From: Terje Slettebø (tslettebo_at_[hidden])
Date: 2003-04-27 17:04:07
>From: "Robert Ramey" <ramey_at_[hidden]>
> From: =?iso-8859-1?Q?Terje_Sletteb=F8?= <tslettebo_at_[hidden]>
> One more uninformed opinion? It would seem to me the angle
> isn' dimensionless. and it has units of measure of degrees/radians or?
> What am I missing here?
Well, "dimensionless", in the context of SI, refers to that it has no
combination of the seven SI units. It may well be considered a dimension,
outside the SI system, though.
For example radians = length of arc/length of radius = m/m = 1
There's a good reference to the SI system here
(http://physics.nist.gov/cuu/Units/index.html), for anyone interested.
There's also a humorous article with link to a great reference of all kinds
of measurements systems here
(http://research.unc.edu/endeavors/win2003/rowlett.html). To quote:
"The number and variety of terms are far more vast than you might expect,
thanks largely to the unique requirements of science and commerce. For
example, you'll find almost 30 entries under "degree" alone. You already
know about measuring temperature in degrees Fahrenheit or degrees Celsius.
But what about degrees MacMichael, which measure the viscosity of chocolate,
and degrees Quevenne, which measure the density of milk? (When comparing
your milk to some other liquid, just remember that five degrees Quevenne
equal one degree Twaddle.)"
There are also more advanced stuff, such as what is being done in Walter E.
Brown's (who Dave A referred to) SI units library , such as "views", which
is also supported by Eric Ford's SI unit library. For example, you may have
a relativistic view, where the speed of light, c = 1. This may simplify some
calculations in some contexts, such as high-energy physics. In this case,
you can suddenly add length and time, as they now have the same underlying
unit (!) (time and space being two sides of the same thing), and the same
goes for mass and energy.
> Some time ago I made a quantity library along with an article
> that never got published. It doesn't use templates all that much
> and its not suitable as basis for a boost library, but it might contain
> an idea or two that might be useful to included in the new system.
> If there's interest, I can upload it to the files section.
Great. I see from the other posting that you've uploaded it, so I'll have a
look at it.
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