Some of these terms already have other meanings. For instance:
the metric mile = 1500 metres exactly (see
http://en.wikipedia.org/wiki/Metric_mile )
the metric foot = 30 cm exactly (see
http://www.gwydir.demon.co.uk/jo/units/length.htm )
There have been proposals for other metrified English units:
the metric inch = 25 mm exactly
the metric yard = 900 mm exactly
the metric chain = 20 m exactly
the metric furlong = 200 m exactly
(see http://en.wikipedia.org/wiki/Metrified_English_unit )
--
John Hynes
www.decimaltime.org
----- Original Message -----
From: "Pat Naughtin" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[email protected]>
Sent: Thursday, January 19, 2006 3:40 PM
Subject: [USMA:35748] Re: decimal time
Dear Phil,
Thanks for your analysis, below.
This is why I refer to the post-1959 measures as:
the metric inch = 25.4 millimetres exactly,
the metric foot = 304.8 millimetres exactly,
the metric yard = 914.4 millimetres exactly,
the metric chain = 20.116 8 metres exactly,
the metric furlong = 201.16 8 metres exactly, and
the metric mile = 1 609.344 metres exactly.
I do this because I find that their descriptively accurate title,
'post-1959
measures with quaint old pre-metric names' too cumbersome.
Cheers,
Pat Naughtin
PO Box 305 Belmont 3216
Geelong, Australia
61 3 5241 2008
[EMAIL PROTECTED]
http://www.metricationmatters.com
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On 20/01/06 10:13 AM, "Philip S Hall" <[EMAIL PROTECTED]> wrote:
It is interesting to note that not only is a yard defined as 0.9144 m
but
the inch is not defined as 1/36 of a yard but as 25.4 mm (exactly).
Therefore, customary measures are all defined by metric ones and not in
relation to each other.
If you do the arithmetic you will find that:
0.0254 * 12 = 0.3048,
36 * 0.0254 = 3 * 0.3048 = 0.9144
0.9144 * 1760 = 1 609.344
all being exact with no rounding.
Hence:
(a) 1 in = 0.0254 m, 1 ft = 12 in
(b) 1 ft = 0.3048 m, 1 in = 1/12 ft
Are equivalent statements, as are
(c) 1 ft = 0.3048 m, 1 yd = 3 ft
(d) 1 yd = 0.9144 m, 1 ft = 1/3 yd
and so on.
Hence to define linear imperial measures all that is requires is the
absolute size of one of them (e.g. 1 yd = 0.9144 m) , and then state the
ratios between all the others. True enough we usually do see the absolute
sizes tabulated rather than the ratios but it doesn't alter anything.
The real bombshell (if they only but knew it) is the use of that word
"exact" in relation to the figures 0.0254, 0.3048, ...
When it comes to the real world there is no such thing as "exact". All
measurements have a tolerance however small it may be. Hence imperial
measures are *tied* to metric by an abstract idealised relationship.
Imperial can have no independent physical definition of its own on that
basis.
Phil Hall
