{"id":349008,"date":"2025-06-18T13:26:33","date_gmt":"2025-06-18T12:26:33","guid":{"rendered":"https:\/\/zakrasnejsivimperk.cz\/?p=349008"},"modified":"2025-06-21T22:29:35","modified_gmt":"2025-06-21T21:29:35","slug":"astronomicky-ustav-v-sobotu-21-cervna-nastava-letni-slunovrat","status":"publish","type":"post","link":"https:\/\/zakrasnejsivimperk.cz\/?p=349008","title":{"rendered":"ASTRONOMICK\u00dd \u00daSTAV:  V sobotu 21. \u010dervna nast\u00e1v\u00e1 letn\u00ed slunovrat"},"content":{"rendered":"<figure id=\"attachment_349066\" aria-describedby=\"caption-attachment-349066\" style=\"width: 960px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-349066 size-full\" src=\"https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/slunce.webp\" alt=\"\" width=\"960\" height=\"540\" srcset=\"https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/slunce.webp 960w, https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/slunce-300x169.webp 300w, https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/slunce-768x432.webp 768w, https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/slunce-635x357.webp 635w, https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/slunce-859x483.webp 859w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><figcaption id=\"caption-attachment-349066\" class=\"wp-caption-text\">Ilustra\u010dn\u00ed foto: pixabay<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<h6 class=\"-wm-MsoNormal\">V\u00a0sobotu 21. \u010dervna ve 4 hodiny a 43 minut na\u0161eho (st\u0159edoevropsk\u00e9ho letn\u00edho) \u010dasu nastane letn\u00ed slunovrat a za\u010dne astronomick\u00e9 l\u00e9to. P\u0159i letn\u00edm slunovratu Slunce dos\u00e1hne nejsevern\u011bj\u0161\u00edho bodu sv\u00e9 dr\u00e1hy, na severn\u00ed polokouli tak za\u017eijeme nejdel\u0161\u00ed den v roce. Dny se pak ale u\u017e za\u010dnou zkracovat, a to a\u017e do zimn\u00edho slunovratu 21. prosince 2025.<\/h6>\n<p class=\"-wm-MsoNormal\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-181090 alignright\" src=\"https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2020\/01\/02\/astronomick\u00fd-\u00fastav-logo-300x122.png\" alt=\"\" width=\"300\" height=\"122\" srcset=\"https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2020\/01\/02\/astronomick\u00fd-\u00fastav-logo-300x122.png 300w, https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2020\/01\/02\/astronomick\u00fd-\u00fastav-logo.png 437w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/>A pro jistotu: l\u00e9to na severn\u00ed polokouli nem\u00e1me proto, \u017ee je Zem\u011b nejbl\u00ed\u017ee ke Slunci. Je to dokonce p\u0159esn\u011b naopak. Zem\u011b je v tomto ro\u010dn\u00edm obdob\u00ed od Slunce nejd\u00e1le \u2013 letos to nastane 3. \u010dervence ve 22 hodin, kdy n\u00e1s od Slunce bude d\u011blit 152,1 milionu kilometr\u016f. Na st\u0159\u00edd\u00e1n\u00ed ro\u010dn\u00edch obdob\u00ed m\u00e1 toti\u017e vzd\u00e1lenost Zem\u011b od Slunce velmi mal\u00fd vliv. Kl\u00ed\u010dovou roli hraje to, jak je na\u0161e planeta slune\u010dn\u00edm paprsk\u016fm vystavena. Ta m\u00edsta zemsk\u00e9ho povrchu, kde je l\u00e9to, jsou ke Slunci p\u0159iklon\u011bna a slune\u010dn\u00ed paprsky na n\u011b dopadaj\u00ed v\u00edce zp\u0159\u00edma, zat\u00edmco oblasti, kter\u00e9 jsou od Slunce odklon\u011bny a slune\u010dn\u00ed paprsky do t\u011bchto m\u00edst dopadaj\u00ed \u0161ikmo pod mal\u00fdmi \u00fahly, za\u017e\u00edvaj\u00ed zimu. Na severn\u00ed polokouli p\u0159iklon\u011bn\u00e9 ke Slunci proto nyn\u00ed pro\u017e\u00edv\u00e1me tepl\u00e9 obdob\u00ed, zat\u00edmco na odklon\u011bn\u00e9 ji\u017en\u00ed polokouli maj\u00ed v t\u00e9to dob\u011b naopak zimu.<\/p>\n<p class=\"-wm-MsoNormal\">Letn\u00ed slunovrat nast\u00e1v\u00e1 obvykle 20. \u010di 21. \u010dervna. Vz\u00e1cn\u011b m\u016f\u017ee b\u00fdt 22. \u010dervna \u2013 naposledy se tak stalo roku 1975 a p\u0159\u00ed\u0161t\u011b to bude v roce 2203. Nebo i 19. \u010dervna, na takov\u00e9 datum si mus\u00edme po\u010dkat a\u017e do roku 2487. Pro\u010d tomu tak je? Kalend\u00e1\u0159n\u00ed rok trv\u00e1 365 nebo 366 dn\u00ed, ale Zem\u011b ob\u011bhne kolem Slunce za 365 dn\u00ed 5 hodin 49 minut. Proto se okam\u017eik letn\u00edho slunovratu opo\u017e\u010fuje ka\u017ed\u00fd n\u00e1sleduj\u00edc\u00ed rok o p\u0159eb\u00fdvaj\u00edc\u00edch 5h 49min. Za\u0159azen\u00edm p\u0159estupn\u00e9ho roku se okam\u017eik letn\u00edho slunovratu \u201ep\u0159edb\u011bhne\u201c o 24h \u2013 5h 49min = 18h 11min. P\u0159itom m\u016f\u017ee doj\u00edt ke zm\u011bn\u011b data letn\u00edho slunovratu.<\/p>\n<p class=\"-wm-MsoNormal\">Sou\u010dasn\u00fd (\u0159eho\u0159sk\u00fd neboli gregori\u00e1nsk\u00fd) kalend\u00e1\u0159 \u201epracuje\u201c ve 400let\u00fdch cyklech. Rokem 2000 jsme vstoupili do nov\u00e9ho cyklu a na jeho za\u010d\u00e1tku vzniknou nejv\u011bt\u0161\u00ed rozd\u00edly. Proto ve 21. stolet\u00ed p\u0159ipadne letn\u00ed slunovrat 62kr\u00e1t na 21. 6. a 38kr\u00e1t na 20. 6. (pokud vych\u00e1z\u00edme ze st\u0159edoevropsk\u00e9ho letn\u00edho \u010dasu). Na 20. 6. p\u0159ipadl letn\u00ed slunovrat v roce 2020 (poprv\u00e9 od roku 1796), v\u00a0roce 2024 a nastane d\u00e1le v letech 2028, 2032, atd.<\/p>\n<p class=\"-wm-MsoNormal\">K pomal\u00fdm zm\u011bn\u00e1m doch\u00e1z\u00ed i zm\u011bnami zemsk\u00e9 dr\u00e1hy. Dnes je z ro\u010dn\u00edch dob nejdel\u0161\u00ed l\u00e9to a velmi zvolna se je\u0161t\u011b prodlu\u017euje (o 6h 29min do roku 3000).<\/p>\n<p class=\"-wm-MsoNormal\">Pojmenov\u00e1n\u00ed slunovrat vzniklo na z\u00e1klad\u011b pozorov\u00e1n\u00ed v\u00fdchod\u016f a z\u00e1pad\u016f Slunce. V m\u011bs\u00edc\u00edch p\u0159ed \u010dervnov\u00fdm slunovratem se pozice v\u00fdchodu a z\u00e1padu pozvolna posouvaj\u00ed k severu, v den slunovratu dos\u00e1hnou nejsevern\u011bj\u0161\u00edho bodu a pot\u00e9 se op\u011bt vydaj\u00ed sm\u011brem k jihu.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Pavel SUCHAN, Astronomick\u00fd \u00fastav AV \u010cR<\/strong><\/p>\n<hr \/>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>&nbsp; V\u00a0sobotu <\/p>\n","protected":false},"author":2,"featured_media":349067,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"gallery","meta":{"footnotes":""},"categories":[110],"tags":[],"jetpack_featured_media_url":"https:\/\/zakrasnejsivimperk.cz\/wp-content\/uploads\/2025\/06\/18\/ram-slunovrat.jpg","_links":{"self":[{"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/posts\/349008"}],"collection":[{"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=349008"}],"version-history":[{"count":2,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/posts\/349008\/revisions"}],"predecessor-version":[{"id":349068,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/posts\/349008\/revisions\/349068"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=\/wp\/v2\/media\/349067"}],"wp:attachment":[{"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=349008"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=349008"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zakrasnejsivimperk.cz\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=349008"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}