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; in 1986, as a key member of the Rogers Commission, he investigated the Space Shuttle Challenger disaster and identified its cause; in 1965, he and two colleagues were awarded the Nobel Prize “for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles.” He was also an incredibly likeable character, and made countless other advances in his field, the complexities of which I will never be able understand.

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