Equatorial sundial

Sundials were among the first devices created to tell the time. The variation of the shadow cast by a pin or blade (the gnomon or style) on a graduated surface charts the Earth’s rotation on its axis, and therefore solar time. The dial indicates solar noon, the moment when the sun is highest in the sky. To determine the actual time, correction tables need to be consulted, which vary with the seasons and location. Of the many types of sundials, of special note is the one designed by Jean Desclincourt, the interior of whose spherical bowl, engraved with the zodiac, parallels and meridians, enables the hour and date to be read.