Re: [Phys-l] Finishing up with that Dead Horse.

[William Robertson <wrobert9@ix.netcom.com>]

There are always "nitpicks" when it comes to the real world. That  
doesn't, at least for me, justify altering a definition. My favorite  
Einstein quote (probably paraphrased): "As far as the laws of  
mathematics apply to reality, they are not certain: as far as they are  
certain, they do not apply to reality."

Bill


William C. Robertson, Ph.D.
Bill Robertson Science, Inc.
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On Nov 8, 2010, at 9:07 PM, Bernard Cleyet wrote:

> That's why I prefer the bathroom scale definition.  Of course in  
> teaching one must explain that the weight is due to more than just  
> the presence of one big mass.
>
> bc
>
> p.s. IIRC the better gravitometers use a mass drop, which will be  
> influenced by more than the presence of earth masses (plural to  
> include mountains, etc.).    Horologists rate the quality of  
> pendulum clocks by their ability to detect the presence of the moon.
>
>
> On 2010, Nov 08, , at 16:03, carmelo@pacific.net.sg wrote:
>
> > Quoting "Rauber, Joel" <Joel.Rauber@SDSTATE.EDU>:
> >
> > > It is a valid definition IMO, not my preference to define the weight
> > > as m*g where g is
> > >
> > > M*g = GMm/r^2 direction presumably pointing towards the center of a
> > > uniform spherical planet.
> >
> > Strictly, this is still not true.
> > The direction of g is not towards the centre of a uniform spherical  
> > planet.
> >
> > Note that there is also gravitational force on the object from the
> > moon, Sun, etc...
> >
> > Some may even insist on including dark matter and dark energy. :-)
>
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