Context: The new Parliament building’s one of the key features includes a Foucault pendulum suspended from its ‘Constitutional Gallery’ area. It was designed and installed by the National Council of Science Museums (NCSM), Kolkata.

What is a Foucault pendulum?

• It is a deceptively simple device used to illustrate the earth’s rotation.

• Founded by: The Foucault pendulum is named for Léon Foucault (1819-1868), the French physicist who devised the apparatus in the 19th century.

How does the Foucault pendulum function?

• The pendulum consists of a bob suspended at the end of a long, strong wire from a fixed point in the ceiling.

• As the pendulum swings, the imaginary surface across which the wire and the bob swipe is called the plane of the swing.

For instance,

• a) If the pendulum is installed at the North Pole, it will basically be swinging as the earth rotates ‘below’, 

• b) If the pendulum is installed over the equator, the plane won’t appear to shift at all because it will be rotating along with the earth, and 

• c) On any other latitude, the plane will shift through 360 degrees in “one sidereal day divided by the sine of the latitude of its location.

• A Foucault pendulum is not easy to set up. It must be designed, installed, and set swinging in such a way that the bob’s motion is influenced to the extent possible only by gravity.

• Note: In 1991, the then-new Inter-University Centre for Astronomy and Astrophysics, Pune, commissioned the country’s first Foucault pendulum for public display from the NCSM. After several studies and failed tests, the NCSM installed the set-up in 1993.