Farsight, the way you are using the term, active gravitational mass, is the issue. Most of your comments above represent theoretical explanations not proven facts. Take the issue of energy and gravity. That has not been proven, though from what we observe it fits, with our currently best theoretical models, and is a necessary conclusion. The fact that it fits with theory does not make it so. Yet you constantly state it and other assumptions, as if they were fact! Almost everything in most of these discussions is theoretical! It is how we have come to believe the universe works. Our best theories work well at describing and predicting, but they remain theories. Yes theoretically energy, other than the inherent energy associated with massive objects, contributes to a gravitational field and that conclusion has sound basis in our theoretical interpretation of what we observe and understand to the universe... But it remains theoretical. It is my belief that photons play a role in what we experience as gravitation, but it does not seem reasonable to me, to extend to individual photons, a gravitational field of any kind. To do so would suggest that individual photons would interact gravitationally. Perhaps not when traveling through the relatively strong gravitational fields of massive objects, but certainly in the vast distances between galaxies where the active gravitational potential of those galaxies would be insignificant. Other than in theoretical contexts, photons do not interact directly with each other. If they did we would be unable to make any sense of what we observe of the distant universe. The picture would have become to distorted by photon gravitational interaction. Even small disturbances over the distances and time frames involved would blur the picture beyond reconstruction. As for your insistence that I go look up anything that you have failed to provide credible evidence of... Prove it yourself!