Is it arbitrary? It is the distance traveled by light in a 
vacuum in 1/299,792,458 of a second so that it is always a 
repeatable distace. Then again I dont know the reason why 
they picked 1/299,792,458 of a second so I guess that is 
arbitrary.

Thanks,
Chris

---- Original message ----
>Date: Thu, 16 May 2002 20:42:48 +1200
>From: Andrew Grebneff 
<andrew.grebneff@STONEBOW.OTAGO.AC.NZ>  
>Subject: Re: Warning!!! �Check Your Speedometer - What a 
Sad, Sad Example  
>To: vanagon@GERRY.VANAGON.COM
>
>>Reportedly, grade-school students spend a few days on 
measurements,
>>practicing moving the decimal place around. Once they
grasp the ease
>>of metric, they forget it. No conversions to do. Nothing. 
Then they
>>move on, while American students spend endless days (not)
>>understanding how to convert inches to feet to yards to 
miles to...
>
>Matric is the ONLY system which makes any sense. The meter 
itself may
>be arbitrary in length, but the other measures are all 
based directly
>on it.
>
>1000 microns = 1mm
>1000mm = 1m
>1000m = 1km
>
>It's all based on thousands, not hundreds.
>
>1000mm3 = 1cm3 (=1ml)
>1000 cm3 (ml) = 1l
>1000l = 1m3
>
>Also:
>10mm= 1cm
>10cm = 1dm
>10dm = 1m
>
>What could be more logical? I'm glad I began using metric 
myself as a
>kid, before Canada (where I lived then) metricated. I can't 
remember,
>nor do I care, how many feet or yards there are in a mile.
And I use
>maps a lot, being a paleontologist (of sorts), and often 
need to work
>distances out exactly. On the maps 2mm=50m. 20mm=1km. Easy.
>--
>Andrew Grebneff
>165 Evans St, Dunedin 9001, New Zealand
><andrew.grebneff@stonebow.otago.ac.nz>
>Seashell, Macintosh, VW/Toyota van nut