Foucault's pendulum

The Foucault pendulum (pronounced "foo-KOH", IPA:), or Foucault's pendulum, named after the French physicist Léon Foucault, was conceived as an experiment to demonstrate the rotation of the Earth.
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Foucault's Pendulum (original title: Il pendolo di Foucault) is a novel by Italian novelist and philosopher Umberto Eco. It was first published in 1988; the translation into English by William Weaver appeared a year later. Foucault's Pendulum was re-issued by Harcourt March 2007.Foucault's Pendulum is divided into ten segments represented by the ten Sefiroth. The novel is full of esoteric references to the Kabbalah, alchemy and conspiracy theory, so many that critic and novelist Anthony Burgess has suggested that it needed an index. The title of the book derives from an actual pendulum designed by the French physicist Léon Foucault to demonstrate the rotation of the earth.
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An experiment first performed in 1851 to demonstrate the rotation of the earth without recourse to observing the external universe. Many public science centres have a long simple pendulum set swinging and its plane of oscillation can be observed to apparantly turn slowly; in fact its plane in space is static.