Dear Josh, (01)
I don't think that we disagree substantially. The kind of quantity
"thermodynamic temperature" is defined by reference to a physical law. The
Kelvin is defined by a physical law and by reference to an arbitrary fixed
point - the triple point of water. However the ITS90 scale is not defined
with respect to either a physical law or the Kelvin - it is an arbitrary
scale which is defined by a measurement process and which has been shown by
experiment to be close to the scale derived from Kelvin. (02)
I think we agree that the ontology needs to encompass different types of
quantity, unit and scale - some of which rely upon illustrious physical laws
and some of which rely upon rather weak ones. In the case of Rockwell C
hardness, the "physical law" is very weak. It is merely that the values
provided by the measurement procedure are consistent with one of the
intuitive understandings of hardness - an ability to resist damage when
impacted by a hard pointed object. (03)
Best regards,
David (04)
At 16:54 07/08/2009 -0400, you wrote:
>David,
>
>Temperature is not at all defined by the measurable processes you
>mention. Those happen to be means of measuring temperature through
>models which relate observable processes to a phenomenon of interest,
>namely temperature. The models may rest on more or less illustrious
>theories, e.g. laws of thermodynamics versus concept of hardness in
>material science. The scale or reference system for relating
>coordinates to measurements within the model may be more or less
>absolute in those theories, e.g. absolute zero versus spatial or
>temporal coordinate systems. Nevertheless, I would contend that they
>are always present where units of measure are being employed
>meaningfully (or should I say, realistically).
>
>Josh
>
>On Aug 7, 2009, at 4:32 PM, David Leal wrote:
>
>> Temperature is not merely a
>> phenomenon defined by the differential thermal expansion of mercury
>> and
>> glass or the behaviour of electrons in a thermocouple junctions,
>> because we
>> have the laws of thermodynamics.
>
>
>_________________________________________________________________
>Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/
>Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx
>Config/Unsubscribe:
http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/
>Shared Files: http://ontolog.cim3.net/file/work/UoM/
>Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard
>
>
> (05)
============================================================
David Leal
CAESAR Systems Limited
registered office: 29 Somertrees Avenue, Lee, London SE12 0BS
registered in England no. 2422371
tel: +44 (0)20 8857 1095
mob: +44 (0)77 0702 6926
e-mail: david.leal@xxxxxxxxxxxxxxxxxxx
web site: http://www.caesarsystems.co.uk
============================================================ (06)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/uom-ontology-std/
Subscribe: mailto:uom-ontology-std-join@xxxxxxxxxxxxxxxx
Config/Unsubscribe: http://ontolog.cim3.net/mailman/listinfo/uom-ontology-std/
Shared Files: http://ontolog.cim3.net/file/work/UoM/
Wiki: http://ontolog.cim3.net/cgi-bin/wiki.pl?UoM_Ontology_Standard (07)
|