Foucault pendulum calculator
Calculate the ideal turn of a pendulum’s swing plane at any latitude. Compare the signed hourly rate and full-turn period with the polar and equatorial cases.
At 51.5° latitude, the ideal swing plane turns 11.771° per hour. Clockwise, viewed from above. The rate is zero at the equator; it changes sign across the equator rather than changing the speed of Earth’s rotation.
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Turn rate = Earth rotation rate × sin φ
Viewed from above, the swing plane turns clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. At either pole it completes a turn in one sidereal day. At the equator the ideal rate is zero.
Suspension friction, an elliptical swing and external driving can move a real pendulum’s plane too. Compare observations over several swings while keeping those effects separate from the latitude-dependent prediction.