A plehtora of Quantities

[David Berry]

Guy,

> What if the real-world quantity is dimensionless? Should we add 'nodims' or
> something as a kind of quasi-unit?

Do you mean dimension-less, or unit-less? Angle is dimension-less, but it
has units (rad.s, deg.s etc). Numbers which count something are
dimension-less, but they can be said to have units of the thing they are
counting. E.g. the FITS standard for units (see FITS-WCS paper 1) includes
units like "pixel". Can you think of a quantity which has no units in this
sense?

David




>
> On Thu, 13 May 2004, Alberto Micol wrote:
>
> > > Want a quantity with errors but no units?  Go right ahead.
> >
> >
> > I think we should forbid such option, really!
> > Of course, unless you can convince me of the contrary.
> >
> > Alberto
> >
> >
> >
>
> Guy Rixon 				        gtr at ast.cam.ac.uk
> Institute of Astronomy   	                Tel: +44-1223-337542
> Madingley Road, Cambridge, UK, CB3 0HA		Fax: +44-1223-337523
>

----------------------------------------------------------------------
Dr David S. Berry    (dsb at ast.man.ac.uk)

STARLINK project		 |	Centre for Astrophysics
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Rutherford Appleton Laboratory	 |	PRESTON
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