Dear Sirs, I have a question regarding the interpretation of the Michelson-Morley experiment. As I understand it, the special relativity theory implies that, say, if I were to watch another person in a n inertial reference frame (say a vehicle) moving relative to me send a light beam towards the front of the vehicle, we would both register the same speed of light. This would have to be compensated by the slowing of the clock of the person inside the vehicle relative to mine. On the other hand, in the Michelson-Morley experiment, there is no external observer, since the whole experimental set-up is moving together with the Earth. There is thus no external observer relative to whose clock the time within the set-up would slow down. Yet, two light beams are said to arrive to the detector at the same time, even though one of them seems to have covered a longer distance. How can this be explained, if the aether drag hypothesis is rejected?