Haber was a short, bald, and dapper chemist who was born Jewish but tried mightily to assimilate by converting, getting baptized, and adopting the dress, manner, and even pince-nez glasses of a proper Prussian. The director of the chemistry institute where Einstein had his office, he had been mediating the war between Einstein and Mari just as the larger war in Europe was breaking out. Although he hoped for a commission as an officer in the army, because he was an academic of Jewish heritage he had to settle for being made a sergeant.43
Haber reorganized his institute to develop chemical weapons for Germany. He had already found a way to synthesize ammonia from nitrogen, which permitted the Germans to mass-produce explosives. He then turned his attention to making deadly chlorine gas, which, heavier than air, would flow down into the trenches and painfully asphyxiate soldiers by burning through their throats and lungs. In April 1915, modern chemical warfare was inaugurated when some five thousand French and Belgians met that deadly fate at Ypres, with Haber personally supervising the attack. (In an irony that may have been lost on the inventor of dynamite, who endowed the prize, Haber won the 1918 Nobel in chemistry for his process of synthesizing ammonia.)
His colleague and occasional academic rival Nernst, bespectacled and 50, had his wife inspect his style as he practiced marching and saluting in front of their house. Then he took his private car and showed up at the western front to be a volunteer driver. Upon his return to Berlin, he experimented with tear gas and other irritants that could be used as a humane way to flush the enemy out of the trenches, but the generals decided they preferred the lethal approach that Haber was taking, so Nernst became part of that effort.
Even the revered Planck supported what he called Germany’s “just war.” As he told his students when they went off to battle, “Germany has drawn its sword against the breeding ground of insidious perfidy.”44
Einstein was able to avoid letting the war cause a personal rift between him and his three colleagues, and he spent the spring of 1915 tutoring Haber’s son in math.45 But when they signed a petition defending Germany’s militarism, he felt compelled to break with them politically.
The petition, published in October 1914, was titled “Appeal to the Cultured World” and became known as the “Manifesto of the 93,” after the number of intellectuals who endorsed it. With scant regard for the truth, it denied that the German army had committed any attacks on civilians in Belgium and went on to proclaim that the war was necessary. “Were it not for German militarism, German culture would have been wiped off the face of the earth,” it asserted. “We shall wage this fight to the very end as a cultured nation, a nation that holds the legacy of Goethe, Beethoven, and Kant no less sacred than hearth and home.”46
It was no surprise that among the scientists who signed was the conservative Philipp Lenard, of photoelectric effect fame, who would later become a rabid anti-Semite and Einstein hater. What was distressing was that Haber, Nernst, and Planck also signed. As both citizens and scientists, they had a natural instinct to go along with the sentiments of others. Einstein, on the other hand, often displayed a natural inclination not to go along, which sometimes was an advantage both as a scientist and as a citizen.
A charismatic adventurer and occasional physician named Georg Friedrich Nicolai, who had been born Jewish (his original name was Lewinstein) and was a friend of both Elsa and her daughter Ilse, worked with Einstein to write a pacifist response. Their “Manifesto to Europeans” appealed for a culture that transcended nationalism and attacked the authors of the original manifesto. “They have spoken in a hostile spirit,” Einstein and Nicolai wrote. “Nationalist passions cannot excuse this attitude, which is unworthy of what the world has heretofore called culture.”
Einstein suggested to Nicolai that Max Planck, even though he had been one of the signers of the original manifesto, might also want to participate in their countermanifesto because of his “broad-mindedness and good will.” He also gave Zangger’s name as a possibility. But neither man, apparently, was willing to get involved. In an indication of the temper of the times, Einstein and Nicolai were able to garner only two other supporters. So they dropped their effort, and it was not published at the time.47
Einstein also became an early member of the liberal and cautiously pacifist New Fatherland League, a club that pushed for an early peace and the establishment of a federal structure in Europe to avoid future conflicts. It published a pamphlet titled “The Creation of the United States of Europe,” and it helped get pacifist literature into prisons and other places. Elsa went with Einstein to some of the Monday evening meetings until the group was banned in early 1916.48
One of the most prominent pacifists during the war was the French writer Romain Rolland, who had tried to promote friendship between his country and Germany. Einstein visited him in September 1915 near Lake Geneva. Rolland noted in his diary that Einstein, speaking French laboriously, gave “an amusing twist to the most serious of subjects.”
As they sat on a hotel terrace amid swarms of bees plundering the flowering vines, Einstein joked about the faculty meetings in Berlin where each of the professors would anguish over the topic “why are we Germans hated in the world” and then would “carefully steer clear of the truth.” Daringly, maybe even recklessly, Einstein openly said that he thought Germany could not be reformed and therefore hoped the allies would win, “which would smash the power of Prussia and the dynasty.”49
The following month, Einstein got into a bitter exchange with Paul Hertz, a noted mathematician in Göttingen who was, or had been, a friend. Hertz was an associate member of the New Fatherland League with Einstein, but he had shied away from becoming a full member when it became controversial. “This type of cautiousness, not standing up for one’s rights, is the cause of the entire wretched political situation,” Einstein berated. “You have that type of valiant mentality the ruling powers love so much in Germans.”
“Had you devoted as much care to understanding people as to understanding science, you would not have written me an insulting letter,” Hertz replied. It was a telling point, and true. Einstein was better at fathoming physical equations than personal ones, as his family knew, and he admitted so in his apology. “You must forgive me, particularly since—as you yourself rightly say—I have not bestowed the same care to understanding people as to understanding science,” he wrote.50
In November, Einstein published a three-page essay titled “My Opinion of the War” that skirted the border of what was permissible, even for a great scientist, to say in Germany. He speculated that there existed “a biologically determined feature of the male character” that was one of the causes of wars. When the article was published by the Goethe League that month, a few passages were deleted for safety’s sake, including an attack on patriotism as potentially containing “the moral requisites of bestial hatred and mass murder.”51
The idea that war had a biological basis in male aggression was a topic Einstein also explored in a letter to his friend in Zurich, Heinrich Zangger. “What drives people to kill and maim each other so savagely?” Einstein asked. “I think it is the sexual character of the male that leads to such wild explosions.”
The only method of containing such aggression, he argued, was a world organization that had the power to police member nations.52 It was a theme he would pick up again eighteen years later, in the final throes of his pure pacifism, when he engaged in a public exchange of letters with Sigmund Freud on both male psychology and the need for world government.
The Home Front, 1915
The early months of the war in 1915 made Einstein’s separation from Hans Albert and Eduard more difficult, both emotionally and logistically. They wanted him to come visit them in Zurich for Easter that year, and Hans Albert, who was just turning 11, wrote him two letters designed to pull at his heart: “I just think: At Easter you’re going to be here and we’ll have a Papa again.”
In his next postcard, he said that his younger brother told him about
having a dream “that Papa was here.” He also described how well he was doing in math. “Mama assigns me problems; we have a little booklet; I could do the same with you as well.”53
The war made it impossible for him to come at Easter, but he responded to the postcards by promising Hans Albert that he would come in July for a hiking vacation in the Swiss Alps. “In the summer I will take a trip with just you alone for a fortnight or three weeks,” he wrote. “This will happen every year, and Tete [Eduard] may also come along when he is old enough for it.”
Einstein also expressed his delight that his son had taken a liking to geometry. It had been his “favorite pastime” when he was about the same age, he said, “but I had no one to demonstrate anything to me, so I had to learn it from books.” He wanted to be with his son to help teach him math and “tell you many fine and interesting things about science and much else.” But that would not always be possible. Perhaps they could do it by mail? “If you write me each time what you already know, I’ll give you a nice little problem to solve.” He sent along a toy for each of his sons, along with an admonition to brush their teeth well. “I do the same and am very happy now to have kept enough healthy teeth.”54
But the tension in the family worsened. Einstein and Mari exchanged letters arguing about both money and vacation timing, and at the end of June a curt postcard came from Hans Albert. “If you’re so unfriendly to her,” he said of his mother, “I don’t want to go with you.” So Einstein canceled his planned trip to Zurich and instead went with Elsa and her two daughters to the Baltic sea resort of Sellin.
Einstein was convinced that Mari was turning the children against him. He suspected, probably correctly, that her hand was behind the postcards Hans Albert was sending, both the plaintive ones making him feel guilty for not being in Zurich and the sharper ones rejecting vacation hikes. “My fine boy had been alienated from me for a few years already by my wife, who has a vengeful disposition,” he complained to Zangger. “The postcard I received from little Albert had been inspired, if not downright dictated, by her.”
He asked Zangger, who was a professor of medicine, to check on young Eduard, who had been suffering ear infections and other ailments. “Please write me what is wrong with my little boy,” he pleaded. “I’m particularly fondly attached to him; he was still so sweet to me and innocent.”55
It was not until the beginning of September that he finally made it to Switzerland. Mari felt it would be proper for him to stay with her and the boys, despite the strain. They were, after all, still married. She had hopes of reconciling. But Einstein showed no interest in being with her. Instead, he stayed in a hotel and spent a lot of time with his friends Michele Besso and Heinrich Zangger.
As it turned out, he got a chance to see his sons only twice during the entire three weeks he was in Switzerland. In a letter to Elsa, he blamed his estranged wife: “The cause was mother’s fear of the little ones becoming too dependent on me.” Hans Albert let his father know that the whole visit made him feel uncomfortable.56
After Einstein returned to Berlin, Hans Albert paid a call on Zangger. The kindly medical professor, friends of all sides in the dispute, tried to work out an accord so that Einstein could visit his sons. Besso also played intermediary. Einstein could see his sons, Besso advised in a formal letter he wrote after consulting with Mari, but not in Berlin nor in the presence of Elsa’s family. It would be best to do it at “a good Swiss inn,” initially just with Hans Albert, where they could spend some time on their own free of all distractions. Over Christmas, Hans Albert was planning to visit Besso’s family, and he suggested that perhaps Einstein could come then.57
The Race to General Relativity, 1915
What made the flurry of political and personal turmoil in the fall of 1915 so remarkable was that it highlighted Einstein’s ability to concentrate on, and compartmentalize, his scientific endeavors despite all distractions. During that period, with great effort and anxiety, he was engaged in a competitive rush to what he later called the greatest accomplishment of his life.58
Back when Einstein had moved to Berlin in the spring of 1914, his colleagues had assumed that he would set up an institute and attract acolytes to work on the most pressing problem in physics: the implications of quantum theory. But Einstein was more of a lone wolf. Unlike Planck, he did not want a coterie of collaborators or protégés, and he preferred to focus on what again had become his personal passion: the generalization of his theory of relativity.59
So after his wife and sons left him for Zurich, Einstein moved out of their old apartment and rented one that was nearer to Elsa and the center of Berlin. It was a sparsely furnished bachelor’s refuge, but still rather spacious: it had seven rooms on the third floor of a new five-story building.60
Einstein’s study at home featured a large wooden writing table that was cluttered with piles of papers and journals. Padding around this hermitage, eating and working at whatever hours suited him, sleeping when he had to, he waged his solitary struggle.
Through the spring and summer of 1915, Einstein wrestled with his Entwurf theory, refining it and defending it against a variety of challenges. He began calling it “the general theory” rather than merely “a generalized theory” of relativity, but that did not mask its problems, which he kept trying to deflect.
He claimed that his equations had the greatest amount of covariance that was permissible given his hole argument and other strictures of physics, but he began to suspect that this was not correct. He also got into an exhausting debate with the Italian mathematician Tullio Levi-Civita, who pointed out problems with his handling of the tensor calculus. And there was still the puzzle of the incorrect result the theory gave for the shift in Mercury’s orbit.
At least his Entwurf theory still successfully explained—or so he thought through the summer of 1915—rotation as being a form of relative motion, that is, a motion that could be defined only relative to the positions and motions of other objects. His field equations, he thought, were invariant under the transformation to rotating coordinates.61
Einstein was confident enough in his theory to show it off at a weeklong series of two-hour lectures, starting at the end of June 1915, at the University of Göttingen, which had become the preeminent center for the mathematical side of theoretical physics. Foremost among the geniuses there was David Hilbert, and Einstein was particularly eager—too eager, it would turn out—to explain all the intricacies of relativity to him.
The visit to Göttingen was a triumph. Einstein exulted to Zangger that he had “the pleasurable experience of convincing the mathematicians there thoroughly.” Of Hilbert, a fellow pacifist, he added, “I met him and became quite fond of him.” A few weeks later, after again reporting, “I was able to convince Hilbert of the general theory of relativity,” Einstein called him “a man of astonishing energy and independence.” In a letter to another physicist, Einstein was even more effusive: “In Göttingen I had the great pleasure of seeing that everything was understood down to the details. I am quite enchanted with Hilbert!”62
Hilbert was likewise enchanted with Einstein and his theory. So much so that he soon set out to see if he could beat Einstein to the goal of getting the field equations right. Within three months of his Göttingen lectures, Einstein was confronted with two distressing discoveries: that his Entwurf theory was indeed flawed, and that Hilbert was racing feverishly to come up with the correct formulations on his own.
Einstein’s realization that his Entwurf theory was unraveling came from an accumulation of problems. But it culminated with two major blows in early October 1915.
The first was that, upon rechecking, Einstein found that the Entwurf equations did not actually account for rotation as he had thought.63 He hoped to prove that rotation could be conceived of as just another form of relative motion, but it turned out that the Entwurf didn’t actually prove this. The Entwurf equations were not, as he had believed, covariant under a transformation that uniformly rotated the coor
dinate axes.
Besso had warned him in a memo in 1913 that this seemed to be a problem. But Einstein had ignored him. Now, upon redoing his calculations, he was dismayed to see this pillar knocked away. “This is a blatant contradiction,” he lamented to the astronomer Freundlich.
He assumed that the same mistake also accounted for his theory’s inability to account fully for the shift in Mercury’s orbit. And he despaired that he would not be able to find the problem. “I do not believe I am able to find the mistake myself, for in this matter my mind is too set in a deep rut.”64
In addition, he realized that he had made a mistake in what was called his “uniqueness” argument: that the sets of conditions required by energy-momentum conservation and other physical restrictions uniquely led to the field equations in the Entwurf. He wrote Lorentz explaining in detail his previous “erroneous assertions.”65
Added to these problems were ones he already knew about: the Entwurf equations were not generally covariant, meaning that they did not really make all forms of accelerated and nonuniform motion relative, and they did not fully explain Mercury’s anomalous orbit. And now, as this edifice was crumbling, he could hear what seemed to be Hilbert’s footsteps gaining on him from Göttingen.
Part of Einstein’s genius was his tenacity. He could cling to a set of ideas, even in the face of “apparent contradiction” (as he put it in his 1905 relativity paper). He also had a deep faith in his intuitive feel for the physical world. Working in a more solitary manner than most other scientists, he held true to his own instincts, despite the qualms of others.
But although he was tenacious, he was not mindlessly stubborn. When he finally decided his Entwurf approach was untenable, he was willing to abandon it abruptly. That is what he did in October 1915.
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