How did the ancient Egyptians measure time?
Remarkably, the ancient Egyptians divided the year in twelve months and each day into 24 hours: 12 hours for day and 12 hours for night, regardless of the seasons. This, of course, led to a certain approximation also because there is no evidence that the hour was later divided into smaller measurements. We know Egyptians use the word "at", with the meaning of "moment", but that does not indicate a precise duration.
Time, on the other hand, was called "unut", and linked to this word is another word, "unuyt" which defined the necessary, constant presence of at least one priest in the temples to ensure the continuity of the worship of the God to whom the temple was dedicated.
During the day the measurement of the time was performed with gnomons, even portable ones, with which the length of the shadow was observed on a graduated scale or its projection on a plane divided into sectors.
Let's not forget that Eratosthenes of Cyrene, in Ptolemaic times was able to determine the circumference of the globe with incredible precision by comparing the length of the shadows at the zenith of two obelisks, one in Alexandria and one in Thebes, and measuring the distance between the two! These gnomons often bore the image of a baboon, as a representation of the God of all measurements, Thoth.
During the night, however, to determine the time ancient Egyptians relies on the passage of certain stars from the zenith. The movement of the stars was observed through a slit cut in a tablet that was oriented with plumb lines.
It was only during the New Kingdom, under Amenophis I, that an engineer called Amenemhet invented the hourglass. It consisted of a conical vessel graduated on the inside with 12 notches and in which a carefully calibrated hole was drilled in the bottom. It was not filled with sand, however, but with water, to the brim, at sunrise and sunset.
Depending on the level of the water, one could thus know the time. Water, by the way, allowed a more precise and constant measurement than that with sand, as it was not affected by atmospheric humidity!
The measurement of time was for the Egyptians and the state administration very important. This is confirmed by administrative papyri in which Pharaoh's officials kept track of the hours of work that were actually performed.
