Since the curvature of spacetime in our Hubble sphere is zero (flat), or as close to as it gets, GR is our main concern.
Yes...SR is considered a local theory, whereas GR is a global theory.
Here's a little conundrum for you....according to Einstein, gravity is nothing more than the curvature of space due to the presence of matter. But how is that matter curving spacetime and producing gravity??
