Creating accurate time pieces has been a long-standing goal. Some of the earliest devices, such as the sun dial, suffered from the fact that they depended on the presence of sunlight. Water clocks, that measured the level of water in a container as it flowed out through a hole at the bottom, solved that problem but suffered from others, such as that the rate of flow depended upon the height of water in the container and was thus irregular and that the water had to be manually replenished. Another thing that had to be taken into account was that in those days, an ‘hour’ was not a fixed time interval as it is now. Instead, an ‘hour’ was defined by dividing the total amount of daylight in a day by twelve, and thus the length of an ‘hour’ varied with the seasons and this was hard to take into account.
But way back in the in the 3rd century BCE, a Greek inventor in Alexandria named Ctesibius devised an ingenious water clock that solved all these problems and which remained the standard for about 1800 years until the invention of the pendulum clock in 1656.
This video explains how he did it.
Cool
The question arises: if Ctesibius’s clock was so accurate, why did Europeans start using mechanical clocks -- around 1300- which (until the 17th century invention of pendulum clocks) were less accurate? The answer in a word: winter. A water clock is not much use when the water freezes! Europeans also used sand clocks for short durations. The adoption of the mechanical clock may in turn have been responsible for the switch to equal hours: making one which could manage different hours for day and night, winter and summer, was probably beyond the clockmakers’ abilities.