On Sunday, 4 March 2018 21:41:33 UTC, Fox's Mercantile wrote:
On 3/4/18 2:31 PM, Gareth Magennis wrote:
Just from memory, I can't be arsed to Google it right now,

isn't there some piece of metal held in a vault somewhere (possibly
France) that is defined to be the accepted length of a metre?

That would be the Bureau international des poids et mesures.

The original international prototype of the metre is still kept at
the BIPM under the conditions specified in 1889.

The BIPM is also the keeper of the international prototype of the
kilogram.

The BIPM is situated in the Parc de Saint-Cloud, at Sèvres, in the
suburbs south-west of Paris.

Postal address: Pavillon de Breteuil, F-92312 Sèvres Cedex
Street address: 12bis Grande Rue, F-92310 Sèvres

However, it's still just an arbitrary measurement. It was based on
a fraction of the earth's diameter. And derived from a small arc of
said diameter. Coincidentally it just happened to end up being close
to the same length of the English yard.

Frequency is another arbitrary system. It is based on the rotation
of the earth divided by 86,400 for seconds. Or 24 for hours, which
had already been standardized during the Roman Empire.

The primary advantage of the Metric system is all the units are
related to one another and divisible by ten. Length, volume, weight
etc.. Unlike the relationship between inches, ounces (liquid) and
ounces (weight) that all have different divisors. Inch, feet, yards,
miles etc..

Somewhere I have a book from the 1800s that lists the sizes of imperial measurements in various countries. They are nearly all different, that is the prime reason metric became popular, traditional units became a mare when international trade greatly expanded.

Easy division by 10 is sometimes useful. Easy division by 2,3,4,6 & 12 is sometimes useful. I pick my system according to which works better for each task.


NT