Is this situation possible??!!! Hello friends, I have seen many videos that explain time dilation like this. you imagine a two mirrors which are apart by 186000 miles. a light goes and hits the mirror and reflected and hits the other mirror and goes on. This is used to explain a tick of the clock,if it hits the mirror,it is considered as one tick. Think that these mirrors are two points in y-axis. let is move in the direction of x-axis. Well,it the context of who is moving in IRF, Those two ticks travel straight and they consider as two ticks of clock. for an observer, that "light" needs to go in slant direction,so it needs to travel a longer direction,so time dilation to IRF that is moving can be understood in reference to the observer. But my question is: whether the second situation possible. I mean Light moving in slant direction? If you think that it is possible, then you will have to say what caused light to move in slant direction??!!