Richard Feynman was one of the best-known and most influential physicists of his generation. In the 1940s, he played a part in the development of the atomic bomb. He won a Novel Prize for his contribution to science, and was also incredibly well-liked.

In June of 1945, his wife and high-school sweetheart, Arline, passed away from tuberculosis. She was 25-years-old. 16 months later, in October of 1946, Richard wrote his her a heartbreaking love letter and sealed it in an envelope. It remained unopened until after his death in 1988.

Opening his letter, "D'Arlene, I adore you, sweetheart," Feynman writes of how she is worth more, in his mind, than anyone else in the world, and of how - while he has tried to meet other women - none of them compare to her. "You dead are so much better than anyone else alive," he writes, and: "I find it hard to understand in my mind what it means to love you after you are dead, but I still want to comfort and take care of you."

Feynman ends his letter with a knowing post script, saying: "please excuse my not mailing this, but I don't know your new address."

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