hello, imagine 2 source of light. In the middle there is an observer who is moving towards one source at a determined speed s. The 2 sources send a ray of light when the observer is perfectly in the middle. In the observer's point of view, the 2 rays of light travel towards him at the relative speed of c, so they meet exactly at the same point on the observer; this is impossible because in the meantime the observer has travelled for some space, so the 2 rays have to meet together not in the middle, but near a source. I cannot solve this problem, can you help me? thank you. regards, kknull P.S. Excuse me for my bad english!