During the ensuing week, he sent two more such notes. “I rejoice at the thought that I will soon be coming to you,” he wrote in the first. And a few days later: “Now we will be together and rejoice in each other!” It is impossible to know for sure what relative weight to assign to each of the factors enticing him to Berlin: the unsurpassed scientific community there, the glories and perks of the post he was offered, or the chance to be with Elsa. But at least to her he claimed it was primarily the latter. “I look forward keenly to Berlin, mainly because I look forward to you.”65
Elsa had actually tried to help him get the offer. Earlier in the year, on her own initiative, she had dropped in on Fritz Haber, who ran the Kaiser Wilhelm Institute of Chemistry in Berlin, and let him know that her cousin might be open to a position that would bring him to Berlin. When he learned of Elsa’s intervention, Einstein was amused. “Haber knows who he is dealing with. He knows how to appreciate the influence of a friendly female cousin . . . The nonchalance with which you dropped in on Haber is pure Elsa. Did you tell anyone about it, or did you consult only with your wicked heart? If only I could have looked on!”66
Even before Einstein moved to Berlin, he and Elsa began to correspond as if they were a couple. She worried about his exhaustion and sent him a long letter prescribing more exercise, rest, and a healthier diet. He responded by saying that he planned to “smoke like a chimney, work like a horse, eat without thinking, go for a walk only in really pleasant company.”
He made clear, however, that she should not expect him to abandon his wife: “You and I can very well be happy with each other without her having to be hurt.”67
Indeed, even amid his flurry of love letters with Elsa, Einstein was still trying to be a suitable family man. For his August 1913 vacation, he decided to take his wife and two sons hiking with Marie Curie and her two daughters. The plan was to go through the mountains of southeastern Switzerland down to Lake Como, where he and Mari had spent their most passionate and romantic moments twelve years earlier.
As it turned out, the sickly Eduard was unable to make the trip, and Mari stayed behind for a few days to get him settled with friends. Then she joined them as they neared Lake Como. During the hikes, Curie challenged Einstein to name all the peaks. They also talked science, especially when the children ran ahead. At one point Einstein stopped suddenly and grabbed Curie’s arm. “You understand, what I need to know is exactly what happens to the passengers in an elevator when it falls into emptiness,” he said, referring to his ideas about the equivalence of gravity and acceleration. As Curie’s daughter noted later, “Such a touching preoccupation made the younger generation roar with laughter.”68
Einstein then accompanied Mari and their children to visit her family in Novi Sad and at their summer house in Ka. On their final Sunday in Serbia, Mari took the children, without her husband, to be baptized. Hans Albert remembered later the beautiful singing; his brother, Eduard, only 3, was disruptive. As for their father, he seemed sanguine and bemused afterward. “Do you know what the result is?” he told Hurwitz.“They’ve turned Catholic. Well, it’s all the same to me.”69
The façade of familial harmony, however, masked the deterioration of the marriage. After his visit to Serbia and a stop in Vienna for his annual appearance at the conference of German-speaking physicists, Einstein continued on to Berlin, alone. There he was reunited with Elsa. “I now have someone I can think about with pure delight and I can live for,” he told her.70
Elsa’s home cooking, a hearty pleasure she lavished on him like a mother, became a theme in their letters. Their correspondence, like their relationship, was a stark contrast to that between Einstein and Mari a dozen years earlier. He and Elsa tended to write to each other about domestic comforts—food, tranquillity, hygiene, fondness—rather than about romantic bliss and planted kisses, or intimacies of the soul and insights of the intellect.
Despite such conventional concerns, Einstein still fancied their relationship could avoid sinking into a mundane pattern. “How nice it would be if one of these days we could share in managing a small bohemian household,” he wrote. “You have no idea how charming such a life with very small needs and without grandeur can be!”71 When Elsa gave him a hairbrush, he initially prided himself on his progress in personal grooming, but then he reverted to more slovenly ways and told her, only half jokingly, that it was to guard against the philistines and the bourgeoisie. Those were words he had used with Mari as well, but more earnestly.
Elsa wanted not only to domesticate Einstein but to marry him. Even before he moved to Berlin, she wrote to urge him to divorce Mari. It would become a running battle for years, until she finally won her way. But for the moment, Einstein was resistant. “Do you think,” he asked her, “it is so easy to get a divorce if one does not have any proof of the other party’s guilt?” She should accept that he had virtually separated from Mari even if he was not going to divorce her. “I treat my wife as an employee whom I cannot fire. I have my own bedroom and avoid being alone with her.” Elsa was upset that Einstein did not want to marry her, and she was fearful of how an illicit relationship would affect her daughters, but Einstein insisted it was for the best.72
Mari was understandably depressed by the prospect of moving to Berlin. There she would have to deal with Einstein’s mother, who had never liked her, and his cousin, whom she rightly suspected of being a rival. In addition, Berlin had sometimes been less tolerant to Slavs than it was even to Jews. “My wife whines to me incessantly about Berlin and her fear of the relatives,” Einstein wrote Elsa. “Well, there is some truth in this.” In another letter, when he noted that Mari was afraid of her, he added, “Rightly so I hope!”73
Indeed, by this point all of the women in his life—his mother, sister, wife, and kissing cousin—were at war with one another. As Christmas 1913 neared, Einstein’s struggle to generalize relativity had the added benefit of being a way to avoid family emotions. The effort produced yet another eloquent restatement of how science could rescue him from the merely personal. “The love of science thrives under these circumstances,” he told Elsa, “for it lifts me impersonally from the vale of tears into peaceful spheres.”74
With the approach of the spring of 1914 and their move to Berlin, Eduard came down with an ear infection that made it necessary for Mari to take him to an Alpine resort to recover. “This has a good side,” Einstein told Elsa. He would initially be traveling to Berlin alone, and “in order to savor that,” he decided to skip a conference in Paris so that he could arrive earlier.
On one of their last evenings in Zurich, he and Mari went to the Hurwitz house for a farewell musical evening. Once again, the program featured Schumann, in an attempt to cheer her up. It didn’t. She instead sat by herself in a corner and did not speak to anyone.75
Berlin, 1914
By April 1914, Einstein had settled into a spacious apartment just west of Berlin’s city center. Mari had picked it out when she visited Berlin over Christmas vacation, and she arrived in late April, after Eduard’s ear infection had subsided.76
The tensions in Einstein’s domestic life were exacerbated by overwork and mental strain. He was settling into a new job—actually three new jobs—and still struggling with his fitful attempts to generalize his theory of relativity and tie it into a theory of gravity. That first April in Berlin, for example, he engaged in an intense correspondence with Paul Ehrenfest over ways to calculate the forces affecting rotating electrons in a magnetic field. He started writing a theory for such situations, then realized it was wrong. “The angel had unveiled itself halfway in its magnificence,” he told Ehrenfest, “then on further unveiling a cloven hoof appeared and I ran away.”
Even more revealing, perhaps more than he meant it to be, was his comment to Ehrenfest about his personal life in Berlin.“I really delight in my local relatives,” he reported, “especially in a cousin of my age.”77
When Ehrenfest came for a visit at the end of April, Mari had just arrived,
and he found her gloomy and yearning for Zurich. Einstein, on the other hand, had thrown himself into his work. “He had the impression that the family was taking a bit too much of his time, and that he had the duty to concentrate completely on his work,” his son Hans Albert later recollected about that fateful spring of 1914.78
Personal relationships involve nature’s most mysterious forces. Outside judgments are easy to make and hard to verify. Einstein repeatedly and plaintively stressed to all of their mutual friends—especially the Bessos, Habers, and Zanggers—that they should try to see the breakup of his marriage from his perspective, despite his own apparent culpability.
It is probably true that he was not solely to blame. The decline of the marriage was a downward spiral. He had become emotionally withdrawn, Mari had become more depressed and dark, and each action reinforced the other. Einstein tended to avoid painful personal emotions by immersing himself in his work. Mari, for her part, was bitter about the collapse of her own dreams and increasingly resentful of her husband’s success. Her jealousy made her hostile toward anyone else who was close to Einstein, including his mother (the feeling was reciprocal) and his friends. Her mistrustful nature was, understandably, to some extent an effect of Einstein’s detachment, but it was also a cause.
By the time they moved to Berlin, Mari had developed at least one personal involvement of her own, with a mathematics professor in Zagreb named Vladimir Variak, who had challenged Einstein’s interpretations of how special relativity applied to a rotating disk. Einstein was aware of the situation. “He had a kind of relationship with my wife, which can’t be held against either of them,” he wrote to Zangger in June. “It only made me feel my sense of isolation doubly painfully.”79
The end came in July. Amid the turmoil, Mari moved with her two boys into the house of Fritz Haber, the chemist who’d recruited Einstein and who ran the institute where his office was located. Haber had his own experience with domestic discord. His wife, Clara, would end up committing suicide the following year after a fight over Haber’s participation in the war. But for the time being, she was Mileva Mari’s only friend in Berlin, and Fritz Haber became the intermediary as the Einsteins’ battles broke into the open.
Through the Habers, Einstein delivered to Mari in mid-July a brutal cease-fire ultimatum. It was in the form of a proposed contract, one in which Einstein’s cold scientific approach combined with his personal hostility and emotional alienation to produce an astonishing document. It read in full:
Conditions.
A. You will make sure
1. that my clothes and laundry are kept in good order;
2. that I will receive my three meals regularly in my room;
3. that my bedroom and study are kept neat, and especially that my desk is left for my use only.
B. You will renounce all personal relations with me insofar as they are not completely necessary for social reasons. Specifically, you will forego
1. my sitting at home with you;
2. my going out or traveling with you.
C. You will obey the following points in your relations with me:
1. you will not expect any intimacy from me, nor will you reproach me in any way;
2. you will stop talking to me if I request it;
3. you will leave my bedroom or study immediately without protest if I request it.
D. You will undertake not to belittle me in front of our children, either through words or behavior.80
Mari accepted the terms. When Haber delivered her response, Einstein insisted on writing to her again “so that you are completely clear about the situation.” He was prepared to live together again “because I don’t want to lose the children and I don’t want them to lose me.” It was out of the question that he would have a “friendly” relationship with her, but he would aim for a “businesslike” one. “The personal aspects must be reduced to a tiny remnant,” he said. “In return, I assure you of proper comportment on my part, such as I would exercise to any woman as a stranger.”81
Only then did Mari realize that the relationship was not salvageable. They all met at Haber’s house on a Friday to work out a separation agreement. It took three hours. Einstein agreed to provide Mari and his children 5,600 marks a year, just under half of his primary salary. Haber and Mari went to a lawyer to have the contract drawn up; Einstein did not accompany them, but instead sent his friend Michele Besso, who had come from Trieste to represent him.82
Einstein left the meeting at Haber’s house and went directly to the home of Elsa’s parents, who were also his aunt and uncle. They arrived home late from dinner to find him there, and they received the news about the situation with “a mild distaste.” Nevertheless, he ended up staying at their house. Elsa was on summer vacation in the Bavarian Alps with her two daughters, and Einstein wrote to inform her that he was now sleeping in her bed in the apartment upstairs. “It’s peculiar how confusingly sentimental one gets,” he told her. “It is just a bed like any other, as though you had never slept in it. And yet I find it comforting.” She had invited him to visit her in the Bavarian Alps, but he said he could not, “for fear of damaging your reputation again.”83
The way to a divorce had now been paved, he assured Elsa, and he called it “a sacrifice” he had made on her behalf. Mari would move back to Zurich and take custody of the two boys, and when they came to visit their father they could meet only on “neutral ground,” not in any house he shared with Elsa. “This is justified,” Einstein conceded to Elsa, “because it is not right to have the children see their father with a woman other than their own mother.”
The prospect of parting with his children was devastating for Einstein. He pretended to be detached from personal sentiments, and sometimes he was. But he became deeply emotional as he imagined life apart from his sons. “I would be a real monster if I felt any other way,” he wrote Elsa. “I have carried these children around innumerable times day and night, taken them out in their pram, played with them, romped around and joked with them. They used to shout with joy when I came; the little one cheered even now, because he was still too small to grasp the situation. Now they will be gone forever, and their image of their father is being spoiled.”84
Mari and the two boys left Berlin, accompanied by Michele Besso, aboard the morning train to Zurich on Wednesday, July 29, 1914. Haber went to the station with Einstein, who “bawled like a little boy” all afternoon and evening. It was the most wrenching personal moment for a man who took perverse pride in avoiding personal moments. For all of his reputation of being inured to deep human attachments, he had been madly in love with Mileva Mari and bonded to his children. For one of the few times in his adult life, he found himself crying.
The next day he went to visit his mother, who cheered him up. She had never liked Mari and was delighted that she was gone. “Oh, if your poor Papa had only lived to see it!” she said about the separation. She even professed herself pleased for Elsa, although they had occasionally clashed. And Elsa’s mother and father also seemed happy enough with the resolution, though they did express resentment that Einstein had been too financially generous to Mari, which meant the income left for him and Elsa might be “a bit meager.”85
The whole ordeal left Einstein so drained that, despite what he had said to Elsa just a week earlier, he decided that he was not prepared to get married again. Thus he would not have to force the issue of a legal divorce, which Mari fiercely resisted. Elsa, still on vacation, was “bitterly disappointed” by the news. Einstein sought to reassure her. “For me there is no other female creature besides you,” he wrote. “It is not a lack of true affection which scares me away again and again from marriage! Is it a fear of the comfortable life, of nice furniture, of the odium that I burden myself with or even of becoming some sort of contented bourgeois? I myself don’t know; but you will see that my attachment to you will endure.”
He insisted that she should not feel ashamed or let people pity her for consorting with a man who w
ould not marry her. They would take walks together and be there for each other. Should she choose to offer even more, he would be grateful. But by not marrying, they would be protecting themselves from lapsing into a “contented bourgeois” existence and preventing their relationship “from becoming banal and from growing pale.” To him, marriage was confining, which was a state he instinctively resisted. “I’m glad our delicate relationship does not have to founder on a provincial narrow-minded lifestyle.”86
In the old days, Mari had been the type of soul mate who responded to such bohemian sentiments. Elsa was not such a person. A comfortable life with comfortable furniture appealed to her. So did marriage. She would accept his decision not to get married for a while, but not forever.
In the meantime, Einstein became embroiled in a long-distance battle with Mari over money, furniture, and the way she was allegedly “poisoning” their children against him.87 And all around them, a chain reaction was taking Europe into the most incomprehensibly bloody war in its history.
Not surprisingly, Einstein reacted to all of this turmoil by throwing himself into his science.
CHAPTER NINE
GENERAL RELATIVITY
1911–1915
Light and Gravity
After Einstein formulated his special theory of relativity in 1905, he realized that it was incomplete in at least two ways. First, it held that no physical interaction can propagate faster than the speed of light; that conflicted with Newton’s theory of gravity, which conceived of gravity as a force that acted instantly between distant objects. Second, it applied only to constant-velocity motion. So for the next ten years, Einstein engaged in an interwoven effort to come up with a new field theory of gravity and to generalize his relativity theory so that it applied to accelerated motion.1
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