The Foucault Pendulum is an experiment to demonstrate Earth’s rotation, named after French physicist Léon Foucault. The Foucault pendulum is the first simple and direct evidence of the Earth’s rotation. It is a straightforward experiment: a huge pendulum is allowed to swing throughout the day, and it will slowly rotate because of Earth’s rotation.
For any flat-Earthers, the Foucault pendulum is one of the facts that must be discredited. They would invent various “explanations” to reject the conclusion of the experiment. They are wrong. Anyone is free to repeat the experiment, and when done correctly, it will result in a consistent result and in line with expectations.
To answer the result of the Foucault pendulum, the victims of flat-Earth are divided into two camps:
The ‘fake’ camp will discredit the Foucault pendulum as fakery, and it rotates because of manipulations.
They would “explain” that in all Foucault pendulums all around the world, there are physical or electromagnetic mechanisms to make it swinging all day. They attribute the rotating motion to this mechanism. They are wrong. These mechanisms are there only to keep the pendulum to swing, not unlike the original pendulum, where it had to be restarted several times a day because at some point it would lose momentum and stop swinging.
The ‘genuine’ camp acknowledge that the Foucault pendulum is genuine, but they don’t accept that Earth’s rotation causes it. They would invent ad-hoc hypotheses to “explain how it works”. Their assumptions are easily refuted, and they can’t explain the rotating motion of the Foucault pendulum.
Sometimes, they attribute the Allais effect as the cause. It is an anomalous phenomenon whenever a solar eclipse occurs. This anomaly is still questionable, but we know it is not evidence of a flat-Earth.
The Foucault pendulum will rotate with an angular velocity of 360° × sin φ / day, where φ is the latitude of the pendulum’s location. It rotates clockwise in the northern hemisphere, and counter-clockwise in the southern hemisphere. There is only one explanation why the Foucault pendulum works that way: the Earth is a sphere, and it is rotating.
Illustration: Foucault Pendulum by Daryl Clark.
- Foucault pendulum – Wikipedia
- How do flat Earthers explain the Foucault pendulum? – Quora
- Allais effect – Wikipedia