I've been following this exchange for quite some time now and I felt I should
intervene at this stage due to some apparent "misconceptions" about metric usage. So,
without much ado, here I go...
On Tue, 31 Oct 2000 13:33:48 Hooper, Bill and or Barbara wrote:
>...
>> From: Gustaf Sjvberg <[EMAIL PROTECTED]>
>> Subject: Re: Cribsheet
>...
>> Since the fractions around the baseunit are the most used, they deserve there
>> own names.
>
>I will agree with Gustaf that this is a reasonable argument in favor of
>using the minor prefixes (deci, centi, deka and hecto). But it is just one
>reason and there are equally good reasons not to use them.
>
What happens (really) is that the world around us goes in a "continuum" where the
usage of "intermediary" prefixes would be "in order", or at a minimum, convenient.
Besides, this is especially useful when dealing with units which are powered, like
area and volume (as someone here already pointed out). We shouldn't "ostracize" the
usage of such prefixes, simply because they do not conform to some "powers of 3"
sequencing!
Please realize that it's only when we "move from earth" or towards the "microworld"
that one may not really need to resort to more intermediary "powers" above the first
power of 3. That's actually really why we find powers of 1, 2, 3, then 6, 9, 12, etc.
(this is also valid for negative powers). So, let's not "shoot down" this convenience
for the sake of some alleged convenience (e.g. some engineering applications). Again,
I repeat, let "experts" in several fields out there choose whatever prefix they find
useful.
Quite frankly even though some here may feel some of these prefixes may be "dying" I'd
say that the reality appears to support quite the opposite (if one does not *force*
interference with marketplace's preferences, that is...)! For instance, I don't
honestly ever envision the day when Brazilians would abandon its "centimeter"
preference!!! ;-)
>> Then there is the accuracy. Should you measure everything exactly to the
>> millimeter all the time? The accuracy of +-1mm or +-1mL can't be
>> kept in all situations. That is totally unecessary.
>
>Accuracy is not an issue....
>
Actually, while Bill does have a point here that many times the showing of several
digits may not be indicative of the accuracy of the measurement in question, he also
appears to be overlooking an important aspect.
There are applications where indeed accuracy is required only to the centi, or deci
(also, the hecto and deka) precision. As a consequence measured numbers invariably
reflect that. Take for instance the cm in tailoring. Whether one shows figures as
1.52 m or 152 cm, the fact remains, one would *stop* at the figure 2. If one would
require added precision then one would add an extra digit. In such applications it
would be technically wrong to state the values as 1.520 or 1520. So, why should one
mistate measurements like this? Just because one *must* settle for powers of 3 in
presenting results???
IMHO, that doesn't make much sense.
Why burden results with extra digits which cannot be substantiated/verified and/or
*force* the use of a specific prefix to justify not having that zero there (the meter
figure in this case) when one could potentially have "consistency" problems (e.g. the
use of m and cm, if a single unit may be required - and if in this case one settles
for the meter, one could argue that it would be a burden to have figures like .06,
.16, etc all the time)?
...
>One more example (bear with me, please). My height is 181 cm. If I choose
>not to use the centi prefix I can report it as 1810 mm. If I fear someone
>will think that means a precision of plu-or-minus 1 mm (so my height must be
>between 1809 mm and 1811 mm), then I can report it as 1.81 m and the
>"problem is solved...
Bravo! That's the spirit, and coincidently that's why a significant amount of people
around the world would state their heights in the above fashion (1.81 m).
But let's not lose sight of the "enforcement" issue. There might be situations in
which it would not be advantageous to insist on the enforcement of a "power-of-3"
prefix. Imagine, for instance, the hassle it would be for the aviation world to have
to change their avionics instruments just because one ought to use 101.325 kPa instead
of 1013.25 hPa (or mbar)!
Marcus
Angelfire for your free web-based e-mail. http://www.angelfire.com
