einstein

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 coordinate 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 energymomentum
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.