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al-Jazari's Clocks: Perhaps the Earliest Programmable Analog Computers

1206

In the al-Jāmiʿ bain al-ʿilm wa al-ʿamal al-nāfiʿ fī ṣināʿat al-ḥiyal (The Book of Knowledge of Ingenious Mechanical Devices) written in 1206, the year of his death, Muslim polymath, engineer and inventor Badi'al-Zaman Abū al-'Izz ibn Ismā'īl ibn al-Razāz al-Jazarī (بديع الزمان أَبُو اَلْعِزِ بْنُ إسْماعِيلِ بْنُ الرِّزاز الجزري‎, Turkish: Ebû’l İz İbni İsmail İbni Rezzaz El Cezerî) from Jazirat ibn Umar (current Cizre,Turkey), described 100 mechanical devices, about 80 of which were trick vessels of various kinds, along with instructions on how to construct them. These included his elephant clock, scribe clock, and castle clock. The castle clock, a most sophisticated water-powered astronomical clock, has been called the earliest programmable analog computer. 

"It was a complex device that was about 11 feet high, and had multiple functions alongside timekeeping. It included a display of the zodiac and the solar and lunar orbits, and a pointer in the shape of the crescent moon which travelled across the top of a gateway, moved by a hidden cart and causing automatic doors to open, each revealing a mannequin, every hour. It was possible to re-program the length of day and night everyday in order to account for the changing lengths of day and night throughout the year, and it also featured five robotic musicians who automatically play[ed] music when moved by levers operated by a hidden camshaft attached to a water wheel. Other components of the castle clock included a main reservoir with a float, a float chamber and flow regulator, plate and valve trough, two pulleys, crescent disc displaying the zodiac, and two falcon automata dropping balls into vases" (Wikipedia article on Al-Jazari, accessed 04-02-2009).

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