Gene Mechtly wrote:
>Ton = 1 000 kg is a well established definition of ton in most
>countries (spelling variations aside), and is more explicitly related
>to the SI base unit of mass, kilogram, than is megagram.
> 
>The Mg is unnecessary and is more of a deviation from coherent SI.

I don't understand. Despite the kilogram being the base unit, the names
are manipulated as if the base unit were the gram. Part of the true SI
sequence for mass is:

pg picogram
ng nanogram
�g microgram
mg milligram
g gram
kg kilogram
Mg megagram
Gg gigagram


The tonne is a table 6 unit and is therefore non-SI but 'accepted for
use'. So it is acceptable to have:

�t microtonne
mt millitonne
t tonne
kt kilotonne
Mt megatonne
Gt gigatonne

I have seen tonne and larger multiples such as kilotonne. However, I do
not regard these as anything other than commonly used non-SI anomalies.
Are you suggesting that the normal SI prefixes should not apply for
mass?

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