How does the period of a pendulum provide data related to the Earth's size and shape?

Answer

Its period varies slightly based on local acceleration due to gravity ($g$), which changes with distance from the center of mass.

Since gravity is slightly weaker further from the Earth's center (at the equator versus the poles), an identical pendulum will swing at a slightly different rate, helping to confirm the oblate spheroid model.

How does the period of a pendulum provide data related to the Earth's size and shape?

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