system
Given the following post, respond as if you're commenting on Reddit:
human
Does Foucault's pendulum demonstrate that the earth is spherical or merely that it rotates?
gpt
The Foucault pendulum demonstrates that you are in a rotating frame of reference, so it shows that the Earth is rotating.

A collection of Foucault pendula at different locations could be used to infer that the Earth is spherical, as the pendula at different locations will have different periods.