Re: Gravitational constant

* Uncle Al writes:

> The U/Wash experiment used a Pyrex plate of nominal density 2.23
> g/cm^3 and stainless steel attractors of nominal density 7.98 g/cm^3. 
> One could imagine obtaining tighter bounds using a precision machined
> much stiffer (and therefore thinner) single crystal alumina plate,
> d=3.965, and precision machined HIPed tungsten attractors of nominal
> density 19.35 g/cm^3.

The keyword is 'nominal'. The problem with attractor masses is that it
takes some care to manufacture them to the required homogeneity and
precision machining therefor is only half of the story.

> G is a particularly nasty measurement for the weakness of the
> interaction and the impossiblity of shielding external gravitational
> noise (tides, rain, passersby).

Indeed. 

-- 
Space - the final frontier