My friend posed a question to me that I was unable to succinctly answer (or answer at all for that matter). So I thought I'd make an account and ask people who know more about this than I do. Ok. So let's assume that Person A starts at Position 1. Person B is at position 2, which is 1 light year away. There also exists a giant reflective surface between them such that these three points form an equilateral triangle (where Position 1 is the bottom left corner, Position 2 is the bottom right, and the reflective surface is at the top). So Person A leaves Position 1 going 90% of the speed of light directly towards Position 2. At the same time, a beam of light is shot from Position 1 directly towards the reflective surface, such that when reflected, it will eventually reach Position 2 (in what would be exactly double the time at slower speeds). Person A, though he is traveling 90% of the speed of light, will still see that beam of light as going the speed of light relative to his speed, correct? If that is the case, from his frame of reference, the beam of light will reach Position 2 much earlier than he does. However, Person B standing at Position 2 would see Person A arrive much earlier than the beam of light. Therefore, Person A would see the beam of light arrive before him, but then be able to witness the light arriving as he stood next to Person B? This is the question he posed. Any help?