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Foucault et son pendule

Foucault and his Pendulum


Foucault Pendulum

The Foucault pendulum or Foucault's pendulum, named after the French physicist Léon Foucault, is a simple device conceived as an experiment to demonstrate the rotation of the Earth. While it had long been known that the Earth rotated, the introduction of the Foucault pendulum in 1851 was the first simple proof of the rotation in an easy-to-see experiment. Today, Foucault pendulums are popular displays in science museums and universities.

The first public exhibition of a Foucault pendulum took place in February 1851 in the Meridian of the Paris Observatory. A few weeks later Foucault made his most famous pendulum when he suspended a 28 kg brass-coated lead bob with a 67 meter long wire from the dome of the Panthéon, Paris. The plane of the pendulum's swing rotated clockwise 11° per hour, making a full circle in 32.7 hours

Click here for an explanation (and to calculate how far you are from the North Pole!)

Foucault is also credited with making an early measurement of the speed of light and with the discovery of eddy currents: electric currents induced within conductors by a changing magnetic field in the conductor, which are sometimes called Foucault currents.

The son of a publisher, Foucault was born in Paris in 1819, where he initially studied medicine but soon switched to physics. Initially, the primary focus of his research was into LJM Daguerre's photographic processes, while he was also an assistant to the bacteriologist Alfred Donne in the course of his work on microscopic anatomy.

After collaborating with his fellow physicist Hippolyte Fizeau on a series of investigations into the intensity of the light of the sun, he made his name at the Panthéon in Paris in 1851 with a demonstration that involved suspending a 67-metre, 28kg pendulum suspended from the building's dome.

The plane of its motion, with respect to the earth, rotated slowly clockwise. The experiment sparked a pendulum-mania across Europe and the United States, and crowds were attracted to observe so-called "Foucault pendulums" in major cities on both sides of the Atlantic.

Later achievements included devising a method of testing the mirror of a reflecting telescope to determine its shape, the so-called "Foucault knife-edge test".

By way of recognition for his achievements, Foucault was made a member of the Bureau des Longitudes, of the Royal Society of London and of the Legion d'Honneur.

The physicist, whose name is one of 72 French scientists, engineers, and mathematicians engraved on the Eiffel Tower, died in Paris in 1868.

And the exhibition in Tauranga ???

  • WHENWednesday 23rd October, 10:00am
  • WHERETauranga Art Gallery Atrium
  • TICKETSFREE (donations welcome)

A new work by one of New Zealand's most exciting sculpture artists.

The Atrium of the Tauranga Art Gallery will be home to Foucault’s Pendulum, a new work by Gregor Kregar. This site-specific, suspended installation made from aluminium combined with recycled neon lights is named after the French physicist Léon Foucault who, in 1851, designed an experimental device to demonstrate the rotation of Earth.

Gregor Kregar’s Foucault’s Pendulum opens on 23 October and it not to be missed.

Commissioned by Tauranga Art Galley for Tauranga Arts Festival.

Find out more at