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Updated: September 30, 2013 13:48 IST

Circle of discovery

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A copy: At the Regional Science Centre in Coimbatore. Photo: K. Ananthan
A copy: At the Regional Science Centre in Coimbatore. Photo: K. Ananthan

Léon Foucault was born on September 18, 1819. His 194th birth anniversary is a good time to take a look at his discovery, the Foucault pendulum used to determine Earth’s rotation.

The early months of 1851 were indeed important as everyone living on Earth got to know the science behind Earth’s rotation. French physicist Jean Bernard Léon Foucault created an uproar with his creation of the Foucault pendulum — first exhibited in the Meridian of the Paris Observatory.

The study of medicine was his first choice. But, he soon gave it up as he suffered from Hemophobia (fear of blood). Soon after, he started assisting other famous physicists.

New finds

His claim to fame came with his discovery that light travelled slower through water than through air. Popular as the Foucault–Fizeau experiment, this served as a launch pad when he demonstrated Earth’s rotation. A “pendulum mania” swept across Europe and the U.S.

The original pendulum consisted of a 28kg brass-coated lead bob that was suspended from the dome of the Pantheon with a 67-metre long wire.

This pendulum completed a full circle once every 32.7 hours, swinging clockwise at 11° per hour.

In 1852, he went a step further by demonstrating the earth’s rotation using a gyroscope.

Foucault earned the Copley Medal of the Royal Society for his efforts in proving Earth's diurnal rotation in the year 1855.

There were many more experiments done by him but his health took a toll on him and the world lost a mastermind on February 11, 1868.

Know more: Wikipedia

- The original bob used in 1851 at the Panthéon was moved in 1855 to the Conservatoire des Arts et Métiers in Paris.

- A second temporary installation was made for the 50th anniversary in 1902.

- During museum reconstruction in the 1990s the original pendulum was temporarily displayed at the Panthéon (1995), but was later sent to the Musée des Arts et Métiers before it reopened in 2000.

- On April 6, 2010 the cable suspending the bob in the Musée des Arts et Métiers snapped, causing irreparable damage to the pendulum and to the marble flooring of the museum.

- A replica of the original pendulum has been swinging permanently since 1995 under the dome of the Panthéon, Paris.

- If you visit the Eiffel Tower look for his name. it features on the wall of fame with 72 French scientists, engineers, and mathematicians.

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