Foucault pendulum 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. An exact copy of the original pendulum has been operating under the dome of the Panthéon, Paris since 1995. At either the North Pole or South Pole, the plane of oscillation of a pendulum remains fixed relative to the distant masses of the universe while Earth rotates underneath it, taking one sidereal day to complete a rotation. So, relative to Earth, the plane of oscillation of a pendulum at the North Pole
Glan–Foucault prism Glan–Foucault prism A Glan–Foucault prism (also called a Glan–air prism) is a type of prism which is used as a polarizer. It is similar in construction to a Glan–Thompson prism, except that two right-angled calcite prisms are spaced with an air gap instead of being cemented together. Total internal reflection of "p"-polarized light at the air gap means that only "s"-polarized light is transmitted straight through the prism. Compared to the Glan–Thompson prism, the Glan–Foucault has a narrower acceptance angle over which it works, but because it uses an air gap rather than cement, much higher irradiances can be used