[SciPy-User] Error in constants documentation?

David Goldsmith d.l.goldsmith@gmail....
Wed Apr 7 14:13:04 CDT 2010


Oh wohl, I tried.

DG

On Wed, Apr 7, 2010 at 12:03 PM, Robert Kern <robert.kern@gmail.com> wrote:

> On Wed, Apr 7, 2010 at 13:57, David Goldsmith <d.l.goldsmith@gmail.com>
> wrote:
> > On Wed, Apr 7, 2010 at 11:40 AM, Charles R Harris
> > <charlesr.harris@gmail.com> wrote:
> >>
> >> On Wed, Apr 7, 2010 at 12:32 PM, David Goldsmith <
> d.l.goldsmith@gmail.com>
> >> wrote:
> >>>
> >>> On Wed, Apr 7, 2010 at 10:52 AM, Charles R Harris
> >>> <charlesr.harris@gmail.com> wrote:
> >>>>
> >>>> On Wed, Apr 7, 2010 at 11:02 AM, Florian Lindner <mailinglists@xgm.de
> >
> >>>> wrote:
> >>>>>
> >>>>> Am Dienstag, 6. April 2010 22:08:53 schrieb Arthur M. Greene:
> >>>>> > It would seem that there is some confusion, in the
> >>>>> > constants.html, between force and mass...
> >>>>>
> >>>>> Beside the wrong unit which is fixed now I don't see any confusion.
> >>>>>
> >>>>> > Strictly speaking, kg is a unit of mass, Newton a unit
> >>>>> > of force. Weight is force, not mass: A gold brick
> >>>>> > floating in interstellar space is weightless but still
> >>>>> > massive.  Pounds and kilograms can be equated, but only
> >>>>> > in some specified gravitational field (like at the
> >>>>> > surface of the earth, where we usually weigh things).
> >>>>>
> >>>>> This is true for pounds-force and kilograms. Pounds-mass and
> kilograms
> >>>>> could be equated in any context. Pound itself is ambigous.
> >>>>>
> >>>>> > So mass is the more fundamental quantity, since it does
> >>>>> > not depend on gravity for its value. In Imperial units
> >>>>> > (feet, pounds) the unit of mass is the slug:
> >>>>> > http://en.wikipedia.org/wiki/Slug_(mass)<http://en.wikipedia.org/wiki/Slug_%28mass%29>.
> This is
> >>>>> > absent from the constants page.
> >>>>>
> >>>>> Mmmh.. never heard of it though I read quite some English language
> >>>>> aerospace engineering literature. However I'm using SI units. I think
> >>>>> pounds-mass is more widely used as a imperial unit of mass.
> >>>>>
> >>>>
> >>>> I recall slug being used in amateur rocketry books 50 years ago or so.
> >>>> But SI units are definitely simpler.
> >>>>
> >>>> Chuck
> >>>
> >>>
> >>> OK, since Charles opened the door: what about taking the bold,
> >>> forward-looking step of not supporting "Imperial" units at all?  (I say
> >>> "good riddance.")
> >>>
> >>
> >> Well, what if someone wants to know what a slug is in SI units? It's not
> >> as if it is a big problem to support,
> >
> > I think as time drags on it will become a bother to support; if someone
> > needs Imperial support, they can roll their own.
>
> They're constants. The amount of support they need is smaller than the
> smallest function in our codebase.
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless
> enigma that is made terrible by our own mad attempt to interpret it as
> though it had an underlying truth."
>  -- Umberto Eco
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-- 
Mathematician: noun, someone who disavows certainty when their uncertainty
set is non-empty, even if that set has measure zero.
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