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The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today. 
Clock at the Royal Observatory, Greenwich 
Replica of an ancient Chinese incense clock 
A scale model of Su Song’s Astronomical Clock Tower, built in 11th century Kaifeng, China. It was driven by a large waterwheel, chain drive, and escapement mechanism. 
Automatic clock of al-Jazari, 12th century. 
An elephant clock in a manuscript by Al-Jazari (1206 AD) from The Book of Knowledge of Ingenious Mechanical Devices. 
A linear clock at London’s Piccadilly Circus tube station. The 24 hour band moves across the static map, keeping pace with the apparent movement of the sun above ground, and a pointer fixed on London points to the current time 
Digital clock outside Kanazawa Station displaying the time by controlling valves on a fountain
From Wikipedia, the free encyclopedia : Watches and clocks |
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