{"id":29189,"date":"2014-01-10T09:52:49","date_gmt":"2014-01-10T08:52:49","guid":{"rendered":"https:\/\/www.ufe.cz\/z-prednasky-alexandra-kuny-kde-se-vzala-prestupna-sekunda\/"},"modified":"2025-08-22T10:25:04","modified_gmt":"2025-08-22T08:25:04","slug":"from-the-lecture-of-alexander-kuna-where-did-the-leap-second-come-from","status":"publish","type":"post","link":"https:\/\/www.ufe.cz\/en\/from-the-lecture-of-alexander-kuna-where-did-the-leap-second-come-from\/","title":{"rendered":"From the lecture of Alexander Kuna: Where did the leap second come from?"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"29189\" class=\"elementor elementor-29189 elementor-29178\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-85ff9c2 e-flex e-con-boxed e-con e-parent\" data-id=\"85ff9c2\" data-element_type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-27f5dfc elementor-widget elementor-widget-text-editor\" data-id=\"27f5dfc\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p>The presentation was introduced in the spirit of Werich&#8217;s definition of time: &#8220;people came up with time in order to know &#8211; from when to when and what do you want for it&#8221; at the Pilsen Observatory and Planetarium on January 8th, 2014. He talked about the history of time keeping and the definition of basic unit &#8211; the second.\u00a0<span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">For those who<\/span>\u00a0<span class=\"hps\">do not know where<\/span>\u00a0<span class=\"hps\">the name<\/span>\u00a0<span class=\"hps\">comes from,\u00a0<\/span><\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\">\u00a0<span class=\"hps\">the<\/span>\u00a0<span class=\"hps\">second was the<\/span>\u00a0<span class=\"hps\">designation<\/span>\u00a0<span class=\"hps\">for the second<\/span>\u00a0<span class=\"hps atn\">(<\/span>seconde)\u00a0<span class=\"hps\">sexagesimal<\/span>\u00a0<span class=\"hps alt-edited\">division of<\/span>\u00a0<span class=\"hps\">hours<\/span>\u00a0<span class=\"hps\">already<\/span>\u00a0at the time of\u00a0<span class=\"hps\">Ptolemy. The Czech, often misused, second comes from\u00a0<\/span><\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">a similar<\/span>\u00a0<span class=\"hps\">expression<\/span>\u00a0<span class=\"hps atn\">in Russian (<\/span>\u0432\u0442\u043e\u0440\u043e\u0439\u00a0<span class=\"hps\">= second<\/span>). Other standards\u00a0<\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">(ie<\/span>\u00a0<span class=\"hps\">standards<\/span>\u00a0<span class=\"hps\">of individual<\/span>\u00a0<span class=\"hps\">physical quantities)<\/span>\u00a0are defined with the use of time constants b<\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\">ecause time can be so easily and accurately measured.\u00a0<\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">For example, a<\/span>\u00a0<span class=\"hps\">meter<\/span>\u00a0<span class=\"hps\">is the distance<\/span>\u00a0<span class=\"hps\">traveled by<\/span>\u00a0<span class=\"hps\">light in vacuum during<\/span>\u00a0<span class=\"hps\">a<\/span>\u00a0<span class=\"hps\">specific fraction of time<\/span>. The definition of a meter is therefore based on two constants &#8211; the speed of light and a time interval.<\/span><\/p><p><strong><span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">The leap second<\/span><\/span><\/strong><span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">\u00a0<\/span><\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\">\u00a0<span class=\"hps\">is inserted<\/span>\u00a0<span class=\"hps\">at most twice<\/span>\u00a0<span class=\"hps\">a year<\/span>\u00a0in a way that\u00a0<span class=\"hps\">the last<\/span>\u00a0<span class=\"hps\">minute<\/span>\u00a0<span class=\"hps\">of<\/span>\u00a0<span class=\"hps\">the<\/span>\u00a0<span class=\"hps\">day<\/span>\u00a0<span class=\"hps\">has 61<\/span>\u00a0<span class=\"hps\">seconds.<\/span><\/span><span id=\"result_box\" lang=\"en\" xml:lang=\"en\"><span class=\"hps\">\u00a0<\/span><\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Alexander Kuna spoke about the second &#8211; the intangible, nevertheless one of the fundamental physical variables. Time itself is hard to describe, but it can be measured perfectly.<\/p>\n","protected":false},"author":7,"featured_media":29182,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[51],"tags":[],"acf":[],"_links":{"self":[{"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/posts\/29189"}],"collection":[{"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/comments?post=29189"}],"version-history":[{"count":0,"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/posts\/29189\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/media\/29182"}],"wp:attachment":[{"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/media?parent=29189"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/categories?post=29189"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ufe.cz\/en\/wp-json\/wp\/v2\/tags?post=29189"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}