The universe is expanding \u2013 but how fast exactly? The answer depends on whether you estimate the cosmic expansion rate \u2013 the Hubble\u2019s constant or H0 \u2013 based on the echo of the Big Bang or measure H0 directly based on today\u2019s stars and galaxies. This problem, the Hubble tension, has puzzled astrophysicists and cosmologists worldwide.<\/p>\n\n\n\n
A study by the Ecole Polytechnique F\u00e9d\u00e9rale de Lausanne (EPFL) and led by Richard Anderson adds a new piece to the puzzle. Their research<\/a>, the institution says in a press release<\/a>, achieved the most accurate calibration of Cepheid stars. This a variable star whose luminosity fluctuates over a defined period \u2013 for distance measurements to date based on data collected by the European Space Agency\u2019s (ESA\u2019s) Gaia mission.<\/em> This new calibration further amplifies the Hubble tension.<\/p>\n\n\n The Hubble constant (H0) is named after the astrophysicist who, together with Georges Lema\u00eetre, discovered the phenomenon in the late 1920s.<\/p>\n\n\n\n The best direct measurement of H0 uses a \u201ccosmic distance ladder,\u201d whose first rung is set by the absolute calibration of the brightness of Cepheids, now recalibrated by the EPFL study. In turn, Cepheids calibrate the next rung of the ladder, where supernovae \u2013 powerful explosions of stars at the end of their lives \u2013 trace the expansion of space itself. H0 can also be determined by interpreting the CMB \u2013 the ubiquitous microwave radiation left over from the Big Bang more than 13 billion years ago. However, this \u201cearly Universe\u201d measurement method has to assume<\/em> the most detailed physical understanding of how the Universe evolves, rendering it model dependent.<\/p>\n\n\n These two models present a discrepancy in value.<\/p>\n\n\n\n The Hubble tension refers to this discrepancy, depending on whether the CMB (early Universe) method or the distance ladder (late Universe) method is used. The implication, provided that the measurements performed in both ways are correct, is that there is something wrong with understanding the fundamental physical laws that govern the Universe. Naturally, this significant issue underscores how essential astrophysicists’ methods are to be reliable.<\/p>\n\n\n\n The new EPFL study is noteworthy because it strengthens the first rung of the distance ladder by improving the calibration of Cepheids as distance tracers.<\/p>\n\n\n\n Given the vast scale of the Universe, why does a difference of just a few km\/s\/Mpc matter? “This discrepancy has a huge significance,” says Anderson. “Suppose you wanted to build a tunnel by digging into two opposite sides of a mountain. If you’ve understood the type of rock correctly and your calculations are correct, the two holes you’re digging will meet in the center. But if they don’t, that means you’ve made a mistake \u2013 either your calculations are wrong, or you’re wrong about the type of rock. That’s what’s going on with the Hubble constant. The more confirmation we get that our calculations are accurate, the more we can conclude that the discrepancy means our understanding of the Universe is mistaken, that the Universe isn’t quite as we thought.”<\/p>\n","protected":false},"author":2583,"featured_media":492785,"template":"views\/single-selected.blade.php","meta":{"_acf_changed":false,"advgb_blocks_editor_width":"","advgb_blocks_columns_visual_guide":""},"categories":[76370,42],"tags":[45865,39636,130098,4261,6158,66580],"location":[52892],"internal_archives":[],"class_list":["post-442555","selected","type-selected","status-publish","has-post-thumbnail","hentry","category-science","category-sustainability-nl","tag-astrophysics","tag-epfl-en","tag-hubble-constant","tag-research","tag-space","tag-universe","location-switzerland"],"blocksy_meta":[],"acf":[],"featured_img":"https:\/\/ioplus.nl\/archive\/wp-content\/uploads\/2023\/03\/pexels-pixabay-41006.jpg","coauthors":[],"author_meta":{"author_link":"https:\/\/ioplus.nl\/archive\/author\/francesco-morelli\/","display_name":"Francesco Morelli"},"relative_dates":{"created":"Posted 3 years ago","modified":"Updated 3 years ago"},"absolute_dates":{"created":"Posted on April 6, 2023","modified":"Updated on April 6, 2023"},"absolute_dates_time":{"created":"Posted on April 6, 2023 3:00 pm","modified":"Updated on April 6, 2023 3:00 pm"},"featured_img_caption":"","tax_additional":{"category":{"linked":["Science<\/a>","Sustainability<\/a>"],"unlinked":["Science<\/span>","Sustainability<\/span>"],"slug":"category","name":"Categories"},"post_tag":{"linked":["astrophysics<\/a>","EPFL<\/a>","Hubble constant<\/a>","research<\/a>","space<\/a>","universe<\/a>"],"unlinked":["astrophysics<\/span>","EPFL<\/span>","Hubble constant<\/span>","research<\/span>","space<\/span>","universe<\/span>"],"slug":"post_tag","name":"Tags"},"language":{"linked":["EN<\/a>"],"unlinked":["EN<\/span>"],"slug":"language","name":"Tags"},"post_translations":{"linked":["pll_642e91a895ad4<\/a>"],"unlinked":["pll_642e91a895ad4<\/span>"],"slug":"post_translations","name":""},"location":{"linked":["Switzerland<\/a>"],"unlinked":["Switzerland<\/span>"],"slug":"location","name":"Locations"},"internal_archives":{"linked":[],"unlinked":[],"slug":"internal_archives","name":"Internal Archives"}},"series_order":"","_links":{"self":[{"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/selected\/442555","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/selected"}],"about":[{"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/types\/selected"}],"author":[{"embeddable":true,"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/users\/2583"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/media\/492785"}],"wp:attachment":[{"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/media?parent=442555"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/categories?post=442555"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/tags?post=442555"},{"taxonomy":"location","embeddable":true,"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/location?post=442555"},{"taxonomy":"internal_archives","embeddable":true,"href":"https:\/\/ioplus.nl\/archive\/wp-json\/wp\/v2\/internal_archives?post=442555"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}What is the Hubble Constant?<\/strong><\/h2>\n\n\n\n
Do we understand the universe correctly?<\/strong><\/h2>\n\n\n\n
So, what’s the matter?<\/h2>\n\n\n\n