Pendulum the pendulum could be used to measure the force of gravity. During his expedition to Cayenne, French Guiana in 1671, Jean Richer found that a pendulum clock was minutes per day slower at Cayenne than at Paris. From this he deduced that the force of gravity was lower at Cayenne. In 1687, Isaac Newton in "Principia Mathematica" showed that this was because the Earth was not a true sphere but slightly oblate (flattened at the poles) from the effect of centrifugal force due to its rotation, causing gravity to increase with latitude. Portable pendulums began to be taken on voyages
Foucault pendulum vector diagrams Foucault pendulum vector diagrams Several vector diagrams are often used to demonstrate the physics underlying the Foucault pendulum. Diagrams are provided to illustrate a pendulum located at the North Pole, equator, and 45 degrees N to show how the rotation of Earth in relation to the pendulum is observed, or not, at these locations. This is not a rigorous evaluation but is intended to convey information regarding the interaction of the two moving objects, the swinging pendulum and the rotating Earth. One of the great insights by Léon Foucault is that the time to observe a full rotation of the