I took a course in special relativity as an undergrad, but am now almost 6 years removed from it and have not retained much of the info. Let me pose a scenario I came up with that is a modification of a problem discussed in that class: Suppose there is a train moving at some fraction of the speed of light relative to an observer outside the train. There is a light source at either end of the train set to emit a single photon on separate timers. They are set to emit photons at the same clock time as perceived by an observer in the train. The observer waits in the middle of the train. He's a sad guy, so he's decided to potentially give his life to science in a grandiose experiment in collusion with the savvy non-exploding stationary observer. (He's constructed a device that will detonate a bomb if it detects the photons arriving at the same time.) I have two questions: 1) Do the photons arrive at the same time as perceived by the observer in the middle of the moving train? How about the stationary observer? (in other words, does the bomb detonate?) 2) Related to question #1: would the stationary observer who sees the train explode/not explode scratch his head at the outcome of their little experiment? [ie - would he observe a seemingly contradictory event prior to the train exploding/not exploding] If the answer to #2 is yes ... then I am deeply troubled.