Her circumstances, perhaps combined with an innate disposition, caused her to become gloomy, even depressed. When Philipp Frank met her in Prague for the first time, he thought that she might be schizophrenic. Einstein concurred, and he later told a colleague that her gloominess “is doubtless traceable to a schizophrenic genetic disposition coming from her mother’s family.”37
Thus it was that Einstein’s marriage was once again in an unstable state when he traveled alone to Berlin during the Easter holidays in 1912. There he became reacquainted with a cousin, three years older, whom he had known as a child.
Elsa Einstein* was the daughter of Rudolf (“the rich”) Einstein and Fanny Koch Einstein. She was Einstein’s cousin on both sides. Her father was the first cousin of Einstein’s father, Hermann, and had helped fund his business. Her mother was the sister of Einstein’s mother, Pauline (making Elsa and Albert first cousins). After Hermann’s death, Pauline had moved in with Rudolf and Fanny Einstein for a few years, helping them keep house.
As children, Albert and Elsa had played together at the home of Albert’s parents in Munich and on one occasion had shared a first artistic experience at the opera.38 Since then, Elsa had been married, divorced, and now, at age 36, was living with her two daughters, Margot and Ilse, in the same apartment building as her parents.
The contrast with Einstein’s wife was stark. Mileva Mari was exotic, intellectual, and complex. Elsa wasn’t. Instead, she was conventionally handsome and domestically nurturing. She loved heavy German comfort foods and chocolate, which tended to give her a rather ample, matronly look. Her face was similar to her cousin’s, and it would become strikingly more so as they aged.39
Einstein was looking for new companionship, and he first flirted with Elsa’s sister. But by the end of his Easter visit, he had settled on Elsa as offering the comfort and nurturing that he now craved. The love he was seeking, it seems, was not wild romance but uncomplicated support and affection.
And Elsa, who revered her cousin, was eager to give it. When he returned to Prague, she wrote him right away—sending the letter to his office, not his home, and proposing a way they could correspond in secret. “How dear of you not to be too proud to communicate with me in such a way!” he responded. “I can’t even begin to tell you how fond I have become of you during these few days.” She asked him to destroy her letters, which he did. She, on the other hand, kept his responses for the rest of her life in a folder that she tied and later labeled “Especially beautiful letters from better days.”40
Einstein apologized for his flirtation with her sister Paula.“It is hard for me to understand how I could have taken a fancy to her,” he declared. “But it is in fact simple. She was young, a girl, and complaisant.”
A decade earlier, when he was writing his love letters to Mari that celebrated their own rarefied and bohemian approach to life, Einstein would likely have lumped relatives such as Elsa into the category of “bourgeois philistines.” But now, in letters that were almost as effusive as the ones he had written to Mari, he professed his new passion for Elsa. “I have to have someone to love, otherwise life is miserable,” he wrote. “And this someone is you.”
She knew how to make him defensive: she teased him for being under Mari’s thumb and asserted that he was “henpecked.” As she may have hoped, Einstein responded by protesting that he would show her otherwise. “Do not think about me in such a way!” he said. “I categorically assure you that I consider myself a full-fledged male. Perhaps I will sometime have the opportunity to prove it to you.”
Spurred by this new affection and by the prospect of working in the world’s capital of theoretical physics, Einstein developed a desire to move to Berlin. “The chances of getting a call to Berlin are, unfortunately, slight,” he admitted to Elsa. But on his visit, he did what he could to increase his chances of someday getting a position there. In his notebook he listed appointments he had been able to get with important academic leaders, including the scientists Fritz Haber, Walther Nernst, and Emil Warburg.41
Einstein’s son Hans Albert later recalled that it was just after his eighth birthday, in the spring of 1912, when he noticed that his parents’ marriage was falling apart. But after returning to Prague from Berlin, Einstein seemed to develop qualms about his affair with his cousin. He tried, in two letters, to put an end to it. “There would only be confusion and misfortune if we were to give into our mutual attraction,” he wrote Elsa.
Later that month, he tried to be even more definitive. “It will not be good for the two of us, as well as for the others, if we form a closer attachment. So, I am writing to you today for the last time and am submitting again to the inevitable, and you must do the same. You know that it is not hardness of heart or lack of feeling that makes me talk like this, because you know that, like you, I bear my cross without hope.”42
Einstein and Mari shared one thing: a feeling that living among the middle-class German community in Prague had become wearisome. “These are not people with natural sentiments,” he told Besso. They displayed “a peculiar mixture of snobbery and servility, without any kind of goodwill toward their fellow men.” The water was un-drinkable, the air was full of soot, and an ostentatious luxury was juxtaposed with misery on the streets. But what offended Einstein most were the artificial class structures. “When I come to the institute,” he complained, “a servile man who smells of alcohol bows and says, ‘your most humble servant.’ ”43
Mari worried that the bad water, milk, and air were hurting the health of their younger son, Eduard. He had lost his appetite and was not sleeping well. It was also now clear that her husband cared more about his science than his family. “He is tirelessly working on his problems; one can say that he lives only for them,” she told her friend Helene Savi. “I must confess with a bit of shame that we are unimportant to him and take second place.”44
So Einstein and his wife decided to return to the one place they thought could restore their relationship.
Zurich, 1912
The Zurich Polytechnic, where Einstein and Mari had blissfully shared their books and their souls, had been upgraded in June 1911 to a full university, now named the Eidgenössische Technische Hochschule (ETH), or the Swiss Federal Institute of Technology, with the right to grant graduate degrees. At 32 and by now quite famous in the world of theoretical physics, Einstein should have been an easy and obvious choice for one of the new professorships available there.
That possibility had been discussed a year earlier. Before he left for Prague, Einstein had made a deal with officials in Zurich. “I promised in private that I would advise them before accepting another offer from somewhere else, so that the administration of the Polytechnic could also make me an offer if they find it fit to do so,” he told a Dutch professor who was trying to recruit him to Utrecht.45
By November 1911, Einstein had received such an offer from Zurich, or at least so he thought, and as a result he declined the offer to go to Utrecht. But the matter was not completely settled, because some of Zurich’s education officials objected. They argued that a professor in theoretical physics was a “luxury,” that there was not enough lab space to accommodate one, and that Einstein personally was not a good teacher.
Heinrich Zangger, a longtime friend who was a medical researcher in Zurich, intervened on Einstein’s behalf. “A proper theoretical physicist is a necessity these days,” he wrote in a letter to one of the top Swiss councilors. He also pointed out that in such a role Einstein “needs no laboratory.” As for Einstein’s teaching talents, Zangger provided a wonderfully nuanced and revealing description:
He is not a good teacher for mentally lazy gentlemen who merely want to fill a notebook and then learn it by heart for an exam; he is not a smooth talker, but anyone wishing to learn honestly how to develop his ideas in physics in an honest way, from deep within, and how to examine all premises carefully and see the pitfalls and the problems in his reflections, will find Einstein a first-class teacher, because all o
f this is expressed in his lectures, which force the audience to think along.46
Zangger wrote Einstein to express his outrage at the dithering in Zurich, and Einstein replied, “The dear Zurich folks can kiss my . . . [und die lieben Züricher können mich auch . . . (ellipses are in original letter)].” He told Zangger not to push the matter further. “Leave the Polytechnic* to God’s inscrutable ways.”47
Einstein, however, decided not to drop the matter but instead to push the Polytechnic through a light ruse. Officials at the university in Utrecht were just about to offer their open post to someone else, Peter Debye, when Einstein asked them to hold off. “I am turning to you with a strange request,” he wrote. The Zurich Polytechnic had initially seemed very eager to recruit him, he said, and it had been proceeding with haste out of fear that he would go to Utrecht. “But if they were to learn in the near future that Debye is going to Utrecht, they would lose their fervor at once and keep me forever in suspense. I ask you therefore to wait a little longer with the official offer to Debye.”48
Rather oddly, Einstein found himself needing letters of recommendation to secure a post at his own alma mater. Marie Curie wrote one. “In Brussels, where I attended a scientific conference in which Mr. Einstein also participated, I was able to admire the clarity of his intellect, the breadth of his information, and the profundity of his knowledge,” she noted.49
Adding to the irony was that his other main letter of recommendation came from Henri Poincaré, the man who had almost come up with the special theory of relativity but still had not embraced it. Einstein was “one of the most original minds I have ever come across,” he said. Particularly poignant was his description of Einstein’s willingness, which Poincaré himself lacked, to make radical conceptual leaps: “What I admire in him in particular is the facility with which he adapts himself to new concepts. He does not remain attached to classical principles, and, when presented with a problem in physics, is prompt to envision all the possibilities.” Poincaré, however, could not resist asserting, perhaps with relativity in mind, that Einstein might not be right in all his theories: “Since he seeks in all directions one must expect the majority of the paths on which he embarks to be blind alleys.”50
Soon it all worked out. Einstein would move back to Zurich in July 1912. He thanked Zangger for helping him to prevail “against all odds,” and exulted, “I am enormously happy that we will be together again.” Mari was thrilled as well. She thought that the return could help save both her sanity and their marriage. Even the children seemed happy to be out of Prague and back to the city of their birth. As Einstein put it in a postcard to another friend,“Great joy about it among us old folks and the two bear cubs.”51
His departure caused a minor controversy in Prague. Newspaper articles noted that anti-Semitism at the university may have played a role. Einstein felt compelled to issue a public statement. “Despite all presumptions,” he said,“I did not feel and did not notice any religious prejudice.” The appointment of Philipp Frank, a Jew, as his successor, he added, confirmed that “such considerations”were not a major problem.52
Life in Zurich should have been glorious. The Einsteins were able to afford a modern six-room apartment with grand views. They were reunited with friends such as Zangger and Grossmann, and there was even one fewer adversary. “The fierce Weber has died, so it will be very pleasant from a personal point of view,” Einstein wrote of their undergraduate physics professor and nemesis, Heinrich Weber.53
Once again there were musical gatherings at the home of math professor Adolf Hurwitz. The programs included not only Mozart, Einstein’s favorite, but also Schumann, who was Mari’s. On Sunday afternoons, Einstein would arrive with his wife and two little boys at the doorstep and announce, “Here comes the whole Einstein hen house.”
Despite being back with such friends and diversions, Mari’s depression continued to deepen, and her health to decline. She developed rheumatism, which made it hard for her to go out, especially when the streets became icy in winter. She attended the Hurwitz recitals less frequently, and when she did show up her gloom was increasingly evident. In February 1913, to entice her out, the Hurwitz family planned an all-Schumann recital. She came, but seemed paralyzed by pain, both mental and physical.54
Thus the atmosphere was ripe for a catalyst that would disrupt this unstable family situation. It came in the form of a letter. After almost a year of silence, Elsa Einstein wrote to her cousin.
The previous May, when he had declared that he was writing her “for the last time,” Einstein had nonetheless given her the address of what would be his new office in Zurich. Now Elsa decided to send him a greeting for his thirty-fourth birthday, and she added a request for a picture of him and a recommendation of a good book she could read on relativity. She knew how to flatter.55
“There is no book on relativity that is comprehensible to the layman,” he replied. “But what do you have a relativity cousin for? If you ever happen to be in Zurich, then we (without my wife, who is unfortunately very jealous) will take a nice walk, and I will tell you about all of those curious things that I discovered.” Then he went a bit further. Instead of sending a picture, wouldn’t it be better to see each other in person? “If you wish to make me truly happy, then arrange to spend a few days here sometime.”56
A few days later, he wrote again, with word that he had instructed a photographer to send her a picture. He had been working on generalizing his theory of relativity, he reported, and it was exhausting. As he had a year earlier, he complained about being married to Mari: “What I wouldn’t give to be able to spend a few days with you, but without my cross!” He asked Elsa if she would be in Berlin later that summer. “I would like to come for a short visit.”57
It was therefore not surprising that Einstein was very receptive, a few months later, when the two towers of Berlin’s scientific establishment—Max Planck and Walther Nernst—came to Zurich with an enticing proposal. Having been impressed by Einstein at the Solvay Conference of 1911, they had already been sounding out colleagues about getting him to Berlin.
The offer they brought with them, when they arrived with their wives on the night train from Berlin on July 11, 1913, had three impressive components: Einstein would be elected to a coveted vacancy in the Prussian Academy of Sciences, which would come with a hefty stipend; he would become the director of a new physics institute; and he would be made a professor at the University of Berlin. The package included a lot of money, and it was not nearly as much work as it may have seemed on the surface. Planck and Nernst made it clear that Einstein would have no required teaching duties at the university and no real administrative tasks at the institute. And though he would be required to accept German citizenship once again, he could keep his Swiss citizenship as well.
The visitors made their case during a long visit to Einstein’s sunny office at the Polytechnic. He said he needed a few hours to think it over, though it is likely he knew he would accept. So Planck and Nernst took their wives on an excursion by funicular railway up one of the nearby mountains. With puckish amusement, Einstein told them he would be awaiting their return to the station with a signal. If he had decided to decline, he would be carrying a white rose, and if he was going to accept, a red rose (some accounts have the signal being a white handkerchief). When they stepped off the train, they happily discovered that he had accepted.58
That meant that Einstein would become, at 34, the youngest member of the Prussian Academy. But first Planck had to get him elected. The letter he wrote, which was also signed by Nernst and others, had the memorable but incorrect concession, quoted earlier, that “he might sometimes have overshot the target in his speculations, as for example in his light quantum hypothesis.” But the rest of the letter was suffused with extravagant praise for each of his many scientific contributions. “Among the great problems abundant in modern physics, there is hardly one to which Einstein has not made a remarkable contribution.”59
The Berliners were
taking a risk, Einstein realized. He was being recruited not for his teaching skills (as he would not be teaching), nor for his administrative ones. And even though he had been publishing outlines and papers describing his ongoing efforts to generalize relativity, it was unclear whether he would succeed in that quest. “The Germans are gambling on me as they would on a prize-winning hen,” he told a friend as they were leaving a party, “but I don’t know if I can still lay eggs.”60
Einstein, likewise, was taking a risk. He had a secure and lucrative post in a city and society that he, his wife, and his family loved. The Swiss personality agreed with him. His wife had a Slav’s revulsion for all things Teutonic, and he had a similar distaste that had been in-grained in childhood. As a boy he had run away from Prussian-accented parades and Germanic rigidity. Only the opportunity to be gloriously coddled in the world capital of science could have compelled him to make such a move.
Einstein found the prospect thrilling and a bit amusing. “I am going to Berlin as an Academy-man without any obligations, rather like a living mummy,” he wrote fellow physicist Jakob Laub. “I’m already looking forward to this difficult career!”61 To Ehrenfest he admitted, “I accepted this odd sinecure because giving lectures gets on my nerves.”62 However, to the venerable Hendrik Lorentz in Holland Einstein displayed more gravitas: “I could not resist the temptation to accept a position in which I am relieved of all responsibilities so that I can give myself over completely to rumination.”63
There was, of course, another factor that made the new job enticing: the chance to be with his cousin and new love, Elsa. As he would later admit to his friend Zangger, “She was the main reason for my going to Berlin, you know.”64
The same evening that Planck and Nernst left Zurich, Einstein wrote Elsa an excited letter describing the “colossal honor” they had offered. “Next spring at the latest, I’ll come to Berlin for good,” he exulted. “I already rejoice at the wonderful times we will spend together!”
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