Originally posted by dehammer:
[QUOTE]lets see. person a is moving away from person b at .8 speed of light, and light headed in the opposite direction is moving away from him at speed of light so the light is moving away from person a (who has not changed his speed at all) at 1.8 times the speed of light? no. its the perception that is the key. it would appear to person b that the light is moving away from him at light speed, but the light would still be moving away from person a at the same speed. he never altered his movement. light never sped up. the light is moving the same speed for both of them. just they perceive it differently.
The fact that person a is moving at 0.8c from person b and experiences light moving away from him at light speed c, does NOT mean that person b measures a light speed of 1.8c in his reference frame. This is the whole point of special relativity. When measuring light speed in your inertial reference frame (within which you are stationary) you will measure the speed of light as c notwithstanding the speed at which the light source is moving relative to you. Speeds cannot be added linearly when applying special relativity.
