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Foucault Pendulum on a Rotating Earth

What you are seeing: a pendulum's bob traces a rosette on the local floor while its plane of oscillation rotates at Ω⊕sin⁡ϕ\Omega_\oplus \sin\phi. The globe shows the suspension point at the chosen latitude as Earth turns. At the pole the rosette closes in one sidereal day; at the equator the bob just swings back and forth on a single line

Figure 1. Foucault pendulum trace on the local floor + rotating Earth with suspension point at latitude phi. Method: Boris-style symplectic step in the co-rotating frame; Coriolis term as exact 2D rotation.
latitude (deg)49
amplitude1.00
animation speed2

WHAT TO TRY

  • Set the latitude to the pole: the swing plane precesses a full turn per sidereal day (Omega sin(phi) at 90 degrees). At the equator it never precesses at all.
  • Move to a mid-latitude like Paris: the plane rotates partway each day, the rate falling as sin(latitude), the original 1851 demonstration that Earth turns.
  • Watch the bob trace a rosette on the floor: the plane of oscillation stays fixed in inertial space while the ground rotates beneath it, the Coriolis effect made visible.