Editing Foucault pendulum (section)

== History ==
[[File:Foucault Pendulum.jpg|thumb|left|upright|A print of the Foucault Pendulum, 1895]]
[[File:Foucault pendulum 1.webm|thumb|upright=1.2|Foucault Pendulum at [[COSI Columbus]] knocking over a ball]]

Foucault was inspired by observing a thin flexible rod on the axis of a [[lathe]], which vibrated in the same plane despite the rotation of the supporting frame of the lathe.<ref name=":0">{{Cite journal |last=Sommeria |first=Joël |date=2017-11-01 |title=Foucault and the rotation of the Earth |journal=Comptes Rendus Physique |series=Science in the making: The Comptes rendus de l’Académie des sciences throughout history |language=en |volume=18 |issue=9 |pages=520–525 |doi=10.1016/j.crhy.2017.11.003 |bibcode=2017CRPhy..18..520S |issn=1631-0705|doi-access=free }}</ref> 

The first public exhibition of a Foucault pendulum took place in February 1851 in the [[Paris meridian|Meridian]] of the [[Paris Observatory]]. A few weeks later, Foucault made his most famous pendulum when he suspended a {{convert|28|kg|lb|adj=on}} brass-coated lead [[bob (physics)|bob]] with a {{convert|67|m|ft|adj=mid|long}} wire from the dome of the [[Panthéon, Paris]]. 

Because the latitude of its location was <math>\phi = \mathrm{48^\circ 52' N}</math>, the plane of the pendulum's swing made a full circle in approximately <math display="inline">\frac{\mathrm{23h56'}}{\sin \phi} \approx \mathrm{31.8\,h} \;(\mathrm{31\,h\,50\,min})</math>, rotating clockwise approximately 11.3° per hour. The proper period of the pendulum was approximately <math display="inline">2\pi\sqrt{l/g}\approx 16.5 \,\mathrm{s}</math>, so with each oscillation, the pendulum rotates by about <math>9.05 \times 10^{-4} \mathrm{rad}</math>. Foucault reported observing 2.3 mm of deflection on the edge of a pendulum every oscillation, which is achieved if the pendulum swing angle is 2.1°.<ref name=":0" />

Foucault explained his results in an 1851 paper entitled ''Physical demonstration of the Earth's rotational movement by means of the pendulum'', published in the ''[[Comptes rendus de l'Académie des Sciences]]''. He wrote that, at the North Pole:<ref>{{Cite wikisource |wslanguage=fr |title=Démonstration physique du mouvement de rotation de la Terre au moyen du pendule |last=Foucault |first=Léon |year=1851}}</ref>
<blockquote>...an oscillatory movement of the pendulum mass follows an arc of a circle whose plane is well known, and to which the [[inertia]] of matter ensures an unchanging position in space. If these oscillations continue for a certain time, the movement of the earth, which continues to rotate from west to east, will become sensitive in contrast to the immobility of the oscillation plane whose trace on the ground will seem animated by a movement consistent with the apparent movement of the celestial sphere; and if the oscillations could be perpetuated for twenty-four hours, the trace of their plane would then execute an entire revolution around the vertical projection of the point of suspension.</blockquote>

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.<ref>{{cite web |url=http://www.parisenimages.fr/fr/galerie-collections/9232-13-pendule-foucault-du-pantheon-ceremonie-dinauguration-m-chaumie-ministre-linstruction-publique-brulant-fil-retenue-mettre-marche-pendule-1902 |title=The Pendulum of Foucault of the Panthéon. Ceremony of inauguration by M. Chaumié, minister of the state education, burnt the wire of balancing, to start the pendulum. 1902 |publisher=Paris en images |url-status=dead |archive-url=https://web.archive.org/web/20140821171755/http://www.parisenimages.fr/fr/galerie-collections/9232-13-pendule-foucault-du-pantheon-ceremonie-dinauguration-m-chaumie-ministre-linstruction-publique-brulant-fil-retenue-mettre-marche-pendule-1902 |archive-date=2014-08-21 }}</ref>

During museum reconstruction in the 1990s, the original pendulum was temporarily displayed at the Panthéon (1995), but was later returned to the [[Musée des Arts et Métiers]] before it reopened in 2000.<ref>{{cite web|last=Kissell|first=Joe|title=Foucault's Pendulum: Low-tech proof of Earth's rotation|url=http://itotd.com/articles/362/foucaults-pendulum/|publisher=Interesting thing of the day|access-date=March 21, 2012|date=November 8, 2004|url-status=live|archive-url=https://web.archive.org/web/20120312175754/http://itotd.com/articles/362/foucaults-pendulum/|archive-date=March 12, 2012}}</ref> On April 6, 2010, the cable suspending the bob in the Musée des Arts et Métiers snapped, causing irreparable damage to the pendulum bob and to the marble flooring of the museum.<ref>{{cite magazine |url=http://www.lexpress.fr/actualite/sciences/le-pendule-de-foucault-perd-la-boule_888228.html |title=Le pendule de Foucault perd la boule |first=Boris |last=Thiolay |magazine=L'Express |date=April 28, 2010 |language=fr |url-status=live |archive-url=https://web.archive.org/web/20100710123539/http://www.lexpress.fr/actualite/sciences/le-pendule-de-foucault-perd-la-boule_888228.html |archive-date=July 10, 2010 }}</ref><ref>{{cite news |last=Caulcutt |first=Clea |title=Foucault's pendulum is sent crashing to Earth |url=https://www.timeshighereducation.com/news/foucaults-pendulum-is-sent-crashing-to-earth/411529.article |access-date=August 10, 2024 |newspaper=[[Times Higher Education]] |date=13 May 2010 |url-access=limited |url-status=live |archive-url=https://web.archive.org/web/20240302021907/https://www.timeshighereducation.com/news/foucaults-pendulum-is-sent-crashing-to-earth/411529.article |archive-date=March 2, 2024}}</ref> The original, now damaged pendulum bob is displayed in a separate case adjacent to the current pendulum display.

An exact copy of the original pendulum has been operating under the dome of the Panthéon, Paris since 1995.<ref>{{cite magazine|title=Foucault's Pendulum and the Paris Pantheon|url=https://www.atlasobscura.com/places/pantheon-paris|access-date=January 12, 2018|magazine=Atlas Obscura|url-status=live|archive-url=https://web.archive.org/web/20180112160124/https://www.atlasobscura.com/places/pantheon-paris|archive-date=January 12, 2018}}</ref>