Part 2 (1/2)

In the evenings, instead of turning left on Theresienstra.s.se to go to the university, Pauli would turn right. The road took him to the bohemian Schwabing district teeming with cafes, bars, beer gardens, and a huge number of cheap apartments. It was like a fusion of the Latin Quarter in Paris, where debates over the latest trends in art, music, and politics took place, with Montmartre, populated by the creators of these movements who generally lived in squalid conditions. Like the avant-garde scene in Paris there were publis.h.i.+ng houses turning out new-wave literary magazines and satiric journals. It was the locus of radical experiments in art, politics, and s.e.x. In Schwabing, anything went.

The area a.s.similated a spectrum of people. Before the war Vladimir Ilyich Lenin lived there while on the run from the tsar's secret police and schemed with a.s.sociates such as Rosa Luxemburg. Among other denizens were the writers Thomas Mann and Rainer Maria Rilke and the artists Wa.s.sily Kandinsky and Paul Klee. It was a place where up-and-coming artists aspired to achieve their first success. Among these was a young man who arrived in 1913 and made a living by selling his paintings of the area to tourists. He tried to fit into the bohemian culture, but never really did. Twenty years later Adolf Hitler, in his autobiography Mein Kampf (My Battle), recalled the ”Schwabing decadents.”

Despite the upheavals in Munich, in October 1918 Schwabing was an island of calm. Cafe society was still bustling. Young Pauli, newly released from home, found it irresistibly attractive. He came to drink, to meet men and women, and perhaps to think about physics, while sitting at a table with a gla.s.s of wine or a cup of coffee. He had found the rhythm of his life.

Pauli spent longer and longer in Schwabing, though he was always careful to stay sober enough to be able to spend the small hours of the night working. It soon became impossible for him to make it to Sommerfeld's morning lecture, which began at 9.00 a.m. Instead Pauli took to dropping in at noon to check the blackboard to see what the topic had been so he could work it out for himself.

Sommerfeld reprimanded him. ”In order for you to become a genius I have to educate you,” he told him. ”You have to come at eight o'clock in the morning.” Unusually in the stiff world of the German Herr Professor Doktor, he was prepared to tolerate erratic behavior if the student was undoubtedly brilliant. Touched that Sommerfeld took such personal interest in his well-being, Pauli began to turn up at 8.00 a.m., at least for a while.

Pauli was particularly gripped by Sommerfeld's course on cutting-edge atomic physics, which focused on problems that the master himself was still struggling with. Fortunately for Pauli, the seminar took place once a week for two hours-in the evening.

After cla.s.s a group of students often went to the cafe Annast, now part of the Hofgarten-Cafe, in the southernmost part of Ludwigstra.s.se, a short walk from the university's main entrance. For scientists the attraction of the Annast was its marble-topped tables, which provided excellent surfaces for scribbling equations during animated conversations. According to one story, Sommerfeld was once stuck on a particular equation. When he left the cafe he forgot to erase his attempts to solve it. The next evening he returned and found that another customer had solved it for him.

War zone in Munich.

A short three months after Pauli arrived in Munich, this idyllic world of pondering the universe came to an abrupt end. Suddenly Munich was in the grip of anarchy. The moderate Soviet Republic formed just a few months earlier had lost the support of the populace. It was not surprising. Every day Pauli would have seen people standing hungry in the streets, lining up for food in the snows of one of the worst winters on record. A host of political factions sprang up and with great speed coalesced into two groups: a moderate to extreme right-wing group and a left-wing communist one. Both sides had no trouble recruiting an army. Central Europe was swarming with thousands of armed, disgruntled, and starving soldiers looking for a fight. The situation was ominous. News traveled fast around Munich that there had been a gun fight in the Bavarian diet, and that two representatives had been killed.

For sizable periods of time the university was shut down. Cafes became cla.s.srooms for Pauli and his fellow students and teachers. They also offered front-row seats for the street fighting carried on by uniformed soldiers as well as local citizens. Sometimes it was difficult to tell one side from another. By April there was a second Soviet Republic.

But this second Soviet regime also failed to contend with the food and fuel crisis and in April 1919 total chaos descended on Munich. Having suppressed an attempted communist coup in Berlin, the federal government dispatched an army to Munich to put down the last vestiges of rebellion against it. They blockaded the city, exacerbating the already critical food and fuel shortages. The struggle boiled down to a confrontation between the Communist army of the Soviet Republic-the reds-and the army from Berlin-the whites. The Red Army had 15,000 soldiers. The whites had about 40,000 soldiers, committed to eradicate by any means the Communists who they saw as a threat to the new republic.

Even walking the streets was risky because the reds were arresting and summarily shooting anyone suspected of spreading discontent or who looked suspicious.

The backbone of the white army-the Berliners-was the Freikorps (Free Corps). This was made up of extreme right-wing fascist paramilitary units manned by combat-hardened ex-soldiers serving as mercenaries, former officers often with royal t.i.tles and students who had been too young to fight in the war and sought instant action against easy targets. They were financed privately by German industry and hated Communists. One unit of the Free Corps called itself the defender of the democratic spirit against Communists and Jews. From it emerged such staunch ”defenders of democracy” as Rudolf Hess, who was to become Hitler's deputy chancellor, and Ernst Rohm soon to command Hitler's storm troopers. It was also to provide the start in life for the man who was to become Pauli's closest colleague-Werner Heisenberg.

Preceded by a heavy artillery and mortar bombardment that created enormous damage and caused numerous civilian deaths, at the end of April the white army stormed Munich. Planes flew over, dropping leaflets telling people to surrender. There was heavy street fighting and ma.s.sacres by both sides.

The fighting ended on May 8. Thousands of Red Army soldiers and civilian supporters had been killed-some estimates were as high as 20,000-in what became known as the white terror, wreaked mainly on the reds by the trigger-happy Free Corps. The white army estimated its losses at around 60. But the white terror was not yet over. People suspected of collaboration were summarily shot, stabbed, or beaten to death with rifle b.u.t.ts. Often they had been identified by spies who had infiltrated communist organizations, such as Corporal Hitler who had returned to decadent Schwabing. Munich, his favorite city, soon became the hot bed of his right-wing politics. The excesses of the Free Corps were so blatant that Lenin threatened to unleash Soviet forces on the area.

For Pauli, as for everyone, it must have been a traumatic and exciting time and also certainly dangerous. No doubt he wrote home about his experiences but sadly none of those letters remain. Perhaps Pauli's father destroyed them when he fled Vienna in 1938. Pauli, himself, may have destroyed others when he left Europe in 1940.

Pauli meets Heisenberg.

By 1920 peace had returned to the city. Pauli was now Sommerfeld's deputy a.s.sistant. Among the students whose homework he had to correct was a young man called Werner Heisenberg.

Heisenberg was destined to become one of the great names in the history of physics. Even as a boy he was immensely compet.i.tive. He was not a natural athlete but trained with great determination and became an expert skier, runner, and Ping-Pong player. Like Pauli, he breezed through his cla.s.ses at school and spent much of his time reading on his own, almost exclusively mathematics.

He had the look of ”a simple farmboy with short, fair hair, clear blue eyes, and a charming expression,” his friends recalled. Heisenberg first encountered atomic physics at the age of eighteen, in 1919, reading Plato's Timaeus while lying on a rooftop at the University of Munich during a break from his military duties as a member of the Free Corps, while rioting went on below him. (Five decades later Heisenberg was to recall those days as youthful fun, like ”playing robbery [cops and robbers] and so on; it was nothing serious at all.” Perhaps. Or perhaps not.) Heisenberg was entranced with Plato's description of atoms, visualized as geometrical solids. He knew this was now fantasy but was struck by the way in which the ancient Greek scientists were prepared to consider even the most unlikely speculations.

He had developed a keen interest in the theory of numbers and a year later entered the university. He had also tried studying Einstein's relativity theory. The reigning power in the mathematics department, Professor Ferdinand von Lindemann, convinced that Heisenberg's brush with relativity theory had spoiled his mind for a career in mathematics, rejected him outright. Sommerfeld, on the other hand, delighted with his enthusiasm and obvious brilliance, sent him straight to his graduate-level seminars, plunging him into advanced quantum physics.

Heisenberg and Pauli quickly struck up a friends.h.i.+p, cemented by their mutual pa.s.sion for physics-although the two young men had diametrically opposite tastes when it came to what const.i.tuted a good time. Heisenberg recalled: ”While I loved the daylight and spent as much of my free time as I could mountain-walking, swimming or cooking simple meals on the sh.o.r.e of one of the Bavarian lakes, Wolfgang was a typical night bird. He preferred the town, liked to spend his evenings in some old bar or cafe, and would then work on his physics through much of the night with great concentration and success.” It was often said that in Germany just after the war, in the pre-Hitler years of the Weimar Republic, there were two types of people: those who went in for night life and those who dedicated themselves to the youth movement. Pauli typified the former, Heisenberg the latter.

Whenever they were apart, they corresponded, though their letters were more like scientific articles as they bounced ideas off one another. Just as he had corrected Heisenberg's homework in Munich, so Pauli continued to comment critically on Heisenberg's ideas. ”Pauli had a very strong influence on me,” Heisenberg recalled. ”I mean Pauli was simply a strong personality.... He was extremely critical, I don't know how frequently he told me, 'You are a complete fool,' and so on. That helped me a lot.”

”When I was young I believed I was the best formalist of my time,” Pauli said later in life, referring to his extraordinary understanding of mathematics and how to use it in solving problems in physics. Mathematics had served him well in his papers on relativity theory. Now Pauli was to apply his mathematical ac.u.men to another puzzle that he was determined to crack and which formed the subject matter of his PhD thesis. It related to the great Danish physicist Niels Bohr and his seminal model of the ”atom as universe.”

Niels Bohr and his theory of the atom.

Bohr was another scientific prodigy. He arrived in England from Copenhagen in 1911, when he was twenty-six, and became fascinated by the work of Ernest Rutherford at Manchester University. Rutherford had just unraveled the structure of the atom in a series of experiments that suggested that the atom was made up of a nucleus with a positive charge, surrounded by enough negatively charged electrons to produce an electrically neutral atom.

In other words, it was a sort of miniature solar system. But the model was unstable. Science was out of step with nature.

Bohr set out to solve this problem. He showed that electrons in an atom could not revolve in just any orbit-like planets-but that only certain orbits were allowed. Given that atoms are generally stable, their planetary electrons cannot be pulled into the nucleus. If they did then the atom would collapse. Bohr interpreted the stability of atoms as proof that there had to be a lowest orbit. He found it by altering Newton's theory of planetary motion using Planck's constant.*

In his atomic ”bookkeeping” Bohr a.s.signed to each allowed orbit a whole number, which he called the ”princ.i.p.al quantum number.” The lowest orbit was number one. As the princ.i.p.al quantum number increased, the orbits became closer and closer. Bohr called allowed orbits ”stationary states.”

(a).

(a) This figure shows the hydrogen atom with its single orbital electron from Bohr's theory of the atom, where n is the princ.i.p.al quantum number tagging the electron's permitted orbits. When the electron moves from a higher to a lower orbit there is a burst of radiation, and the frequency of this emitted radiation can be measured as a spectral line. The Lyman series, Balmer series, etc. are series of spectral lines.

(b)

(b) This figure shows the Balmer series.

Since the late nineteenth century scientists had been aware that when light illuminated a collection of atoms, they emitted light in response. When the light the atoms emitted was pa.s.sed through an instrument that separated its frequencies-a spectroscope-lines appeared. Dubbed spectral lines, these lines were unequally s.p.a.ced and bunched up more and more as their frequency increased. Most strikingly the series of lines were different for each sort of atom. In fact, an atom's spectral lines were its fingerprint, its DNA. Scientists had made a stab at writing equations to describe these lines, but there was no theory of the atom to explain the equations. Bohr's was the first to succeed.

According to Bohr's theory atoms emitted light when an electron moved from an upper to a lower orbit. The light that was emitted by an electron had the same frequency as a spectral line that had been observed. An oddity of the theory was that the electron's transition from one orbit to another could not be visualized-it disappeared and appeared again like the Ches.h.i.+re cat's smile. In this sense the electron's quantum jumps were discontinuous.

Bohr's was a magnificent theory and it worked more than adequately. When applied to the hydrogen atom, the difference between the spectral lines observed in the laboratory and the spectral lines deduced from his theory was only 1 percent.

Scientists were impressed not only by its accuracy but also by its iconic visual imagery: the atom as a miniscule solar system with the electrons revolving in circular orbits around a central ”sun,” or nucleus. It was a momentous fusion of large and small, of the universe and the atom, the macro-and microcosmos.

Bohr's theory depicted the simplest element, hydrogen, as a single electron orbiting a positive charge-its nucleus. The atom had no total electrical charge; it was electrically neutral, just as atoms are in nature. Helium, the next element in the periodic table of the chemical elements, differs from hydrogen in that it has two electrons that orbit around a nucleus that has two units of positive electric charge. Because helium does not react chemically-it cannot bond with any other element-Bohr deduced that the innermost orbit needed to be filled up with two electrons. He went on to infer that the next orbit can take on eight electrons.

Atoms depicted according to Bohr's atomic theory. (Kramers and Holst [1923]).

As another of the pioneers of atomic physics, Max Born, head of the Inst.i.tute for Atomic Physics at the University of Gottingen, put it: A remarkable and alluring result of Bohr's atomic theory is the demonstration that the atom is a small planetary system.... The thought that the laws of the macrocosmos in the small reflect the terrestrial world obviously exercises a great magic on mankind's mind; indeed its form is rooted in the superst.i.tion (which is as old as the history of thought) that the destiny of men could be read from the stars. The astrological mysticism has disappeared from science, but what remains is the endeavor toward the knowledge of the unity of the laws of the world.

Pauli's work on Bohr's theory.

No one had attempted to apply the Bohr theory to anything more complex than the hydrogen atom. Pauli set out to do so.

He began the year after he arrived in Munich and decided to apply Bohr's theory to the next simplest atomic system to the hydrogen atom, that is, two protons...o...b..ted by a single electron-the hydrogen-molecule ion, H+2. The mathematics he had to grapple with was extremely complex. The problem gnawed at him. It took over his life. He ended up thinking about it night and day.

The last thing Pauli wanted was to disprove Bohr's iconic model. But after two years of working on the problem he had to conclude that he had proved beyond doubt that Bohr's theory could not produce the necessary orbits-or ”stationary states”-for a stable H+2 ion. When he applied Bohr's theory, he discovered that a small disturbance to the electron orbiting the two protons would make it fly away from them. But that couldn't be right because stable H+2 ions had already been found in the laboratory. This could only mean that there was something fundamentally wrong with Bohr's model-not at all the result Pauli had hoped for.

Pauli was deeply discouraged. But Sommerfeld praised his mathematical skill and thoroughness. Heisenberg considered Pauli's result ominous. ”In some way this was the first moment when really this confidence [in Bohr's theory] was shaken,” he said.

Then Pauli received an invitation from Max Born. Born had done important work in electromagnetic theory, relativity, acoustics, crystallography, and most recently atomic physics. He was highly impressed with Pauli's mathematical skills and invited him to spend six months at the inst.i.tute. Pauli accepted.

”W. Pauli is now my a.s.sistant; he is amazingly intelligent and very able. At the same time he is very human and, for a 21-year-old, normal, gay, and childlike,” Born wrote to Einstein. By Pauli's own account, he was actually rather miserable. Born and Pauli applied Pauli's mathematical methods to the helium atom (He)-two electrons...o...b..ting a nucleus. But Bohr's theory failed here, too. It horrified Pauli that all his work seemed to result only in undermining this iconic theory. As far as he was concerned, it was he who had failed, not the theory. This failure loomed over him and grew into a general sense of gloom.

Despite Born's presumption of his ”gaiety,” he had also noted that Pauli ”cannot bear life in a small city.” Nor was Pauli particularly enamored of working with Born. While Born was neat and well organized, Pauli was not. Born was an early riser, Pauli far from that, especially after late nights working. Born often had to send someone to Pauli's apartment at 10:30 in the morning to awake him for his 11 o'clock lecture. Born recalled: ”Although a place like Gottingen is accustomed to all kinds of strange people, Pauli's neighbors were worried to watch him sitting at his desk, rocking slowly like a praying Buddha, until the small hours of the morning.”

Pauli also did not appreciate Born's overly heavy mathematical style of physics. He felt that the time was not yet ripe for such a rigorous approach. For him adroit guesswork backed up by mathematics was the best way to proceed.