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About The Foucault’s Pendulum


Suspended from the ceiling of the Central Foyer of India’s new Parliament building is a Foucault pendulum that all but 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”.


GS III: Science and Technology

Dimensions of the Article:

  1. About Foucault’s Pendulum
  2. Pendulum Motion at Different Latitudes
  3. Educational Significance

About Foucault’s Pendulum

  • Foucault’s pendulum is an experiment created by Leon Foucault in 1851.
  • It provides direct visual evidence of the Earth’s rotation on its axis.
The Largest Foucault’s Pendulum in India:
  • Created by the National Council of Science Museum (NCSM) in Kolkata.
  • Stands 22 meters tall and weighs 36 kg.
  • Installed at the new parliament building, it is the largest pendulum of its kind in India.
  • A prototype was developed and tested at Science City, Kolkata, to ensure safety and functionality.
Experimental Setup:
  • A heavy object is suspended from a height with a string, allowing it to swing freely.
  • The pendulum’s initial motion can be in any direction, such as north-south.
  • Over time, the pendulum changes its orientation gradually, e.g., shifting to east-west.

Ground Rotation, Not Pendulum:

  • The apparent change in the pendulum’s motion is due to the rotation of the ground beneath it.
  • Observers on the ground, rotating with the Earth, can observe the pendulum’s change in orientation.

Pendulum Motion at Different Latitudes:

At the north and south poles:

  • When aligned with the Earth’s axis of rotation, the pendulum’s back-and-forth motion returns to its original plane in precisely 24 hours.
  • It gradually shifts from north-south to northeast-southwest and east-west before returning to its original orientation.

At other latitudes:

  • The pendulum takes longer to return to its original orientation.
  • The pendulum is not aligned with the Earth’s axis, causing deviations in its swing.

At the equator:

  • The pendulum remains perpendicular to the axis of rotation.
  • It does not change its orientation, showing no deviation from its original course.

Educational Significance:

  • Foucault’s pendulum is a common feature in science museums worldwide, designed to educate children about the Earth’s rotation.
  • It helps people understand concepts such as the Earth’s spherical shape and its rotation on the axis.
  • Experiments like Foucault’s pendulum embody the spirit of scientific inquiry and promote scientific temper.

-Source: Indian Express

February 2024