Does relativity work for a coordinate system traveling with a light photon? Lets see, if the observer is traveling with a photon then the universe is Lorenz contracted into a two dimensional plane perpendicular to the direction of the photon velocity vector. All mass objects would have infinite relativistic mass, however photons have only relativistic mass which does not exist perpendicular to the direction of motion so the universal plane would have no gravitational affect on a rest massless photon. All matter at rest in our coordinate system must exist as photons as that is the only thing known to travel at the speed of light. Other photons could move toward and away from the coordinate photon in the universal plane as the photon crosses the universe but no time passes for the coordinate photon. So other photons must exist at all positions it has in time in the universal plane simultaneously. Or other photons, however, must travel at the speed of light, regardless? That’s it!! my brain is fried.