History of Timekeeping Devices in Egypt - Sundials and Shadow Clocks

Sundials and Shadow Clocks

Despite Herodotus's attribution of the invention of the sundial to the Babylonians in 430 BC, the earliest known sundials were simple gnomons of Egyptian origin invented around 3500 BC. More complex devices were developed over time, the earliest surviving one a shadow clock made of green schist dating back to approximately 800 BC. Shadow clocks were modified sundials that allowed for greater precision in determining the time of day, and were first used around 1500 BC. Their major innovation was a modified, more precise gnomon that allowed for the division of night time into 50 parts, with an additional two "twilight hours" in the morning and evening. The shadow clock gnomon was made up of a long stem divided into six parts, as well as an elevated crossbar that cast a shadow over the marks. This early clock was positioned eastward in the morning, while at noonit was rotated to face west to measure shadows cast by the setting sun. The concept of measured shadows were adapted into larger, more public designs in the form of obelisks. Markers around the obelisk would indicate units of time, including morning and afternoon as well as the summer and winter solstices for ceremonial purposes.