I am mystified by the constant repetition of one of the "reasons" why
millimetres are too small for measuring many common things. The
argument seems to be that because millimetres are so small, the numbers
have to be inconveniently large. And "inconveniently large" seems to
mean numbers in the hundreds.
Why are numbers in the hundreds considered inconvenient?
There are many examples of other types of measurements that we make
which normally yield numbers in the hundreds. And don't fall back on
that business that reporting something in millimetres means we must
have measured it to a precision of 1 mm. That's nonsense. It is
frequently done in technical work (where it is referred to as
significant figures) but is not often done in non-technical cases.
Here are some examples of measurements that I encounter regularly (some
metric, some Olde English):
(1)
I measure out 300 to 350 mL of water to make a cup of tea. (Yes it is a
large cup.) And "no" I did not measure it to the nearest 1 mL. I'm
lucky if it's accurate any better than 10 mL.
(2)
My height is 181 cm. (Of course I know that is 1.81 m but I usually
refer to it as 181 cm. Could I express it as 1810 mm? Of course. Does
that mean I have measured it to the nearest one millimeter? Of course
not. It probably isn't accurate to better than a whole centimetre. (I
sometimes DO report it as 180 cm or 1.8 m, and could do so with 1800
mm.)
(3)
A road trip I occasionally take is 456 miles from portal to portal.
(Yes, I also have recorded it in kilometres but that's not the point
here.) Do I try to report this 456 mi. figure as 57 furlongs because
"miles is too short and it gives me a number in the hundreds which is
too big"? No! Is my 456 mile figure intended to show that it has been
measured with a precision of plus or minus 1 mile? No! Those couple
short side trips for gas and food probably spoiled that precision.
(4)
I don't know my weight in pounds but a figure of 165 pounds would not
be far off, I think. Should I measure it in stone so it wouldn't be a
number over a hundred? No! Do I care if the precision is not exactly 1
pound? No!
(5)
My electric grill instructions tell me to pre-heat the grill to between
550 and 650 �F to broil steaks. Do I try to convert this to
"kilodegrees-F" so that the numbers won't be so big? Of course not. I
am quite accustomed to cooking temperatures in the range of several
hundred degrees. I know that these figures are not precise to the
nearest one degree-F because they are telling me that anything within a
full hundred degree range is OK (and frankly I can get a properly done
steak with the grill at only 400 �F).
(6)
In Germany (where I visit occasionally), sandwich meats and other foods
are sold by the 100 gram. No one expects the meat to be weighed out
exactly to the nearest 1 g. And people think and talk about the
quantities in increments of 10 grams or even 50 grams or more: "Do we
need 500 or 600 grams of leberwurst? Well maybe we'll get 550 g."
In all the examples above, whether in Olde English or SI metric, people
routinely work with numbers in the hundreds with no difficulty at all,
and they aren't bothered in the least by the fact that the precision
might not be just "plus or minus 1" of the unit in question.
I maintain that there is nothing wrong with using units that result in
values in the hundreds. Anytime someone argues against a use of a
particular unit because it leads to a number in the hundreds, his or
her argument is simply false. Just think of the many measurements we
all use already, with numbers in the hundreds, with no difficulty at
all.
Regards,
Bill Hooper
Fernandina Beach, Florida, USA
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Go Metric America! Or get left behind!
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