Of course you realise the centimetre is not a unit, neither is the millimetre, kilometre, megametre, etc. The unit is the metre. The prefixes are scaling words coming in front of the unit that replace the counting words that add zeros before or after the number. Whatever prefix you use is perfectly fine. Of course, if a particular discipline requires the prefix milli to be used, your use of centi will cause problems.
Dumbing down is a term used when one person assumes everyone is too stupid to understand proper SI units and the prefixes and assumes that everyone will understand some silly unit like AU. So literature is peppered with such a unit when in reality it isn’t understood except by some niche group. Whenever words like AU are encountered, those who may care about the subject will always ask for a translation so they hear words, like metre, that they are familiar with. If no one questions the meaning of AU, it doesn’t mean they understand it, it means they don’t care. What exactly is your work and what is wrong with using metres with prefixes that place the numbers in the range of 1 to 1000? From: Eric L Shuman Sent: Saturday, 2014-06-28 15:10 To: Harold Potsdamer Cc: U.S. Metric Association Subject: Re: [USMA:54072] Re: New supplement to the SI Brochure >The truth is, those you are trying to dumb down to by using AU don’t >understand AU either. I must be misunderstanding you, because this sounds remarkably similar to you telling me that I am bad at my job and that you can tell me how to do it. I most certainly do not "dumb down" my work, which anyone who has actually seen me work could tell you. I did not invent the AU. It is accepted for use with the SI and I use it. I also use liters and centimeters if you'd care to reprimand me for that. In the mean time, I have to insist that all the complaints on this mailing list about things not being metric enough are entirely self-defeating. ES On 27 June 2014 18:37, Harold_Potsdamer <[email protected]> wrote: Eric, I have to agree with John on this. Units only become meaningful with use. This is why SI is so superior. You can pick a prefix that puts the numbers in a meaningful range. The truth is, those you are trying to dumb down to by using AU don’t understand AU either. Harold From: John M. Steele Sent: Friday, 2014-06-27 06:40 To: U.S. Metric Association Subject: [USMA:54069] Re: New supplement to the SI Brochure But gigameters, terameters, petameters, etc. are not. That's what prefixes are for, and they continue to a range that could handle the universe. The AU is approximately 149.6 Gm, the parsec about 30.86 Pm. ---------------------------------------------------------------------------- From: Eric L Shuman <[email protected]> To: U.S. Metric Association <[email protected]> Cc: U.S. Metric Association <[email protected]> Sent: Friday, June 27, 2014 2:48 AM Subject: [USMA:54068] Re: New supplement to the SI Brochure Because the numbers are beyond human comprehension. This part of my job requires me to provide some meaningful sense of proportion. Earth is 149 597 871 km from the Sun. That's our STARTING point. Meters, kilometers, miles, furlongs, parasangs and stadia are totally meaningless on the astronomical scale. On 26 June 2014 17:45, Harold_Potsdamer <[email protected]> wrote: Why? Since the AU is fixed to the metre, why not just use the metre and its prefixes? From: Eric L Shuman Sent: Thursday, 2014-06-26 15:31 To: U.S. Metric Association Cc: U.S. Metric Association Subject: [USMA:54054] Re: New supplement to the SI Brochure Thanks for bringing this to my (our) attention! I use the astronomical unit in outreach work that I do, so this is good to be aware of. On 26 June 2014 07:36, James <[email protected]> wrote: Dear Folks, The BIPM has issued a supplement to the SI Brochure. It alters the order of the base units in defining derived units (Tables 6 and 7), it reflects the recent IAU decision to define the astronomical year as a fixed and exact number, and it makes some updates reflecting the latest CODATA, among other things. http://www.bipm.org/utils/common/pdf/si_supplement_2014.pdf Best regards, Jim Frysinger -- James R. Frysinger 632 Stoney Point Mountain Road Doyle TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
