Answer: January 8
Notes: Earth’s Rotation Day is observed every year on 8 January to highlight Earth’s continuous rotation on its axis. It commemorates the 1851 Foucault Pendulum experiment conducted by French physicist Léon Foucault. The experiment gave the first clear experimental proof that Earth rotates on its axis. Earth’s rotation causes the day–night cycle and influences climate and wind patterns. The day promotes awareness of basic Earth science and astronomy.
