sitting in the middle of a train while your friend is standing on the embankment outside, watching the train go roaring by. If lightning strikes on both ends of the train just as the train’s midpoint is passing the embankment, your friend would see the two bolts of lightning strike at the same time, because both strikes are the same distance from him, the observer. If asked, he would say the strikes happened simultaneously—an accurate statement of his perception of time. However, from your perspective, sitting in the middle of the train as it moves forward, you will see the lightning that
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