Hey guys, in classical mechanics Newton's law of universal gravitationa force says that the force between two bodies is equal to the product of their masses divided by the square root of the distance between them. So far, so good. In SR, lengths depend on the frame that we are in, and so the parameter 'r' (distance) varies between frame to frame and therefore that implies that the gravitational force varies from frame to frame. This fact should also imply that the acceleration which a body undergoes because of gravity varies from frame to frame. Is this valid reasoning, and could somebody help me with the maths? The basic question is can Newton's law of gravity be compatible with SR. Regards, analyst.