What is a Foucault’s Pendulum, hanging in the new Parliament building

(Important for Prelims)

Article 51A of the Constitution enshrines every citizen “to develop the scientific temper, humanism, and the spirit of inquiry and reform”. In keeping with that, there was a decision by those handling the project to have a piece reflecting this.

·        It signifies the “integration of the idea of India with the idea of the cosmos”.

·    At the latitude of the Parliament, it takes 49 hours, 59 minutes, and 18 seconds for the pendulum to complete one rotation, as per the details displayed at the installation.

Background of Foucault’s pendulum

·  The original Foucault’s pendulum, named after 19th century French scientist Leon Foucault, is a simple experiment to demonstrate the earth’s rotation. When Foucault carried out this experiment for the public in 1851, it was the first direct visual evidence of the fact that the earth rotates on its axis.

Science behind Foucault’s pendulum

·    The experimental set-up involves a heavy object hung from a height with a string, free to swing in any direction. Once set in to-and-fro motion, the pendulum is seen to change its orientation slowly over time. For example, if the initial motion imparted to it was in the north-south direction, after a few hours it could be seen moving in the east-west direction.

·    Actually, it is not the pendulum that changes its plane of motion, but the ground beneath it. Observers standing on the ground do not notice the earth’s rotation, because they too are rotating with the earth, but can notice the change in orientation of the pendulum.

·   At the north and south poles, when the pendulum is aligned with the axis of rotation of the earth, the pendulum’s back-and-forth motion comes back to its original plane in exactly 24 hours. That is, if it starts swinging in the north-south direction, it then slowly turns in the northeast-southwest direction, then in the east-west direction. It keeps on changing its orientation, till it is back in its original orientation after 24 hours.