system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How does Foucault's Pendulum work? How does it actually prove that the earth rotates?

I cannot understand how the pendulum shifts its plane of oscillation since the base which **holds** it also rotates. I can only think of it happening if only we hang a piece of string from space to the north pole.
gpt
Since the rope is not rigid, it doesn't impart enough force on the bob to stop it from deviating off of it path as the earth spins.

You can see this for yourself.  Get a pendulum, and put it on a lazy susan or a merry go round.  You will quickly see the path deviate from going straight back and forth.

The other thing about a Foucault's Pendulum is it doesn't just deviate...it deviates exactly as predicted given the earth's size and force of gravity and the pendulum's latitude.