I guess most of you are familiar with the "paradox" of the train passing through a tunnel smaller than itself on a speed close to the speed of light and 2 guillotines (1 in the exit and 1 in the entrance of the tunnel) going down/up when the train is "fully inside" the tunnel ( http://www.pcbheaven.com/opendir/index.php?show=3550vf5099tla8512e2c ).
I think I fully understand the explanation of this paradox, and I think it's ok for a person in the frame of reference of the train to think that the events are not simultaneous.
But what would happen if, instead of both guillotines being activated at the same time, the entrance guillotine would be activated first and this would cause the activation of the exit guillotine. For instance, when the entrance guillotine is activated, it starts to fall uncovering a light signal that goes to exit guillotine and activate itself. (Remember that the train is running in a speed close to light, let's assume 0.5c, so the signal is faster.)
How would the explanation be in that case in both frames of reference?