My impression always was that when you describe a problem in special relativity, you are already implicitly taking into account the light that would need to travel for some person to theoretically "see" a special relativistic phenomenon. I was confronted recently in another thread that this impression was wrong. My question is, is this correct? If so, then after you do your problem using the Lorentz Transformations, or geometrically using the space-time interval, to determine what a person actually sees, you need to do additional computations! Yet, I have never seen this step done personally (granted I learned SR on my own). Is there a reason for this? Is it perhaps that usually this additional computation doesn't change the end result much - or at all - and so we don't usually do it? Are there any guidelines then when to and not to take traveling light into account? Or is it the case rather that the initial conditions we give already take light into effect? In either case, are there some equations to help transform between what you "see" and what actually happens? Or is it something that you always have to do geometrically? Unless, since it's possible I misunderstood, that what you see and what actually happens are one and the same. Thanks.