Thanks for replying. That's an interesting answer. I will have to study it in order to see if I think the "qualification" makes the "yes" into a "no". But it will have to wait, I'm afraid. For my purpose, I can not presuppose length contraction, time dilation or relativity of simultaneity. I am trying to discover these phenomena through Einsteins descriptions of the experiments and the two postulates. If I put the conclusion among my premises, I am doing circular logic, and I would only be confusing myself. I note that Einstein says nothing about length contraction in this experiment. He is apparently satisfied that he can explain the relativity of simultaneity to me without it. This does not mean that I deny length contraction, I have just not discovered it yet. I have found a slowdown of clocks, but all of it is meassured fom only one frame of reference, and I have been told it is really only the Doppler effect, and that there is an additional, relativistic slowdown of the clocks. I have still to find that one, too. I haven't looked into length contraction yet. I have re-read the paragraph of "Relativity" you pointed me to. I have not changed my mind. I will come back to you with a post where I explain my reading of it, so that you may point out faults in my reasoning.