Years later he apparently told a colleague that putting in the lambda was “the greatest blunder of my life.” But about this he was wrong. Einstein made an even greater mistake by then deciding that he could ignore experiments that seemed to disprove what he was convinced was right. He’d made that error in his dealings with Friedmann and Lemaître, but he had made it in other regards, too. Over the years, Einstein had bumped up against other experimental evidence suggesting that the universe was less tidy than he believed. He had never wanted to accept that. Now his experience with the lambda had made him downright obdurate—and less inclined than ever to accept disagreeable findings about how the cosmos actually worked.
Part V
THE GREATEST MISTAKE
Einstein, early 1930s
FIFTEEN
Crushing the Upstart
IN ALL THE YEARS that Einstein had been working on large-scale questions of the universe’s structure, physics had also been making advances in the realm of the ultrasmall, at the level of atoms and electrons. This was happening at the same time that Einstein had conceived of G=T, and later as he adulterated it with the lambda, and still later during the more than ten years he had uncomfortably abided that unwanted term’s existence. An entirely new view was taking shape. It represented as big a jump in our understanding of the world we inhabit as that which the Victorians had created in their physics of the century before, and that which Einstein’s theories of special and general relativity had effected during the twentieth century. This revolution would threaten everything Einstein held to be true, and his response would lead to the scientific isolation that he endured at Princeton.
The old paradigm had been kind to Einstein, and he had grown comfortable with it, even as other physicists were working to overturn it. When Einstein had been young, and even into his twenties and thirties while he was achieving so much with the ideas leading to G=T, thinkers had assumed that whether you looked at large objects or small, it would be possible to find precise laws that explained how they moved. Yet by that point in Einstein’s life, evidence had been emerging to suggest that this was not the case—even if his fellow scientists had a hard time accepting that interpretation at first.
In 1908, for example, when working in Manchester, the bluff New Zealand–born researcher Ernest Rutherford had discovered something that seemed too strange to comprehend. He had fired tiny particles into thin sheets of atoms, and although most flew right through, or got deflected off course by a few degrees, there were a small number of particles that bounced directly back.
“It was quite the most incredible event that has ever happened to me in my life,” he wrote. “It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.”
Rutherford’s discovery challenged all expectations about how subatomic particles would behave—yet the rebound effect he discovered didn’t end the view that everything could be understood with exact and causal certainty. After only a few weeks of confusion, Rutherford worked out that what this really meant was not that there was random chaos inside an atom, but rather that there was something very hard in there. That hard bit at the center of each atom, he realized, could be seen as being like a miniature sun. Flying around it, he imagined, there would be miniature planets. Those were the far lighter electrons. The particles he’d shot into the atoms had mostly passed through the empty space between the miniature “planets,” but occasionally one had hit the tough “sun” at the center—what he came to call the atom’s nucleus—and that’s why they had been deflected back.
This was a comforting and familiar interpretation—the idea that the micro-world operated just like a miniature copy of the macro-world; that we humans lived on a planet in a big solar system, and inside us there were a multitude of smaller “solar systems” making up the atoms of which we were composed. None of this undermined the standard view of how science advanced: that with ever greater analysis and more powerful tools, scientists would continue to see precise activities, however deeply within matter they entered.
Then, in 1912 and 1913, the Danish scientist Niels Bohr worked out even more details about those miniature “solar systems” Rutherford had discovered. While Rutherford looked like one might imagine any stocky New Zealand farmer to look, Bohr resembled no one else. He had a great wide head and unusually big teeth. When he and his brother were toddlers, a passerby apparently once commiserated with his mother on having such clearly abnormal children. Yet he was also an exceptional soccer player. At his Ph.D. ceremony, the faculty at the University of Copenhagen were discomfited when they realized that many of the attendees were simply other soccer players out to support their outstanding teammate. Bohr’s even more skilled brother was a star of the national Olympic squad, and the story goes that when Niels later won the Nobel Prize, one headline in a sporting paper read BROTHER OF SOCCER STAR WINS PHYSICS PRIZE.
Niels Bohr on holiday in Norway, 1933
Bohr mumbled when he spoke, which he did with unusual slowness, but he was the kindest of men, with a profound creative mind, and took delight in friends who shared his ability to take a fresh view of life. When Bohr had begun his work on electron orbits, for example, he had been studying with Ernest Rutherford and staying at a boardinghouse in Manchester. The students living there suspected that their landlady was recycling the Sunday roast, turning it into dishes so many days or weeks later that it was no longer fit to eat. One of the students was a Hungarian, George de Hevesy, who after reflection decided to spike their Sunday leftovers with a radioactive tracer from Rutherford’s lab. A Geiger counter–like device that was smuggled in many days later showed that the young men’s suspicions were true. Bohr and de Hevesy became lifelong friends (and indeed de Hevesy later won the Nobel Prize for his work on radioactive tracers).
In Bohr’s research into the architecture of atoms, many of his early findings seemed too strange to incorporate into the march of rational physics. He realized that electrons couldn’t really operate like the miniature solar systems Rutherford had imagined. If electrons did start out circling the nucleus, they would soon end up tumbling inward, and the atoms would collapse. As, however, we, and our planet, and much of the universe are made up of atoms that haven’t collapsed—as our bodies haven’t shriveled to concentrated particles of dust—something else must be going on to keep the whirring electrons more stably in position.
But this strange aspect of electrons’ orbits was, like Rutherford’s discovery about atomic nuclei, something that could be understood in what were still fairly conventional terms. Bohr came up with the notion that electrons were locked into a fixed range of possible orbits. They couldn’t randomly glide down from a distant position to one closer to the central nucleus. Instead, they were restricted to making tiny hops from one particular orbit to another. It would be as if Neptune could suddenly appear whirling in orbit just beside the earth, or possibly beside Mars or another planet, but it could never appear anywhere else in the solar system. This concept, like Rutherford’s theory, was strange to imagine—but once it was accepted, there was no inherent limit to the detail with which the underlying phenomena could be described. Those hops came to be called quantum jumps (in the sense of “quantity”).The term emphasizes the way these hops occur in discrete, fixed amounts.
THE CLASSICAL VISION that Einstein had been brought up with was being stretched but still hadn’t broken. In fact, he had been a central player in many of the first twentieth-century advances in the realm of the ultrasmall: so successful that his Nobel Prize wasn’t for his large-scale studies such as G=T, but for work he had done in 1905 explaining how light could be a particle and a wave at the same time. The particle side could be used to explain the way metals so often send electrons shooting out when they are hit by light. To the outside world, this idea seemed another mark of his genius, but to Einstein it only made sense: the universe always has an order, which human reason can find.
A decade after his 1905 finding
s about photons, in his exuberance after first working out G=T in Berlin, Einstein had taken his early work on subatomic particles even further. In the summer of 1916, resting after his exhausting research that had led up to G=T, he detailed how electrons that weren’t otherwise liable to plummet down from “higher” orbits around their atoms could, sometimes, be excited if we pumped in extra light to strike them. When that extra light then made those electrons “fall,” they released their own blasts of light, like Lucifer plummeting down from heaven. That could lead to something of a chain reaction: producing in this case not a deadly atomic explosion, but simply pure, useful light.
Einstein wouldn’t have been able to construct a machine to keep this process going with the limited equipment available in wartime Berlin. But this Light Amplification through the Stimulated Emission of Radiation—the acronym for which led to the name “laser”—would ultimately be understood by his fellow researchers. In this seemingly casual paper, Einstein had laid out the basic dynamics of the laser: the device at the heart of today’s fiber-optic cables, and without which the Internet would not operate. And since he couldn’t know when the jumps were made, he had introduced the probability of their occurring with no cause.
The big question was whether these ideas about photons, electrons, nuclei, and other subatomic objects still fit within the underlying certainty that all of science, since Galileo and Newton, had been finding in the world. Einstein believed that they must—yet his conviction that the universe was governed by orderly, logical principles was increasingly at odds with the latest research. For instance, Einstein disliked the way, at least in his preliminary findings, he couldn’t tell exactly which electrons were going to be knocked out of their orbits first. “The weakness of the theory,” he wrote in his published report, “lies . . . in the fact . . . that it leaves the duration and direction of the elementary processes to ‘chance.’”
At the time, Einstein wasn’t too deeply bothered by the randomness inherent in his theory about light being released from falling electrons. In many other fields, we make do with statistical averages: the heights of recruits into the French and German armies; the color of leaves in a forest at a certain time of year. None of that is taken to mean that randomness truly prevails. We feel that if we looked more closely, we’d be able to trace the sequence of events that led to each recruit being a particular height, or each leaf taking on a particular hue. The common view is that this sort of recourse to statistics, to probability, is not fundamental, but just a convenient shortcut when we’re not able to examine the detailed causality behind each particular object—that if we were to look into those details, the need for probabilities would disappear.
Einstein’s belief that randomness would eventually be dispelled from his theory explains why he put the word “chance” in quotation marks. He knew that within his calculations, it was helpful to talk about the probabilities of the various sorts of transitions. But at heart he remained a classical physicist. He put in the quotation marks to show his belief that if we had the time to look at the details, we’d no doubt see that each transition had simple, precise causes. “The real joke presented to us here by the eternal riddle-setter,” Einstein told his friend Besso, “has absolutely not yet been understood.”
Einstein had faith that the great riddles of the universe could be answered in a logical way. By the mid-1920s, however, results were coming in that seemed to violate that promised clarity—and this is what set Einstein on a collision course with his fellow physicists in the burgeoning study of the ultrasmall.
AS SUBATOMIC RESEARCH progressed into the 1920s, it became increasingly clear that this minuscule realm seemed to follow principles that were far more unexpected than anyone had imagined. Although atoms as simple as hydrogen followed the principles that Bohr had laid out, more complex ones—carbon, gold, aluminum—seemed to have electrons that acted entirely differently. Arnold Sommerfeld and others made attempts to jury-rig fixes and make everything continue to operate by conventional means, such as imagining that the electrons weren’t entirely like solar system planets whirling around the central nucleus all in neat circles on one plane, but instead were following ellipses or flying in complex three-dimensional patterns around the nucleus. But all were stopgaps.
In 1924 Einstein’s friend Max Born, a professor at the great German university of Göttingen, told his top graduate students and teaching assistants that he was fed up with these half measures and wanted to try to find a theory that could address them. He was nearly Einstein’s age, and might have been expected to resist the surprising new phenomena that were so different from what he’d been taught. But although Born was a strong thinker, he was nowhere near Einstein’s level—and that actually gave Born an advantage, for it meant he didn’t have as much invested in his own past achievements as Einstein did. It was the classical approaches that had been so tremendously productive for Einstein. Born, by contrast, had less to lose in jumping to a new view.
Born and his students knew that Isaac Newton had managed to work out the mechanics of the large-scale, visible world we inhabit—of trees, and moons, and powerful steam engines. It was the job of present-day physicists, Born now insisted, to do the same for the underlying micro-world where the new, minuscule “quantum” jumps were taking place. That fresh science—if it could be created—would be called quantum mechanics.
A year later, in 1925, the brightest of Born’s teaching assistants, a handsome, blond-haired, and highly strung twenty-four-year-old named Werner Heisenberg, managed to solve Born’s problem. Heisenberg was a great believer in German romanticism; he loved hiking in Germany’s hills with muscular young men and dreamily watching sunrises. After several months of work, his inspiration came together in an intense burst one night on the North Sea island of Heligoland, on whose clean, windswept beaches he’d sought to escape the hay fever he suffered from on the mainland.
Heisenberg succeeded by putting aside, entirely, any attempt to work out exactly how the electrons in an atom were flying about—whether they were tracing ellipses, flying high over the “north pole” of the nucleus, or following some other pattern. He knew that Einstein, his hero, had achieved great things in relativity by simply looking at what we could measure of an event—be that waking up in a falling elevator or seeing an innocuous piece of radium metal glow with pure energy—without always trying to imagine the details of why it worked that way.
Now, for his own purposes, Heisenberg made lists of what investigators could observe of the light that electrons produced under different circumstances. Those observations changed as the atoms of which the electrons were a part were bombarded with light or otherwise stirred about. He was simply going to record what went in, and record what came out, and work out the simplest mathematical operations to link the two together.
Werner Heisenberg, 1926, one year after his breakthrough on the windswept island of Heligoland
As a very rough analogy for what Heisenberg was attempting, imagine taking note of the clothes a large number of actors were wearing as they hurried backstage to change between acts in one of the large operettas then so popular in Berlin. From that, one wanted to work out how that corresponded with the clothes they were wearing as they came back out for the start of the next act. Some patterns would be clear. Watching the performance, one might see that women dressed as princesses were likely to come out as peasants (if, for example, the story line was moving from a palace to the countryside). Such an analysis would be limited, but in Heisenberg’s new approach, it would be enough. No one would need bother to try to see the rush of individual changes taking place backstage; all that would be measured was what we could observe, appearing “somehow” from behind the curtains.
Heisenberg’s whole process was not that different from the approach Einstein had taken in his early laser system in 1916. There, one arrangement of light photons goes in, and a different one comes out. We can measure them and get good at predicting how the former will lead to the latter.
So it is with the musical theater analogy—and so it was with Heisenberg’s formal calculations on Heligoland in 1925. He could tabulate a range of possible events inside an atom and from that calculate the spectral lines that were seen. As to what “actually” went on inside the atoms to create the output we saw—whether it was inherently unknowable or just too complex to understand yet—was not something that, at that point, he was going to speculate about.
Heisenberg had accomplished what none of the older physicists working on the problem had managed. With the achievement of a lifetime lying in scattered notes on his desk (“It was almost three o’clock in the morning . . . I was far too excited to sleep”), he hiked down to the southernmost tip of Heligoland, climbed a rock jutting into the sea, and—as Einstein and his friends had on the mountain near Bern twenty years before—rested there to watch the sun rise over the North Sea stretching before him. Strict causality had triumphed in the West for hundreds of years. Now, limiting himself to external measurements just as he thought Einstein had—presuming it was not our job to speculate on what went on “inside”—he had a different breakthrough. Heisenberg’s work is considered the birth of the new quantum mechanics.
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