Dear John and others, (01)
We are still seeking a definition of the term "scale". (02)
In your e-mail you have used "scale" as a synonym for "kind of quantity",
because both temperature and mass are kinds of quantity. (03)
I have proposed that a scale be defined as a function from a kind of
quantity to a "set of elements with axioms", such as the real numbers. To be
a valid scale there would have to be constraints upon the nature of this
function. I have no strong opinion as to whether the term scale should be
applied to this function, or to its inverse, or to both. (04)
I don't think that my proposal has consensus, but I am not clear about
further proposals. (05)
Best regards,
David (06)
At 09:37 14/08/2009 -0400, you wrote:
>Dear Matthew and David,
>
>DL> Hence we have two different instances of kind of quantity, for
> > which the same unit is used. Pressure is a quantity for which zero
> > is well defined, and there is no problem in regarding the bar, psi
> > or Pa as firstly a magnitude of absolute pressure. If it is assumed
> > that there is an addition operator for the kind of quantity absolute
> > pressure, then the same unit can be used for the kind of quantity
> > gauge pressure. This assumption is usually unstated but I believe
> > that it is necessary for the use of the same unit for both kinds
> > of quantity.
>
>If you have a scale with an absolute zero, such as temperature
>or mass, you can still talk about intervals, such as adding
>an extra 10 degrees of temperature or 10 grams of mass.
>
>But for interval measures, such as time and space, there is
>no absolute zero, and only intervals are meaningful. The
>choice of "zero" is an arbitrary convenience.
>
>John
>
>
>
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> (07)
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