{"id":799,"date":"2014-09-11T05:36:44","date_gmt":"2014-09-11T05:36:44","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/feldmann\/?p=799"},"modified":"2014-09-17T05:25:19","modified_gmt":"2014-09-17T05:25:19","slug":"cadran-solaire","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/feldmann\/2014\/09\/11\/cadran-solaire\/","title":{"rendered":"Le cadran solaire"},"content":{"rendered":"<p>Depuis toujours les hommes cherchent \u00e0 mesurer l&#8217;\u00e9coulement du temps et \u00e0 conna\u00eetre l&#8217;heure, indispensable pour signaler les moments des travaux et ceux des pri\u00e8res.<\/p>\n<p><a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran1.jpg\" rel=\"lightbox[799]\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-803\" src=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran1-450x337.jpg\" alt=\"cadran1\" width=\"450\" height=\"337\" srcset=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran1-450x337.jpg 450w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran1-1024x768.jpg 1024w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran1.jpg 1200w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/a><\/p>\n<p>Il \u00e9tait donc assez logique qu&#8217;on pensa tr\u00e8s t\u00f4t \u00e0 utiliser le <a title=\"Le Soleil dans le lac\" href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2014\/06\/04\/soleil-lac\/\" target=\"_blank\">Soleil <\/a>et sa course apparente quotidienne dans le ciel comme marqueur de temps.<\/p>\n<p><!--more-->Le principe du cadran solaire (dont les plus anciens mod\u00e8les retrouv\u00e9s en Egypte datent du troisi\u00e8me si\u00e8cle avant J-C) est simple : projeter l&#8217;ombre d&#8217;un objet (en r\u00e8gle g\u00e9n\u00e9rale une tige surnomm\u00e9e gnomon ou style) sur une surface gradu\u00e9e.<\/p>\n<p><a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran2.jpg\" rel=\"lightbox[799]\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-804\" src=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran2-450x337.jpg\" alt=\"cadran2\" width=\"450\" height=\"337\" srcset=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran2-450x337.jpg 450w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran2-1024x768.jpg 1024w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran2.jpg 1200w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/a><\/p>\n<p>La mise en pratique est un peu plus compliqu\u00e9e : il faut en effet que le style soit parall\u00e8le \u00e0 l&#8217;axe de rotation de la Terre, axe imaginaire qui se prolonge dans le ciel en direction de l&#8217;<a title=\"Elle tourne, elle tourne\u2026\" href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2014\/05\/04\/tourne-tourne\/\" target=\"_blank\">\u00e9toile polaire<\/a>.<\/p>\n<p>L&#8217;ombre projet\u00e9e sur le cadran indique l&#8217;heure solaire vraie. Pour avoir l&#8217;heure l\u00e9gale de la montre, il est n\u00e9cessaire d&#8217;apporter diff\u00e9rentes corrections qui tiennent compte du fuseau horaire local, de l&#8217;\u00e9cart en longitude avec le m\u00e9ridien de r\u00e9f\u00e9rence (celui de <a title=\"Le m\u00e9ridien de Greenwich\" href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2014\/09\/05\/meridien-greenwich\/\" target=\"_blank\">Greenwich<\/a>) et de la variabilit\u00e9 de la vitesse de la Terre sur son orbite durant l&#8217;ann\u00e9e (ce param\u00e8tre est appel\u00e9 l&#8217;\u00e9quation du temps).<\/p>\n<p><a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran3.jpg\" rel=\"lightbox[799]\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-805\" src=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran3-450x337.jpg\" alt=\"cadran3\" width=\"450\" height=\"337\" srcset=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran3-450x337.jpg 450w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran3-1024x767.jpg 1024w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2014\/09\/cadran3.jpg 1200w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/a><\/p>\n<p>Les cadrans solaires pr\u00e9sent\u00e9s dans cet articles ont \u00e9t\u00e9 photographi\u00e9s dans trois villages du Beaujolais (de haut en bas Amb\u00e9rieux d&#8217;Azergue, Oingt et Theiz\u00e9)<\/p>\n<!-- AddThis Advanced Settings generic via filter on the_content --><!-- AddThis Share Buttons generic via filter on the_content -->","protected":false},"excerpt":{"rendered":"<p>Depuis toujours les hommes cherchent \u00e0 mesurer l&#8217;\u00e9coulement du temps et \u00e0 conna\u00eetre l&#8217;heure, indispensable pour signaler les moments des travaux et ceux des pri\u00e8res. Il \u00e9tait donc assez logique qu&#8217;on pensa tr\u00e8s t\u00f4t \u00e0 utiliser le Soleil et sa course apparente quotidienne dans le ciel comme marqueur de temps.<!-- AddThis Advanced Settings generic via filter on get_the_excerpt --><!-- AddThis Share Buttons generic via filter on get_the_excerpt --><\/p>\n","protected":false},"author":8,"featured_media":803,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[87],"tags":[356,360,359,98,358,97,357,175],"class_list":["post-799","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-les-hommes-et-le-ciel","tag-cadran-solaire","tag-egypte","tag-equation-du-temps","tag-etoile-polaire","tag-gnomon","tag-soleil","tag-style","tag-terre"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.1 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Le cadran solaire<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2014\/09\/11\/cadran-solaire\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Le cadran solaire\" \/>\n<meta property=\"og:description\" content=\"Depuis toujours les hommes cherchent \u00e0 mesurer l&#8217;\u00e9coulement du temps et \u00e0 conna\u00eetre l&#8217;heure, indispensable pour signaler les moments des travaux et ceux des pri\u00e8res. 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