How does a sundial tell time?


Long before we had clocks and watches, people used sundial to tell time.  A sundial is really a shadow clock – it tells the time by the sun’s shadow.

A sundial consists of the dial face and the gnomon (pointer), which is set in the center of the dial.  The dial is divided into hours.

Many sundial have dials numbered in Roman numerals from 5 to 8.  When the sun strikes the gnomon, it casts a shadow that points toward the numbers on the dial.  As the sun moves across the sky during the day,  the time is told by the shadow of the gnomon falling on the different numbers.

A sundial cannot tell the time at night when the sun is not shining, nor can it tell the time when the sun is hidden by the clouds.  And it cannot rely time by minutes and seconds.  It is no, wonder that people worked out other ways of telling time.

Today, sundials are often built in gardens for their looks rather than for their usefulness.

1 Comment

  1. I am doing a project on ancient egypt sundials. Would you have any access to a picture or information??

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