> Of [EMAIL PROTECTED] >For us who know the technical stuff of SI that comes from CIPM >through BIPM, we can say litre is not SI where we mean that it is >not coherent
I have a much more simple test. When I say something is not SI, I mean merely that the BIPM says it is not SI. This prevents me being sued for making false statements, and allows me to say to engineers "tables 1 to 5 list all the SI components that you need" >As for the general public we should not be so stupid as to say >litre and millimetre are not SI. I am not stupid and I do not enjoy reading such an implication. If somebody asked me if the millimetre and litre are SI, then I would tell them that the millimetre is SI but the litre is not. However, my experience of the general public is that the term of choice is the undefined term 'metric system' rather than the strictly defined term 'SI'. So the scenario that you are suggesting appears unlikely to me. I can easily imagine a scenario whereby a member of the public says that the litre is 'metric'. I cannot imagine myself challenging that. There is no authoritative reference that defines 'metric'. It appears to be inconsistent colloquial usage. Most people will probably say that the litre (BIPM table 6) is metric but the hour (also table 6) is not. However put hour with km as in 'km/h' and the whole thing is regarded metric. It just goes to show that people use fuzzy logic. Some people may argue about whether the quintal is metric. This unit is equal to 100 kg and commonly used in agriculture. It is not listed by the BIPM at all. Conversely some units listed in BIPM tables 6, 7 and 8 such as 'day' and 'nautical mile' (BIPM table 8) would not be regarded as metric even in association with other units. There are not many occasions where a definition of metric it is at the heart of the debate. The issues I encounter are much more mundane such as "Is petrol in the UK sold in imperial or metric units?". I would say "it is sold in litres" (avoiding the issue) or "It is sold in metric units" (i.e. using colloquial terms). I hope that makes sense.
