THE Léon Foucault
Foucault originally studied to become a doctor, but then finding out that he had hemophobia he became a physicists. He also had a curious and creative side... Most of his experimenting was done at home. His work was done in collaboration with other scientists of the day.
The Foucault Pendulum (How it Works)
This was an invention created by Leon Foucault, that demonstrated the Earth's rotation. How it works is that a tall pendulum swings freely in any vertical plane. The plane of swing appears to rotate relative to Earth. The wire needs to be long as possible.
Why Was His Invention So Significant?
Without his main invention we wouldn't know about the rotation of the Earth! Just this one thing gives us much information about Earth, and it helps finding out things about Earth as well.