Foucault's pendulum

Here are some links to help explain  Foucault's pendulum:

http://en.wikipedia.org/wiki/Foucault_pendulum

http://www.calacademy.org/products/pendulum/

http://www.animations.physics.unsw.edu.au/jw/foucault_pendulum.html

http://www.astro.louisville.edu/foucault/

http://plus.maths.org/content/os/issue9/xfile/index

http://pbskids.org/zoom/games/pendulum/foucault.html