[RR wrote:] (So why didn't anyone chew you out for not even having a Sig?) First of all, no mere definition can cause the outcome of any scientific experiment. Second, the definition that pertains to a speed of light is the one that states that - by pure definition - a speed of light is _exactly_ 299,492,458 m/s, but what speed of light is being defined to be an exact number here? It cannot be light's two-clock, one-way speed because no one has ever measured this speed. Thus, it has to be either Maxwell's _NO-clock_ speed or the one-clock, round-trip speed. I fully agree of course that Maxwell's c is very close to the above number, and I also fully agree that the round-trip, two-clock light speed is very close to the above number, but I cannot agree that the one-way, two-clock speed is close to the above number, and no one has shown that it is close. If you think that I am speaking some sort of gibberish here, then please recall the fact that Einstein himself obtained a value for the one-way speed of light that differed greatly from c. No, I am not making this up. See the next paragraph. In his book "Relativity_, Einstein noted that - given the truly synchronous clocks of classical physics - (and he was not able to prove that such clocks cannot exist) light's one-way, two-clock speed will vary with the observer's velocity (and Einstein wrote this mathematically as c - v for a departing light ray's speed). If you still want to protest, then look again at Einstein's little equation (which contained c - v as light's one-way speed) and tell me how he derived it. Also tell me what it means physically. I guarantee you that you will have to conclude that it was due to the use of the truly synchronous clocks of classical physics on paper. No amount of protesting or objecting from anyone can do away with the fact that Einstein himself obtained the result c - v on paper. And Einstein was not able to prove that this result will not _still_ occur truly synchronous clocks are used; all he did was force clocks to obtain his chosen value c, supposedly chosen or given purely by mere definition! It was certainly NOT given by any experiment using two clocks! This is why it is extremely important to separate the two-clock case from the other cases (i.e., from the one-clock and the no-clock ones). These three cases are fundamentally different. There are three different speeds of light. And the one-way speed has not been determined yet. (By the way, the second is 9, 192, 631, 770 cycles of some atomic radiation, so it is not "defined by reference to the speed of light," as you said.) One final remark: What is your personal prediction for the outcome of "the one-way light speed measurement by using two clocks"? ------RR------(you can call me a stupid crackpot all you want, but I speak with unforked tongue! :-) ) _________________________________________________________________ Help protect your PC. Get a FREE computer virus scan online from McAfee. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963