Einstein’s detachment was plain to see when, in 1939, Bohr himself spent two months at Princeton. Once, the two men had been the closest of intellectual companions (“Not often . . . has a human being caused me such joy”), but this time Einstein almost entirely avoided him: not attending Bohr’s talks, not joining Bohr on the long walks the Dane so loved, even avoiding departmental coffees where the one-time friends might meet. When Bohr did go up to Einstein after a seminar, Einstein would speak only in banalities. “Bohr was profoundly unhappy with this,” a participant remembered.
But what choice did Einstein have? They were men of the same generation, yet Bohr was still at the center of world research. Einstein was not. Avoiding Bohr meant Einstein could keep his dignity.
By avoiding Bohr, however, Einstein was also taking one more step into isolation—isolation from developments that might have jump-started his own unified field work if he’d been willing to listen to them. Even more tantalizingly, these developments—had Einstein engaged with them—might have led him to make significant contributions to the hunt for the truth in quantum mechanics. But they passed him by, as he did them.
TWENTY
The End
EINSTEIN TRIED TO MAKE a good life for himself outside his beloved field. He sat for sculptors; he made friends with the saintly theologian Martin Buber (discovering a mutual pleasure in Ellery Queen detective stories); he invited the great singer Marian Anderson to stay at his home whenever she was in Princeton. If he was alone, he would improvise for long stretches on the piano. When his cat Tiger was depressed because it had to stay inside during a rainstorm, Einstein’s secretary recorded him telling the cat, “I know what’s wrong, dear fellow, but I don’t know how to turn it off.”
Elsa died in 1936, and Mileva Marić—whom he hadn’t seen in many years—in 1948, and each loss was a greater blow than he’d expected. Marić’s death was especially tragic. She’d been making a decent life for herself in Zurich, supported by Einstein’s money; tutoring students in the music and mathematics she’d always loved. But their younger son, Eduard, who’d remained in Switzerland, had been diagnosed with schizophrenia as a young adult. He was in and out of institutions; generally peaceful, and content to dreamily play the piano—one of many similarities to his father that family friends remarked on —but he also experienced manic episodes in which he sometimes became violent. In one of those moments, Marić had been with Eduard and, possibly during a struggle, had collapsed. Three months later, she died in the hospital.
Einstein’s sister, Maja, had moved to Princeton just before the war, when her own marriage had fallen apart. (The Winteler family that Einstein had stayed with for his remedial year of high school in Switzerland entered here once again: their daughter Marie had been his first sweetheart, his friend Besso had married another daughter, and Maja had married one of the Winteler sons.) In the hours he spent reading to Maja, Einstein sometimes turned to Don Quixote, but more often to Dostoevsky, whose works they both liked, especially The Brothers Karamazov and its characters’ quest to understand a distant God. Although Ivan, one of the brothers in the book, thought it was impossible to know the Creator (“Such questions are utterly inappropriate for a mind created with an idea of only three dimensions”), Dostoevsky did not, and Einstein was fascinated by the author’s conviction.
When Maja died in 1951, Einstein sat on the back porch of his now empty home for hours on end. “I miss her more than can be imagined,” he told his stepdaughter Margot when she came out to console him. He continued sitting there, in the hot Princeton summer, at one point gesturing to the sky. “Look into nature,” he whispered, almost to himself. “Then you will understand it better.” From special relativity he knew that from some perspectives in the universe, the moment of her death hadn’t yet occurred. But he also knew that those locations were ones he could never access.
AGE WAS PRESSING IN. In 1952 young players from the Juilliard String Quartet came to visit Einstein in his home, playing for him pieces by Beethoven, Bartók, and one of his favorite composers, Mozart. When he was cajoled to join in, he suggested Mozart’s String Quintet in G Minor, and they played together. His hands were stiff and out of practice, but it was a piece he knew well. One of the players remembered, “Einstein hardly referred to the notes on the musical score . . . His coordination, sense of pitch, and concentration were awesome.”
Doubts were creeping in, too—darkness seeping into the corners of the great thinker’s fabled inner vision. At times he was unsure that his efforts with a unified field theory would work. Once, he wrote that he felt as if he were “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.” Another time, he admitted to a favorite mathematics assistant that although he could come up with fresh ideas as well as ever, he sometimes worried that his judgment about which were worth pursuing was fading. More often, though, he would tell others with a shrug that he was convinced that in the future, findings in science would catch up with his theoretical work, just as had often happened in the past. Isaac Newton, after all, had disregarded his own qualms about gravity acting instantaneously, and as a result missed out on the breakthrough that Einstein himself had achieved in 1915. The lambda events had shown Einstein the value of holding out for what he was convinced was right. And now, though quantum theory described certain events accurately, he held out hope that it, too, might be just an intermediate step toward a far greater physics that would be discovered in the future.
Early in 1955, his longest-standing friend, the gentle Michele Besso, died. It had been more than a half century before that Einstein had told Marić, “I like him a great deal because of his sharp mind and his simplicity. I also like Anna, and especially their little kid.” Now that little boy, Vero, was close to sixty himself. Einstein wrote him and Michele’s sister about Michele, explaining how much he had loved and admired him, and adding, “The foundation of our friendship was laid in our student years in Zurich, where we met regularly at musical evenings . . . Later the Patent Office brought us together. The conversations during our mutual way home were of unforgettable charm.” This is when he added the remark we’ve seen before: “Now he has preceded me briefly in his departure from this strange world. This means nothing. For those of us who believe in physics, the distinction between past, present, and future is only an illusion, however tenacious this illusion may be.”
By that time, Einstein was seventy-five years old and ill himself, with one of the large arteries from his heart swelling in an aneurysm that doctors explained was going to burst at some unexpected time. There was the possibility of an operation, but medical science was still poor in this area, and there was no guarantee the procedure—if Einstein even survived it—would cure him.
Rather than risk an operation, Einstein decided to continue with his work on the unified field theory, as well as on public statements warning that unfettered nuclear weaponry could destroy all human life on earth. He tried to be stoic. “To think with fear of the end of one’s life is pretty general with human beings,” he admitted. “. . . The fear is stupid but it cannot be helped.” He was anxious about his condition, and no doubt wondered whether science would justify his isolated labors after all.
In early April 1955, Einstein’s heart condition worsened. His doctors explained that the aneurysm was tearing. The process would be slow at first, then suddenly speed up. There was more talk of an operation, but Einstein was adamant: “It is tasteless to prolong life artificially. I have done my share.” Einstein did ask them what he would experience—how “horrible” the pain would be—but they couldn’t tell him anything for sure. An injection of morphine helped slightly.
By Friday, April 15, he was in such pain that he was driven to Princeton Hospital. When his stepdaughter Margot came, she barely recognized him: pale, his face twisted in pain. Even so, “his personality was the same as ever,” she remembered. “He joked with me . . . and awaited his end as an immine
nt natural phenomenon.” His older son flew in from Berkeley, where he now worked as an engineering professor. Speaking to Hans Albert, Einstein gestured to his equations—which were yet another effort at creating a unified field theory to bring together all known forces in a clear, predictable manner. He said, wryly: “If only I had more mathematics.”
Soon he felt a little better, and even asked for his glasses, as well as a pencil and his papers, to work on those calculations some more. But then in the early morning of Monday, April 18, the aneurysm burst.
He was alone, bleeding to death very quickly. He called out to a nurse, and when she arrived, he whispered to her. But she spoke no German, and so had no idea what the old man said before he died.
Epilogue
ONE DAY AROUND 1904, when Michele Besso’s son, Vero, was young, a friend of his father’s made the boy a splendid kite. The three then walked into the countryside, in the direction of a small mountain south of Bern, taking the kite with them. At the foot of the mountain, one of the adults launched the kite and, once it was airborne, put the string into the boy’s hand.
Vero would remember this family friend clearly in later years, for the man “was always in a good mood, he was amusing and jolly, and above all he knew lots of things.” In particular, Vero never forgot how, on that day, as the kite soared through the air, the man who had made it—Mr. Einstein—could explain to him how it flew.
Einstein was a man of insatiable curiosity and great kindness. Like anyone, he had his faults, and over the course of his life they were magnified by his outsize achievements. But his underlying impulse was pure. If the end of his career was tragic, it was only because he became locked into mistaken lessons from his past.
He had dreamed of being redeemed by history when it came to quantum mechanics, but the very opposite has taken place. In the 1950s and 1960s, researchers developed ways to test Einstein’s belief that quantum mechanics was just a temporary step to a more certain future theory, one that would dispose of the randomness he loathed and provide a more logical, orderly explanation of how the universe functions. When those tests were carried out in the 1980s, however, they confirmed that Heisenberg, Bohr, and the others had been right: the uncertainty principle is rock solid. The world does not operate in the determinist way Einstein wanted to believe it did. The only thing certain, at least at the atomic and subatomic levels, is a certain degree of randomness.
In time, some of Einstein’s own efforts to disprove quantum theory would be turned against him. Even the paper he coauthored in 1935, showing that quantum mechanics would allow distant particles to be “miraculously” entangled, has only strengthened the now accepted view. Those entangled particles have actually been created and are being used in the first generations of quantum computers being built today, in the twenty-first century.
In a vast range of important fields, however, Einstein’s approach and findings have been so completely accepted that generally they are not even acknowledged as coming from him: they just “are.” Our fundamental understanding of photons, of lasers, of low-temperature physics, and, of course, of relativity stems directly from his papers written in Bern, Zurich, and Berlin. Collectively, these achievements are rivaled only by those of Newton in their impact on our lives and in the way they deepened our understanding of the cosmos.
Although Einstein’s particular approach to finding a unified field theory failed, many researchers in subsequent generations have been inspired by the knowledge that the world’s greatest mind spent so many years on this hunt. Einstein’s fruitless quest is, for example, what helped inspire physicist Steven Weinberg and others in their successful work unifying electromagnetism with the weak force that operates inside the atom, an achievement for which they were awarded the Nobel Prize.
With general relativity, which has been symbolized as G=T in this book, Einstein’s work is linked to some of the most stunning discoveries of modern times. His insights about gravitational lensing do show that when we look at distant clusters of galaxies, we should be able to see at least something of what’s behind them. That swerving of light is just what Eddington measured in his 1919 photographs of light bending near the sun.
The more mass there is in those clusters, the more the space around them will bend, and the more powerful that distant lens will be. This today helps to allow us to estimate how much mass there is in such galactic clusters—in informal words, to “weigh” them. The results have been startling, and this has helped show that what we thought filled the universe—stars and planets and the like—is only a small part of the full mass those clusters contain. Most of what exists in the universe is entirely invisible to us, and what it is composed of we do not know. This unseen “stuff” that Einstein’s work allowed us to discover is called dark matter and is a major topic of research.
Not everything about G=T has worked out so neatly, however. When it comes to the lambda, the greatest of ironies has arisen. Einstein had been reluctant to put that extra term into his great 1915 equation, despite its effectiveness in providing a repulsion that pushed outward against gravity. He was delighted when Hubble and Humason in 1929 seemed to show that the universe was expanding at a steady rate, and so no such lambda term was needed. But starting in the 1990s, new findings began to suggest that, inadvertently, Einstein might have been right after all when he brought in the lambda. The universe is not only spreading outward, but something is propelling it apart at an ever faster rate. That enormous force of repulsion has been labeled dark energy and is exactly what a revised lambda term could account for. If this holds up, it would mean that to some extent, what Einstein had felt as his mistake wasn’t, in fact, an error—and all the stubbornness that came from it was unnecessary. Research on a new, revamped cosmological constant is now of great interest, because of its implications for Einstein’s work and its connection to burgeoning new subfields of physics.
These are humbling findings. Everything we see and thought we knew—all the continents and oceans on earth; all the planets and stars beyond—makes up only a very small part of the universe. Dark matter makes up perhaps 25 percent of all there is; dark energy perhaps 70 percent. The entire world we know is but a small, 5 percent fragment, surfing on an unseen immensity. The dark energy component is what necessitates a lambda term after all, modifying Einstein’s great 1915 work. The dark matter is different, and to a great extent can be seen as just another bit of “mass” to plug into his otherwise still valid equations.
Einstein himself pondered how much of the universe’s vastness can be perceived by the human mind. In 1914 he had written to his friend Heinrich Zangger, “Nature is only showing us the tail of the lion. But I have no doubt that the lion belongs to it, even though, because of its colossal size, it cannot directly reveal itself to the beholder.” The underlying truth is hard to perceive. But perhaps one day another genius like Einstein—avoiding the mistake of hubris this time—will show us the behemoth itself.
Acknowledgments
WRITING THE FIRST draft of this book, I felt as if the Muses were dictating the story, but my friends—a cynical lot—thought that if the Muses were providing dictation, it was curious that they included so many clumsy phrases and dull repeated repetitions that had to be fixed, and Shanda Bahles, Richard Cohen, Tim Harford, Richard Pelletier, Gabrielle Walker, Patrick Walsh, and Andrew Wright jumped in with somewhat disturbing eagerness to get that done.
While they were savaging gently improving the manuscript, Michael Hirschl prepared deft illustrations for the main text, and Mark Noad did the same for the online appendix. At one moment, when a large chunk of edited text disappeared into the ether, Carrie Plitt most wonderfully managed to re-create it; Yuri from the Regent Street Apple Store in London helped when the ether called again. Arthur Miller and James Scargill saved me from a number of errors (though neither is responsible for any errors I may have subsequently added). In New York, Alexander Littlefield read the entire manuscript and as deadlines neared made a tremendous number o
f improvements with a calmness that was inspiring to behold. After that, the rest of his team joined in, and it was a pleasure to receive their help: Beth Burleigh Fuller, Naomi Gibbs, Lori Glazer, Martha Kennedy, Stephanie Kim, Ayesha Mirza, and—in distant New Hampshire—Barbara Jatkola, who copyedited the whole thing. In London, Tim Whiting provided excellent counsel and support, and thanks are also due to Iain Hunt, Linda Silverman, Jack Smyth, and Poppy Stimpson.
A generation of Oxford students helped in my initial thoughts on this project by sitting through the Intellectual Tool-Kit lectures in which I first tried out several of the ideas presented here. Going back to the mid-1970s, I had the honor of studying under Chandrasekhar, who worked with many of the principals in this story. (He was the young guest sitting with Rutherford and Eddington at the start of interlude 2.) From the late 1970s, I fondly remember a long afternoon with Louis de Broglie in Paris, his memory of the days when quantum mechanics was being created still utterly clear.
None of that would have led to this book, if it had not been for the remarkable fact that after many years of being a single dad I met Claire. When I proposed marriage —after waiting an interminable eight days from when we first met —she put one finger to my lips, and then whispered: Of course. I had no idea life could offer this.
I’d been too daunted to attempt this book before, but with the confidence that gave me I was able to move forward. Once I began, Mark Hurst deftly showed me how to focus the story, while Floyd Woodrow, the most inspiring of men, showed me how to remain focused.
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