Jack L Since I've never really understood the MM experiment (indeed I am not so rash as to claim that this has changed in any significant degree) I Gooled 'michalson morley' and after having my spelling corrected, I went to the first of 220 000 hits -- the ubiquitous Wikipedia. I read the whole article -- not a chore -- and I now have a better overview of the experiment and its place at the start of a long line of similar experiments. This article is not a good place to learn the technicalities of the experiment but I found it to be very instructive in the philosophy of the experiment. Some interesting points. Michelson won a Nobel Prize for this experiment in 1907 ie he was recognised. However the most interesting point of this exercise was the fact that despite increasingly sensitive and accurate apparatus, no evidence that an aether had been identified was found. The suggestion, so often made, that MM proves the Earth to be stationary, so far from being conclusively shown, was not even mentioned. As such a proof depends in fact upon the presumption of the existence of an aether which cannot be shown, it seems then that this view springs entirely from a non scientific base. My understanding is that if an aether indeed does not exist, then this experiment says nothing at all about whether the Earth moves or does not move. Finally, while the experiment has a firm place in the history of science, it is remembered for its failure to prove what it set out to prove. Additionally, the experiment was designed to find evidence in support of a widely held hypothesis. It was not designed to explain any anomaly or shortcoming in any theory. This is why Michelson and Morely et al are not scientific heroes. Paul D ____________________________________________________________________________________ Yahoo!7 Mail has just got even bigger and better with unlimited storage on all webmail accounts. http://au.docs.yahoo.com/mail/unlimitedstorage.html