Time dilation

[kkris1]

I would like to comment on Einstein’s “thought experiment” regarding time dilation. In his explanation the light was reflected from the mirror on the ceiling inside boxcar travelling in horizontal direction in regard to stationary observer. It was concluded that even if the light was emitted perpendicular to the mirror, for external observer it would appear to be travelling on angle. Because speed of light is constant, therefore time would have to be longer. But what if there are two light rays , one red and one blue , emitted simultaneously as shown on the diagram below?

time dilation pict1.JPG (14.77 KiB) Viewed 205 times

For stationary observer the light would appear to travel shorter distance (blue ray) in longer time![