Jim Elwell wrote:
....
> Then we get to some of you guys: some of you seem to think that a bunch of
> laboratory scientists and academics, bright and learned in their own right,
> can write documents describing in minute detail how measurement systems
> should work, and that if any of us deviate from their recommendations, we
> are heretics and apostates.
....
> I am not suggesting we substantially reduce what is already in the most
> fundamental documents (IEEE/ASTM SI 10-1997 or BIPM's The International
> System of Units," but am more convinced than ever that demanding exacting
> compliance with less than truly fundamental aspects of measurement is not
> just ineffective, it can be counterproductive.
....
Jim,
You've written a fine essay here, but I'm not totally certain that I
fully understand what you are saying. So I'll make a point or two;
perhaps we agree or perhaps we disagree a bit.
The SI depends extensively on what is called the quantity calculus but
unfortunately that name probably scares most people off. Essentially it
boils down to viewing quantities as products of numbers and units and to
applying the rules of first year algebra to both parts. This is what
makes it possible for young science students to engage in their favorite
indoor sport---figuring out unit cancellations and doing unit
conversions.
But the SI also depends heavily on practicality. Here's an example of
how that concern enters the decision-making process. On one hand a
derived unit with a special name and symbol simplifies speech and
writing; on the other hand large numbers of these quickly lead to the
impossible task faced by any one person to comprehend them all, thus
leading back to the bad old days of arcane units revered, known, and
used only within an elite club of people working in a narrow field.
Another example is the simple set of (algebraic) rules used to handle
those units and prefixes.
My guess is that all of the above led to the development of an
intentionally lean standard, one which shows great resistance to efforts
to expand it's level of detail, while remaining universal in its
application. On purpose, the rules are limited in number but rigid. Some
might see its few rules as stifling, claiming that their even simpler
version causes no confusion. An example of this might be the proposed
omission of the unit after all but the last product of numbers. Indeed,
in that one field or even in several fields there might be no
possibility of confusion arising. But the SI is there to cover all
fields of measurement and so many nations, many standards organizations,
and many technical and commercial interests meet to tend the rules of
the SI. Only in such a wide gamut of inputs can one hope to be confident
that altering a rule can cause no harm in any field using the SI. To
allow some fields to simplify rules of their choosing while others must
adhere to those rules for the sake of safety and clarity would be to
make the SI no longer universal.
As for being branded a heretic, you are safe. No subpoena will be
thrust into your hand demanding your appearance before a tribunal in
Sevres, there to be caned with a meter stick. You merely risk
demonstrating a departure from the rules that might be innocuous in your
field but perhaps harmful in others. And, of course, you are subject to
the pleasure and wrath of legally governing bodies who invoke those
rules and may show varying degrees of tolerance.
Others have done this in the SI and in non-SI sets of measurement
units. Grill manufacturers rate their grills in "Btu"s instead of Btu/h.
A leading researcher in the study of plasmas recently spoke at our
school and plotted temperature in electron-volts on the x-axis of every
graph. People in each of those two fields know what they *really* mean,
but many others are befuddled by their statements. The SI publishes a
very sparse set of units, prefixes, and rules for the sake of avoiding
that. That's the simple kind of approach I prefer. If I point out that
something a person writes doesn't comply with the SI, that doesn't mean
that I consider the author a heretic but merely one who didn't comply
with the standards specified in the SI. After all, it ain't that hard to
comply with the "grammar rules" of the SI.
Jim
--
Metric Methods(SM) "Don't be late to metricate!"
James R. Frysinger, CAMS http://www.metricmethods.com/
10 Captiva Row e-mail: [EMAIL PROTECTED]
Charleston, SC 29407 phone/FAX: 843.225.6789
