Watch the Earth Rotate: The Foucault Pendulum

"The Earth's rotation is too slow to observe directly - no experiment can show it."

Visit a science museum or planetarium with a Foucault pendulum - a heavy bob on a long wire, swinging over a marked circle. Don't touch it (any push adds motion of its own). Watch or photograph the plane of the swing against the floor marks over an hour or more, and compare with the rate your latitude predicts.

The swing plane keeps its orientation in space (inertia) while the Earth turns under it, so it appears to rotate relative to the floor at 15.04°/hour × sin(latitude). At the poles: one full circle per day. At the equator: none. At 45° latitude: about 10.6°/hour (a circle in ~34 hours). At the Panthéon in Paris (48.9° N): about 11.3°/hour clockwise - a full circle in ~31.8 hours, exactly what Foucault measured in 1851.

Léon Foucault, 1851. The first public demonstration was in February 1851 at the Paris Observatory; weeks later he hung a 28 kg bob on a 67 m wire from the dome of the Panthéon - the first experiment to give simple, direct evidence of the Earth's rotation. In 1852 he followed it with the gyroscope. Foucault pendulums are now a staple of science museums worldwide.

You cannot feel the ground moving at up to 1,670 km/h, but you can watch it: the pendulum's plane is fixed in space and the floor rotates underneath. It is the same 15°/hour that the flat-earth community's $20,000 gyroscope 'could not accept' in 2017 - the museum's free exhibit and their most expensive instrument measure the same rotation.