Ingvar and Pat, (01)
I certainly agree that scientists today know far more about the
underlying principles than they did one or two centuries ago.
But the point I was trying to emphasize is that the same units
of measure that they used back then can still be used in the
same way (but with greater precision) for the same kinds of
applications. More people use the meter for measuring roads
and houses than they do for measuring stars and atoms. (02)
That implies that any ontology for UoM should be *neutral* with
respect to Newtonian physics, quantum mechanics, relativity,
string theory, or whatever anyone might discover in the future. (03)
IJ> I would say that it is only after the acceptance of statistical
> thermodynamics that the "absolute zero" became generally regarded
> as the temperature that theoretically is the lowest possible
> temperature. (04)
That's probably true. But Lambert proposed the term 'absolute zero'
in 1779 and gave the very good approximation of -270 C. The fact
that the underlying principles became better understood a century
or so later does not invalidate the use of the concept and its
estimated value during the 19th century. Nor does it invalidate
mundane uses of the temperature scale today by people who have
never studied statistical thermodynamics. (05)
Implications for computational uses of a UoM ontology: (06)
1. Whatever system of ontology we propose should support multiple
"microtheories" or whatever else one would like to call them. (07)
2. Some of those microtheories might assume good old Newtonian
mechanics, others might use relativity, others might use a
nonrelativistic quantum mechanics, and others might use the
latest and greatest theories anybody has proposed. (08)
3. But all of them can use the same words and values for the
basic units of measure. (09)
4. Those points imply that a microtheory for units of measure
should *not* contain detailed axioms and definitions of the
underlying physical principles and theories. (010)
5. The detailed axioms and definitions should be contained in
microtheories for whatever physical theories are assumed for
any particular application. (011)
PC> I think that 'force' is a concept that means a lot more than
> just "ma", and also happens to be directly experienced by many
> sentient animals. (012)
I agree. The UoM should contain the equations that relate the
measures of force to the basic units such as m, kg, and s.
But it should not contain detailed axioms and definitions that
might conflict with any application. Detailed axioms needed
for each kind of application can be contained in microtheories
designed for those applications. (013)
John (014)
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