Two bombs lie on a train platform, a distance L apart. As a train passes by at speed v, the bombs explode simultaneously (in the platform frame) and leave marks on the train. Due to the length contraction of the train, we know that the marks on the train will be a distance γL apart when viewed in the train’s frame (since this distance is what is length-contracted down to the given distance L in the platform frame). How would someone on the train quantitatively explain to you why the marks are γL apart, considering that the bombs are only a distance L/γ apart in the train frame?