hmmm.
could the glass be slowly melting and stuff at the base shedding so that
when the weight in the glass vacuums is removed from weight calculations
it
equals 50 microgams?
also. every time the platinum-iridium weight is measured. it probably
abrades infinitesimally.
i think the latter unless time-worn methods of weighing the kilo are
sloppy
as in the first suggestion.
how to fix it? how about instead of an isotope (which can be abraded as
well) having a permanent scale that the kilogram is mounted on. in a
hundred
years that should tell us whether microabrasion was it or not.
cheers!
Doc
