Experiment of the Month
The rotation of the plane of oscillation throughout one day in August, 2000. The photos are taken with the pendulum near it maximum displacement. A graph of position on the "clock face" background for the figures, versus actual time of measurement is shown below. If the pendulum worked simply the graph would be a straight line with slope 1. The pendulum tends to slow its rotation as it passes through directions that are (mildly) preferred.