Imagine if you will, a strand of fiber optic cable 186,000 miles long. A pulse of light is sent through the stationary cable: it takes 1 second for light to travel the entire length of the cable.
Now again, imagine this same fiber optic cable travelling at 98,000 miles per second and a pulse of light is sent through the cable. In this instance both the cable and the pulse of light are travelling in the same direction. How long does it take the light to travel the length of the cable? Would it take the light 2 seconds to travel the 1 light second of distance through the cable?
Carl Sagan, "Thou shalt not add thy speed to the speed of light"
Yet again, picture this same fiber optic cable is travelling at 98,000 miles per second.. but this time the pulse of light is sent in the opposite direction that the cable is moving. Does the light take only half a second to travel the 1 light second of distance?
if the cable is moving at 99.9% the speed of light and a pulse of light is sent perpendicular to the course of the cable... is the information lost because the light cannot move in the direction the cable is moving AND its path within the fiber optic cable?