[boost] Re: Dimensional Analysis Interest?

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

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