> But what comes below is exactly paragraph 1.2 in VIM 2008 (= JCGM 200:2008
> (E/F)).
>
> Ingvar J (01)
True. But your use of the word "but" implies that I have denied this to be so.
Having read some, but not all, materials on dimensions and units, I cannot deny
that other sources may be sufficient. I found the ISO documents the most
complete, and are, I assume, the most authoritative.
Other, derivative documents I have found to be less complete. (02)
Regarding the current state of physics, I think that everyday applied physics
is
best for the target user group. Cutting edge theoretical physics is not
sufficiently stable, nor useful, to chase after with ontologies. (03)
R/jbc (04)
ingvar_johansson wrote:
>> Just a comment on one point in Ingvar's last note:
>>
>> On mass:
>>> 3. You write: "and in middle school we learn that each kind of such
>>> particles has a mass which can be computed as the sum of the mass of
>>> its constituents." Not EACH kind of particle. Photons and neutrinos
>>> have no mass.
>>>
>> Photons have relativistic mass, though no rest mass; neutrinos actually
>> have
>> a very small rest mass (according to the latest info I have). The "mass"
>> we
>> measure is relativistic mass, and I don't think any distinction is
>> required
>> in the units ontology (though it would be in an ontology of physics).
>> Relativistic mass is a very useful concept because it provides a simple
>> definition of 'physical object' as an Object (primitive concept) that has
>> some mass; that would include photons and any other fundamental particles
>> that have relativistic mass.
>
> I think one should be careful not to make definitions TOO dependent on the
> present state of physics. Wikipedia says: "The Standard Model of particle
> physics assumed that neutrinos are massless, although adding massive
> neutrinos to the basic framework is not difficult. Indeed, the
> experimentally established phenomenon of neutrino oscillation requires
> neutrinos to have nonzero masses." Since not long ago the standard model
> was accepted, and neutrinos regarded as physical objects without rest
> mass, physics may also in the future discover particles that they would
> like to regard as both lacking rest mass and being physical.
>
> Ingvar J
>
>
>> Pat
>>
>> Patrick Cassidy
>> MICRA, Inc.
>> 908-561-3416,
>> cell: 908-565-4053
>> cassidy@xxxxxxxxx
>>
>>
>>
>>
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>
>
>
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> (05)
--
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Joseph B. Collins, Ph.D.
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