<P> A sundial is a device that tells the time of day when there is sunlight by the apparent position of the Sun in the sky . In the narrowest sense of the word, it consists of a flat plate (the dial) and a gnomon, which casts a shadow onto the dial . As the Sun appears to move across the sky, the shadow aligns with different hour - lines, which are marked on the dial to indicate the time of day . The style is the time - telling edge of the gnomon, though a single point or nodus may be used . The gnomon casts a broad shadow; the shadow of the style shows the time . The gnomon may be a rod, wire, or elaborately decorated metal casting . The style must be parallel to the axis of the Earth's rotation for the sundial to be accurate throughout the year . The style's angle from horizontal is equal to the sundial's geographical latitude . </P> <P> In a broader sense, a sundial is any device that uses the Sun's altitude or azimuth (or both) to show the time . In addition to their time - telling function, sundials are valued as decorative objects, literary metaphors, and objects of mathematical study . </P>

What is a sundial and how does it work
find me the text answering this question