I could preface this question with three pages of posts, but I'll just put it out there and see what shakes lose. Put two flashlights (torches, lasers, whatever) butt to butt. Then send out two light beams in opposite directions. How fast, realitive to each other, are those light beams traveling? If you picked one photon from Beam West and one photon Beam East and determined their relative velocity, what velocity would that be?