A clock is an instrument for measuring time. True clocks have an announcing or striking mechanism that sounds after each set interval of time, usually by ringing a bell. A silent clock without a striking mechanism is traditionally known as a timepiece.The clock is one of the oldest human inventions.As the seasons and the phases of the moon can be used to measure the passage of longer periods of change, shorter processes of measurement were desired, hence the invention of the terms, “hours” and “minutes”. The sundial which measures the time of the day by the direction of shadows cast by the sun, was widely used in ancient times. A well-designed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era. However, its practical limitations – it requires the sun to shine and doesn’t work at all during the night – encouraged the use of other techniques for measuring time.Candles and sticks of incense that burn down at, approximately, predictable speeds have also been used to estimate the passing of time. In an hour glass, fine sand pours through a tiny hole at a constant rate and indicates a predetermined passage of an arbitrary period of time.Water clocks, along with the sundials, are possibly the oldest time-measuring instruments.In 797 (or possibly 801), the caliph of Baghdad, Harun al-Rashid, presented Charlemagne with an Asian elephant named Abul-Abbas together with a mechanical clock, out of which came a mechanical bird to announce the hours. This indicates that the early mechanical clock probably was made in Eastern Asia.
None of the first clocks survive from 13th century Europe, but various mentions in church records reveal some of the early history of the clock. Medieval religious institutions required clocks to measure and indicate the passing of time because, for many centuries, daily prayer and work schedules had to be strictly regulated. In modern times clockmaker’s developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock’s accuracy, so many different mechanisms were tried.
The History of the Clock