One person on the ground and the other traveling in a train. Two light detector X and Y are placed in the train at equal distance from the observer in the train. If only one is hit first by the light, only that detector will display its name else if both detector are hit simultaneously both detector will display their name. When both are just exactly facing each other, a light source from the observer in the train is switch on. Since in relativity two person will not agree on simultaneity, person on the ground will found that the detector to the rear end of the train only display its name while the person on the train will found both the detector display their name because in his frame both the detector are hit by the light simultaneously. Wouldn't the person on the ground find his observation wrong when the train come to rest. Isn't the outcome of a same event would be different if both are correct.