imagine two people in deep space, with no frame of reference but each other. if one of them is speeding along at near lightspeed, he might just as well assume he is stationary and the other guy is moving. how can we get around this problem, without something like the ether?? secondly, does light speed up when traveling towards a mass, as it slows down when traveling away from it? or am i just misunderstanding something? i am not too clear about relativity, so please keep explanations simple... thanksalot.