Physics / Earth
Foucault pendulum
The Earth's rotation turns the swing plane: precession ∝ sin(latitude).
What happens
The pendulum swings in a fixed plane; it is the Earth that turns underneath. At the pole the swing plane makes a full circle per day, at 45 degrees it takes about 34 hours, at the equator it never turns: precession goes as the sine of latitude. Drag the latitude, use the preset buttons, and speed up the rotation to see it clearly. A ring of brass pins stands just inside the swing's reach: the turning platform carries each one into the frozen swing plane and the bob's pointer knocks it flat - the Panthéon staging, driven by the actual sweep, not a script.
Equations used in the module
Equations Ω_precession = Ω_Earth sin φ one turn in 24 h / sin φ (32 h at Paris) T = 2π √(L/g)
