Jesse, The only "coherent" unit of mass in SI is the kilogram, not the gram or the tonne. As you probably know, in the older cgs system of units, gram was the coherent unit of mass.
The metric ton or tonne is nothing more than a sometimes convenient multiple of the kilogram by a factor of 1 000, used at the expense of coherence. Both tonne and Mg are not coherent with the set of SI Base Units; meter, kilogram, second, ampere etc., nor with any of the coherent SI derived units. Therefore, in my opinion, it is best to avoid tonne and Mg for calculations involving mass and other quantities. To preserve coherence, I use such expressions as 1.00 E-3 kg and 1.00 E+3 kg to express values of mass. This also avoids deprecated "double prefixes"; such as kkg. In this USMA Forum in past years, we have worked through several cycles of proposed new names and symbols for the kilogram to dispose of this anomaly of an SI Base Unit containing the prefix kilo. This inconsistency remains. Gene. ---- Original message ---- >Date: Thu, 24 Jan 2008 19:06:08 -0800 (PST) >From: "Ziser, Jesse" <[EMAIL PROTECTED]> >Subject: [USMA:40210] Tonnes >To: "U.S. Metric Association" <[email protected]> > >Interesting. I've never seen anyone use Mm before. Kind of like Mg. > >On that subject, now that I think of it, I've been wondering for years why the >unpleasant little >detail of the tonne hasn't been ironed out yet in *any* countries as far as I >know. I've searched >the web and found nothing suggesting that anyone is even considering >"switching" from tonnes to >Mg. Why the heck not? > >If I may ask, what is the opinion of you wise folks on this? >...
