[time-nuts] Standards for units
cfharris at erols.com
Mon Apr 2 22:09:49 EDT 2007
>>> 1 meter/39.37 inches = 0.02540 meters/inch = 2.54 cm/inch = 25.4 mm/inch
>> As long as exact means within a few parts per million:
>> 1/meter/39.37 inches = 0.025400051 meters/inch ...
>>> -Chuck Harris
>> time-nuts mailing list
>> time-nuts at febo.com
> That's a little sloppy for this list surely.
> In fact the US currently uses 2 different inches the "survey" inch (plus
> yard, mile etc) which is defined by the relation
> 1 metre = 39.37 "survey" inches exactly.
> This inch is used purely for surveying purposes.
> The other inch defined by
> 1 inch = 25.4mm exactly
> is used for everything else.
My recollection when I posted the earlier letter was 24.5 mm/inch was
exact by definition, and I recalled that 39.37 inches/meter was also
exact... a quick calculator check to 6 figures showed that it was exact,
then I tried to 9 figures, and saw that pesky little 0.000000051.
> For confirmation read the appendix C of NIST Handbook 44, where these
> and other units of measurement are described.
> Why on earth one has to have different units all called barrels for oil,
> cranberry juice, dried fruits, liquor (this one varies from state to
> state) etc., defies imagination.
I think the biggest push for metric is the chance to start fresh. But
when metric includes piezes, and poises, and sthenes and steres and stokes...
I guess it ain't all that fresh.
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