Pendulum plane of oscillation of a pendulum, like a gyroscope, tends to stay constant regardless of the motion of the pivot, and that this could be used to demonstrate the rotation of the Earth. He suspended a pendulum free to swing in two dimensions (later named the Foucault pendulum) from the dome of the Panthéon in Paris. The length of the cord was . Once the pendulum was set in motion, the plane of swing was observed to precess or rotate 360° clockwise in about 32 hours. This was the first demonstration of the Earth's rotation that didn't depend on celestial
Griffith Observatory the Foucault pendulum, which was designed to demonstrate the rotation of the Earth. The exhibits also included a 12-inch (305mm) Zeiss refracting telescope in the east dome, a triple-beam coelostat (solar telescope) in the west dome, and a thirty-eight foot relief model of the moon's north polar region. Col. Griffith requested that the observatory include a display on evolution which was accomplished with the Cosmochron exhibit which included a narration from Caltech Professor Chester Stock and an accompanying slide show. The evolution exhibit existed from 1937 to the mid-1960s. Also included in the original design was a planetarium under the