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From: bob@islenet.UUCP (Bob Cunningham)
Newsgroups: net.physics
Subject: Re: Weird Gravitational effects at Lake Delton Wisconsin
Message-ID: <1516@islenet.UUCP>
Date: Thu, 22-Aug-85 17:28:17 EDT
Article-I.D.: islenet.1516
Posted: Thu Aug 22 17:28:17 1985
Date-Received: Mon, 26-Aug-85 01:28:10 EDT
References: <974@sphinx.UChicago.UUCP>
Organization: Hawaii Institute of Geophysics
Lines: 26

Currently, instruments used in gravity surveys are sensitive to about one
part in 10^8.  Gravity prospecting is commonly used as a reconnaissance
tool in oil exploration -- it's often cheaper than a seismic survey --
though it's usually employed as a secondary method for mineral exploration,
although recently it's become more popular for detailed follow-up of
magnetic and electromagnetic anomalies during integrated base-metal
surveys.

Even a quick survey (several neighborhood sites for reference + a few
measurements at the point of interest) would surely detect objectively any
thing like what you've observed.  Still, it wouldn't be cheap.  Several
days (minimum) of a well-trained crew of several people.  (Contact any oil
company for details and a cost estimate :-).  Having well-calibrated
instruments is a must.

On the other hand, if the anomaly (anomalies?) are as pronounced as you
suspect, they're probably detectable using a simple pendulum (accurately
measuring period, using the total number of cycles over a period of several
hours), or some form of torsion balance.  The precision would be much less
than that of modern gravity meters, but probably sufficient to detect (or
fail to) major changes in the gravity field up by the lake.  The time,
effort and expertise involved would be roughly equivalent to a good high
school level science fair project.
-- 
Bob Cunningham  {dual|vortex|ihnp4}!islenet!bob
Hawaii Institute of Geophysics