The centimetr e is virtually the ONLY currently used SI unit that is incorporates the "centi- " prefix. True, it is still recognized as legitimate SI, but we can simplify SI still further by avoiding (and eventually eliminating) the "centi-" prefix (al ong with deci, deka and hecto).
I believe it was Einstein who once said that things should be simplified as much as possible, but no further.
>if we could get rid of centimeters we'd have virtually eliminated the >"centi -" prefix. It would be an archaic part of the metric system like >"deci-", "hect o-" and "deka-". Then we might succeed in getting rid of >all four of them and h ave just the nice round steps of 1000.
This is what I mean by the bias against the centi prefix. SI *is not* based solely on the so called "rule of 1000". SI is firmly based on decimal base 10 prefixes. It is only when you get beyond 1000 times that the need for prefixes every order of magnitude becomes unnecessary. However between 0.001 and 1000 it is very convenient to have closer spaced prefixes. Yes, it it a tiny bit more complex, but lets not try to make things simple just for the sake of having everything neat, when it makes the system more clumsy to use. This should be particularly true when you are trying to convince your fellow countrymen to change from something they have known all their lives.
Also, try to remember that in most countries, metric units are part of everyday experience, and not something that is the sole preserve of the scientist, and ease of use is more important than the fact that not everything is neatly expressed in multiples of 1000.
Another poster quoted his height in both meters and millimeters. Expressing your height in mm is simply laughable - it implies a level of exactness that makes it look over-precise to someone familiar with the concept of precision (and downright nerdy to those who aren't). Do you honestly think that trying to standardize on heights in mm rather than cm will enhance a metric transition ?
The plain fact is that centi is a perfectly legitimate prefix, and the fact that it doesn't appear with most units simply means it is a not a convenient muliplier for those entities. But that shouldn't mean it should be dropped in the small number of cases where it is, just to satisfy someone's over zealous sense of symmetry (others have also pointed out the cL, dB & hPa units in common use).
And if it were to be used it w ould be called "centiamperes" (cA) not "centi-Amps".
Only if milliamps were also incorrect (they may well be technically, but milliamps & amps are more often heard than milliamperes & amperes, so I guess centiamps would be OK).
The other thing to remember is the link with the only quantity that was metric in the US right from the start, and which is familiar to all Americans: the currency. Using meters and centimeters is as easy and as apple-pie American as dollars and cents.
The variety of prefixes is one of the great strengths of the metric system. You can choose the prefix that gives you the most convenient range of values, and thanks to the fact it is based on multiples of 10, shifting between them is trivial. Don't sacrifice this just because something looks superficially neat.
(that's my 2 cents worth - or 20 millidollars if you really must insist). --------------------------------------------------------- Tom Wade | EMail: tee dot wade at eurokom dot ie EuroKom | Tel: +353 (1) 296-9696 A2, Nutgrove Office Park | Fax: +353 (1) 296-9697 Rathfarnham | Disclaimer: This is not a disclaimer Dublin 14 | Tip: "Friends don't let friends do Unix !" Ireland
