... and some of which rely on no physical laws at all, e.g. currency units. (01)
Mike (02)
David Leal wrote:
> Dear Josh,
>
> 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.
>
> 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.
>
> Best regards,
> David
>
> 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.
>>>
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>>
>
> ============================================================
> David Leal
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> (03)
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Mike Bennett
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