Jan 8th - Earth's Rotation Day

 

Almost everyone knows that the Earth rotates on an almost vertical axis every 24 hours, which gives us one Earth day but not many of us remember when it was universally recognized and acknowledged. Earth’s Rotation Day marks the calendar as on this day in 1851, the French physicist Leon Foucault proved that the Earth rotates on its axis by demonstrating axis rotation supported by his pendulum experiments.

Foucault’s Experiment

Foucault built the Foucault Pendulum to prove his theory. This simple and brilliant device shows the rotation of the Earth over a day by hanging a lead ball. The physicist hung pendulum from the top of the Pantheon at world fair held in Paris in a lead-filled brass sphere. As the pendulum swings, pins arranged in a circle are knocked down one by one by the pendulum, completing a full rotation. Thus, with the help of the pendulum, Foucault demonstrated that the plane of the swing of the pendulum rotates in relation to the Earth's rotation. 

 

Why this day is named after Foucault while many Muslim and Greek scientists have found it earlier?

Before Foucault’s demonstration, many scientists in the early centuries observed this phenomenon. Muslim scientists like Abu Rayḥan Al-Biruni and ancient Greek scientists such as Aristarchus of Samos have found that earth’s rotate on its axis in 24 hours but none of them have reported their findings in world records which is why they left unknown for their contribution. On the other hand, Foucault was the first scientist to report his finding in the world record which helped him carve his name in the history as the discoverer of earth’s rotation with his world famous “Pendulum Experiment”.