Very educational, Joe. In principle I'd have no beef with this piece from SA. However, there are some remarks that I feel should be made on this seemingly never-ending controversy (c vs. m).
On Wed, 24 Jul 2002 09:24:36 Joseph B. Reid wrote: ... >South African Metrication News, 1978-07/08 wrote: >1. One of the most important aims of the SI is the simplification and >rationaliation of units, both for measurment and for use in calculations... > 3. If the centimetre is interposed between the millimetre and the metre >it has several disadvantages: > (i) It destroys the simplicity of the system, ? I beg to differ! Nothing is "destroyed" by the use of ANY SI prefix, otherwise we simply wouldn't have them. Again, the business of using prefix was created for *convenience* purposes. We gain nothing by insisting or condemning people who *exercise a preference*!!! The SI system would continue to be simple, centi, deci, deka, whatever! True, it may be "natural" for many to move decimal points in increments of 3. But this is probably mostly due to the fact that we "separate" big numbers in groups of 3, and this "habit" (or rule) has NOTHING to do with the SI system. > (ii) It makes it impossible to use the *groups of three* method to >change from centimetres, say, as the gap is in the wrong place viz: >76 322 cm = 763,22 m >But there will be a tendency - using the *gap* theory - to make the answer >76,322 m (a tenfold error). Two points: 'impossible' is a strange adjective here and is applicable only if one turns this business of 'groups of 3' as some 'method' indeed (but there is nothing in SI books that hints at turning this as some "biblical dogma"!). And secondly, this kind of 'tendency' may occur, no argument here, but it's not because we have this "risk" that we should condemn a specific prefix. Attentive professionals, especially those who are used to dealing with these prefixes, would normally NOT fall pray to this 'tendency' and would handle these numbers properly without much difficulty (I being a typical example... :-) ). > (iii) It is universal practice in technical drawings to use >millimetres only. I dispute such 'universality'! In Brazil and other European countries this is clearly NOT universal! Actually, what we use there is not even the cm per se, but rather the meter itself *to the centimeter accuracy*! I'll explain: 1.72 m <- In other words, dimensions are quoted in meters with the decimal point and all all the way to the centimeter decimal point (the 2 here). If more accuracy is required or used, then there would be a 3rd digit, as in 1.724 m, for instance. > If this practice is employed all that has to be done is >to write *all dimensions in millimetres* at the top of the drawing and then >leave all symbols off each dimension - a tremendous saving of time and >ensuring that errors in transcription are avoided. There is indeed economies of scale savings if one stuck to a specific prefix all across the board, so to speak. No argument here. Therefore, it is possible that this does take place especially when one uses IT data and electronic transfers of info. For this I'd certainly encourage and accept this "standardization". But the fact of the matter is people will continue to use the cm not only in casual conversation and will resort to mm accuracy when necessary/required. This practice will certainly (here I'll play prophet a little bit... ;-) ) never die. I'll repeat what I tired of saying before: (please, read my lips! :-) ) This is NOT a big deal. So, let's please NOT turn this into one. We, cm users, do NOT care about whether one wants to make use of the mm. We would and will gladly comply, but just don't *force* us to, so please cut us some slack, please?... We just are puzzled by mm users "fixation" with this. With all due respect (no offense is intended here) these individuals are mostly metric newbies who unfortunately have not had much experience with the metric system yet, so really I don't think you should be in the business of imposing specific metric usages onto us. We have NO difficulties or beef with using the cm, nor with ANY other SI prefix and we feel we never will, period! We have enough exposure to these to appreciate their diverse usage. And I'm not talking just for myself but also on behalf of all those in "old" metric countries. I'm confident you'd certainly hear a similar opinion from them, too! Where the use of a specific prefix would help contribute towards more efficient use of resources and all you'll definitely see us cooperating, but, by golly, don't make us feel like we're "odd" or doing something wrong. This would be utterly unwarranted! ... > 4. It should be noted that the objection to centimetre is confined to >its use as a linear measure. When raised to the second and third powers, as >in areas and volumes respectively, it is necessary to employ square >centimetres and cubic centimetres to render the steps betweeen successive >multiples of area and volume, practical ones. Aha! Some acknowledgment, thank you! This is the crux of the issue: *practicality* (plus the required accuracy, too, evidently, or ability of instruments to provide a read out to the specific needed decimal place). This is also why the SI system should NEVER get rid of these intermediary prefixes. They do have their place in facilitating people's lives in some applications, like when length dimensions are powered to 2, 3 or more. > 5. In South Africa the centimetre is used in the clothing and textile >industries and therefore also for related dimensions of the the human body. >It should, preferably, not be introduced elsewhere. I'd agree but with caution as I'd not like to restrict people's businesses and all if they by any chance felt that they would benefit by using the centi prefix. > 6. If the centimetre were given equal status with the millimetre we >would have the situation where some people would specify the dimensions of, >say, a piece of paper in centimetres and others would specify its >dimensions in millimetres. This would be very confusing and would defeat >one of the main objects of introducing a univeersal language of >measurement. Where this is warranted, fine, you'd find no opposition here. > 7. There is no doubt that the preference that many people have for the >centimetre is merely aother throw-back to the imperial system - it is the >sub-multiple of the metre that is most closely relatred to the inch - and >such people naturally tend to use it in all applications where the inch was >previojsly used. This "cross-section" of people is, however a dimnishing >one. I don't think so! Some countries never used the Anglo-saxon inch before, but something else. Besides, the use of cm is mostly driven by practical matters. Again, I don't foresee the cm disappearing EVER. > 9. The SI, if it is to retain its simplicity and its coherency, must >employ as few sub-multiples and multiples as possible. ? The coherence aspect of the SI system has NOTHING to do with prefixes which are just convenient tools to render the writing of measurement values with less or more decimal places when needed. Ideally people should adopt the use of powers of 10 when meeting with several measured values that make use of a diversity of prefixes and handle them separately. Example: 4 m/s x 8 cm/hPa / 4 daN = 4 x 8 / 4 x 10 to (-2-2-1) m/s x m/Pa / N etc By adopting this simple procedure and care one would never have trouble with prefixes no matter how odd they may be, 3s, 2s, 4s, who cares? > Nobody wishes to >interpose centigram between milligram and gram, for example, nor >centinewton between millinewton and newton, nor centivolt between millivolt >and volt, etc.,... To my knowledge I can't see ANY application where the use of centi in the above examples would be an advantage, therefore, I can't fear or expect this to happen. But, IF it ever did, I'd not lose my sleep over (just like I don't when my fellow Canadians prefer to say they're 185 cm tall instead of the usual - for me - 1.85 m)!!! ;-) Marcus Is your boss reading your email? ....Probably Keep your messages private by using Lycos Mail. Sign up today at http://mail.lycos.com
