On Fri, 26 Sep 2003 10:05:08 -0700, Jim Kelley
wrote:



Gene Nygaard wrote:
Apparently Halliday and Resnick were a lot smarter a couple of decades
earlier, when they were only a little past their prime:

Hey Gene,

Maybe Halliday and Resnick in fact _avoided_ becoming "past their prime"
when they adapted their point of view to the one which now prevails.

It isn't a matter of "point of view." This isn't politics or an
opinion poll, and it isn't psychology or sociology, and it isn't
freshman literature. It's a matter of facts--of standards and
definitions. The fact is that pounds are units of mass, and that
pounds force also exist (a recent *******ization, of course).

Their 1981 Appendix misstates those facts. That's it, plain and
simple.

Now prevails? I issue you the same challenge I issued to our
Metrologist:

Show me an official definition of a pound force on the NIST pages.
Bet you can't do so. Note that a conditional definition, with a big
"if", indicating that this is only one possible acceptable definition,
is not sufficient--I want an official definition.

If you can't do that, try a broader problem: Show me an official
definition of a pound as a unit of force from ANY law of ANY country
in the world, or from ANY standard of ANY national or international
standards organization, or from ANY standard of ANY professional
organization.

Halliday and Resnick were right on top of things in 1960, already
aware of the change of definition that had taken place only 1 July of
the previous year, effective immediately on its publication. If you
haven't read what the National Bureau of Standards said in that
announcement, take the time now to do so (partial excerpt below).
http://www.ngs.noaa.gov/PUBS_LIB/Fed...doc59-5442.pdf
http://gssp.wva.net/html.common/refine.pdf

Announcement. Effective July 1, 1959, all calibrations in
the U.S. customary system of weights and measures carried
out by the National Bureau of Standards will continue to be
based upon metric measurement standards and except for
the U.S. Coast and Geodetic Survey as noted below, will be
made in terms of the following exact equivalences and
appropriate multiples and submultiples:
1 yard = 0.9144 meter
1 pound (avoirdupois) = 0.453 592 37 kilogram

Currently, the units defined by these same equivalences,
which have been designated as the International Yard and
the International Pound, respectively, will be used by the
National Standards Laboratories of Australia, Canada, New
Zealand, South Africa, and United Kingdom; thus there will
be brought about international accord on the yard and
pound by the English-speaking nations of the world, in
precise measurements involving these basic units.

Now, perhaps you think something changed between 1960 and 1981 when
the revised Halliday & Resnick came out. What would that have been?
Some change in the law? In the standards kept by the National Bureau
of Standards (later replaced by NIST)? Show me some justification for
a change, some change in facts, that would justify a different "point
of view" as you put it.

Or were Halliday and Resnick just terribly prescient, and they foresaw
some change that took place between 1981 and today? If so, tell us
exactly what that change was.

Or maybe you think that the 1959 redefinition is just some sort of
"legal definition" and that in the sciences we have some other "real
definition" that we go by. Is that your position? No problem if it
is, but if that is indeed what you are claiming, please fill us in on
a few followup questions:

1. What is the nature of the standard for a pound in its "scientific
definition"? Is it something mechanical, something electrical, or
what?

2. Who declared whatever the standard is to be the standard? NIST?
U.S. Congress? ISO? BIPM? The First International Extraordinary
Hydrographic Conference (they are the ones who defined the standard
for the international nautical mile)? Some other entity?

3. When was it made the standard? Just the year will do.

4. To whom does the standard apply? In other words, for whom does
the defining agency have the authority to make the standards?

5. Along the same lines, if this is a "scientific definition" which
differs from the "legal definition," what is its scope? What is "in
science"? Does it include Halliday and Resnick's definition of a Btu,
and their use of units of Btu/(lb °F) for specific heat capacity?
Same for Sears and Zemansky, the textbook cited by the Peacekeeper
Engineer?

6. What is the exact relationship between pounds force and the metric
units, or the relationship to the greatest precision in which it can
be expressed if it is not exact?

7. Even if all this were true, would it mean that the pound is a unit
of mass? Is there some rule that says that textbook authors are
allowed to bury their heads in the sand, and ignore the real world
which does in fact use the definition agreed on by those six national
standards laboratories of some of the most advanced nations in the
world in 1959?


Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/