If we take a look at the experiment were two observers A (inside a train) and B on the platform observering the train as it pass by. Person A will stand in the exact middle of the train and send out a light wave. Person A will observe the light to hit the wall at the same time, while person two will see the light hit the back of the train before the front. So Einstein says that simultainity is relative, and that what is right depends on the reference frame(whether the light hits the back before the front (B) or back and front at the same time (A). However, what if the front and the back of the train had a censor that need to be hit by the light at the same time or else a gun would fire a shot and kill observer A. Observer A would think he is safe because he observes the light hit the the front and back at the same time, but not observer B who will see the light hit the back of the train first. So what will happend? If (accordingly to Einstein) both observers are right in what they are observering, will the person be shot or not? :S I know there is something I have missunderstood somewhere, but I dont now what that is, and I have tried to figure it out for a while now so Im greatfull for some help!