Like many Jewish refugees, his feelings had a personal basis. Among those who suffered under the Nazis was his first cousin Roberto, son of Uncle Jakob. When German troops were retreating from Italy near the end of the war, they wantonly killed his wife and two daughters, then burned his home while he hid in the woods. Roberto wrote to Einstein, giving the horrible details, and committed suicide a year later.51
The result was that Einstein’s national and tribal kinship became even more clear in his own mind. “I am not a German but a Jew by nationality,” he declared as the war ended.52
Yet in ways that were subtle yet real, he had become an American as well. After settling in Princeton in 1933, he never once in the remaining twenty-two years of his life left the United States, except for the brief cruise to Bermuda that was necessary to launch his immigration process.
Admittedly, he was a somewhat contrarian citizen. But in that regard he was in the tradition of some venerable strands in the fabric of American character: fiercely protective of individual liberties, often cranky about government interference, distrustful of great concentrations of wealth, and a believer in the idealistic internationalism that gained favor among American intellectuals after both of the great wars of the twentieth century.
His penchant for dissent and nonconformity did not make him a worse American, he felt, but a better one. On the day in 1940 when he was naturalized as a citizen, Einstein had touched on these values in a radio talk. After the war ended, Truman proclaimed a day in honor of all new citizens, and the judge who had naturalized Einstein sent out thousands of form letters inviting anyone he had sworn in to come to a park in Trenton to celebrate. To the judge’s amazement, ten thousand people showed up. Even more amazing, Einstein and his household decided to come down for the festivities. During the ceremony, he sat smiling and waving, with a young girl sitting on his lap, happy to be a small part of “I Am an American” Day.53
CHAPTER TWENTY-THREE
LANDMARK
1948–1953
With Israeli Prime Minister David Ben-Gurion in Princeton, 1951
The Endless Quest
The problems of the world were important to Einstein, but the problems of the cosmos helped him to keep earthly matters in perspective. Even though he was producing little of scientific significance, physics rather than politics would remain his defining endeavor until the day he died. One morning when walking to work with his scientific assistant and fellow arms control advocate Ernst Straus, Einstein mused at their ability to divide their time between the two realms. “But our equations are much more important to me,” Einstein added. “Politics is for the present, while our equations are for eternity.”1
Einstein had officially retired from the Institute for Advanced Study at the end of the war, when he turned 66. But he continued to work in a small office there every day, and he was still able to enlist the aid of loyal assistants willing to pursue what had come to be considered his quaint quest for a unified field theory.
Each weekday, he would wake at a civilized hour, eat breakfast and read the papers, and then around ten walk slowly up Mercer Street to the Institute, trailing stories both real and apocryphal. His colleague Abraham Pais recalled “one occasion when a car hit a tree after the driver suddenly recognized the face of the beautiful old man walking along the street, the black woolen knit cap firmly planted on his long white hair.”2
Soon after the war ended, J. Robert Oppenheimer came from Los Alamos to take over as director of the Institute. A brilliant, chain-smoking theoretical physicist, he proved charismatic and competent enough to be an inspiring leader for the scientists who built the atomic bomb. With his charm and biting wit, he tended to produce either acolytes or enemies, but Einstein fell into neither category. He and Oppenheimer viewed each other with a mixture of amusement and respect, which allowed them to develop a cordial though not close relationship.3
When Oppenheimer first visited the Institute in 1935, he called it a “madhouse” with “solipsistic luminaries shining in separate and hapless desolation.” As for the greatest of these luminaries, Oppenheimer declared, “Einstein is completely cuckoo,” though he seemed to mean it in an affectionate way.4
Once they became colleagues, Oppenheimer became more adroit at dealing with his luminous charges and his jabs became more subtle. Einstein, he declared, was “a landmark but not a beacon,” meaning he was admired for his great triumphs but attracted few apostles in his current endeavors, which was true. Years later, he provided another telling description of Einstein: “There was always in him a powerful purity at once childlike and profoundly stubborn.”5
Einstein became a closer friend, and a walking partner, of another iconic figure at the Institute, the intensely introverted Kurt Gödel, a German-speaking mathematical logician from Brno and Vienna. Gödel was famous for his “incompleteness theory,” a pair of logical proofs that purport to show that any useful mathematical system will have some propositions that cannot be proven true or false based on the postulates of that system.
Out of the supercharged German-speaking intellectual world, in which physics and mathematics and philosophy intertwined, three jarring theories of the twentieth century emerged: Einstein’s relativity, Heisenberg’s uncertainty, and Gödel’s incompleteness. The surface similarity of the three words, all of which conjure up a cosmos that is tentative and subjective, oversimplifies the theories and the connections between them. Nevertheless, they all seemed to have philosophical resonance, and this became the topic of discussion when Gödel and Einstein walked to work together.6
They were very different personalities. Einstein was filled with good humor and sagacity, both qualities lacking in Gödel, whose intense logic sometimes overwhelmed common sense. This was on glorious display when Gödel decided to become a U.S. citizen in 1947. He took his preparation for the exam very seriously, studied the Constitution carefully, and (as might be expected by the formulator of the incompleteness theory) found what he believed was a logical flaw. There was an internal inconsistency, he insisted, that could allow the entire government to degenerate into tyranny.
Concerned, Einstein decided to accompany—or chaperone—Gödel on his visit to Trenton to take the citizenship test, which was to be administered by the same judge who had done so for Einstein. On the drive, he and a third friend tried to distract Gödel and dissuade him from mentioning this perceived flaw, but to no avail. When the judge asked him about the Constitution, Gödel launched into his proof that its internal inconsistency made a dictatorship possible. Fortunately, the judge, who by now cherished his connection to Einstein, cut Gödel off. “You needn’t go into all that,” he said, and Gödel’s citizenship was saved.7
During their walks, Gödel explored some of the implications of relativity theory, and he came up with an analysis that called into question whether time, rather than merely being relative, could be said to exist at all. Einstein’s equations, he figured, could describe a universe that was rotating rather than (or in addition to) expanding. In such a case, the relationship between space and time could become, mathematically, mixed up. “The existence of an objective lapse of time,” he wrote, “means that reality consists of an infinity of layers of ‘now’ which come into existence successively. But if simultaneity is something relative, each observer has his own set of ‘nows,’ and none of these various layers can claim the prerogative of representing the objective lapse of time.”8
As a result, Gödel argued, time travel would be possible. “By making a round trip on a rocket ship in a sufficiently wide curve, it is possible in these worlds to travel into any region of the past, present and future, and back again.” That would be absurd, he noted, because then we could go back and chat with a younger version of ourselves (or, even more discomforting, our older version could come back and chat with us). “Gödel had achieved an amazing demonstration that time travel, strictly understood, was consistent with the theory of relativity,” writes Boston University philosophy professor Palle
Yourgrau in his book on Gödel’s relationship with Einstein, World Without Time. “The primary result was a powerful argument that if time travel is possible, time itself is not.”9
Einstein responded to Gödel’s essay along with a variety of others that had been collected in a book, and he seemed to be mildly impressed but also not totally engaged by the argument. In his brief assessment, Einstein called Gödel’s “an important contribution” but noted that he had thought of the issue long ago and “the problem here involved disturbed me already.” He implied that although time travel may be true as a mathematical conceivability, it might not be possible in reality.“It will be interesting to weigh whether these are not to be excluded on physical grounds,” Einstein concluded.10
For his part, Einstein remained focused on his own white whale, which he pursued not with the demonic drive of Ahab but the dutiful serenity of Ishmael. In his quest for a unified field theory, he still had no compelling physical insight—such as the equivalence of gravity and acceleration, or the relativity of simultaneity—to guide his way, so his endeavors remained a groping through clouds of abstract mathematical equations with no ground lights to orient him. “It’s like being in an airship in which one can cruise around in the clouds but cannot see clearly how one can return to reality, i.e., earth,” he lamented to a friend.11
His goal, as it had been for decades, was to come up with a theory that encompassed both the electromagnetic and the gravitational fields, but he had no compelling reason to believe that they in fact had to be part of the same unified structure, other than his intuition that nature liked the beauty of simplicity.
Likewise, he was still hoping to explain the existence of particles in terms of a field theory by finding permissible pointlike solutions to his field equations. “He argued that if one believed wholeheartedly in the basic idea of a field theory, matter should enter not as an interloper but as an honest part of the field itself,” recalled one of his Princeton collaborators, Banesh Hoffmann. “Indeed, one might say that he wanted to build matter out of nothing but convolutions of spacetime.” In the process he used all sorts of mathematical devices, but constantly searched for others. “I need more mathematics,” he lamented at one point to Hoffmann.12
Why did he persist? Deep inside, such disjunctures and dualities—different field theories for gravity and electromagnetism, distinctions between particles and fields—had always discomforted him. Simplicity and unity, he intuitively believed, were hallmarks of the Old One’s handiwork. “A theory is more impressive the greater the simplicity of its premises, the more different things it relates, and the more expanded its area of applicability,” he wrote.13
In the early 1940s, Einstein returned for a while to the five-dimensional mathematical approach that he had adopted from Theodor Kaluza two decades earlier. He even worked on it with Wolfgang Pauli, the quantum mechanics pioneer, who had spent some of the war years in Princeton. But he could not get his equations to describe particles.14
So he moved on to a strategy dubbed “bivector fields.” Einstein seemed to be getting a little desperate. This new approach, he admitted, might require surrendering the principle of locality that he had sanctified in some of his thought-experiments assaulting quantum mechanics.15 In any event, it was soon abandoned as well.
Einstein’s final strategy, which he pursued for the final decade of his life, was a resurrection of one he had tried during the 1920s. It used a Riemannian metric that was not assumed to be symmetric, which opened the way for sixteen quantities. Ten combinations of them were used for gravity, and the remaining ones for electromagnetism.
Einstein sent early versions of this work to his old comrade Schrödinger. “I am sending them to nobody else, because you are the only person known to me who is not wearing blinders in regard to the fundamental questions in our science,” Einstein wrote. “The attempt depends on an idea that at first seems antiquated and unprofitable, the introduction of a non-symmetrical tensor ... Pauli stuck his tongue out at me when I told him about it.”16
Schrödinger spent three days poring over Einstein’s work and wrote back to say how impressed he was. “You are after big game,” he said.
Einstein was thrilled with such support. “This correspondence gives me great joy,” he replied, “because you are my closest brother and your brain runs so similarly to mine.” But he soon began to realize that the gossamer theories he was spinning were mathematically elegant but never seemed to relate to anything physical. “Inwardly I am not so certain as I previously asserted,” he confessed to Schrödinger a few months later. “We have squandered a lot of time on this, and the result looks like a gift from the devil’s grandmother.”17
And yet he soldiered on, churning out papers and producing the occasional headline. When a new edition of his book, The Meaning of Relativity, was being prepared in 1949, he added the latest version of the paper he had shown Schrödinger as an appendix. The New York Times reprinted an entire page of complex equations from the manuscript, along with a front-page story headlined “New Einstein Theory Gives a Master Key to Universe: Scientist, after 30 Years’ Work, Evolves Concept That Promises to Bridge Gap between the Star and the Atom.”18
But Einstein soon realized that it still wasn’t right. During the six weeks between when he submitted the chapter and when it went to the printers, he had second thoughts and revised it yet again.
In fact, he continued to revise the theory repeatedly, but to no avail. His growing pessimism was visible in the lamentations he sent to his old friend from the Olympia Academy days, Maurice Solovine, then Einstein’s publisher in Paris. “I shall never ever solve it,” he wrote in 1948. “It will be forgotten and must later be rediscovered again.”Then, the following year: “I am uncertain as to whether I was even on the right track. The current generation sees in me both a heretic and a reactionary who has, so to speak, outlived himself.” And, with some resignation, in 1951: “The unified field theory has been put into retirement. It is so difficult to employ mathematically that I have not been able to verify it. This state of affairs will last for many more years, mainly because physicists have no understanding of logical and philosophical arguments.”19
Einstein’s quest for a unified theory was destined to produce no tangible results that added to the framework of physics. He was able to come up with no great insights or thought experiments, no intuitions about underlying principles, to help him visualize his goal. “No pictures came to our aid,” his collaborator Hoffmann lamented. “It is intensely mathematical, and over the years, with helpers and alone, Einstein surmounted difficulty after difficulty, only to find new ones awaiting him.”20
Perhaps the search was futile. And if it turns out a century from now that there is indeed no unified theory to be found, it will also look misconceived. But Einstein never regretted his dedication to it. When a colleague asked him one day why he was spending—perhaps squandering—his time in this lonely endeavor, he replied that even if the chance of finding a unified theory was small, the attempt was worthy. He had already made his name, he noted. His position was secure, and he could afford to take the risk and expend the time. A younger theorist, however, could not take such a risk, for he might thus sacrifice a promising career. So, Einstein said, it was his duty to do it.21
Einstein’s repeated failures in seeking a unified theory did not soften his skepticism about quantum mechanics. Niels Bohr, his frequent sparring partner, came to the Institute for a stay in 1948 and spent part of his time writing an essay on their debates at the Solvay Conferences before the war.22 Struggling with the article in his office one floor above Einstein’s, he developed writer’s block and called in Abraham Pais to help him. As Bohr paced furiously around an oblong table, Pais coaxed him and took notes.
When he got frustrated, Bohr sometimes would simply sputter the same word over and over. Soon he was doing so with Einstein’s name. He walked to the window and kept muttering, over and over, “Einstein . . . Einstein . . .”
At one such moment, Einstein softly opened the door, tiptoed in, and signaled to Pais not to say anything. He had come to steal a bit of tobacco, which his doctor had ordered him not to buy. Bohr kept muttering, finally spurting out one last loud “Einstein” and then turning around to find himself staring at the cause of his anxieties. “It is an understatement to say that for a moment Bohr was speechless,” Pais recalled. Then, after an instant, they all burst into laughter.23
Another colleague who tried and failed to convert Einstein was John Wheeler, Princeton University’s renowned theoretical physicist. One afternoon he came by Mercer Street to explain a new approach to quantum theory (known as the sum-over-histories approach) that he was developing with his graduate student, Richard Feynman. “I had gone to Einstein with the hope to persuade him of the naturalness of the quantum theory when seen in this new light,” Wheeler recalled. Einstein listened patiently for twenty minutes, but when it was over repeated his very familiar refrain: “I still cannot believe that the good Lord plays dice.”
Wheeler showed his disappointment, and Einstein softened his pronouncement slightly. “Of course, I may be wrong,” he said in a slow and humorous cadence. Pause. “But perhaps I have earned the right to make my mistakes.” Einstein later confided to a woman friend, “I don’t think I’ll live to find out who is correct.”
Wheeler kept coming back, sometimes bringing his students, and Einstein admitted that he found many of his arguments “sensible.” But he was never converted. Near the end of his life, Einstein regaled a small group of Wheeler’s students. When the talk turned to quantum mechanics, he once again tried to poke holes in the idea that our observations can affect and determine realities. “When a mouse observes,” Einstein asked them, “does that change the state of the universe?”24
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