Recently, in my research, a question has arisen about the modification of the scattering frequency of a photon by a population of electrons, if those electrons are flowing at a considerable fraction of the speed of light. Intuitively, to me, it seems that if a photon is directed into a population of electrons which are flowing in the same direction as the photon, the photon will travel a greater distance and for a greater time before its first scattering event than if the population was static. Conversely, it seems reasonable that if the electrons are flowing in the opposite direction as the photon, the photon will scatter in a shorter distance and sooner. My feeling in this matter is based, of course, on the fact that over a given distance traveled, the photon would pass more or less electrons than the static case. These situations would depend on the fact that the densities observed in the lab frame are the same, regardless of the bulk flow direction. I'm aware that in the electrons' rest frame, the photon still travels at the speed of light - however, my intuition says that the geometry in that frame would be modified to reflect the above effect. I'm aware that the electron cross-section would be modified based on head-on or tail-on collisions, but am not concerned with that issue at the moment. I'd be happy to hear thoughts on that matter as well, however. I'd love to hear your thoughts and reasoning concerning these problems.