I was wondering two hings. First, does light's energy equate to mass and result in the bending of space time? The fact that it does follow the curve of space-time as well as mass-energy equivalence principle lead me to believe it would. Secondly, was that energy accounted for in calculating the mass of the universe(or whatever we did to figure there was dark matter)? Because that seems like it would be quite a few photons of really small energy that would add up to alot of energy centered around where the most photon-emitting objects were. and sort of extra: Thirdly, could the effects of gravity not cause enough loss of energy in photons traveling for such great distances to shorten their wavelengths and cause redshift, I didn't think we expected a constant energy level in anything else, why light, it should lose energy over time like anything else.... eventually causing redshift and the farther away the object the more it would be red-shifted?