---------- Forwarded message ----------
Date: Thu, 28 Jun 2001 12:27:33 +0100
From: Ian Mills <[EMAIL PROTECTED]>
To: Gene Mechtly <[EMAIL PROTECTED]>, "Martin, Peter" <[EMAIL PROTECTED]>,
Quinn <[EMAIL PROTECTED]>, "Taylor, Barry N." <[EMAIL PROTECTED]>
Subject: Re: Symbols for SI Prefixes
Dear Gene,
I am sorry to have been so slow in replying to your last email. For various
reasons it did not get an immediate reply, and then it got lost in the press
of other matters that I have had to deal with.
However I have little to add, in reply to your questions, to the information
that I reported in my last message to you. The proposal for the alternative
symbols D, H and K to be allowed in parallel with the existing symbols da,
h and k was discussed, and the decision was taken to make no change in the
current rules for prefixes. We did not actually vote because the decision
was essentially unanimous. The reason for making no change was that the
CCU is strongly of the opinion that making many small changes to the SI
will lead to confusion, and hence that it is better to make no changes
unless we feel the case to be overwhelming. In this case the meeting did
not feel that the case was so strong. The CCU receives many proposals for
small changes to the SI, and generally these are not accepted, even though
many of them have some logical support.
It is not for me to detail who spoke which way on issues of this kind. The
members of the CCU are there as representatives of their supporting
institutions, such as the NIST, the NPL, the IUPAP, and the IUPAC; they
are not present in a personal capacity. Thus you should lobby your
representative from one of these bodies if you wish to express a view.
In my last message I also mentioned the problem of the two alternative names
"SI units" and "units of the SI", which have been given different meanings
in the ruling of the CCU in recent years. In this case we again considered
the alternative of making no change, for the reasons mentioned above, but
we felt ourselves forced to make a change for two reasons.
First, it is a violation of the English language to attach different meanings
to the phrases "SI units" and "units of the SI". That was put to us by
several people, and it seemed a compelling reason for making a change.
Second, it was also put to us that most ordinary folk, indeed almost all folk
whether or not they are trained scientists, find it extraordinary to be told
(for example) that the kilometre, the centimetre, and the millimetre are
not SI units. It seems to violate common understanding. We therefore decided
to make the change that I believe I described briefly in my last message,
namely that one should use the phrase "coherent SI units" to refer to only
the SI base units and the coherent derived units (i.e. those without prefixes,
excluding the exceptional case of the kilogram). Then the phrases "SI units"
and "units of the SI" may both be taken to refer to all the units with or
without prefixes.
I am sorry to disappoint you.
With my best wishes, Ian Mills
---------------------------------------------------------
from: Ian Mills, President of the CCU
Department of Chemistry
University of Reading
Reading RG6 6AD U.K.
phone: +44 (0)118 931 8456
fax: +44 (0)118 931 1610
email: [EMAIL PROTECTED]
web: http://www.chem.rdg.ac.uk//dept/staff/phys/imm.html
