Demonstration of Foucault�s pendulum at the Pantheon, Paris, France, 1880.

FRANCE - MAY 14: This print shows the display of a Foucault's pendulum, a striking demonstration to illustrate the rotation of the Earth. Devised by the French physicist Leon Foucault (1819-1868), this engraving shows the site of its first demonstration inside the Parisian Patheon in 1851. This illustration was reproduced in 'Astronomie Populaire' by Camille Flammarion published in 1880. The pendulum shows evidence of the earth's rotation by changing its plane of oscillation as it swing back and forward over the course of an hour or so. To make this movement apparent an angular scale marked in degrees is usual placed below the Foucault pendulum. (Photo by SSPL/Getty Images)