I’ve been interested in sundials for ages. Tracking the sun’s path by observing the shadow of a stick is an ancient form of astronomy, and a gateway into geometry (literally “land measurement”).

A sundial often marks the solstices and equinoxes, and enables measurement of the cardinal directions of north, south, east, and west: at the peak of its daily journey through the sky, the sun throws a north-south shadow; on the equinoxes, the shadow of the sun draws an east-west line. Ancient sundials acted as calendars, showing precisely when the sun returned to a given spot in its annual journey from south to north and back again.