Pendulums generally swing back and forth in a single
plane fixed in space. On Earth however, if the path
of a pendulum's swing is traced out over time, the orientation
of the plane appears to change. This provides evidence
for Earth's rotation because it shows that Earth is
rotating underneath the unchanging orientation of the
This animation shows two views of a pendulum swinging
over the North Pole. The drawing shows the path traced
out by the swinging pendulum.
the image to see the animation.