History

Posted: Sun Jul 05, 2009 3:40 pm     Post subject: History

History
Replica of an ancient Chinese incense clock

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. Such measurements require devices. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.

Sundials and other devices
The sundial, which measures the time of 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 does not work at all during the night - encouraged the use of other techniques for measuring time. In India, the King of Jaipur the Pink City, Jai Singh II constructed many instruments and sundials in the observatories in cities Jaipur, Varanasi, Ujjain, Mathura between 1724-1730 A.D. He had a good interest in astronomy and town planning.