Summary.

The conclusions to be drawn from all these arguments are,

• All frames of reference are equivalent, provided we are willing to include possible gravitational effects (in non-inertial or accelerated frames forces will appear which are indistinguishable from gravitational forces).
• Space-time is a dynamic object: matter curves it, and the way in which it is curved determines the motion of matter in it. Since all bodies are affected in the same way by the curvature of space and time the effects of gravity are independent of the nature of the body. Changes in the distribution of matter change space-time deforming it, and, in some instances, making it oscillate.