Albert struck up a relationship with Elsa on that trip. He was still married to Mileva; at the time I believe they were living in Prague. There was an intense correspondence for a few months and then Albert broke it off, and about a year later on his birthday Elsa wrote again and there was evidence that there was some sort of fracas between them. Maybe Mileva intercepted the correspondence. Shortly after that Albert was recruited by Max Planck. Basically the Germans decided that this quantum theory that Einstein had been pushing for the last ten years was really hot stuff and could help German industry rule the world, and they were ready to put a lot of money into it, and they made him an offer he couldn't refuse to go to Berlin. Einstein was sick of teaching. This was a job for more money and no students. It was everything he wanted except he had to move back to Germany. But Elsa was there, and there's even some evidence that she helped things along on the German end.

Einstein moved to Berlin in the spring of 1914, and things got very nasty between him and Mileva as soon as she arrived as he was running around with Elsa. By then Einstein started working on his general theory of relativity. He had a germ of an idea in 1907, but it started consuming him in 1911 or 1912, and once he moved to Berlin, that was pretty much all he did for the next couple of years. He lived in a bachelor pad downtown which was described as a place just littered with papers. One of his friends described his working habits as follows: he works until you drag him away, then you give him some food, he eats until it's gone, you put him in bed, he sleeps until you wake him up, and then it all starts all over again. He was completely obsessed.

EDGE: Obsessed with work?

OVERBYE: Elsa was there too.

EDGE: How did their relationship play out?

OVERBYE: Just before Mileva left, Albert and Mileva and one of Albert's friends and lawyer met, and they arranged a separation agreement. Elsa, who didn't want to be around, had left town during this period, but he went home to her house after that meeting and slept in her bed. Then Elsa started putting the screws on him to get married and to finalize his divorce with Mileva. Of course he had told Mileva when they split up that he would never marry again and he wasn't going to marry Elsa. But he eventually got dragged into it. It took Mileva a long time to agree to a divorce, and there were many stormy scenes. The war was dragging on; Einstein finished general relativity, towards the end of 1915. Mileva had a physical breakdown in the spring of 1916 right after Easter, probably after Albert had been there and told her he wanted a divorce.

That winter Albert got sick, he thought he had cancer, then he seemed to have had some sort of gall bladder problem, but he was on his back for months. They moved him into an apartment across the hall from Elsa; at this point he was effectively living with Elsa and her two daughters, who were around 18 and 20. It was clear that they were eventually going to get married.

They did get married, in 1919, but not before Albert had temporarily decided that he would rather marry one of Elsa's daughters, Ilse. All we know about this is that Ilse wrote a letter to her friend Georg Nicolai and said, help, what do I do here? She was not attracted to Albert she loved him as a father, and she had the good sense not to get involved. But it was Albert's Woody Allen moment.

He did marry Elsa, in 1919, and the marriage went on until 1936 when Elsa died. During the 1920s Albert had lots of affairs in Berlin — he was carrying on with a number of different women. Elsa was not happy with this, but she more or less decided she had made her deal. After she died Albert once made some comment about how his wife didn't know anything about physics. Unfortunately this had not been the case with his first wife.

EDGE: Do you have any notions about how these relationships with women affected his world view or changed his temperament?

OVERBYE: I know lots of people like Albert. I might be like him myself. He was a hopeless romantic, he lived on anticipation. He was always yearning for the next thing. He was always envisioning some wonderful life with somebody else, while grimly enduring life with the woman he was with. If I think about it, I would say that that was kind of the key to his psychology, that he had the lure of the perfect situation, the perfect person. Of course if you're Einstein, you want everything that you want your way and then you want to be left alone. So you want love, and you want affection, you want a good meal, but then you don't want any interference outside of that, so you don't want any obligations interfering with your life, with your work. Which is a difficult stance to maintain in an adult relationship; it doesn't work. Everything has to be a give and take.

Einstein always felt Paradise was just around the corner, but as soon as he got there, it started looking a little shabby and something better appeared. I've known a lot of people like Albert in my time, I have felt lots of shocks of recognition. I feel like I got to know Albert as a person in the course of this, and I have more respect for him as a physicist than I did when I started, I have more a sense of what he accomplished and how hard it really was to be Einstein than I did before. It's a great relief to be able to think of him as a real person. If he was around I'd love to buy him a beer ..... but I don't know if I'd introduce him to my sister.