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On Nov. 18, Einstein received Hilbert's new paper. Einstein was dismayed to see how similar it was to his own work. His response to Hilbert was terse and clearly designed to assert the priority of his own work. "The system you furnish agrees--as far as I can see--exactly with what I found in the last few weeks and have presented to the Academy," he wrote.
Hilbert responded kindly and quite generously the following day, claiming no priority for himself. "If I could calculate as rapidly as you," he wrote, "in my equations the electron would have to capitulate and the hydrogen atom would have to produce its note of apology about why it does not radiate." Yet one day later, Hilbert sent a paper to a scientific journal with his own version of the equations for general relativity. The title he picked for his piece was not a modest one. "The Foundations of Physics," he called it.
Einstein's climactic fourth lecture at the Prussian Academy, on Nov. 25, was titled "The Field Equations of Gravitation." It contained the correct set of equations that capped his theory of general relativity. Although it came a few days after Hilbert had sent in his own paper, Einstein's version was more complete, and the underlying concepts were his alone.
The theory was one of history's most imaginative and dramatic revisions of our concepts about the universe. It was, said Paul Dirac, the Nobel laureate pioneer of quantum mechanics, "probably the greatest scientific discovery ever made." Max Born, another giant of 20th century physics, called it "the greatest feat of human thinking about nature, the most amazing combination of philosophical penetration, physical intuition and mathematical skill."
Nevertheless, Einstein's triumph was tempered by his continued struggles with Hans Albert. The boy told a family friend that he wanted to spend the entire Christmas vacation hiking with his father, but he wrote a chilly letter to his father indicating the opposite: Dear Papa, I will come over New Year's, i.e., from the 31st to 2nd. I don't want to stay longer because Christmas is nicest at home. Besides, I got skis and would like to learn how to use them with my colleagues. The ski equipment costs about 70 francs, and Mama bought them for me on condition that you also contribute. I consider them a Christmas present. Yours, Adu So Einstein informed his son that he was canceling the trip. "The unkind tone of your letter dismays me very much," he wrote just days after finishing his last lecture on general relativity. "I see that my visit would bring you little joy, therefore I think it's wrong to sit in a train for two hours and 20 minutes."
There was also the question of paying for the skis. Einstein was not pleased. He replied that he would send Hans Albert a gift in cash, "but I do think that a luxury gift costing 70 francs does not match our modest circumstances," he wrote, underlining the phrase.