Imagine a stream of photons moving from the sun to the earth (A, B, C, D, E, F, G, etc.). Now imagine 2 different men measuring the speed of the photons, and (somehow) recording which photon is hitting them. They are in the same position, but one is traveling 1/2 the speed of light (relative to the earth) toward the sun, and the other is travelling 1/2 the speed of light away from the sun. Say they are giving each other a high-five as they pass and doing the measurement at the same time that their hands slap. The question I want to ask, is which photon in the stream are each of the measuring? For the guy who is moving toward the sun, the photon-stream is moving towards him at the speed of light (but 1.5 the speed of light relative to the earth, since he's moving 1/2 the speed of light toward the sun). But for the guy moving away from the sun, the photon stream is moving toward him also at the speed of light, but only 1/2 the speed of light relative to the earth. Therefore, aren't they going to be measuring two totally different photons to be in the same place at the same time as they pass each other? Won't the first guy be measuring a much earlier-in-the-stream photon, while the guy moving away measuring a later-in-the-stream photon? How is this explained?