Naked numbers are common on drawings when the units are understood. There may be a note somewhere that may read: All units in mm unless otherwise stated.
Jerry ________________________________ From: John M. Steele <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Thursday, March 12, 2009 9:01:18 AM Subject: [USMA:43708] Re: Fw: Re: Metric personal data was Re: 24 hour time None of the choices, 1.81 m, 181 cm, or 1810 mm, are wrong. Perhaps one is preferred and the other two are acceptable (if only we could agree on which). Europe, in particular, uses the centimeter in clothing sizes and I doubt you will talk them out of it. I'd like to comment on a couple of your other points to. The liter is not exactly an SI unit, but permitted for use with it. The centiliter is commonly used in Europe. The wine bottle we label 750 mL is labelled 75 cL there. I assume this is a matter of law. They require it, we forbid it. Your examples of numbers over 1000 are all quite rounded. In the spoken word 3000 miles becomes three thousan miles. "Thousand miles" becomes a new pseudo-unit and with nothing following it, in some respects, it is no longer a large number (your one counterexample becomes fifteen hundred gallons, same thing). 1810 mm does not work out so well. Back to the original example, none of the three forms is really a problem as long as the units stay attached to the number. The big problem occurs when the units are not explicitly stated, what I call "naked numbers." Naked numbers are VERY confusing unless there is a well-known norm for the units. It may be wise to establish a norm for that reason. Since the rest of the world is more metric than us, the first place to look might be how they do it, since we don't have a well-established precedent of our own (we do have a well-established precedent in spelling differences, I don't propose changing that, but why INVENT new differences) I waffle on whether meters or centimeters is the better choice, but I think millimeters has the weakest argument. --- On Wed, 3/11/09, Bill Hooper <[email protected]> wrote: > From: Bill Hooper <[email protected]> > Subject: [USMA:43700] Re: Fw: Re: Metric personal data was Re: 24 hour time > To: "U.S. Metric Association" <[email protected]> > Date: Wednesday, March 11, 2009, 10:09 PM > On Mar 11 , at 4:48 PM, John Frewen-Lord wrote: > > There I suggest using cm (sorry Pat N), as people can > then express their height verbally as, say, One Seventy > Eight - which can be interpreted by the listener as either > 178 cm or 1.78 m - both are the same value. > > > John says you can say "one seventy-eight" and in > can easily be understood to mean 1.78 m or 178 cm. However, > you can also say "one, seven-eighty" which can be > easily interpreted as 1.780 m or 1780 mm (which are also the > same value). That argument fails in showing that centimetres > are better than millimetres for this measurement. > > It really is NOT easier one way or the other. Some things > seem easier just because we're more familiar with them. > > Virtually all other prefixes in SI are multiples of 1000. > The centimetre is the ONLY commonly used SI unit that uses > the prefix "centi". (Emphasis on > "common".) As such, it is reasonable to suggest > that we drop it so we have one less prefix to bother with. > > Yes, I know that the centimetre is still an official part > of SI, but if it is unnecessary, we don't have to use > it. SI tells us what we MAY use in SI; it does not tell us > that we MUST use an particular part of it. > > It seems funny to me, too, to report my height in > millimetres. I first learned my height in metric on a > centimetre measuring rod. So I learned 181 cm and I became > familiar with that. I often find it convenient to refer to > it my height as 1.81 m but I know some people are > uncomfortable using fraction ("Why", I'll > never know!) and, therefore, they feel more comfortable with > 181 cm. But there really is nothing wrong, difficult or > awkward about using 1810 mm. > > I would agree that it would probably need to be understood > that such measurements are good only to the nearest 10 mm, > that is, the trailing zero is usually not a significant > figure. However, there are plenty of example in daily life > where we use numbers that large and we might have problems > understanding the implied precision, and they seem to give > us no trouble. Some examples (in our comfortable Olde > English units) are: > > The distance from New York to San Francisco is about > 3000 miles. > Last year I earned $75,000. (I didn't, by the way!) > The Dow John Average has fallen over 7000 points since > it's highest value. > Mt. Everest is 29,000 feet high. > I paid $113,000 for that house. > The distance to the moon is 239,000 miles. > I use about 1500 gallons of gas a year in my car. > The NFL season rushing record is over 2000 yards. > I have only about 17000 frequent flyer miles. > The speed of sound is a little over 1000 ft/s. > > If we're not turned off by these and hundreds of other > example with numbers over 1000, then why are we bothered by > my height stated as 1819 mm? > (That previous sentence is NOT merely a rhetorical > question; we ARE bothered and I'm asking if you know > why. Do you know?) > > > Bill Hooper > 1810 mm tall > Fernandina Beach, Florida, USA > > ========================== > SImplification Begins With SI. > ==========================
