomalous Zeeman effect. In the three years between his appointment as Born’s assistant at Göttingen in 1924 and his arrival at Hamburg, Jordan had carried out ground-breaking work on the new quantum mechanics. Pauli addressed his postcard to “PQ–QP Jordan,” a joking reference to an important equation Jordan had helped establish. “We are about to study the Zürich night life and try to improve it following the new method due to Pauli: by comparison,” the three wrote exuberantly. “Many Greetings, Kronig,” wrote Kronig. “This method, however, may also be used to worsen matters!—Greetings, Pauli,” added Pauli. “I, too, have heard so many bad things about you that I would like to meet you. Scherrer.”

Shortly afterward Kronig left for a position at Utrecht in the Netherlands and was replaced by Felix Bloch who had been Heisenberg’s first PhD student. Tall, handsome, and urbane, Bloch fit in well with the crowd. Other soon-to-be-famous young physicists passed through the ETH, among them Rudolf Peierls, a student of Sommerfeld’s and Heisenberg’s, who succeeded Bloch as Pauli’s assistant. A young man with immaculately parted hair and round-rimmed glasses, he had to suffer the sting of Pauli’s famous biting remarks. One was particularly memorable: “[Peierls] talks so fast that by the time you understand what he is saying, he is already asserting the opposite.”

J. Robert Oppenheimer worked with Pauli during the first half of 1929. Pauli wrote of Oppenheimer that he treated “physics as an avocation and psychoanalysis as a vocation.” Perhaps Pauli sensed in Oppenheimer’s complex and tortured personality a reflection of himself.

Motivated by his new colleagues, brilliant assistants, and a coterie of exceptional postdoctoral students, Pauli re-entered the stalled collaboration with Heisenberg. By September 1929 they had completed their opus, which they published in two parts. Its eighty-four pages firmly established quantum electrodynamics as a field of research and combined Heisenberg’s intuitive approach and Pauli’s penchant for rigorous calculations to dazzling effect. Covered with lengthy equations, the papers contained a wealth of new mathematical techniques that have since become part of every physicist’s repertoire for exploring how elementary particles interact. “Not for the curious,” quipped Pauli.

As well as its scientific importance, Zürich was a center of German culture and Pauli became a habitué of its intellectual salons. There he met, among others, the philosopher Bernard von Brentano; the writers James Joyce and Thomas Mann; Waldimir Rosenbaum, a wealthy political activist and lawyer; and the artists Max Ernst and Hermann Haller, the son of Einstein’s stern but beloved former boss at the Swiss Federal Patent Office, Kurt Haller. Haller made a bust of Pauli that stands in the La Salle Pauli at CERN. He looks as if he is in deep contemplation, pondering weighty problems. “The sculptor Haller in Zürich has made a bust which makes me look rather introspective—i.e., Buddha-like,” Pauli wrote to Kronig rather proudly.

Pauli in love

Amid this whirl of nightlife and salons Pauli was also building up the prestige of his department and conducting intense physics research. But no matter how much he filled his days and nights, he still anguished over his mother’s death. It was only in 1929 that he hinted at his feelings, signing the papers on quantum electrodynamics that he had written with Heisenberg simply “Wolfgang Pauli,” omitting the suffix “Jr.” He no longer cared whether he was confused with his famous father whom he now loathed.

Then in May 1929 he made a rather strange decision that may or may not have had something to do with his mother’s death: he left the Catholic church and unofficially adopted his father’s original religion, Judaism. Perhaps it was his response to the harsh judgment of Catholicism, which condemns suicide as a mortal sin, that led him to take this step. He later described himself as a “Jew from the waist up.” This may seem odd, in light of his ill feelings toward his father. But he had little regard for either Catholicism or Protestantism, to which his parents had converted in 1911, and he was well aware of how Jewish he looked, with his swarthy complexion, dark wavy hair, and dark eyes.

For all its pleasures Zürich had no Sankt Pauli red-light district where Pauli could seek consolation for his sorrows. He took to making frequent trips back to Hamburg and Berlin. Then, in December 1929, he suddenly announced, to the amazement of his colleagues, that he was going to marry—and, not only that, but that his intended was a cabaret dancer. He had always dismissed marriage as a bourgeois institution.

Perhaps the Zürich academics were surprised that no one else’s wife was involved. In those circles extramarital affairs were common and most marriages quite open. Schrödinger, for example, had had a legendary number of liaisons. He usually traveled with both his wife and current girlfriend. Schrödinger’s wife, meanwhile, was infatuated with the elegant mathematician Hermann Weyl, whose own wife was having an affair with Scherrer.

Pauli had fallen in love. He had met Käthe Deppner some years earlier, during one of his jaunts into the demi-monde of Berlin. Born in Leipzig, she was six years his junior and had trained at the famous Max Reinhardt School for Film and Theater in Berlin. Reinhardt had brought high-class theatre to Berlin and established a film industry that served as a model for Hollywood. Pauli’s sister, Hertha, was with the Max Reinhardt theater and he later revealed that it was when he went to visit her that he had met Käthe for the first time. The two women were friends.

At first Pauli bowled Käthe over by boasting what an eminent physicist he was. Shortly afterward he ran into her again at a party in Zürich given by his friend Adolf Guggenbühl, a wealthy publisher and one of the founders of the magazine Schweizer Spiegel. Käthe was performing with a dance school founded by Trudi Schoop, an old girlfriend of Scherrer’s. Zürich was a small world.

Why anyone falls in love is difficult to work out, especially when no hints are left behind, as was the case with Pauli and Käthe. Käthe was an attractive woman, with a round face and curly hair and a keen sense of fashion. No doubt as a chorus girl she had all the allure of the demi-monde and knew how to attract men. In a photograph of the two on a walk in the mountains, Pauli looks ecstatically happy. Perhaps he sensed a mutual longing and on impulse proposed marriage. It is harder to fathom why she accepted.

Käthe Deppner and Pauli in the countryside, 1929.

For even before the marriage had taken place, it was clear it was going to be a disaster. Käthe made it known that she had already fallen in love with someone else, but for some reason she decided to go through with the marriage to Pauli. Maybe she hoped it would work out in the end. After the ceremony the couple moved into a flat in Hadlaubstrasse, 41, a three-story house with large French windows on a pleasant tree-lined street.

Letters of congratulation poured in. But only two months later, Pauli was already confessing to a friend that he was married only in a very “loose way.” He was clearly unhappy. “He used to walk around like a caged lion in our apartment,” Käthe recalled, “formulating his answers [to letters] in the most biting and witty manner possible. This gave him great satisfaction.” Pauli’s profession demanded that he sit at a desk alone for hours on end. It must have been stifling for someone like her.

In November 1930, less than a year after they had married, the two divorced. Käthe had walked out on Pauli. What he most resented, he always said wryly, was that she had left him for a mere chemist. “If it had been a bullfighter—with someone like that I could not have competed—but with an average chemist?” he would complain. “In spite of his theories he is, like other mortals, at times vehemently plagued by jealousy,” a colleague observed. Soon afterward Käthe married her chemist, Paul Goldfinger.

The lonely neutrino—Pauli’s second breakthrough

Through all this tumult, Pauli’s scientific creativity never flagged. The problem absorbing him at the time was, What happens when the nuclei of certain atoms give off excess energy by emitting an electron? Precise measurements of this process—known as beta-decay—showed, inexplicably, that the energy contained in the nucleus before the electron was emitted was greater than the combined energies of the nucleus afterward plus the discharged electron.

Somewhere, somehow, some energy had been lost. Could it be that beta-decay violated the law of conservation of energy, which holds that these energies must be equal? The law of conservation of energy was a mainstay of physics and engineering, and theories that violated it invariably turned out to be wrong.

Yet, in 1929, Niels Bohr had gone so far as to suggest that this fundamental law might not hold precisely for processes inside the nucleus, but only on average. “We must still be prepared for new surprises” in the atomic world, he wrote. Pauli and most other physicists strongly disagreed.

Pauli jokingly suggested to Bohr, “What if someone owed you a great deal of money and offered to pay it back in instalments, but each time the agreed instalment was not met? Would you consider this to be a statistical error or that something was missing?” In other words, Bohr was trying to make out that the missing energy was a matter of statistics and so was only missing on average.

In the papers on quantum electrodynamics that Pauli wrote with Heisenberg in 1929, he had demonstrated that the law of conservation of energy was built into its equations. Now he pondered long and hard over the loss of energy in beta-decay. Then he came up with an audacious suggestion. Perhaps something really was missing. Could it be that the nucleus undergoing beta-decay emitted another as-yet-undetected particle, along with the electron, that would balance the books?

From the mathematics of beta-decay Pauli inferred that this particle’s mass must be not more than the electron’s, its spin must be one-half and it must have no electric charge. He was later to write of it as “That foolish child of the crisis of my life (1930–1)—which further behaved foolishly.”

He announced his hypothesis in a letter to the audience at the radioactivity session of a physics meeting in Tübingen, Germany, in December 1930, a mere month after his divorce. Even as he pursued his scientific research he could not ignore the fact that his personal life was crumbling around him. The letter—beginning “Dear Radioactive Ladies and Gentlemen”—was to be read in his absence. Pauli had opted instead to attend Zürich’s major social event of the winter, a ball at the splendid Baur au Lac.

In 1930 it was unheard of to suggest a new particle. No one had ever before dared do so. Were the electron, proton (the nucleus of the hydrogen atom), and light quantum (a particle of light) not enough? At first the scientific community was shocked. But it did not take long before everyone acknowledged that Pauli was almost certainly right.

A few years later the Italian physicist Enrico Fermi dubbed Pauli’s new particle the neutrino. The neutrino was the centerpiece of Fermi’s 1934 theory of beta-decay. One of the implications was how weakly neutrinos interacted with matter. The neutrino was a loner, it passed through the earth as if it were not even there and could whiz through space alone, not interacting with anything for three trillion miles. Yet neutrinos also constituted an essential part of the universe, required by basic laws of nature.

Soon after Pauli’s hypothesis of the neutrino, experimental evidence on beta-decay suggested that if the neutrino existed, its mass would have to be zero. We now know it has a tiny mass—about one hundred thousand times less than that of the electron.

Finally, in 1956, twenty-six years after Pauli had suggested it, neutrinos were detected in the laboratory. The neutrino has turned out to be essential for understanding the structure of matter on the subatomic level as well as how massive stars end their lives as supernovas.

In the same period that he had to suffer the death of his mother and his own disastrous marriage and divorce, Pauli had managed to come up with a concept of enormous importance in one of those hunches that influence the whole of physics and our perception of the world. Perhaps it was his need to rescue the beauty of quantum mechanics that impelled him to take this imaginative leap. No matter what dramas occurred in his personal life, his mind was always focused on physics.

Pauli in the United States

Nevertheless, Pauli could not suppress his pain forever. He spent the following summer—1931—traveling across the United States, to Pasadena, Chicago, Ann Arbor, and New York, lecturing on his new particle. Oppenheimer and Sommerfeld were among his traveling companions. Prohibition was in force at the time, forbidding the sale of alcohol, which Pauli found exceedingly trying. Ann Arbor, however, was close to the Canadian border and there was plenty of opportunity for smuggling. He wrote to Peierls, “In spite of the opportunity for swimming here I suffer much from the great heat. But under ‘dryness’ I don’t suffer at all.”

Indeed he did not. By now he was drinking to excess. At a dinner party in Ann Arbor he fell down an entire flight of stairs. “I broke my shoulder and now must lie in bed until my bones are whole again—very tedious,” he wrote. As his shoulder was broken he could not write on the blackboard. Instead of his usual impenetrable lecture style, he was forced to face his audience, his injured arm supported by a metal rod attached to a ring around his expansive waist, while a colleague wrote up the equations. His audiences were enthralled by the brilliance and clarity of his explanations. He kept the real reason for his handicap a secret. The story that went around was that he had injured his shoulder while swimming. One participant at the physics sessions in Ann Arbor commented that he “now runs around with it stuck up in the air like a traffic cop signalling.” Sommerfeld called it an inverse Pauli effect. Later Pauli commented jokingly that it was the only time in his life he had ever raised his hand in a “Heil Hitler” salute.

Instead of returning to Zürich immediately, Pauli spent part of September in a small hotel in Manhattan. Much of the time he kept to himself, except for the occasional meeting with “second-order acquaintances”—friends of friends. (A second-order approximation to solving a problem is less exact than one of first order.) He frequented second-order bars—small speakeasies and out-of-the-way bars rather than the elegant ones that Scherrer had recommended.

Pauli enjoyed America, its people and food—excellent but for the Athenaeum Club at the California Institute of Technology, where he pronounced the food schlecht (wretched). He was less enthralled by its puritanical side; at one dinner there “was a prayer instead of coffee and cigars—not to speak at all of alcohol.” But on the whole he liked it “better than Europe which seems to me now often tiny and clumsy…. It is all very simple and very neat here,” he wrote to Wentzel.

That evening, he continued, he was looking forward to going to “a very good bar and drinking many whiskies.” For, despite his efforts to conceal it, he was falling deeper and deeper into depression. “With women and me things don’t work out at all, and probably never will succeed again,” he confessed to Wentzel. “This, I am afraid, I have to live with, but it is not always easy. I am somewhat afraid that in getting older I will feel increasingly lonely. The eternal soliloquy is so tiresome.” Alone in his hotel room he signed his letter, “Your old Pauli.”

Back in Zürich, he went on a binge of drinking and parties and resumed his life of barroom brawls, smoking, and womanizing. Eventually his bitter quarrels with his colleagues at the ETH came to the attention of the administration, who had to call him in and warn him that his position might be in jeopardy despite his brilliant work.

In front of his colleagues he spoke of his divorce from Käthe in witty, sardonic terms, but his behavior reflected his true desperation. Once again he was living a Jekyll and Hyde existence between two different worlds. To add to all this, his always vivid and dramatic dreams were beginning to seep into his waking life. By the beginning of 1932 he had plummeted to a frightening low point. Despite his hatred of his father, Pauli finally decided to heed his advice: to consult the celebrated psychoanalyst Carl Jung.

The Mephistopheles of Copenhagen

That year, Pauli’s neutrino hypothesis was the central topic at the annual Easter conference held at Bohr’s institute in Copenhagen. It was also the theme of the spoof that customarily concluded the conference, written that year by Max Delbrück, a twenty-five-year-old physicist who had studied with Born.

He and Pauli were close friends; Pauli addressed him in letters as “Max” and signed them “Wolfgang.” Pauli characterized their friendship as a mutual attraction between “two problematic temperaments.”

Years later, Pauli reminded Delbrück that “for me personally the history of the neutrino is inseparably connected with your—very unsuccessful—flirtation with Eve Curie at the party [at the Nuclear Physics Meeting in Rome, in 1931]. She had a sincere veneration of her old mother, whom she had accompanied to the Rome meeting, but otherwise this icy woman had nothing on her mind other than publicity, newspapers with her name in, etc. Why should she have any interest in you, if there was no chance for her to increase her publicity with your help?”

Delbrück entitled his spoof “Faust in Copenhagen,” and modeled it on Goethe’s Faust, with the luminaries of physics as its characters: God stood for Bohr, and Faust for Ehrenfest (who had said to Pauli, “I like your publications better than I like you”). Mephistopheles stood for the sharp-tongued Pauli, who was also the progenitor of the neutrino (Gretchen). In the spoof, Felix Bloch played God (Bohr) and Léon Rosenfeld, Bohr’s assistant at the time, played Mephistopheles (Pauli).

Mephistopheles/Pauli the troublemaker tries to tempt Faust/Ehrenfest by offering him the seductive neutrino—a hypothesis of which the conservative Ehrenfest was famously deeply skeptical. Faust declares that no elementary particle could possibly exist with neither mass nor charge; it is pure madness.

The spoof was wonderfully translated by the physicist, prankster, and frequent visitor to the institute, George Gamow, who had provided delightful cartoons of the characters, including a wickedly accurate depiction of the plump Pauli as Mephistopheles with an infuriating grin and a long tail.

The play opens with Mephistopheles leaping into the midst of a group of archangels, headed by God, all busy discussing astrophysical matters and how stars shine. “To me the theory’s full of sound and fury,” he declares. The Lord/Bohr demands,

Pauli as Mephistopheles in George Gamow’s caricature.

But must you interrupt these revels

Just to complain, you Prince of Devils?

Does Modern Physics never strike you right?

Mephistopheles replies,

No, Lord! I pity Physics only for its plight,

And in my doleful days it pains and sorely grieves me.

No wonder I complain—but who believes me?

Delbrück perfectly captured the rivalry between Bohr and Pauli, who kept each other at arm’s length. Pauli had initially proposed the neutrino specifically to counter Bohr’s suggestion that the laws of conservation of energy and momentum held only on average in the case of beta-decay.

The Lord dismisses the neutrino hypothesis in Bohr’s much-feared words, saying that it “is very in-ter-est-ing”—incorrect, in other words. Mephistopheles fires back, “What rot you talk today! Be quiet!”

Ehrenfest doubted more than Pauli’s neutrino. He also questioned the work on quantum electrodynamics in which Pauli and Heisenberg had been immersed for five years, plagued by the infinite values for the electron’s mass and charge, which they could not eliminate no matter how hard they tried. Gamow portrayed the oblong-headed Heisenberg and devilish Pauli as Siamese twins.

Mephistopheles, transformed into a bowler-hatted traveling salesman, tries to sell Faust quantum electrodynamics, the theory formulated “By Heisenberg-Pauli.” “No sale!” Faust shouts. Then Mephistopheles offers Faust “something unique”—his neutrino theory. Says Faust,

You’ll not seduce me, softly though you speak.

If ever to a theory I should say:

“You are so beautiful!” and “Stay! Oh, stay!”

Then you may chain me up and say goodbye—

Then I’ll be glad to crawl away and die.

Ehrenfest famously believed that beauty was for tailors, not scientists.

Finally Gretchen herself, the neutrino, enters singing:

My mass is zero,

My Charge is the same.

You are my hero,

Neutrino’s my name….

I am your fate,

And I’m your key.

Closed is the gate

For lack of me.

But Ehrenfest remains unconvinced.

Pauli was not present to see himself lampooned, but he later received a copy of the text complete with Gamow’s drawings of him as the mischievous troublemaker of physics. He proudly showed it to visitors. He was obviously delighted to be cast in this role.

In fact he was in Zürich, and his life was about to change.