Re: SI &c., eh?

[Leigh Palmer <palmer@SFU.CA>]

At 11:37 -0700 8/29/99, Daniel Schroeder wrote:

> Leigh:  What unit of (barometric) pressure is used in weather reports
> up there?  (My guess is bars or millibars, like my bicycle tire gauge,
> but official SI would require pascals or kilopascals.)

Don't bet money on it. That's one of the successful unit changes.
Atmospheric pressures are reported in kilopascals (101.3 kPa = 1 atm)
in Canada. Tire pressures are guage and are customarily in psi. (I had
a bicycle tire guage from somewhere in Europe calibrated in units of
kilograms per square centimeter!) Bicycle gearing is denominated in
two different ways according to convention. In English Canada we use
"inches". The inch-gear of a bicycle is the diameter of a wheel which
would roll the same distance in one revolution as the bike moves in
one revolution of the pedals. I don't know what convention is used in
French Canada (the only place in the world where STOP signs don't say
"STOP"), but in France the gear is quoted larger than this by a factor
of pi (and is called "developpement"). Of course it quite sensibly
represents the distance traveled by the bike in one pedal revolution,
and is given in centimeters.

Our produce is sold by the pound, but our deli stuff is sold by the
hundred grams. Often both types of units are used on signs in the
stores (English Canada). Our packages (in French and English) are all
metric, with rare Imperial equivalents included, but there are a lot
of 454 gram packages around! Gasoline is always sold in liters, but
our old (Imperial) gallon was twenty percent larger than the US
gallon so we are well rid of it. Gasoline is about the same price as
it is in the US when all conversions are taken into account, but our
metric dollar (the "looney") is about two thirds the size of a US
greenback dollar ("buck", "smacker", or "simoleon").

Pronunciation is another bug here. The CBC has a policy of pronouncing
"kilometer" correctly (i.e. the SI English way: kil' o me' ter) in
English, but many Anglophone broadcasters still pronounce it the odd
British way, ki lah' meh ter. Physicians here, even those who know it
is incorrect, often pronounce "centimeter" in the affected British
medical manner: sahn' ti me ter.

At 13:18 -0700 8/29/99, paul o johnson wrote:

> Daniel Schroeder wrote:
>
> > Of course, the Official SI Unit of Temperature is the kelvin (lower-case,
> > please, and without "degree" in front).  I wonder if the SI zealots who
> > police journals and textbooks are listening.  If so, I challenge them
> > to banish all temperature measures but kelvin from their everyday
> > vocabulary.
>
> Dan's comment reminds me of one of the reasons why I'm so curmudgeonly in my
> middle age. I just can't go along with a couple of the changes the boys back
> in the smoke-filled room in Paris made.
>
> One was changing the name of the system of units from Metric to SI. If this
> was done solely to pacify the French, which many francophobes claim, it was a
> great disservice to millions of US students who, having heard praises to the
> metric system all their young lives, are told in school that it's called the
> SI system even though it's still all metric. I hope my students forgive me
> for leading them astray by continuing to refer to it as the metric system.

How 'bout cgs and MKS?

> The second change was even more baffling--to change degrees Kelvin to
> kelvins. Lord knows we should honor as many of the earlier greats as we can,
> but why give Lord Kelvin this exclusive honor and leave Brothers Fahrenheit
> and Celsius saddled with degrees? I just can't go see it.

You can still use degrees Kelvin. Just think of them as *honorary*
degrees. No one feels saddled with an honorary degree.

> Will my students suffer in future years if they use these outdated terms I am
> teaching them? Tough.

I've got other peeves: Replacing the excellent unit "mho" and its
typographically challenging but amusing symbol with the "siemens" and
its ill-chosen symbol, adopting the "hertz" when a perfectly good
unit existed, and then compounding the felony by changing "curie" to
"becquerel", an impractical unit from any point of view.

One good thing they did do. They systematized radiometry and
photometry once and for all time. However, I can never remember the
proper names and definitions of all the quantities. I always need to
consult a reference whenever I have to teach that stuff. The standard
candle was pretty lame, one must agree.

&c.

Leigh