Re: when to write radians

[Joe Heafner <heafnerj@VNET.NET>]

On Tuesday, Jul 1, 2003, at 10:42 US/Eastern, Ludwik Kowalski wrote:

> Since numerical representations of all physical quantities,
> in the SI system, are ratios then no units would be necessary
> if only basic SI were used. For example, v=25 would imply,
> automatically, 25 m/s, and not 25 km/s. Likewise for other
> physical quantities, such acceleration or current. But I am
> not suggesting this silly convention. Units are useful.

If I understand what you're saying, then I agree. Units ease the
difficulties for us humans. Other than that, units are not physically
useful in and of themselves because they are completely arbitrary.

> > 1) Decibels are often used to express ratios of two
> >      physical quantities (expressed in the same units).
> >      For example, currents, pressures and voltages.

Yep. We can also add astronomical magnitudes (a logarithmic comparison
of two fluxes) to this list.

> > 2) When we say "a length of a corridor is 20 meters"
> >       we are referring to a ratio of two lengths, that of
> >       the corridor and that of a stick, our secondary
> >       standard of length. Why don't we add "radians,"
> >       "decibels" or "machs?" Because this would not
> >       be useful.

Because the two lengths involved aren't used to define an angle. I
think we're both correct!

Cheers,
Joe Heafner

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