A simple device built to demonstrate the rotation of the Earth is called a Foucault pendulum. It was invented by the French physicist Léon Foucault in 1851. The Foucault pendulum consists of a long, heavy pendulum suspended from a fixed point. As the pendulum swings back and forth, its plane of oscillation appears to rotate slowly over time due to the rotation of the Earth.
The rotation of the Earth causes the plane of the pendulum's swing to gradually shift relative to the Earth's surface. This effect is a result of the Coriolis force, an apparent deflection that occurs when an object moves in a rotating reference frame. By observing the changing direction of the pendulum's swing, one can deduce that the Earth is rotating.
Foucault pendulums are often displayed in museums or science centers as educational exhibits, allowing visitors to witness the rotation of the Earth in a visually compelling way.