Dear All, (01)
I don't disagree with any of the conclusions, but it is not our job to
decide what things like force are. (02)
The BIPM (http://www.bipm.org/en/si/si_brochure/chapter1/1-2.html and linked
pages) says that both the quantity force and its unit the Newton are defined
by reference to the equation f = ma. Our job is to produce a formal record
of what the BIPM says. We only have grounds for arguing back if we detect a
logical inconsistency. (03)
Best regards,
David (04)
At 07:10 10/08/2009 -0400, you wrote:
>I agree with John's comments (below).
>
>I think that for the UoM we can adopt the principle that the dimensions
>(time, distance, mass, temperature, etc.) that are standardized by the basic
>units are themselves "primitive" and logically undefinable, whose meanings
>and usage in programs are generally understood. However the standards
>against which they are measured and the techniques by which they are
>measured can be related to the basic dimensions by semantic relations, and
>the values of those relations may change over time. For those other
>dimensions that are not directly definable as combinations of the basic
>dimensions (e.g. hardness, and I would include force, whose meaning is not
>just 'ma'), it may be best to also treat them as "primitive". For the
>primitive dimensions our main concerned would be how to relate those
>different dimensions of measure to the way the unit is defined and measured
>at any given time in history. This entails that the question - of whether
>any given measure is or is not multiplicative versus some basic unit - is
>not the question that determines whether we treat a particular dimension as
>primitive or derived.
>
>Pat
>
>Patrick Cassidy
>MICRA, Inc.
>908-561-3416
>cell: 908-565-4053
>cassidy@xxxxxxxxx
>
>> -----Original Message-----
>> From: uom-ontology-std-bounces@xxxxxxxxxxxxxxxx [mailto:uom-ontology-
>> std-bounces@xxxxxxxxxxxxxxxx] On Behalf Of John F. Sowa
>> Sent: Monday, August 10, 2009 1:37 AM
>> To: uom-ontology-std
>> Subject: Re: [uom-ontology-std] uom-ontology-std - strawman UML
>>
>> Ingvar and Pat,
>>
>> 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.
>>
>> 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.
>>
>> 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.
>>
>> 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.
>>
>> Implications for computational uses of a UoM ontology:
>>
>> 1. Whatever system of ontology we propose should support multiple
>> "microtheories" or whatever else one would like to call them.
>>
>> 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.
>>
>> 3. But all of them can use the same words and values for the
>> basic units of measure.
>>
>> 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.
>>
>> 5. The detailed axioms and definitions should be contained in
>> microtheories for whatever physical theories are assumed for
>> any particular application.
>>
>> 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.
>>
>> 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.
>>
>> John
>>
>>
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>
>
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> (05)
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