From what I understand, Einstein basically scrapped the concept of gravity being a force and instead said that energy (and thereby mass) and momentum causes spacetime to curve. Objects still travel on geodesics in spacetime (Newton's first law), but since it is curved, the geodesics near massive objects are such that bodies following them look like they're attracted to the object. Since gravity is no longer a force, it cannot by definition do any work. Instead it seems as though work would be required to keep an object from following its spacetime geodesic - which would correspond to acceleration in the newtonian formulation. Thoughts?