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class="vector-toc-numb">2</span> <span>Regional development</span> </div> </a> <button aria-controls="toc-Regional_development-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Regional development subsection</span> </button> <ul id="toc-Regional_development-sublist" class="vector-toc-list"> <li id="toc-Egypt" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Egypt"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Egypt</span> </div> </a> <ul id="toc-Egypt-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Babylon" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Babylon"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Babylon</span> </div> </a> <ul id="toc-Babylon-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-India" 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class="vector-toc-numb">2.6</span> <span>Greco-Roman world</span> </div> </a> <ul id="toc-Greco-Roman_world-sublist" class="vector-toc-list"> <li id="toc-Clepsydrae_for_keeping_time" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Clepsydrae_for_keeping_time"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.6.1</span> <span>Clepsydrae for keeping time</span> </div> </a> <ul id="toc-Clepsydrae_for_keeping_time-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Medieval_Islamic_world" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Medieval_Islamic_world"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.7</span> <span>Medieval Islamic world</span> </div> </a> <ul id="toc-Medieval_Islamic_world-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Korea" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Korea"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.8</span> <span>Korea</span> </div> </a> <ul id="toc-Korea-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Japan" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Japan"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.9</span> <span>Japan</span> </div> </a> <ul id="toc-Japan-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Temperature,_water_viscosity,_and_clock_accuracy" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Temperature,_water_viscosity,_and_clock_accuracy"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Temperature, water viscosity, and clock accuracy</span> </div> </a> <ul id="toc-Temperature,_water_viscosity,_and_clock_accuracy-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Notes</span> </div> </a> <button aria-controls="toc-Notes-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Notes subsection</span> </button> <ul id="toc-Notes-sublist" class="vector-toc-list"> <li id="toc-Sources_used" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Sources_used"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Sources used</span> </div> </a> <ul id="toc-Sources_used-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Bibliography" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Bibliography"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Bibliography</span> </div> </a> <ul id="toc-Bibliography-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Water clock</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 50 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-50" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">50 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B9%D8%A9_%D9%85%D8%A7%D8%A6%D9%8A%D8%A9" title="ساعة مائية – Arabic" lang="ar" hreflang="ar" data-title="ساعة مائية" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Rel%C3%B3_d%27agua" title="Reló d'agua – Asturian" lang="ast" hreflang="ast" data-title="Reló d'agua" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Su_saat%C4%B1" title="Su saatı – Azerbaijani" lang="az" hreflang="az" data-title="Su saatı" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%9C%E0%A6%B2%E0%A6%98%E0%A6%A1%E0%A6%BC%E0%A6%BF" title="জলঘড়ি – Bangla" lang="bn" hreflang="bn" data-title="জলঘড়ি" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%92%D0%BE%D0%B4%D0%B5%D0%BD_%D1%87%D0%B0%D1%81%D0%BE%D0%B2%D0%BD%D0%B8%D0%BA" title="Воден часовник – Bulgarian" lang="bg" hreflang="bg" data-title="Воден часовник" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Rellotge_d%27aigua" title="Rellotge d'aigua – Catalan" lang="ca" hreflang="ca" data-title="Rellotge d'aigua" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Vodn%C3%AD_hodiny" title="Vodní hodiny – Czech" lang="cs" hreflang="cs" data-title="Vodní hodiny" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Vandur" title="Vandur – Danish" lang="da" hreflang="da" data-title="Vandur" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Wasseruhr" title="Wasseruhr – German" lang="de" hreflang="de" data-title="Wasseruhr" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Reloj_de_agua" title="Reloj de agua – Spanish" lang="es" hreflang="es" data-title="Reloj de agua" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Akvohorlo%C4%9Do" title="Akvohorloĝo – Esperanto" lang="eo" hreflang="eo" data-title="Akvohorloĝo" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Ur_erloju" title="Ur erloju – Basque" lang="eu" hreflang="eu" data-title="Ur erloju" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B9%D8%AA_%D8%A2%D8%A8%DB%8C" title="ساعت آبی – Persian" lang="fa" hreflang="fa" data-title="ساعت آبی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Horloge_hydraulique" title="Horloge hydraulique – French" lang="fr" hreflang="fr" data-title="Horloge hydraulique" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gd mw-list-item"><a href="https://gd.wikipedia.org/wiki/Uaireadair-uisge" title="Uaireadair-uisge – Scottish Gaelic" lang="gd" hreflang="gd" data-title="Uaireadair-uisge" data-language-autonym="Gàidhlig" data-language-local-name="Scottish Gaelic" class="interlanguage-link-target"><span>Gàidhlig</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Reloxo_de_auga" title="Reloxo de auga – Galician" lang="gl" hreflang="gl" data-title="Reloxo de auga" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%AC%BC%EC%8B%9C%EA%B3%84" title="물시계 – Korean" lang="ko" hreflang="ko" data-title="물시계" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%8B%D6%80%D5%AB_%D5%AA%D5%A1%D5%B4%D5%A1%D6%81%D5%B8%D6%82%D5%B5%D6%81" title="Ջրի ժամացույց – Armenian" lang="hy" hreflang="hy" data-title="Ջրի ժամացույց" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%9C%E0%A4%B2_%E0%A4%98%E0%A4%A1%E0%A4%BC%E0%A5%80" title="जल घड़ी – Hindi" lang="hi" hreflang="hi" data-title="जल घड़ी" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Vodeni_sat" title="Vodeni sat – Croatian" lang="hr" hreflang="hr" data-title="Vodeni sat" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Jam_air" title="Jam air – Indonesian" lang="id" hreflang="id" data-title="Jam air" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Orologio_idraulico" title="Orologio idraulico – Italian" lang="it" hreflang="it" data-title="Orologio idraulico" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%A9%D7%A2%D7%95%D7%9F_%D7%9E%D7%99%D7%9D" title="שעון מים – Hebrew" lang="he" hreflang="he" data-title="שעון מים" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%A1%D1%83_%D1%81%D0%B0%D2%93%D0%B0%D1%82%D1%8B" title="Су сағаты – Kazakh" lang="kk" hreflang="kk" data-title="Су сағаты" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Vandens_laikrodis" title="Vandens laikrodis – Lithuanian" lang="lt" hreflang="lt" data-title="Vandens laikrodis" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/V%C3%ADz%C3%B3ra_(id%C5%91m%C3%A9r%C5%91)" title="Vízóra (időmérő) – Hungarian" lang="hu" hreflang="hu" data-title="Vízóra (időmérő)" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-arz mw-list-item"><a href="https://arz.wikipedia.org/wiki/%D9%83%D9%84%D9%8A%D8%A8%D8%B3%D9%8A%D8%AF%D8%B1%D8%A7" title="كليبسيدرا – Egyptian Arabic" lang="arz" hreflang="arz" data-title="كليبسيدرا" data-language-autonym="مصرى" data-language-local-name="Egyptian Arabic" class="interlanguage-link-target"><span>مصرى</span></a></li><li class="interlanguage-link interwiki-ms badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://ms.wikipedia.org/wiki/Jam_air" title="Jam air – Malay" lang="ms" hreflang="ms" data-title="Jam air" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Wateruurwerk" title="Wateruurwerk – Dutch" lang="nl" hreflang="nl" data-title="Wateruurwerk" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ne mw-list-item"><a href="https://ne.wikipedia.org/wiki/%E0%A4%9C%E0%A4%B2_%E0%A4%98%E0%A4%A1%E0%A5%80" title="जल घडी – Nepali" lang="ne" hreflang="ne" data-title="जल घडी" data-language-autonym="नेपाली" data-language-local-name="Nepali" class="interlanguage-link-target"><span>नेपाली</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E6%B0%B4%E6%99%82%E8%A8%88" title="水時計 – Japanese" lang="ja" hreflang="ja" data-title="水時計" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Vannklokke" title="Vannklokke – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Vannklokke" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Rel%C3%B2tge_d%27aiga" title="Relòtge d'aiga – Occitan" lang="oc" hreflang="oc" data-title="Relòtge d'aiga" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Zegar_wodny" title="Zegar wodny – Polish" lang="pl" hreflang="pl" data-title="Zegar wodny" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Clepsidra" title="Clepsidra – Portuguese" lang="pt" hreflang="pt" data-title="Clepsidra" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%92%D0%BE%D0%B4%D1%8F%D0%BD%D1%8B%D0%B5_%D1%87%D0%B0%D1%81%D1%8B" title="Водяные часы – Russian" lang="ru" hreflang="ru" data-title="Водяные часы" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Water_clock" title="Water clock – Simple English" lang="en-simple" hreflang="en-simple" data-title="Water clock" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Vodna_ura" title="Vodna ura – Slovenian" lang="sl" hreflang="sl" data-title="Vodna ura" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%92%D0%BE%D0%B4%D0%B5%D0%BD%D0%B8_%D1%87%D0%B0%D1%81%D0%BE%D0%B2%D0%BD%D0%B8%D0%BA" title="Водени часовник – Serbian" lang="sr" hreflang="sr" data-title="Водени часовник" data-language-autonym="Српски / srpski" 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id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Time-piece in which time is measured by the flow of liquid into or out of a vessel</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For the individual water clock at The Children's Museum of Indianapolis, see <a href="/wiki/Water_clock_(Indianapolis)" title="Water clock (Indianapolis)">Water clock (Indianapolis)</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:AGMA_Clepsydre.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/ff/AGMA_Clepsydre.jpg/220px-AGMA_Clepsydre.jpg" decoding="async" width="220" height="307" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/ff/AGMA_Clepsydre.jpg/330px-AGMA_Clepsydre.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/ff/AGMA_Clepsydre.jpg/440px-AGMA_Clepsydre.jpg 2x" data-file-width="800" data-file-height="1115" /></a><figcaption>A display of two outflow water clocks from the Ancient Agora Museum in Athens. The top is an original from the late 5th century BC. The bottom is a reconstruction of a clay original.</figcaption></figure> <p>A <b>water clock </b> or <b>clepsydra</b> (from <a href="/wiki/Ancient_Greek_language" class="mw-redirect" title="Ancient Greek language">Ancient Greek</a> <i> </i><span lang="grc"><a href="https://en.wiktionary.org/wiki/%CE%BA%CE%BB%CE%B5%CF%88%CF%8D%CE%B4%CF%81%CE%B1#Ancient_Greek" class="extiw" title="wikt:κλεψύδρα">κλεψύδρα</a></span><i> (<span title="Ancient Greek transliteration" lang="grc-Latn"><i>klepsúdra</i></span>)</i> '<a href="/wiki/Pipette" title="Pipette">pipette</a>, water clock'; from <i> </i><span lang="grc"><a href="https://en.wiktionary.org/wiki/%CE%BA%CE%BB%CE%AD%CF%80%CF%84%CF%89#Ancient_Greek" class="extiw" title="wikt:κλέπτω">κλέπτω</a></span><i> (<span title="Ancient Greek transliteration" lang="grc-Latn"><i>kléptō</i></span>)</i> 'to steal' and <i> </i><span lang="grc"><a href="https://en.wiktionary.org/wiki/%E1%BD%95%CE%B4%CF%89%CF%81#Ancient_Greek" class="extiw" title="wikt:ὕδωρ">ὕδωρ</a></span><i> (<span title="Ancient Greek transliteration" lang="grc-Latn"><i>hydor</i></span>)</i> 'water'; <abbr style="font-size:85%" title="literal translation">lit.</abbr><span style="white-space: nowrap;"> </span><span class="gloss-quot">'</span><span class="gloss-text"> water thief</span><span class="gloss-quot">'</span>) is a <a href="/wiki/Timepiece" class="mw-redirect" title="Timepiece">timepiece</a> by which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel, and where the amount of liquid can then be measured. </p><p>Water clocks are one of the oldest time-measuring instruments.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The simplest form of water clock, with a bowl-shaped outflow, existed in <a href="/wiki/Babylon" title="Babylon">Babylon</a>, <a href="/wiki/Ancient_Egypt" title="Ancient Egypt">Egypt</a>, and <a href="/wiki/History_of_Iran#Classical_antiquity" title="History of Iran">Persia</a> around the 16th century BC. Other regions of the world, including <a href="/wiki/History_of_India" title="History of India">India</a> and <a href="/wiki/History_of_China" title="History of China">China</a>, also provide early evidence of water clocks, but the earliest dates are less certain. Water clocks were used in <a href="/wiki/Ancient_Greece" title="Ancient Greece">ancient Greece</a> and in <a href="/wiki/Ancient_Rome" title="Ancient Rome">ancient Rome</a>, as described by technical writers such as <a href="/wiki/Ctesibius" title="Ctesibius">Ctesibius</a> (died 222 BC) and <a href="/wiki/Vitruvius" title="Vitruvius">Vitruvius</a> (died after 15 BC). </p> <style data-mw-deduplicate="TemplateStyles:r886046785">.mw-parser-output .toclimit-2 .toclevel-1 ul,.mw-parser-output .toclimit-3 .toclevel-2 ul,.mw-parser-output .toclimit-4 .toclevel-3 ul,.mw-parser-output .toclimit-5 .toclevel-4 ul,.mw-parser-output .toclimit-6 .toclevel-5 ul,.mw-parser-output .toclimit-7 .toclevel-6 ul{display:none}</style><div class="toclimit-3"><meta property="mw:PageProp/toc" /></div> <div class="mw-heading mw-heading2"><h2 id="Designs">Designs</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=1" title="Edit section: Designs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:1648_Eschinardi.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a7/1648_Eschinardi.jpg/220px-1648_Eschinardi.jpg" decoding="async" width="220" height="174" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a7/1648_Eschinardi.jpg/330px-1648_Eschinardi.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a7/1648_Eschinardi.jpg/440px-1648_Eschinardi.jpg 2x" data-file-width="4094" data-file-height="3235" /></a><figcaption>Eschinardi's water clock (Reproduced from <a href="/wiki/Francesco_Eschinardi" title="Francesco Eschinardi">Francesco Eschinardi</a>, <i>Appendix Ad Exodium de Tympano</i>)</figcaption></figure> <p>A water clock uses the flow of water to measure time. If viscosity is neglected, the physical principle required to study such clocks is <a href="/wiki/Torricelli%27s_law" title="Torricelli's law">Torricelli's law</a>. Two types of water clock exist: inflow and outflow. In an outflow water clock, a container is filled with water, and the water is drained slowly and evenly out of the container. This container has markings that are used to show the passage of time. As the water leaves the container, an observer can see where the water is level with the lines and tell how much time has passed. An inflow water clock works in basically the same way, except instead of flowing out of the container, the water is filling up the marked container. As the container fills, the observer can see where the water meets the lines and tell how much time has passed. Some modern timepieces are called "water clocks" but work differently from the ancient ones. Their timekeeping is governed by a <a href="/wiki/Pendulum" title="Pendulum">pendulum</a>, but they use water for other purposes, such as providing the power needed to drive the clock by using a <a href="/wiki/Water_wheel" title="Water wheel">water wheel</a> or something similar, or by having water in their displays. </p><p>The <a href="/wiki/Greeks" title="Greeks">Greeks</a> and Romans advanced water clock design to include the inflow clepsydra with an early feedback system, gearing, and <a href="/wiki/Escapement" title="Escapement">escapement</a> mechanism, which were connected to fanciful <a href="/wiki/Automaton" title="Automaton">automata</a> and resulted in improved accuracy. Further advances were made in <a href="/wiki/Byzantium" title="Byzantium">Byzantium</a>, Syria, and Mesopotamia, where increasingly accurate water clocks incorporated complex segmental and <a href="/wiki/Epicyclic_gearing" title="Epicyclic gearing">epicyclic gearing</a>, <a href="/wiki/Water_wheel" title="Water wheel">water wheels</a>, and <a href="/wiki/Program_(machine)" title="Program (machine)">programmability</a>, advances which eventually made their way to <a href="/wiki/Europe" title="Europe">Europe</a>. Independently, the Chinese developed their own advanced water clocks, incorporating gears, escapement mechanisms, and water wheels, passing their ideas on to <a href="/wiki/Korea" title="Korea">Korea</a> and <a href="/wiki/Japan" title="Japan">Japan</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (November 2011)">citation needed</span></a></i>]</sup> </p><p>Some water clock designs were developed independently, and some knowledge was transferred through the spread of trade. These early water clocks were calibrated with a <a href="/wiki/Sundial" title="Sundial">sundial</a>. While never reaching a level of accuracy comparable to today's standards of timekeeping, the water clock was a commonly used timekeeping device for millennia, until it was replaced by more accurate <a href="/wiki/Verge_escapement" title="Verge escapement">verge escapement</a> mechanical clocks in Europe around 1300.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Regional_development">Regional development</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=2" title="Edit section: Regional development"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Egypt">Egypt</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=3" title="Edit section: Egypt"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The oldest water clock of which there is physical evidence dates to c. 1417–1379 BC in the <a href="/wiki/New_Kingdom_of_Egypt" title="New Kingdom of Egypt">New Kingdom of Egypt</a>, during the reign of the pharaoh <a href="/wiki/Amenhotep_III" title="Amenhotep III">Amenhotep III</a>, where it was used in the <a href="/wiki/Precinct_of_Amun-Re" title="Precinct of Amun-Re">Precinct of Amun-Re</a> at <a href="/wiki/Karnak" title="Karnak">Karnak</a>.<sup id="cite_ref-FOOTNOTECotterellKamminga199059–61_3-0" class="reference"><a href="#cite_note-FOOTNOTECotterellKamminga199059–61-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The oldest documentation of the water clock is the tomb inscription of the 16th century BC Egyptian court official Amenemhet, which identifies him as its inventor.<sup id="cite_ref-FOOTNOTECotterellKamminga199059–61_3-1" class="reference"><a href="#cite_note-FOOTNOTECotterellKamminga199059–61-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> These simple water clocks, which were of the outflow type, were stone vessels with sloping sides that allowed water to drip at a nearly constant rate from a small hole near the bottom. There were twelve separate columns with consistently spaced markings on the inside to measure the passage of "hours" as the water level reached them. The columns were for each of the twelve <a href="/wiki/Month" title="Month">months</a> to allow for the variations of the seasonal hours. Priests used these clocks to determine the time at night so that the temple rites and sacrifices could be performed at the correct hour.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Babylon">Babylon</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=4" title="Edit section: Babylon"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox vcard"><tbody><tr><th colspan="2" class="infobox-above">Clay tablet</th></tr><tr><td colspan="2" class="infobox-image"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Water_clock_tablet.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/Water_clock_tablet.jpg/220px-Water_clock_tablet.jpg" decoding="async" width="220" height="158" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/Water_clock_tablet.jpg/330px-Water_clock_tablet.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/94/Water_clock_tablet.jpg/440px-Water_clock_tablet.jpg 2x" data-file-width="2889" data-file-height="2076" /></a></span><div class="infobox-caption">Water clock calculations by Nabû-apla-iddina.</div></td></tr><tr><th scope="row" class="infobox-label" style="white-space:nowrap;">Size</th><td class="infobox-data">H:8.2 cm (3.2 in)<br />W:11.8 cm (4.6 in)<br />D:2.5 cm (0.98 in)</td></tr><tr><th scope="row" class="infobox-label" style="white-space:nowrap;">Writing</th><td class="infobox-data"><a href="/wiki/Cuneiform" title="Cuneiform">cuneiform</a>, <a href="/wiki/Akkadian_(language)" class="mw-redirect" title="Akkadian (language)">Akkadian</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space:nowrap;">Created</th><td class="infobox-data">600BC-500BC</td></tr><tr><th scope="row" class="infobox-label" style="white-space:nowrap;">Present location</th><td class="infobox-data">Room 55, <a href="/wiki/British_Museum" title="British Museum">British Museum</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space:nowrap;">Identification</th><td class="infobox-data"><a rel="nofollow" class="external text" href="https://www.britishmuseum.org/collection/object/327283">29371 </a></td></tr></tbody></table> <p>In Babylon, water clocks were of the outflow type and were cylindrical in shape. Use of the water clock as an aid to astronomical calculations dates back to the <a href="/wiki/Old_Babylonian_Empire" title="Old Babylonian Empire">Old Babylonian Empire</a> (<i>c.</i> 2000 – <i>c.</i> 1600 BC).<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> While there are no surviving water clocks from the Mesopotamian region, most evidence of their existence comes from writings on <a href="/wiki/Clay_tablet" title="Clay tablet">clay tablets</a>. Two collections of tablets, for example, are the <i><a href="/wiki/Enuma_Anu_Enlil" title="Enuma Anu Enlil">Enuma Anu Enlil</a></i> (1600–1200 BC) and the <i><a href="/wiki/MUL.APIN" title="MUL.APIN">MUL.APIN</a></i> (7th century BC).<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> In these tablets, water clocks are used for payment of the night and day watches (guards).<sup id="cite_ref-FOOTNOTENeugebauer1947_8-0" class="reference"><a href="#cite_note-FOOTNOTENeugebauer1947-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>These clocks were unique, as they did not have an indicator such as hands (as are typically used today) or grooved notches (as were used in Egypt). Instead, these clocks measured time "by the weight of water flowing from" it.<sup id="cite_ref-neugebauer_9-0" class="reference"><a href="#cite_note-neugebauer-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> The volume was measured in capacity units called <i>qa</i>. The weight, <i>mana</i> or <a href="/wiki/Mina_(unit)" title="Mina (unit)">mina</a> (the Greek unit for about one pound), is the weight of water in a water clock.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (December 2020)">citation needed</span></a></i>]</sup> </p><p>In Babylonian times, time was measured with temporal hours. So, as seasons changed, so did the length of a day. "To define the length of a 'night watch' at the <a href="/wiki/Summer_solstice" title="Summer solstice">summer solstice</a>, one had to pour two mana of water into a cylindrical clepsydra; its emptying indicated the end of the watch. One-sixth of mana had to be added each succeeding half-month. At the <a href="/wiki/Equinox" title="Equinox">equinox</a>, three mana had to be emptied in order to correspond to one watch, and four mana was emptied for each watch of the <a href="/wiki/Winter_solstice" title="Winter solstice">winter solstitial night</a>."<sup id="cite_ref-neugebauer_9-1" class="reference"><a href="#cite_note-neugebauer-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="India">India</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=5" title="Edit section: India"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Hindu_units_of_time" title="Hindu units of time">Hindu units of time</a></div> <p>N. Narahari Achar and <a href="/wiki/Subhash_Kak" title="Subhash Kak">Subhash Kak</a> suggest that water clocks were used in <a href="/wiki/History_of_India" title="History of India">ancient India</a> as early as the 2nd millennium BC, based on their appearance in the <i><a href="/wiki/Atharvaveda" title="Atharvaveda">Atharvaveda</a>'.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup></i> According to N. Kameswara Rao, pots excavated from the <a href="/wiki/Indus_Valley_Civilisation" title="Indus Valley Civilisation">Indus Valley Civilisation</a> site of <a href="/wiki/Mohenjo-daro" title="Mohenjo-daro">Mohenjo-daro</a> may have been used as water clocks. They are tapered at the bottom, have a hole on the side, and are similar to the utensil used to perform <i><a href="/wiki/Abhi%E1%B9%A3eka" class="mw-redirect" title="Abhiṣeka">abhiṣeka</a></i> (ritual water pouring) on <a href="/wiki/Lingam" title="Lingam">lingams</a>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Jyotisha" class="mw-redirect" title="Jyotisha">Jyotisha</a>, one of the six <a href="/wiki/Vedanga" title="Vedanga">Vedanga</a> disciplines, describes water clocks called <i>ghati</i> or <i>kapala</i> that measure time in units of <i>nadika</i> (around 24 minutes). A clepsydra in the form of a floating and sinking copper vessel is mentioned in the <i><a href="/wiki/S%C3%BCrya_Siddh%C4%81nta" class="mw-redirect" title="Sürya Siddhānta">Sürya Siddhānta</a></i> (5th century AD).<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> At <a href="/wiki/Nalanda_mahavihara" title="Nalanda mahavihara">Nalanda mahavihara</a>, an <a href="/wiki/Ancient_higher-learning_institutions" title="Ancient higher-learning institutions">ancient Buddhist university</a>, four-hour intervals were measured by a water clock, which consisted of a similar copper bowl holding two large floats in a larger bowl filled with water. The bowl was filled with water from a small hole at its bottom; it sank when filled and was marked by the beating of a drum in the daytime. The amount of water added varied with the seasons, and students at the university operated the clock.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p><p>Descriptions of similar water clocks are also given in the <i><a href="/wiki/Pancha-Siddhantika" class="mw-redirect" title="Pancha-Siddhantika">Pañca Siddhāntikā</a></i> by the polymath <a href="/wiki/Var%C4%81hamihira" title="Varāhamihira">Varāhamihira</a> in the 6th century, which adds further detail to the account given in the <i>Sūrya Siddhānta</i>.<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citing_sources#What_information_to_include" title="Wikipedia:Citing sources"><span title="A complete citation is needed. (July 2019)">full citation needed</span></a></i>]</sup> Further descriptions are recorded in the <i><a href="/wiki/Br%C4%81hmasphu%E1%B9%ADasiddh%C4%81nta" title="Brāhmasphuṭasiddhānta">Brāhmasphuṭasiddhānta</a></i> by the mathematician <a href="/wiki/Brahmagupta" title="Brahmagupta">Brahmagupta</a> in the 7th century. A detailed description with measurements is also recorded by the astronomer <a href="/wiki/Lalla" title="Lalla">Lalla</a> in the 8th century, who describes the <i>ghati</i> as a hemispherical copper vessel with a hole that is fully filled after one <i>nadika</i>.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="China">China</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=6" title="Edit section: China"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Clock_Tower_from_Su_Song%27s_Book_desmear.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/46/Clock_Tower_from_Su_Song%27s_Book_desmear.JPG/220px-Clock_Tower_from_Su_Song%27s_Book_desmear.JPG" decoding="async" width="220" height="331" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/46/Clock_Tower_from_Su_Song%27s_Book_desmear.JPG/330px-Clock_Tower_from_Su_Song%27s_Book_desmear.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/46/Clock_Tower_from_Su_Song%27s_Book_desmear.JPG/440px-Clock_Tower_from_Su_Song%27s_Book_desmear.JPG 2x" data-file-width="908" data-file-height="1366" /></a><figcaption>The water-powered mechanism of <a href="/wiki/Su_Song" title="Su Song">Su Song</a>'s astronomical clock tower, featuring a clepsydra tank, <a href="/wiki/Waterwheel" class="mw-redirect" title="Waterwheel">waterwheel</a>, <a href="/wiki/Escapement" title="Escapement">escapement</a> mechanism, and <a href="/wiki/Chain_drive" title="Chain drive">chain drive</a> to power an <a href="/wiki/Armillary_sphere" title="Armillary sphere">armillary sphere</a> and 113 <a href="/wiki/Striking_clock" title="Striking clock">striking clock</a> jacks to sound the hours and to display informative plaques</figcaption></figure> <p>In <a href="/wiki/Ancient_China" class="mw-redirect" title="Ancient China">ancient China</a>, as well as throughout East Asia, water clocks were very important in the study of <a href="/wiki/Astronomy" title="Astronomy">astronomy</a> and <a href="/wiki/Astrology" title="Astrology">astrology</a>. The oldest written reference dates the use of the water clock in China to the 6th century BC.<sup id="cite_ref-needham479_16-0" class="reference"><a href="#cite_note-needham479-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> From about 200 BC onwards, the outflow clepsydra was replaced almost everywhere in China by the inflow type with an indicator-rod borne on a float(called fou chien lou,浮箭漏).<sup id="cite_ref-needham479_16-1" class="reference"><a href="#cite_note-needham479-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> The Han dynasty philosopher and politician <a href="/wiki/Huan_Tan" title="Huan Tan">Huan Tan</a> (40 BC – AD 30), a Secretary at the Court in charge of clepsydrae, wrote that he had to compare clepsydrae with sundials because of how temperature and humidity affected their accuracy, demonstrating that the effects of evaporation, as well as of temperature on the speed at which water flows, were known at this time.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> The liquid in water clocks was liable to freezing, and had to be kept warm with torches, a problem that was solved in 976 by the Chinese astronomer and engineer <a href="/wiki/Zhang_Sixun" title="Zhang Sixun">Zhang Sixun</a>. His invention—a considerable improvement on Yi Xing's clock—used <a href="/wiki/Mercury_(element)" title="Mercury (element)">mercury</a> instead of water. Mercury is a liquid at room temperature, and freezes at −38.83 °C (−37.9 °F), lower than any air temperature common outside polar regions.<sup id="cite_ref-FOOTNOTETemple1986107_18-0" class="reference"><a href="#cite_note-FOOTNOTETemple1986107-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> Again, instead of using water, the early Ming Dynasty engineer Zhan Xiyuan (c. 1360–1380) created a sand-driven wheel clock, improved upon by Zhou Shuxue (c. 1530–1558).<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>The use of clepsydrae to drive mechanisms <a href="/wiki/Armillary_sphere" title="Armillary sphere">illustrating astronomical phenomena</a> began with the Han Dynasty polymath <a href="/wiki/Zhang_Heng" title="Zhang Heng">Zhang Heng</a> (78–139) in 117, who also employed a <a href="/wiki/Waterwheel" class="mw-redirect" title="Waterwheel">waterwheel</a>.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> Zhang Heng was the first in China to add an extra compensating tank between the reservoir and the inflow vessel, which solved the problem of the falling <a href="/wiki/Pressure_head" title="Pressure head">pressure head</a> in the reservoir tank.<sup id="cite_ref-needham479_16-2" class="reference"><a href="#cite_note-needham479-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Zhang's ingenuity led to the creation by the Tang dynasty mathematician and engineer <a href="/wiki/Yi_Xing" title="Yi Xing">Yi Xing</a> (683–727) and <a href="/wiki/Liang_Lingzan" title="Liang Lingzan">Liang Lingzan</a> in 725 of a clock driven by a waterwheel linkwork <a href="/wiki/Escapement" title="Escapement">escapement</a> mechanism.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> The same mechanism would be used by the Song dynasty polymath <a href="/wiki/Su_Song" title="Su Song">Su Song</a> (1020–1101) in 1088 to power his <a href="/wiki/Astronomical_clock" title="Astronomical clock">astronomical clock</a> tower, as well as a <a href="/wiki/Chain_drive" title="Chain drive">chain drive</a>.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Su_Song" title="Su Song">Su Song</a>'s clock tower, over 30 feet (9.1 m) tall, possessed a <a href="/wiki/Bronze" title="Bronze">bronze</a> power-driven armillary sphere for observations, an automatically rotating <a href="/wiki/Celestial_globe" title="Celestial globe">celestial globe</a>, and five front panels with doors that permitted the viewing of changing <a href="/wiki/Mannequin" title="Mannequin">mannequins</a> which rang bells or gongs, and held tablets indicating the hour or other special times of the day. In the 2000s, in <a href="/wiki/Beijing" title="Beijing">Beijing</a>'s <a href="/wiki/Gulou_and_Zhonglou_(Beijing)" class="mw-redirect" title="Gulou and Zhonglou (Beijing)">Drum Tower</a> an outflow clepsydra is operational and displayed for tourists. It is connected to automata so that every quarter-hour a small brass statue of a man claps his cymbals.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Persia">Persia</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=7" title="Edit section: Persia"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG/220px-Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG/330px-Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/37/Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG/440px-Ancient_water_clock_used_in_qanat_of_gonabad_2500_years_ago.JPG 2x" data-file-width="3264" data-file-height="2448" /></a><figcaption>Ancient Persian clock</figcaption></figure> <p>The use of water clocks in <a href="/wiki/Greater_Iran" title="Greater Iran">Greater Iran</a>, especially in the desert areas such as <a href="/wiki/Yazd" title="Yazd">Yazd</a>, <a href="/wiki/Isfahan" title="Isfahan">Isfahan</a>, <a href="/wiki/Zibad" title="Zibad">Zibad</a>, and <a href="/wiki/Gonabad" title="Gonabad">Gonabad</a>, dates back to 500 BC.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> Later, they were also used to determine the exact holy days of pre-Islamic religions such as <a href="/wiki/Nowruz" title="Nowruz">Nowruz</a> (<a href="/wiki/March_equinox" title="March equinox">March equinox</a>), <a href="/wiki/Mehregan" title="Mehregan">Mehregan</a> (<a href="/wiki/September_equinox" title="September equinox">September equinox</a>), <a href="/wiki/Tirgan" title="Tirgan">Tirgan</a> (<a href="/wiki/Summer_solstice" title="Summer solstice">summer solstice</a>) and <a href="/wiki/Yald%C4%81_Night" title="Yaldā Night">Yaldā Night</a> (<a href="/wiki/Winter_solstice" title="Winter solstice">winter solstice</a>) – the shortest, longest, and equal-length days and nights of the years. The water clocks, called <i>pengan</i> (and later <i>fenjan</i>) used were one of the most practical ancient tools for timing the yearly calendar.<sup id="cite_ref-Qanat_26-0" class="reference"><a href="#cite_note-Qanat-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-japan.mfa.gov.ir_27-0" class="reference"><a href="#cite_note-japan.mfa.gov.ir-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> The water clock was the most accurate and commonly used timekeeping device for calculating the amount or the time that a farmer must take water from a <a href="/wiki/Qanat" title="Qanat">qanat</a> or well for irrigation until more accurate current clocks replaced it.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>Persian water clocks were a practical, useful, and necessary tool for the qanat's shareholders to calculate the length of time they could divert water to their farms or gardens. The qanat was the only water source for agriculture and irrigation in arid area so a just and fair water distribution was very important. Therefore, a very fair and clever old person was elected to be the manager of the water clock or <i>mir āb</i>, and at least two full-time managers were needed to control and observe the number of hours and announce the exact time of the days and nights from sunrise to sunset because shareholders usually divided between day and night owners.<sup id="cite_ref-amordadnews.com_30-0" class="reference"><a href="#cite_note-amordadnews.com-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p><p>The Persian water clock consisted of a large pot full of water and a bowl with a small hole in the center. When the bowl became full of water, it would sink into the pot, and the manager would empty the bowl and again put it on the top of the water in the pot. He would record the number of times the bowl sank by putting small stones into a jar.<sup id="cite_ref-amordadnews.com_30-1" class="reference"><a href="#cite_note-amordadnews.com-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> The place where the clock was situated and its managers were collectively known as the <i>khane pengān</i>. Usually this would be the top floor of a public house, with west- and east-facing windows to show the time of sunset and sunrise. The <a href="/wiki/Zibad" title="Zibad">Zibad</a> water clock was in use until 1965,<sup id="cite_ref-japan.mfa.gov.ir_27-1" class="reference"><a href="#cite_note-japan.mfa.gov.ir-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> when it was replaced by modern clocks.<sup id="cite_ref-Qanat_26-1" class="reference"><a href="#cite_note-Qanat-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Greco-Roman_world">Greco-Roman world</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=8" title="Edit section: Greco-Roman world"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Clepsydra-Diagram-Fancy.jpeg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Clepsydra-Diagram-Fancy.jpeg/220px-Clepsydra-Diagram-Fancy.jpeg" decoding="async" width="220" height="352" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Clepsydra-Diagram-Fancy.jpeg/330px-Clepsydra-Diagram-Fancy.jpeg 1.5x, //upload.wikimedia.org/wikipedia/commons/7/7b/Clepsydra-Diagram-Fancy.jpeg 2x" data-file-width="375" data-file-height="600" /></a><figcaption>An early 19th-century illustration<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> of <a href="/wiki/Ctesibius" title="Ctesibius">Ctesibius</a>'s (285–222 BC) clepsydra from the 3rd century BC. The hour indicator ascends as water flows in. Also, a series of gears rotate a cylinder to correspond to the temporal hours.</figcaption></figure> <p>The word "<a href="https://en.wiktionary.org/wiki/%CE%BA%CE%BB%CE%B5%CF%88%CF%8D%CE%B4%CF%81%CE%B1#Ancient_Greek" class="extiw" title="wiktionary:κλεψύδρα">clepsydra</a>" comes from the Greek meaning "water thief".<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> The Greeks considerably advanced the water clock by tackling the problem of the diminishing flow. They introduced several types of the inflow clepsydra, one of which included the earliest feedback control system.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Ctesibius" title="Ctesibius">Ctesibius</a> invented an indicator system typical for later clocks such as the dial and pointer.<sup id="cite_ref-John_G._Landels_35_34-0" class="reference"><a href="#cite_note-John_G._Landels_35-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Ancient_Rome" title="Ancient Rome">Roman</a> engineer <a href="/wiki/Vitruvius" title="Vitruvius">Vitruvius</a> described early alarm clocks, working with gongs or trumpets.<sup id="cite_ref-John_G._Landels_35_34-1" class="reference"><a href="#cite_note-John_G._Landels_35-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> A commonly used water clock was the simple outflow clepsydra. This small earthenware vessel had a hole in its side near the base. In both Greek and Roman times, this type of clepsydra was used in courts for allocating periods of time to speakers. In important cases, such as when a person's life was at stake, it was filled completely, but for more minor cases, only partially. If proceedings were interrupted for any reason, such as to examine documents, the hole in the clepsydra was stopped with wax until the speaker was able to resume his pleading.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Clepsydrae_for_keeping_time">Clepsydrae for keeping time</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=9" title="Edit section: Clepsydrae for keeping time"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Some scholars suspect that the clepsydra may have been used as a stop-watch for imposing a time limit on clients' visits in <a href="/wiki/Athens" title="Athens">Athenian</a> brothels.<sup id="cite_ref-John_G._Landels_32_36-0" class="reference"><a href="#cite_note-John_G._Landels_32-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> Slightly later, in the early 3rd century BC, the <a href="/wiki/Hellenistic" class="mw-redirect" title="Hellenistic">Hellenistic</a> physician <a href="/wiki/Herophilos" title="Herophilos">Herophilos</a> employed a portable clepsydra on his house visits in <a href="/wiki/Alexandria" title="Alexandria">Alexandria</a> for measuring his patients' pulse-beats. By comparing the rate by age group with empirically obtained data sets, he was able to determine the intensity of the disorder.<sup id="cite_ref-John_G._Landels_32_36-1" class="reference"><a href="#cite_note-John_G._Landels_32-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p><p>Between 270 BC and AD 500, <a href="/wiki/Hellenistic_civilization" class="mw-redirect" title="Hellenistic civilization">Hellenistic</a> (<a href="/wiki/Ctesibius" title="Ctesibius">Ctesibius</a>, <a href="/wiki/Hero_of_Alexandria" title="Hero of Alexandria">Hero of Alexandria</a>, <a href="/wiki/Archimedes" title="Archimedes">Archimedes</a>) and <a href="/wiki/Ancient_Rome" title="Ancient Rome">Roman</a> <a href="/wiki/Horology" class="mw-redirect" title="Horology">horologists</a> and <a href="/wiki/Astronomer" title="Astronomer">astronomers</a> were developing more elaborate mechanized water clocks. The added complexity was aimed at regulating the flow and at providing fancier displays of the passage of time. For example, some water clocks rang <a href="/wiki/Bell_(instrument)" class="mw-redirect" title="Bell (instrument)">bells</a> and <a href="/wiki/Gong" title="Gong">gongs</a>, while others opened doors and windows to show figurines of people, or moved pointers, and dials. Some even displayed <a href="/wiki/Astrology" title="Astrology">astrological</a> models of the universe. The 3rd century BC engineer <a href="/wiki/Philo_of_Byzantium" title="Philo of Byzantium">Philo of Byzantium</a> referred in his works to water clocks already fitted with an escapement mechanism, the earliest known of its kind.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p><p>The biggest achievement of the invention of clepsydrae during this time, however, was by Ctesibius with his incorporation of gears and a dial indicator to automatically show the time as the lengths of the days changed throughout the year, because of the temporal timekeeping used during his day. Also, a Greek astronomer, <a href="/wiki/Andronicus_of_Cyrrhus" title="Andronicus of Cyrrhus">Andronicus of Cyrrhus</a>, supervised the construction of his Horologion, known today as the <a href="/wiki/Tower_of_the_Winds" title="Tower of the Winds">Tower of the Winds</a>, in the <a href="/wiki/Athens" title="Athens">Athens</a> marketplace (or <a href="/wiki/Agora" title="Agora">agora</a>) in the first half of the 1st century BC. This <a href="/wiki/Octagon" title="Octagon">octagonal</a> <a href="/wiki/Clocktower" class="mw-redirect" title="Clocktower">clocktower</a> showed scholars and shoppers both <a href="/wiki/Sundial" title="Sundial">sundials</a> and a <a href="/wiki/Windvane" class="mw-redirect" title="Windvane">windvane</a>. Inside it was a mechanized clepsydra, although the type of display it used cannot be known for sure; some possibilities are: a rod that moved up and down to display the time, a water-powered <a href="/wiki/Automaton" title="Automaton">automaton</a> that struck a bell to mark the hours, or a moving star disk in the ceiling.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Medieval_Islamic_world">Medieval Islamic world</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=10" title="Edit section: Medieval Islamic world"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Al-jazari_elephant_clock.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Al-jazari_elephant_clock.png/220px-Al-jazari_elephant_clock.png" decoding="async" width="220" height="345" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/76/Al-jazari_elephant_clock.png/330px-Al-jazari_elephant_clock.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/76/Al-jazari_elephant_clock.png/440px-Al-jazari_elephant_clock.png 2x" data-file-width="1013" data-file-height="1587" /></a><figcaption><a href="/wiki/Al-Jazari" class="mw-redirect" title="Al-Jazari">Al-Jazari</a>'s <a href="/wiki/Elephant_clock" title="Elephant clock">elephant water clock</a> (1206).<sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup></figcaption></figure> <p>In the <a href="/wiki/Islamic_Golden_Age" title="Islamic Golden Age">medieval Islamic world</a> (632-1280), the use of water clocks has its roots from Archimedes during the rise of <a href="/wiki/Alexandria" title="Alexandria">Alexandria</a> in <a href="/wiki/Egypt" title="Egypt">Egypt</a> and continues on through <a href="/wiki/Byzantium" title="Byzantium">Byzantium</a>. The water clocks by the Arabic engineer <a href="/wiki/Al-Jazari" class="mw-redirect" title="Al-Jazari">Al-Jazari</a>, however, are credited for going "well beyond anything" that had preceded them. In Al-Jazari's 1206 treatise, he describes one of his water clocks, the <a href="/wiki/Elephant_clock" title="Elephant clock">elephant clock</a>. The clock recorded the passage of temporal hours, which meant that the rate of flow had to be changed daily to match the uneven length of days throughout the year. To accomplish this, the clock had two tanks, the top tank was connected to the time indicating mechanisms and the bottom was connected to the <a href="/wiki/Regulator_(automatic_control)" title="Regulator (automatic control)">flow control regulator</a>. Basically, at daybreak, the tap was opened and water flowed from the top tank to the bottom tank via a float regulator that maintained a constant pressure in the receiving tank.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Clock_of_al_Jazari_before_1206.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Clock_of_al_Jazari_before_1206.jpg/220px-Clock_of_al_Jazari_before_1206.jpg" decoding="async" width="220" height="285" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Clock_of_al_Jazari_before_1206.jpg/330px-Clock_of_al_Jazari_before_1206.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/3/3d/Clock_of_al_Jazari_before_1206.jpg 2x" data-file-width="384" data-file-height="497" /></a><figcaption>Water-powered automatic <a href="/wiki/Castle_clock" class="mw-redirect" title="Castle clock">castle clock</a> of <a href="/wiki/Al-Jazari" class="mw-redirect" title="Al-Jazari">Al-Jazari</a>, 12th century.</figcaption></figure> <p>The most sophisticated water-powered <a href="/wiki/Astronomical_clock" title="Astronomical clock">astronomical clock</a> was <a href="/wiki/Al-Jazari" class="mw-redirect" title="Al-Jazari">Al-Jazari</a>'s <a href="/wiki/Castle_clock" class="mw-redirect" title="Castle clock">castle clock</a>, considered by some to be an early example of a programmable <a href="/wiki/Analog_computer" title="Analog computer">analog computer</a>, in 1206.<sup id="cite_ref-Ancient_Discoveries_41-0" class="reference"><a href="#cite_note-Ancient_Discoveries-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> It was a complex device that was about 11 feet (3.4 m) high, and had multiple functions alongside timekeeping. It included a display of the <a href="/wiki/Zodiac" title="Zodiac">zodiac</a> and the solar and lunar orbits, and a pointer in the shape of the crescent moon which traveled across the top of a gateway, moved by a hidden cart and causing automatic doors to open, each revealing a mannequin, every hour.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hill2_43-0" class="reference"><a href="#cite_note-Hill2-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> It was possible to re-program the length of day and night in order to account for the changing lengths of day and night throughout the year, and it also featured five musician automata who automatically play music when moved by levers operated by a hidden camshaft attached to a water wheel.<sup id="cite_ref-Ancient_Discoveries_41-1" class="reference"><a href="#cite_note-Ancient_Discoveries-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> Other components of the castle clock included a main reservoir with a float, a <a href="/wiki/Float_chamber" title="Float chamber">float chamber</a> and flow regulator, plate and valve trough, two pulleys, crescent disc displaying the zodiac, and two falcon <a href="/wiki/Automaton" title="Automaton">automata</a> dropping balls into vases.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Reliable_sources" title="Wikipedia:Reliable sources"><span title="The material near this tag relies on an unreliable source. This is just a link to a google search for the preceding phrase" (March 2017)">unreliable source</span></a></i>]</sup> </p><p>The first water clocks to employ complex segmental and <a href="/wiki/Epicyclic_gearing" title="Epicyclic gearing">epicyclic gearing</a> was invented earlier by the <a href="/wiki/Arab" class="mw-redirect" title="Arab">Arab</a> engineer <a href="/wiki/Ibn_Khalaf_al-Muradi" title="Ibn Khalaf al-Muradi">Ibn Khalaf al-Muradi</a> in <a href="/wiki/Al-Andalus" title="Al-Andalus">Islamic Iberia</a> c. 1000. His water clocks were driven by <a href="/wiki/Water_wheel" title="Water wheel">water wheels</a>, as was also the case for several Chinese water clocks in the 11th century.<sup id="cite_ref-Hassan_45-0" class="reference"><a href="#cite_note-Hassan-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> Comparable water clocks were built in <a href="/wiki/Damascus" title="Damascus">Damascus</a> and <a href="/wiki/Fes,_Morocco" class="mw-redirect" title="Fes, Morocco">Fez</a>. The latter (<a href="/wiki/Dar_al-Magana" title="Dar al-Magana">Dar al-Magana</a>) remains until today and its mechanism has been reconstructed. The first European clock to employ these complex gears was the astronomical clock created by <a href="/wiki/Giovanni_Dondi_dell%27Orologio" class="mw-redirect" title="Giovanni Dondi dell'Orologio">Giovanni de Dondi</a> in c. 1365. Like the Chinese, Arab engineers at the time also developed an <a href="/wiki/Escapement" title="Escapement">escapement</a> mechanism which they employed in some of their water clocks. The escapement mechanism was in the form of a constant-head system, while heavy floats were used as weights.<sup id="cite_ref-Hassan_45-1" class="reference"><a href="#cite_note-Hassan-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Korea">Korea</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=11" title="Edit section: Korea"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Jang_Yeong-sil#Water_Clock" title="Jang Yeong-sil">Jang Yeong-sil § Water Clock</a></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:BoRuGak_Jagyeongnu.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/BoRuGak_Jagyeongnu.JPG/220px-BoRuGak_Jagyeongnu.JPG" decoding="async" width="220" height="293" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/BoRuGak_Jagyeongnu.JPG/330px-BoRuGak_Jagyeongnu.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/67/BoRuGak_Jagyeongnu.JPG/440px-BoRuGak_Jagyeongnu.JPG 2x" data-file-width="1848" data-file-height="2464" /></a><figcaption>Jang Yeong-sil's self-striking water clock, the <a href="/wiki/Borugak_Jagyeongnu" title="Borugak Jagyeongnu">Borugak Jagyeongnu</a></figcaption></figure> <p>In 718, <a href="/wiki/Unified_Silla" title="Unified Silla">Unified Silla</a> established the system of clepsydra for the first time in Korean history, imitating the Tang Dynasty.<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> In 1434, during <a href="/wiki/Joseon" title="Joseon">Joseon</a> rule, <a href="/wiki/Jang_Yeong-sil" title="Jang Yeong-sil">Jang Yeong-sil</a> (<a href="/wiki/Korean_language" title="Korean language">Korean</a>: <span title="Korean-language text"><span lang="ko-Hang">장영실</span></span>; <a href="/wiki/Hanja" title="Hanja">Hanja</a>: <span title="Korean-language text"><span lang="ko-Hani">蔣英實</span></span>), a palace guard and later chief court engineer, constructed the <a href="/wiki/Borugak_Jagyeongnu" title="Borugak Jagyeongnu">Borugak Jagyeongnu</a> or self-striking water clock of Borugak Pavillion for <a href="/wiki/Sejong_the_Great" title="Sejong the Great">Sejong the Great</a>. </p><p>What made his water clock self-striking (or automatic) was using jack-work mechanisms: three wooden figures or "jacks" struck objects to signal the time. This innovation no longer required the reliance of human workers, known as "rooster men", to constantly replenish it.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (December 2020)">citation needed</span></a></i>]</sup> </p><p>The uniqueness of the clock was its capability to announce dual-times automatically with visual and audible signals.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> Jang developed a signal conversion technique that made it possible to measure analog time and announce digital time simultaneously as well as to separate the water mechanisms from the ball-operated striking mechanisms.<sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> The conversion device was called <i>pangmok</i>, and was placed above the inflow vessel that measured the time, the first device of its kind in the world.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> Thus, the Borugak water clock is the first hydro-mechanically engineered dual-time clock in the history of horology.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Japan">Japan</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=12" title="Edit section: Japan"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Emperor_Tenji" title="Emperor Tenji">Emperor Tenji</a> made Japan's first water clock called a Rokoku<span style="font-weight: normal"> (<span title="Japanese-language text"><span lang="ja">漏刻</span></span>)</span>. They were highly socially significant and run by <a href="/w/index.php?title=R%C5%8Dkoku_Hakase&action=edit&redlink=1" class="new" title="Rōkoku Hakase (page does not exist)">Doctors of Water Clock</a><span class="noprint" style="font-size:85%; font-style: normal;"> [<a href="https://ja.wikipedia.org/wiki/%E6%BC%8F%E5%88%BB%E5%8D%9A%E5%A3%AB" class="extiw" title="ja:漏刻博士">ja</a>]</span> </p> <div class="mw-heading mw-heading2"><h2 id="Temperature,_water_viscosity,_and_clock_accuracy"><span id="Temperature.2C_water_viscosity.2C_and_clock_accuracy"></span>Temperature, water viscosity, and clock accuracy</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=13" title="Edit section: Temperature, water viscosity, and clock accuracy"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When viscosity can be neglected, the outflow rate of the water is governed by <a href="/wiki/Torricelli%27s_law" title="Torricelli's law">Torricelli's law</a>, or more generally, by <a href="/wiki/Bernoulli%27s_principle" title="Bernoulli's principle">Bernoulli's principle</a>. <a href="/wiki/Viscosity" title="Viscosity">Viscosity</a> will dominate the outflow rate if the water flows out through a nozzle that is sufficiently long and thin, as given by the <a href="/wiki/Hagen%E2%80%93Poiseuille_equation" title="Hagen–Poiseuille equation">Hagen–Poiseuille equation</a>.<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> Approximately, the flow rate is for such design <a href="/wiki/Inversely_proportional" class="mw-redirect" title="Inversely proportional">inversely proportional</a> to the viscosity, which depends on the <a href="/wiki/Temperature" title="Temperature">temperature</a>. <a href="/wiki/Liquid" title="Liquid">Liquids</a> generally become less viscous as the temperature increases. In the case of water, the viscosity varies by a factor of about seven between zero and 100 degrees Celsius. Thus, a water clock with such a nozzle would run about seven times faster at 100 °C than at 0 °C. Water is about 25 percent more viscous at 20 °C than at 30 °C, and a variation in temperature of one degree Celsius, in this "<a href="/wiki/Room_temperature" title="Room temperature">room temperature</a>" range, produces a change of viscosity of about two percent.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup> Therefore, a water clock with such a nozzle that keeps good time at some given temperature would gain or lose about half an hour per day if it were one degree Celsius warmer or cooler. To make it keep time within one minute per day would require its temperature to be controlled within <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">1</span>⁄<span class="den">30</span></span>°C (about <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027"><span class="frac"><span class="num">1</span>⁄<span class="den">17</span></span>°F). There is no evidence that this was done in antiquity, so ancient water clocks with sufficiently thin and long nozzles (unlike the modern pendulum-controlled one described above) cannot have been reliably accurate by modern standards. However, while modern timepieces may not be reset for long periods, water clocks were likely reset every day, when refilled, based on a sundial, so the cumulative error would not have been great.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (December 2020)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Bernard_Gitton" title="Bernard Gitton">Bernard Gitton</a></li> <li><a href="/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History of timekeeping devices</a></li> <li><a href="/wiki/Hourglass" title="Hourglass">Hourglass</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=15" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width reflist-columns-2"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><a href="#CITEREFTurner1984">Turner 1984</a>, p. 1</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFMills1982" class="citation journal cs1">Mills, A. A. (August 1982). <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/531476">"Newton's Water Clocks and the Fluid Mechanics of Clepsydrae"</a>. <i>Notes and Records of the Royal Society of London</i>. <b>37</b> (1): 35–61. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1098%2Frsnr.1982.0004">10.1098/rsnr.1982.0004</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/531476">531476</a><span class="reference-accessdate">. Retrieved <span class="nowrap">18 June</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Notes+and+Records+of+the+Royal+Society+of+London&rft.atitle=Newton%27s+Water+Clocks+and+the+Fluid+Mechanics+of+Clepsydrae&rft.volume=37&rft.issue=1&rft.pages=35-61&rft.date=1982-08&rft_id=info%3Adoi%2F10.1098%2Frsnr.1982.0004&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F531476%23id-name%3DJSTOR&rft.aulast=Mills&rft.aufirst=A.+A.&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F531476&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-FOOTNOTECotterellKamminga199059–61-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-FOOTNOTECotterellKamminga199059–61_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-FOOTNOTECotterellKamminga199059–61_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a href="#CITEREFCotterellKamminga1990">Cotterell & Kamminga 1990</a>, pp. 59–61.</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBerlev1997" class="citation book cs1">Berlev, Oleg (1997). "Bureaucrats". In Donadoni, Sergio (ed.). <i>The Egyptians</i>. Trans. Bianchi, Robert <i>et al</i>. Chicago: The University of Chicago Press. p. 118. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-226-15555-2" title="Special:BookSources/0-226-15555-2"><bdi>0-226-15555-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Bureaucrats&rft.btitle=The+Egyptians&rft.place=Chicago&rft.pages=118&rft.pub=The+University+of+Chicago+Press&rft.date=1997&rft.isbn=0-226-15555-2&rft.aulast=Berlev&rft.aufirst=Oleg&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><a href="#CITEREFCotterellKamminga1990">Cotterell & Kamminga 1990</a></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPingree1998" class="citation book cs1"><a href="/wiki/David_Pingree" title="David Pingree">Pingree, David</a> (1998). "Legacies in Astronomy and Celestial Omens". In <a href="/wiki/Stephanie_Dalley" title="Stephanie Dalley">Stephanie Dalley</a> (ed.). <i>The Legacy of Mesopotamia</i>. Oxford: Oxford University Press. pp. 125–126. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-19-814946-8" title="Special:BookSources/0-19-814946-8"><bdi>0-19-814946-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Legacies+in+Astronomy+and+Celestial+Omens&rft.btitle=The+Legacy+of+Mesopotamia&rft.place=Oxford&rft.pages=125-126&rft.pub=Oxford+University+Press&rft.date=1998&rft.isbn=0-19-814946-8&rft.aulast=Pingree&rft.aufirst=David&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFEvans1998" class="citation book cs1">Evans, James (1998). <i>The History and Practice of Ancient Astronomy</i>. 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Retrieved <span class="nowrap">2007-05-11</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Electronic+Journal+of+Vedic+Studies&rft.atitle=On+the+meaning+of+AV+XIX.+53.3%3A+Measurement+of+Time%3F&rft.date=1998-12&rft.aulast=Achar&rft.aufirst=N.+Narahari&rft_id=http%3A%2F%2Fwww.ejvs.laurasianacademy.com%2Fejvs0402%2Fejvs0402.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKak2003" class="citation book cs1 cs1-prop-long-vol"><a href="/wiki/Subhash_Kak" title="Subhash Kak">Kak, Subhash</a> (2003-02-17). "Babylonian and Indian Astronomy: Early Connections". In Pande, G. C. (ed.). <i>History of Science, Philosophy & Culture in Indian Civilization</i>. Vol. 1 Part 4. pp. 847–869. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/physics/0301078">physics/0301078</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2003physics...1078K">2003physics...1078K</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Babylonian+and+Indian+Astronomy%3A+Early+Connections&rft.btitle=History+of+Science%2C+Philosophy+%26+Culture+in+Indian+Civilization&rft.pages=847-869&rft.date=2003-02-17&rft_id=info%3Aarxiv%2Fphysics%2F0301078&rft_id=info%3Abibcode%2F2003physics...1078K&rft.aulast=Kak&rft.aufirst=Subhash&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRao2005" class="citation journal cs1">Rao, N. Kameswara (December 2005). <a rel="nofollow" class="external text" href="http://www.ncra.tifr.res.in/~basi/05December/3305499-511.pdf">"Aspects of prehistoric astronomy in India"</a> <span class="cs1-format">(PDF)</span>. <i>Bulletin of the Astronomical Society of India</i>. <b>33</b> (4): 499–511. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005BASI...33..499R">2005BASI...33..499R</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2007-05-11</span></span>. <q>It appears that two artifacts from Mohenjo-daro and Harappa might correspond to these two instruments. Joshi and Parpola (1987) lists a few pots tapered at the bottom and having a hole on the side from the excavations at Mohenjadaro (Figure 3). A pot with a small hole to drain the water is very similar to clepsydras described by Ohashi to measure the time (similar to the utensil used over the lingum in Shiva temple for abhishekam).</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Bulletin+of+the+Astronomical+Society+of+India&rft.atitle=Aspects+of+prehistoric+astronomy+in+India&rft.volume=33&rft.issue=4&rft.pages=499-511&rft.date=2005-12&rft_id=info%3Abibcode%2F2005BASI...33..499R&rft.aulast=Rao&rft.aufirst=N.+Kameswara&rft_id=http%3A%2F%2Fwww.ncra.tifr.res.in%2F~basi%2F05December%2F3305499-511.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text">"A copper vessel (in the shape of the lower half of the water jar) which has a small hole in its bottom and being placed upon clean water in a basin sinks exactly 60 times in a day and at night." – Chapter 13, verse 23 of the <i>Sürya Siddhānta</i>.</span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFScharfe2002" class="citation book cs1">Scharfe, Hartmut (2002). <span class="id-lock-limited" title="Free access subject to limited trial, subscription normally required"><a rel="nofollow" class="external text" href="https://archive.org/details/educationancient00scha"><i>Education in Ancient India</i></a></span>. Leiden: Brill Academic Publishers. p. <a rel="nofollow" class="external text" href="https://archive.org/details/educationancient00scha/page/n177">171</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/90-04-12556-6" title="Special:BookSources/90-04-12556-6"><bdi>90-04-12556-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Education+in+Ancient+India&rft.place=Leiden&rft.pages=171&rft.pub=Brill+Academic+Publishers&rft.date=2002&rft.isbn=90-04-12556-6&rft.aulast=Scharfe&rft.aufirst=Hartmut&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Feducationancient00scha&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">"A copper vessel weighing 10 palas, 6 angulas in height and twice as much in breadth at the mouth—this vessel of the capacity of 60 palas of water and hemispherical in form is called a ghati." This copper vessel, which was bored with a needle and made of 3 1/8 masas of gold and 4 angulas long, gets filled in one nadika."<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citing_sources#What_information_to_include" title="Wikipedia:Citing sources"><span title="A complete citation is needed. (July 2019)">full citation needed</span></a></i>]</sup></span> </li> <li id="cite_note-needham479-16"><span class="mw-cite-backlink">^ <a href="#cite_ref-needham479_16-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-needham479_16-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-needham479_16-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><a href="#CITEREFNeedham2000">Needham 2000</a>, p. 479</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham1995">Needham 1995</a>, pp. 321–322</span> </li> <li id="cite_note-FOOTNOTETemple1986107-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-FOOTNOTETemple1986107_18-0">^</a></b></span> <span class="reference-text"><a href="#CITEREFTemple1986">Temple 1986</a>, p. 107.</span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.britannica.com/EBchecked/topic/375837">Mercury</a> at the <i><a href="/wiki/Encyclop%C3%A6dia_Britannica" title="Encyclopædia Britannica">Encyclopædia Britannica</a></i></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham1986">Needham 1986</a>, pp. 510–511</span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham2000">Needham 2000</a>, pp. 30, 532</span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham2000">Needham 2000</a>, pp. 471, 490, 532</span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><a href="#CITEREFNeedham2000">Needham 2000</a>, p. 462</span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFEllywa2007" class="citation web cs1">Ellywa (1 August 2007). <a class="external text" href="https://commons.wikimedia.org/wiki/Image:CIMG1106_Clepshydra_in_Drum_Tower,_Beijing_august_2007.JPG">"Clepsydra in the Drum Tower, Beijing, China"</a> – via Wikimedia Commons.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Clepsydra+in+the+Drum+Tower%2C+Beijing%2C+China&rft.date=2007-08-01&rft.au=Ellywa&rft_id=http%3A%2F%2Fcommons.wikimedia.org%2Fwiki%2FImage%3ACIMG1106_Clepshydra_in_Drum_Tower%2C_Beijing_august_2007.JPG&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRahimi" class="citation web cs1">Rahimi, G.H. <a rel="nofollow" class="external text" href="https://jihs.ut.ac.ir/article_69801_e14a6b2d0d61cd4df20e24ffd5b216a4.pdf">"Water Sharing Management in Ancient Iran, with Special Reference to Pangān (cup) in Iran"</a> <span class="cs1-format">(PDF)</span>. <i>Tehran university science magazine</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Tehran+university+science+magazine&rft.atitle=Water+Sharing+Management+in+Ancient+Iran%2C+with+Special+Reference+to+Pang%C4%81n+%28cup%29+in+Iran&rft.aulast=Rahimi&rft.aufirst=G.H.&rft_id=https%3A%2F%2Fjihs.ut.ac.ir%2Farticle_69801_e14a6b2d0d61cd4df20e24ffd5b216a4.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-Qanat-26"><span class="mw-cite-backlink">^ <a href="#cite_ref-Qanat_26-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Qanat_26-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1 cs1-prop-foreign-lang-source"><a rel="nofollow" class="external text" href="http://www.aftabir.com/articles/view/science_education/technical/c3c1183387267p1.php">"Conference of Qanat in Iran – water clock in Persia 1383"</a>. <i>www.aftabir.com</i> (in Persian).</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.aftabir.com&rft.atitle=Conference+of+Qanat+in+Iran+%E2%80%93+water+clock+in+Persia+1383&rft_id=http%3A%2F%2Fwww.aftabir.com%2Farticles%2Fview%2Fscience_education%2Ftechnical%2Fc3c1183387267p1.php&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-japan.mfa.gov.ir-27"><span class="mw-cite-backlink">^ <a href="#cite_ref-japan.mfa.gov.ir_27-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-japan.mfa.gov.ir_27-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://japan.mfa.gov.ir/en/newsview/536035">"Qanat is cultural and social and scientific heritage in Iran"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Qanat+is+cultural+and+social+and+scientific+heritage+in+Iran&rft_id=https%3A%2F%2Fjapan.mfa.gov.ir%2Fen%2Fnewsview%2F536035&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20170610061516/http://parssea.org/?p=2734">"Water clock or Pengan in Iran, National conference 2004 Gonabad"</a>. <i>parssea.org</i>. Archived from <a rel="nofollow" class="external text" href="http://parssea.org/?p=2734">the original</a> on 2017-06-10.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=parssea.org&rft.atitle=Water+clock+or+Pengan+in+Iran%2C+National+conference+2004+Gonabad&rft_id=http%3A%2F%2Fparssea.org%2F%3Fp%3D2734&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFvista.ir" class="citation web cs1">vista.ir. <a rel="nofollow" class="external text" href="http://vista.ir/article/265134">"Qanat iscultural and social and scientific heritage in Iran"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Qanat+iscultural+and+social+and+scientific+heritage+in+Iran&rft.au=vista.ir&rft_id=http%3A%2F%2Fvista.ir%2Farticle%2F265134&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-amordadnews.com-30"><span class="mw-cite-backlink">^ <a href="#cite_ref-amordadnews.com_30-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-amordadnews.com_30-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20140429163019/http://amordadnews.com/neveshtehNamyesh.aspx?NId=6010">"water clock in persia"</a>. <i>amordadnews.com</i>. Archived from <a rel="nofollow" class="external text" href="http://amordadnews.com/neveshtehNamyesh.aspx?NId=6010">the original</a> on 2014-04-29.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=amordadnews.com&rft.atitle=water+clock+in+persia&rft_id=http%3A%2F%2Famordadnews.com%2FneveshtehNamyesh.aspx%3FNId%3D6010&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text">This engraving is taken from "Rees's Clocks, Watches, and Chronometers 1819–20. The design of the illustration was modified from Claude Perrault's illustrations in his 1684 translation of Vitruvius's Les Dix Livres d'Architecture (1st century BC), of which he describes Ctesibius's clepsydra in great length.</span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLevy2004" class="citation book cs1">Levy, Janey (2004). <a rel="nofollow" class="external text" href="https://archive.org/details/keepingtimethrou0000levy/page/11"><i>Keeping Time Through the Ages: The History of Tools Used to Measure Time</i></a>. Rosen Classroom. p. <a rel="nofollow" class="external text" href="https://archive.org/details/keepingtimethrou0000levy/page/11">11</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780823989171" title="Special:BookSources/9780823989171"><bdi>9780823989171</bdi></a>. <q>The Greeks named the water clock 'clepsydra' (KLEP-suh-druh), which means 'water thief'.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Keeping+Time+Through+the+Ages%3A+The+History+of+Tools+Used+to+Measure+Time&rft.pages=11&rft.pub=Rosen+Classroom&rft.date=2004&rft.isbn=9780823989171&rft.aulast=Levy&rft.aufirst=Janey&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fkeepingtimethrou0000levy%2Fpage%2F11&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><a href="#CITEREFGoodenowOrrRoss2007">Goodenow, Orr & Ross (2007)</a>, p. 7</span> </li> <li id="cite_note-John_G._Landels_35-34"><span class="mw-cite-backlink">^ <a href="#cite_ref-John_G._Landels_35_34-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-John_G._Landels_35_34-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">John G. Landels: "Water-Clocks and Time Measurement in Classical Antiquity", "Endeavour", Vol. 3, No. 1 (1979), pp. 32–37 (35)</span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><a href="#CITEREFHill1981">Hill 1981</a>, p. 6</span> </li> <li id="cite_note-John_G._Landels_32-36"><span class="mw-cite-backlink">^ <a href="#cite_ref-John_G._Landels_32_36-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-John_G._Landels_32_36-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLandels1979" class="citation journal cs1">Landels, John G. (1979). "Water-Clocks and Time Measurement in Classical Antiquity". <i>Endeavour</i>. <b>3</b> (1): 33. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0160-9327%2879%2990007-3">10.1016/0160-9327(79)90007-3</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Endeavour&rft.atitle=Water-Clocks+and+Time+Measurement+in+Classical+Antiquity&rft.volume=3&rft.issue=1&rft.pages=33&rft.date=1979&rft_id=info%3Adoi%2F10.1016%2F0160-9327%2879%2990007-3&rft.aulast=Landels&rft.aufirst=John+G.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><a href="#CITEREFLewis2000">Lewis 2000</a>, pp. 356f.</span> </li> <li id="cite_note-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-38">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNoblede_Solla_Price1968" class="citation journal cs1">Noble, Joseph V.; de Solla Price, Derek (October 1968). <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/503828">"The Water Clock in the Tower of the Winds"</a>. <i>American Journal of Archaeology</i>. <b>72</b> (4): 345–355. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.2307%2F503828">10.2307/503828</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/503828">503828</a><span class="reference-accessdate">. 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Reidel. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/969-8016-25-2" title="Special:BookSources/969-8016-25-2"><bdi>969-8016-25-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Book+of+Knowledge+of+Ingenious+Mechanical+Devices&rft.place=Dordrecht&rft.pub=D.+Reidel&rft.date=1974&rft.isbn=969-8016-25-2&rft.au=ibn+al-Razzaz+al-Jazari&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-40">^</a></b></span> <span class="reference-text"><a href="#CITEREFal-HassanHill1986">al-Hassan & Hill 1986</a>, pp. 57–59</span> </li> <li id="cite_note-Ancient_Discoveries-41"><span class="mw-cite-backlink">^ <a href="#cite_ref-Ancient_Discoveries_41-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Ancient_Discoveries_41-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20140301151115/https://www.youtube.com/watch?v=rxjbaQl0ad8">"Ancient Discoveries, Episode 11: Ancient Robots"</a>. <a href="/wiki/History_(U.S._TV_channel)" class="mw-redirect" title="History (U.S. TV channel)">History Channel</a>. 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Turner (1997), <i>Science in Medieval Islam: An Illustrated Introduction</i>, p. 184. <a href="/wiki/University_of_Texas_Press" title="University of Texas Press">University of Texas Press</a>, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-292-78149-0" title="Special:BookSources/0-292-78149-0">0-292-78149-0</a>.</span> </li> <li id="cite_note-Hill2-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-Hill2_43-0">^</a></b></span> <span class="reference-text"><a href="/wiki/Donald_Routledge_Hill" class="mw-redirect" title="Donald Routledge Hill">Routledge Hill, Donald</a>, "Mechanical Engineering in the Medieval Near East", <i>Scientific American</i>, May 1991, pp. 64–69. (<a href="/wiki/Cf." title="Cf.">cf.</a> <a href="/wiki/Donald_Routledge_Hill" class="mw-redirect" title="Donald Routledge Hill">Donald Routledge Hill</a>, <a rel="nofollow" class="external text" href="http://home.swipnet.se/islam/articles/HistoryofSciences.htm">Mechanical Engineering</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071225091836/http://home.swipnet.se/islam/articles/HistoryofSciences.htm">Archived</a> 2007-12-25 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>)</span> </li> <li id="cite_note-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-44">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.google.com.my/search?hl=en&q=two+falcon+automata+dropping+balls+into+vases&um=1&ie=UTF-8&tbo=u&tbs=bks:1&source=og&sa=N&tab=wp">"two falcon automata dropping balls into vases – Google Search"</a>. <i>www.google.com.my</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.google.com.my&rft.atitle=two+falcon+automata+dropping+balls+into+vases+%E2%80%93+Google+Search&rft_id=http%3A%2F%2Fwww.google.com.my%2Fsearch%3Fhl%3Den%26q%3Dtwo%2Bfalcon%2Bautomata%2Bdropping%2Bballs%2Binto%2Bvases%26um%3D1%26ie%3DUTF-8%26tbo%3Du%26tbs%3Dbks%3A1%26source%3Dog%26sa%3DN%26tab%3Dwp&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-Hassan-45"><span class="mw-cite-backlink">^ <a href="#cite_ref-Hassan_45-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Hassan_45-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a href="/wiki/Ahmad_Y_Hassan" class="mw-redirect" title="Ahmad Y Hassan">Hassan, Ahmad Y</a>, <a rel="nofollow" class="external text" href="http://www.history-science-technology.com/Articles/articles%2071.htm">Transfer Of Islamic Technology To The West, Part II: Transmission Of Islamic Engineering</a>, <i>History of Science and Technology in Islam</i></span> </li> <li id="cite_note-46"><span class="mw-cite-backlink"><b><a href="#cite_ref-46">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFXu2021" class="citation book cs1">Xu, Z. 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Vol. 3. pp. 413–426. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2F978-981-15-7847-2_11">10.1007/978-981-15-7847-2_11</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-981-15-7846-5" title="Special:BookSources/978-981-15-7846-5"><bdi>978-981-15-7846-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Spread+of+Traditional+Chinese+Mathematics+in+the+Sinosphere+and+Its+Influence&rft.btitle=The+High+Tide+of+Science+and+Technology+Development+in+China%3A+History+of+Science+and+Technology+in+China&rft.pages=413-426&rft.date=2021&rft_id=info%3Adoi%2F10.1007%2F978-981-15-7847-2_11&rft.isbn=978-981-15-7846-5&rft.aulast=Xu&rft.aufirst=Z.&rft_id=https%3A%2F%2Flink.springer.com%2Fcontent%2Fpdf%2F10.1007%2F978-981-15-7847-2_11.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-47">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKoetsierceccarelli2012" class="citation book cs1">Koetsier, Teun; ceccarelli, marco (5 April 2012). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=-x9NHOLSnNUC&pg=PA90"><i>Explorations in the History of Machines and Mechanisms: Proceedings of HMM2012</i></a>. Springer Science & Business Media. p. 90. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9789400741324" title="Special:BookSources/9789400741324"><bdi>9789400741324</bdi></a><span class="reference-accessdate">. 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KSCPP. Archived from <a rel="nofollow" class="external text" href="http://www.kscpp.net/LinkClick.aspx?fileticket=lILBCCXDCSk%3d&tabid=144&mid=528">the original</a> on 2017-03-27<span class="reference-accessdate">. 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Retrieved <span class="nowrap">27 March</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Bridge+between+Conceptual+Frameworks%3A+Sciences%2C+Society+and+Technology+Studies&rft.pages=364&rft.pub=Springer&rft.date=2015-06-30&rft.isbn=9789401796453&rft.aulast=Pisano&rft.aufirst=Raffaele&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DeUUPCgAAQBAJ%26pg%3DPA364&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></span> </li> <li id="cite_note-52"><span class="mw-cite-backlink"><b><a href="#cite_ref-52">^</a></b></span> <span class="reference-text"><a href="#CITEREFGoodenowOrrRoss2007">Goodenow, Orr & Ross (2007)</a>, p. 6</span> </li> <li id="cite_note-53"><span class="mw-cite-backlink"><b><a href="#cite_ref-53">^</a></b></span> <span class="reference-text"><a href="/wiki/CRC_Handbook_of_Chemistry_and_Physics" title="CRC Handbook of Chemistry and Physics">CRC Handbook of Chemistry and Physics</a>, page F-36</span> </li> </ol></div> <div class="mw-heading mw-heading3"><h3 id="Sources_used">Sources used</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=16" title="Edit section: Sources used"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFal-HassanHill1986" class="citation book cs1"><a href="/wiki/Ahmad_Y_Hassan" class="mw-redirect" title="Ahmad Y Hassan">al-Hassan, Ahmad Y.</a>; <a href="/wiki/Donald_Routledge_Hill" class="mw-redirect" title="Donald Routledge Hill">Hill, Donald R.</a> (1986). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/islamictechnolog0000hasa"><i>Islamic Technology: An Illustrated History</i></a></span>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-26333-6" title="Special:BookSources/0-521-26333-6"><bdi>0-521-26333-6</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/13332728">13332728</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Islamic+Technology%3A+An+Illustrated+History&rft.pub=Cambridge+University+Press&rft.date=1986&rft_id=info%3Aoclcnum%2F13332728&rft.isbn=0-521-26333-6&rft.aulast=al-Hassan&rft.aufirst=Ahmad+Y.&rft.au=Hill%2C+Donald+R.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fislamictechnolog0000hasa&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCotterellKamminga1990" class="citation book cs1">Cotterell, Brian; Kamminga, Johan (1990). <i>Mechanics of pre-industrial technology: An introduction to the mechanics of ancient and traditional material culture</i>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-42871-8" title="Special:BookSources/0-521-42871-8"><bdi>0-521-42871-8</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/18520966">18520966</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Mechanics+of+pre-industrial+technology%3A+An+introduction+to+the+mechanics+of+ancient+and+traditional+material+culture&rft.pub=Cambridge+University+Press&rft.date=1990&rft_id=info%3Aoclcnum%2F18520966&rft.isbn=0-521-42871-8&rft.aulast=Cotterell&rft.aufirst=Brian&rft.au=Kamminga%2C+Johan&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCowan1958" class="citation book cs1">Cowan, Harrison J. (1958). <i>Time and Its Measurement: From the stone age to the nuclear age</i>. Ohio: The World Publishing Company. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1958tmfs.book.....C">1958tmfs.book.....C</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Time+and+Its+Measurement%3A+From+the+stone+age+to+the+nuclear+age&rft.place=Ohio&rft.pub=The+World+Publishing+Company&rft.date=1958&rft_id=info%3Abibcode%2F1958tmfs.book.....C&rft.aulast=Cowan&rft.aufirst=Harrison+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGoodenowOrrRoss2007" class="citation cs2">Goodenow, Jennifer; Orr, Richard; Ross, David (2007), <a rel="nofollow" class="external text" href="http://www.nawcc-index.net/Articles/Goodenow-WaterClocks.pdf"><i>Mathematical Models of Water Clocks</i></a> <span class="cs1-format">(PDF)</span>, Rochester Institute of Technology</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Mathematical+Models+of+Water+Clocks&rft.pub=Rochester+Institute+of+Technology&rft.date=2007&rft.aulast=Goodenow&rft.aufirst=Jennifer&rft.au=Orr%2C+Richard&rft.au=Ross%2C+David&rft_id=http%3A%2F%2Fwww.nawcc-index.net%2FArticles%2FGoodenow-WaterClocks.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHill1981" class="citation book cs1"><a href="/wiki/Donald_Routledge_Hill" class="mw-redirect" title="Donald Routledge Hill">Hill, D.R.</a> (1981). <i>Arabic Water–Clocks</i>. Syria: University of Aleppo.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Arabic+Water%E2%80%93Clocks&rft.place=Syria&rft.pub=University+of+Aleppo&rft.date=1981&rft.aulast=Hill&rft.aufirst=D.R.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLewis2000" class="citation book cs1">Lewis, Michael (2000). "Theoretical Hydraulics, Automata, and Water Clocks". In <a href="/wiki/%C3%96rjan_Wikander" title="Örjan Wikander">Wikander, Örjan</a> (ed.). <i>Handbook of Ancient Water Technology</i>. Technology and Change in History. Vol. 2. Leiden. pp. 343–369 (356f.). <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/90-04-11123-9" title="Special:BookSources/90-04-11123-9"><bdi>90-04-11123-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Theoretical+Hydraulics%2C+Automata%2C+and+Water+Clocks&rft.btitle=Handbook+of+Ancient+Water+Technology&rft.place=Leiden&rft.series=Technology+and+Change+in+History&rft.pages=343-369+%28356f.%29&rft.date=2000&rft.isbn=90-04-11123-9&rft.aulast=Lewis&rft.aufirst=Michael&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_book" title="Template:Cite book">cite book</a>}}</code>: CS1 maint: location missing publisher (<a href="/wiki/Category:CS1_maint:_location_missing_publisher" title="Category:CS1 maint: location missing publisher">link</a>)</span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeedham1986" class="citation book cs1"><a href="/wiki/Joseph_Needham" title="Joseph Needham">Needham, Joseph</a> (1986). <i>Science & Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering</i>. Taipei: Caves Books.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Science+%26+Civilization+in+China%3A+Volume+4%2C+Physics+and+Physical+Technology%2C+Part+2%2C+Mechanical+Engineering&rft.place=Taipei&rft.pub=Caves+Books&rft.date=1986&rft.aulast=Needham&rft.aufirst=Joseph&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeedham1995" class="citation book cs1"><a href="/wiki/Joseph_Needham" title="Joseph Needham">Needham, Joseph</a> (1995). <i>Science & Civilisation in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth</i>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-05801-5" title="Special:BookSources/0-521-05801-5"><bdi>0-521-05801-5</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/153247126">153247126</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Science+%26+Civilisation+in+China%3A+Volume+3%2C+Mathematics+and+the+Sciences+of+the+Heavens+and+the+Earth&rft.pub=Cambridge+University+Press&rft.date=1995&rft_id=info%3Aoclcnum%2F153247126&rft.isbn=0-521-05801-5&rft.aulast=Needham&rft.aufirst=Joseph&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeedham2000" class="citation book cs1"><a href="/wiki/Joseph_Needham" title="Joseph Needham">Needham, Joseph</a> (2000). <i>Science & Civilisation in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering</i>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-05803-1" title="Special:BookSources/0-521-05803-1"><bdi>0-521-05803-1</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/153247141">153247141</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Science+%26+Civilisation+in+China%3A+Volume+4%2C+Physics+and+Physical+Technology%2C+Part+2%2C+Mechanical+Engineering&rft.pub=Cambridge+University+Press&rft.date=2000&rft_id=info%3Aoclcnum%2F153247141&rft.isbn=0-521-05803-1&rft.aulast=Needham&rft.aufirst=Joseph&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeugebauer1947" class="citation journal cs1"><a href="/wiki/Otto_E._Neugebauer" title="Otto E. Neugebauer">Neugebauer, Otto</a> (1947). "Studies in Ancient Astronomy. VIII. The Water Clock in Babylonian Astronomy". <i>Isis</i>. <b>37</b> (1/2): 37–43. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F347965">10.1086/347965</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/20247883">20247883</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:120229480">120229480</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Isis&rft.atitle=Studies+in+Ancient+Astronomy.+VIII.+The+Water+Clock+in+Babylonian+Astronomy&rft.volume=37&rft.issue=1%2F2&rft.pages=37-43&rft.date=1947&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A120229480%23id-name%3DS2CID&rft_id=info%3Apmid%2F20247883&rft_id=info%3Adoi%2F10.1086%2F347965&rft.aulast=Neugebauer&rft.aufirst=Otto&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span> (Reprinted in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNeugebauer1983" class="citation book cs1">Neugebauer, Otto (1983). <i>Astronomy and History: Selected Essays</i>. pp. 239–245.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Astronomy+and+History%3A+Selected+Essays&rft.pages=239-245&rft.date=1983&rft.aulast=Neugebauer&rft.aufirst=Otto&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span>)</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTemple1986" class="citation book cs1">Temple, Robert (1986). <span class="id-lock-limited" title="Free access subject to limited trial, subscription normally required"><a rel="nofollow" class="external text" href="https://archive.org/details/geniusofchina3000temp/page/55"><i>The Genius of China: 3000 years of science, discovery and invention</i></a></span>. New York: Simon and Schuster. p. 55. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780671620288" title="Special:BookSources/9780671620288"><bdi>9780671620288</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Genius+of+China%3A+3000+years+of+science%2C+discovery+and+invention&rft.place=New+York&rft.pages=55&rft.pub=Simon+and+Schuster&rft.date=1986&rft.isbn=9780671620288&rft.aulast=Temple&rft.aufirst=Robert&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fgeniusofchina3000temp%2Fpage%2F55&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTurner1984" class="citation book cs1 cs1-prop-long-vol">Turner, Anthony J. (1984). <i>The Time Museum</i>. Vol. I: <i>Time Measuring Instruments</i>, Part 3: <i>Water-clocks</i>, <i>Sand-glasses</i>, <i>Fire-clocks</i>. Rockford, IL: The Museum. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-912947-01-2" title="Special:BookSources/0-912947-01-2"><bdi>0-912947-01-2</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/159866762">159866762</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Time+Museum&rft.place=Rockford%2C+IL&rft.pub=The+Museum&rft.date=1984&rft_id=info%3Aoclcnum%2F159866762&rft.isbn=0-912947-01-2&rft.aulast=Turner&rft.aufirst=Anthony+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="Bibliography">Bibliography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=17" title="Edit section: Bibliography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Bibliography_of_water_clocks" title="Bibliography of water clocks">Bibliography of water clocks</a></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Water_clock&action=edit&section=18" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/60px-Wiktionary-logo-en-v2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/80px-Wiktionary-logo-en-v2.svg.png 2x" data-file-width="512" data-file-height="512" /></span></span></div> <div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/clepsydra" class="extiw" title="wiktionary:clepsydra"> clepsydra</a></b></i> in Wiktionary, the free dictionary.</div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735"><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Water_clocks" class="extiw" title="commons:Category:Water clocks">Water clocks</a></span>.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://www.europa-center-berlin.de/en/the-sights/the-clock-of-flowing-time.html">The Clock of Flowing Time in Berlin</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190118081232/http://www.europa-center-berlin.de/en/the-sights/the-clock-of-flowing-time.html">Archived</a> 2019-01-18 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-through-time/walk-through-time-early-clocks">NIST: A Walk Through Time – Early Clocks</a></li> <li><a rel="nofollow" class="external text" href="http://www.marcdatabase.com/~lemur/dm-gitton.html#iw-time-flow-clocks">Bernard Gitton's Time-Flow Clocks</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110809073852/http://www.marcdatabase.com/~lemur/dm-gitton.html#iw-time-flow-clocks">Archived</a> 2011-08-09 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://japan.mfa.gov.ir/en/newsview/536035">Qanat is cultural, social and scientific heritage in Iran</a></li> <li><a rel="nofollow" class="external text" href="http://www.eternalegypt.org/EternalEgyptWebsiteWeb/HomeServlet?ee_website_action_key=action.display.element&story_id=19&module_id=5&language_id=1&element_id=60513">Egypt's Water Clock</a></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation encyclopaedia cs1"><span class="cs1-ws-icon" title="s:The Encyclopedia Americana (1920)/Clepsydra"><a class="external text" href="https://en.wikisource.org/wiki/The_Encyclopedia_Americana_(1920)/Clepsydra">"Clepsydra" </a></span>. <i><a href="/wiki/Encyclopedia_Americana" title="Encyclopedia Americana">Encyclopedia Americana</a></i>. 1920.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Clepsydra&rft.btitle=Encyclopedia+Americana&rft.date=1920&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><a rel="nofollow" class="external text" href="https://www.perseus.tufts.edu/GreekScience/Students/Jesse/CLOCK1A.html">A Brief History of Clocks: From Thales to Ptolemy</a></li> <li><a rel="nofollow" class="external text" href="http://www.childrensmuseum.org/waterclock">The Indianapolis Children's Museum Water Clock</a></li> <li><a rel="nofollow" class="external text" href="http://www.landmarkclocks.com/page14.html">Nanaimo, BC Water Clock</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070811001650/http://www.landmarkclocks.com/page14.html">Archived</a> 2007-08-11 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://www.history-of-physics.com/2017/08/ancient-greece-water-clock-clepsydra-of_14.html">Animation: Ctesibius Water Clock</a></li> <li><a rel="nofollow" class="external text" href="http://www.antique-horology.org/_editorial/clepsydra/">Rees's Universal Dictionary article on Clepsydra, 1819</a></li> <li><a rel="nofollow" class="external text" href="http://www.royalgorgebridge.com/WaterClock.aspx">The Royal Gorge Bridge Water Clock</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070501165809/http://www.royalgorgebridge.com/WaterClock.aspx">Archived</a> 2007-05-01 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation encyclopaedia cs1"><span class="cs1-ws-icon" title="s:The New International Encyclopædia/Clepsydra"><a class="external text" href="https://en.wikisource.org/wiki/The_New_International_Encyclop%C3%A6dia/Clepsydra">"Clepsydra" </a></span>. <i><a href="/wiki/New_International_Encyclopedia" class="mw-redirect" title="New International Encyclopedia">New International Encyclopedia</a></i>. 1905.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Clepsydra&rft.btitle=New+International+Encyclopedia&rft.date=1905&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWater+clock" class="Z3988"></span></li> <li><a rel="nofollow" class="external text" href="http://www.muslimheritage.com/article/mechanical-water-clock-ibn-al-haytham">The Mechanical Water Clock Of Ibn Al-Haytham</a></li> <li><a rel="nofollow" class="external text" href="https://maghzrayaneh.ir/services-computer">computer servies on site</a> on clocks</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline 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navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Time_topics" title="Template:Time topics"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Time_topics" title="Template talk:Time topics"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Time_topics" title="Special:EditPage/Template:Time topics"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Time" style="font-size:114%;margin:0 4em"><a href="/wiki/Time" title="Time">Time</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Key concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Past" title="Past">Past</a></li> <li><a href="/wiki/Present" title="Present">Present</a></li> <li><a href="/wiki/Future" title="Future">Future</a></li> <li><a href="/wiki/Eternity" title="Eternity">Eternity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Horology" class="mw-redirect" title="Horology">Measurement</a><br />and <a href="/wiki/Time_standard" title="Time standard">standards</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Chronometry" title="Chronometry">Chronometry</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a></li> <li><a href="/wiki/Universal_Time" title="Universal Time">UT</a></li> <li><a href="/wiki/International_Atomic_Time" title="International Atomic Time">TAI</a></li> <li><a href="/wiki/Unit_of_time" title="Unit of time">Unit of time</a></li> <li><a href="/wiki/Orders_of_magnitude_(time)" title="Orders of magnitude (time)">Orders of magnitude (time)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/System_of_measurement" class="mw-redirect" title="System of measurement">Measurement<br />systems</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Italian_six-hour_clock" title="Italian six-hour clock">Italian six-hour clock</a></li> <li><a href="/wiki/Thai_six-hour_clock" title="Thai six-hour clock">Thai six-hour clock</a></li> <li><a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a href="/wiki/24-hour_clock" title="24-hour clock">24-hour clock</a></li> <li><a href="/wiki/Relative_hour" title="Relative hour">Relative hour</a></li> <li><a href="/wiki/Daylight_saving_time" title="Daylight saving time">Daylight saving time</a></li> <li><a href="/wiki/Traditional_Chinese_timekeeping" title="Traditional Chinese timekeeping">Chinese</a></li> <li><a href="/wiki/Decimal_time" title="Decimal time">Decimal</a></li> <li><a href="/wiki/Hexadecimal_time" title="Hexadecimal time">Hexadecimal</a></li> <li><a href="/wiki/Hindu_units_of_time" title="Hindu units of time">Hindu</a></li> <li><a href="/wiki/Metric_time" title="Metric time">Metric</a></li> <li><a href="/wiki/Roman_timekeeping" title="Roman timekeeping">Roman</a></li> <li><a href="/wiki/Sidereal_time" title="Sidereal time">Sidereal</a></li> <li><a href="/wiki/Solar_time" title="Solar time">Solar</a></li> <li><a href="/wiki/Time_zone" title="Time zone">Time zone</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Calendar" title="Calendar">Calendars</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Calendar#Systems" title="Calendar">Main types</a> <ul><li><a href="/wiki/Solar_calendar" title="Solar calendar">Solar</a></li> <li><a href="/wiki/Lunar_calendar" title="Lunar calendar">Lunar</a></li> <li><a href="/wiki/Lunisolar_calendar" title="Lunisolar calendar">Lunisolar</a></li></ul></li> <li><a href="/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a></li> <li><a href="/wiki/Julian_calendar" title="Julian calendar">Julian</a></li> <li><a href="/wiki/Hebrew_calendar" title="Hebrew calendar">Hebrew</a></li> <li><a href="/wiki/Islamic_calendar" title="Islamic calendar">Islamic</a></li> <li><a href="/wiki/Solar_Hijri_calendar" title="Solar Hijri calendar">Solar Hijri</a></li> <li><a href="/wiki/Chinese_calendar" title="Chinese calendar">Chinese</a></li> <li><a href="/wiki/Hindu_calendar" title="Hindu calendar">Hindu Panchang</a></li> <li><a href="/wiki/Maya_calendar" title="Maya calendar">Maya</a></li> <li><i><a href="/wiki/List_of_calendars" title="List of calendars">List</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Clock" title="Clock">Clocks</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Clock#Types" title="Clock">Main types</a> <ul><li><a href="/wiki/Astronomical_clock" title="Astronomical clock">astronomical</a> <ul><li><a href="/wiki/Astrarium" title="Astrarium">astrarium</a></li></ul></li> <li><a href="/wiki/Atomic_clock" title="Atomic clock">atomic</a> <ul><li><a href="/wiki/Quantum_clock" class="mw-redirect" title="Quantum clock">quantum</a></li></ul></li> <li><a href="/wiki/Hourglass" title="Hourglass">hourglass</a></li> <li><a href="/wiki/Marine_chronometer" title="Marine chronometer">marine</a></li> <li><a href="/wiki/Sundial" title="Sundial">sundial</a></li> <li><a href="/wiki/Watch" title="Watch">watch</a> <ul><li><a href="/wiki/Mechanical_watch" title="Mechanical watch">mechanical</a></li> <li><a href="/wiki/Stopwatch" title="Stopwatch">stopwatch</a></li></ul></li> <li><a class="mw-selflink selflink">water-based</a></li></ul></li> <li><a href="/wiki/Cuckoo_clock" title="Cuckoo clock">Cuckoo clock</a></li> <li><a href="/wiki/Digital_clock" title="Digital clock">Digital clock</a></li> <li><a href="/wiki/Grandfather_clock" title="Grandfather clock">Grandfather clock</a></li> <li><i><a href="/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History</a></i> <ul><li><i><a href="/wiki/Timeline_of_time_measurement_inventions" title="Timeline of time measurement inventions">Timeline</a></i></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><div class="hlist"><ul><li><a href="/wiki/Chronology" title="Chronology">Chronology</a></li><li><a href="/wiki/History" title="History">History</a></li></ul></div></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astronomical_chronology" title="Astronomical chronology">Astronomical chronology</a></li> <li><a href="/wiki/Big_History" title="Big History">Big History</a></li> <li><a href="/wiki/Calendar_era" title="Calendar era">Calendar era</a></li> <li><a href="/wiki/Deep_time" title="Deep time">Deep time</a></li> <li><a href="/wiki/Periodization" title="Periodization">Periodization</a></li> <li><a href="/wiki/Regnal_year" title="Regnal year">Regnal year</a></li> <li><a href="/wiki/Timeline" title="Timeline">Timeline</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Philosophy_of_space_and_time" title="Philosophy of space and time">Philosophy of time</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/A_series_and_B_series" title="A series and B series">A series and B series</a></li> <li><a href="/wiki/B-theory_of_time" title="B-theory of time">B-theory of time</a></li> <li><a href="/wiki/Chronocentrism" title="Chronocentrism">Chronocentrism</a></li> <li><a href="/wiki/Duration_(philosophy)" title="Duration (philosophy)">Duration</a></li> <li><a href="/wiki/Endurantism" title="Endurantism">Endurantism</a></li> <li><a href="/wiki/Eternal_return" title="Eternal return">Eternal return</a></li> <li><a href="/wiki/Eternalism_(philosophy_of_time)" title="Eternalism (philosophy of time)">Eternalism</a></li> <li><a href="/wiki/Event_(philosophy)" title="Event (philosophy)">Event</a></li> <li><a href="/wiki/Perdurantism" title="Perdurantism">Perdurantism</a></li> <li><a href="/wiki/Philosophical_presentism" title="Philosophical presentism">Presentism</a></li> <li><a href="/wiki/Temporal_finitism" title="Temporal finitism">Temporal finitism</a></li> <li><a href="/wiki/Temporal_parts" title="Temporal parts">Temporal parts</a></li> <li><i><a href="/wiki/The_Unreality_of_Time" title="The Unreality of Time">The Unreality of Time</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><div class="hlist"><ul><li><a href="/wiki/Category:Time_in_religion" title="Category:Time in religion">Religion</a></li><li><a href="/wiki/Template:Time_in_religion_and_mythology" title="Template:Time in religion and mythology">Mythology</a></li></ul></div></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ages_of_Man" title="Ages of Man">Ages of Man</a></li> <li><a href="/wiki/Destiny" title="Destiny">Destiny</a></li> <li><a href="/wiki/Immortality" title="Immortality">Immortality</a></li> <li><a href="/wiki/The_Dreaming" title="The Dreaming">Dreamtime</a></li> <li><a href="/wiki/K%C4%81la" title="Kāla">Kāla</a></li> <li><a href="/wiki/Time_and_fate_deities" title="Time and fate deities">Time and fate deities</a> <ul><li><a href="/wiki/Father_Time" title="Father Time">Father Time</a></li></ul></li> <li><a href="/wiki/Wheel_of_time" title="Wheel of time">Wheel of time</a> <ul><li><a href="/wiki/Kalachakra" title="Kalachakra">Kalachakra</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Time_perception" title="Time perception">Human experience</a><br />and <a href="/wiki/Time-use_research" title="Time-use research">use of time</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronemics" title="Chronemics">Chronemics</a></li> <li><a href="/wiki/Generation_time" title="Generation time">Generation time</a></li> <li><a href="/wiki/Mental_chronometry" title="Mental chronometry">Mental chronometry</a></li> <li><a href="/wiki/Duration_(music)" title="Duration (music)">Music</a> <ul><li><a href="/wiki/Tempo" title="Tempo">tempo</a></li> <li><a href="/wiki/Time_signature" title="Time signature">time signature</a></li></ul></li> <li><a href="/wiki/Rosy_retrospection" title="Rosy retrospection">Rosy retrospection</a></li> <li><a href="/wiki/Tense%E2%80%93aspect%E2%80%93mood" title="Tense–aspect–mood">Tense–aspect–mood</a></li> <li><a href="/wiki/Time_management" title="Time management">Time management</a></li> <li><a href="/wiki/Yesterday_(time)" title="Yesterday (time)">Yesterday</a> – <a href="/wiki/Present" title="Present">Today</a> – <a href="/wiki/Tomorrow_(time)" title="Tomorrow (time)">Tomorrow</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Time in <a href="/wiki/Science" title="Science">science</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Geology" title="Geology">Geology</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Geologic_time_scale" title="Geologic time scale">Geological time</a> <ul><li><a href="/wiki/Age_(geology)" class="mw-redirect" title="Age (geology)">age</a></li> <li><a href="/wiki/Chronozone" title="Chronozone">chron</a></li> <li><a href="/wiki/Eon_(geology)" class="mw-redirect" title="Eon (geology)">eon</a></li> <li><a href="/wiki/Epoch_(geology)" class="mw-redirect" title="Epoch (geology)">epoch</a></li> <li><a href="/wiki/Era_(geology)" class="mw-redirect" title="Era (geology)">era</a></li> <li><a href="/wiki/Geological_period" class="mw-redirect" title="Geological period">period</a></li></ul></li> <li><a href="/wiki/Geochronology" title="Geochronology">Geochronology</a></li> <li><a href="/wiki/Geological_history_of_Earth" title="Geological history of Earth">Geological history of Earth</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Time_in_physics" title="Time in physics">Physics</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Absolute_space_and_time" title="Absolute space and time">Absolute space and time</a></li> <li><a href="/wiki/Arrow_of_time" title="Arrow of time">Arrow of time</a></li> <li><a href="/wiki/Chronon" title="Chronon">Chronon</a></li> <li><a href="/wiki/Coordinate_time" title="Coordinate time">Coordinate time</a></li> <li><a href="/wiki/Instant" title="Instant">Instant</a></li> <li><a href="/wiki/Proper_time" title="Proper time">Proper time</a></li> <li><a href="/wiki/Spacetime" title="Spacetime">Spacetime</a></li> <li><a href="/wiki/Theory_of_relativity" title="Theory of relativity">Theory of relativity</a></li> <li><a href="/wiki/Time_domain" title="Time domain">Time domain</a></li> <li><a href="/wiki/Time_translation_symmetry" class="mw-redirect" title="Time translation symmetry">Time translation symmetry</a></li> <li><a href="/wiki/T-symmetry" title="T-symmetry">Time reversal symmetry</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;">Other fields</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronological_dating" title="Chronological dating">Chronological dating</a></li> <li><a href="/wiki/Chronobiology" title="Chronobiology">Chronobiology</a> <ul><li><a href="/wiki/Circadian_rhythm" title="Circadian rhythm">Circadian rhythms</a></li></ul></li> <li><a href="/wiki/Chemical_clock" title="Chemical clock">Clock reaction</a></li> <li><a href="/wiki/Glottochronology" title="Glottochronology">Glottochronology</a></li> <li><a href="/wiki/Time_geography" title="Time geography">Time geography</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Leap_year" title="Leap year">Leap year</a></li> <li><a href="/wiki/Memory" title="Memory">Memory</a></li> <li><a href="/wiki/Moment_(unit)" title="Moment (unit)">Moment</a></li> <li><a href="/wiki/Space" title="Space">Space</a></li> <li><a href="/wiki/System_time" title="System time">System time</a></li> <li><i><a href="/wiki/Tempus_fugit" title="Tempus fugit">Tempus fugit</a></i></li> <li><a href="/wiki/Time_capsule" title="Time capsule">Time capsule</a></li> <li><a href="/wiki/Time_immemorial" title="Time immemorial">Time immemorial</a></li> <li><a href="/wiki/Time_travel" title="Time travel">Time travel</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Time" title="Category:Time">Category</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Commons page"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span> <a href="https://commons.wikimedia.org/wiki/Category:Time" class="extiw" title="commons:Category:Time">Commons</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Time_measurement_and_standards" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Time_measurement_and_standards" title="Template:Time measurement and standards"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Time_measurement_and_standards" title="Template talk:Time measurement and standards"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Time_measurement_and_standards" title="Special:EditPage/Template:Time measurement and standards"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Time_measurement_and_standards" style="font-size:114%;margin:0 4em"><a href="/wiki/Time" title="Time">Time measurement</a> and <a href="/wiki/Time_standard" title="Time standard">standards</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="3"><div> <ul><li><a href="/wiki/Chronometry" title="Chronometry">Chronometry</a></li> <li><a href="/wiki/Orders_of_magnitude_(time)" title="Orders of magnitude (time)">Orders of magnitude</a></li> <li><a href="/wiki/Time_metrology" class="mw-redirect" title="Time metrology">Metrology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">International standards</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">Coordinated Universal Time</a> <ul><li><a href="/wiki/UTC_offset" title="UTC offset">offset</a></li></ul></li> <li><a href="/wiki/Universal_Time" title="Universal Time">UT</a></li> <li><a href="/wiki/%CE%94T_(timekeeping)" title="ΔT (timekeeping)">ΔT</a></li> <li><a href="/wiki/DUT1" title="DUT1">DUT1</a></li> <li><a href="/wiki/International_Earth_Rotation_and_Reference_Systems_Service" title="International Earth Rotation and Reference Systems Service">International Earth Rotation and Reference Systems Service</a></li> <li><a href="/wiki/ISO_31-1" title="ISO 31-1">ISO 31-1</a></li> <li><a href="/wiki/ISO_8601" title="ISO 8601">ISO 8601</a></li> <li><a href="/wiki/International_Atomic_Time" title="International Atomic Time">International Atomic Time</a></li> <li><a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a href="/wiki/24-hour_clock" title="24-hour clock">24-hour clock</a></li> <li><a href="/wiki/Barycentric_Coordinate_Time" title="Barycentric Coordinate Time">Barycentric Coordinate Time</a></li> <li><a href="/wiki/Barycentric_Dynamical_Time" title="Barycentric Dynamical Time">Barycentric Dynamical Time</a></li> <li><a href="/wiki/Civil_time" title="Civil time">Civil time</a></li> <li><a href="/wiki/Daylight_saving_time" title="Daylight saving time">Daylight saving time</a></li> <li><a href="/wiki/Geocentric_Coordinate_Time" title="Geocentric Coordinate Time">Geocentric Coordinate Time</a></li> <li><a href="/wiki/International_Date_Line" title="International Date Line">International Date Line</a></li> <li><a href="/wiki/IERS_Reference_Meridian" title="IERS Reference Meridian">IERS Reference Meridian</a></li> <li><a href="/wiki/Leap_second" title="Leap second">Leap second</a></li> <li><a href="/wiki/Solar_time" title="Solar time">Solar time</a></li> <li><a href="/wiki/Terrestrial_Time" title="Terrestrial Time">Terrestrial Time</a></li> <li><a href="/wiki/Time_zone" title="Time zone">Time zone</a></li> <li><a href="/wiki/180th_meridian" title="180th meridian">180th meridian</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="9" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/Hourglass" title="Hourglass"><img alt="template illustration" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Marine_sandglass_MMM.jpg/75px-Marine_sandglass_MMM.jpg" decoding="async" width="75" height="175" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Marine_sandglass_MMM.jpg/113px-Marine_sandglass_MMM.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/70/Marine_sandglass_MMM.jpg/150px-Marine_sandglass_MMM.jpg 2x" data-file-width="1637" data-file-height="3819" /></a></span><br /><span typeof="mw:File"><a href="/wiki/Time_zone" title="Time zone"><img alt="template illustration" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png/75px-Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png" decoding="async" width="75" height="152" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png/113px-Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png/150px-Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png 2x" data-file-width="496" data-file-height="1007" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Obsolete standards</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ephemeris_time" title="Ephemeris time">Ephemeris time</a></li> <li><a href="/wiki/Greenwich_Mean_Time" title="Greenwich Mean Time">Greenwich Mean Time</a></li> <li><a href="/wiki/Prime_meridian" title="Prime meridian">Prime meridian</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Time_in_physics" title="Time in physics">Time in physics</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Absolute_space_and_time" title="Absolute space and time">Absolute space and time</a></li> <li><a href="/wiki/Spacetime" title="Spacetime">Spacetime</a></li> <li><a href="/wiki/Chronon" title="Chronon">Chronon</a></li> <li><a href="/wiki/Continuous_signal" class="mw-redirect" title="Continuous signal">Continuous signal</a></li> <li><a href="/wiki/Coordinate_time" title="Coordinate time">Coordinate time</a></li> <li><a href="/wiki/Cosmological_decade" title="Cosmological decade">Cosmological decade</a></li> <li><a href="/wiki/Discrete_time_and_continuous_time" title="Discrete time and continuous time">Discrete time and continuous time</a></li> <li><a href="/wiki/Proper_time" title="Proper time">Proper time</a></li> <li><a href="/wiki/Theory_of_relativity" title="Theory of relativity">Theory of relativity</a></li> <li><a href="/wiki/Time_dilation" title="Time dilation">Time dilation</a></li> <li><a href="/wiki/Gravitational_time_dilation" title="Gravitational time dilation">Gravitational time dilation</a></li> <li><a href="/wiki/Time_domain" title="Time domain">Time domain</a></li> <li><a href="/wiki/Time-translation_symmetry" title="Time-translation symmetry">Time-translation symmetry</a></li> <li><a href="/wiki/T-symmetry" title="T-symmetry">T-symmetry</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Horology" class="mw-redirect" title="Horology">Horology</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Clock" title="Clock">Clock</a></li> <li><a href="/wiki/Astrarium" title="Astrarium">Astrarium</a></li> <li><a href="/wiki/Atomic_clock" title="Atomic clock">Atomic clock</a></li> <li><a href="/wiki/Complication_(horology)" title="Complication (horology)">Complication</a></li> <li><a href="/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History of timekeeping devices</a></li> <li><a href="/wiki/Hourglass" title="Hourglass">Hourglass</a></li> <li><a href="/wiki/Marine_chronometer" title="Marine chronometer">Marine chronometer</a></li> <li><a href="/wiki/Marine_sandglass" title="Marine sandglass">Marine sandglass</a></li> <li><a href="/wiki/Radio_clock" title="Radio clock">Radio clock</a></li> <li><a href="/wiki/Watch" title="Watch">Watch</a> <ul><li><a href="/wiki/Stopwatch" title="Stopwatch">stopwatch</a></li></ul></li> <li><a class="mw-selflink selflink">Water clock</a></li> <li><a href="/wiki/Sundial" title="Sundial">Sundial</a></li> <li><a href="/wiki/Dialing_scales" title="Dialing scales">Dialing scales</a></li> <li><a href="/wiki/Equation_of_time" title="Equation of time">Equation of time</a></li> <li><a href="/wiki/History_of_sundials" title="History of sundials">History of sundials</a></li> <li><a href="/wiki/Schema_for_horizontal_dials" title="Schema for horizontal dials">Sundial markup schema</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Calendar" title="Calendar">Calendar</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a></li> <li><a href="/wiki/Hebrew_calendar" title="Hebrew calendar">Hebrew</a></li> <li><a href="/wiki/Hindu_calendar" title="Hindu calendar">Hindu</a></li> <li><a href="/wiki/Holocene_calendar" title="Holocene calendar">Holocene</a></li> <li><a href="/wiki/Islamic_calendar" title="Islamic calendar">Islamic</a> (lunar Hijri)</li> <li><a href="/wiki/Julian_calendar" title="Julian calendar">Julian</a></li> <li><a href="/wiki/Solar_Hijri_calendar" title="Solar Hijri calendar">Solar Hijri</a></li> <li><a href="/wiki/Astronomical_year_numbering" title="Astronomical year numbering">Astronomical</a></li> <li><a href="/wiki/Dominical_letter" title="Dominical letter">Dominical letter</a></li> <li><a href="/wiki/Epact" title="Epact">Epact</a></li> <li><a href="/wiki/Equinox" title="Equinox">Equinox</a></li> <li><a href="/wiki/Intercalation_(timekeeping)" title="Intercalation (timekeeping)">Intercalation</a></li> <li><a href="/wiki/Julian_day" title="Julian day">Julian day</a></li> <li><a href="/wiki/Leap_year" title="Leap year">Leap year</a></li> <li><a href="/wiki/Lunar_calendar" title="Lunar calendar">Lunar</a></li> <li><a href="/wiki/Lunisolar_calendar" title="Lunisolar calendar">Lunisolar</a></li> <li><a href="/wiki/Solar_calendar" title="Solar calendar">Solar</a></li> <li><a href="/wiki/Solstice" title="Solstice">Solstice</a></li> <li><a href="/wiki/Tropical_year" title="Tropical year">Tropical year</a></li> <li><a href="/wiki/Determination_of_the_day_of_the_week" title="Determination of the day of the week">Weekday determination</a></li> <li><a href="/wiki/Names_of_the_days_of_the_week" title="Names of the days of the week">Weekday names</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Archaeology and geology</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronological_dating" title="Chronological dating">Chronological dating</a></li> <li><a href="/wiki/Geologic_time_scale" title="Geologic time scale">Geologic time scale</a></li> <li><a href="/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">International Commission on Stratigraphy</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Astronomical_chronology" title="Astronomical chronology">Astronomical chronology</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Galactic_year" title="Galactic year">Galactic year</a></li> <li><a href="/wiki/Nuclear_timescale" title="Nuclear timescale">Nuclear timescale</a></li> <li><a href="/wiki/Precession" title="Precession">Precession</a></li> <li><a href="/wiki/Sidereal_time" title="Sidereal time">Sidereal time</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other <a href="/wiki/Unit_of_time" title="Unit of time">units of time</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Instant" title="Instant">Instant</a></li> <li><a href="/wiki/Flick_(time)" title="Flick (time)">Flick</a></li> <li><a href="/wiki/Shake_(unit)" title="Shake (unit)">Shake</a></li> <li><a href="/wiki/Jiffy_(time)" title="Jiffy (time)">Jiffy</a></li> <li><a href="/wiki/Second" title="Second">Second</a></li> <li><a href="/wiki/Minute" title="Minute">Minute</a></li> <li><a href="/wiki/Moment_(unit)" title="Moment (unit)">Moment</a></li> <li><a href="/wiki/Hour" title="Hour">Hour</a></li> <li><a href="/wiki/Day" title="Day">Day</a></li> <li><a href="/wiki/Week" title="Week">Week</a></li> <li><a href="/wiki/Fortnight" title="Fortnight">Fortnight</a></li> <li><a href="/wiki/Month" title="Month">Month</a></li> <li><a href="/wiki/Year" title="Year">Year</a></li> <li><a href="/wiki/Olympiad" title="Olympiad">Olympiad</a></li> <li><a href="/wiki/Lustrum" title="Lustrum">Lustrum</a></li> <li><a href="/wiki/Decade" title="Decade">Decade</a></li> <li><a href="/wiki/Century" title="Century">Century</a></li> <li><a href="/wiki/Saeculum" title="Saeculum">Saeculum</a></li> <li><a href="/wiki/Millennium" title="Millennium">Millennium</a></li></ul> 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