On Jul 15, 2009, at 7:00 PM, Ed Barkmeyer wrote: (01)
> James Davenport wrote:
>
>> Personally, I'm not sure that I would give 'length' and 'width'
>> different kinds, but that's why we will (when we actually get down to
>> talking about populating the ontology) be having these debates. Two
>> better examples are torque and energy,
>
> Torque and energy are different kinds of quantity, and their instances
> are not comparable. The confusion here arises from the fact that they
> differ in their dimensional formulations by multiplication by a kind
> of
> quantity (angle) that has no "unit". (Its model is arc length/radius,
> i.e. length/length.) (02)
It always bothered me that dimensional analysis made angles
dimensionless, when they are of such profound physical significance.
Clearly, direction of length matters. The fact is, 'length' should be
treated as a vector rather than a scalar. This also, btw, helps with
distinguishing length from width from height. BUt this is probably
going too far out in left field for this forum :-) (03)
>
>> or the distinction between relative and non-relative temperatures
>
> Pandora's box number 2. Absolute temperatures (which is the usual
> kind)
> and date-time are very special problems. They don't work like other
> measurements. (04)
Date/time is a mess because the scales aren't additive (months screw
things up), but the underlying model of time-intervals is quite
coherent. Temperature is interesting: another dimensionless
dimension :-) (05)
PatH (06)
>
> -Ed
>
> --
> Edward J. Barkmeyer Email: edbark@xxxxxxxx
> National Institute of Standards & Technology
> Manufacturing Systems Integration Division
> 100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
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>
> "The opinions expressed above do not reflect consensus of NIST,
> and have not been reviewed by any Government authority."
>
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> (07)
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