What is a sundial and how does it work?

The sundial, one of the first instruments used to measure time, works by simulating the movements of the Sun. The Sun shines on a gnomon (pronounced NO-men), a triangle or device set perpendicular to a base plate, and casts its shadow on the appropriate hour line, thus displaying the time of day. The angle on the gnomon has to be parallel to the Earth’s axis and must be equal to your location’s latitude if it is to display accurate clock time.

Sundials tell time by casting a shadow on a base plate marked with the different hours of the day.