Thanks,
Sid
At 11:30 AM 04/08/2002 -0400, James R. Frysinger wrote:
Ma Be wrote:
>
> On Sun, 7 Apr 2002 19:24:33
> Joseph B. Reid wrote:
> ...
> >Would Ma Be be happier if the metre was defined by "Light travels in vacuum
> >299 792 458 metres during a time interval of one second"?...
> >
> Good try, Joe, but I'm afraid the above would also NOT be acceptable. While it would address the fraction aspect it would continue to be silly. Usually one would require to define what a UNIT of the measurement in question is! In other words, it would solve one aspect while creating a much bigger problem.
>
> So... Nah... Get rid of using the second and stick with some definition that would point *directly/straight* to a length size just like it was with the previous definition.
Physical artifacts (objects) change dimension with temperature. One of
the most precise methods of measuring distances (lengths) is
interferometry, which is senstitive to less than one wavelength of
light. An atomic transition is more stable and in the long run much more
precise than a physical meter stick, even one with fussy temperature
controls.
Physical standards (artifacts) are also located in only one spot at a
time. Thus, NIST still must have its kilogram mass compared periodically
to the prototype in Sevres. They used to have to do this with their
meter artifact, as well. But now, anyone can set up a valid meter
standard for a relatively small sum and don't have to worry about their
national standard being lost at sea or out of use during calibration.
This may be hard for some people to comprehend and appreciate,
especially those who have not used an interferometer, counting circuits,
and the like. But that's the way it is. The CIPM is going for precision
more than public understanding by those without sufficient background
(at least a few years of physics, for example). For an analogy, ask
yourself this: Should modern medicine limit itself to diagnostic,
surgical, and therapeutical techniques that the common man on the street
can understand? Ooops, there go our MRIs, CT scans, laser sugeries, etc.
Your inclination to stop progress on realization of standards, due to
lack of understanding, is quite analogous to the inclination of
Americans not to commit to the metric system, which they feel they don't
understand as well. The accuracy of those feelings has nothing to do
with their resulting inclinations. An unkind person might say that
you're just being a luddite at a higher level of misunderstanding. Of
course, that's quite blunt and perhaps tactless, so I wouldn't put it
that way.
Jim
--
James R. Frysinger University/College of Charleston
10 Captiva Row Dept. of Physics and Astronomy
Charleston, SC 29407 66 George Street
843.225.0805 Charleston, SC 29424
http://www.cofc.edu/~frysingj [EMAIL PROTECTED]
Cert. Adv. Metrication Specialist 843.953.7644
