A simple geometric model for visualizing the motion of a Foucault pendulum

A geometrical model of the Foucault pendulum is presented, which corrects some common misconceptions concerning the ``fixed'' plane in which the pendulum oscillates. It is shown visually, and by the use of metric geometry, that the direction of oscillation of the pendulum undergoes a parallel displacement as it moves along the Earth's spherical surface. However, this direction of oscillation is not fixed relative to the stars.