Sundials are the oldest known devices used to measure time. It is believed that sundials were first used by the Babylonians as early as 2000 B.C. The Egyptian and Chinese cultures were also believed to have used sundials to measure time. However, the Chaldeans probably had the earliest and most accurate sundials of the ancient world. They divided the day and night into twelve-hour periods each.
Later on, the Greeks and Romans developed more accurate forms of keeping time. They made smaller sundials so that the wealthy could carry them. Sundials were put on south-facing walls so that the public could read time as well. During the Renaissance time period, zodiac symbols began to appear on sundials in order to tell the date and season as well as the hours and minutes; intricately covered sundials were part of the artistic style ofthe era. Some sundials during this time even showed the periods of high and low tides.
Sundials tell time using the sun, which creates different angles of shadows throughout the day. These shadows are longer in the early morning and late afternoon. Since the sun rises in the east and sets in the west, the sundial shadow points west in the morning while the shadow points to the east in the evening. Sundial shadows are also affected by season; the sun is lower in the sky during the winter, thus there are longer shadows. In summer, there are shorter shadows because the sun is higher in the sky. Per hour, the sun “moves” approximately fifteen degrees.
Sundials come in a variety of styles. From a simple stick in the ground, to an elaborately-made 3D model, sundials have the same common purpose of telling time. Some sundials come in the form of different shapes; the obelisk, used by the ancient Egyptians, creates a shadow from which to accurately tell time. Most sundials however, lie flat on the ground with a pointer sticking up from the center.
The pointer of a sundial is called the gnomon. Another part of the sundial is the plane, also known as the dial face. A standard sundial is divided by hours; more rarely, they are divided into increments of fifteen and thirty minute time periods.
In modern times, sundials have been frequently used in gardens as decoration. They are also used in front of professional businesses as a form of art. Although not as accurate as current time-keeping methods such as clocks and watches, the sundial can still be found in different parts of the present society.