>>7784195
Tensor Calc
Smooth Manifolds
Riemannian Geometry

Also being good at working with PDEs is useful considering almost everything you study in GR revolves around EFEs and their solutions.

light goes woo when gravity goes woooo and then your get compressed like wo and then you throw a baseball out of a car like weee

Why would you waste time on that? In general relativity gravity doesn't change from the Newton's law to bended space. It is both.

>>7784227
What?

so how does one determine which way to orient the spatial felt?

Between two systems the answer seems obvious: set the horizontal so that both systems are given influence proportional to their mass. Same could be said about 3 systems, just create a plan that encompasses them.

But what about 4+?

>>7784230
That pic of yours sucks ass. It doesn't sescribe gravity wholly.

>>7784195
Matrix Algebra
Vector Calculus
Modern Geometry
Differential Geometry of Curves and Surfaces
Proofs and Abstract Math
Real Mathematical Analysis
Tensors and Differential Forms
Smooth Manifolds
Riemann Geometry