An introduction to the conceptual and mathematical framework of Einstein's General Theory of Relativity. We begin by considering the key insight of gravity as a geometric phenomenon, and how the curvature of spacetime by matter explains the equality of inertial and gravitational mass. We then discuss the mathematics of general relativity, including geodesics, differential manifolds, covariant derivatives, the metric tensor, Christoffel symbols, the Riemann curvature tensor, the Ricci tensor, and the energy-momentum tensor. The episode concludes with a derivation and explanation of the significance of Einstein's Field Equations. Recommended pre-listening is Episodes 114 and 115: Special Relativity 1 and 2. 
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