This has bothered me for a long time. I understand that time varies with velocity relative to the observer. But what about this case -- Suppose we have 3 space ships: A, B, and C. They are spaced widely apart with B in the middle and A and C at opposite sides to B. A and C are moving towards each other at relativistic speed (equal but opposite) and B is sitting still. How are the clocks varying? I can see that B sees A'a and C's clock slowing down, but what about A vs C? For example, from A's pov, B and C are moving towards him with B going half as fast as A. So according to A, B and C's clocks are running slow. But C thinks the same thing about A and B. So everybody is thinking every one else's clock is the slow one. How is this resolved?