**Gregorio Ricci** (also known as Gregorio Ricci-Corbastro) (January 12, 1853 to Aug 6, 1925) Ricci was an Italian mathematician whose most notable achievement was developing, in collaboration with Tullio Levi-Civita, the field of tensor calculus, which is a generalization of vector calculus and important in many branches of physics and in engineering. Tensor calculus is particularly important for the formulation of the General Theory of Relativity (Einstein’s theory of gravity). The Ricci curvature tensor *R _{μν}* and the Ricci scalar curvature

*R*are named after him. These appear in Einstein’s Equations for the gravitational field, which are written

_{ }** ***R _{μν}* – ½

*R g*+

_{μν}*Λ*

*g*= 8πG/c

_{μν}^{4}

*T*

_{μν}where *g _{μν}* is the metric tensor,

*Λ*is the cosmological constant,

*G*is Newton's gravitational constant,

*c*is the speed of light in vacuum, and

*T*is the stress-energy tensor. Ricci’s Catholic faith is reflected in this excerpt from his spiritual testament:

_{μν}“Only in the faith of Christ and in the Gospels have I found comfort in the troubles of life and a sure guide to lead me in life itself. Only the faith of Christ can give a satisfactory answer to those questions that are imposed even on those who do not want to know: Why are we in this world? What awaits us after this life, which, even when long, ends so soon? And how must we conduct ourselves to achieve the end for which we were created.”