There is a moving light clock at a certain velocity. For an outside observer, the light just seemed to be traveling in a slant path. So far, it is right for the outside observer, the light is going in a slant path and hitting the top bar and then again returning and hitting the bottom bar. Now, suppose the moving light clock changes its velocity periodically, then if I'm right, the track of the light now for the outside observer, will be, as if it is following and changing its track, as if the light knows when to change the track. How would the outside observer explain, the changing of the track of light in the space? I hope I have made my question clear. What is it, I'm not understanding here? Thanks very much.