>Hilmar,
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>>kilogram for mass (NOT for weight)
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>And it seems fundamentally silly to define mass by using weight, as in the magnetic force proposal. F = m * a. Weight = mass * gravitational acceleration. In college we always had to use lb_m and lb_f when talking about pounds-mass and pounds-force (yeah most of my engineering classes were pre-SI focus). m = F / a but this means you have to have a constant a to determine m.
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>I don't believe the gravitational force is constant enough over the entire face of the earth to make that a feasible solution. Scientists on the moon or Mars will require a different magnetic force to measure a standard kilogram. So there is no "one" definition of a kilogram using the magnetic force mechanism.
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>later update There is another infeasbility in this scheme. The gravitational acceleration between two bodies is a function of the two masses and the distance between them. So the magnetic force scheme wants to define mass as a function of mass, you can't do that.
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>>and some unit for luminescense, which I forget.
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>lumen (I think) candela is the another old measure the amount of light on a 1 foot square one foot from a candle.

Indeed, the gravitation of Earth varies by about 1% (?) in different places, which would be a million times more than the desired accuracy.

There must be more details than the article explains, but I don't know. Perhaps force is defined first (for purposes of precise measurements of the units), but I wouldn't know how it would be measured.