Albert Einstein thought he had made the breakthrough of his career and wrote a letter to his son sharing the news. It turned out not to be so. But in his letter, the physicist took a rare moment to reflect on his life's work and offered a glimpse into his fond relationship with his son. The one-page handwritten letter is being auctioned this week by Boston's RR Auction. It could fetch more than $100,000, company officials said. In the letter, which is estimated to be from 1929, Einstein tells his son, Eduard Einstein, that he has made a major discovery, the AP reports. "Einstein does not usually talk about his life's work—that's what makes the letter spectacular," an exec at the auction house says.
"I am now very happy because I finally solved to my total satisfaction ... my gravitation-electricity problem," he wrote, according to a translation of the German letter. "This, in a way, concludes my life's work—the remainder simply is bonus material." The letter also depicts Einstein as a caring father to Eduard, who was finishing high school at the time. He writes about a "deep inner kinship" between them. "It seems to me it has been so long since I have seen you, and I am longing to have you around me once again," Einstein wrote. Eduard was later diagnosed with schizophrenia and had his first breakdown in 1930. He went on to live much of his life in psychiatric institutions. (Read more Albert Einstein stories.)