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Eratosthenes and plumb bobs

On Tue, 05 Jun 2001 18:40:03 -0500 brian whatcott <inet@INTELLISYS.NET> writes:
> At 15:26 6/5/01 -0700, Ken Murray wrote:
> >My students would like to measure the size of this planet with a
> >length-of-shadow measurement (a variation on Eratosthenes's
> observations).We would measure the shadow angle of a vertical metre stick
> /snip/
> >Ken Murray
> It's an interesting detail of the experiment to decide how the
> verticality of the sun stick should be verified.   I've heard
mention of a windshielded tray of water at the foot,  using the
eye's perception of the straightness of the stick
> compared to its reflection.  A windshielded plumb bob seems
to have possibilities too.
> brian whatcott <>  Altus OK Eureka!
I've heard of a windshield on a car and on a motorboat.
But ? ..... a windshielded tray of water?  
 and a windshielded plumb bob???
Did Eratosthenes have a windshield on his vertical stick?
Has anyone ever measured the deflection of a plumb bob
as a function of varying wind speeds??  Is it a viable
project for a student science fair?   Is it necessary to perform
such experiments during a tornado or hurricane? 
If so, is a windshield wiper of any help at such times?
Herb Gottlieb from New York City
(Where builders use plumb bobs without windshields)