““It sometimes happens that mathematical methods conceived in the abstract turn out later to be so well suited to a particular application that they might have been written especially for it. When he was wrestling with the problems of general relativity, Albert Einstein came across the tensor calculus, invented 50 years earlier by Curbastro Gregorio Ricci and Tullio Levi-Civita, and saw that it was exactly what he needed. James enlisted a method that had been created in the mid-eighteenth century by Joseph-Louis Lagrange.””
![“Einstein, my upset stomach hates your theory [of General Relativity]—it…” quote by Paul Ehrenfest](https://sms4smile.com/quotes/img-quotes/8bf/paul-ehrenfest-52330_answers_einstein-my-upset-stomach-hates-your-the_467759.jpg)
