so i am somewhat new to the theory of general relativity but in none of the papers i have read does anyone seem to explain what causes matter to attract.... for example, the moon and the earth are attracted to each other because each of them warps spacetime around themselves. these warped pockets could be thought of as low density areas in spacetime. Einstein says they attract because they are following the curvature of spacetime but what drives that motion? the only thing i can think of that would cause objects to want to clump together in a spacetime feild is if spacetime is somehow elastic. it is as if for whatever reason there is a pressure-like force causing spacetime to want to return to a uniform distribution. is there a term for such a force and if so what causes it?