Me and my Dad were having a conversation about the elongation of EMR wavelengths over an extended period of time. He began to explain to me what Red Shift was but I couldn't understand what he was trying to get at (he's a poor explainer, or I'm bad listener). But his explanation did spark an idea I had that goes like this: Since light is affected by gravity and also must maintain its velocity constancy, to overcome gravitational effects energy must be given up. In doing so, it must also elongate its wavelength. Over time, these gravitational effects from surrounding bodies would lower the energy of the photon. I asked him if that was Red Shift and he said no. So what is Red Shift, and much of a role does it play compared to the phenomena explained above?