First timekeeping device

First used in Mesopotamia in c. 3500 BC, the time stick – a primitive form of sundial – was the first “clock” ever developed by Man. Consisting simply of a long stick planted in the earth, it told the time by casting a shadow on the ground that changed length and position as the Sun “moved” overhead. Later, more sophisticated versions were created with multiple sides, with each one featuring a timescale for a different month or season. Around 2500–2000 BC, the Egyptians replaced these sticks with the obelisk, a large stone spire hewn from a single piece of rock that worked in a similar way to the time stick but on a grander scale. More conventional sundials were first developed in c.300 BC. A vertical pointer – called a gnomon (Greek for “one who knows”) – cast a shadow on to a dial marked with the hours of the day. Special devices called “merkhets” could be placed over the sundial at night to measure the time by the stars.