Einstein's Greatest Mistake

by David Bodanis

  Ordinary residents in the New Jersey town were more pleasant. When the great black American singer Marian Anderson was refused entry at a local inn, Einstein invited her to stay at his house and found that instead of being ostracized, a number of his neighbors quietly supported him. They liked this pleasant European in their midst. Indeed, on his very first day in Princeton, Einstein entered an ice cream shop and, knowing his barely understandable English would not get him far, had jabbed one thumb toward a student with an intriguing carrying device for the ice cream, then pointed to himself. The waitress who served him his first vanilla ice cream cone later told reporters it was one of the highlights of her life. The fact that Einstein then strolled outside and bought a newspaper describing the way American journalists were hunting for news of his whereabouts (he’d been brought by tugboat directly from his ocean steamer to a pier in Manhattan, then whisked to Princeton to avoid publicity at the main Manhattan docks) simply added to his charm.

  As time went on, he tutored neighborhood children in mathematics; at Christmas he went outside to play his violin with carolers; he bought a boat for holidays—a small seventeen-footer that he solemnly named the Tinnef (Yiddish for “piece of junk”) and in it again he’d drift, content, for hours. He and Elsa were still not quite in love but made a decent shared life in this land of the flying snakes. When she experienced eye and then kidney problems, she wrote to a friend, “He has been so upset by my illness . . . I never thought he loved me so much. And that comforts me.”

  The material comforts were pleasant, too, as even in Berlin the Einsteins had not had an electric refrigerator. Here seemingly everyone had one. It was also—a great joy—easy to heat water for the bubble bath he liked in the morning. And with rural New Jersey all around them, the price of the two sunny-side-up eggs he preferred for breakfast was exceptionally reasonable. “I have settled down splendidly here,” Einstein wrote his old friend Max Born. “I hibernate like a bear in its cave, and really feel more at home than ever before in all my varied existence.”

  But Einstein was hibernating in other ways as well. Where once he had walked the delicate line between stubbornness and suppleness, now he was becoming increasingly closed-minded. In his view, of course, there was no alternative. “I still do not believe that the Lord throws dice,” he noted, even after several years in America. “Because if he had wanted to do that, he would have done it throughout, and not kept to [any] pattern. Gone the whole hog. In [such a] case we wouldn’t have to look for laws at all.”

  His friends back in Europe begged him to reconsider his position. Every new discovery was backing the subatomic interpretations of Heisenberg and Born; there was absolutely no evidence on his side. The research indicated that scientists could study the world in ever finer detail, but there wouldn’t be any certainty, guarantees, or determinism at its very core. Instead, there would be an intrinsic blur, an uncertainty—actions that seemed impossible from our large-scale perspective.

  Einstein insisted those findings were just temporary and one day would inevitably be overturned. Yet in closing himself off from all that supporting data—which he found so repugnant to his view; which he felt the whole lambda interlude justified him in ignoring—Einstein also was closing himself off from the intellectual connection he still sought. For although much of the Princeton faculty was merely pompous, there were several researchers with whom he might have done serious work, much as Bohr was doing in Copenhagen.

  Just blocks away from Einstein’s Institute for Advanced Study, for example, in Princeton’s main physics department, work was taking place on what would later be called quantum tunneling. Place an electron in front of a wall, and according to traditional physics, the electron might wobble around a bit, but otherwise would pretty much have to stay in its place. With the insights codified in Heisenberg’s uncertainty principle, however, measuring the electron’s velocity requires it to have an indeterminate location, since any measure taken of an electron’s speed prevents an accurate reading of its location. What this means is that although there’s still a chance the electron might stay in front of the wall, there’s also a chance that when you next look, it will appear on the far side of the wall without ever passing through it on the way.

  Were such quantum effects to be noticeable on our usual, large scale of existence, everyone would be able to walk through walls, be they brick or metal or stone. Thin steel walls would be easy to traverse, the walls of King’s Cross train station in London would be a bit harder, and teleporting across the Matterhorn by running into its side would be left only to the most adventurous. None of that would be a matter of just pushing through the barrier in question. Rather, if the rules of quantum tunneling applied at this scale, first you’d be on one side of the thing, and then, instantly, you would appear on the other side.

  By Einstein’s intuition, this was impossible. Yet according to the data accumulated by researchers following Heisenberg, Bohr, and Born, it was what did happen in our real world. The men in the physics department at Princeton who were sharing this work worshipped Einstein and would have relished the chance to collaborate with him. Their studies ultimately helped lead to the creation of the transistors that today operate inside all our phones and electronic devices. But Einstein couldn’t bring himself to grapple with these strange consequences of the new quantum mechanics. Quantum tunneling—and the transistor revolution—advanced without him.

  EINSTEIN’S PERSONAL HISTORY had made him predisposed to discover relativity, but not to accept uncertainty. And now, like so many famous individuals—feted, financially free, his oldest friends far away—there was no force pushing on him to make him reconsider.

  Instead, now in his fifties, Einstein began to concentrate more and more on what he termed his unified field theory. The great Victorian scientists had managed to bring much of what was known about energy in the universe together, fusing that knowledge in the concept of the conservation of energy, which held that all energy—whether produced in a gas explosion or a slamming car door—was connected and could not be created or destroyed, but rather only transformed. In 1905, with E=mc2, Einstein had taken that idea further, showing that not just all forms of energy but also all forms of mass were interlinked. In 1915, with G=T, he had shown that the very geometry of space was interlinked with the mass and energy held within all “things” as well.

  Einstein had advanced the field of physics more than anyone in living memory. But what if he could go further and show that electricity itself was just another aspect of gravity and geometry? That truly would be an achievement for the ages and help show his critics that clear, causal links could be found between an even greater range of phenomena.

  Such, at least, was his aim behind unified field theory, though here again his stubbornness worked against him.

  When Einstein had been an undergraduate in Zurich, his professor Heinrich Weber had said, “You are a smart boy, Einstein, a very smart boy. But you have one great fault: you do not let yourself be told anything.” Far from a great fault, at the time Einstein’s bullheadedness was a strength, for Weber was locked in the physics of the mid-1800s, and Einstein needed to revolt against teachers like him in order to achieve greatness. Yet now, as an aging man, what began as a foible—if that—had grown into something more serious.

  By staying away from the latest findings in quantum mechanics, Einstein was also isolating himself from the era’s breakthroughs in recognizing new particles within the atom. For any unified field theory to work, it would have to incorporate those findings; it could not possibly succeed without them. Once, Einstein would have acknowledged this; indeed, he had regularly ended his early papers with a call to judge them according to new experimental evidence. Now, not only did he not call for experiments to test his theories, but, with the unified field theory being so far from what any researchers were engaged in, such a thing was not even possible. He wasn’t responding to new research results; he wasn’t proposing new, detailed experiments. His dream of
a unified theory was proving impossible to carry out.

  Einstein’s insistence on his own path wasn’t heroic self-belief anymore; it really was unreasonable stubbornness. Yet with his dogged determination, he kept at it, month after month, for almost twenty years.

  His efforts were made more meaningless by the fact that working so much on his own now—or just with bright but utterly subservient graduate assistants—Einstein was also isolating himself from fresh analytic tools. A young visitor to his upstairs study saw that his work surfaces were full of papers still using the notation that had been so useful when Grossmann had taught him about it in the 1910s. By the 1940s and 1950s, physicists were using very different formalisms for their new work in nuclear physics. Yet those old tools had done such wonders for Einstein before that he couldn’t let them go.

  This was a tragedy, for Einstein’s intellect remained exceptionally powerful. Several years into his time at Princeton, when he briefly set aside his work on unified field theory and turned back to pure relativity, he elaborated on a magnificent construct called gravitational lenses, suggesting that entire galaxies could warp everything around them so strongly that light from galaxies even farther behind them—light that should have been forever blocked from our sight—could actually be seen, as the warping “tugged” that light all the way around. The idea was so staggering that it was almost entirely ignored.

  Amidst these other projects, Einstein summoned the energy to mount a final challenge to his bête noire, quantum theory. In 1935, working with two younger colleagues, he tried one more paper to show that the predictions of quantum mechanics couldn’t be true. In the paper, he came up with the concept of what’s now called quantum entanglement. This notes that under the accepted rules of quantum mechanics, if a particle breaks up into, say, two particles that travel very fast and very far—if one ends up at the far side of the solar system or beyond—an experiment on one can cause an immediate change in certain properties that the other possesses.

  In Einstein’s mind, the bizarre notion that distant particles could be instantaneously interconnected demonstrated what was “wrong” with the field Bohr, Heisenberg, and the others had begun: clearly, this outrageous implication of their theory meant that the entire thing was unstable. When this didn’t persuade the new generation of scientists to change their views, he gave up. There was no use arguing. Although he would continue to criticize quantum theory from time to time, he would never mount a concerted campaign against it again.

  EINSTEIN’S OLDER SON, Hans Albert, moved to the United States in 1937. Whatever tension had once existed between them had long since disappeared, and Einstein visited him often in South Carolina, where Hans Albert was working on hydraulic engineering and studying how sediments collect in rivers. They’d stroll in the forests and gossip about Hans Albert’s academic research. Einstein was open-minded about it, and when Hans Albert ended up as a professor at Berkeley, he remembered his father still loving to hear about new inventions and clever mathematical puzzles. But if the topic turned to quantum mechanics, Einstein would close down; his views were entirely set.

  At one point in the mid-1930s, there had been a chance that Einstein’s isolation could end. He’d stayed in touch with the Austrian physicist Erwin Schrödinger, who, although he’d been central to the quantum revolution, remained one of the very few who shared Einstein’s doubts about a probabilistic interpretation of quantum mechanics. The two men also shared a certain bohemian attitude toward life. (“It was bad enough to have one wife at Oxford,” his biographer remarked about Schrödinger’s time guest-lecturing there, “[but] to have two was unspeakable.”) They truly liked each other. “You are my closest brother,” Einstein wrote him, “and your brain runs so similarly to mine.”

  Schrödinger, blessedly, had even followed up Einstein’s 1935 paper on quantum mechanics with a thought experiment that aimed to show how absurd quantum entanglement (a term the Austrian coined) was. Building on ideas shared in letters with Einstein, Schrödinger proposed his famous scenario in which a cat was trapped in a sealed box with a vial of poison that would be released—or not—depending on whether a decaying radioactive substance within the box let out a single particle. There was a fifty-fifty chance that the cat would die, but the only way to know for sure was to open the box. Until one did that, was the cat alive or dead?

  Now known colloquially as “Schrödinger’s Cat experiment,” this case is used today to illustrate the strange-but-true nature of quantum mechanics. At the time, however, it was held to be a critique of the entire system against which Einstein had railed for so long. In true Einstein fashion, Schrödinger had used his imagination to mount a vigorous attack on quantum theory.

  Einstein and Schrödinger were, therefore, predisposed to be partners, and for a time it seemed as if they might have a chance to collaborate more closely. Even though Schrödinger wasn’t Jewish, he’d had a tense relationship with the Nazis and had let everyone in the physics community know that he would be happy to be appointed to a post in Princeton, safely across the Atlantic. Had this happened, Schrödinger and Einstein surely would have teamed up. Einstein’s thinking on quantum mechanics may well have been clarified, though given his personality it’s unlikely that his attitude would have softened as much as Schrödinger’s ultimately did. For although quantum mechanics is far from being entirely random—principles such as the uncertainty principle hold very precisely—it is, at its heart, still far from the determinism that Einstein always insisted had to be true.

  What Einstein and Schrödinger might have achieved together will never be known, however, for the director of the Institute for Advanced Study, Abraham Flexner, had at this point turned against Einstein—though not for anything having to do with quantum mechanics. Flexner paid Einstein handsomely (not for nothing was it also known as the Institute for Advanced Salaries) but had tried too hard to keep his star attraction under control.

  When Einstein had first arrived, Flexner had screened the letters coming to him, and in particular had turned down an invitation for Einstein to visit the White House because he thought it would distract Einstein from his work. For Einstein, that had been infuriating, not just because he hated the idea of being patronized (this was, he wrote in one of his rare curt letters, an “interference . . . that no self-respecting person can tolerate”), but also because the director’s meddling was constraining Einstein’s affairs in one area of particular importance to him.

  Einstein was one of the most active of all émigrés in trying to get refugees away from the growing Nazi power in Europe. He used much of his income to pay for visas for ordinary families; he wrote innumerable letters of recommendation so that ordinary faculty—not just the elite—could get jobs in the United States; he lobbied for changes in policy to allow more of his colleagues to immigrate. The thought that he had been denied a chance to press their case at the highest levels of the U.S. government was intolerable.

  When he found out what Flexner had done, Einstein wrote to the president, Franklin D. Roosevelt, and ended up dining at the White House after all. Roosevelt, like many educated Americans of the time, spoke enough German to carry on a conversation in Einstein’s native tongue. Along with the European situation, they talked about sailing, which both men loved, and the Einsteins spent the night.

  Einstein left the White House having advanced the case of his fellow refugees—but inadvertently having also ruined his last best chance of refurbishing his reputation among his fellow physicists. Flexner was so offended by having his control questioned that—knowing how important Schrödinger could be to Einstein—he blocked any chance of the transfer both scientists so wanted. Schrödinger ended up in Dublin, where he would remain until the end of Einstein’s life.

  Even in the isolation of 1930s Dublin—a relatively poor city in a new country that was fiercely separating itself from the United Kingdom—Schrödinger did what Einstein could not. He effectively admitted that he’d given his best arguments and that Bohr a
nd the others had answers for all of them—and so he would accept that his intuition was wrong. He put his old ideas aside and shifted to fresh explorations of the structure of life—work of such insight that it helped trigger the revolution in DNA research that occurred from the 1940s onward.

  This was exactly the sort of shift to a new field that had inspired Einstein in the past and might have helped him to revive his career now—if only he had been capable of admitting his error, or at least putting the matter fully out of his mind. But he seemed incapable of doing either. Without Schrödinger’s assistance and unable to mount a renewed, more viable offensive against quantum theory, he continued his drift toward the sidelines of science.

  Einstein knew he was being shunned. Although the popular press reported on his work with credulous excitement, working physicists scorned it, as in a remark by the acerbic Wolfgang Pauli, writing from Switzerland: “Einstein has once again come out with a public comment on quantum mechanics . . . As is well known, each time he does that, it is a disaster.” Another physicist at the Princeton institute remembered that word had gone out to the scientists there that “it would be better not to work with Einstein.” The extent of his marginalization became painfully clear when a paper he wrote was turned down by the Physical Review, an American journal that was roughly the equivalent of Germany’s prestigious Zeitschrift für Physik. Einstein was not the sort of man to stand on rank, but this had never happened to him before.

  He pretended the failures and rejections didn’t matter: “I am generally regarded as sort of a petrified object. I find this role not too distasteful, as it corresponds very well with my temperament.” But it was hard to keep up that front entirely, and rather than enduring the humiliation of his own irrelevance, increasingly it seemed that Einstein was simply giving up on the work that others were doing in physics.