A large ball and a small ball at the ends of a rod represent the Earth and the Moon. When the rod is pivoted around its geometric center, the system is unstable, and friction quickly stops the rotation. When the rod is rotated around its center of mass, the system is stable and rotates freely. A model of a Foucault Pendulum for illustrating one of the proofs that the Earth is rotating. A spotlight at the lecture bench serves as the sun.
Students use a tennis ball to model the earth and a ping pong ball to model the moon.
The apparent positions of stars on the celestial sphere are mapped on a large plastic sphere. Click here to return to the text based index.