The Foucault’s Pendulum

The Foucault’s Pendulum

Subject : Science and technology

Section: Msc

Concept :

• The Foucault’s Pendulum has been installed hanging from a skylight at the top of the Constitution Hall in the newly inaugurated Parliament.
• Suspended from the ceiling of the Central Foyer of India’s new Parliament building, inaugurated is a Foucault pendulum.

Foucault’s Pendulum

• The Foucault’s Pendulum was named after French physicist Léon Foucault who invented it in the mid-19th Century.
• Foucault in 1851 built the first-of-its-kind pendulum comprising a 28-kilo iron ball and a 67-metre steel wire.
• Foucault hung the pendulum inside France’s Panthéon and then pushed it to one side and released it – after which it began swinging back and forth.
• Though the pendulum swings back and forth the Earth rotates beneath it. This means relative motion is at play.
• At the North Pole, latitude 90° N, the relative motion as viewed from above in the plane of the pendulum’s suspension is a counterclockwise rotation of the Earth once approximately every 24 hours (more precisely, once every 23 hours 56 minutes 4 seconds, the length of a sidereal day). Correspondingly, the plane of the pendulum as viewed from above appears to rotate in a clockwise direction once a day.
• A Foucault pendulum always rotates clockwise in the Northern Hemisphere with a rate that becomes slower as the pendulum’s location approaches the Equator.
• Foucault’s original pendulums at Paris rotated clockwise at a rate of more than 11° per hour, or with a period of about 32 hours per complete rotation.
• The rate of rotation depends on the latitude.
• At the Equator, 0° latitude, a Foucault pendulum does not rotate.
• In the Southern Hemisphere, rotation is counter-clockwise.
• In short, as the Earth rotates on its axis the pendulum changes the direction it swings in.

The pendulum inside the new Parliament

• Created by the National Council of Science Museum (NCSM) in Kolkata, the pendulum is being dubbed as the largest such piece in India, 22 metre in height, and weighing a staggering 36 kg.
• The piece has been crafted with gunmetal and affixed with an electromagnetic coil to ensure hassle-free movement.
• It touches the floor as it rotates on its axis. The pendulum hangs from a skylight at the top of the Constitution Hall, and 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.