Einstein: His Life and Universe, by Walter Isaacson (Simon & Schuster, April, 2007)

In 2005, the world celebrated the centenary of Albert Einstein's “miraculous year.” Within the space of a few months in 1905, an unknown patent clerk with frustrated academic ambitions wrote five papers that would forever transform our understanding of the physical world.

The world into which he was born, in 1879, looked to its inhabitants very different from our own: a world of absolute space and time, built on an uneasy marriage between the deterministic classical mechanics of Newton and the electromagnetic theory of Maxwell. It had not yet experienced the horror of two World Wars, the rise of internationalism and pacifism, the regimes of Hitler and Stalin, or the terrible atomic apotheosis at Hiroshima and Nagasaki.

The story bridging the gulf between that world and our own is in many ways the story of a patent clerk's transformation into the greatest physicist since Newton and the greatest scientific celebrity in history. In telling it, Walter Isaacson also offers the story of our universe as we know it: how it came to be, and where it is going.

When individuals become icons—as Einstein certainly did—we tend to regard them “as sort of a petrified object”, to use Einstein's self-description in his old age. In other words, we forget that they were born, lived, suffered, and died. To most of us, Einstein was always a “beautiful old man walking along the street, the black woolen knit cap firmly planted on his long white hair.” We forget that he was also once a child overwhelmed by the mystery of a compass, once a young man overwhelmed by love. He was once a young Turk anxious for the approval of his elders, thunderously predicting that his doctoral advisor, Alfred Kleiner, “won't dare reject my dissertation, otherwise the short-sighted man is of little use to me” (it was rejected). And he once presented his erstwhile sweetheart Marić with an icy list of “conditions” for their continued cohabitation (“you will stop talking to me if I request it”). As Isaacson writes, “Einstein was human, and thus both good and flawed”. The delight of Isaacson's new biography lies in its dedication to the idea of Einstein as a human being, flaws and all.

Isaacson's prose is sprightly, with a frank informality that would have charmed his subject. Despite its forbidding length, the biography is a quick read. Isaacson's paragraphs fly by at such a speed that readers may experience a bit of relativistic time themselves: a few minutes spent in the company of this great human being correspond to hours in the quotidian world of alarm clocks and 8 a.m. meetings. Although the book is built along roughly chronological lines, the chapters are shaped thematically, jumping among Einstein's life, politics, and science. The thematic focus allows Isaacson to build his case with subtlety and care.

All rumors to the contrary, the young Einstein was actually a rather successful student. Through his family's charity, he befriended a poor medical student named Max Talmud, who introduced the thirteen year old Albert to the delights of Euclidean geometry and the philosophy of Kant. Talmud also gave Einstein a series of books by Aaron Bernstein, in which thought experiments were one of the central tools of explanation.

Kant would in time lead Einstein to the work of Hume and Mach, in which he first confronted “the issue of what can be known about reality”. In his great 1905 discoveries, he would address this question directly, taking from Hume and Mach his empiricism and particularly his skepticism towards absolute space and time. The cognitive habit of thought experiments, too, was foundational.

The delight of Isaacson's new biography lies in its dedication to the idea of Einstein as a human being, flaws and all.

Einstein switched schools at the age of sixteen to avoid the German militarism that was even then emerging as a bothersome counterweight to free-spirited learning. He landed at a school in Aarau, Switzerland, with a rather different approach, one that “began with hands-on observations and then proceeded to intuitions, conceptual thinking, and visual imagery.” The traces of this educational philosophy are obvious in Einstein's adult work. 

In Aarau, Einstein first encountered two forces that would exert a powerful influence on the rest of his life: women and politics. In the same household, Einstein became acquainted both with the “internationalism, pacifism, and democratic socialism” that would be his life-long political creed, and with his political mentor Jost Winteler's charming daughter Marie, whose involvement in Einstein's life would be shorter-lived.

Einstein entered college at the Zurich Polytechnic in 1896. He shied away from the abstractions of pure mathematics in favor of physics courses, where his powerful intuition and visual thinking were more useful. He was an abysmal performer at the laboratory bench, and meanwhile agitated for his teacher, Heinrich Weber, to include the most recent scientific theories in the curriculum—Maxwell's theory of electromagnetism, for example.

With a group of friends he forged ahead, reading the latest papers and cultivating at the same time the bohemian air and casual attitude that evolved into his iconic sockless informality. One of these friends, Marcel Grossman, would later provide crucial mathematical advice when Einstein struggled to formulate general relativity. Another, Michele Besso, would become Einstein's “sounding board” during the development of special relativity, and a collaborator on some of the early versions of the general theory. A third, Mileva Marić, would become Einstein's first wife.

A dark, plain Serbian, prone to depression, Marić was Einstein's classmate at the Polytechnic and hoped to become a professor of physics. Einstein's attraction towards her was complicated, driven in part by his natural, stubborn tendency to contravene convention and in part by her intense intellectualism. Theirs was a passionate relationship, and their letters, which Isaacson quotes extensively, are equal parts the blandishments of young love and the shared enthusiasms of scientific colleagues. Einstein graduated fourth out of five, in part because he had antagonized most of his professors; Marić, however, failed. She would fail her second attempt, a year later, in large measure because she was pregnant out of wedlock with Einstein's child (the fate of this child, Lieserl, is lost to history; she may have been adopted, or may have died at a young age). Einstein's relationship with Marić was extremely unpopular with his family, and Einstein's father only gave his consent on his deathbed, in 1903.

Before he could wed, Einstein needed a job. Conventionally, he would have worked as a professor's assistant. But he was thwarted in his search, and believed (probably correctly) that this difficulty ultimately issued from the pen of his “nemesis” Heinrich Weber. His academic career was off to a most unpromising start. He began publishing papers, generally undistinguished despite his claims to friends about their revolutionary character, and exercised his impudent defiance of authority in squabbles with many of the luminaries of German theoretical physics.

Through the intervention of his friend Grossman he was finally offered a job at the Swiss Patent Office in Bern, in 1902. There he would form another informal philosophical society, the Olympia academy, and begin in earnest the study of Hume and Mach. There he would also make good on his promise to revolutionize physics.

The fact that he spent seven years as a patent clerk—and wrote the paper for which he was awarded the Nobel Prize in that period—is often presented as one of history's great injustices, but Einstein would disagree. He wrote in an autobiographical sketch that the daily examination of patent applications “stimulated me to see the physical ramifications of theoretical concepts.” His superior, Friedrich Haller, “graciously ignored” the fact that Einstein completed his work in two or three hours and spent the rest of his time on physics; further, he insisted that the examiners “think that everything the inventor says is wrong”, encouraging Einstein's native skepticism and willingness to “question every premise, challenge conventional wisdom.” A starting position in the academy would have offered none of these benefits, and Einstein would have likely seen his creativity and independence of thought stifled.

In 1905, Einstein wrote his five famous papers. In the first of these, the only one he himself called “revolutionary”, Einstein proposed that light consisted not of continuous waves, as had been thought since the rejection of Newton's particle theory, but rather of tiny bundles called quanta, with energy proportional to their frequency. Planck had introduced the idea of quanta in his solution to the problem of blackbody radiation, but considered it a mathematical trick, or at best a property of the absorption and emission of light, rather than a property of light itself. In one of history's great ironies, Einstein used the quantum hypothesis to explain the behavior of electrons emitted from certain metals when exposed to light—the photoelectric effect—which had been discovered by Philipp Lenard. Lenard would later become a vicious anti-Semite and one of Einstein's principle enemies.

The fact that he spent seven years as a patent clerk—and wrote the paper for which he was awarded the Nobel Prize in that period—is often presented as one of history's great injustices, but Einstein would disagree.

Less revolutionary in concept were Einstein's next two papers, on the determination of molecular dimensions and on Brownian motion. The former, which finally earned Einstein a doctorate, was the most conventional of the five papers, and applied classical techniques of fluid dynamics and diffusion to calculate Avogadro's number. The latter deployed the statistical physics Einstein loved to explain the jiggling of small particles in a liquid (“Brownian motion”). In essence, the jiggling was caused by the “thermal molecular motions” of the molecules of the liquid; sometimes the motions would cause more liquid molecules to hit one side of the particle, pushing it that direction, and sometimes another, pushing it in a new direction. In total the particle would execute a random walk, and by calculating the statistical properties of that walk, Einstein was able to provide an easy test for the existence of atoms and molecules, which was shortly carried out by an experimentalist.

Although it beggars belief today, scientists of the early twentieth century were unsure about the ontological status of atoms and molecules. These reservations were put to rest largely through the experimental confirmation of Einstein's predictions.

Isaacson hones in on a peculiarity of Einstein's presentation in the Brownian motion paper: the paper starts not with the empirical evidence, but rather with basic physical principles, advanced as postulates. Einstein worked deductively from his postulates to derive results that matched empirical findings.

This peculiarity shines light on Einstein's thinking in his fourth and probably most famous paper, “On the Electrodynamics of Moving Bodies,” in which he advances the theory of special relativity. Einstein had struggled with the reconciliation of Maxwell's electromagnetic theory and the classical principle of relativity—the equivalence of physics in any references frames moving at constant relative velocity—since a thought experiment at the age of 16, when he imagined “rid[ing] at the speed of light alongside a light beam.”

The intuitive result of that thought experiment—that the electromagnetic waves making up the light beam should appear frozen—contradicted Maxwell's theory. Similar worries had plagued many of the world's most prominent physicists, especially since experimental evidence appeared inconsistent with the “luminiferous ether” scientists then believed in. Lorentz had dealt with this apparent contradiction by proposing that physical objects moving relative to the ether contracted in length, rendering the motion relative to the absolute ether frame undetectable.

But this sort of post-hoc solution was anathema to Einstein; it lacked a fundamental simplicity. Instead, he worked by deduction from an intuited “light postulate,” the idea that light always moves at a fixed velocity “regardless of the state of motion of the emitting body.” The consistent elaboration of the light postulate and the principle of relativity led Einstein to reject the notion of absolute simultaneity; as he later wrote, “Two events which, viewed from a system of coordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relative to that system.” But with absolute simultaneity gone, Einstein showed that we must also abandon ideas of absolute space and absolute time, as well as the luminiferous ether—despite the fact that the former had been at the foundation of classical physics since the time of Newton.

Perhaps the simplest illustration of the special theory is the traditional “light clock” example, used by Isaacson in his excellent exposition. Imagine a clock that consists of two mirrors, one at the bottom and one at the top of a box. A single particle of light—a photon—bounces between the mirrors, and every time it makes a complete up-down cycle we count off one unit of time. Because we know the speed of light, and how far apart the two mirrors are, we can figure out what this unit of time is: distance is velocity multiplied by time, so the time for the photon to make the trip from one mirror to the other and back is just twice the distance between the mirrors, divided by the speed of light. This quantity is our unit of time.

Now imagine I take this box and get on the obligatory train, traveling at a high speed. By the relativity principle, my clock works just fine, and I measure the same unit of time. But you, watching from the train platform, observe the following. When the photon leaves the bottom mirror, you see it move diagonally to hit the top mirror, which has moved ahead with the train; likewise, when it bounces back, the bottom mirror has moved ahead, so the photon seems (to you) to take a diagonal path back. You can convince yourself by drawing pictures that the total distance traveled by the photon is larger than twice the distance between the two mirrors. By the light postulate, the speed of light must be the same for both of us. Thus when you compute the unit of time—distance divided by the speed of light—your unit of time will be larger than the one I measure on the train. To you, time on the train seems to be “running slow”.  

Einstein's courage to abandon absolute space and time was informed by the positivism he had learned from Hume and especially Mach; as Einstein wrote in his obituary for Mach, this taught that “Concepts have meaning only if we can point to objects to which they refer and to the rules by which they are assigned to these objects.” On this account, absolute space and time are metaphysical baggage, the luminiferous ether a meaningless heuristic convenience: they cannot be observed, and hence do not really exist.

Einstein extended these results shortly after the appearance of the special relativity paper, yielding the most famous equation in all history: energy equals mass times the speed of light squared.

Although the physics community took its time to recognize his achievements, Einstein had already moved on. In 1907 he had what he would later call “the happiest thought in my life”.

Einstein had been dissatisfied by the limited scope of the special theory of relativity. It only covered cases of relative motion at constant velocity; worse, it left out gravity completely. Like special relativity, the happy realization that gravity and acceleration are completely equivalent—called the “equivalence principle”—appeared through a striking thought experiment: “If a person falls freely, he will not feel his own weight.”

This striking ability to juggle two viewpoints apparently at odds was characteristic of Einstein's thought, and often served as a prelude to the reconciliation of apparently opposed theories.

The elaboration of this insight, and the correct generalization of the relativity principle to accelerated motion, would take eight long years, and would culminate in a theory of gravity and an even more radical revision of our conception of space and time. In the meantime, Einstein would finally assume a professorship at the University of Zurich, in 1909, and thence wander to Prague, to the Zurich Polytechnic, and finally to the University of Berlin, where he was elected the youngest member of the prestigious Prussian Academy, largely due to the efforts of one of his earliest admirers: the great Max Planck. Planck and Einstein shared an abiding interest in the quantum hypothesis, which Planck had tentatively advanced as a calculational convenience and Einstein had grudgingly realized would undermine the entire foundation of classical physics.

In his 1905 papers, Einstein actually used two apparently contradictory interpretations of the nature of light. In the paper on light quanta, Einstein had argued forcefully for the return to Newton's particulate conception of light. Yet in the same year, in his development of special relativity, Einstein had rejected a particulate emission theory of light and had used the traditional Maxwell wave theory. This striking ability to juggle two viewpoints apparently at odds was characteristic of Einstein's thought, and often served as a prelude to the reconciliation of apparently opposed theories. Indeed, in 1909 he advanced the outrageous notion that light could actually be both a wave and a particle—what is now called “wave-particle duality.” This idea, and the consequent disruption of classical notions of determinism and certainty, filled Einstein with a palpable undercurrent of anxiety, and he would struggle for the rest of his life to interpret or unify away the consequences of the theory he and Planck had unleashed.

As Einstein struggled towards a general theory of relativity, embracing both accelerated motion and gravitation, his relationship with Marić fell apart. Einstein took up with his cousin Elsa in 1911, and in the seven years that transpired before he and Marić divorced, they used their friends and two sons, Hans Albert and Eduard, as pawns in a long and bitter struggle. Einstein sought refuge in his scientific labors, and from 1911 to 1915 he would work with heroic focus on the problem of generalizing relativity.

In one of the book's most gripping sections, Isaacson describes the race to solve this problem, which pitted Einstein against the mathematician David Hilbert: their cagey sparring to assert priority, and Einstein's heroic completion of the theory in the course of four Thursday lectures to the Prussian Academy. By the third lecture, Einstein successfully calculated the bending of light by a gravitational field and the explained a long-standing peculiarity in the orbit of Mercury, despite having not quite finished the theory. In the fourth lecture, on November 25, 1915, Einstein presented the final set of gravitational field equations, and his long quest to generalize the relativity principle was complete.

Although mathematically much more complicated than the special theory, general relativity has a similarly intuitive character; as the great Princeton physicist John Wheeler puts it, “Matter tells spacetime how to curve and curved space tells matter how to move”. In other words, the essence of general relativity is that gravity is geometry—the geometry of space-time. Despite having single-handedly revised our conception of space, time, and gravity, Einstein only partly appreciated the consequences of his theory.

One of the many oddities predicted by the theory was the black hole, a singularity in the curvature of space-time from which nothing, not even light, could escape. Einstein resisted this implication from its initial proposal by Schwarzschild in 1916 until its dramatic confirmation by Oppenheimer and Snyder in 1939. Similarly, Einstein beautifully teased out the cosmological implications of general relativity in a 1917 paper, in which he proposed a curved universe that is “finite and yet has no limits”, much like the universe experienced by creatures living on the surface of a sphere. Yet when his field equations showed that the universe must either expand or contract, Einstein balked at overturning the static picture of the universe that prevailed at the time, adding instead the infamous “cosmological constant”, a hypothetical repulsive force able to prevent the universe from collapsing and keep it in stasis.

The static universe would be dramatically overthrown in the 1920's by Edwin Hubble, who showed that the universe was in fact expanding, and Einstein would label the cosmological constant his “greatest blunder.” The cosmological constant has since resurfaced as the mysterious “dark energy” pressed into service to explain the universe’s apparently accelerating expansion—leaving contemporary scientists to hope that Einstein's greatest blunder was right after all. Einstein's discovery of general relativity remains one of the pinnacles of human achievement; yet there is a certain irony in the fact that even Einstein, the great iconoclast, lacked the temerity to follow his postulates through to the very end and predict the expanding universe—probably the only achievement that could have exceeded his own 1905 and 1915 triumphs.

After Einstein had completed his struggle with the general theory, the struggles in his personal life and in the world around him came to the fore. Einstein finally bought his freedom from Marić by offering her the prize money from the Nobel he correctly assumed he would soon be awarded. Despite his initial reluctance, he married his cousin Elsa shortly after the divorce was complete, in June 1919. Elsa was utterly unlike Marić; she was conventional, quite attractive, and wanted nothing more than to settle down with Einstein in a bourgeois household, as befit a scientist of Einstein's stature. As Isaacson rightly puts it, “the marriage was...a solid symbiosis”; unlike Marić, who had sought scientific partnership with Einstein, Elsa saw that grasping her husband's science “is not necessary for my happiness”. She was to serve as Einstein's “translator as well as manager”; in her own words, she was “not talented in any direction except perhaps as wife and mother” (Einstein, Isaacson wryly observes, “required both”).

Despite having single-handedly revised our conception of space, time, and gravity, Einstein only partly appreciated the consequences of his theory.

With the end of World War in 1918, Einstein also for the first time confronted the tension between his socialist sympathies and his “liberal, anti-authoritarian” sentiment. Einstein had strongly opposed the war—and his colleagues' “pro-war mentality”—writing a 1915 manifesto criticizing the nationalist, patriotic impulse. He posited “a biologically determined feature of the male character” that predisposed men to war and proposed “a world organization that had the power to police member nations” as the only solution to the unavoidable problem of militarism. Yet Einstein was equally appalled by the leftist student revolutionaries who took over the University of Berlin in 1918. Einstein, Max Born, and a third friend confronted the revolutionaries, demanding the freedom of the deans and rector whom they had jailed. Einstein sharply criticized the new statutes put in place by the revolutionaries, which he complained “abolish...the old freedom” that was essential to the life of the university. This dedication to intellectual freedom and individualism would remain a nuance in all of Einstein's political positions—positions that would shortly increase enormously in importance.

In 1919, the British astronomer Arthur Eddington finally tested Einstein's prediction that the sun's gravitational field would deflect the apparent position of nearby stars during an eclipse by 1.7 arc-seconds. Although the observations were somewhat ambiguous, Eddington (correctly, it would turn out) discarded the observations that conformed to the older Newtonian predictions and declared Einstein's theory dramatically confirmed.

Einstein was instantly catapulted to fame the likes of which no scientist had ever seen. Isaacson speculates that the world was “yearning for a triumph of human transcendence”—and “an announcement that the theory of a German Jew had been proven correct by an English Quaker” was exactly the balm that the world craved. With evident delight, Isaacson reproduces many of the newspaper headlines announcing the discovery; perhaps the most hilariously over-the-top is this one, from the New York Times: “Men of Science More or Less Agog over Results of Eclipse Observations.” Einstein was torn in his response to sudden celebrity; he was “attracted and repelled by the cameras, loved publicity and loved to complain about it”. But as Isaacson observes, he “could, and would, play the role” required. He had an instinctive ability to generate memorable sound-bites, and would often respond to some ceremony held in his honor by playing his violin.

V.

Einstein's friends cautioned him that his growing fame might provoke the anti-Semitic sentiments that had been brewing in Germany in the aftermath of the first World War. He would, they feared, be portrayed as a “self-promoting Jew”. But unlike many German Jews, who responded to the tide of anti-Semitism by stepping up their effort to assimilate, Einstein was driven to a new-found identification with his “kindred brethren”. As in his science, Einstein had to negotiate a tension between two competing ideals: his fervent anti-nationalism, and his support for the Zionist cause. Einstein's personal experience of anti-Semitism seemed to tip the balance and resolve the tension. In 1920, after attending a meeting of anti-relativists who had denounced the “Jewish nature” of the theory and then criticized Einstein for his “businesslike booming of his theory and name,” Einstein blasted the organizers of the meeting, as well as their colleague Philipp Lenard, in a front-page article, correctly decoding the anti-Semitism veiled in such adjectives as “businesslike”. By 1921 a then-unknown Adolf Hitler was observing that “Science, once our greatest pride, is today being taught by Hebrews.”

Einstein then accepted an invitation from Chaim Weizmann to embark on a joint fund-raising tour through the United States. Isaacson calls Einstein's transformation “a leap not of faith but of commitment”; the great scientist, for whom personal commitment had always been so difficult, was prepared to do “whatever I can for the brothers of my race who are treated so badly everywhere.”

Einstein finally bought his freedom from Maric by offering her the prize money from the Nobel he correctly assumed he would soon be awarded.

The two-month tour was literally incredible. Einstein was often greeted by crowds numbering in the tens of thousands. The theory of relativity was actually debated in the Senate, and Representative J.J. Kindred pushed for “placing an explanation of Einstein's theories in the Congressional Record.” Why? “It may bear upon the legislation of the future as to general relations with the cosmos”. Einstein met President Warren Harding, who was forced to admit he found the theory of relativity baffling.

Although the tour failed to meet Weizmann's fundraising goals, it succeeded in cementing Einstein's “visceral” identification with the Jewish people; it also marked him as “a citizen of the world, an internationalist, not a German”. Einstein's discomfort with his German citizenship would increase in 1922, when Jewish foreign minister Walther Rathenau was assassinated. As an extremely prominent Jew, Einstein was considered a likely target, and described himself as “always on the alert.” He felt little hesitation on leaving for a six month world tour to Asia and Palestine in October 1922—even though he had been advised by Svante Arrehnius that “It will probably be very desirable for you to come to Stockholm in December”. Arrenhius was the head of the physics committee of the Nobel Prize, and the subtext was clear: Einstein would at last receive the award he had promised Mileva Marić in 1917.

VI.

It is not widely known that Einstein actually won the Nobel Prize not for the special or general theory of relativity, but for his work on the photoelectric effect. Each of these three papers was worthy of a Nobel. But the ridiculous politics of the Nobel committee assured that Einstein would not be awarded the Nobel for relativity—and almost prevented his receiving the award at all. In 1920, with the 1919 eclipse observations dramatically confirming the general theory of relativity, Einstein had been nominated by some of the greatest physicists in Europe. But the committee was unmoved; in fact, it was persuaded in part by the arguments of Einstein's anti-Semitic anti-relativist opponents, including Philipp Lenard. In 1921, Einstein was again nominated (“far more than any other contender”), but discomfort with Einstein's growing celebrity caused the committee to award the Nobel to no one rather than to Einstein.

By 1922, it was finally realized that Einstein's “lack of a prize had begun to reflect more negatively on the Nobel than on Einstein” (truly a testament to Einstein's stature, if ever there were one). Isaacson quotes Marcel Brillouin's nominating letter, which observes, “Imagine for a moment what the general opinion will be fifty years from now if the name Einstein does not appear on the list of Nobel laureates.” To resolve the impasse, it was decided to ignore Einstein's work on relativity—in fact, to explicitly note that the Nobel was not given in any way for relativity—and to cite Einstein “for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect” in belatedly awarding him the 1921 Nobel.

And what of Einstein's services to theoretical physics? It is simply not true that Einstein made no further substantial contributions to physics after the discovery and elaboration of the general theory of relativity. Indeed, if his subsequent contributions seem small, it is only in comparison to the enormity of his prior achievements. And no doubt part of this attitude stems from Einstein's overriding quest to extend his general theory to a “Unified Field Theory,” incorporating gravitation and electromagnetism in one grand framework—which would ultimately fail. In fact—rather ironically—the most significant of Einstein's later contributions (stimulated emission—which led to the laser—and Bose-Einstein condensation) applied to the quantum theory that made him so uncomfortable and which he hoped to subsume in the Unified Field Theory.

In the late 1920s, he observed with increasing dismay the advent of quantum mechanics, with its uncertainty principle and its denial of “strict determinism” in favor of a fundamentally probabilistic world-view. Given Einstein's seminal contributions to the quantum revolution, not to mention his youthful sympathy with the positivist philosophy of science that guided the younger generation of quantum physicists, it is natural to wonder how the doggedly anti-establishment Einstein could have transformed into a reactionary defender of the old deterministic universe.

The theory of relativity was actually debated in the Senate: Representative J.J. Kindred pushed for ‘placing an explanation of Einstein's theories in the Congressional Record.’ Why? ‘It may bear upon the legislation of the future as to general relations with the cosmos.’

Paradoxically, it was the success of the general theory of relativity that seems to have guided this transformation. Einstein's philosophy of science had always contained an element of realism; his encounter with the compass at the age of five instilled in him the conviction that “something deeply hidden had to be behind things.” But his working process as a young man had been characterized by a relatively consistent pattern, in which his broad acquaintance with experimental facts guided him to intuit fundamental principles, the consequences of which he would then work out in detail—often closing with a proposed experiment to test the theory.

His positivism came into play chiefly as a negative force; as he wrote to Michele Besso, “It cannot give birth to anything living. It can only exterminate harmful vermin” (e.g. absolute space and time or the ether). This strategy guided him faithfully to the 1905 breakthroughs, and informed his discovery of the equivalence of gravitation and acceleration.

But in order to complete the general theory of relativity, Einstein had ultimately to rely upon mathematical desiderata, and this seems to have elevated a belief in fundamental simplicity and mathematical beauty above all other considerations. He wrote, “When I am judging a theory, I ask myself whether, if I were God, I would have arranged the world in such a way.” This drive to guess the mathematical “secrets of the Old One” informed Einstein's pursuit of the Unified Field Theory; but, crucially, in this case Einstein lacked an overarching physical principle, and came to rely more and more on arguments of mathematical elegance. Such arguments—or rather, intuitions—also informed his skepticism of quantum mechanics, and his conviction that the Old One “does not play dice.”

Einstein turned fifty in 1929. Although he sought to avoid the inevitable storm of publicity, gifts poured in from across the world. One of the most touching—which brought tears to his eyes—was a pouch of tobacco, sent by “an unemployed man [who] had saved a few coins.” His family life had largely settled; he had achieved some measure of reconciliation with Marić, and had even reconciled with his son Hans Albert, who had followed the family pattern by marrying a woman considered most unsuitable by both his parents. His second son, Eduard, had spiraled irretrievably into depression and was institutionalized. Elsa tolerated Einstein's philandering, and selected a “completely discreet, protective, loyal, and [non]-threatening” secretary in Helen Dukas; Dukas would remain Einstein's tireless guardian for the rest of his life (and, later, her own).

‘Imagine for a moment what the general opinion will be fifty years from now if the name Einstein does not appear on the list of Nobel laureates.’

In the years before 1933, when Hitler swept to power on waves of nationalist, anti-Semitic hysteria, Einstein became ever more involved in politics. His pacifism hardened into militancy, and on his second trip to America, in 1930, he argued for “uncompromising war resistance and refusal to do military service under any circumstances”. He sought out the company of Upton Sinclair and Charlie Chaplin, both well-known celebrities of the left, and was repeatedly courted by Soviet and communist front organizations; the latter he consistently rejected, as the Soviet Union violated what Isaacson calls “the most fundamental of all of Einstein's moral principles: Freedom and individualism are necessary for creativity and imagination to flourish.” Einstein's activism was a constant source of consternation for Robert Millikan, the conservative president of Caltech, who had been trying mightily to lure Einstein to join that institution. This tension would be discharged (to Millikan's dismay) when the brilliant educational pioneer Abraham Flexner poached Einstein for his Institute for Advanced Study in Princeton, New Jersey.

The deal concluded with Flexner in June 1932 arrived just in time for Einstein; Hitler became chancellor in January 1933, and Einstein realized that his time in Germany—and his pacifism—had to come to an end. He resigned from the Prussian Academy and gave up his German citizenship (for the second time—he had done so as a youth in Switzerland); he also abandoned his support for war resisters, realizing that the magnitude of the German threat admitted no response “other than organized power”. Isaacson views Einstein's renunciation of pacifism as the pre-eminent example of his scientific approach even to political matters: “For a scientist, altering your doctrines when the facts change is not a sign of weakness”.

Einstein arrived at the Institute for Advanced Study in 1933, and by 1934 had decided to stay. He liked Princeton, which he described as “A quaint and ceremonious village of puny demigods strutting on stiff legs.” He liked America, with its emphasis on individualism and democracy, its “lack of stifling traditions.” And he liked the “modest white clapboard” house at 112 Mercer Street where he settled with Elsa, Helen Dukas, and his step-daughter Margot in 1935.

His time at the Institute generated little in the way of new science, as he continued to grapple with his unified field theory, aided by a string of faithful assistants. His tireless combat with quantum mechanics served, paradoxically, to strengthen the theory: The famous 1935 Einstein-Podolsky-Rosen or EPR paper, aimed to show that quantum mechanics was incomplete, but the experiments inspired by EPR demonstrated conclusively that what Einstein called “spooky action at a distance”—quantum entanglement—was indeed a real feature of the natural world.

While his scientific contributions may have slowed at last to a trickle (despite frequent and breathless newspaper coverage of his latest “successful” unified field theories), at Princeton he generated almost the entirety of the “Einstein legend.” In a process of gradual positive feedback, Einstein settled into the role of “absentminded professor”; indeed, he seemed to play the role self-consciously, noting “I'm a kind of ancient figure known primarily for his non-use of socks and wheeled out on special occasions as a curiosity”. These were the years of helping schoolchildren with their math homework, of surreptitious calls to the Institute asking for directions after he'd “forgotten where my house is.” Elsa died in 1936; Einstein cried publicly for the first time since his mother's death, belying his friend Born's claim that “For all his kindness, sociability, and love of humanity, [Einstein] was nevertheless totally detached from his environment and the human beings in it.” Einstein may have projected the image of living “like a bear in my cave,” but as Isaacson observes, “he was a true loner only in his own mind,” surrounded, in fact, by “a clan wherever he went.”

Any discussion of Einstein's famous equation E = mc² is inevitably framed by the most dramatic illustration of the equivalence of mass and energy: the atomic bomb. Although he would be excluded from the practical design and construction of the first atomic weapons by his lack of relevant expertise and by rather absurd security concerns, Einstein was prompted by Leo Szilard and Edward Teller to write the letter to President Roosevelt that would ultimately launch the Manhattan project. Roosevelt summarized the letter with characteristic flair: “what you are after is to see that the Nazis don't blow us up.”

Like many of the Manhattan Project scientists, Einstein had thought the bomb would be used, if necessary, to defeat the Nazis; after Germany's defeat, he wrote President Roosevelt to beg him not to use it against the Japanese, and was dismayed when the bomb was dropped on Hiroshima and Nagasaki. He was even more disturbed that the bomb would be tied to him in the popular imagination, as in a Time magazine cover “with a portrait showing a mushroom cloud erupting behind him with E = mc² emblazoned on it”. Einstein responded, “Had I known that the Germans would not succeed in producing an atomic bomb, I never would have lifted a finger”.

His broad acquaintance with experimental facts guided him to intuit fundamental principles, the consequences of which he would then work out in detail—often closing with a proposed experiment to test the theory.

More than a month after the dropping of the bomb, Einstein announced that “the only salvation for civilization and the human race lies in the creation of world government.” His final years would be animated by this political quest above all others; in fact, “his passion for advocating a unified governing structure for the globe would rival that for finding a unified field theory that could govern all the forces of nature.” Such activity, and his later opposition to McCarthyism, brought him under the continued and incompetent scrutiny of the FBI, but Einstein was largely oblivious and completely unconcerned. Unlike the Nazi threat, which caused Einstein to abandon his pacifism to resist a menace greater than militarism, the threat of nuclear annihilation confirmed Einstein's commitment to world federalism. In the face of this existential menace, all other dangers—even communist authoritarianism, which he despised—paled in comparison. Einstein famously summarized the danger: “I do not know how the Third World War will be fought, but I can tell you what they will use in the Fourth—rocks”.

Einstein's commitment to broader humanist principles was equaled by his commitment to the American principles of free speech and individual liberty. It was for this reason—and not because of any sympathy with the Soviets—that he opposed McCarthy and urged others to “passive resistance”. When he received a card describing “the American Creed”, which proclaimed that “It is my duty to my country to love it; to support its Constitution; to obey its laws”, Einstein poignantly “wrote on the edge, 'This is precisely what I have done'”. It is both a testament and a rebuke to the American spirit that this immigrant scientist, this recent citizen, understood the principles and freedoms on which our nation makes its foundation better than many whose sworn duty was to protect and uphold them.

Einstein died on Monday, April 18, 1955. His very last actions advanced the three causes that consumed his final years. On April 11, he had put his name to the manifesto drafted with Bertrand Russell, “urg[ing] the governments of the world to realize, and to acknowledge publicly, that their purpose cannot be furthered by a world war...and...to find peaceful means for the settlement of all matters of dispute between them.” On the same day he worked on a speech commemorating the seventh anniversary of the founding of Israel, “one of the few political acts in his lifetime that had a moral quality.” There, too, Einstein's concerns were prescient; he wrote, “The attitude we adopt toward the Arab minority will provide the real test of our moral standards as a people.”

But as he lay dying, he was found not with the draft of a political manifesto, nor editing an address on the Zionist cause, but with “twelve pages of tightly written equations.” The last act of his life was to scratch a few more lines, to strive ever to apprehend the secrets of the Old One. Man of peace, Jewish saint, Einstein was in the end what he had been first, foremost, and always: a man of science.

Isaacson only hints at the most concrete lesson of this remarkable life, which speaks to those who now assume Einstein's mantle and search for the unified theory embracing all of nature. These new theorists, with their talk of strings and twistors, focus on ideas of mathematical elegance and simplicity, much as Einstein did in his quest for the Unified Field Theory. They would do well to remember that Einstein's successes in divining the secrets of the Old One were bookended by a clear physical principle at the beginning and by concrete experimental predictions at the end. At the moment, all but the most dogmatic string theorists would admit that these crucial bookends are missing from their vision of the cosmos; and they recognize that if string theory is to succeed where Einstein failed, the most basic task is to figure out what string theory actually is, to articulate a physical principle as simple as the equivalence of acceleration and gravity.

But to draw such narrow lessons from a life as broad as Einstein's would be to diminish its scope and his significance. Einstein lived through the collapse of determinism in science and in politics. He experienced, and in many cases initiated, paroxysms and revolutions in our picture of the universe and our relations with our fellow men. He was many things to many people: lovestruck youth, upstart physicist, political idealist, simple sage. And his voice speaks to us from Isaacson's pages on issues of blistering contemporary significance.

In an age when the battle-lines between religion and science are drawn with razor-edged clarity, we would do well to remember than Einstein happily occupied the despised middle ground; although he rejected belief in a personal God, he had scant patience for atheists, who lacked, in his words, “a feeling of utter humility towards the unattainable secrets of the harmony of the cosmos.” Surely we can all learn from Einstein's credo, that “Science can be created only by those who are thoroughly imbued with the aspiration towards truth and understanding. This source of feeling, however, springs from the sphere of religion.”  

In a nation where the threat of communism has been replaced by the new existential threat of transnational terrorism, we would be fools not to heed Einstein's words during the McCarthy era. “Every reasonable person must strive to promote moderation and a more objective judgment,” he cautioned, and: “America is incomparably less endangered by its own Communists than by the hysterical hunt for the few Communists that are here.” We can only hope that Isaacson's faith in “how resilient America's democracy and its nurturing of individual liberty could be” is not misplaced.

Isaacson's book is everything a great Einstein biography should be: eminently readable and scientifically literate, full of charming detail and apt quotations. But it is something more. By making Einstein's life quintessentially of the 20^th century, Isaacson deepens the understanding of our own 21^st, and provides us with an example of how to live through the revolutions—scientific, cultural, and political—that we will no doubt confront as the century marches on. From impudent schoolboy to physicist-icon, Einstein remained true to his principles: questioning authority; revering individual freedom; protecting the freedoms of speech and conscience; and striving always to understand the world around us. He wrote: “One of the strongest motives that leads men to art and science is escape from everyday life with its painful crudity and hopeless dreariness. Such men make this cosmos and its construction the pivot of their emotional life, in order to find the peace and security which they cannot find in the narrow whirlpool of personal experience.”

Our world remains one full of painful crudity and hopeless dreariness. But it is also full of hope; full of the possibility of human transcendence. Perhaps this is why Einstein remains so beloved—and so important. Few of us can think as Einstein thought. But we should all strive to live as Einstein lived.

Jacob Foster studied mathematical physics at Balliol College, Oxford, on a Rhodes Scholarship, supervised by Sir Roger Penrose. He is now a PhD student in Complexity Science at the University of Calgary. His current interests range from the mathematical properties of complex networks to the geometry of the Big Bang.