Sun, sand and water

We are not talking about the beach: sun, sand and water were the first means used to measure and calculate time. In antiquity, as people perceived that the sunlight casts larger or smaller shadows from a certain object throughout the day, they started do fix a stick on the floor. When the shadow disappeared, it was noon; as the size of the shadow increased, the day ended. The idea evolved into the sun watch, called gnomon.

Another invention of the ancient world was the water clock, called clepsidra. It worked similarly to the hourglass, an instrument with two containers and an orifice, through which an amount of sand passes. The time needed for the sand to pass from one container to the other is the same - so that it was possible, for example, to calculate the guard time of Roman troops, the working day of ancient times.