This is a bit like a batter saying that he cannot measure distance when watching an approaching baseball with one eye closed. Then complaining when the ball hits him in the face. "Hey Ump, that ball could not have been moving because I could not see it moving!"John Mcrain said:I know that light beam has diagonal trajectory, but I cant see it from this position/case..
Say that the train is moving at 0.6 c and the light clock is 4 feet in height. If the light pulse has a 5 foot diagonal trajectory, it will take 5 nanoseconds to follow that trajectory, not 4. Even if we look from in front rather than from the side. The train and light pulse will have moved 3 feet forward in this time.