????? What? I'm sorry, Joe, but how can you say that when I have been saying the very thing that I oppose about the definition of the metre is the fact that it's been pegged to the second (even a fraction thereof), another base unit? I'm sorry, but you completely lost me here now... :-S
I've been defending that BIPM folks should NOT use the crutch of ANOTHER base unit (be it the second, candela, kilogram, w-h-a-t-e-v-e-r) for the definition of any base unit, at least not *directly*. It's acceptable though if some "outside properties" would be tied to it, like they do it with the definition of the ampere (metre) and the candela (watt, if I'm not mistaken). In other words, if the property is the length, focus on *IT*. Therefore, I found the previous definition, using wavelength sizes, most (and more) appropriate, despite its lack of better accuracy compared to the current one. So, this has just been a big misunderstanding. Marcus On Thu, 11 Apr 2002 16:05:37 Joseph B. Reid wrote: >Marcus, in USMA 19409, indicates that he still does not believe that the >latest definition of the metre involves the second. I can only refer him >to the metric bible, page 116, Resolution 1 of the 17th CGPM, 1983 which >stated: >"The metre is the length of the path travelled by light in vacuum during a >time interval of 1/299 792 458 of a second." > >>Possible, of course. But it would help foster better understanding if you >>present how I was supposed to have understood that message of yours... >>;-) >> >>Thanks in advance for your willingness to clarify that, if you'd be so kind. >> >>Marcus >> >>On Wed, 10 Apr 2002 16:47:28 >> Joseph B. Reid wrote: >>>I am afraid Ma Be in USMA 19387 completely misunderstood what I wrote in >>>USMA 19374. >>> >>>> Joseph B. Reid wrote: >>>>... >>>>>Appendix 1 of the metric bible states that the CPGM of 1975 redommended a >>>>>value for the speed of light. The second is the most accurately defined >>>>>unit that we have. It is axiomatic that >>>>> c = speed of light = lamda X frequency. >>>>>The frequency of a laser can be determined, and by the equation, so can its >>>>>wavelength. This gives a standard of length that is more accurate than the >>>>>previous metal bars. It could be stated that it as based on the wavelength >>>>>of a radiation of a specified frequency, or as the path travelled by light >>>>>in a specified time interval. The CPGM decided in favor of the latter form >>>>>of the statement. >>>>>... >>>>Very good, Joe. Thanks. Which goes to show that one CAN define the metre >>>>without resorting to the "crutch" of the second after all. Again, it goes >>>>to show how much we may still have to do and work in terms of the >>>>*conceptual* aspect of defining a system of units. >>>> >>>>Marcus > > >Joseph B.Reid >17 Glebe Road West >Toronto M5P 1C8 Tel. 416 486-6071 > > Is your boss reading your email? ....Probably Keep your messages private by using Lycos Mail. Sign up today at http://mail.lycos.com
