The following is the Einstein’s train but instead of train consider two airships of equal in lengths. http://www.youtube.com/watch?v=wteiuxyqtoM&feature=related Both are moving with same speed but opposite in direction. After certain time they cross each other such that one is exactly above the other (front of upper ship is exactly above the rare of lower and rare of upper is exactly above the front of lower). The stationary observer would see that light strike the rare and front of each ship at the same time. While both the moving observer would notice that light strikes the front before the rare end of their respective ship. So who is right? Upper moving observer Lower moving observer If both are right then both are wrong also. It means they noticed the same thing as stationary observer.