Google Doodle celebrates French physicist Léon Foucault’s 194th birthday with pendulum tribute

Foucault pendulum is a simple device introduced in 1851 to confirm that the earth rotated

John Hall@johnmatthewhall
Monday 08 September 2014 15:38

The interactive doodle is based on the Foucault pendulum - a radical device he created to demonstrate the effect of the earth’s rotation - and allows users to manipulate the swinging bob according to where on earth they happen to be.

The Foucault pendulum is a simple device introduced in 1851 to confirm, in as basic a way as possible, the long-assumed theory that the earth rotated.

Foucault’s original pendulum was first exhibited in the Meridian of the Paris Observatory, and consisted of a 28kg brass-coated lead bob with a 67-metre long wire from the dome of the Pantheon. The pendulum made a full circle once every 32.7 hours, swinging clockwise at 11 degrees per hour.

Foucault was born the son of a publisher in Paris on September 18, 1819 and originally studied medicine, but was forced to give it up after developing a fear of blood.

His career as a physicist began shortly after, assisting and collaborating with Alfred Donne and Hippolyte Fizeau.

In 1850 he conducted a ground-breaking experiment that was viewed as “driving the last nail in the coffin” of Newton’s corpuscle theory of light when it proved light travels more slowly through water than through air.

In 1851 Foucault caused a sensation with his famous pendulum experiment, and the following year he used and named (but did not invent) the gyroscope – a device for measuring and maintaining orientation.

In 1855 Foucault discovered that the force required for the rotation of a copper disc becomes greater when it is made to rotate with its rim between the poles of a magnet, the disc at the same time becoming heated by the eddy current or “Foucault currents” induced in the metal.

Two years later he invented the Foucault polarizer, and in 1858 devised a method of testing the mirror reflecting telescope to determine its shape – the so-called Foucault knife-edge test which is still used in amateur telescopes.

Foucault died of multiple sclerosis on February 11, 1868 at the age of 48 after being made a member of many of the top scientific societies in Europe.

He was buried in the Cimetière de Montmartre, with his name among those of seventy-two French scientists, engineers, and mathematicians engraved on the Eiffel Tower. The asteroid 5668 Foucault is also named after him.

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