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Re: [uom-ontology-std] retitled: Units of an angle

To: "'uom-ontology-std'" <uom-ontology-std@xxxxxxxxxxxxxxxx>
From: "Patrick Cassidy" <pat@xxxxxxxxx>
Date: Tue, 21 Jul 2009 14:08:44 -0400
Message-id: <0a0c01ca0a2e$4931bc10$db953430$@com>
Just a comment on one point in Ingvar's last note:    (01)

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.    (02)

Pat    (03)

Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx    (04)




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