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From: Jan Langer (jan_at_[hidden])
Date: 2003-10-16 17:04:08

Jan Van Dijk wrote:
> Unfortunately the algebra (the transformation properties) is not linear. Just
> consider conversion from the temperature-'base vector' K (kelvin) to C
> (Celsius), C=K-273.15.
> In technical terms: obviously the K->C base transformation cannot be described
> with a (metric) 00-tensor (or scalar) M via the linear transformation
> relation C=MK.
> This is a nasty habit of temperature units, it seems: the seem goes for the
> Fahrenheit and the (less well-known) Rheamur. I don't know of units for any
> other dimension than 'temperature' with this non-linearity property. It shows
> that people quantified the concept of temperature in an era in which they did
> not have a clue about its true meaning :-)

when thinking about it, i cannot imagine a case where this is important.
it makes imho no sense to add °C to °F or something similar. what is the
result of 20°C plus 10°C? 30°C or (293.17+283.17)°K or just 30 Kelvin?
it is difficult to calculate with units which cannot be used as
differences. and if they can be used as differences they are linear. IMHO.

jan langer ... jan_at_[hidden]
"pi ist genau drei"

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