Just a minor comment to emphasize the fact that the liter is actually IMHO just a convenient "nickname" for the dm3, and also a way to "cheat" the prefix system somewhat. For example, if one kept the "pure" m3 one would not be able to refer to centiliters. Evidently the mL could also be replaced by the cm3, etc...
I see a similar "principle" here applying to the ha as well, i.e. that this again is just another way around the difficulty with finding suitable/convenient "sizes" for surface areas. OBS.: I evidently would rather use "the real thing", but I must be realistic as well and starting to use dm3, cm3 and the likes may not be at the right time yet... Marcus On Thu, 28 Mar 2002 12:31:57 RobertHB wrote: > 2002 March 28 >What is an SI unit? >In 19104 Bill Hooper says "The litre is not an SI unit." Well, yes it is. >This long-time problem arose even more strongly with the millimetre. Could >we >really get away with telling people that the millimetre is not an SI unit? >We would >be laughed out of town. Or people would say to hell with SI. > >The CCU has treated this issue. Any unit, with a prefix or not, formed from >the >base and derived units is an SI unit. Accordingly, Section 2.2 of draft 5 of >SI10 >now says > > "The term SI units includes the SI base units, the SI derived > units, and all units formed from them using the SI prefixes. > >The coherent property applies to units without prefixes. > >The second paragraph of Section C.1, called C.1.1 in draft 5, has the word >"coherent" added to the text to read: > > "A great advantage of SI is that there is one and only one > coherent SI unit for each physical quantity." > >Furthermore, what is the meaning of a requirement that SI units be used? >Section 3.3.2 Units in use with SI says: > > "Compliance with this standard includes the use, as needed > and convenient, of certain non-SI units listed in Tables 6 > and 7, as well as all the SI units, including the multiples > and submultiples." > >This makes it now easier to promote SI units. > > Robert Bushnell, PhD PE > meteorologist > chair ASTM E43 on SI > > See Dave Matthews Band live or win a signed guitar http://r.lycos.com/r/bmgfly_mail_dmb/http://win.ipromotions.com/lycos_020201/splash.asp
