The history of the sundial is rooted deep in antiquity. It is not known who made the first sundial. But long before recorded history, man has noticed the passage of the sun through the sky. There are many ancient structures that support this conclusion. One such structure is Stonehenge. Stonehenge is a monument constructed on Salisbury Plain some four thousand years ago [2]. The stones of Stonehenge are oriented to mark off certain dates of the year. The construction merely proves that ancient man knew of the motion of the sun through the sky.

The earliest known sundials come to us from the Egyptians. About 1500 B.C. the Egyptians started constructing sundials [3]. These sundials were known as step sundials. A vertical wall cast a shadow upon a set of steps where upon the ``time'' was read [4]. As time progressed, they got better at their sundials. Around 330-30 B.C. (Hellenistic Period), the Egyptians realized that the length of the day was not constant through the year, and constructed sundials which accounted for this variable [3].

There are many examples found in various works of literature indicating the use of sundials. In the Bible there is reference to the Dial of Ahaz in the verses of Kings 20:9-11

And Isiah the prophet cried unto the Lord; and he brought the shadow ten degrees backward, by which it had gone down in the dial of Ahaz.

Behold, I will bring again the shadow of the degrees, which is gone down in the sundial of Ahaz, ten degrees backward. So the sun returned ten degrees, by which it had gone down.

The Babylonians also used a gnomon. By measuring the length of the gnomon, the Babylonians divided the day up into twelve equal parts. Six parts in the morning, and six parts for the evening [5].

From the Babylonians, the greeks acquired the knowledge of the gnomon along with the twelve equal parts of the day [5]. Anaximander of Miletus constructed a sundial around 560 B.C. [3]. This sundial consisted of a vertical gnomon that was probably construced in a town square to indicate the time of day. Later the greeks made smaller hand-help versions called heliotropes. These consisted of a block of stone or wood out of which a bowl was cut, and placed a small gnomon. On the inside of the bowl was cast the shadow of the gnomon. Lines were present on the interior of the bowl to indicate the time.

Starting around 290 B.C., the Romans extensively used the sundial to tell time [1]. There are numerous examples of Roman artifacts which are clearly bowl shaped sundials [1]. Sundials were known to be sold in markets to the public. As a consequence, sundials were very popular amongst the Romans [5].

Before the modern clock, people often carved sundials into buildings. In many historic farmhouses, one can often find a line carved into something like the window sill, a wall, or a floor. This mark was called the noon mark, and was used to indicate the time of local noon [5]. When the window's shadow was cast upon the line, the time was noon. This gave an indication when the farmers should be called in for their evening meal.

In modern times, the need for sundials has diminished. Thanks to accurate digital watches, there is no need to carry around a pocket-sized sundial. Nevertheless, sundials should not be forgotten. They are still one of the most reliable forms of timepieces available, for the sun will always rise in the morning and set in the evening. The length of the winter days will always be shorter than the length of summer days. If we get nothing more than pleasure out of their use, we at least gain a clear understanding of sun and its motion through the sky.