Earth’s Rotation Day is observed worldwide every January 8 to commemorate the discovery made by French physicist Léon Foucault in 1851, when he first demonstrated the Earth's rotation using a pendulum that now bears his name. This day serves to educate people about the Earth's rotation and its effects on daily life, such as the creation of day and night, time zones, and tidal movements. Foucault's initial experiment took place in his home cellar, followed by a public demonstration at the Paris Observatory and a notable demonstration in the Panthéon, where he used a heavy pendulum to illustrate the shift in its oscillation plane due to the Earth's rotation. The original Foucault pendulum from the Panthéon is now housed at the Musée des Arts et Métiers in Paris, while replicas can be found in museums around the world. The celebration encourages a deeper understanding of how Earth's rotation influences various natural phenomena.