Re: SI units

[Joe Darling <jdarling@emh1.otc.cc.mo.us>]

The candella is still listed in the 77nd. Ed. (1996-1997) of the
CRC Handbook of Chemistry and Physics, page I20, with its definition
unchanged since the 14th CGPM in 1971.

I'll have to remember the millikilogram.  I have always assumed,
and perhaps someone can verify, that the definition of the gram
long preceded the effort to establish the MKS or SI system.  They
were also unable to convert us to a "metric" time.  I often ask my
students if they are so unwilling to give up the English or BE system
of units, what is their unit of mass.  No one has gotten this yet
unless I make the mistake of passing out my study guide first.  I 
hope the resulting discussion helps to emphasize the difference
between weight and mass.

I believe we have a number of participants from metric countries.
I also believe they announce their weight in kilograms instead of 
newtons, an uncomfortably larger number.  But I tell my students that
they are really announcing the mass, which would be unchanged if they were
suddenly transported to the Moon.  Is there any scientific justification
for this practice?  Am I creating any misconceptions in the minds
of my students?

Joe D. Darling   jdarling@emh1.otc.cc.mo.us
Instructor of Physics and Physical Science  
Ozarks Technical Community College
1020 East Brower   Springfield, MO 65802
(417) 895-7907   (417) 895-7085 FAX

On Mon, 23 Feb 1998, James Mclean wrote:

> Chuck Britton says:
> > The only SI units that are NOT named after people are the second, meter and
> > kilogram. (I guess this means that the liter and the mol are not truly
> > correct SI units?)
>
> It just occurred to me: if the basic mass unit in SI is the kilogram,
> should we really measure smaller masses in 'millikilograms'?
>
> On a very slightly more serious note, my 1992 CRC gives both the mole and
> the candela as SI base units.  Is the candela still recognized in 1998?
>
> -- 
> --James McLean
> jmclean@chem.ucsd.edu
> post doc
> UC San Diego, Chemistry