around to tell us what to do!”
Most of all, he tried to be reassuring. He would find a job, he pledged, even if it meant going into the insurance business. They would create a comfortable home together. “Be happy and don’t fret, darling. I won’t leave you and will bring everything to a happy conclusion. You just have to be patient! You will see that my arms are not so bad to rest in, even if things are beginning a little awkwardly.”35
Mari was preparing to retake her graduation exams, and she was hoping to go on to get a doctorate and become a physicist. Both she and her parents had invested enormous amounts, emotionally and financially, in that goal over the years. She could have, if she had wished, terminated her pregnancy. Zurich was then a center of a burgeoning birth control industry, which included a mail-order abortion drug firm based there.
Instead, she decided that she wanted to have Einstein’s child—even though he was not yet ready or willing to marry her. Having a child out of wedlock was rebellious, given their upbringings, but not uncommon. The official statistics for Zurich in 1901 show that 12 percent of births were illegitimate. Residents who were Austro-Hungarian, moreover, were much more likely to get pregnant while unmarried. In southern Hungary, 33 percent of births were illegitimate. Serbs had the highest rate of illegitimate births, Jews by far the lowest.36
The decision caused Einstein to focus on the future. “I will look for a position
The pregnancy could also resolve, or so he hoped, the issues they faced with their families. “When your parents and mine are presented with a fait accompli, they’ll just have to reconcile themselves to it as best they can.”37
Mari, bedridden in Zurich with pregnancy sickness, was thrilled. “So, sweetheart, you want to look for a job immediately? And have me move in with you!” It was a vague proposal, but she immediately pronounced herself “happy” to agree. “Of course it mustn’t involve accepting a really bad position, darling,” she added. “That would make me feel terrible.” At her sister’s suggestion she tried to convince Einstein to visit her parents in Serbia for the summer vacation. “It would make me so happy,” she begged. “And when my parents see the two of us physically in front of them, all their doubts will evaporate.”38
But Einstein, to her dismay, decided to spend the summer vacation again with his mother and sister in the Alps. As a result, he was not there to help and encourage her at the end of July 1901 when she re-took her exams. Perhaps as a consequence of her pregnancy and personal situation, Mileva ended up failing for the second time, once again getting a 4.0 out of 6 and once again being the only one in her group not to pass.
Thus it was that Mileva Mari found herself resigned to giving up her dream of being a scientific scholar. She visited her home in Serbia—alone—and told her parents about her academic failure and her pregnancy. Before leaving, she asked Einstein to send her father a letter describing their plans and, presumably, pledging to marry her. “Will you send me the letter so I can see what you’ve written?” she asked. “By and by I’ll give him the necessary information, the unpleasant news as well.”39
Einstein’s impudence and contempt for convention, traits that were abetted by Mari, were evident in his science as well as in his personal life in 1901. That year, the unemployed enthusiast engaged in a series of tangles with academic authorities.
The squabbles show that Einstein had no qualms about challenging those in power. In fact, it seemed to infuse him with glee. As he proclaimed to Jost Winteler in the midst of his disputes that year, “Blind respect for authority is the greatest enemy of truth.” It would prove a worthy credo, one suitable for being carved on his coat of arms if he had ever wanted such a thing.
His struggles that year also reveal something more subtle about Einstein’s scientific thinking: he had an urge— indeed, a compulsion—to unify concepts from different branches of physics. “It is a glorious feeling to discover the unity of a set of phenomena that seem at first to be completely separate,” he wrote to his friend Grossmann as he embarked that spring on an attempt to tie his work on capillarity to Boltzmann’s theory of gases. That sentence, more than any other, sums up the faith that underlay Einstein’s scientific mission, from his first paper until his last scribbled field equations, guiding him with the same sure sense that was displayed by the needle of his childhood compass.40
Among the potentially unifying concepts that were mesmerizing Einstein, and much of the physics world, were those that sprang from kinetic theory, which had been developed in the late nineteenth century by applying the principles of mechanics to phenomena such as heat transfer and the behavior of gases. This involved regarding a gas, for example, as a collection of a huge number of tiny particles—in this case, molecules made up of one or more atoms—that careen around freely and occasionally collide with one another.
Kinetic theory spurred the growth of statistical mechanics, which describes the behavior of a large number of particles using statistical calculations. It was, of course, impossible to trace each molecule and each collision in a gas, but knowing the statistical behavior gave a workable theory of how billions of molecules behaved under varying conditions.
Scientists proceeded to apply these concepts not only to the behavior of gases, but also to phenomena that occurred in liquids and solids, including electrical conductivity and radiation. “The opportunity arose to apply the methods of the kinetic theory of gases to completely different branches of physics,” Einstein’s close friend Paul Ehrenfest, himself an expert in the field, later wrote.“Above all, the theory was applied to the motion of electrons in metals, to the Brownian motion of microscopically small particles in suspensions, and to the theory of blackbody radiation.”41
Although many scientists were using atomism to explore their own specialties, for Einstein it was a way to make connections, and develop unifying theories, between a variety of disciplines. In April 1901, for example, he adapted the molecular theories he had used to explain the capillary effect in liquids and applied them to the diffusion of gas molecules. “I’ve got an extremely lucky idea, which will make it possible to apply our theory of molecular forces to gases as well,” he wrote Mari. To Grossmann he noted, “I am now convinced that my theory of atomic attractive forces can also be extended to gases.”42
Next he became interested in the conduction of heat and electricity, which led him to study Paul Drude’s electron theory of metals. As the Einstein scholar Jurgen Renn notes, “Drude’s electron theory and Boltzmann’s kinetic theory of gas do not just happen to be two arbitrary subjects of interest to Einstein, but rather they share an important common property with several other of his early research topics: they are two examples of the application of atomistic ideas to physical and chemical problems.”43
Drude’s electron theory posited that there are particles in metal that move freely, as molecules of gas do, and thereby conduct both heat and electricity. When Einstein looked into it, he was pleased with it in parts. “I have a study in my hands by Paul Drude on the electron theory, which is written to my heart’s desire, even though it
