Re: Apparent weight

[John Mallinckrodt <ajmallinckro@CSUPomona.Edu>]

On Mon, 16 Feb 1998, Rauber, Joel              Phys wrote:

> I want my fish with neutral buoyancy to be declared weightless, another
> way of saying it is that I want the rock in the water to weigh less,
> just as we measure it to be in the lab (hanging it from a pan balance
> and the rocked immersed in the water).  This would match up with the
> usual use of the term "weightless" in outer space and with what goes on
> in the space shuttle and also would explain why they train in huge water
> tanks for their extra-vehicular activities; as they have close to the
> same degree of weightlessness in the two cases, which agrees with the
> "bathroom scale" definition and is not the case with strict use of
> David's definition. 

Training astronauts in a big tank of water provides a useful but wholly
impoverished approximation of "weightlessness" without even considering
the additional experiential divergences due to viscosity and dynamic drag.
All the water does is to distribute a contact force that is usually
confined to a small area--and which, therefore, causes large localized
stresses--over a much larger area, thereby reducing those stresses to
relatively negligible values.  Our body is still, however, fully supported
against freefall, the fluid in our inner ears is not fooled, and our
internal organs are well aware that they are still supporting those that
are "above" them.  So it seems to me, that any definition of "weight" 
which would equate the experience of a swimmer to that of an astronaut is
highly misleading. 

John
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