Hi Randall,  Thanks for this great artical.   Ted
----- Original Message ----- 
From: "Randall Peters" 
To: 
Sent: Monday, February 25, 2008 12:15 PM
Subject: pendulum types


> With all the attention to non-simple pendulums of late, perhaps some 
> readers will be
> interested
> in the following old one of my webpages:
> http://physics.mercer.edu/petepag/pend.htm#torsion
>  The 'pendulum' titled 'tiltmeter' is an example of a system for which the 
> influence of
> earth tilt can be greatly 'magnified'.as the operator changes the 
> orientation of the torsion
> wire, causing approach toward a critical value.
> A system similar to it was used by one of my students in the early 1990's 
> to study
> chemisorbed
> gases on metals.  With it he was the frist person to observe (accidently) 
> earth hum having
> frequencies below a few milliHertz.  There was much, much geoscience 
> interest in later,
> similar earth oscillations at mainly higher frequency, starting about 
> 1998.
>    Randall
> 

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