On Fri, 8 Jun 2001, Ma Be wrote:
> Just a small comment that perhaps you meant ... 'K for kilo',
Yes, Marcus, only "K for kilo" (and only "H for hecto") are in
the EU Directive. Please forgive my typo error, K *not D* for kilo.
The only symbol listed for deca is "da" in both the BIPM Brochure
and in the EU Directive. My preference is D for deca as an alternative
to da for a trial period, just as both l and L are for a trial period.
To add no options to the list of prefix symbol:
> >> That proposal was at once given a warm reception,
Reaction by Marcus:
> This is the part that really worries me about this committee.
> I am indeed quite disappointed in the fact that these guys appear more
> concerned about keeping the status quo than to really evaluating pending
> conceptual problems with the SI system and making an effort to fix them!
> THAT is quite disappointing indeed!...
I share your disappointment, Marcus.
> ...
> >> and we decided with no dissenting voices to make no change.
>
> Especially troublesome was the fact that that decision was unanimous!
> (SIC)
> Which gets me to asking who decides who sits in this committee.
> We might bring this overall issue to the proper channels (whoever that
> may be...). THIS state of affairs is utterly unacceptable.
Mechtly wrote:
> >Indeed! The set of prefix symbols remains defective in logic.
Marcus reacted:
> And I must concur with Gene here. I honestly believe it would be
> about time to fix some of these 'minor' problems. It's beyond me why
> BIPM hasn't yet moved on this issue at all. This shouldn't be such a
> big deal.
The CCU recommends to CIPM and on to the CGPM. Perhaps the CIPM will
not accept the CCU decision to add no options to prefix
symbols.
> >> On the other hand we did decide that something had to be done about
> >> the names "SI units" and "Units of the SI"...
> >> We decided that both "SI units" and "Units of the SI" should be names
> >> that covered the whole lot, and that when one wishes to
> >> refer to only the base and derived units without prefixes one should use
> >> the name "coherent SI units".
> >
> ? I found this resolution also somewhat confusing. Up until the
> 'whole lot' was fine, but then they really lost me with the last part of
> that sentence.
Marcus, recall that in SI there is one and only one coherent unit for each
quantity (whether it be a base or derived quantity and respective unit).
> >Changing the name "SI units" to include multiples (and submultiples) of SI
> >Units damages the concept of coherence of SI Units.
>
> On the other hand I don't follow Gene's rationale here either.
> Gene, would you please care to explain your position?
Marcus, there are only a few "coherent" units in SI (one and only one for
each quantity), but many many multiples and submultiples. e.g. only one
*unit* for length, meter (m); but many *incoherent* decimal submultiples
nm, mm, cm; and multiples km, Mm, Gm etc.
> If we accept that 'multiples' of SI units are not really *new* units,
> but rather just a *cosmetic representation* of the value to save us
> either unnecessary zeros or decimal places, why calling these SI units
> would 'damage the concept of coherence', as you put it?
The situation would be U = 10 U, U = 100 U, U = 1000 U, etc. all at the
same time for every SI Unit (each represented by U in the above equations).
Do you accept these equations as mathematically correct for U in general?
> ... apparently they, too, seem to think of prefixed SI units as
> 'non-coherent'.
The CCU decision departs from that distinction and accepts U = 10 U, etc.
That is my objection!
>
> To me, it should be this simple: prefixed units are *actually* the *same*
> unit.
Yes, only if you mean that the unit name (root) is embedded in the name
of the multiple. e.g. meter is the root part of kilometer.
> Just like cents are still dollars!
Would you be willing to give me a dollar (even a Canadian dollar) for
every cent I give you? After all cents are still dollars as you put it.
> Therefore, I am ok with calling 'the whole lot' SI units, after all.
Really, Marcus? If so, there is where we part company, unless you send
me your dollars for my cents, one for one.
Gene.
