Before the Fallout
Page 9
While recovering from a serious illness, Heisenberg read about Einstein's theories of relativity. The mathematical arguments and the abstract thoughts underlying them both excited and disturbed him. He enrolled at Munich University to study theoretical physics under Professor Arnold Sommerfeld, whose contributions in the fields of quantum theory and relativity and brilliance as a teacher were legendary. Another of Sommerfeld's students was the sharply clever Wolfgang Pauli. Pauli and Heisenberg became close friends, though their habits were diametrically opposed. Heisenberg loved hiking and camping expeditions and became a leader in one of the many youth movements then springing up with the aim of renewing the spiritual and physical vigor of German youth. Pauli was a night owl, happiest in smoky cafes. He worked through the night and would not rise until noon. He teased the fresh-faced Heisenberg for being a "prophet of nature." In 192c Pauli would propose his famous "exclusion principle," suggesting—on the basis of his experimental observations of how electrons behaved when subjected to magnetic fields—that no more than two electrons could inhabit the same orbit around a nucleus. This resolved a hitherto puzzling anomaly and earned him the nickname of the "Atomic Housing Officer."
It was Sommerfeld who brought Heisenberg with him from Munich to hear Niels Bohr at Gottingen. The lecture hall was crammed. Heisenberg was excited not only by what the Dane had to say but also, as he later recalled, by how he said it: "Each one of his carefully formulated sentences revealed a long chain of underlying thoughts, of philosophical reflections, hinted at but never fully expressed." At the end of Bohr's third lecture Heisenberg summoned enough courage to voice a critical remark. Bohr listened gravely and at the end of the lecture invited Heisenberg for a walk over the Hain Mountain. During it, Bohr asked him to visit Copenhagen. Heisenberg later wrote, "My real scientific career began only that afternoon."
Also that year, 1922, Sommerfeld suggested that Heisenberg attend a scientific congress in Leipzig where Einstein was speaking. As Heisenberg entered the lecture hall, a young man pressed a red handbill into his hand. It attacked Einstein and derided relativity as wild, dangerous speculation alien to German culture and put about by the Jewish press. The lecture went ahead, but Heisenberg was too disturbed by the eruption into science of such "twisted political passions" to concentrate. He had no heart, at the end, to seek an introduction to Einstein. It was his first, but by no means last, experience of what he called "the dangerous no-man's land between science and politics."
After completing his doctorate at Munich, Heisenberg moved to Gottingen as Max Born's assistant. He also made frequent visits to Bohr in Copenhagen. During long walks he and the Dane became good friends while debating quantum theory. Heisenberg was becoming increasingly troubled by the theory's reliance on the unobservable and hence the unmeasurable. Hypothesizing about what was happening within the atom and about orbiting electrons was, he felt, all very well, but he yearned for proof of what was actually occurring. He therefore decided to focus on what could be observed—the frequencies and amplitudes of light emitted from inside the atom—and to seek mathematical correlations between them.
It was a complex task, but in 1925 Heisenberg had something akin to a vision. A severe bout of hay fever sent him to the bracingly windy, relatively pollen-free North Sea island of Heligoland. He arrived with a face so swollen his landlady thought he had been in a fight. He worked late in his room, churning out reams of calculations until he felt that "through the surface of atomic phenomena, I was looking at a strangely beautiful interior, and felt almost giddy at the thought that I now had to probe this wealth of mathematical structures nature had so generously spread out before me." He was so exhilarated that, instead of going to bed, he went out and climbed a jutting sliver of rock and waited for the sun to rise.
Down from "the mountain" and back at Gottingen, Heisenberg was sufficiently sure of himself to parade his thoughts to Max Born and his colleagues. Together they evolved what Heisenberg called "a coherent mathematical framework . . . that promised to embrace all the multifarious aspects of atomic physics." This new approach was the earliest version of "quantum mechanics"—a tool using experimental evidence to predict physical phenomena. It was based on matrix algebra, a species of mathematics originally developed in the 1850s, and later refined, as a means of analyzing large amounts of numbers using a system of grids. In keeping with his original aim, Heisenberg's quantum mechanics focused on what could be observed—like radiation emitted from an atom—and otherwise involved only the use of fundamental constants. In contrast with the Rutherford-Bohr model, Heisenberg's abstract mathematics provided nothing in the way of a picture of atomic structure, but its predictions proved remarkably accurate.
Heisenberg s approach had a competitor: "wave mechanics," outlined just a few weeks later by an urbane Austrian physicist, Erwin Schrodinger. Building on an idea of the Frenchman Louis de Broglie that particles such as electrons behave like waves, Schrodinger invented a neat equation capable of embracing those wavelike characteristics. An important feature was the incorporation in the calculation of a likelihood of occurrence—a probability—which meant, for example, that the location of an electron was not predicted as a point but rather as a smear of probability whose density gave the likelihood of the electron being found at any point. At first, Schrodinger's different approach appeared to threaten Heisenberg's quantum mechanics, and the respective proponents indulged in vigorous debate. Heisenberg wrote crossly to Wolfgang Pauli, that, "The more I think about the physical portion of Schrodinger's theory, the more repulsive I find it. . . . What Schrodinger writes about the visualizability of his theory is probably not quite right, in other words it's crap." However, Schrodinger proved that his "wave equation," as it became known, provided resuits mathematically equivalent to Heisenberg's formulas and that the two theories complemented each other rather than conflicted. Schrodinger's waves and Heisenberg's matrices were analogous.
From left to right: Enrico Fermi, Werner Heisenberg, and Wolfgang Pauli
Heisenberg's next step, in 1927, was his renowned "uncertainty principle." It grew out of an intellectual pummeling from Bohr over whether apparent ambiguities in atomic physics could be reconciled. A cold walk under a starlit sky in Copenhagen led Heisenberg to a conclusion that some uncertainties were unavoidable. Given the atom's tiny dimensions, the scientist's ability to measure events must be inherently limited. The more accurately one aspect was measured, the more uncertain another must become. Although it was possible accurately to observe either the speed or the position of a nuclear particle, doing both simultaneously was impossible. "The more precisely the position is determined," he wrote, "the less precisely its momentum is known and vice versa." In the mechanical world of Newtonian physics, future behavior could be predicted with certainty, just as what had happened in the past could be accurately determined. Under Heisenberg's principle, while past behavior could be known accurately and future behavior could generally be predicted using a series of approximations based on probability, the future behavior of an individual atom was subject to inherent uncertainty.
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Heisenberg's ideas at first provoked a fierce reaction from Bohr, who taxed him with flying in the face of previous interpretations and reduced him to tears with his vehemence. When both had cooled off, they agreed that their approaches could, after all, be reconciled. Bohr incorporated Heisenberg's uncertainty principle into a broader thesis of his own: "complementarity." He argued that conflicting or ambiguous findings should be placed side by side to build a comprehensive picture—the particle and wave nature of matter should be accepted—and each aspect should recognize "the impossibility of any sharp separation between the behaviour of atomic objects and the interaction with measuring instruments." He borrowed the word complementarity from the Latin complemen-tum, meaning "that which completes." Bohr's and Heisenberg's friendship emerged unscathed from their confrontation. However, Heisenberg's uncertainty principle sparked a famous row with Einstein, who argued th
at probability was far too vague a tool for assessing the physical world: "It seems hard to sneak a look at God's cards. But that He plays dice and uses telepathic methods . . . is something that I cannot believe for a single moment." Nor did he or any other scientist yet believe that this rash of new intellectual tools would be used to predict how atoms could be split to release their latent energy explosively.
That same year, 1927, Heisenberg was appointed professor at Leipzig at just twenty-six. His youth, lack of formality, and skill at Ping-Pong endeared him to his students, one of whom was the young Hungarian Edward Teller, later to be known as the "father" of the H-bomb. Science was Teller's earliest passion. He had gained his first respect for technology from a ride in his grandparents' car. The end of the First World War and the collapse of the Austro-Hungarian Empire, when Teller was ten, had destroved his comfortable, middle-class world, just as Heisenberg's had disintegrated. Many of Teller's games consisted of playing with numbers, finding security in the patterns they created. In the newly independent Hungary a communist takeover was followed by hunger and uncertainty. Soldiers were billeted on the Tellers in their Budapest home, and Edward had perforce to learn to sing the "Internationale" at school. Many of the communist leaders were Jews, and when the communist regime collapsed it triggered a vicious anti-Semitic backlash against Jewish families like the Tellers. In 1919 the new right-wing "white" Hungarian government under Admiral Horthy conducted a purge. Over five thousand people, many of them Jewish, were executed, and thousands more fled. Anti-Semitism became so open and pervasive that, even as a youngster, Teller worried whether "being a Jew really was synonymous with being an undesirably different kind of person."
During his final years at school, knowing that science was his great love, Teller sought the company of three young scientists, all from Budapest's Jewish community, all of whom were studying in Germany. The theoretical physicist Eugene Wigner, later winner of the Nobel Physics Prize in 1963, and the mathematician John von Neumann, later the designer and builder of some of the first modern computers in the late 1940s, were in their early twenties. The third man, the eccentric Leo Szilard, was a little older. Listening to their discussion, occasionally daring to ask questions, Teller decided to study mathematics but knew that it would be hard to climb the academic ladder in Hungary, where Jews were subject to a quota system. His father urged him to go to Germany, which in the 1920s, according to Teller, appeared to be free of anti-Semitism. He also urged his son to study something more practical than mathematics, and they compromised on chemistry.
In 1926 Teller's protective parents accompanied the seventeen-year-old onto an express train to Karslruhe, where he enrolled in the Technical Institute. However, within two years Teller had abandoned chemistry and was studying physics and mathematics with Arnold Sommerfeld in Munich. He did not achieve the rapport that Heisenberg had enjoved with his brilliant teacher. Teller wrote of Sommerfeld that he was "verv correct, verv svstematic, and very competent. I disliked him." However, he found his new field—particularly the new science of quantum mechanics—deeply exciting.
Lost in thought on his way to meet friends for a hike in the Bavarian Alps in 1928, Teller absentmindedly slipped while dismounting from a trolley bus and was caught by its wheels. Unlike Pierre Curie, he survived, but the bus severed his right foot. What Teller remembered most of his recuperation was the sudden disappearence of a Dr. von Lossow, who had been treating him. He later found out that the doctor was a relative of General von Lossow, who had arrested Hitler after his abortive 1923 Munich beer hall putsch. By 1928 public dissatisfaction with the weak Weimar Republic and the weak economy over which it presided was growing, and conflicts between the extreme right and left were beginning again. As Hitler's Nazis reemerged as a political and street-fighting force, Dr. von Lossow had probably realized that Germany held no future for him.
Teller, however, still caught up in the heady atmosphere of new ideas, did not allow the sinister undercurrents to worry him. Released from the hospital and learning that Sommerfeld had gone abroad for a year, he headed happily for Leipzig and Heisenberg. He was eager to study under the man he revered not only for giving mathematical expression to quantum mechanics but also for giving it philosophical expression through his uncertainty principle.
*In the Second World War Saipan and Tinian, once captured bv the Americans, would become major air bases for the U.S. assault on Japan.
FIVE
DAYS OF ALCHEMY
ATOMIC PHYSICISTS, looking back from a less innocent age, would recall the 19 20s as "a heroic time . . . a time of creation." Such an intoxicating atmosphere exactly suited a charismatic young Russian, Peter Kapitza, who arrived at the Cavendish Laboratory to become Rutherford's star pupil. The son of a czarist general, Kapitza had, in 19 21, left a Russia riven by civil war and famine as a member of a Soviet mission sent to renew scientific relations with other countries. The mission's leader, Abram Joffe, a sympathetic individual as well as one of Russia's foremost physicists, had brought Kapitza to help him overcome a devastating trauma. Kapitza had recently lost his two-year-old son to scarlet fever, followed, within a month, by the loss of his wife, baby daughter, and father to the Spanish flu epidemic sweeping through Europe.
Liking what he saw in Cambridge, Kapitza asked Rutherford to take him on as a research student. Rutherford, fearing that Kapitza might be a left-wing agitator, consulted Chadwick, who advised that the Russian would be an asset, provided he agreed not to talk politics. Kapitza accepted the condition and soon formed an unlikely friendship with the quiet, retiring Chadwick, allowing the Englishman to pilot his motorbike and, by misjudging the curves, to send them both flying. When Chadwick married Aileen Stewart-Brown, the daughter of a prominent Liverpool stockbroker, in 192c, Kapitza was his best man in a borrowed top hat.
Kapitza's enthusiasm attracted other students, and a lucky thirty were invited to the "Kapitza Club," which met in his rooms every Tuesday evening for milky coffee and boisterous debate. Above all, Kapitza came to idolize Rutherford, calling him "the crocodile" for "in Russia the crocodile is the symbol for the father of the family and is also regarded with awe and admiration because it has a stiff neck and cannot turn back. It just goes straight forward with gaping jaws—like science, like Rutherford." He could twist Rutherford around his finger, winning concessions that others would not even have dared to seek. Kapitza's great interest was creating magnetic fields of greater and greater power. In 1928 he was put in charge of the Cavendish's new Department of Magnetic Research.
Peter Kapitza (left) and James Chadwick at Chadwick's wedding in 1925
Rutherford had become convinced that using subatomic particles naturally emitted by radioactive substances as projectiles to smash atoms was too limiting. The particles lacked the energy to barge through the electrical defenses of the nucleus. Under Rutherford's guidance and with industrial help, two of the Cavendish team, John Cockcroft and Ernest Walton, began developing machines—today known as "accelerators"—that would use high voltages to hurl particles at sufficient speed to penetrate the nuclei of the target.
Elsewhere, others were having similar ideas. In the United States, at MIT, Robert Van de Graaff was building a huge electrostatic device, while at the University of California at Berkeley, Ernest Lawrence, a young experimental physicist from South Dakota, was planning the world's first "cyclotron"—a machine combining electric and magnetic fields to send particles spiraling away at high speed. He was determined to invade the nucleus, sitting snug behind its protective screen of electrons like, as he put it, "a fly inside a cathedral."
Lawrence was an extrovert of overpowering drive and energy, much like Rutherford as a young man. He also had some of Rutherford's intuition, and this had helped him conceive the cyclotron. In 1929, the year of the Wall Street crash, Lawrence came across an article by Rolf Wideroe, a Norwegian engineer working in Germany, describing a linear device that would accelerate charged particles down a straight tube—similar to the approac
h being pursued at the Cavendish Laboratory. Lawrence's German was not good enough for him to understand everything Wideroe had written, but as he studied the accompanying diagram, an inspirational thought struck him. If he could confine particles with electromagnets within a circular track, rather than pushing them along a straight line, he could accelerate them indefinitely, causing them to whizz faster after each burst of voltage. It would, in his words, be a "proton merry-go-round." He told his friends, confidently—and accurately as it turned out—"I'm going to bombard and break up atoms!" "I'm going to be famous."
Lawrence's first machine was "a four-inch pillbox sprouting arms like an octopus." When he demonstrated it to the U.S. National Academy of Sciences, he secured it in place on a kitchen chair with a clothes hanger. Despite its absurd appearence, its potential caused a sensation. Newspapers hailed the invention of a device "to break up atoms," and they were right. So good was his progress that by the end of the 1930s Lawrence would build a cyclotron with a magnet weighing 200 tons. Inspired by the desire to explore one of the tiniest things in existence, the nucleus of the atom, big science was coming.
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While the creators of the new atom-smashing machines honed their early designs, quantum mechanics continued to forge bridges between Europe and the United States. Just as young Americans eager to understand the new theories were flocking to Arnold Sommerfeld in Munich, Max Born in Gottingen, Werner Heisenberg in Leipzig, and Niels Bohr in Copenhagen, European scientists were touring the United States to spread the word. The big names like Einstein were eagerly sought, but so too were younger scientists. The Hungarians John von Neumann and Eugene Wigner were invited as guest lecturers. Their task, in Wigner's words, was "to modernise" America's "scientific spirit." They saw themselves as "pioneers who break new ground"; their mission, to make quantum mechanics and relativity theory a reality to people to whom it was still "an abstraction."