In the midst of Berlin’s chaos, a problem entirely of his own making tormented Einstein. As so often happened with Einstein, what he saw as a problem would have struck many others as a solution. Switzerland had offered him an escape hatch from Berlin. Einstein, however, wanted to say No. But the Swiss were so nice and the Germans so barbarous that he hated to be rude and snub a generous offer. He needed a way to say No and Yes at the same time. Einstein had once built a theory on the idea that an object can seem to be both at rest and in motion, so if anybody could find a No-Yes answer he was probably the one. But no solution jumped at him.

There were Berliners who hoped Einstein would stay, but they understood all too well why he or any other person would grab the opportunity to flee. Germany was up for grabs. Strange prophets with odd ambitions had begun to appear even before the war ended, and the moment the Kaiser fled they began pressing their way toward the center ring. On the very first Sunday following the armistice, a man of distinctly proletarian face, with short-cropped hair, creases in his cheeks, and exhaustion beneath his eyes, entered the city’s Protestant cathedral. He was Johannes Baader, and he waited calmly in the church’s pseudo-Italian setting. The ornate decor would surely have horrified Martin Luther—Saint Martin, the cathedral’s artwork seemed

to make him. Then, as the pastor was about to begin his sermon, Baader rose and shouted out, “Just a minute. I’m asking you what Jesus Christ means to you …”.

He had more to say but already there was a commotion. Baader was seized and silenced. The authorities wanted to charge him with blasphemy, but the speaking notes he carried demanded only greater respect for Jesus. The next day Berlin’s newspapers were full of tales of Baader’s “insult” to propriety. Baader was one of those strange prophets, a member of the Dada movement, trying to rescue Berlin.

Dada was provocateur art that sought to replace “bourgeois” Europe with the ideals of international art. Its aims cannot be defined more precisely. The previous summer, in a famous statement of enthusiastic contradiction, the Berlin Dadaists had issued a manifesto that concluded, “To be against this manifesto is to be a Dadaist!”

That was Dada’s version of a Yes-No reply, and if Einstein thought he could get away with saying, “To reject Zürich’s offer is to accept it,” he probably would have tried. Might the land of strict accounting and precision clocks accept such an answer? Well, Zürich was Dada’s birthplace. Guarded by the Alps, neutral Zürich had long avoided the fates of Paris and Berlin, cities on the plains where armed warriors found easy maneuver. Lenin and James Joyce were Switzerland’s most famous anti-war refugees, but many anonymous ones had come there as well to express, under authority of their own souls, their visions. Some anti-warriors with artistic imaginations had, at a boîte called the Cabaret Voltaire, begun a protest movement that spread to the warring capitals on both sides of the battle lines. When the war ended, Dada and communism were the only radical movements found in both the conquered and conquering nations. Communism was already becoming a Soviet tool, but Dada remained a decentralized, international movement. It marked postwar Germany’s encounter with romantic irrationality.

One of Dada’s earliest statements boasted, “The Cabaret’s role is to remind us that, beyond the war and nationalities, there are independent men who live by other ideals.” It sounds like a movement Einstein could have joined, and, indeed, he was as independent and as anti-national as any Dada poet. Einstein saw science the way Dada’s

proponents saw art, as an alternative to military madness, and like the Dadaists he hated nationalism. “What is truly valuable in our bustle of life is not the nation,” he said, “but the creative and impressionable individuality, the personality.” Dadaists across Europe took that doctrine of personal authority as truth’s one sure point. Einstein, too, believed in a community of hard-toiling laborers at imagination.

Yet Einstein and Dada could never have made common cause. The Dada Manifesto, issued in Zürich during the summer of 1918, proclaimed, “Logic is complication. Logic is always wrong. It draws the threads of notions, words, in their formal extension, towards illusory ends and centers. Its chains kill; it is an enormous centipede stifling independence.” Einstein understood their point. He had been engaged in deeply creative thinking for perhaps 20 years and had produced a series of wonders—showing how to count atoms with a schoolhouse microscope; abolishing the notion of an elusive, universal substance called the ether; abolishing, too, the ancient belief in absolute space and absolute time; redefining how light interacts with matter; redefining gravity—and he liked to say that his creative work had not been logical. “Invention is not the product of logical thought,” he insisted, and a Dadaist would have understood, but then Einstein added, “even though the final product is tied to a logical structure.”

Logic for Einstein was not hackwork, not a mechanical procedure for generating information, and definitely not the Dadaists’ hated military commander who ordered people where to go. Logic, in Einstein’s eyes, was a map showing the limits of the understood. A great explorer like Sir Richard Burton looked at a chart and saw some empty spot, possibly decorated with a fanciful annotation like “Here there be tygers,” and he said to himself that’s where he would go next. So Burton scouted out Mecca and Lake Tanganyika. For Einstein, the tygers were places where logic had no more to say. His greatest papers often began by noticing a paradox, a point where logic contradicted itself. Then, just as a composer resolves two contradictory themes by inventing a unifying symphony, Einstein would unify his physical themes behind a new language for describing the world. Yes/no. What was the music that would unify them?

When the Great War ended, radiation was the uncharted territory

facing physics. Newton’s mechanics had considered matter—the heavy stuff that falls when you drop it, sits still when you set it down, and rolls on forever if you hurl it through empty space. In his early years Einstein had done radical work on matter, but he soon saw that the most revolutionary mysteries had to do with light, heat, energy—all those immaterial enigmas that physicists lumped together as radiation. As science’s boldest explorer, Einstein was hoping to unite radiation and matter under one grand theory, but when it came to science, he was not a lunatic adventurer, not one of those mad Englishmen who went gloriously off the map only to discover that the team should have brought warmer clothing. Einstein knew that he needed to understand more about radiation and what it was.

In his younger days when he wanted to understand some profound mystery, Einstein would retreat into the temple of his mind until finally he could reemerge with a prophetic message. The rest of the physics world would gape, wonder if the revelation could be true, and then discover that Einstein had announced something so real that he had birthed a whole new branch of physics. How did Einstein do that? The goings on in the temple were hidden behind a veil and Einstein’s method was as undiscoverable as Shakespeare’s or Michaelangelo’s. But by the war’s end Einstein was not quite so invisible. The next dozen years would reveal the great scientist struggling openly with a great mystery. As the story of an individual those years would show how Einstein made war on his own ignorance. On a larger scale it showed how scientific imaginations in general wrestle with nature. On a still larger and even more general level it showed how difficult and wondrous it is for every sort of dreamer to create new things, and why reason is part of any fruitful imagination.

For Einstein the war had exposed unreason’s price and he had no sympathy for those groups, whether they called themselves artists or patriots, who were trying to organize the postwar under one of irrationality’s many banners.

“Say yes to a life that strives upward by negation,” the Berlin Dada Manifesto called, “Affirmation: negation: the gigantic hocus-pocus of existence fires the nerves of the true Dadaist—and there he is, reciting, hunting cycling—half Pantagruel, half Saint Francis, laughing and laughing!” In short, exalted Dada, Yes-No.

How different was the speech made that revolutionary November by Berlin’s leading scientist, Max Planck. Bald and wiry, he appeared as sober as a bank examiner, yet there must have been something unconventional about him, for years earlier (in 1900) he had discovered radiation’s strangest mystery, the quantum. Now, in late 1918, while revolution tugged at Germany, Planck traveled past the Brandenburg Gate to the Prussian State Library—another of Berlin’s grand buildings completed just in time to greet the war’s outbreak. The Prussian Academy of Sciences met there and Planck had come to encourage the assembled savants to face the future with courage and confidence. Everyone in the room knew that behind the words, Planck’s own heart was broken. One of his sons, Karl, the one whom Planck had considered worthless and without purpose, had been killed at the front. It tore Planck’s soul to know he had never recognized his son’s value until it was lost. A few months later Planck had lost a daughter, Grete, from complications following childbirth. Even so, he kept a sober face before the Prussian Academy, telling it, “If the enemy has taken from our fatherland all defense and power, … there is one thing which no foreign or domestic enemy has taken from us: the position that German science occupies in the world.”

Einstein loved to laugh and his spirit united more of Pantagruel and Saint Francis than his colleagues dared recognize. There was also less of Einstein in Planck’s patriotic science than the Academy cared to acknowledge, but when it came time to bet, rouge ou noir, on Fortune’s spinning wheel, Einstein could be counted on to slip all his chips beside Planck’s. Einstein would never have phrased it so belligerently, but he agreed with Planck on German science’s importance. That was part of why he wanted to say Yes to Berlin, if only he could avoid saying No to Zürich.

Already, however, a new theme sounded softly in the back of the orchestra; Germany might have begun to say No to Einstein, No to science. A new book published the previous summer perfectly suited the new pessimism and the public’s doubts about reason. This was Oswald Spengler’s The Decline of the West, and the book was beginning a bestsellerdom that would take it through 30 printings in five years, and then another 30 printings following a new edition in 1923. The

book inspired constant comment among intellectual groups. Its gloomy doctrine held that European civilization—what Spengler called Faustian Culture—had passed its maturity and was entering an inevitable decline into senility and death.

Spengler’s word “Faustian” said baldly that the West had sold its soul to the beast in return for power. Western claims for science as eternal truth were vanity. Science, preached Spengler, was just as much the cultural moment’s product as painting or music, and at the Faustian lie’s heart sat the illusion that logical, fixed laws defined reality.

Einstein agreed that the war had exposed many lies. He was eager that still more of them should be publicized so that everyone could understand how false were the idols that had taken millions of their sons and brothers. Yet he was no nihilist; he believed with the confidence of a pope that the world makes sense and that it can make sense to us mortals. His ambition was the mystic’s quiet prayer: to find the face of What Is.

Before the war Berlin had been the best place for that pursuit, but now Europeans of all classes and education loathed Germany and Germans. Across the continent good people were shaking their heads over what to do about friends in Germany. In Holland the patriarchal figure of physics, Hendrik Lorentz, a slender old man with a vital face, drafted a letter to a Belgian patron asking,

That for ever gives the game away. Lorentz knew it was going to take some time before Germans were allowed back into the arms of international science.

Einstein knew it too, even sympathized with the attitude. Prussians were never his choice neighbors. He once told a friend, “These cool blond people make me feel very uneasy; they have no psychological comprehension of others. Everything must be explained to them very explicitly.” And then late in the summer, just before the war’s end, he was offered an escape via an unusual joint professorship at both Zürich University and Zürich’s polytechnic school. Einstein had graduated from the polytechnic and had taught previously at the university. He considered Zürich his true hometown. After he had renounced his German nationality (in 1896) he saved his pocket money until (in 1901) he could afford to apply for Swiss citizenship. Democratic, free Switzerland seemed to him the model for what a country should be. Besides, in Zürich he could work without the distractions of the allied blockade, the revolution, and the desperate starving people.

Einstein wanted no distractions. Physics had become as confused as German politics and it demanded a clear head. Newton’s and Maxwell’s great achievements had been reconsidered and, while not forced into abdication, placed under a new constitution. A mystery had been swallowing physics for almost 20 years now. At first Einstein had been perhaps the only one alive to realize what was happening, the way a sailor in the crow’s nest might be alone in noticing a storm thickening beyond the horizon. Max Planck had discovered the quantum, but Albert Einstein was the first to say aloud that the new quantum theory of radiation was revolutionary.

The mystery that was eating centuries of thought was as old as the dreams around campfires. When prehumans huddled beside a flame, listening to zebras barking out in the darkness, just what were they gathering round? Why did they feel warmer near the fire? Why could they see one another’s faces? If they knew, they forgot to pass along the answers to their children. The Greeks buried the problem by naming fire as one of the world’s basic building blocks. Its heat and light were just the way things were. Poets and mystics often use fire to express a duality, spirit, and matter, a soul that lives in the world and yet touches something invisible. When chemistry replaced alchemy, Lavoisier proved that fire is simply the rapid union of oxygen with a substance. The fire was the action of the chemical union, but this

understanding still left the mystery untouched. What was that burning light? What the heat? What the work that fire did? For thousands of years imaginations had played with the campfire’s dream and still the boldest dreamers asked themselves, What is this flickering thing, really?

The quantum notion was conceived during an attempt to understand how light is related to temperature. Planck’s interests had been abstract and theoretical, but they carried practical implications. Anybody who has ever seen pictures of a steel plant knows that its hot furnaces glow with a brilliant white light. As the flame reaches farther from the source of the activity, its color shifts to yellow shades and then to red. These color changes mark changes in light intensities at different temperatures. Planck derived a formula that linked energy (heat) and light. Using Planck’s math a person could, among other things, tell how hot a point in a steel furnace is just by measuring the light waves it gives off. But buried in Planck’s formula was the mystery that had shaken Einstein right through.

“What’s to be done?” Einstein had written his Swiss friend, Michele Besso, the previous August as he fretted over the offer to return in triumph in Zürich. At that time he was still tempted to just say Yes. “Difficult days of pondering lie behind me.” He added, “Proof: I dreamed I had cut my throat with a razor.”

Einstein could not expect his neighbors to thank him for risking his throat by staying put in Berlin. Planck would be pleased by his remaining, but few Germans had the mathematical imagination to appreciate Einstein’s importance. Most of them, like most of us, were unlikely to be moved by anything, no matter how bizarre, found in an equation, and they would not admire the way Einstein questioned equations as eagerly as poets question clichés.

Einstein’s success rested on his talent for finding the concrete meaning behind an equation’s abstractions. He had first startled physicists in the spring of 1905 when he published a paper offering visible proof that molecules and atoms really exist. In those days many chemists and a few physicists still considered atoms to be theoretical fictions. Einstein’s proof of their reality built on statistical ideas developed by a thick-bearded Austrian named Ludwig Boltzmann. Boltzmann was also a firm believer in atoms and Einstein sometimes wondered why

he had not found the proof first. It was a modest man’s question. Einstein’s creation required a special imaginative energy. Taking one of Boltzmann’s statistical equations (one that Boltzmann so loved, he had it carved on his tombstone), Einstein showed how it applied to everyday concepts like time and motion. Until then, Boltzmann’s formula had been used only to calculate remote abstractions like probability and entropy in gases. Einstein proved that Boltzmann’s abstract idea could be applied to visible things like pollen grains floating in water.

If you look through a microscope to inspect pollen in a water drop, you will see the grains moving in endless jigs and jogs known as Brownian motion. They jump this way and that, getting nowhere, yet never standing still. A botanist named Robert Brown had brought this seemingly perpetual motion to scientific attention in 1828. Did the motion result from something inside the little specks? Or was there something in the water causing the motion? Einstein took the second view and proposed that water molecules knock the pollen about. He made his theory so precise that a person holding a stopwatch and measuring the jigs could calculate the number of molecules in the water. In one short paper Einstein explained Brownian motion, proved the reality of molecules and atoms, and created a lasting technique for analyzing seemingly random fluctuations. Not bad for a patent examiner who couldn’t get a job teaching at a university.

Einstein’s great strength lay in that ability to find physical meaning in abstract ideas. A scientific “step,” as Einstein called these imaginative feats, meant going beyond the received wisdom to show that a fact said something deeper about reality itself. Einstein’s strides were the kind of insight long mytholigized in the story of Archimedes leaping from his bath. Supposedly Archimedes shouted “Eureka” when he saw past the banal fact that climbing into a tub causes the water to rise and recognized what was really going on.

It was this search for steps that explain physical surprises that kept bringing Einstein back to Planck’s quantum. Up in the crow’s nest Einstein had recognized an extra meaning behind Planck’s equation. To Einstein, Planck’s work was as amazing as it would be for a more ordinary thinker to learn that something fundamental about human psychology could be measured exactly by multiplying a person’s IQ

by some idealized, fixed batting average. The union is as contrary as Dada’s linking Saint Francis with Pantagruel. IQ is brain; batting average is brawn. Granted, brain and brawn might have some connection, but this isn’t even your brawn, it is some unchanging, one-size-fits-all batting average. Such an equation makes no sense. So if I told you that I could measure, say, your creativity by combining your IQ with a batting average, you would not take me seriously, but if for the next 20 years I showed you that more and more psychological traits could be measured precisely by multiplying IQs and batting averages you might begin to wonder what on earth was afoot.

Einstein sure wondered. He could have wondered in more comfort in Zürich, but he could not bring himself to leave Berlin. The Swiss offer forced Einstein to face a secret about himself. In Berlin he was admired but stayed always apart, always an outsider. In Switzerland, intimacy was easy, but Einstein finally admitted to his old friend Besso, “Here [in Berlin] everybody approaches me only to within a certain distance, so that life unrolls almost without friction.” He had developed a taste for the way the cool blonds left him alone. So it would be Yes to Berlin.

Left alone, Einstein could work on his mystery. Back in 1900 Planck had shown that by multiplying two things that had no business keeping company he could predict astonishingly precise relations between color and temperature. The first multiplier in this case was radiation’s frequency, symbolized by the Greek letter υ (pronounced nu). For visible light, frequency determines color. Technically, the frequency refers to how many times per second something vibrates. This part of Planck’s formula held no surprises. It was like the IQ part of our imaginary psychology formula. You would expect intelligence to have something to do with creativity. In the same way, physicists expected measures of light and other radiation to include its frequency. After all, many experiments had proven that light is a wave.

The simplest proof of light’s wave nature is to shine colored light, say red light, on two holes to illuminate a screen beyond. If you arrange the holes and screen properly, the red light will include dark lines where no color shines. Light creates these dark lines because the waves coming from the two holes interfere with one another, just as a

room with poor acoustics can have dead spots where sound waves interfere with themselves.

The surprise came in the second part of Planck’s formula because it measured a discrete chunk of action—a “quantum of action,” Planck called it—symbolized by the harmless-seeming symbol h. Planck’s number h never changes and is known as Planck’s constant. Planck multiplied his h by the frequency of radiation to get what he described as “not … a continuous infinitely divisible quantity, but … a discrete quantity composed of an integral number of finite equal parts.” In other words: when you multiply υ and h you do not get something continuous, like a wave, but something discrete, like a particle.

The meaning of hυ—a particle-like something emerging from a wave—astonished Einstein. Material things, like stones, come in chunks. Immaterial things, when they are real enough to have any form at all, come in continuous flows, like time. To see the difference between chunks and continuous things, imagine a slingshot that fires a stone into a swimming pool. The slingshot sends the stone flying. When the stone hits the water, however, ripples spread out in all directions. The stone is a chunk or particle and acts in a chunk-like way. It moves in one direction and arrives in one place. The ripples, meanwhile, behave most unchunkishly and flow in all directions, following one another across the pool like cars on a train. These differences result from the way chunks move as a whole while waves spread when they move. So how does a chunkish hυ emerge from the pure wave υ?

Planck first introduced h as a desperate calculation when no other, more reasonable, energy description worked. He had reached his wits’ end searching for a formula and then found that if he used h the formula worked. So, okay, it worked; use it. But then Einstein used hυ again, this time in what he called light quanta. Again, the formula worked, but it was so aggressively paradoxical and contrary to everything known about light waves that almost no other physicist in the world took it seriously. Since then, however, the paradoxical hυ had turned up again and again. Einstein also used it in a theory about heat, and then a Danish physicist named Niels Bohr used it to analyze the light given off by excited molecules. By the close of 1918 all sorts of basic physics could be measured by using hυ. Especially amazing was

the way these calculations gave very precise answers. If you multiplied a wave’s frequency by Planck’s constant, you got an impressively exact, discrete number that, time after time, matched the experimental data.

Einstein called his hυ a light quantum, making it a definite thing, an indivisible unit of energy. Others, however, even people like Bohr, who used hυ in their own calculations refused to speak of “light quanta.” They denied these were actual energy granules bounding through space. A difference like this can seem subtle to the point of invisibility, but Einstein, who believed that scientific concepts identified real things, and Bohr, who wanted only to describe the outcome of experiments, eventually found themselves in a long, slow-stewing battle that forced everyone interested in the nature of science to pick a side.

Even during a political revolution, Einstein could count on Berliners to leave him alone to ponder what hυ meant. In Zürich, however, he had a wife and children. Einstein found it easy to say No to family. From early on he had played at love with many women, but he seldom became emotionally entangled with any of them. When his emotions did join in, it was usually a sign that physics had become frustrating, and as physics was rarely frustrating for him, emotional involvement was also rare. Einstein had married his wife, Mileva, during the most difficult time of his life, when nobody in Europe was willing to give him a physics job or even take his letters seriously. Years later, after he had been hailed as a giant, he became tormented by the difficulties in revising his theory of relativity, and again his fancy turned toward a woman, his cousin Elsa. That emotion, too, cooled once he gained sure footing in his wrestle with relativity. By then, however, he had settled in Berlin and sent his wife and children marching back to Zürich.

With relativity resolved, Einstein’s attention returned to the quantum. What was radiation and how did it work? Light quanta seemed particularly vexing. It was increasingly clear to Einstein that radiation, at least in its most familiar form, was the emission of light quanta, but light quanta had this puzzling dual nature of wave and particle that made it difficult to say how light behaved. You could perform one set of experiments to show it acted at a specific point, like a particle. A

second set of experiments showed that it moved like a wave. And then there was Einstein’s own genius, always dashing up to the crow’s nest and spotting something new. In 1917, he had written an article on quantum motion in which quanta appeared to move spontaneously, that is, without any of the physical causes that Newton’s laws require. Neither the time nor the direction of such spontaneous actions seemed predictable, except in a statistical way. The whole quantum mystery appeared to lie on wretchedly incomplete ideas.

Most other physicists had more practical worries. Einstein’s question—What is radiation?—was the sort of broad puzzle raised by amateurs and three-year-old children. In 1918 a typical physicist was an experimenter, someone like the young American, Arthur Compton, who was studying X-ray behavior without paying any attention to quantum ideas. Even other theoretical physicists asked narrower questions than did Einstein. Einstein’s good friend Paul Ehrenfest had been among the first to join the quantum investigation, but he was ready to compromise. He wanted “a general point of view,” as he put it, “which may trace the boundary between the ‘classical region’ and the ‘region of the quanta’.” Ehrenfest was willing to accept both classical theory and quantum radiation, despite the contradictions, if only he could know when to use which rule. When it came to physics, contradiction was impossible for Einstein to tolerate.

In his personal life, however, he was more flexible and finally, as 1918 was closing, Einstein dreamt up a way to say Yes to both Berlin and Zürich. He could not possibly say No to Berlin now that it was beaten and ruined. Once Germans were despised by the whole world, they inevitably became more appealing in Einstein’s eyes. He wrote to his friend Lorentz that it was “a priori incredible that the inhabitants of a whole great country should be branded as morally inferior.” To the Swiss as well he said Yes. Unfortunately, he informed them, he could not abandon his duties in Berlin, but because he greatly appreciated the offer and “to show his gratitude to his fellow citizens,” he would, at no charge, be delighted to give a semiannual series of a dozen lectures, starting in early 1919.

Meanwhile, Einstein continued on his own to seek out the law

that underlay the world. Already there were stirrings that law had failed and the new world should be based on something else—pick your instinct: power, heroics, terror, art. Einstein was one of the last of the old knights who was still questing to slay the dragons of anarchy and find the law that lies behind life’s quietest riddle.