It is well-known that Einstein was notoriously bad at mathematics. The sole reason for the decade of delay between his 1905 Special Theory of Relativity and his

It is well-known that Einstein was notoriously bad at mathematics. The sole reason for the decade of delay between his 1905 Special Theory of Relativity and his 1915 General Theory of Relativity is that Einstein did not have the mathematics to calculate the formulas. He needed some of the work done by Hermann Minkowski. By 1908 Minkowski realized that the special theory of relativity, introduced by his former student Albert Einstein in 1905 and based on the previous work of Lorentz and Poincaré, could best be understood in a four-dimensional space, since known as the "Minkowski spacetime," in which time and space are not separated entities but intermingled in a four-dimensional space–time, and in which the Lorentz geometry of special relativity can be effectively represented using the invariant interval x^2 + y^2 + z^2 -c^2*t^2. So even the notion of space-time was not Einstein's idea. Although Einstein is credited with finding the field equations for General Relativity, the German mathematician David Hilbert published them in an article before Einstein's article. This has resulted in accusations of plagiarism against Einstein, although not from Hilbert, and assertions that the field equations should be called the "Einstein–Hilbert field equations". However, Hilbert did not press his claim for priority. Albert Einstein's friendship with Marcel Grossmann began with their school days in Zurich. Grossmann's careful and complete lecture notes at the Federal Polytechnic School proved to be a salvation for Einstein, who missed many lectures. Grossmann's father helped Einstein get his job at the Swiss Patent Office in Bern, and it was Grossmann who helped to conduct the negotiations to bring Einstein back from Prague as a professor of physics at the Zurich Polytechnic. Grossmann was an expert in differential geometry and tensor calculus; just the mathematical tools providing a proper mathematical framework for Einstein's work on gravity. Thus, it was natural that Einstein would enter into a scientific collaboration with Grossmann. It was mathemetician Marcel Grossmann who emphasized the importance of a non-Euclidean geometry called Riemannian geometry (also elliptic geometry) to Einstein, which was a necessary step in the development of Einstein's general theory of relativity. Abraham Pais's book on Einstein suggests that Grossmann mentored Einstein in tensor theory as well. Grossmann introduced Einstein to the absolute differential calculus, started by Christoffel and fully developed by Ricci-Curbastro and Levi-Civita. Grossmann facilitated Einstein's unique synthesis of mathematical and theoretical physics in what is still today considered the most elegant and powerful theory of gravity: the general theory of relativity. The collaboration of Einstein and Grossmann led to a ground-breaking paper: "Outline of a Generalized Theory of Relativity and of a Theory of Gravitation," which was published in 1913 and was one of the two fundamental papers which established Einstein's theory of gravity. continues in reply to my own comment...