Many of you have countered my argument in favor of voluntarily phasing out
the use of the special prefixes centi, deci, hecto and deka. The arguments
always seem to center on the centimetre.
But let me draw a comparison between length and mass:
LENGTH
If we wish to express the length of 152 cm without using the centi (or deci)
prefixes, we could use either 1.52 m or 1520 mm. Several of you have argued
that 1520 mm is too long and furthermore implies a precision of 1 mm which
may not be warranted.
But you miss the point when you assume I am arguing in favor of using 1520
mm. I am not. I am arguing that one may use either metres OR millimetres,
WHICHEVER IS MORE SUITABLE. If 1520 mm is not suitable (as noted above),
then use 1.52 m. Where's the problem?
MASS
Now please compare this with a similar situation involving mass. Suppose
something has a mass of 1.52 kg which is also 1520 g. Does anyone seriously
think it would be a good idea to express this in centigrams: 152 cg? That
would be perfectly valid SI usage but I think it would be highly
inappropriate. No one uses centigrams for measuring anything. Let's not
start using centi there, where it is not already in common use.
If we don't need centi for centigrams, then I fail to see why we really need
centi for centimetres. The situations are the same. (Notice I wrote "NEED",
not "WANT".)
We are unfortunately stuck with the historical fact that centi is in VERY
common use for lengths in centimetres. Fine! So we can accept the continuing
use of it there. But let's not start measuring masses in centigrams (and
time in hectoseconds or voltage in dekavolts or power in deciwatts, etc).
The base unit plus the prefixes kilo and milli will suffice for virtually
ALL common measurements (and the other powers-of-1000 prefixes will suffice
in any case where killo and milli are not large or small enough).
Centi (and deci and deka and hecto) may be WANTED by some peole, but they
are not NEEDED.
Regards,
Bill Hooper
PS I appreciate this vigorous exchange of ideas. I hope no one interprets
this discussion of our varying views to indicate that we are not all united
in promoting the general adoption of SI.
