Howdy! In the middle of reading "The Fabric of the Cosmos" by some MIT physicist or something. I'll present the problem differently than he did because i like my presentation better and it doesn't change the meaning of the problem. There is, on a moving train, a pile of gunpowder. On each end of the train, there's a stopwatch that will start when it receives a signal from a light-sensitive monitor. There is an observer on the train and an observer watching the train go by. The gunpowder ignites and makes a small explosion! Both light sensors sense the light generated by the explosion and start their stopwatch. The observer on the train sees that both stopwatches started at the same time, as the speed of light is constant to any observer. The observer NOT on the train, however, sees the stopwatch at the caboose of the train start sooner. Light, traveling at a constant speed, does not get "pushed forward" by the fact that the explosion was not stationary as it happened. However, the sensor at the caboose of the train does get pushed forward by the fact that it is on a moving train! It gets pushed towards the explosion. Likewise, the sensor at the front of the train is being pushed away from the light generated by the explosion. The onboard observer, however, was at rest relative to the train and therefore the fact that the train was moving should not have affected the timing of the stopwatches at all. When the train stops and the two stopwatches are brought together... what the hell happens?