Another question about light and relativity: The way I “understand” the theory of relativity is that it is based on the fact that light always moves at a constant speed in the direction which you perceive it to be traveling. This is how (I think?) Einstein’s light-clock and spaceship analogy works. My question is this: If relativity is based on the observer’s perception of light’s direction, does optical perspective (reality) have an effect? As the light clock gets farther and farther away from the observer, the distance the light is traveling appears to decrease dramatically until it eventually disappears. If the perceived vertical distance the light has to travel becomes shorter, and light continued to travel at the same speed as always, would the clock not tick faster and faster the farther away it gets? It seems to me that the thought experiment only works if the two clocks can be perceived as being exactly equal in height – something that is simply not possible. In reality, shouldn’t the person the spaceship age way faster?? Thanks for your help.