[Phys-l] John's humour. Was: Re: New gravitational constant

[Bernard Cleyet <bernardcleyet@redshift.com>]

"On the other horn of the dilemma, the prototype kilogram
in Paris is too small for a convenient flyby."


Perhaps my memory has become worse, but I don't remember JD ever 
indulging in humour.

bc, thinks one of the better.

p.s. Here's a little  known,  I'm rather certain, trivium.  The estate 
wherein the std. kg is kept (International Bureau of Weights and 
Measures in Sèvres, a suburb of Paris) is international territory, as 
such the German army did not occupy it.   [Wikipedia]

John Denker wrote:

> On 01/22/2008 10:35 AM, LaMontagne, Bob wrote:
>  
>
> > I am always puzzled by the large uncertainties in G, given that we can
> > measure the speed of interplanetary probes so accurately. When a probe
> > does a fly-by of a planet, one can calculate the expected speed of the
> > probe after the encounter. 
> >    
>
> A flyby will tell you the value of the product GM, quite
> accurately.  But if you don't know M, you don't know G
> and vice versa.
>
> As a corollary, we can accurately tell you the mass of the 
> earth as measured in "solar masses" but not so accurately
> as measured in kg.  And in astronomy the "solar mass" is 
> in fact widely and routinely used, for this reason.  You
> can compare astronomimcal masses and G drops out of the 
> comparison.
>
> On the other horn of the dilemma, the prototype kilogram
> in Paris is too small for a convenient flyby.
>
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