SI (sometimes [unofficially] clarified as "SI-metric") is simply the current version of the metric system.
It was preceded by mks (meter/kilogram/second) and, prior to that, cgs (centimeter/gram/second), both of which are wholly metric. However, many of the units used with those systems (especially with cgs), such as erg, dyne, etc. are no longer regarded as appropriate. They have been replaced, in SI, by more practical units, with a greater degree of coherence (in some cases) and with better scaling (ergs and dynes are incredibly small, for example). If you rename an SI unit (e.g., cubic decimeter to liter), it doesn't cease to be metric. The name is simply one that is unapproved for the current SI lexicon of base and derived units. And, of course, it's entirely possible that, at some future meeting, CGPM will approve it as SI, rather than "non-SI, accepted for use with SI." Bill Potts, CMS Roseville, CA http://metric1.org [SI Navigator] >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:owner-usma@;colostate.edu]On >Behalf Of [EMAIL PROTECTED] >Sent: Wednesday, October 23, 2002 12:30 >To: U.S. Metric Association >Subject: [USMA:22900] RE: Mishmash of units at the liquor store > > >Joseph B. Reid wrote: >>>I am not sure what you mean. I said that the ml is not an SI unit. >>>Are you saying that it is or it isn't? >> >>I did not express an opinion; I merely quoted the metric bible. >>Terry is right that the litre is not, strictly speaking, an SI unit. > >With you so far... > > >>However it is "accepted for use with the International System". > >Still with you... > > > >>However, the litre is a metric unit. > >Now this is where we diverge. I regard the terms 'metric' and 'SI' as >synonyms. This is because of phrases such as 'the International System >of Units, which is the modern form of the metric system'. Am I mistaken? > >Thus I have treated 'accepted for use with the International System' as >identical in meaning to 'accepted for use with the metric system'. > >-- >Terry Simpson >Human Factors Consultant >[EMAIL PROTECTED] >www.connected-systems.com >Phone: +44 7850 511794 >
