interesting thought. The key seems to be in movement, linear and rotational. If I recall correctly, if any mass accelerates fast enough, it turns into pure energy, which is mass-less, but "moving" or transmitted. Im still wondering if energy, such as photons, can warp spacetime, or only be warped by a mass. Thought experiment - if everything in the cosmos came to a stand still, would anything exist? Does the cosmos exist only because all parts of it (mass and energy) move. Thoughts?Spacetime is reality. My guess is that the fabric of spacetime is made of virtual mass.