Einstein

The Einstein & Levi-Civita correspondence was an exchange of letters in 1915 in which the mathematician Tullio Levi-Civita pointed out a mathematical error in Albert Einstein's work on general relativity, leading to a friendship and mutual respect despite technical criticism. This correspondence was crucial to the development of the theory and was characterized by Einstein's admiration for Levi-Civita's method and his ability to communicate in Italian, the language Levi-Civita used to write to Einstein.  The latter, though wrote in Geman... Except for the postcard below: