Editing Gear (section)

==History==

The oldest functioning gears by far are not man made, but are seen in the hind legs of the nymphs of the planthopper insect ''[[Issus coleoptratus]]''.

[[File:Han Iron Gears (9947881746).jpg|thumb|Iron gears, [[Han dynasty]]]]
The earliest man-made gears that have not been lost or destroyed date to 4th century BC [[China]]<ref name="Derek">[[Derek J. de Solla Price]], [http://www.gutenberg.org/files/30001/30001-h/30001-h.htm On the Origin of Clockwork, Perpetual Motion Devices, and the Compass], p.84</ref> (Zhan Guo times – Late East [[Zhou dynasty]]), which have been preserved at the [[Luoyang Museum]] of Henan Province, [[China]].

[[File:Antikythera Fragment A (Front).webp|thumb|The main fragment of the [[Antikythera mechanism]]]]
In Europe, [[Aristotle]] mentions gears around 330&nbsp;BC, as wheel drives in [[windlass|windlasses]]. He observed that the direction of rotation is reversed when one gear wheel drives another gear wheel. [[Philo of Byzantium|Philon of Byzantium]] was one of the first who used gears in water raising devices.<ref>{{Cite web |title=Gears from Archimedes, Heron and Dionysius |url=https://www.hellenicaworld.com/Greece/Technology/en/ArchimedesGears.html |access-date=2023-11-21 |website=www.hellenicaworld.com}}</ref> Gears appear in works connected to [[Hero of Alexandria]], in [[Roman Egypt]] circa AD&nbsp;50,<ref>{{harvnb|Norton|2004|p=462}}</ref> but can be traced back to the mechanics of the [[Library of Alexandria]] in 3rd-century BC [[Ptolemaic Egypt]], and were greatly developed by the Greek [[polymath]] [[Archimedes]] (287–212 BC).<ref>{{cite journal |first=M. J. T. |last=Lewis |title=Gearing in the Ancient World |journal=Endeavour |volume=17 |issue=3 |year=1993 |pages=110–115 |doi=10.1016/0160-9327(93)90099-O }}</ref>  The earliest surviving gears in Europe were found in the [[Antikythera mechanism]] an example of a very early and intricate geared device, designed to calculate [[astronomical]] positions of the sun, moon, and planets, and predict [[eclipse]]s.  Its time of construction is now estimated between 150 and 100&nbsp;BC.<ref>{{cite web |url=http://www.antikythera-mechanism.gr/faq/general-questions/why-is-it-so-important |title=The Antikythera Mechanism Research Project: Why is it so important? |access-date=2011-01-10 |quote=The Mechanism is thought to date from between 150 and 100 BC |archive-url=https://web.archive.org/web/20120504005417/http://www.antikythera-mechanism.gr/faq/general-questions/why-is-it-so-important |archive-date=4 May 2012 |url-status=dead }}</ref><ref>{{Cite web |author1=Owen Jarus |date=2022-04-14 |title=World's first computer, the Antikythera Mechanism, 'started up' in 178 B.C., scientists claim |url=https://www.livescience.com/antikythera-mechanism-start-date-found |access-date=2022-06-05 |website=livescience.com |language=en}}</ref><ref>{{Cite web |last=Freeth |first=Tony |title=An Ancient Greek Astronomical Calculation Machine Reveals New Secrets |url=https://www.scientificamerican.com/article/an-ancient-greek-astronomical-calculation-machine-reveals-new-secrets/ |access-date=2022-06-05 |website=Scientific American |language=en}}</ref>

[[File:South-pointing chariot (Science Museum model).jpg|thumb|right|Modern model of a south-pointing chariot]]
The Chinese engineer [[Ma Jun (mechanical engineer)|Ma Jun]] ({{circa|200}}–265) described a [[south-pointing chariot]].  A set of [[differential (mechanical device)|differential gears]] connected to the wheels and to a pointer on top of the chariot kept the direction of latter  unchanged as the chariot turned.<ref>[[Joseph Needham]] (1986). ''Science and Civilization in China: Volume 4, Part 2'', page 298. Taipei: Caves Books, Ltd.</ref>

Another early surviving example of geared mechanism is a complex calendrical device showing the phase of the Moon, the day of the month and the places of the Sun and the Moon in the Zodiac was invented in the Byzantine empire in the early 6th century.<ref name="vertical dial {{!}} British Museum">{{Cite web |title=vertical dial {{!}} British Museum |url=https://www.britishmuseum.org/collection/object/H_1997-0303-1 |access-date=2022-06-05 |website=The British Museum |language=en}}</ref><ref>{{Cite web |title=The Portable Byzantine Sundial Calendar: The Second Oldest Geared Mechanism in Existence |url=https://www.thearchaeologist.org/blog/the-portable-byzantine-sundial-calendar-the-second-oldest-geared-mechanism-in-existence?format=amp&ved=2ahUKEwif5JvFo5f4AhVIwzgGHR41Co4QtwJ6BAgqEAE&usg=AOvVaw1IoLGjGalchFiBkky90L6x |access-date=2022-06-05 |website=www.thearchaeologist.org}}</ref>

Geared [[mechanical clock|mechanical water clock]]s were built in [[China]] by 725.{{cn|date = July 2024}}

Around 1221, a geared [[astrolabe]] was built in [[Isfahan]]  showing the position of the [[moon]] in the [[zodiac]] and its [[Lunar phase|phase]], and the number of days since new moon.<ref>{{cite web|title=Astrolabe By Muhammad Ibn Abi Bakr Al Isfahani|url=https://www.mhs.ox.ac.uk/astrolabe/catalogue/browseReport/Astrolabe_ID=165.html}}</ref>

The [[worm gear]] was invented in the [[Indian subcontinent]], for use in roller [[cotton gin]]s, some time during the 13th–14th centuries.<ref name="india">[[Irfan Habib]], [https://books.google.com/books?id=K8kO4J3mXUAC&pg=PA53 ''Economic History of Medieval India, 1200-1500'', page 53], [[Pearson Education]]</ref>

A complex astronomical clock, called the [[Astrarium of Giovanni Dondi dell'Orologio|Astrarium]], was built between 1348 and 1364 by [[Giovanni Dondi dell'Orologio]]. It had seven faces and 107 moving parts; it showed the positions of the sun, the moon and the five planets then known, as well as religious feast days.<ref>{{Cite web |title=Giovanni Dondi's Astrarium, 1364 {{!}} cabinet |url=https://www.cabinet.ox.ac.uk/giovanni-dondis-astrarium-1364-0 |access-date=2022-06-05 |website=www.cabinet.ox.ac.uk}}</ref> The [[Salisbury Cathedral clock]], built in 1386, it is the world's oldest still working geared mechanical clock.

[[Differential (mechanical device)|Differential]] gears were used by the British clock maker Joseph Williamson in 1720.{{cn|date = July 2024}}