{"id":45996,"date":"2025-05-01T15:36:24","date_gmt":"2025-05-01T10:06:24","guid":{"rendered":"https:\/\/vajiramandravi.com\/current-affairs\/?p=45996"},"modified":"2025-05-13T15:58:41","modified_gmt":"2025-05-13T10:28:41","slug":"s8-tension","status":"publish","type":"post","link":"https:\/\/vajiramandravi.com\/current-affairs\/s8-tension\/","title":{"rendered":"S8 Tension"},"content":{"rendered":"<h2>S8 Tension Latest News<\/h2>\n<p>The Subaru Telescope in Hawaii, using the Hyper Suprime-Cam, conducted a deep sky survey from the University of Tokyo, reported an S8 value of 0.747, consistent with prior lensing estimates.<\/p>\n<h2>What is S8?<\/h2>\n<ul>\n<li><strong>S8 (Sigma Eight)<\/strong>\u00a0is a parameter used in\u00a0<strong>cosmology to quantify the &#8220;clumpiness&#8221; or clustering of matter<\/strong>\u00a0in the universe on a scale of about\u00a0<strong>26 million light-years<\/strong>.<\/li>\n<li>It helps determine\u00a0<strong>how much matter (both visible and dark) is clustered<\/strong>\u00a0in different cosmic regions.<\/li>\n<\/ul>\n<h2>Background<\/h2>\n<ul>\n<li>The\u00a0<strong>universe began<\/strong>\u00a0with the\u00a0<strong>Big Bang ~13.8 billion years ago<\/strong>, starting off\u00a0<strong>highly uniform<\/strong>, as revealed by the\u00a0<strong>Cosmic Microwave Background (CMB)<\/strong>.<\/li>\n<li><strong>Small fluctuations in density<\/strong>\u00a0(1 in 100,000) eventually evolved into\u00a0<strong>galaxies, star clusters, and filaments<\/strong>, forming the\u00a0<strong>lumpy structure<\/strong>\u00a0of the present universe.<\/li>\n<\/ul>\n<h2>What is the S8 Tension?<\/h2>\n<ul>\n<li>The\u00a0<strong>S8 tension<\/strong>\u00a0refers to the\u00a0<strong>mismatch in the value of S8<\/strong>\u00a0as obtained by:\n<ul>\n<li><strong>CMB measurements<\/strong>\u00a0(higher value).<\/li>\n<li><strong>Cosmic shear\/lensing surveys<\/strong>\u00a0(lower value).<\/li>\n<\/ul>\n<\/li>\n<li>This discrepancy challenges the\u00a0<strong>\u039bCDM (Lambda Cold Dark Matter)<\/strong>\u00a0model, the\u00a0<strong>standard model of cosmology<\/strong>.<\/li>\n<\/ul>\n<h3>Cosmic Microwave Background (CMB)<\/h3>\n<ul>\n<li>CMB is a\u00a0<strong>sea of photons<\/strong>, the particles of light,\u00a0<strong>present throughout<\/strong>\u00a0the\u00a0<strong>universe<\/strong>. They are left over from the Big Bang, its afterglow.<\/li>\n<li>Scientists have\u00a0<strong>measured temperature changes in the CMB<\/strong>\u00a0and studied its large-scale properties using complicated trigonometry.<\/li>\n<li><strong>Based on these studies<\/strong>, cosmologists have\u00a0<strong>estimated space to be expanding at<\/strong>\u00a0around 68 kilometres per second per megaparsec ((km\/s)\/Mpc). That is, an object one megaparsec (3.26 million lightyears) away is moving away at\u00a0<strong>68 km\/s)\/Mpc.<\/strong><\/li>\n<\/ul>\n<h3>Cosmic Shear &amp; Gravitational Lensing<\/h3>\n<ul>\n<li><strong>Cosmic shear<\/strong>\u00a0refers to the\u00a0<strong>distortion in galaxy shapes<\/strong>\u00a0due to\u00a0<strong>gravitational lensing<\/strong>\u00a0by intervening matter.<\/li>\n<li>This lensing helps map\u00a0<strong>dark matter distribution<\/strong>\u00a0and provides an\u00a0<strong>indirect method to calculate S8<\/strong>.<\/li>\n<li><strong>Lower S8 from lensing<\/strong>\u00a0suggests\u00a0<strong>less clumping<\/strong>\u00a0than expected.<\/li>\n<\/ul>\n<p><strong>Source:\u00a0<\/strong><a href=\"https:\/\/www.thehindu.com\/sci-tech\/science\/s8-tension-cosmologists-cant-agree-on-how-clumpy-the-universe-is\/article69508288.ece#:~:text=Cosmologists%20use%20the%20term%20S8,S8%20turned%20up%20different%20estimates\" target=\"_blank\" rel=\"nofollow noopener\">TH<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>S8 (Sigma Eight) is a parameter used in cosmology to quantify the &#8220;clumpiness&#8221; or clustering of matter in the universe on a scale of about 26 million light-years.<\/p>\n","protected":false},"author":11,"featured_media":45997,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[21,232,23],"class_list":{"0":"post-45996","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-upsc-prelims-current-affairs","8":"tag-prelims-pointers","9":"tag-s8-tension","10":"tag-upsc-prelims-current-affairs","11":"no-featured-image-padding"},"acf":[],"_links":{"self":[{"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/posts\/45996","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/users\/11"}],"replies":[{"embeddable":true,"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/comments?post=45996"}],"version-history":[{"count":0,"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/posts\/45996\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/media\/45997"}],"wp:attachment":[{"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/media?parent=45996"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/categories?post=45996"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vajiramandravi.com\/current-affairs\/wp-json\/wp\/v2\/tags?post=45996"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}