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Karl Giberson

Mr. Uncertainty: Part1: The battle over Heisenberg.

Click here for Part 2 of this article.

Now we're all dead and gone, yes, and there are only two things the world remembers about me. One is the uncertainty principle, and the other is my mysterious visit to Niels Bohr in Copenhagen in 1941. Everyone understands uncertainty, or thinks he does. No one understands my trip to Copenhagen.

—Heisenberg, in Copenhagen,1 Act 1

The Spy

Moe Berg was a third string catcher for the Boston Red Sox, on the same team as Ted Williams. He was sophisticated, especially for a professional athlete, having been educated at Princeton; he spoke several languages and was something of a ladies' man. During World War II he spied for the Allies. His life makes for quite an adventure, and several biographies of Berg (both for adult readers and for juveniles) have been published in the last five years alone, in addition to earlier ones. At the present time George Clooney is reportedly in conversation with Warner Brothers about adapting one of these biographies2 for the big screen. Clooney will play Berg.

One of the first biographies of Berg was Moe Berg: Athlete, Scholar, Spy, originally published in 1974, and rereleased in 1996.3 A copy of the original book, which contained a number of pictures of Berg, was sent to the great German physicist Werner Heisenberg, who had headed up Hitler's nuclear physics program during the war. An astonished Heisenberg recognized Berg in the photos as a "Swiss acquaintance who had accompanied him to the hotel, who had listened so attentively in the first row during his lecture" and had later asked "such intelligent and interested questions."4

It turns out that Berg was not Swiss, and his interest in what Heisenberg had to say was rather sinister. The catcher-turned-spy sat in the front row of that small lecture hall in neutral Switzerland with a loaded pistol in his pocket under orders to shoot Heisenberg, if the infamous Nobel Prize-winning physicist had said anything that indicated he was making progress on building a bomb for Hitler. Satisfied that Heisenberg was not in fact making meaningful progress on a German atomic bomb, Berg kept the gun in his pocket.

Berg's judgment was validated by a remarkable revelation that came to light when the Allied forces invaded Germany and captured the leading physicists: despite the fact that basic bomb physics had been discovered in Germany in 1938, despite the fact that Heisenberg, arguably the world's greatest physicist at the time (Einstein and Bohr having passed their prime), was working on nuclear physics for Germany, despite the very long tradition of German superiority in physics—despite all this—the Germans had made virtually no progress on the atomic bomb, while their American counterparts, sequestered on a mesa in the New Mexico desert, had succeeded. The results in Germany were simply pitiful.

What had gone wrong? Why was Germany unable to make even nominal progress on a bomb despite the conviction of a number of his former colleagues working for the Allies that if anyone could build a bomb, it would be Werner Heisenberg? Did he, as he later claimed, deliberately sabotage German physics because of moral scruples about making a bomb for Hitler? Or, as others have argued, did he work as hard as he could to build a bomb for Hitler, but make a number of simple mistakes that were not caught in time? This is the Heisenberg enigma, still unresolved after a half century of heated debate, still generating passionate responses—including most recently the British playwright Michael Frayn's Copenhagen, which opens in New York this spring.

The endurance of the Heisenberg mystery is nothing short of astonishing. There is a rich paper trail documenting almost everything he did in Germany; there are hundreds of pages of secret recordings made without his knowledge; there are countless interviews with people who knew him well; there are memoirs written by his wife, volumes from his own hand, commentary from his associates. And yet the mystery remains unsolved, a black hole of intrigue that continues to pull historians tightly into its orbit. What exactly was Heisenberg doing in Germany during World War II?

Some questions remain long after their owners have died. Lingering like ghosts. Looking for the answers they never found in life.

Margrethe Bohr, in Copenhagen, Act 1

Boy Wonder

The story of Werner Heisenberg starts out as the story of the development of quantum mechanics, the most complex intellectual revolution in the history of physics and arguably the most amazing theory in the history of science. No other theory has been as difficult to develop, as complex to interpret, and as metaphysically suggestive as quantum mechanics.

Quantum theory emerged as an attempt to understand electromagnetic radiation, of which light is the most familiar example. At the turn of this century, radiation was understood to be a wave, and we still use terms such as "radio waves" for one particular portion of the electromagnetic spectrum. But Max Planck discovered in 1900 that energy was also, in some strange sense, a particle. A hot object, as it cooled, emitted what seemed to be particles of energy; we call them photons now. The question naturally arose, Was light then a particle or a wave?

Strangely, the answer depended on the context in which one was observing or measuring it. One could do "wave physics"—pass waves around posts or through openings that would give rise to interference patterns— and the radiation would always behave like a wave. One could do "particle physics"—have particles hit detectors or go through various openings—and the radiation would always behave like a particle. All this happened without apparent contradiction, for one could design no experimental setup that would simultaneously look at waves and particles. This dual character of electromagnetic radiation became known as the "wave-particle duality."

A French historian-turned-physicist, Prince Louis de Broglie argued, in a seven-page doctoral dissertation so short, so speculative, and so odd that his advisor sent it to Einstein for review, that maybe this "wave-particle duality" of light could clarify the nature of electrons. De Broglie's suggestion, later borne out by experiment and rewarded with a Nobel Prize, was that the electron, which had always been thought of as a particle, might also be, in some way that could not be pictured, a wave. Just as wave-like radiation had suddenly taken on a new particle-like aspect, so the particle-like electron was adding a new wave-like aspect. Long live symmetry and the ghost of Pythagoras.

De Broglie's wave-particle duality became a cornerstone of the new quantum physics and Janus-like progress occurred as physicists alternately uncovered waveness in nature and then particleness, but never both together. Along the way it became clear that these small bits of reality—the photons and the electrons—really could not be modeled in any meaningful sense of that term, and that reality—itself now a complex concept—simply could not be pictured at the level of the very small.

The atom, for example, was not appropriately modeled as a miniature solar system, as had been recently popular (and as introductory texts continued to picture the atom even decades after the quantum revolution). Familiar "orbits" in which little electronic "planets" circled heavy nuclear "suns," were replaced by "orbitals"—ephemeral, wave-like clouds of purely mathematical probability, wrapped around and even through the nucleus of the atom, like fog on a lake.

So the atom, which had been thought to be only slightly more complicated than a marble with a hook on it, had suddenly and mysteriously retreated into a deep Platonic cave, cloaking itself with an epistemologically opaque mathematics. It appeared that there was no way to describe, in the traditional sense, just what the electron was doing, and that the best one could hope for was an explanation of how the atom behaved when it happened to do something observable, like kicking out an electron that might go on to light up a bit of phosphor on a television screen.

The world was undergoing a strange bifurcation in which straightforward, measurable effects were mysteriously emerging from a different reality, somehow beyond the grasp of our experientially limited imaginations. An extraordinary team of revolutionary physicists from all over Europe was meeting regularly as they searched feverishly for a proper theory of the atom—a theory that would both ex plain what atoms did when they were being observed but also, hopefully, what they were doing when nobody was watching. Some, like the great Austrian Erwin Schrodinger, thought the key was the new wave-like character of electrons, which he envisioned as somehow wrapping around the nucleus; others, like Albert Einstein, wanted to ensure that the final result would be a classical theory in the tradition of Isaac Newton, James Clerk Maxwell, and his own groundbreaking works in relativity; Niels Bohr, the greatest of Danes, was certain that a decisive break with the traditional classical physics would be required; and the brilliant and eccentric Austrian Wolfgang Pauli discovered his famous "Exclusion Principle," which stated that every individual electron in an atom had to be in a different configuration. This simple rule explained all the regularities of the chemists' periodic table of the elements, but it did little to help with modeling the atom. So many pieces, and yet no picture.

There is a rich paper trial, and yet the mystery remians unsolved. What exactly was Heisenberg doing in Germany during World War II?

But there were voices beginning to argue against the search for a "picture," considering that search to be motivated by a quixotic fascination with the Newtonian, billiard-ball model of the world. The September 1925 issue of Zeitschrift fur Physik—one of the world's premier physics journals—contained a 15-page article by the boy wonder of quantum physics, Werner Heisenberg. The paper laid the foundations for an entirely new theory of quantum mechanics—you could plug simple numerical information such as masses, charges, and forces into mathematical entities called matrices and crank out more interesting and experimentally measurable quantities such as the frequencies of the emitted spectral lines.

Heisenberg developed the theory on the tiny, barren, resort island of Helgoland, off the German coast, where he had gone to recover from an attack of hay fever. He was alone with the waves, the horizon, the boulders, and a mysterious new mathematics5 in which A times B was not the same as B times A. Heisenberg was 24, the age when most physicists are hoping to get admitted into a doctoral program.

So what was Bohr? He was the first of us all. Modern atomic physics began when Bohr realized that quantum theory applied to matter as well as to energy. 1913. Everything we did was based on that great insight of his.

—Heisenberg, in Copenhagen, Act 1

On to Uncertainty

Heisenberg's revolutionary quantum mechanics—which was squarely in the particle camp—was eclipsed the following year by Schrodinger's "wave" theory, which was much easier to use. The two theories were quite different, and they (and their creators) competed vigorously for a while, even as physicists tried to figure out what the theories actually meant.

Heisenberg wrote to Pauli that Schrodinger's theory was "crap." But then Schrodinger proved that the two theories were actually mathematically equivalent, in spite of their apparent differences. (This of course implied—with mathematical certainty—that Heisenberg had inadvertently called his own theory "crap"!) In the end Heisenberg's formulation lost out because it was harder to use, more abstract, and even more difficult to interpret than Schrodinger's wave mechanics, if that were possible.

The problem of how to interpret quantum mechanics continued to puzzle physicists. Einstein constantly challenged Bohr on the emerging interpretation of quantum theory—an interpretation which increasingly emphasized indeterminacy and probability. His challenges were ingenious and epistemologically profound, but Bohr, who had developed the very first, primitive "quantum model of the atom" and then mentored almost everyone in the field, countered all of Einstein's objections successfully, defending both quantum theory and his role as its "guru." Einstein never conceded defeat and took his intuition that there was something wrong with quantum theory to the grave. To date nobody has been able to find anything to confirm Einstein's now infamous intuition that "God does not throw dice."

Quantum theory is the most epistemologically difficult theory in all of science, forcing a reinterpretation of what it means to say that we are observing the world. Somehow, when we make a measurement on a quantum system, such as the humble atom, the very act of measurement forces that system to assume a particular configuration in which it may not have been prior to our observation. When we measure the position of an electron by shining light on it, the light bounces off the electron and sends it skittering away to a new location. If we measure the position with a long-wavelength, low-energy photon, the electron is not as significantly affected, but the long wavelength of the photon means that we don't actually know the position of the electron very accurately. If we use a short-wavelength, high-energy photon, then the electron will be much better localized, but the interaction with the photon will send the electron careening away at a much higher speed. And so on.

It is as though one were trying to locate a billiard ball by either rolling a basketball at it or throwing a baseball at it. The size of the basketball gives a bit more uncertainty as to where the billiard ball is located, but does not make it roll away as fast as the baseball would. When it comes to electrons this implies that the more accurately you measure the position of the electron, the more you change its momentum, or speed.

The precise articulation of this limitation on how well we can know the quantum world is enshrined in Heisenberg's most significant contribution to physics—the celebrated Uncertainty Principle. Mathematically it looks like this:

Dx Dp³ h/4P

which, being translated, means that the uncertainty in our knowledge of the position of a particle, multiplied by the uncertainty of our knowledge of the momentum, is always equal to or greater than h/4Š, where h is Planck's constant, a very, very, very small number. That Heisenberg was able to precisely quantify the indeterminacy in this way was truly remarkable.

Indeed, the Uncertainty Principle enshrines one of science's greatest in sights into the nature of reality, and the idea itself, like democracy, mono theism, and relativity, certainly ranks with some of the greatest ideas of all time. For ex ample, when one goes looking for the roots of postmodernity, the celebrated Heisenberg Uncertainty Principle is one of the signposts that keeps appearing, albeit generally misinterpreted.

Germany is where I was born. Germany is where I became what I am. Germany is all the faces of my childhood, all the hands that picked me up when I fell, all the voices that encouraged me and set me on my way, all the hearts that speak to my heart.

—Heisenberg, in Copenhagen, Act 1

The Life and Times

David Cassidy has written the standard biography of Werner Heisenberg, Uncertainty: The Life and Science of Werner Heisenberg,6 which won the 1992 American Institute of Physics Science Writing Award in Physics and Astronomy. Perhaps the leading American scholar on Heisenberg, Cassidy is a professor of the History of Science at Hofstra University, Long Island, New York. In addition to Uncertainty he has contributed to a number of other accounts and analyses of the enduring cultural enigma that is Werner Heisenberg.

Cassidy's 600-plus-page treatment provides insights into Heisenberg's early development that shed some light on his controversial decision to remain in Germany during the war. Of particular interest is the young Werner's developing insecurity, to which he responded by cultivating an inner life to which he could retreat. This inner world was highly ordered—math, science, Mozart—and never betrayed him, as did his outer world—family, friends, and country.

Never a social child—"No evidence survives of any childhood playmate," Cassidy remarks—Heisenberg nonetheless became a leader in the German youth movement, the Pathfinders. His experiences leading "Gruppe Heisenberg" shaped him in important ways, from developing a passion for the beauty of the German countryside, to embracing a detached and critical stance vis-a-vis the "decadent" and self-absorbed German society of the day. By the time he was 20, Heisenberg had come to view physics, nature, and music "as belonging to a higher plane of existence and truth that somehow transcended the ephemeral dirty world of politics."

It is important to note that this "detachment" from local political realities occurred well before Hitler came to power. And, as it turned out, virtually none of the members of Gruppe Heisenberg joined the Nazi Party when it became expedient to do so. (This is clue number one to the Heisenberg mystery.)

Heisenberg's ascendancy came through his work in quantum mechanics. Wolfgang Pauli—also destined for enduring greatness—emerged as Heisenberg's sharpest and most helpful critic, replacing his estranged older brother as the closest thing to a soulmate. Heisenberg shone so brightly and so early that Bohr took the wunderkind under his wing, and soon senior members of the German physics community began to negotiate on his behalf to help him land a prestigious research appointment. But two odd controversies emerged even as Heisenberg's star rose. The first was the legitimacy of Heisenberg's brand of purely theoretical physics. The German tradition was one that demanded excellence in both theory and experiment. Heisenberg almost flunked his doctoral exams when his experimental physics instructor, Wilhelm Wien, discovered that the 21-year-old math whiz couldn't answer some very basic questions about telescopes and batteries. Luckily the "F" that Wien gave Heisenberg was averaged with much higher grades on the other parts of the exam. This total apathy toward experimental, applied, "hands-on" physics certainly contributed to Heisenberg's later difficulties in making progress on building an atomic bomb.

Heisenberg's purely theoretical approach to physics stands in contrast to that of colleagues like Enrico Fermi, who was outstanding in both theory and experiment—and who, not coincidentally, was able to move rather efficiently toward creating the atomic bomb. (This is clue number two.)

The second controversy that surrounded Heisenberg was rather different, yet curiously related to the first. A strange movement among some leading German physicists, including the Nobel Prize-winners Phillip Lenard and Johannes Stark, challenged the increasing dominance of theoretical, or highly mathematical and abstract, physics. This movement tried to make a distinction between "German" physics, rooted in a long tradition of careful observation of the natural world, and "Jewish" physics, which emphasized elegant mathematical formulations that sometimes could not be visualized in the simple way that had long characterized physics done in the classical, Newtonian tradition. The attack on Jewish physics was so strident that it became dangerous to mention Albert Einstein's name and even to make use of his theory of relativity.

Heisenberg was very discouraged by this bizarre politicization of his beloved physics. And his seminal work in quantum mechanics was the worst kind of "Jewish physics." Heisenberg's breakthrough in quantum mechanics came when he explicitly abandoned any constraint that his new theory of the atom should be based on a model that could be visualized. He was highly critical of the prevailing Bohr/Rutherford model, which pictured the atom as a miniature solar system, with tiny planetary electrons orbiting about a massive nuclear sun. There is absolutely no observational evidence that electrons "orbit" about a nucleus, so a theory should not have to support this old-fashioned notion. But the Bohr/Rutherford model enjoyed an intuitive appeal that Heisenberg's mathematical approach patently did not—hence the attacks on Heisenberg as a "White Jew." (This is clue number three.)

In October 1927 Heisenberg was appointed to the Leipzig chair for theoretical physics. Four months later, at the age of 26, he became Germany's youngest full professor. A few months later he published his celebrated paper on the Uncertainty Principle, one of the seminal pieces of physics in this most remarkable century of scientific advance. The formal structure of quantum mechanics was now complete in the sense that the theory could identify correctly the various things that atoms do, such as emit and absorb radiation of certain energies, or lose and gain electrons. However, it turned out that there was much work to be done trying to interpret the meaning of quantum mechanics in a philosophical sense.

It is in the speculative philosophical richness of quantum theory (and the associated Uncertainty Principle) that we find the reasons for Heisenberg's enduring stature as one of the great minds of this century. And Heisenberg, together with Bohr, lost no time in taking the quantum message to the larger culture. In 1929, for example, we find Heisenberg, not yet 30 years old, delivering a paper to the Vienna Circle entitled "Causal Law and Quantum Mechanics." He called for a repudiation of Kantian epistemology and a new understanding of what it means to "know" things about the world. That same year he toured the United States as a newly minted quantum celebrity. Lectures he gave at the University of Chicago became the basis of his first book, The Physical Principles of the Quantum Theory, which exerted a considerable influence on the interpretation of new quantum mechanics.

In 1933 Heisenberg received the Nobel Prize. Except for the occasional complaint that his physics was a bit Jewish, he was at the top of his profession, arguably the most important scientist in physics, at the very time when physics was at the peak of its vitality and international relevance. In that same year Adolf Hitler came to power and set in motion an astonishing sequence of events—events that gathered everyone in Germany into a maelstrom of confusion, moral chaos, and ambiguous terror. Heisenberg would spend the rest of his life trying to free himself from his role in what was about to occur.

Cassidy chronicles the tragic anti-Semitic dismantling of the once-great German science. In a tale that is by now all too familiar, Jews began to lose their freedom, their jobs, and finally their lives. Heisenberg looked on in uncomprehending astonishment as, one after another, brilliant Jewish scientists lost their positions and were replaced by men of far less ability who were members of the Nazi Party. (Heisenberg himself never joined the party.) He lamented the ill treatment of his colleagues, and tried to help in a few cases, but somehow never saw his way clear, until after the war, to condemn Nazi excesses, except in the vaguest language. His focus narrowed to self-preservation. At one point the persecution of Heisenberg became so great that his mother intervened on his behalf by taking a letter to Himmler's mother. The persecution stopped. (Another, highly ambiguous, clue.)

In 1935 Heisenberg wrote to his mother, "The world out there is really ugly, but the work is beautiful." His world shrank until its boundaries barely and rarely extended beyond physics. In his role as the leader of the German physics community, he managed to slow the extraction of Jewish physics, and he worked on some new physics of cosmic rays. In January of 1937 he met Elizabeth Schumacher, whom he married four months later. Nine months later Elizabeth gave birth to fraternal twins, Wolfgang and Maria. The boy was named after Wolfgang Pauli, who congratulated his old friend on his "pair creation."7

Meanwhile, leading physicists had begun to flee Nazi Germany, many with the assistance of Bohr, himself partially Jewish. The roster of great physicists who fled to freedom in the United States is extraordinary—Fermi, Hans Bethe, Max Born, Walter Heitler, Eugene Wigner—all of them Nobel Prize-winners. It was a veritable brain drain, and there is no doubt that the transplanted expertise in physics made it possible for the United States to build the first atomic bomb. Other countries, especially England, also benefited from the exodus.

Heisenberg stayed. He discovered the surprising and inconvenient depth of his roots in the German soil of his happy childhood. He knew that the Nazi regime would disgrace his country, but he could not reduce his country to its political leaders. He had hiked in the hills of Germany, had swum in its streams; he had mastered its music, and studied its philosophy; he had risen through the ranks of its world-renowned educational system. His children were German, and he wanted them to stay that way. He was a prestigious leader of German science surrounded by young graduate students in whom he saw the future of a German physics that would be reborn after the Nazi-induced hibernation. He made the fateful decision to stay in Germany and wait for things to take their course, after which time he would contribute to the restoration.

On a tour of the United States in 1939, Heisenberg was asked by Enrico Fermi's Jewish wife why he would not stay in America. "Germany needs me" he said, less than three months before the formal declaration of World War II. (Another clue.)

In Inner Exile: Reflections of a Life with Werner Heisenberg, Elizabeth Heisenberg wrote,

In August of 1939, Heisenberg returned to Europe aboard the last ship from America. It was almost empty. After all, who returned to the madhouse in Germany of his own accord? It is easy to understand why the Americans formed the wrong opinion on this move, and decided Heisenberg was a hidden Nazi, after all.

During the war Heisenberg worked in Germany on nuclear physics. It was clear from the discovery of nuclear fission by Otto Hahn in 1938 that it ought to be possible to get energy out of uranium; building a nuclear reactor, perhaps to power submarines and ships for the German navy, seemed like a relatively straightforward research problem. Building a bomb looked a bit harder.

In 1941 Heisenberg made a trip to Copenhagen in occupied Denmark that remains the subject of much speculation. He went to lecture and talk about physics with Bohr. While he was there, he and Bohr went for a long walk and talked about nuclear weapons. Historians continue to argue about this meeting, "still shrouded in controversy and questions," as Cassidy remarks. (Another very controversial clue.)

According to Heisenberg's postwar account, he went to see his mentor Bohr to enquire whether "as a physicist one has the moral right to work on the practical exploitation of atomic energy." Bohr's recollection is that Heisenberg was probing to see what kind of progress was being made elsewhere on the bomb and whether Bohr might use his considerable influence to discourage such efforts.

At the time of their meeting, Germany was clearly winning the war and it is entirely possible that Heisenberg thought it would soon be over. However, World War I had bogged down in the trenches of France, and Heisenberg may have been worried that some such eventuality would give the Americans time to build an atomic bomb—a bomb which would almost certainly be used to turn his beloved Germany into a radioactive wasteland.

Heisenberg continued to work on nuclear physics for the German government. (Meanwhile, at Los Alamos, Heisenberg's former colleagues, students, and teachers were building the atomic bombs which were ultimately dropped on Japan to end the war.) He grew increasingly demoralized by the behavior of the Nazis, but he had staked his future on Germany and, for better or worse, he would stand by the Fatherland. When he was approached about getting involved in the plot to kill Hitler, he declined. Several of the principals who were executed for the attempt were close associates. (Another important clue.)

In 1944, as it became increasingly clear that Germany was going to lose the war, Heisenberg traveled to neutral Switzerland, where he lectured on "S-Matrix Theory," an application of quantum mechanics that had nothing to do with bomb physics. The choice of this topic was somewhat fortunate, since this was the lecture that included Moe Berg in the audience.

On May 3, 1945, four days before the German surrender, on what he regarded as "the most important single intelligence mission of the war," Colonel Boris Pash of the U.S. Army arrested Heisenberg at his cabin overlooking the lake in Urfeld. A relieved and cooperative Heisenberg introduced his captors to his family and said goodbye, expecting to see them again shortly. It would be eight long, strange months before he got his wish.

The details of Heisenberg's arrest provided by Cassidy differ in a few minor respects from those provided in Elizabeth's memoir. But she recalls that "the American soldiers looked like liberators from a horrid nightmare." Three days earlier, she recalls, she and Werner had drunk a bottle of wine in celebration of the news that Hitler was dead. (Another clue.)

What happened next has contributed greatly to the controversy about Heisenberg and his wartime activities. Heisenberg and nine other leading German scientists, who were all—with one or two exceptions—thought to be connected to bomb research, were arrested and interned at a British country house called Farm Hall. Part of the reason for this remote location was to keep these valuable commodities from being "liberated" by the Russian army entering from the east. The Cold War had begun.

Farm Hall was a posh prison. There were tennis courts, a grand piano, books, daily newspapers, excellent food—and bugging devices everywhere that recorded their conversations, including those that occurred in response to the news from the BBC broadcast about the bombing of Hiroshima and Nagasaki. The tapes of these conversations, which came to be known as the Farm Hall Transcripts, remained classified until 1992 and have now become a critically important part of the Heisenberg mystery.

Heisenberg was detained at Farm Hall "at his majesty's pleasure" for six months, the maximum allowed by British law for imprisonment under this obscure provision. On January 3, 1946 he was returned to his disgraced, destroyed, yet beloved Germany, where he rejoined his remarkable wife and began the task of picking up the shattered pieces of German science.

Cassidy's massive account of Heisenberg's life ends with a whimper. His final chapter opens in 1946, when Heisenberg was 45, and closes a few pages later with his death in 1976. It is the story of the endgame of a truly great scientist. Heisenberg wrote memoirs, delivered the Gifford Lectures in 1956, and consulted with the German government on the best way to rebuild German science. He worked with scientific foundations and mentored young scientists.

The weakness of Cassidy's otherwise excellent biography is in this superficial coverage of the last part of Heisenberg's life. For it was during those 30 years that Heisenberg moved clearly into his role as a cultural icon whose influence extended far beyond the precincts of the scientific community. His name and above all his Uncertainty Principle were invoked in Zen primers, in avant-garde poetry, in manifestos calling for a new social order. His books for a popular audience, mingling physics and philosophy with a quasi-mystical bent, might keep company with a Jefferson Airplane album, the Last Whole Earth Catalogue, and a battered copy of Being and Time.

But all the while there was an undercurrent of dissent, focused not on Heisenberg's stature as a physicist (that was never in doubt) nor on pop understandings of quantum uncertainty (though critics there were) but on his role as a scientist in service to the Nazi regime. Was Werner Heisenberg, when all was said and done, Hitler's accomplice? That question simply wouldn't go away.

Next issue: The battle over Heisenberg.

Karl Giberson is professor of physics at Eastern Nazarene College.

1. Michael Frayn, Copenhagen (Methuen, 1998).

2. Nicholas Dawidoff, The Catcher Was a Spy: The Mysterious Life of Moe Berg (Pantheon, 1994).

3. Louis Kauffmann, Barbara Fitzgerald, and Tom Sewell, Moe Berg: Athlete, Scholar, Spy (Little, Brown, 1974).

4. Elizabeth Heisenberg, Inner Exile: Reflections of a Life with Werner Heisenberg (Birkhauser, 1984), p. 97.

5. New to Heisenberg, that is—but surprisingly it turned out to be a branch of the mathematics of "matrices," which had been around for some time.

6. David C. Cassidy, Uncertainty: The Life and Science of Werner Heisenberg (W.H. Freeman, 1992).

7. The joke about "pair creation" alludes to a process in particle physics whereby a particle and its anti-particle appear seemingly out of nowhere. In reality, their arrival is "paid for" by energy that changes form, from radiation to material particles.

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