Einstein was a con-artist but the math apparatus developed by his controllers was still very impressive.

Especially, it includes a way to mathematically define the existence of curvature of a surface.

The method, which is explained in this video, is based on parallel-translation of a vector around a curve of the surface examined.

https://youtu.be/foRPKAKZWx8?t=4353 I recommend watching from start if you are not already familiar with tensor math.

Now, if you end up with the vector …