Einstein's Clock on a Train

The Einstein clock on a train refers to a thought experiment done by Einstein when he was elaborating his SR relativity theory. This thought experiment consists of a light beam reflecting back and forth between two parallel mirrors, acting like a clock, and being on a moving train. The speed of the light ray, viewed by two observers, one from the embankment and the other one on the moving train, is the basis of the thought experiment. From this experiment, Einstein deduced that time and space are not absolute in the universe and depend on the velocity of the observer. We will show that the conclusion about this experiment depends on the way the light beam propagates with respect to the two observers and demonstrate why Einstein is wrong