Museo Galileo
Virtual Museum

Rod or style oriented in such a way that its shadow, cast by the Sun's rays, shows the hours on a sundial. It is often positioned to show the time from noon or midday (in Latin: meridies, hence the Italian meridiana, "sundial"). The gnomon function can also be performed by a thread (as in box sundials), or a simple hole in a suitably positioned plate through which the sun's rays fall on an elongated surface marked with the hour lines or signs of the zodiac for tracking the Sun's path during the year.