Their calculation, mostly in Einstein’s handwriting with corrections and a few more substantial contributions from Besso, offers some guilty pleasures. Einstein made a couple of elementary blunders—multiplying the mass of the sun by an extra factor of ten, for example—the kind of careless mistakes that come as a comfort to us mere mortals. He also made at least one more serious error in persuading himself that an approximate solution for another, more abstract test of the theory was valid when it was not.
At the same time, the work offers a rare window into the act of scientific thinking, a very different kind of picture than the ones to be found in the static, artificial picture of discovery in most published results. Einstein is groping here, both trying to master the big ideas in an unfamiliar and difficult body of mathematics and to develop the specific techniques to use that math to generate detailed accounts of the behavior of matter in motion. The calculation for the orbit of Mercury contains a real advance. In it, Einstein developed a valid method to analyze the motion of a planet moving through curved space-time. But given the still-hidden flaws in the Einstein-Grossman version of gravitation, that technical achievement didn’t help just yet. Instead, when they worked through all the steps, Einstein and Besso found that they still could only account for just eighteen of the forty-three arcseconds per century they needed.
Credit 9.1
In this letter to the American astronomer George Ellery Hale, Einstein seeks advice about measuring the deflection of starlight around the sun.
On the face of it, that was as much a failed result as any of the Vulcan sightings and misidentified sunspots were under Newtonian gravitation. Einstein himself seemed to respond to the problem just as Vulcan’s partisans had decades before: the failure to confirm his view mattered less than the theory itself. If a relativistic account of gravity made sense, if it retained its logical and explanatory power, a single missing confirmation was hardly reason to abandon it.
Still, such a result was certainly nothing to advertise. Einstein never published this particular exercise. Instead, he just kept going. He knew that Newtonian gravity was inadequate as a matter of principle—the conflict with special relativity that could not be wished away. He could feel the logic of a relativistic theory of gravity accumulating with each new insight. If it was not yet fully formed, he was still convinced that it represented the only reasonable path forward—so much so that he was prepared to subject it to the most public of tests. The next total eclipse of the sun was scheduled for August 21, 1914. Russia’s Crimean peninsula, jutting out into the Black Sea, offered prime viewing conditions. There, astronomers would have their first chance to check the theory’s major prediction: that a ray of light from a star grazing the edge of the sun would be deflected by .87 arcseconds off its usual path as it careened around that patch of sharply bent space-time. The symmetry is obvious: Vulcan, of course, had been sought and seen and unseen again in such conditions.
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There was, however, an obstacle in the way of testing Einstein’s account of gravity (and hence of Mercury’s motion) at the 1914 eclipse—one that had nothing to do with his scientific argument. Einstein himself had risen far since his miracle year, but as a professor in Zurich he had no real hope of finding the funding to mount an expedition to Russia. In July 1913, that ceased to be a problem. Two men from Berlin came to call on him, Max Planck and Walther Nernst, both future Nobel laureates. They made Einstein an unprecedented offer: if he would abandon the Swiss and join them in Germany’s imperial capital, he’d gain a truly impressive salary, a faculty appointment with no teaching requirements, and membership in the Prussian Academy of Sciences.
Despite such temptations, there were plenty of reasons for Einstein to reject the invitation. Einstein loved Zurich, and had renounced his German citizenship at the earliest opportunity more than a decade earlier. But this offer said, in effect, that if he came to Berlin, he’d arrive as first among equals within the single most impressive collection of scientific talent in the world.
Einstein took a day to think it over, but it really was too good a deal to refuse. It also came with an implied bonus: his Berlin hosts wanted him to be happy. In practice, that meant he could now draw on enough money to fund an eclipse-spotting team.
Einstein left Zurich in March 1914. He crisscrossed Europe for a few weeks visiting physicist friends before settling into the Berlin suburb of Dahlem in April. His marriage didn’t survive the move. Marić and their sons returned to Zurich in early July, and Einstein, though he wept as they left, swiftly returned to what he clearly loved best, thinking about physics unburdened by (as he called it) “the merely personal.”
The eclipse expedition was duly organized. The Prussian Academy paid part of the total—the expected sweetener to charm their newest recruit—and the patriarch of the Krupp family covered the balance. Erwin Freundlich, a young astronomer and Einstein enthusiast, selected four camera-equipped telescopes and recruited two companions. They left Berlin for the Crimea on July 19. No one seemed to think that an event three weeks earlier would impinge on such a purely disinterested quest. What possible concern could it be for stargazers from Germany, bound for Russia, that on the 28th of June, 1914, in the Serbian city of Sarajevo, an Austrian archduke had got himself shot?
* * *
*1 Sadly, there is no solid evidence that they ever spoke to each other.
*2 Einstein did not simply settle for pictures. In this, his first paper on gravity in several years, he started to generate some hard numbers. For the bending of light, he calculated how much a mass the size of the sun would divert a ray of starlight just scraping past its edge. He came up with a figure, .87 of an arcsecond, that was, not quite coincidentally, the same value that Newton’s theory generates. The number was wrong, as we shall see, but Einstein believed it for the next four years. By way of scale: a circle can be divided up into 360 degrees. Each degree splits up into sixty minutes (or arcminutes, or minutes of arc, depending on such niceties as whether one speaks English or American), and each minute can be further divided into sixty seconds of arc. .87 seconds of arc is a small but not impossibly tiny number. If one were to draw a line from the Bulfinch dome atop the state capitol in Boston to Times Square, that line would stretch approximately two hundred miles. Coming to rest at the half-price Broadway ticket booth at the heart of the square, a deviation of .87 arcseconds would land one about six feet to either side of the line queuing for the chance of the latest hot seat.
*3 Richard Feynman, in the final lecture reprinted in Six Not-So-Easy Pieces, presents one of the best and most straightforward discussions of the ideas discussed here, but the clock-and-rocket-ship example has been around for quite some time. Feynman does give a nice sense of perspective, providing, for example, a number for the amount that time slows as one climbs to weaker and weaker heights in the earth’s gravitational field. Every twenty meters up alters the frequency of light, and hence the measurement of time, by two parts in a thousand trillion (2/1015).
“BESIDE HIMSELF WITH JOY”
July 1914.
In Berlin, a delight.
Looking back years later, long after Europe’s Great Powers consummated their four-year murder-suicide pact, it seemed life had never been sweeter. Journalist Theodor Wolff crystallized those last prewar weeks in the craze of the day: “The Berlin public discovered a new passion,” he wrote. “After the one-step and the two-step had done their duty, the new miracle was called Tango.”
The pleasures of the season persisted for a good while after a Serbian radical killed the Austrian archduke Franz Ferdinand and his wife, Sophie, on the 28th of June. The next morning, the first printing of the Frankfurter Zeitung—Germany’s most serious newspaper—covered the murder. The second edition, though, returned to conventional summer fare, including an article urging public support for the Berlin Olympic games slated for 1916. Three weeks later, the press still covered what seemed—and was!—a perfectly normal summer. On July 21 the Berliner Volksbl
att told its readers how to get a tan, while warning of the possibly immoral costumes that produced the best results. Perhaps the most striking proof of the incomprehensibility of war in those last weeks appeared in the classified ads: during that summer the Frankfurter Zeitung carried for-sale notices aimed at their upscale audience—for vacation property in Russia.
It was thus utterly ordinary that a German scientific expedition should show up on Russia’s Black Sea coast in the last week of July, just ahead of the eclipse that would pass that way on August 21. Erwin Freundlich and his colleagues had come to measure what Albert Einstein had told them to look for: the bending of starlight around the sun. They met up with a group of astronomers from Argentina who were, in a coincidence no fictional account would tolerate, just about the last holdouts, a group seeking to photograph a hypothesized planet inside the orbit of Mercury planet—that old friend, Vulcan.
Then, in less than a week, sunlit Europe, dancing Europe vanished. On the 30th of July, Nicholas, Czar of all the Russias, committed his empire to full military mobilization. Germany called on Russia’s ally France to remain neutral. France refused, mobilizing on the 31st. On August 1, the German ambassador to Russia delivered a document to the foreign ministry in St. Petersburg: the formal declaration of war.
That night, a small German force entered neutral Belgium. Germany’s patrols crossed into France on the 2nd and delivered the now redundant paperwork the next day. Finally, at 11 P.M. on August 4, His Majesty’s government made its decision, informing the Kaiser’s ambassador to the Court of St. James’s that a state of war existed between the British Empire and the German Reich. Among the least noted consequences of that rush to war: three German scientists had just become enemies to their hosts. Freundlich and his companions were arrested and interned, their equipment seized.
In the end, it didn’t matter. The eclipse was a tease. Clouds gathered just before totality and cleared beautifully only after it passed; no light-bending observations could have been made. The German astronomers were lucky. Detained only briefly, they were swapped for Russian officers in one of the first prisoner exchanges of the war. To Einstein’s relief, he was able to welcome them back to Berlin by the end of September.
—
That was one of Einstein’s few consolations in that miserable time. He never reconciled himself to the shock of the war—not merely the fact of battle, but the naked joy that everyone, it seemed, took in the fight. “That a man can take pleasure in marching in fours to the strains of a band is enough to make me despise him,” he wrote years later. “Heroism on command, senseless violence and all the loathsome nonsense that goes by the name of patriotism—how passionately I hate them.” What was worse, in Einstein’s eyes, was that the extraordinary collection of scientific minds that had lured him to Berlin turned out to be as war-drunk as any mob in the street.
The most potent symbol of this almost-personal betrayal was Einstein’s closest Berlin friend, Fritz Haber, who would later win the Nobel Prize for chemistry. With the start of the war, he shifted his lab to a near-total military focus. The element chlorine caught his attention, as he pursued what he hoped would be the weapon to end the war to end all wars: lethal poison gas, illegal under prewar agreements, which he now proposed to deliver to the German General Staff.
Haber managed to produce battlefield-ready chemical munitions early in 1915. That spring, cylinders loaded with chlorine were shipped to the Western Front, to be deployed on the Ypres battlefield in Belgium. After weeks spent waiting for the winds to blow steadily from east to west, April 22 offered made-to-order conditions. As dusk approached, German soldiers released 168 tons of chlorine gas along a four-mile front.
In its path stood three divisions: one Algerian, one territorial (the equivalent of a national guard unit), both under French colors, and one Canadian. A green-tinged cloud advanced, drifting, rolling, stretching across the muddy wreck of no-man’s-land. The Germans waited until the billowing mass of chlorine reached the Allied lines. The effect was everything Haber had hoped for: hundreds of soldiers “were thrown into a comatose or dying position,” as General Sir John French reported. The Algerians broke, leaving a gap in the line. The Germans advanced, taking two thousand prisoners and a number of artillery pieces—until the Canadians reformed and reasserted the relentless stasis of trench warfare.
Such a “victory” was a fiasco typical of the brutal stasis that had already gripped the Western Front. Achieving complete surprise, using a weapon for which their enemy had no defense, the Germans gained exactly nothing. The Germans had no reserves available to exploit an advantage they possessed for the briefest of moments. The western Allies soon retaliated with gas munitions of their own, with no greater tactical success than the Germans.
Gas was and remains a terror weapon, ineffective against prepared and similarly armed opponents. Both sides would continue to launch poison attacks throughout that “great” war—and Haber himself persisted for years, seeking the one magic formula that would at last deliver a strategic breakthrough rather than just a particularly nasty increment to the misery of trench warfare. He never found it.
To Einstein, this was simply madness. “Our whole, highly praised technological progress,” he wrote in what is now one of his most famous aphorisms, “and civilization in general can be likened to an axe in the hand of a pathological criminal.” World War I broke something in Einstein, destroying forever the faith he’d affirmed until the fall of 1914—that there was a genuinely supranational, disinterested elite of the mind, united by what he most valued, the study of “this huge world, which exists independently of us human beings and which stands before us like a great external riddle.” As a youth he “soon noticed that many a man whom I had learned to esteem and admire had found inner freedom and security in devoted occupation with it.” Those were the people he thought he’d joined in Berlin, and now, mere months after his arrival, they had (as he saw it) abandoned him.
Yet he stayed. He didn’t have to. He still held Swiss citizenship, and he was able to cross the border between Germany and Switzerland during the war. Zurich had long been his favorite city, and as the British naval blockade came to bite, wartime Berlin would become not just politically grim but flat-out hungry. None of that seemed to matter. Berlin, it turned out, had one unsurpassed advantage. If all his colleagues were consumed by the passion and labor of war, at least they left him undisturbed. His wife and children were gone. He lived alone. He kept his office in Haber’s chemistry institute, while ignoring that which he disdained going on all around him. Uninterrupted, he could think.
—
So, once the initial shock of August wore off, Einstein got back to work. On October 19, he delivered the first of two lectures to the Prussian Academy. He spoke not of war, but of gravity, introducing what he now saw as a substantially complete generalization of relativity.
In those talks, Einstein argued that his new theory presented not just the solutions to certain problems, but a whole new way of thinking. He explained the significance of his prior work on non-Euclidean geometries, those mathematical systems in which parallel lines could meet and space warps. Such concepts were not just abstract toys for clever mathematicians but, rather, he said, should be understood as actual candidate descriptions of the real world. Using them, it became possible to contrast competing ideas: Newton’s account of gravity as a force and Einstein’s own, in which the shape of space-time determines how objects move.
It was an utterly foreign message for that audience. To be fair, Einstein admitted that his theory was not yet complete, even if it seemed to him logically sufficient. But the claim that geometry was destiny was simply too bizarre a thought for most. Even allowing for such difficulties, though, it’s remarkable that none of his German colleagues, despite all the effort they’d expended to lure Einstein into their midst, paid any real notice to what they’d just heard: first, that Isaac Newton was wrong about gravitation, and second, that to get gravity right, physicists had
to reimagine fundamental assumptions about the behavior of the universe. Einstein told them to their faces, twice, and he published the argument as a fifty-five-page article in the proceedings of the Prussian Academy. When his article appeared, Einstein did receive a few letters from foreign researchers exploring the corners of his ideas, but nothing fundamental. No one in Berlin went even that deep.
Einstein was unsurprised. The year before, the dean of German physics, Max Planck, had warned him not to tackle gravity. It was too hard a problem, he said, and “even if you succeed no one will believe you.” Science may celebrate the triumph of the better idea. Scientists don’t, not always, not immediately, not when the strangeness involved takes extraordinary effort to embrace.
Einstein ignored both Planck’s advice and the apathy of his colleagues. His October lectures contained the most complete account of his ideas about gravitation he could manage. A problem remained with the interpretation of his equations: in certain circumstances his 1913–14 theory violated a key claim of special relativity, that every observer in motion relative to each other must come up with the same description of an event in the mathematical language of space-time.
For the time being, Einstein didn’t think that reversal invalidated the generalization of relativity to motion under the influence of gravity. That, he was convinced, had to be right. Nonetheless, the loss of invariance was certainly worrisome. For the moment, though, he had reached his limit. If there were errors, he could not—yet—recognize them.
The first year of the war came to an end, marked by the beautiful and melancholy Christmas Truce spontaneously declared by ordinary soldiers on both sides of the Western Front. Einstein gave the first months of 1915 over to various distractions, including an utterly unsuccessful jaunt into the wilds of experimental physics. He thought about the battlefield, and his hatred of it, and later that year distilled his anger into his first public statement on war and peace.
The Hunt for Vulcan Page 14
