The Gnomon - Sundial

Early Sundials

In antiquity, day refers primarily to the hours of available sunlight. When we refer to the day in its abstract form, we mean both the daytime and nighttime. But before our modern methods of timekeeping, the overall day was seen as two very different events. The clearest markings for each day hinged on the rising and the setting of the sun.

Naturally, the earliest timepieces relied on the sun as their referent. Or, to be more precise, the earliest timepieces relied on the shadows caused by the sun. At dawn, with the sun rising in the east, long shadows form which fall to the west. As the sun rises to its position overhead at noon, the shadows shorten. With the sun�s descent toward dusk, shadows begin to lengthen again, this time pointing to the east. The movement and length of shadows, as the sun rises and falls, is the basis for many early sundials.

The first sundial was most likely a stick in the ground. If one were to stand facing the stick (with their back to the south), the first, long shadow of day would appear on the ground to the left. While this gnomon (Greek for to know) was good for marking the dawn, noon, and sunset, it did little to "tell time," as we are used to it today. As sundials spread from Egypt to Greece to Rome, additional refinements and markings were added, in the attempt to make a more accurate timepiece.