NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2010 Sep 12, 09:28 -0700
I am attaching a Youtube video of the Foucault Pendulum in the Pantheon in Paris. The pendulum swings back and forth above a scale of hours. As the day go by the pendulum appears to change its swing and passes over the markings on the scale on the floor indicating the time. Note that the hour marks are not 15 degrees apart as they would be at the north pole but are only 11.3 degrees apart, the sine of the latitude of the Pantheon (48 degrees 51') times 15.04 degrees per hour that the earth rotates in space. This is easier to see at the end of the video where there is a 89 degree gap between the "24" and "0" marks since the pendulum only appears to change its swing by 271 degrees in twenty four hours. They have to reorient the pendulum in the morning and start it swinging in the right direction for the new day.
This is a clear example of "earth rate precession" that effects directional gyros such as the one in Earhart's plane. But since she was at the equator the precession would have been zero.
gl
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