Synge once said, use space and time, and define them.

This post is aimed to make clear what frame are we in.

In general relavity, many theorems provides deep understanding of gravity.

Documents for modified gravity theories.

This post lists the experiments which are used to test gravity theories carried out on the earth.

This is a post for cosmic background radiation surveys.

Galaxy surveys is a powerful way of exploring the large scale structure of the universe, as well as a way of testing the theory of gravity.