It is not safe to look at the sun, so a simple device that used a shadow was developed to safely observe the movement of the sun. The first sun dial was probably just a stick that was put into the ground. At sunrise the shadow of the stick was long and pointed toward the west. During the morning the shadow would get shorter and by noon it would be at its smallest length, perhaps pointing slightly to the north in the Northern Hemisphere. After noon the shadow would grow toward the east and as sunset approached it would grow long once again.
Sundials are the oldest known instrument for telling time.
They were probably invented in Egypt where the day was divided into twelve equal hours as early as 6000 years ago. The horizontal dial plane is marked off into hours and quarter hours. The vertical gnomon, which casts a shadow onto the dial plane, is usually triangular. The angle of the gnomon is equal to the latitude of its location. In the Northern Hemisphere the gnomon points to the north, and in the Southern Hemisphere it points to the south.