Re: SI Units Stumper

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

My vote is that one cannot "define" the number of atoms in a mole since it
is a derived unit.  One can establish a basis set of units, but we will always
need derived units.  If we define a unit such a a mole in terms of 
absolute numbers, we generate inconsistencies in our system of units.

For example define pi to be = 3.0

We can measure the mass of an atom via mass spectroscopy.  Therefore we
can calculate the number of atoms in a kilogram.  As our ability to
measure the mass improves the value of the mole must change to reflect
that improved acuracy.

pi = 3.14

pi = 3.14159

etc.