Re: [Phys-l] FW: universal gravitation lab

[Brian Whatcott <betwys1@sbcglobal.net>]

At 12:37 PM 2/15/2007, BC, you wrote:

> Here's another from Sci. Am.  (Sept. 1963)
>
> "An inexpensive version of the Cavendish apparatus, modified to include
> electrostatic shielding, has been constructed and used successfully for
> evaluating G within 1 per cent of the currently accepted value by Sam
> Epstein of Los Angeles.
>
>
> Figure 3: Lower end of suspension
> Epstein writes: "Essentially the Cavendish apparatus is a sensitive
> torsion balance and a balance arm suspended at the middle by a slender
> steel wire.  ////

Bah, humbug!    This may be Epstein's Cavendish apparatus,
but Cavendish's Cavendish apparatus was slung initially from
 a silvered copper wire of about 10 thousandths inch diameter.
Details...details!   :-)

<http://books.google.com/books?vid=OCLC27796316&id=zrkEAAAAMAAJ&pg=RA2-PA125&lpg=RA2PA125&dq=cavendish+experiment+suspension+wire#PRA1-PA67,M1>

page 67
a silvered copper wire, 39 1/4 in long, weighing 2 4/10 grains/ft.

> bc



> Brian Whatcott wrote:
> ...
> >Now that WAS a physics setup.  Torsion to spare in fact.
> >Which reminds me that I seem to recall that Cavendish discarded
> >his first copper torsion wire as too compliant, allowing the arm
> >to hit the draft-box.
> >
> >


Brian Whatcott    Altus OK    Eureka!