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<div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>"The universe" versus "the observable universe"</span> </div> </a> <ul id="toc-"The_universe"_versus_"the_observable_universe"-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Size" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Size"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Size</span> </div> </a> <ul id="toc-Size-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Matter_and_mass" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Matter_and_mass"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Matter and mass</span> </div> </a> <button aria-controls="toc-Matter_and_mass-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Matter and mass subsection</span> </button> <ul id="toc-Matter_and_mass-sublist" class="vector-toc-list"> <li id="toc-Number_of_galaxies_and_stars" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Number_of_galaxies_and_stars"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Number of galaxies and stars</span> </div> </a> <ul id="toc-Number_of_galaxies_and_stars-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Matter_content—number_of_atoms" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Matter_content—number_of_atoms"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Matter content—number of atoms</span> </div> </a> <ul id="toc-Matter_content—number_of_atoms-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Mass_of_ordinary_matter" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Mass_of_ordinary_matter"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Mass of ordinary matter</span> </div> </a> <ul id="toc-Mass_of_ordinary_matter-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Estimates_based_on_critical_density" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Estimates_based_on_critical_density"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.4</span> <span>Estimates based on critical density</span> </div> </a> <ul id="toc-Estimates_based_on_critical_density-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Large-scale_structure" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Large-scale_structure"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Large-scale structure</span> </div> </a> <button aria-controls="toc-Large-scale_structure-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Large-scale structure subsection</span> </button> <ul id="toc-Large-scale_structure-sublist" class="vector-toc-list"> <li id="toc-Cosmic_Web:_walls,_filaments,_nodes,_and_voids" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cosmic_Web:_walls,_filaments,_nodes,_and_voids"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Cosmic Web: walls, filaments, nodes, and voids</span> </div> </a> <ul id="toc-Cosmic_Web:_walls,_filaments,_nodes,_and_voids-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-End_of_Greatness" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#End_of_Greatness"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>End of Greatness</span> </div> </a> <ul id="toc-End_of_Greatness-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Observations" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Observations"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Observations</span> </div> </a> <ul id="toc-Observations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cosmography_of_Earth's_cosmic_neighborhood" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cosmography_of_Earth's_cosmic_neighborhood"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.4</span> <span>Cosmography of Earth's cosmic neighborhood</span> </div> </a> <ul id="toc-Cosmography_of_Earth's_cosmic_neighborhood-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Most_distant_objects" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Most_distant_objects"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Most distant objects</span> </div> </a> <ul id="toc-Most_distant_objects-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Horizons" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Horizons"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Horizons</span> </div> </a> <ul id="toc-Horizons-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Gallery" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Gallery"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Gallery</span> </div> </a> <ul id="toc-Gallery-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">12</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">13</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Observable universe</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 61 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-61" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">61 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://af.wikipedia.org/wiki/Sigbare_heelal" title="Sigbare heelal – Afrikaans" lang="af" hreflang="af" data-title="Sigbare heelal" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%A7%D9%84%D9%83%D9%88%D9%86_%D8%A7%D9%84%D9%85%D8%B1%D8%B5%D9%88%D8%AF" title="الكون المرصود – Arabic" lang="ar" hreflang="ar" data-title="الكون المرصود" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Universu_observable" title="Universu observable – Asturian" lang="ast" hreflang="ast" data-title="Universu observable" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AA%E0%A6%B0%E0%A7%8D%E0%A6%AF%E0%A6%AC%E0%A7%87%E0%A6%95%E0%A7%8D%E0%A6%B7%E0%A6%A3%E0%A6%AF%E0%A7%8B%E0%A6%97%E0%A7%8D%E0%A6%AF_%E0%A6%AE%E0%A6%B9%E0%A6%BE%E0%A6%AC%E0%A6%BF%E0%A6%B6%E0%A7%8D%E0%A6%AC" title="পর্যবেক্ষণযোগ্য মহাবিশ্ব – Bangla" lang="bn" hreflang="bn" data-title="পর্যবেক্ষণযোগ্য মহাবিশ্ব" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9D%D0%B0%D0%B1%D0%BB%D1%8E%D0%B4%D0%B0%D0%B5%D0%BC%D0%B0_%D0%B2%D1%81%D0%B5%D0%BB%D0%B5%D0%BD%D0%B0" title="Наблюдаема вселена – Bulgarian" lang="bg" hreflang="bg" data-title="Наблюдаема вселена" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Univers_observable" title="Univers observable – Catalan" lang="ca" hreflang="ca" data-title="Univers observable" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/%D0%9C%D0%B5%D1%82%D0%B0%D0%B3%D0%B0%D0%BB%D0%B0%D0%BA%D1%82%D0%B8%D0%BA%D0%B0" title="Метагалактика – Chuvash" lang="cv" hreflang="cv" data-title="Метагалактика" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target"><span>Чӑвашла</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Pozorovateln%C3%BD_vesm%C3%ADr" title="Pozorovatelný vesmír – Czech" lang="cs" hreflang="cs" data-title="Pozorovatelný vesmír" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Observerbare_univers" title="Observerbare univers – Danish" lang="da" hreflang="da" data-title="Observerbare univers" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Beobachtbares_Universum" title="Beobachtbares Universum – German" lang="de" hreflang="de" data-title="Beobachtbares Universum" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Vaadeldav_universum" title="Vaadeldav universum – Estonian" lang="et" hreflang="et" data-title="Vaadeldav universum" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A0%CE%B1%CF%81%CE%B1%CF%84%CE%B7%CF%81%CE%AE%CF%83%CE%B9%CE%BC%CE%BF_%CF%83%CF%8D%CE%BC%CF%80%CE%B1%CE%BD" title="Παρατηρήσιμο σύμπαν – Greek" lang="el" hreflang="el" data-title="Παρατηρήσιμο σύμπαν" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Universo_observable" title="Universo observable – Spanish" lang="es" hreflang="es" data-title="Universo observable" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Observebla_universo" title="Observebla universo – Esperanto" lang="eo" hreflang="eo" data-title="Observebla universo" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Unibertso_behagarri" title="Unibertso behagarri – Basque" lang="eu" hreflang="eu" data-title="Unibertso behagarri" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AC%D9%87%D8%A7%D9%86_%D9%82%D8%A7%D8%A8%D9%84_%D9%85%D8%B4%D8%A7%D9%87%D8%AF%D9%87" title="جهان قابل مشاهده – Persian" lang="fa" hreflang="fa" data-title="جهان قابل مشاهده" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Univers_observable" title="Univers observable – French" lang="fr" hreflang="fr" data-title="Univers observable" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Universo_observable" title="Universo observable – Galician" lang="gl" hreflang="gl" data-title="Universo observable" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EA%B4%80%EC%B8%A1_%EA%B0%80%EB%8A%A5%ED%95%9C_%EC%9A%B0%EC%A3%BC" title="관측 가능한 우주 – Korean" lang="ko" hreflang="ko" data-title="관측 가능한 우주" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%84%D5%A5%D5%BF%D5%A1%D5%A3%D5%A1%D5%AC%D5%A1%D5%AF%D5%BF%D5%AB%D5%AF%D5%A1" title="Մետագալակտիկա – Armenian" lang="hy" hreflang="hy" data-title="Մետագալակտիկա" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Alam_semesta_teramati" title="Alam semesta teramati – Indonesian" lang="id" hreflang="id" data-title="Alam semesta teramati" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Universo_osservabile" title="Universo osservabile – Italian" lang="it" hreflang="it" data-title="Universo osservabile" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%94%D7%99%D7%A7%D7%95%D7%9D_%D7%94%D7%A0%D7%A6%D7%A4%D7%94" title="היקום הנצפה – Hebrew" lang="he" hreflang="he" data-title="היקום הנצפה" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9B%E1%83%94%E1%83%A2%E1%83%90%E1%83%92%E1%83%90%E1%83%9A%E1%83%90%E1%83%A5%E1%83%A2%E1%83%98%E1%83%99%E1%83%90" title="მეტაგალაქტიკა – Georgian" lang="ka" hreflang="ka" data-title="მეტაგალაქტიკა" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9C%D0%B5%D1%82%D0%B0%D0%B3%D0%B0%D0%BB%D0%B0%D0%BA%D1%82%D0%B8%D0%BA%D0%B0" title="Метагалактика – Kazakh" lang="kk" hreflang="kk" data-title="Метагалактика" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%9C%D0%B5%D1%82%D0%B0%D0%B3%D0%B0%D0%BB%D0%B0%D0%BA%D1%82%D0%B8%D0%BA%D0%B0" title="Метагалактика – Kyrgyz" lang="ky" hreflang="ky" data-title="Метагалактика" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Metagalaktika" title="Metagalaktika – Lithuanian" lang="lt" hreflang="lt" data-title="Metagalaktika" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Megfigyelhet%C5%91_vil%C3%A1gegyetem" title="Megfigyelhető világegyetem – Hungarian" lang="hu" hreflang="hu" data-title="Megfigyelhető világegyetem" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%A8%E0%B4%BF%E0%B4%B0%E0%B5%80%E0%B4%95%E0%B5%8D%E0%B4%B7%E0%B4%A3%E0%B4%AF%E0%B5%8B%E0%B4%97%E0%B5%8D%E0%B4%AF_%E0%B4%AA%E0%B5%8D%E0%B4%B0%E0%B4%AA%E0%B4%9E%E0%B5%8D%E0%B4%9A%E0%B4%82" title="നിരീക്ഷണയോഗ്യ പ്രപഞ്ചം – Malayalam" lang="ml" hreflang="ml" data-title="നിരീക്ഷണയോഗ്യ പ്രപഞ്ചം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Alam_semesta_boleh_cerap" title="Alam semesta boleh cerap – Malay" lang="ms" hreflang="ms" data-title="Alam semesta boleh cerap" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%9C%E1%80%B1%E1%80%B7%E1%80%9C%E1%80%AC%E1%80%94%E1%80%AD%E1%80%AF%E1%80%84%E1%80%BA%E1%80%9E%E1%80%B1%E1%80%AC_%E1%80%85%E1%80%80%E1%80%BC%E1%80%9D%E1%80%A0%E1%80%AC" title="လေ့လာနိုင်သော စကြဝဠာ – Burmese" lang="my" hreflang="my" data-title="လေ့လာနိုင်သော စကြဝဠာ" data-language-autonym="မြန်မာဘာသာ" data-language-local-name="Burmese" class="interlanguage-link-target"><span>မြန်မာဘာသာ</span></a></li><li class="interlanguage-link interwiki-pcm mw-list-item"><a href="https://pcm.wikipedia.org/wiki/Obsavabul_univas" title="Obsavabul univas – Nigerian Pidgin" lang="pcm" hreflang="pcm" data-title="Obsavabul univas" data-language-autonym="Naijá" data-language-local-name="Nigerian Pidgin" class="interlanguage-link-target"><span>Naijá</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Waarneembaar_heelal" title="Waarneembaar heelal – Dutch" lang="nl" hreflang="nl" data-title="Waarneembaar heelal" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E8%A6%B3%E6%B8%AC%E5%8F%AF%E8%83%BD%E3%81%AA%E5%AE%87%E5%AE%99" title="観測可能な宇宙 – Japanese" lang="ja" hreflang="ja" data-title="観測可能な宇宙" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Det_observerbare_universet" title="Det observerbare universet – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Det observerbare universet" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Det_observerbare_universet" title="Det observerbare universet – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Det observerbare universet" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Univ%C3%A8rs_Observable" title="Univèrs Observable – Occitan" lang="oc" hreflang="oc" data-title="Univèrs Observable" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-blk mw-list-item"><a href="https://blk.wikipedia.org/wiki/%E1%80%80%E1%80%9C%E1%80%BD%E1%80%B0%EA%A9%BB%E1%80%91%E1%80%BD%E1%80%AC%E1%82%8F%E1%80%94%E1%80%BD%E1%80%B1%E1%80%AC%E1%80%84%E1%80%BA%EA%A9%BB%E1%80%92%E1%80%AB%E1%82%8F_%E1%80%85%E1%80%B2%E1%80%80%E1%80%B9%E1%80%80%E1%80%BB%E1%80%AC%E1%82%8F%E1%80%9D%E1%80%A0%E1%80%AC%E1%82%8F" title="ကလွူꩻထွာႏနွောင်ꩻဒါႏ စဲက္ကျာႏဝဠာႏ – Pa'O" lang="blk" hreflang="blk" data-title="ကလွူꩻထွာႏနွောင်ꩻဒါႏ စဲက္ကျာႏဝဠာႏ" data-language-autonym="ပအိုဝ်ႏဘာႏသာႏ" data-language-local-name="Pa'O" class="interlanguage-link-target"><span>ပအိုဝ်ႏဘာႏသာႏ</span></a></li><li class="interlanguage-link interwiki-ps mw-list-item"><a href="https://ps.wikipedia.org/wiki/%D8%AF_%D9%85%D8%B4%D8%A7%D9%87%D8%AF%DB%90_%D9%88%DA%93_%D9%86%DA%93%DB%8D" title="د مشاهدې وړ نړۍ – Pashto" lang="ps" hreflang="ps" data-title="د مشاهدې وړ نړۍ" data-language-autonym="پښتو" data-language-local-name="Pashto" class="interlanguage-link-target"><span>پښتو</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Widzialny_Wszech%C5%9Bwiat" title="Widzialny Wszechświat – Polish" lang="pl" hreflang="pl" data-title="Widzialny Wszechświat" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Universo_observ%C3%A1vel" title="Universo observável – Portuguese" lang="pt" hreflang="pt" data-title="Universo observável" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Univers_observabil" title="Univers observabil – Romanian" lang="ro" hreflang="ro" data-title="Univers observabil" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9C%D0%B5%D1%82%D0%B0%D0%B3%D0%B0%D0%BB%D0%B0%D0%BA%D1%82%D0%B8%D0%BA%D0%B0" title="Метагалактика – Russian" lang="ru" hreflang="ru" data-title="Метагалактика" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-stq mw-list-item"><a href="https://stq.wikipedia.org/wiki/Beooboachtboar_Al" title="Beooboachtboar Al – Saterland Frisian" lang="stq" hreflang="stq" data-title="Beooboachtboar Al" data-language-autonym="Seeltersk" data-language-local-name="Saterland Frisian" class="interlanguage-link-target"><span>Seeltersk</span></a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Universi_i_v%C3%ABzhguesh%C3%ABm" title="Universi i vëzhgueshëm – Albanian" lang="sq" hreflang="sq" data-title="Universi i vëzhgueshëm" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Observable_universe" title="Observable universe – Simple English" lang="en-simple" hreflang="en-simple" data-title="Observable universe" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Pozorovate%C4%BEn%C3%BD_vesm%C3%ADr" title="Pozorovateľný vesmír – Slovak" lang="sk" hreflang="sk" data-title="Pozorovateľný vesmír" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-ckb mw-list-item"><a href="https://ckb.wikipedia.org/wiki/%DA%AF%DB%95%D8%B1%D8%AF%D9%88%D9%88%D9%86%DB%8C_%DA%86%D8%A7%D9%88%D8%AF%DB%8E%D8%B1%DB%8C%DA%A9%D8%B1%D8%A7%D9%88" title="گەردوونی چاودێریکراو – Central Kurdish" lang="ckb" hreflang="ckb" data-title="گەردوونی چاودێریکراو" data-language-autonym="کوردی" data-language-local-name="Central Kurdish" class="interlanguage-link-target"><span>کوردی</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%92%D0%B8%D0%B4%D1%99%D0%B8%D0%B2%D0%B8_%D1%81%D0%B2%D0%B5%D0%BC%D0%B8%D1%80" title="Видљиви свемир – Serbian" lang="sr" hreflang="sr" data-title="Видљиви свемир" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Vidljivi_svemir" title="Vidljivi svemir – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Vidljivi svemir" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Havaittava_maailmankaikkeus" title="Havaittava maailmankaikkeus – Finnish" lang="fi" hreflang="fi" data-title="Havaittava maailmankaikkeus" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Observerbara_universum" title="Observerbara universum – Swedish" lang="sv" hreflang="sv" data-title="Observerbara universum" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%95%E0%AE%BE%E0%AE%9F%E0%AF%8D%E0%AE%9A%E0%AE%BF%E0%AE%95%E0%AF%8D%E0%AE%95%E0%AF%81%E0%AE%9F%E0%AF%8D%E0%AE%AA%E0%AE%9F%E0%AF%8D%E0%AE%9F_%E0%AE%AA%E0%AF%87%E0%AE%B0%E0%AE%A3%E0%AF%8D%E0%AE%9F%E0%AE%AE%E0%AF%8D" title="காட்சிக்குட்பட்ட பேரண்டம் – Tamil" lang="ta" hreflang="ta" data-title="காட்சிக்குட்பட்ட பேரண்டம்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%80%E0%B8%AD%E0%B8%81%E0%B8%A0%E0%B8%9E%E0%B8%97%E0%B8%B5%E0%B9%88%E0%B8%AA%E0%B8%B1%E0%B8%87%E0%B9%80%E0%B8%81%E0%B8%95%E0%B9%84%E0%B8%94%E0%B9%89" title="เอกภพที่สังเกตได้ – Thai" lang="th" hreflang="th" data-title="เอกภพที่สังเกตได้" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/G%C3%B6zlemlenebilir_evren" title="Gözlemlenebilir evren – Turkish" lang="tr" hreflang="tr" data-title="Gözlemlenebilir evren" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-udm mw-list-item"><a href="https://udm.wikipedia.org/wiki/%D0%9C%D0%B5%D1%82%D0%B0%D0%B3%D0%B0%D0%BB%D0%B0%D0%BA%D1%82%D0%B8%D0%BA%D0%B0" title="Метагалактика – Udmurt" lang="udm" hreflang="udm" data-title="Метагалактика" data-language-autonym="Удмурт" data-language-local-name="Udmurt" class="interlanguage-link-target"><span>Удмурт</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%92%D0%B8%D0%B4%D0%B8%D0%BC%D0%B8%D0%B9_%D0%B2%D1%81%D0%B5%D1%81%D0%B2%D1%96%D1%82" title="Видимий всесвіт – Ukrainian" lang="uk" hreflang="uk" data-title="Видимий всесвіт" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D9%82%D8%A7%D8%A8%D9%84_%D9%85%D8%B4%D8%A7%DB%81%D8%AF%DB%81_%DA%A9%D8%A7%D8%A6%D9%86%D8%A7%D8%AA" title="قابل مشاہدہ کائنات – Urdu" lang="ur" hreflang="ur" data-title="قابل مشاہدہ کائنات" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/V%C5%A9_tr%E1%BB%A5_quan_s%C3%A1t_%C4%91%C6%B0%E1%BB%A3c" title="Vũ trụ quan sát được – Vietnamese" lang="vi" hreflang="vi" data-title="Vũ trụ quan sát được" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E5%8F%AF%E8%A7%80%E6%B8%AC%E5%AE%87%E5%AE%99" title="可觀測宇宙 – Cantonese" lang="yue" hreflang="yue" data-title="可觀測宇宙" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E5%8F%AF%E8%A7%80%E6%B8%AC%E5%AE%87%E5%AE%99" title="可觀測宇宙 – Chinese" lang="zh" hreflang="zh" data-title="可觀測宇宙" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a 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searchaux" style="display:none">All of space observable from the Earth at the present</div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox" style="width:25em;"><caption class="infobox-title">Observable universe</caption><tbody><tr><td colspan="2" class="infobox-image"><span typeof="mw:File"><a href="/wiki/File:Observable_Universe_with_Measurements_01.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Observable_Universe_with_Measurements_01.png/300px-Observable_Universe_with_Measurements_01.png" decoding="async" width="300" height="300" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Observable_Universe_with_Measurements_01.png/450px-Observable_Universe_with_Measurements_01.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/98/Observable_Universe_with_Measurements_01.png/600px-Observable_Universe_with_Measurements_01.png 2x" data-file-width="3072" data-file-height="3072" /></a></span><div class="infobox-caption">Visualization of the observable universe. The scale is such that the fine grains represent collections of large numbers of superclusters. The <a href="/wiki/Virgo_Supercluster" title="Virgo Supercluster">Virgo Supercluster</a>—home of Milky Way—is marked at the center, but is too small to be seen.</div></td></tr><tr><th scope="row" class="infobox-label">Diameter</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7026880000000000000♠"></span>8.8<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>26</sup> m</span> or 880 <a href="/wiki/Yotta-" class="mw-redirect" title="Yotta-">Ym</a> <span class="nowrap">(28.5 <a href="/wiki/Parsec" title="Parsec">Gpc</a> or 93 <a href="/wiki/Light-year" title="Light-year">Gly</a>)</span><sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label">Circumference</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7027276400000000000♠"></span>2.764<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>27</sup> m</span> or 2.764 <a href="/wiki/Ronna-" class="mw-redirect" title="Ronna-">Rm</a> <span class="nowrap">(89.6 <a href="/wiki/Parsec" title="Parsec">Gpc</a> or 292.2 <a href="/wiki/Light-year" title="Light-year">Gly</a>)</span></td></tr><tr><th scope="row" class="infobox-label">Volume</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7080356599999999999♠"></span>3.566<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>80</sup> m<sup>3</sup></span><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label">Mass (ordinary matter)</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7053150000000000000♠"></span>1.5<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>53</sup> kg</span><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>note 1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label">Density (of total energy)</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="6973990000000000000♠"></span>9.9<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−27</sup> kg/m<sup>3</sup></span> (equivalent to 6 <a href="/wiki/Proton" title="Proton">protons</a> per cubic meter of space)<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label">Age</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7010137870000000000♠"></span>13.787<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.020 <a href="/wiki/1,000,000,000" title="1,000,000,000">billion</a></span> years<sup id="cite_ref-Planck_2018_5-0" class="reference"><a href="#cite_note-Planck_2018-5"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label">Average temperature</th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7000272548000000000♠"></span>2.725<span style="margin-left:.25em;">48</span><span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.000<span style="margin-left:.25em;">57</span></span> <a href="/wiki/Kelvin" title="Kelvin">K</a><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label">Contents</th><td class="infobox-data"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style><div class="plainlist"> <ul><li><a href="/wiki/Baryon#Baryonic_matter" title="Baryon">Ordinary (baryonic)</a> <a href="/wiki/Matter" title="Matter">matter</a> (4.9%)</li> <li><a href="/wiki/Dark_matter" title="Dark matter">Dark matter</a> (26.8%)</li> <li><a href="/wiki/Dark_energy" title="Dark energy">Dark energy</a> (68.3%)<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup></li></ul> </div></td></tr></tbody></table> <p>The <b>observable universe</b> is a <a href="/wiki/Ball_(mathematics)" title="Ball (mathematics)">spherical</a> region of the <a href="/wiki/Universe" title="Universe">universe</a> consisting of all <a href="/wiki/Matter" title="Matter">matter</a> that can be <a href="/wiki/Observation" title="Observation">observed</a> from <a href="/wiki/Earth" title="Earth">Earth</a>; the <a href="/wiki/Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic radiation</a> from these <a href="/wiki/Astronomical_object" title="Astronomical object">objects</a> has had time to reach the <a href="/wiki/Solar_System" title="Solar System">Solar System</a> and Earth since the beginning of the <a href="/wiki/Metric_expansion_of_space" class="mw-redirect" title="Metric expansion of space">cosmological expansion</a>. Assuming the universe is <a href="/wiki/Isotropy" title="Isotropy">isotropic</a>, the distance to the edge of the observable universe is roughly <a href="/wiki/Equidistant" title="Equidistant">the same</a> in every direction. That is, the observable universe is a <a href="/wiki/Sphere" title="Sphere">spherical</a> region centered on the observer. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth. </p><p>The word <i>observable</i> in this sense does not refer to the capability of modern technology to detect <a href="/wiki/Light" title="Light">light</a> or other information from an object, or whether there is anything to be detected. It refers to the physical limit created by the <a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a> itself. No signal can travel faster than light, hence there is a maximum distance, called the <a href="/wiki/Particle_horizon" title="Particle horizon">particle horizon</a>, beyond which nothing can be detected, as the signals could not have reached the observer yet. Sometimes astrophysicists distinguish between the observable universe and the <i>visible</i> universe. The former includes signals since the end of the <a href="/wiki/Inflationary_epoch" title="Inflationary epoch">inflationary epoch</a>, while the latter includes only signals emitted since <a href="/wiki/Recombination_(cosmology)" title="Recombination (cosmology)">recombination</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>note 2<span class="cite-bracket">]</span></a></sup> </p><p>According to calculations, the current <a href="/wiki/Comoving_distance" class="mw-redirect" title="Comoving distance">comoving distance</a> to particles from which the <a href="/wiki/Cosmic_microwave_background_radiation" class="mw-redirect" title="Cosmic microwave background radiation">cosmic microwave background radiation</a> (CMBR) was emitted, which represents the radius of the visible universe, is about 14.0 billion <a href="/wiki/Parsec" title="Parsec">parsecs</a> (about 45.7 billion light-years). The comoving distance to the edge of the observable universe is about 14.3 billion parsecs (about 46.6 billion light-years),<sup id="cite_ref-mapofuniverse_9-0" class="reference"><a href="#cite_note-mapofuniverse-9"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> about 2% larger. The <a href="/wiki/Radius" title="Radius">radius</a> of the observable universe is therefore estimated to be about 46.5 billion light-years.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ly93_11-0" class="reference"><a href="#cite_note-ly93-11"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Using the <a href="/wiki/Friedmann_equations" title="Friedmann equations">critical density</a> and the diameter of the observable universe, the total mass of ordinary matter in the universe can be calculated to be about <span class="nowrap"><span data-sort-value="7053150000000000000♠"></span>1.5<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>53</sup> kg</span>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> In November 2018, astronomers reported that <a href="/wiki/Extragalactic_background_light" title="Extragalactic background light">extragalactic background light</a> (EBL) amounted to <span class="nowrap"><span data-sort-value="7084400000000000000♠"></span>4<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>84</sup></span> photons.<sup id="cite_ref-NYT-20181203_13-0" class="reference"><a href="#cite_note-NYT-20181203-13"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-SCI-20181130_14-0" class="reference"><a href="#cite_note-SCI-20181130-14"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p>As the universe's expansion is accelerating, all currently observable objects, outside the local <a href="/wiki/Supercluster" title="Supercluster">supercluster</a>, will eventually appear to freeze in time, while emitting progressively redder and fainter light. For instance, objects with the current <a href="/wiki/Redshift" title="Redshift">redshift</a> <i><a href="/wiki/Redshift#Measurement,_characterization,_and_interpretation" title="Redshift">z</a></i> from 5 to 10 will only be observable up to an age of 4–6 billion years. In addition, light emitted by objects currently situated beyond a certain comoving distance (currently about 19 gigaparsecs (62 Gly)) will never reach Earth.<sup id="cite_ref-Loeb2002_15-0" class="reference"><a href="#cite_note-Loeb2002-15"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=1" title="Edit section: Overview"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output 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rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1246091330" /><table class="sidebar sidebar-collapse nomobile nowraplinks plainlist"><tbody><tr><td class="sidebar-pretitle">Part of a series on</td></tr><tr><th class="sidebar-title-with-pretitle"><a href="/wiki/Physical_cosmology" title="Physical cosmology">Physical cosmology</a></th></tr><tr><td class="sidebar-image"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:WMAP_2012.png" class="mw-file-description"><img alt="Full-sky image derived from nine years' WMAP data" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/WMAP_2012.png/220px-WMAP_2012.png" decoding="async" width="220" height="110" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/WMAP_2012.png/330px-WMAP_2012.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/WMAP_2012.png/440px-WMAP_2012.png 2x" data-file-width="4096" data-file-height="2048" /></a></span></td></tr><tr><td class="sidebar-above" style="border:0;font-weight:normal; display:block;margin-bottom:0.4em;"> <ul><li><a href="/wiki/Big_Bang" title="Big Bang">Big Bang</a> <b>·</b> <a href="/wiki/Universe" title="Universe">Universe</a></li> <li><a href="/wiki/Age_of_the_universe" title="Age of the universe">Age of the universe</a></li> <li><a href="/wiki/Chronology_of_the_universe" title="Chronology of the universe">Chronology of the universe</a></li></ul></td></tr><tr><td class="sidebar-content-with-subgroup"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="background:#ddd8e7;text-align:center;;color: var(--color-base)">Early universe</div><div class="sidebar-list-content mw-collapsible-content"><table class="sidebar-subgroup"><tbody><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Cosmic_inflation" title="Cosmic inflation">Inflation</a> <b>·</b> <a href="/wiki/Big_Bang_nucleosynthesis" title="Big Bang nucleosynthesis">Nucleosynthesis</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="font-weight:normal;font-style:italic;"> Backgrounds</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Gravitational_wave_background" title="Gravitational wave background">Gravitational wave (GWB)</a></li> <li><a href="/wiki/Cosmic_microwave_background" title="Cosmic microwave background">Microwave (CMB)</a> <b>·</b> <a href="/wiki/Cosmic_neutrino_background" title="Cosmic neutrino background">Neutrino (CNB)</a></li></ul></td> </tr></tbody></table></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="background:#ddd8e7;text-align:center;;color: var(--color-base)">Expansion <b>·</b> Future</div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Hubble%27s_law" title="Hubble's law">Hubble's law</a> <b>·</b> <a href="/wiki/Redshift" title="Redshift">Redshift</a></li> <li><a href="/wiki/Expansion_of_the_universe" title="Expansion of the universe">Expansion of the universe</a></li> <li><a href="/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metric" title="Friedmann–Lemaître–Robertson–Walker metric">FLRW metric</a> <b>·</b> <a href="/wiki/Friedmann_equations" title="Friedmann equations">Friedmann equations</a></li> <li><a href="/wiki/Lambda-CDM_model" title="Lambda-CDM model">Lambda-CDM model</a></li> <li><a href="/wiki/Future_of_an_expanding_universe" title="Future of an expanding universe">Future of an expanding universe</a></li> <li><a href="/wiki/Ultimate_fate_of_the_universe" title="Ultimate fate of the universe">Ultimate fate of the universe</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content-with-subgroup"> <div class="sidebar-list mw-collapsible"><div class="sidebar-list-title" style="background:#ddd8e7;text-align:center;;color: var(--color-base)">Components <b>·</b> Structure</div><div class="sidebar-list-content mw-collapsible-content"><table class="sidebar-subgroup"><tbody><tr><th class="sidebar-heading" style="font-weight:normal;font-style:italic;"> Components</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Dark_energy" title="Dark energy">Dark energy</a> <b>·</b> <a href="/wiki/Dark_matter" title="Dark matter">Dark matter</a></li> <li><a href="/wiki/Photons" class="mw-redirect" title="Photons">Photons</a> <b>·</b> <a href="/wiki/Baryons" class="mw-redirect" title="Baryons">Baryons</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="font-weight:normal;font-style:italic;"> Structure</th></tr><tr><td class="sidebar-content"> <ul><li><a href="/wiki/Shape_of_the_universe" title="Shape of the universe">Shape of the universe</a></li> <li><a href="/wiki/Galaxy_filament" title="Galaxy filament">Galaxy filament</a> <b>·</b> <a href="/wiki/Galaxy_formation_and_evolution" title="Galaxy formation and evolution">Galaxy formation</a></li> <li><a href="/wiki/Large_quasar_group" title="Large quasar group">Large quasar group</a></li> <li><a class="mw-selflink-fragment" href="#Large-scale_structure">Large-scale structure</a></li> <li><a href="/wiki/Reionization" title="Reionization">Reionization</a> <b>·</b> <a href="/wiki/Structure_formation" title="Structure formation">Structure formation</a></li></ul></td> </tr></tbody></table></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="background:#ddd8e7;text-align:center;;color: var(--color-base)"><a href="/wiki/Observational_cosmology" title="Observational cosmology">Experiments</a></div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><a href="/wiki/Black_Hole_Initiative" title="Black Hole Initiative">Black Hole Initiative (BHI)</a></li> <li><a href="/wiki/BOOMERanG_experiment" title="BOOMERanG experiment">BOOMERanG</a></li> <li><a href="/wiki/Cosmic_Background_Explorer" title="Cosmic Background Explorer">Cosmic Background Explorer (COBE)</a></li> <li><a href="/wiki/Dark_Energy_Survey" title="Dark Energy Survey">Dark Energy Survey</a></li> <li><a href="/wiki/Planck_(spacecraft)" title="Planck (spacecraft)">Planck space observatory</a></li> <li><a href="/wiki/Sloan_Digital_Sky_Survey" title="Sloan Digital Sky Survey">Sloan Digital Sky Survey (SDSS)</a></li> <li><a href="/wiki/2dF_Galaxy_Redshift_Survey" title="2dF Galaxy Redshift Survey">2dF Galaxy Redshift Survey ("2dF")</a></li> <li><div style="display:inline-block; padding:0.2em 0.4em; line-height:1.2em;"><a href="/wiki/Wilkinson_Microwave_Anisotropy_Probe" title="Wilkinson Microwave Anisotropy Probe">Wilkinson Microwave Anisotropy<br />Probe (WMAP)</a></div></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="background:#ddd8e7;text-align:center;;color: var(--color-base)">Scientists</div><div class="sidebar-list-content mw-collapsible-content"><div class="hlist" style="padding:0 0.9em;"> <ul><li><a href="/wiki/Marc_Aaronson" title="Marc Aaronson">Aaronson</a></li> <li><a href="/wiki/Hannes_Alfv%C3%A9n" title="Hannes Alfvén">Alfvén</a></li> <li><a href="/wiki/Ralph_Alpher" title="Ralph Alpher">Alpher</a></li> <li><a href="/wiki/Nicolaus_Copernicus" title="Nicolaus Copernicus">Copernicus</a></li> <li><a href="/wiki/Willem_de_Sitter" title="Willem de Sitter">de Sitter</a></li> <li><a href="/wiki/Robert_H._Dicke" title="Robert H. Dicke">Dicke</a></li> <li><a href="/wiki/J%C3%BCrgen_Ehlers" title="Jürgen Ehlers">Ehlers</a></li> <li><a href="/wiki/Albert_Einstein" title="Albert Einstein">Einstein</a></li> <li><a href="/wiki/George_F._R._Ellis" title="George F. R. Ellis">Ellis</a></li> <li><a href="/wiki/Alexander_Friedmann" title="Alexander Friedmann">Friedmann</a></li> <li><a href="/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo</a></li> <li><a href="/wiki/George_Gamow" title="George Gamow">Gamow</a></li> <li><a href="/wiki/Alan_Guth" title="Alan Guth">Guth</a></li> <li><a href="/wiki/Stephen_Hawking" title="Stephen Hawking">Hawking</a></li> <li><a href="/wiki/Edwin_Hubble" title="Edwin Hubble">Hubble</a></li> <li><a href="/wiki/Christiaan_Huygens" title="Christiaan Huygens">Huygens</a></li> <li><a href="/wiki/Johannes_Kepler" title="Johannes Kepler">Kepler</a></li> <li><a href="/wiki/Georges_Lema%C3%AEtre" title="Georges Lemaître">Lemaître</a></li> <li><a href="/wiki/John_C._Mather" title="John C. Mather">Mather</a></li> <li><a href="/wiki/Isaac_Newton" title="Isaac Newton">Newton</a></li> <li><a href="/wiki/Roger_Penrose" title="Roger Penrose">Penrose</a></li> <li><a href="/wiki/Arno_Allan_Penzias" title="Arno Allan Penzias">Penzias</a></li> <li><a href="/wiki/Vera_Rubin" title="Vera Rubin">Rubin</a></li> <li><a href="/wiki/Brian_Schmidt" title="Brian Schmidt">Schmidt</a></li> <li><a href="/wiki/George_Smoot" title="George Smoot">Smoot</a></li> <li><a href="/wiki/Nicholas_B._Suntzeff" title="Nicholas B. Suntzeff">Suntzeff</a></li> <li><a href="/wiki/Rashid_Sunyaev" title="Rashid Sunyaev">Sunyaev</a></li> <li><a href="/wiki/Richard_C._Tolman" title="Richard C. Tolman">Tolman</a></li> <li><a href="/wiki/Robert_Woodrow_Wilson" title="Robert Woodrow Wilson">Wilson</a></li> <li><a href="/wiki/Yakov_Zeldovich" title="Yakov Zeldovich">Zeldovich</a></li></ul> </div> <ul><li><a href="/wiki/List_of_cosmologists" title="List of cosmologists">List of cosmologists</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="background:#ddd8e7;text-align:center;;color: var(--color-base)"><a href="/wiki/Physical_cosmology#Subject_history" title="Physical cosmology">Subject history</a></div><div class="sidebar-list-content mw-collapsible-content"> <ul><li><div style="display:inline-block; padding:0.2em 0.4em; line-height:1.2em;"><a href="/wiki/Discovery_of_cosmic_microwave_background_radiation" title="Discovery of cosmic microwave background radiation">Discovery of cosmic microwave<br />background radiation</a></div></li> <li><a href="/wiki/History_of_the_Big_Bang_theory" title="History of the Big Bang theory">History of the Big Bang theory</a></li> <li><a href="/wiki/Timeline_of_cosmological_theories" title="Timeline of cosmological theories">Timeline of cosmological theories</a></li></ul></div></div></td> </tr><tr><td class="sidebar-below" style="display:block;margin-top:0.4em; line-height:1.6em;padding-bottom:0.5em;"> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Physical_cosmology" title="Category:Physical cosmology">Category</a></li> <li><span class="nowrap"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/15px-Crab_Nebula.jpg" decoding="async" width="15" height="15" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/23px-Crab_Nebula.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/30px-Crab_Nebula.jpg 2x" data-file-width="3864" data-file-height="3864" /></span></span> </span><a href="/wiki/Portal:Astronomy" title="Portal:Astronomy">Astronomy portal</a></li></ul></td></tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Physical_cosmology" title="Template:Physical cosmology"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Physical_cosmology" title="Template talk:Physical cosmology"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Physical_cosmology" title="Special:EditPage/Template:Physical cosmology"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Home_in_Relation_to_Everything-Observable_Universe.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Home_in_Relation_to_Everything-Observable_Universe.png/350px-Home_in_Relation_to_Everything-Observable_Universe.png" decoding="async" width="350" height="360" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Home_in_Relation_to_Everything-Observable_Universe.png/525px-Home_in_Relation_to_Everything-Observable_Universe.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Home_in_Relation_to_Everything-Observable_Universe.png/700px-Home_in_Relation_to_Everything-Observable_Universe.png 2x" data-file-width="3002" data-file-height="3089" /></a><figcaption>Observable Universe as a function of time and distance, in context of the <a href="/wiki/Expanding_Universe" class="mw-redirect" title="Expanding Universe">expanding Universe</a></figcaption></figure> <p>The universe's size is unknown, and it may be infinite in extent.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Some parts of the universe are too far away for the light emitted since the <a href="/wiki/Big_Bang" title="Big Bang">Big Bang</a> to have had enough time to reach Earth or space-based instruments, and therefore lie outside the observable universe. In the future, light from distant galaxies will have had more time to travel, so one might expect that additional regions will become observable. Regions distant from observers (such as us) are expanding away faster than the speed of light, at rates estimated by <a href="/wiki/Hubble%27s_law" title="Hubble's law">Hubble's law</a>.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>note 3<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Accelerating_expansion_of_the_universe" title="Accelerating expansion of the universe">expansion rate appears to be accelerating</a>, which <a href="/wiki/Dark_energy" title="Dark energy">dark energy</a> was proposed to explain. </p><p>Assuming dark energy remains constant (an unchanging <a href="/wiki/Cosmological_constant" title="Cosmological constant">cosmological constant</a>) so that the expansion rate of the universe continues to accelerate, there is a "future visibility limit" beyond which objects will never enter the observable universe at any time in the future because light emitted by objects outside that limit could never reach the Earth. Note that, because the <a href="/wiki/Hubble%27s_law#Interpretation" title="Hubble's law">Hubble parameter</a> is decreasing with time, there can be cases where a galaxy that is receding from Earth only slightly faster than light emits a signal that eventually reaches Earth.<sup id="cite_ref-ly93_11-1" class="reference"><a href="#cite_note-ly93-11"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> This future visibility limit is calculated at a <a href="/wiki/Comoving_distance" class="mw-redirect" title="Comoving distance">comoving distance</a> of 19 billion parsecs (62 billion light-years), assuming the universe will keep expanding forever, which implies the number of galaxies that can ever be theoretically observed in the infinite future is only larger than the number currently observable by a factor of 2.36 (ignoring redshift effects).<sup id="cite_ref-mapofuniverse2_19-0" class="reference"><a href="#cite_note-mapofuniverse2-19"><span class="cite-bracket">[</span>note 4<span class="cite-bracket">]</span></a></sup> </p><p>In principle, more galaxies will become observable in the future; in practice, an increasing number of galaxies will become extremely <a href="/wiki/Redshift" title="Redshift">redshifted</a> due to ongoing expansion, so much so that they will seem to disappear from view and become invisible.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> A galaxy at a given comoving distance is defined to lie within the "observable universe" if we can receive signals emitted by the galaxy at any age in its history, say, a signal sent from the galaxy only 500 million years after the Big Bang. Because of the universe's expansion, there may be some later age at which a signal sent from the same galaxy can never reach the Earth at any point in the infinite future, so, for example, we might never see what the galaxy looked like 10 billion years after the Big Bang,<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> even though it remains at the same comoving distance less than that of the observable universe. </p><p>This can be used to define a type of cosmic <a href="/wiki/Event_horizon" title="Event horizon">event horizon</a> whose distance from the Earth changes over time. For example, the current distance to this horizon is about 16 billion light-years, meaning that a signal from an event happening at present can eventually reach the Earth if the event is less than 16 billion light-years away, but the signal will never reach the Earth if the event is further away.<sup id="cite_ref-ly93_11-2" class="reference"><a href="#cite_note-ly93-11"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p><p>The space before this cosmic event horizon can be called "reachable universe", that is all galaxies closer than that could be reached if we left for them today, at the speed of light; all galaxies beyond that are unreachable.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> Simple observation will show the future visibility limit (62 billion light-years) is exactly equal to the reachable limit (16 billion light-years) added to the current visibility limit (46 billion light-years).<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-mapofuniverse_9-1" class="reference"><a href="#cite_note-mapofuniverse-9"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Home_in_Relation_to_Everything-Reachable_Universe.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/88/Home_in_Relation_to_Everything-Reachable_Universe.png/350px-Home_in_Relation_to_Everything-Reachable_Universe.png" decoding="async" width="350" height="335" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/88/Home_in_Relation_to_Everything-Reachable_Universe.png/525px-Home_in_Relation_to_Everything-Reachable_Universe.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/88/Home_in_Relation_to_Everything-Reachable_Universe.png/700px-Home_in_Relation_to_Everything-Reachable_Universe.png 2x" data-file-width="3034" data-file-height="2907" /></a><figcaption>The reachable Universe as a function of time and distance, in context of the expanding Universe.</figcaption></figure> <div class="mw-heading mw-heading2"><h2 id=""The_universe"_versus_"the_observable_universe""><span id=".22The_universe.22_versus_.22the_observable_universe.22"></span>"The universe" versus "the observable universe"</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=2" title="Edit section: "The universe" versus "the observable universe""><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Both popular and professional research articles in cosmology often use the term "universe" to mean "observable universe".<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2015)">citation needed</span></a></i>]</sup> This can be justified on the grounds that we can never know anything by direct observation about any part of the universe that is <a href="/wiki/Causality_(physics)" title="Causality (physics)">causally disconnected</a> from the Earth, although many credible theories require a total universe much larger than the observable universe.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2015)">citation needed</span></a></i>]</sup> No evidence exists to suggest that the boundary of the observable universe constitutes a boundary on the universe as a whole, nor do any of the mainstream cosmological models propose that the universe has any physical boundary in the first place. However, some models propose it could be finite but unbounded,<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>note 5<span class="cite-bracket">]</span></a></sup> like a higher-dimensional analogue of the 2D surface of a sphere that is finite in area but has no edge. </p><p>It is plausible that the <a href="/wiki/Galaxy" title="Galaxy">galaxies</a> within the observable universe represent only a minuscule fraction of the galaxies in the universe. According to the theory of <a href="/wiki/Cosmic_inflation" title="Cosmic inflation">cosmic inflation</a> initially introduced by <a href="/wiki/Alan_Guth" title="Alan Guth">Alan Guth</a> and <a href="/w/index.php?title=D._Kazanas&action=edit&redlink=1" class="new" title="D. Kazanas (page does not exist)">D. Kazanas</a>,<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> if it is assumed that inflation began about 10<sup>−37</sup> seconds after the Big Bang and that the pre-inflation size of the universe was approximately equal to the speed of light times its age, that would suggest that at present the entire universe's size is at least <span class="nowrap"><span data-sort-value="7034149999999999999♠"></span>1.5<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>34</sup></span> light-years — this is at least <span class="nowrap"><span data-sort-value="7023300000000000000♠"></span>3<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>23</sup></span> times the radius of the observable universe.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>If the universe is finite but unbounded, it is also possible that the universe is <i>smaller</i> than the observable universe. In this case, what we take to be very distant galaxies may actually be duplicate images of nearby galaxies, formed by light that has circumnavigated the universe. It is difficult to test this hypothesis experimentally because different images of a galaxy would show different eras in its history, and consequently might appear quite different. Bielewicz et al.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> claim to establish a lower bound of 27.9 gigaparsecs (91 billion light-years) on the diameter of the last scattering surface. This value is based on matching-circle analysis of the <a href="/wiki/WMAP" class="mw-redirect" title="WMAP">WMAP</a> 7-year data. This approach has been disputed.<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Size">Size</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=3" title="Edit section: Size"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:HubbleUltraDeepFieldwithScaleComparison.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e4/HubbleUltraDeepFieldwithScaleComparison.jpg/350px-HubbleUltraDeepFieldwithScaleComparison.jpg" decoding="async" width="350" height="350" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e4/HubbleUltraDeepFieldwithScaleComparison.jpg/525px-HubbleUltraDeepFieldwithScaleComparison.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e4/HubbleUltraDeepFieldwithScaleComparison.jpg/700px-HubbleUltraDeepFieldwithScaleComparison.jpg 2x" data-file-width="3100" data-file-height="3100" /></a><figcaption><a href="/wiki/Hubble_Ultra-Deep_Field" title="Hubble Ultra-Deep Field">Hubble Ultra-Deep Field</a> image of a region of the observable universe (equivalent sky area size shown in bottom left corner), near the <a href="/wiki/Fornax" title="Fornax">constellation Fornax</a>. Each spot is a <a href="/wiki/Galaxy" title="Galaxy">galaxy</a>, consisting of billions of stars. The light from the smallest, most <a href="/wiki/Redshift" title="Redshift">redshifted</a> galaxies originated nearly <a href="/wiki/Age_of_the_universe" title="Age of the universe">13.8 billion years</a> ago.</figcaption></figure> <p>The <a href="/wiki/Comoving_and_proper_distances" title="Comoving and proper distances">comoving distance</a> from Earth to the edge of the observable universe is about 14.26 giga<a href="/wiki/Parsec" title="Parsec">parsecs</a> (46.5 <a href="/wiki/1000000000_(number)" class="mw-redirect" title="1000000000 (number)">billion</a> <a href="/wiki/Light-year" title="Light-year">light-years</a> or 4.40<span style="margin:0 .15em 0 .25em">×</span>10<sup>26</sup> m) in any direction. The observable universe is thus a sphere with a <a href="/wiki/Diameter" title="Diameter">diameter</a> of about 28.5 gigaparsecs<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> (93 billion light-years or 8.8<span style="margin:0 .15em 0 .25em">×</span>10<sup>26</sup> m).<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Assuming that space is roughly <a href="/wiki/Shape_of_the_universe#Universe_with_zero_curvature" title="Shape of the universe">flat</a> (in the sense of being a <a href="/wiki/Euclidean_space" title="Euclidean space">Euclidean space</a>), this size corresponds to a comoving volume of about <span class="nowrap"><span data-sort-value="7004122000000000000♠"></span>1.22<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>4</sup> Gpc<sup>3</sup></span> (<span class="nowrap"><span data-sort-value="7005422000000000000♠"></span>4.22<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>5</sup> Gly<sup>3</sup></span> or <span class="nowrap"><span data-sort-value="7080357000000000000♠"></span>3.57<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>80</sup> m<sup>3</sup></span>).<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>These are distances now (in <a href="/wiki/Cosmological_time" class="mw-redirect" title="Cosmological time">cosmological time</a>), not distances at the time the light was emitted. For example, the cosmic microwave background radiation that we see right now was emitted at the <a href="/wiki/Recombination_(cosmology)" title="Recombination (cosmology)">time of photon decoupling</a>, estimated to have occurred about <span class="nowrap"><span data-sort-value="7005380000000000000♠"></span>380,000</span> years after the Big Bang,<sup id="cite_ref-wmap7parameters_35-0" class="reference"><a href="#cite_note-wmap7parameters-35"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> which occurred around 13.8 billion years ago. This radiation was emitted by matter that has, in the intervening time, mostly condensed into galaxies, and those galaxies are now calculated to be about 46 billion light-years from Earth.<sup id="cite_ref-mapofuniverse_9-2" class="reference"><a href="#cite_note-mapofuniverse-9"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ly93_11-3" class="reference"><a href="#cite_note-ly93-11"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> To estimate the distance to that matter at the time the light was emitted, we may first note that according to the <a href="/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metric" title="Friedmann–Lemaître–Robertson–Walker metric">Friedmann–Lemaître–Robertson–Walker metric</a>, which is used to model the expanding universe, if we receive light with a <a href="/wiki/Redshift" title="Redshift">redshift</a> of <i>z</i>, then the <a href="/wiki/Scale_factor_(cosmology)" title="Scale factor (cosmology)">scale factor</a> at the time the light was originally emitted is given by<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p> <blockquote><p><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a(t)={\frac {1}{1+z}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>a</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mrow> <mn>1</mn> <mo>+</mo> <mi>z</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle a(t)={\frac {1}{1+z}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3fc50f64b94c0a8d7356a0726ca0a303db1c8b95" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:12.904ex; height:5.343ex;" alt="{\displaystyle a(t)={\frac {1}{1+z}}}" /></span>.</p></blockquote> <p><a href="/wiki/Wilkinson_Microwave_Anisotropy_Probe#Nine-year_data_release" title="Wilkinson Microwave Anisotropy Probe">WMAP nine-year results</a> combined with other measurements give the redshift of photon decoupling as <i>z</i> = <span class="nowrap"><span data-sort-value="7003109164000000000♠"></span>1<span style="margin-left:.25em;">091</span>.64<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.47</span>,<sup id="cite_ref-bennet-wmap9year-2012_39-0" class="reference"><a href="#cite_note-bennet-wmap9year-2012-39"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> which implies that the scale factor at the time of photon <a href="/wiki/Decoupling_(cosmology)" title="Decoupling (cosmology)">decoupling</a> would be <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">1</span>⁄<span class="den">1092.64</span></span>. So if the matter that originally emitted the oldest CMBR <a href="/wiki/Photon" title="Photon">photons</a> has a present distance of 46 billion light-years, then the distance would have been only about 42 million light-years at the time of decoupling. </p><p>The <a href="/wiki/Light-travel_distance" class="mw-redirect" title="Light-travel distance">light-travel distance</a> to the edge of the observable universe is the <a href="/wiki/Age_of_the_universe" title="Age of the universe">age of the universe</a> times the <a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a>, 13.8 billion light years. This is the distance that a photon emitted shortly after the Big Bang, such as one from the <a href="/wiki/Cosmic_microwave_background" title="Cosmic microwave background">cosmic microwave background</a>, has traveled to reach observers on Earth. Because <a href="/wiki/Spacetime" title="Spacetime">spacetime</a> is curved, corresponding to the <a href="/wiki/Expansion_of_the_universe" title="Expansion of the universe">expansion of space</a>, this distance does not correspond to the true distance at any moment in time.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Matter_and_mass">Matter and mass</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=4" title="Edit section: Matter and mass"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Number_of_galaxies_and_stars">Number of galaxies and stars</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=5" title="Edit section: Number of galaxies and stars"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The observable universe contains as many as an estimated 2 trillion galaxies<sup id="cite_ref-BBC-20231129_41-0" class="reference"><a href="#cite_note-BBC-20231129-41"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> and, overall, as many as an estimated 10<sup>24</sup> stars<sup id="cite_ref-ESA-2019_44-0" class="reference"><a href="#cite_note-ESA-2019-44"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> – more stars (and, potentially, Earth-like planets) than all the <a href="/wiki/Sand" title="Sand">grains of beach sand</a> on planet <a href="/wiki/Earth" title="Earth">Earth</a>.<sup id="cite_ref-SU-20020201_46-0" class="reference"><a href="#cite_note-SU-20020201-46"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-CNET-20150319_47-0" class="reference"><a href="#cite_note-CNET-20150319-47"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-MNRAS-20150313_48-0" class="reference"><a href="#cite_note-MNRAS-20150313-48"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> Other estimates are in the hundreds of billions rather than trillions.<sup id="cite_ref-:0_49-0" class="reference"><a href="#cite_note-:0-49"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ann21001_50-0" class="reference"><a href="#cite_note-ann21001-50"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arxiv:2011.03052_51-0" class="reference"><a href="#cite_note-arxiv:2011.03052-51"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> The estimated total number of stars in an <a href="/wiki/Cosmic_inflation" title="Cosmic inflation">inflationary universe</a> (observed and unobserved) is 10<sup>100</sup>.<sup id="cite_ref-SR-20200203_52-0" class="reference"><a href="#cite_note-SR-20200203-52"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Matter_content—number_of_atoms"><span id="Matter_content.E2.80.94number_of_atoms"></span><span class="anchor" id="Matter_content"></span> Matter content—number of atoms</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=6" title="Edit section: Matter content—number of atoms"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Abundance_of_the_chemical_elements" title="Abundance of the chemical elements">Abundance of the chemical elements</a></div> <p>Assuming the mass of ordinary matter is about <span class="nowrap"><span data-sort-value="7053144999999999999♠"></span>1.45<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>53</sup> kg</span> as discussed above, and assuming all atoms are <a href="/wiki/Hydrogen_atom" title="Hydrogen atom">hydrogen atoms</a> (which are about 74% of all atoms in the Milky Way by mass), the estimated total number of atoms in the observable universe is obtained by dividing the mass of ordinary matter by the mass of a hydrogen atom. The result is approximately 10<sup>80</sup> hydrogen atoms, also known as the <a href="/wiki/Eddington_number" title="Eddington number">Eddington number</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Mass_of_ordinary_matter">Mass of ordinary matter</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=7" title="Edit section: Mass of ordinary matter"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The mass of the observable universe is often quoted as 10<sup>53</sup> kg.<sup id="cite_ref-Paul_Davies_2006_43_53-0" class="reference"><a href="#cite_note-Paul_Davies_2006_43-53"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> In this context, mass refers to ordinary (baryonic) matter and includes the <a href="/wiki/Interstellar_medium" title="Interstellar medium">interstellar medium</a> (ISM) and the <a href="/wiki/Intergalactic_medium" class="mw-redirect" title="Intergalactic medium">intergalactic medium</a> (IGM). However, it excludes <a href="/wiki/Dark_matter" title="Dark matter">dark matter</a> and <a href="/wiki/Dark_energy" title="Dark energy">dark energy</a>. This quoted value for the mass of ordinary matter in the universe can be estimated based on critical density. The calculations are for the observable universe only as the volume of the whole is unknown and may be infinite. </p> <div class="mw-heading mw-heading3"><h3 id="Estimates_based_on_critical_density">Estimates based on critical density</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=8" title="Edit section: Estimates based on critical density"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Critical density is the energy density for which the universe is flat.<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> If there is no dark energy, it is also the <a href="/wiki/Density" title="Density">density</a> for which the expansion of the universe is poised between continued expansion and collapse.<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> From the <a href="/wiki/Friedmann_equations" title="Friedmann equations">Friedmann equations</a>, the value for <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \rho _{\text{c}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ρ</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>c</mtext> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \rho _{\text{c}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eb5e0129465414c2e5fbbb5ca317fcee3678c277" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:2.164ex; height:2.176ex;" alt="{\displaystyle \rho _{\text{c}}}" /></span> critical density, is:<sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \rho _{\text{c}}={\frac {3H^{2}}{8\pi G}},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>ρ</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>c</mtext> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>3</mn> <msup> <mi>H</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> <mrow> <mn>8</mn> <mi>π</mi> <mi>G</mi> </mrow> </mfrac> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \rho _{\text{c}}={\frac {3H^{2}}{8\pi G}},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/844811610634c6446119c46172f0302e06f7d493" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:11.067ex; height:5.843ex;" alt="{\displaystyle \rho _{\text{c}}={\frac {3H^{2}}{8\pi G}},}" /></span></dd></dl> <p>where <i>G</i> is the <a href="/wiki/Gravitational_constant" title="Gravitational constant">gravitational constant</a> and <span class="nowrap"><i>H</i> = <i>H</i><sub>0</sub></span> is the present value of the <a href="/wiki/Hubble_constant" class="mw-redirect" title="Hubble constant">Hubble constant</a>. The value for <i>H</i><sub>0</sub>, as given by the European Space Agency's Planck Telescope, is <i>H</i><sub>0</sub> = 67.15 kilometres per second per megaparsec. This gives a critical density of <span class="nowrap"><span data-sort-value="6973850000000000000♠"></span>0.85<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−26</sup> kg/m<sup>3</sup></span>, or about 5 hydrogen atoms per cubic metre. This density includes four significant types of energy/mass: ordinary matter (4.8%), neutrinos (0.1%), <a href="/wiki/Cold_dark_matter" title="Cold dark matter">cold dark matter</a> (26.8%), and <a href="/wiki/Dark_energy" title="Dark energy">dark energy</a> (68.3%).<sup id="cite_ref-planck_cosmological_parameters_57-0" class="reference"><a href="#cite_note-planck_cosmological_parameters-57"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> </p><p>Although neutrinos are <a href="/wiki/Standard_Model" title="Standard Model">Standard Model</a> particles, they are listed separately because they are <a href="/wiki/Scale_factor_(cosmology)#Radiation-dominated_era" title="Scale factor (cosmology)">ultra-relativistic</a> and hence <a href="/wiki/Equation_of_state_(cosmology)#Ultra-relativistic_particles" title="Equation of state (cosmology)">behave</a> like radiation rather than like matter. The density of ordinary matter, as measured by Planck, is 4.8% of the total critical density or <span class="nowrap"><span data-sort-value="6972408000000000000♠"></span>4.08<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−28</sup> kg/m<sup>3</sup></span>. To convert this density to mass we must multiply by volume, a value based on the radius of the "observable universe". Since the universe has been expanding for 13.8 billion years, the <a href="/wiki/Comoving_and_proper_distances" title="Comoving and proper distances">comoving distance</a> (radius) is now about 46.6 billion light-years. Thus, volume (<style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">4</span><span class="sr-only">/</span><span class="den">3</span></span>⁠</span><i>πr</i><sup>3</sup>) equals <span class="nowrap"><span data-sort-value="7080358000000000000♠"></span>3.58<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>80</sup> m<sup>3</sup></span> and the mass of ordinary matter equals density (<span class="nowrap"><span data-sort-value="6972408000000000000♠"></span>4.08<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−28</sup> kg/m<sup>3</sup></span>) times volume (<span class="nowrap"><span data-sort-value="7080358000000000000♠"></span>3.58<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>80</sup> m<sup>3</sup></span>) or <span class="nowrap"><span data-sort-value="7053146000000000000♠"></span>1.46<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>53</sup> kg</span>. </p> <div class="mw-heading mw-heading2"><h2 id="Large-scale_structure">Large-scale structure</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=9" title="Edit section: Large-scale structure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/16/Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg/220px-Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg" decoding="async" width="220" height="211" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/16/Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg/330px-Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/16/Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg/440px-Galactic_treasure_chest_RXC_J0142.9%2B4438.jpg 2x" data-file-width="6374" data-file-height="6113" /></a><figcaption>Galaxy clusters, like <a href="/w/index.php?title=RXC_J0142.9%2B4438&action=edit&redlink=1" class="new" title="RXC J0142.9+4438 (page does not exist)">RXC J0142.9+4438</a>, are the nodes of the cosmic web that permeates the entire Universe.<sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><span><video id="mwe_player_0" poster="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/400px--Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.jpg" controls="" preload="none" data-mw-tmh="" class="mw-file-element" width="400" height="400" data-durationhint="147" data-mwtitle="Constrained_Local_Universe_Evolution_Simulation_(spherical).webm" data-mwprovider="wikimediacommons" resource="/wiki/File:Constrained_Local_Universe_Evolution_Simulation_(spherical).webm"><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.480p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="480p.vp9.webm" data-width="480" data-height="480" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.720p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="720p.vp9.webm" data-width="720" data-height="720" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.1080p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="1080p.vp9.webm" data-width="1080" data-height="1080" /><source src="//upload.wikimedia.org/wikipedia/commons/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm" type="video/webm; codecs="vp9"" data-width="4096" data-height="4096" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.144p.mjpeg.mov" type="video/quicktime" data-transcodekey="144p.mjpeg.mov" data-width="144" data-height="144" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.240p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="240p.vp9.webm" data-width="240" data-height="240" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.360p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="360p.vp9.webm" data-width="360" data-height="360" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/2/2d/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm/Constrained_Local_Universe_Evolution_Simulation_%28spherical%29.webm.360p.webm" type="video/webm; codecs="vp8, vorbis"" data-transcodekey="360p.webm" data-width="360" data-height="360" /></video></span><figcaption>Video of a <a href="/wiki/Cosmology" title="Cosmology">cosmological</a> <a href="/wiki/Computer_simulation" title="Computer simulation">simulation</a> of the local universe, showing large-scale structure of clusters of galaxies and dark matter<sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup></figcaption></figure><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/List_of_largest_cosmic_structures" title="List of largest cosmic structures">List of largest cosmic structures</a></div> <p><a href="/wiki/Redshift_survey" title="Redshift survey">Sky surveys</a> and mappings of the various <a href="/wiki/Wavelength" title="Wavelength">wavelength</a> bands of <a href="/wiki/Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic radiation</a> (in particular <a href="/wiki/Hydrogen_line" title="Hydrogen line">21-cm emission</a>) have yielded much information on the content and character of the <a href="/wiki/Universe" title="Universe">universe</a>'s structure. The organization of structure appears to follow a <a href="/wiki/Hierarchy" title="Hierarchy">hierarchical</a> model with organization up to the <a href="/wiki/Scale_(spatial)" class="mw-redirect" title="Scale (spatial)">scale</a> of <a href="/wiki/Supercluster" title="Supercluster">superclusters</a> and <a href="/wiki/Galaxy_filament" title="Galaxy filament">filaments</a>. Larger than this (at scales between 30 and 200 megaparsecs),<sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> there seems to be no continued structure, a phenomenon that has been referred to as the <i>End of Greatness</i>.<sup id="cite_ref-Kirshner_61-0" class="reference"><a href="#cite_note-Kirshner-61"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> The shape of the large scale structure can be summarized by the <a href="/wiki/Matter_power_spectrum" title="Matter power spectrum">matter power spectrum</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Cosmic_Web:_walls,_filaments,_nodes,_and_voids"><span id="Cosmic_Web:_walls.2C_filaments.2C_nodes.2C_and_voids"></span>Cosmic Web: walls, filaments, nodes, and voids</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=10" title="Edit section: Cosmic Web: walls, filaments, nodes, and voids"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/26/Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg/400px-Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg" decoding="async" width="400" height="288" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/26/Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg/600px-Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/26/Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg/800px-Map_of_the_Cosmic_Web_Generated_from_Slime_Mould_Algorithm.jpg 2x" data-file-width="1280" data-file-height="920" /></a><figcaption>Map of the cosmic web generated from a slime mould-inspired algorithm<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup></figcaption></figure> <p>The organization of structure arguably begins at the stellar level, though most cosmologists rarely address <a href="/wiki/Astrophysics" title="Astrophysics">astrophysics</a> on that scale. <a href="/wiki/Star" title="Star">Stars</a> are organized into <a href="/wiki/Galaxy" title="Galaxy">galaxies</a>, which in turn form <a href="/wiki/Galaxy_group" title="Galaxy group">galaxy groups</a>, <a href="/wiki/Galaxy_cluster" title="Galaxy cluster">galaxy clusters</a>, <a href="/wiki/Supercluster" title="Supercluster">superclusters</a>, sheets, <a href="/wiki/Galaxy_filament" title="Galaxy filament">walls and filaments</a>, which are separated by immense <a href="/wiki/Void_(astronomy)" title="Void (astronomy)">voids</a>, creating a vast foam-like structure<sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup> sometimes called the "cosmic web". Prior to 1989, it was commonly assumed that <a href="/wiki/Virial_theorem" title="Virial theorem">virialized</a> galaxy clusters were the largest structures in existence, and that they were distributed more or less uniformly throughout the universe in every direction. However, since the early 1980s, more and more structures have been discovered. In 1983, Adrian Webster identified the <a href="/wiki/Webster_LQG" class="mw-redirect" title="Webster LQG">Webster LQG</a>, a <a href="/wiki/Large_quasar_group" title="Large quasar group">large quasar group</a> consisting of 5 quasars. The discovery was the first identification of a large-scale structure, and has expanded the information about the known grouping of matter in the universe. </p><p>In 1987, <a href="/wiki/R._Brent_Tully" title="R. Brent Tully">Robert Brent Tully</a> identified the <a href="/wiki/Pisces%E2%80%93Cetus_Supercluster_Complex" title="Pisces–Cetus Supercluster Complex">Pisces–Cetus Supercluster Complex</a>, the galaxy filament in which the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> resides. It is about 1 billion light-years across. That same year, an unusually large region with a much lower than average distribution of galaxies was discovered, the <a href="/wiki/Giant_Void" title="Giant Void">Giant Void</a>, which measures 1.3 billion light-years across. Based on <a href="/wiki/Redshift_survey" title="Redshift survey">redshift survey</a> data, in 1989 <a href="/wiki/Margaret_Geller" title="Margaret Geller">Margaret Geller</a> and <a href="/wiki/John_Huchra" title="John Huchra">John Huchra</a> discovered the "<a href="/wiki/CfA2_Great_Wall" title="CfA2 Great Wall">Great Wall</a>",<sup id="cite_ref-redshift_64-0" class="reference"><a href="#cite_note-redshift-64"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> a sheet of galaxies more than 500 million <a href="/wiki/Light-year" title="Light-year">light-years</a> long and 200 million light-years wide, but only 15 million light-years thick. The existence of this structure escaped notice for so long because it requires locating the position of galaxies in three dimensions, which involves combining location information about the galaxies with distance information from <a href="/wiki/Redshift" title="Redshift">redshifts</a>. </p><p>Two years later, astronomers Roger G. Clowes and Luis E. Campusano discovered the <a href="/wiki/Clowes%E2%80%93Campusano_LQG" title="Clowes–Campusano LQG">Clowes–Campusano LQG</a>, a <a href="/wiki/Large_quasar_group" title="Large quasar group">large quasar group</a> measuring two billion light-years at its widest point, which was the largest known structure in the universe at the time of its announcement. In April 2003, another large-scale structure was discovered, the <a href="/wiki/Sloan_Great_Wall" title="Sloan Great Wall">Sloan Great Wall</a>. In August 2007, a possible supervoid was detected in the constellation <a href="/wiki/Eridanus_(constellation)" title="Eridanus (constellation)">Eridanus</a>.<sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> It coincides with the '<a href="/wiki/CMB_cold_spot" title="CMB cold spot">CMB cold spot</a>', a cold region in the microwave sky that is highly improbable under the currently favored cosmological model. This supervoid could cause the cold spot, but to do so it would have to be improbably big, possibly a billion light-years across, almost as big as the Giant Void mentioned above. </p> <style data-mw-deduplicate="TemplateStyles:r1233989161">.mw-parser-output .unsolved{margin:0.5em 0 1em 1em;border:#ccc solid;padding:0.35em 0.35em 0.35em 2.2em;background-color:var(--background-color-interactive-subtle);background-image:url("https://upload.wikimedia.org/wikipedia/commons/2/26/Question%2C_Web_Fundamentals.svg");background-position:top 50%left 0.35em;background-size:1.5em;background-repeat:no-repeat}@media(min-width:720px){.mw-parser-output .unsolved{clear:right;float:right;max-width:25%}}.mw-parser-output .unsolved-label{font-weight:bold}.mw-parser-output .unsolved-body{margin:0.35em;font-style:italic}.mw-parser-output .unsolved-more{font-size:smaller}</style> <div role="note" aria-labelledby="unsolved-label-physics" class="unsolved"> <div><span class="unsolved-label" id="unsolved-label-physics">Unsolved problem in physics</span>:</div> <div class="unsolved-body">The largest structures in the universe are larger than expected. Are these actual structures or random density fluctuations?</div> <div class="unsolved-more"><a href="/wiki/List_of_unsolved_problems_in_physics" title="List of unsolved problems in physics">(more unsolved problems in physics)</a></div> </div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Large-scale_structure_of_light_distribution_in_the_universe.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Large-scale_structure_of_light_distribution_in_the_universe.jpg/440px-Large-scale_structure_of_light_distribution_in_the_universe.jpg" decoding="async" width="440" height="320" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Large-scale_structure_of_light_distribution_in_the_universe.jpg/660px-Large-scale_structure_of_light_distribution_in_the_universe.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Large-scale_structure_of_light_distribution_in_the_universe.jpg/880px-Large-scale_structure_of_light_distribution_in_the_universe.jpg 2x" data-file-width="4822" data-file-height="3511" /></a><figcaption>Computer simulated image of an area of space more than 50 million light-years across, presenting a possible large-scale distribution of light sources in the universe—precise relative contributions of galaxies and <a href="/wiki/Quasar" title="Quasar">quasars</a> are unclear.</figcaption></figure> <p>Another large-scale structure is the <a href="/wiki/SSA22_Protocluster" title="SSA22 Protocluster">SSA22 Protocluster</a>, a collection of galaxies and enormous gas bubbles that measures about 200 million light-years across. </p><p>In 2011, a large quasar group was discovered, <a href="/wiki/U1.11" title="U1.11">U1.11</a>, measuring about 2.5 billion light-years across. On January 11, 2013, another large quasar group, the <a href="/wiki/Huge-LQG" title="Huge-LQG">Huge-LQG</a>, was discovered, which was measured to be four billion light-years across, the largest known structure in the universe at that time.<sup id="cite_ref-66" class="reference"><a href="#cite_note-66"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> In November 2013, astronomers discovered the <a href="/wiki/Hercules%E2%80%93Corona_Borealis_Great_Wall" title="Hercules–Corona Borealis Great Wall">Hercules–Corona Borealis Great Wall</a>,<sup id="cite_ref-2014paper_67-0" class="reference"><a href="#cite_note-2014paper-67"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-original_68-0" class="reference"><a href="#cite_note-original-68"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup> an even bigger structure twice as large as the former. It was defined by the mapping of <a href="/wiki/Gamma-ray_burst" title="Gamma-ray burst">gamma-ray bursts</a>.<sup id="cite_ref-2014paper_67-1" class="reference"><a href="#cite_note-2014paper-67"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-69" class="reference"><a href="#cite_note-69"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup> </p><p>In 2021, the <a href="/wiki/American_Astronomical_Society" title="American Astronomical Society">American Astronomical Society</a> announced the detection of the <a href="/wiki/The_Giant_Arc" class="mw-redirect" title="The Giant Arc">Giant Arc</a>; a crescent-shaped string of galaxies that span 3.3 billion light years in length, located 9.2 billion light years from Earth in the constellation <a href="/wiki/Bo%C3%B6tes" title="Boötes">Boötes</a> from observations captured by the <a href="/wiki/Sloan_Digital_Sky_Survey" title="Sloan Digital Sky Survey">Sloan Digital Sky Survey</a>.<sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="End_of_Greatness">End of Greatness</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=11" title="Edit section: End of Greatness"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <i>End of Greatness</i> is an observational scale discovered at roughly 100 <a href="/wiki/Megaparsec" class="mw-redirect" title="Megaparsec">Mpc</a> (roughly 300 million light-years) where the lumpiness seen in the large-scale structure of the <a href="/wiki/Universe" title="Universe">universe</a> is <a href="https://en.wiktionary.org/wiki/homogeneous" class="extiw" title="wikt:homogeneous">homogenized</a> and <a href="/wiki/Isotropic" class="mw-redirect" title="Isotropic">isotropized</a> in accordance with the <a href="/wiki/Cosmological_principle" title="Cosmological principle">cosmological principle</a>.<sup id="cite_ref-Kirshner_61-1" class="reference"><a href="#cite_note-Kirshner-61"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> At this scale, no pseudo-random <a href="/wiki/Fractal" title="Fractal">fractalness</a> is apparent.<sup id="cite_ref-71" class="reference"><a href="#cite_note-71"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Supercluster" title="Supercluster">superclusters</a> and <a href="/wiki/Galaxy_filament" title="Galaxy filament">filaments</a> seen in smaller surveys are <a href="/wiki/Random" class="mw-redirect" title="Random">randomized</a> to the extent that the smooth distribution of the universe is visually apparent. It was not until the <a href="/wiki/Redshift_survey" title="Redshift survey">redshift surveys</a> of the 1990s were completed that this scale could accurately be observed.<sup id="cite_ref-Kirshner_61-2" class="reference"><a href="#cite_note-Kirshner-61"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Observations">Observations</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=12" title="Edit section: Observations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:2MASS_LSS_chart-NEW_Nasa.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/2MASS_LSS_chart-NEW_Nasa.jpg/550px-2MASS_LSS_chart-NEW_Nasa.jpg" decoding="async" width="550" height="278" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/2MASS_LSS_chart-NEW_Nasa.jpg/825px-2MASS_LSS_chart-NEW_Nasa.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7d/2MASS_LSS_chart-NEW_Nasa.jpg/1100px-2MASS_LSS_chart-NEW_Nasa.jpg 2x" data-file-width="1239" data-file-height="627" /></a><figcaption>"Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a>. The image is derived from the <a href="/wiki/2MASS" title="2MASS">2MASS Extended Source Catalog (XSC)</a>—more than 1.5 million galaxies, and the Point Source Catalog (PSC)—nearly 0.5 billion Milky Way stars. The galaxies are color-coded by '<a href="/wiki/Redshift" title="Redshift">redshift</a>' obtained from the <a href="/wiki/Uppsala_General_Catalogue" title="Uppsala General Catalogue">UGC</a>, <a href="/wiki/Harvard-Smithsonian_Center_for_Astrophysics" class="mw-redirect" title="Harvard-Smithsonian Center for Astrophysics">CfA</a>, Tully NBGC, LCRS, <a href="/wiki/2dF_Galaxy_Redshift_Survey" title="2dF Galaxy Redshift Survey">2dF</a>, 6dFGS, and <a href="/wiki/Sloan_Digital_Sky_Survey" title="Sloan Digital Sky Survey">SDSS</a> surveys (and from various observations compiled by the <a href="/wiki/NASA/IPAC_Extragalactic_Database" title="NASA/IPAC Extragalactic Database">NASA Extragalactic Database</a>), or photo-metrically deduced from the <a href="/wiki/K_band_(infrared)" title="K band (infrared)">K band</a> (2.2 μm). Blue are the nearest sources (<span class="nowrap"><i>z</i> < 0.01</span>); green are at moderate distances (<span class="nowrap">0.01 < <i>z</i> < 0.04</span>) and red are the most distant sources that 2MASS resolves (<span class="nowrap">0.04 < <i>z</i> < 0.1</span>). The map is projected with an equal area Aitoff in the Galactic system (Milky Way at center)."<sup id="cite_ref-72" class="reference"><a href="#cite_note-72"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Galactic%2Bcelestial_quads.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/74/Galactic%2Bcelestial_quads.jpg/550px-Galactic%2Bcelestial_quads.jpg" decoding="async" width="550" height="324" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/74/Galactic%2Bcelestial_quads.jpg/825px-Galactic%2Bcelestial_quads.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/74/Galactic%2Bcelestial_quads.jpg/1100px-Galactic%2Bcelestial_quads.jpg 2x" data-file-width="11530" data-file-height="6785" /></a><figcaption>Constellations grouped in galactic quadrants (N/S, 1–4) and their approximate divisions vis-a-vis celestial quadrants (NQ/SQ)</figcaption></figure> <p>Another indicator of large-scale structure is the '<a href="/wiki/Lyman-alpha_forest" title="Lyman-alpha forest">Lyman-alpha forest</a>'. This is a collection of <a href="/wiki/Spectral_line" title="Spectral line">absorption lines</a> that appear in the spectra of light from <a href="/wiki/Quasar" title="Quasar">quasars</a>, which are interpreted as indicating the existence of huge thin sheets of intergalactic (mostly <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a>) gas. These sheets appear to collapse into filaments, which can feed galaxies as they grow where filaments either cross or are dense. An early direct evidence for this cosmic web of gas was the 2019 detection, by astronomers from the RIKEN Cluster for Pioneering Research in Japan and Durham University in the U.K., of light from the brightest part of this web, surrounding and illuminated by a cluster of forming galaxies, acting as cosmic flashlights for intercluster medium hydrogen fluorescence via Lyman-alpha emissions.<sup id="cite_ref-73" class="reference"><a href="#cite_note-73"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-74" class="reference"><a href="#cite_note-74"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> </p><p>In 2021, an international team, headed by Roland Bacon from the Centre de Recherche Astrophysique de Lyon (France), reported the first observation of diffuse extended Lyman-alpha emission from redshift 3.1 to 4.5 that traced several cosmic web filaments on scales of 2.5−4 <a href="/w/index.php?title=CMpc&action=edit&redlink=1" class="new" title="CMpc (page does not exist)">cMpc</a> (comoving mega-parsecs), in filamentary environments outside massive structures typical of web nodes.<sup id="cite_ref-75" class="reference"><a href="#cite_note-75"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> </p><p>Some caution is required in describing structures on a cosmic scale because they are often different from how they appear. <a href="/wiki/Gravitational_lens" title="Gravitational lens">Gravitational lensing</a> can make an image appear to originate in a different direction from its real source, when foreground objects curve surrounding spacetime (as predicted by <a href="/wiki/General_relativity" title="General relativity">general relativity</a>) and deflect passing light rays. Rather usefully, strong gravitational lensing can sometimes magnify distant galaxies, making them easier to detect. <a href="/wiki/Weak_gravitational_lensing" title="Weak gravitational lensing">Weak lensing</a> by the intervening universe in general also subtly changes the observed large-scale structure. </p><p>The large-scale structure of the universe also looks different if only redshift is used to measure distances to galaxies. For example, galaxies behind a galaxy cluster are attracted to it and fall towards it, and so are <a href="/wiki/Blueshift" class="mw-redirect" title="Blueshift">blueshifted</a> (compared to how they would be if there were no cluster). On the near side, objects are redshifted. Thus, the environment of the cluster looks somewhat pinched if using redshifts to measure distance. The opposite effect is observed on galaxies already within a cluster: the galaxies have some random motion around the cluster center, and when these random motions are converted to redshifts, the cluster appears elongated. This creates a "<i><a href="/wiki/Redshift-space_distortions" title="Redshift-space distortions">finger of God</a></i>"—the illusion of a long chain of galaxies pointed at Earth. </p> <div class="mw-heading mw-heading3"><h3 id="Cosmography_of_Earth's_cosmic_neighborhood"><span id="Cosmography_of_Earth.27s_cosmic_neighborhood"></span>Cosmography of Earth's cosmic neighborhood</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=13" title="Edit section: Cosmography of Earth's cosmic neighborhood"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>At the centre of the <a href="/wiki/Hydra%E2%80%93Centaurus_Supercluster" title="Hydra–Centaurus Supercluster">Hydra–Centaurus Supercluster</a>, a gravitational anomaly called the <a href="/wiki/Great_Attractor" title="Great Attractor">Great Attractor</a> affects the motion of galaxies over a region hundreds of millions of light-years across. These galaxies are all <a href="/wiki/Redshift" title="Redshift">redshifted</a>, in accordance with <a href="/wiki/Hubble%27s_law" title="Hubble's law">Hubble's law</a>. This indicates that they are receding from us and from each other, but the variations in their redshift are sufficient to reveal the existence of a concentration of mass equivalent to tens of thousands of galaxies. </p><p>The Great Attractor, discovered in 1986, lies at a distance of between 150 million and 250 million light-years in the direction of the <a href="/wiki/Hydra_(constellation)" title="Hydra (constellation)">Hydra</a> and <a href="/wiki/Centaurus" title="Centaurus">Centaurus</a> <a href="/wiki/Constellation" title="Constellation">constellations</a>. In its vicinity there is a preponderance of large old galaxies, many of which are colliding with their neighbours, or radiating large amounts of radio waves. </p><p>In 1987, <a href="/wiki/Astronomer" title="Astronomer">astronomer</a> <a href="/wiki/R._Brent_Tully" title="R. Brent Tully">R. Brent Tully</a> of the <a href="/wiki/University_of_Hawaii" class="mw-redirect" title="University of Hawaii">University of Hawaii</a>'s Institute of Astronomy identified what he called the <a href="/wiki/Pisces%E2%80%93Cetus_Supercluster_Complex" title="Pisces–Cetus Supercluster Complex">Pisces–Cetus Supercluster Complex</a>, a structure one billion <a href="/wiki/Light-year" title="Light-year">light-years</a> long and 150 million light-years across in which, he claimed, the Local Supercluster is embedded.<sup id="cite_ref-76" class="reference"><a href="#cite_note-76"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Most_distant_objects">Most distant objects</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=14" title="Edit section: Most distant objects"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/List_of_the_most_distant_astronomical_objects" title="List of the most distant astronomical objects">List of the most distant astronomical objects</a></div> <p>The most distant <a href="/wiki/Astronomical_object" title="Astronomical object">astronomical object</a> identified (as of August of 2024) is a galaxy classified as <a href="/wiki/JADES-GS-z14-0" title="JADES-GS-z14-0">JADES-GS-z14-0</a>.<sup id="cite_ref-77" class="reference"><a href="#cite_note-77"><span class="cite-bracket">[</span>72<span class="cite-bracket">]</span></a></sup> In 2009, a <a href="/wiki/Gamma_ray_burst" class="mw-redirect" title="Gamma ray burst">gamma ray burst</a>, <a href="/wiki/GRB_090423" title="GRB 090423">GRB 090423</a>, was found to have a <a href="/wiki/Redshift" title="Redshift">redshift</a> of 8.2, which indicates that the collapsing star that caused it exploded when the universe was only 630 million years old.<sup id="cite_ref-NASAGRB_78-0" class="reference"><a href="#cite_note-NASAGRB-78"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> The burst happened approximately 13 billion years ago,<sup id="cite_ref-79" class="reference"><a href="#cite_note-79"><span class="cite-bracket">[</span>74<span class="cite-bracket">]</span></a></sup> so a distance of about 13 billion light-years was widely quoted in the media, or sometimes a more precise figure of 13.035 billion light-years.<sup id="cite_ref-NASAGRB_78-1" class="reference"><a href="#cite_note-NASAGRB-78"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> </p><p>This would be the "light travel distance" (see <a href="/wiki/Distance_measures_(cosmology)" class="mw-redirect" title="Distance measures (cosmology)">Distance measures (cosmology)</a>) rather than the "<a href="/wiki/Comoving_and_proper_distances#Uses_of_the_proper_distance" title="Comoving and proper distances">proper distance</a>" used in both <a href="/wiki/Hubble%27s_law" title="Hubble's law">Hubble's law</a> and in defining the size of the observable universe. Cosmologist <a href="/wiki/Edward_L._Wright" title="Edward L. Wright">Ned Wright</a> argues against using this measure.<sup id="cite_ref-80" class="reference"><a href="#cite_note-80"><span class="cite-bracket">[</span>75<span class="cite-bracket">]</span></a></sup> The proper distance for a redshift of 8.2 would be about 9.2 <a href="/wiki/Megaparsecs" class="mw-redirect" title="Megaparsecs">Gpc</a>,<sup id="cite_ref-81" class="reference"><a href="#cite_note-81"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup> or about 30 billion light-years. </p> <div class="mw-heading mw-heading2"><h2 id="Horizons">Horizons</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=15" title="Edit section: Horizons"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Cosmological_horizon" title="Cosmological horizon">Cosmological horizon</a></div> <p>The limit of observability in the universe is set by cosmological horizons which limit—based on various physical constraints—the extent to which information can be obtained about various events in the universe. The most famous horizon is the <a href="/wiki/Particle_horizon" title="Particle horizon">particle horizon</a> which sets a limit on the precise distance that can be seen due to the finite <a href="/wiki/Age_of_the_universe" title="Age of the universe">age of the universe</a>. Additional horizons are associated with the possible future extent of observations, larger than the particle horizon owing to the <a href="/wiki/Expansion_of_space" class="mw-redirect" title="Expansion of space">expansion of space</a>, an "optical horizon" at the <a href="/wiki/Cosmic_microwave_background" title="Cosmic microwave background">surface of last scattering</a>, and associated horizons with the surface of last scattering for <a href="/wiki/Cosmic_neutrino_background" title="Cosmic neutrino background">neutrinos</a> and <a href="/wiki/Gravitational_wave_background" title="Gravitational wave background">gravitational waves</a>. </p> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tnone center"><div class="thumbinner multiimageinner" style="width:885px;max-width:885px"><div class="trow"><div class="theader" style="text-align:center"><a href="/wiki/Location_of_Earth" title="Location of Earth">Location of Earth</a> in the <a href="/wiki/Universe" title="Universe">Universe</a></div></div><div class="trow"><div class="tsingle" style="width:84px;max-width:84px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:The_Earth_seen_from_Apollo_17.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/82px-The_Earth_seen_from_Apollo_17.jpg" decoding="async" width="82" height="82" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/123px-The_Earth_seen_from_Apollo_17.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/164px-The_Earth_seen_from_Apollo_17.jpg 2x" data-file-width="3000" data-file-height="3002" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Earth" title="Earth">Earth</a></div></div><div class="tsingle" style="width:148px;max-width:148px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Solar_System_true_color.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/19/Solar_System_true_color.jpg/146px-Solar_System_true_color.jpg" decoding="async" width="146" height="82" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/19/Solar_System_true_color.jpg/219px-Solar_System_true_color.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/19/Solar_System_true_color.jpg/292px-Solar_System_true_color.jpg 2x" data-file-width="3840" data-file-height="2160" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Solar_System" title="Solar System">Solar System</a></div></div><div class="tsingle" style="width:84px;max-width:84px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Galaxymap.com,_map_1000_parsecs_(2022).png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Galaxymap.com%2C_map_1000_parsecs_%282022%29.png/82px-Galaxymap.com%2C_map_1000_parsecs_%282022%29.png" decoding="async" width="82" height="82" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Galaxymap.com%2C_map_1000_parsecs_%282022%29.png/123px-Galaxymap.com%2C_map_1000_parsecs_%282022%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Galaxymap.com%2C_map_1000_parsecs_%282022%29.png/164px-Galaxymap.com%2C_map_1000_parsecs_%282022%29.png 2x" data-file-width="2160" data-file-height="2160" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Molecular_cloud" title="Molecular cloud">Molecular clouds</a> around the Sun inside the <a href="/wiki/Orion-Cygnus_Arm" class="mw-redirect" title="Orion-Cygnus Arm">Orion-Cygnus Arm</a></div></div><div class="tsingle" style="width:95px;max-width:95px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Milky_Way_Arms_ssc2008-10.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Milky_Way_Arms_ssc2008-10.svg/93px-Milky_Way_Arms_ssc2008-10.svg.png" decoding="async" width="93" height="84" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Milky_Way_Arms_ssc2008-10.svg/140px-Milky_Way_Arms_ssc2008-10.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a7/Milky_Way_Arms_ssc2008-10.svg/186px-Milky_Way_Arms_ssc2008-10.svg.png 2x" data-file-width="512" data-file-height="461" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Orion_Arm" title="Orion Arm">Orion Arm</a></div></div><div class="tsingle" style="width:85px;max-width:85px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Artist%27s_impression_of_the_Milky_Way_(updated_-_annotated).jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/Artist%27s_impression_of_the_Milky_Way_%28updated_-_annotated%29.jpg/83px-Artist%27s_impression_of_the_Milky_Way_%28updated_-_annotated%29.jpg" decoding="async" width="83" height="83" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/Artist%27s_impression_of_the_Milky_Way_%28updated_-_annotated%29.jpg/125px-Artist%27s_impression_of_the_Milky_Way_%28updated_-_annotated%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/12/Artist%27s_impression_of_the_Milky_Way_%28updated_-_annotated%29.jpg/166px-Artist%27s_impression_of_the_Milky_Way_%28updated_-_annotated%29.jpg 2x" data-file-width="5600" data-file-height="5600" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a></div></div><div class="tsingle" style="width:113px;max-width:113px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Local_Group_and_nearest_galaxies.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Local_Group_and_nearest_galaxies.jpg/111px-Local_Group_and_nearest_galaxies.jpg" decoding="async" width="111" height="83" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Local_Group_and_nearest_galaxies.jpg/167px-Local_Group_and_nearest_galaxies.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Local_Group_and_nearest_galaxies.jpg/222px-Local_Group_and_nearest_galaxies.jpg 2x" data-file-width="4249" data-file-height="3169" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Local_Group" title="Local Group">Local Group</a></div></div><div class="tsingle" style="width:88px;max-width:88px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Local_supercluster-ly.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Local_supercluster-ly.jpg/86px-Local_supercluster-ly.jpg" decoding="async" width="86" height="83" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Local_supercluster-ly.jpg/129px-Local_supercluster-ly.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Local_supercluster-ly.jpg/172px-Local_supercluster-ly.jpg 2x" data-file-width="426" data-file-height="413" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Virgo_Supercluster" title="Virgo Supercluster">Virgo SCl</a></div></div><div class="tsingle" style="width:85px;max-width:85px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Observable_universe_r2.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Observable_universe_r2.jpg/83px-Observable_universe_r2.jpg" decoding="async" width="83" height="83" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Observable_universe_r2.jpg/125px-Observable_universe_r2.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/64/Observable_universe_r2.jpg/166px-Observable_universe_r2.jpg 2x" data-file-width="768" data-file-height="768" /></a></span></div><div class="thumbcaption text-align-center"><a href="/wiki/Laniakea_Supercluster" title="Laniakea Supercluster">Laniakea SCl</a></div></div><div class="tsingle" style="width:85px;max-width:85px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Observable_Universe_with_Measurements_01.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Observable_Universe_with_Measurements_01.png/83px-Observable_Universe_with_Measurements_01.png" decoding="async" width="83" height="83" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Observable_Universe_with_Measurements_01.png/125px-Observable_Universe_with_Measurements_01.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/98/Observable_Universe_with_Measurements_01.png/166px-Observable_Universe_with_Measurements_01.png 2x" data-file-width="3072" data-file-height="3072" /></a></span></div><div class="thumbcaption text-align-center">Our Universe</div></div></div></div></div> <div class="thumb tnone" style="margin-left:auto;margin-right:auto;overflow:hidden;width:auto;max-width:2260px"><div class="thumbinner"><div class="thumbimage noresize" style="overflow:auto"><span typeof="mw:File"><a href="/wiki/File:Location_of_Earth_(9x1-English_Annot-small).png" class="mw-file-description" title="A diagram of the Earth's location in the observable universe. (Alternative image.)"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Location_of_Earth_%289x1-English_Annot-small%29.png/2250px-Location_of_Earth_%289x1-English_Annot-small%29.png" decoding="async" width="2250" height="183" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Location_of_Earth_%289x1-English_Annot-small%29.png/3375px-Location_of_Earth_%289x1-English_Annot-small%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Location_of_Earth_%289x1-English_Annot-small%29.png/4500px-Location_of_Earth_%289x1-English_Annot-small%29.png 2x" data-file-width="29999" data-file-height="2440" /></a></span></div><div class="thumbcaption"><div class="magnify"><a href="/wiki/File:Location_of_Earth_(9x1-English_Annot-small).png" title="File:Location of Earth (9x1-English Annot-small).png"> </a></div>A diagram of the Earth's location in the observable universe. (<i><a href="/wiki/File:Location_of_Earth_(3x3-English_Annot-small).png" title="File:Location of Earth (3x3-English Annot-small).png">Alternative image</a>.</i>)</div></div></div> <div class="thumb tnone" style="margin-left:auto;margin-right:auto;overflow:hidden;width:auto;max-width:2260px"><div class="thumbinner"><div class="thumbimage noresize" style="overflow:auto"><span typeof="mw:File"><a href="/wiki/File:Observable_Universe_Logarithmic_Map_(horizontal_layout_english_annotations).png" class="mw-file-description" title="A logarithmic map of the observable universe. From left to right, spacecraft and celestial bodies are arranged according to their proximity to the Earth."><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/db/Observable_Universe_Logarithmic_Map_%28horizontal_layout_english_annotations%29.png/2250px-Observable_Universe_Logarithmic_Map_%28horizontal_layout_english_annotations%29.png" decoding="async" width="2250" height="552" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/d/db/Observable_Universe_Logarithmic_Map_%28horizontal_layout_english_annotations%29.png 1.5x" data-file-width="3262" data-file-height="800" /></a></span></div><div class="thumbcaption"><div class="magnify"><a href="/wiki/File:Observable_Universe_Logarithmic_Map_(horizontal_layout_english_annotations).png" title="File:Observable Universe Logarithmic Map (horizontal layout english annotations).png"> </a></div>A logarithmic map of the observable universe. From left to right, spacecraft and celestial bodies are arranged according to their proximity to the Earth.</div></div></div> <div class="mw-heading mw-heading2"><h2 id="Gallery">Gallery</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=16" title="Edit section: Gallery"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1273380762/mw-parser-output/.tmulti" /><div class="thumb tmulti tnone center"><div class="thumbinner multiimageinner" style="width:783px;max-width:783px"><div class="trow"><div class="tsingle" style="width:302px;max-width:302px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Observable_universe_logarithmic_illustration.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Observable_universe_logarithmic_illustration.png/300px-Observable_universe_logarithmic_illustration.png" decoding="async" width="300" height="300" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Observable_universe_logarithmic_illustration.png/450px-Observable_universe_logarithmic_illustration.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Observable_universe_logarithmic_illustration.png/600px-Observable_universe_logarithmic_illustration.png 2x" data-file-width="4200" data-file-height="4200" /></a></span></div><div class="thumbcaption">Artist's <a href="/wiki/Logarithmic_scale" title="Logarithmic scale">logarithmic scale</a> conception of the observable universe with the <a href="/wiki/Solar_System" title="Solar System">Solar System</a> at the center, inner and outer <a href="/wiki/Planets" class="mw-redirect" title="Planets">planets</a>, <a href="/wiki/Kuiper_belt" title="Kuiper belt">Kuiper belt</a>, <a href="/wiki/Oort_cloud" title="Oort cloud">Oort cloud</a>, <a href="/wiki/Alpha_Centauri" title="Alpha Centauri">Alpha Centauri</a>, <a href="/wiki/Perseus_Arm" title="Perseus Arm">Perseus Arm</a>, <a href="/wiki/Milky_Way_galaxy" class="mw-redirect" title="Milky Way galaxy">Milky Way galaxy</a>, <a href="/wiki/Andromeda_Galaxy" title="Andromeda Galaxy">Andromeda Galaxy</a>, nearby <a href="/wiki/Galaxy" title="Galaxy">galaxies</a>, <a href="/wiki/Cosmic_web" class="mw-redirect" title="Cosmic web">Cosmic web</a>, <a href="/wiki/Cosmic_microwave_radiation" class="mw-redirect" title="Cosmic microwave radiation">Cosmic microwave radiation</a> and the Big Bang's invisible plasma on the edge. Celestial bodies appear enlarged to appreciate their shapes.</div></div><div class="tsingle" style="width:477px;max-width:477px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:2dfdtfe.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b3/2dfdtfe.gif/475px-2dfdtfe.gif" decoding="async" width="475" height="302" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b3/2dfdtfe.gif/713px-2dfdtfe.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b3/2dfdtfe.gif/950px-2dfdtfe.gif 2x" data-file-width="1074" data-file-height="683" /></a></span></div><div class="thumbcaption"><a href="/wiki/Dtfe" class="mw-redirect" title="Dtfe">DTFE reconstruction</a> of the inner parts of the <a href="/wiki/2dF_Galaxy_Redshift_Survey" title="2dF Galaxy Redshift Survey">2dF Galaxy Redshift Survey</a></div></div></div></div></div> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=17" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/Bolshoi_cosmological_simulation" title="Bolshoi cosmological simulation">Bolshoi cosmological simulation</a> – Computer simulation of the universe</li> <li><a href="/wiki/Causality_(physics)" title="Causality (physics)">Causality (physics)</a> – Physics of the cause–effect relation</li> <li><a href="/wiki/Chronology_of_the_universe" title="Chronology of the universe">Chronology of the universe</a> – History and future of the universe</li> <li><a href="/wiki/Dark_flow" title="Dark flow">Dark flow</a> – Controversial hypothesis in astrophysics</li> <li><a href="/wiki/Hubble_volume" title="Hubble volume">Hubble volume</a> – Region of the observable universe</li> <li><a href="/wiki/Illustris_project" title="Illustris project">Illustris project</a> – Computer-simulated universes</li> <li><a href="/wiki/Multiverse" title="Multiverse">Multiverse</a> – Hypothetical group of multiple universes</li> <li><a href="/wiki/Orders_of_magnitude_(length)" title="Orders of magnitude (length)">Orders of magnitude (length)</a> – Comparison of a wide range of lengths</li> <li><a href="/wiki/UniverseMachine" title="UniverseMachine">UniverseMachine</a> – Computer simulated universes</li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=18" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">Multiply percentage of ordinary matter given by Planck below, with total energy density given by WMAP below</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">This is when hydrogen atoms were formed from protons and electrons and the universe became transparent to electromagnetic radiation.</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"> <a href="/wiki/Special_relativity" title="Special relativity">Special relativity</a> prevents nearby objects in the same local region from moving faster than the speed of light with respect to each other, but there is no such constraint for distant objects when the space between them is expanding; see <a href="/wiki/Comoving_and_proper_distances#Uses_of_the_proper_distance" title="Comoving and proper distances">uses of the proper distance</a> for a discussion.</span> </li> <li id="cite_note-mapofuniverse2-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-mapofuniverse2_19-0">^</a></b></span> <span class="reference-text">The comoving distance of the future visibility limit is calculated on p. 8 of Gott et al.'s <a rel="nofollow" class="external text" href="http://www.astro.princeton.edu/universe/ms.pdf">A Map of the Universe</a> to be 4.50 times the <a href="/wiki/Hubble_radius" class="mw-redirect" title="Hubble radius">Hubble radius</a>, given as 4.220 billion parsecs (13.76 billion light-years), whereas the current comoving radius of the observable universe is calculated on p. 7 to be 3.38 times the Hubble radius. The number of galaxies in a sphere of a given comoving radius is proportional to the cube of the radius, so as shown on p. 8 the ratio between the number of galaxies observable in the future visibility limit to the number of galaxies observable today would be (4.50/3.38)<sup>3</sup> = 2.36.</span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text">This does not mean "unbounded" in the mathematical sense; a finite universe would have an upper bound on the distance between two points. Rather, it means that there is no boundary past which there is nothing. See <i><a href="/wiki/Geodesic_manifold" class="mw-redirect" title="Geodesic manifold">Geodesic manifold</a></i>.</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=19" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626" /><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFItzhak_BarsJohn_Terning2009" class="citation book cs1">Itzhak Bars; John Terning (2009). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=fFSMatekilIC&pg=PA27"><i>Extra Dimensions in Space and Time</i></a>. Springer. pp. 27–. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0387776378" title="Special:BookSources/978-0387776378"><bdi>978-0387776378</bdi></a><span class="reference-accessdate">. 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"The Temperature of the Cosmic Microwave Background". <i>The Astrophysical Journal</i>. <b>707</b> (2): <span class="nowrap">916–</span>920. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/0911.1955">0911.1955</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009ApJ...707..916F">2009ApJ...707..916F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F0004-637X%2F707%2F2%2F916">10.1088/0004-637X/707/2/916</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:119217397">119217397</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=The+Temperature+of+the+Cosmic+Microwave+Background&rft.volume=707&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E916-%3C%2Fspan%3E920&rft.date=2009-11-30&rft_id=info%3Aarxiv%2F0911.1955&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A119217397%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F0004-637X%2F707%2F2%2F916&rft_id=info%3Abibcode%2F2009ApJ...707..916F&rft.aulast=Fixsen&rft.aufirst=D.+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.esa.int/spaceinimages/Images/2013/03/Planck_cosmic_recipe">"Planck cosmic recipe"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Planck+cosmic+recipe&rft_id=https%3A%2F%2Fwww.esa.int%2Fspaceinimages%2FImages%2F2013%2F03%2FPlanck_cosmic_recipe&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-mapofuniverse-9"><span class="mw-cite-backlink">^ <a href="#cite_ref-mapofuniverse_9-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-mapofuniverse_9-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-mapofuniverse_9-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGott_IIIMario_JurićDavid_SchlegelFiona_Hoyle2005" class="citation journal cs1">Gott III, J. Richard; Mario Jurić; David Schlegel; Fiona Hoyle; et al. (2005). <a rel="nofollow" class="external text" href="http://www.astro.princeton.edu/universe/ms.pdf">"A Map of the Universe"</a> <span class="cs1-format">(PDF)</span>. <i>The Astrophysical Journal</i>. <b>624</b> (2): <span class="nowrap">463–</span>484. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0310571">astro-ph/0310571</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005ApJ...624..463G">2005ApJ...624..463G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F428890">10.1086/428890</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:9654355">9654355</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=A+Map+of+the+Universe&rft.volume=624&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E463-%3C%2Fspan%3E484&rft.date=2005&rft_id=info%3Aarxiv%2Fastro-ph%2F0310571&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A9654355%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1086%2F428890&rft_id=info%3Abibcode%2F2005ApJ...624..463G&rft.aulast=Gott+III&rft.aufirst=J.+Richard&rft.au=Mario+Juri%C4%87&rft.au=David+Schlegel&rft.au=Fiona+Hoyle&rft.au=Michael+Vogeley&rft.au=Max+Tegmark&rft.au=Neta+Bahcall&rft.au=Jon+Brinkmann&rft_id=http%3A%2F%2Fwww.astro.princeton.edu%2Funiverse%2Fms.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://astro.ucla.edu/~wright/cosmology_faq.html">"Frequently Asked Questions in Cosmology"</a>. <i>astro.ucla.edu</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2023-09-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=astro.ucla.edu&rft.atitle=Frequently+Asked+Questions+in+Cosmology&rft_id=https%3A%2F%2Fastro.ucla.edu%2F~wright%2Fcosmology_faq.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-ly93-11"><span class="mw-cite-backlink">^ <a href="#cite_ref-ly93_11-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ly93_11-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-ly93_11-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-ly93_11-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLineweaverDavis2005" class="citation journal cs1">Lineweaver, Charles; Davis, Tamara M. (2005). "Misconceptions about the Big Bang". <i>Scientific American</i>. <b>292</b> (3): <span class="nowrap">36–</span>45. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005SciAm.292c..36L">2005SciAm.292c..36L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fscientificamerican0305-36">10.1038/scientificamerican0305-36</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+American&rft.atitle=Misconceptions+about+the+Big+Bang&rft.volume=292&rft.issue=3&rft.pages=%3Cspan+class%3D%22nowrap%22%3E36-%3C%2Fspan%3E45&rft.date=2005&rft_id=info%3Adoi%2F10.1038%2Fscientificamerican0305-36&rft_id=info%3Abibcode%2F2005SciAm.292c..36L&rft.aulast=Lineweaver&rft.aufirst=Charles&rft.au=Davis%2C+Tamara+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text">See the "Mass of ordinary matter" section in this article.</span> </li> <li id="cite_note-NYT-20181203-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-NYT-20181203_13-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFOverbye2018" class="citation news cs1"><a href="/wiki/Dennis_Overbye" title="Dennis Overbye">Overbye, Dennis</a> (3 December 2018). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2018/12/03/science/space-stars-photons-light.html">"All the Light There Is to See? 4 x 10<sup>84</sup> Photons"</a>. <i><a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a></i><span class="reference-accessdate">. Retrieved <span class="nowrap">4 December</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=All+the+Light+There+Is+to+See%3F+4+x+10%3Csup%3E84%3C%2Fsup%3E+Photons&rft.date=2018-12-03&rft.aulast=Overbye&rft.aufirst=Dennis&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2018%2F12%2F03%2Fscience%2Fspace-stars-photons-light.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-SCI-20181130-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-SCI-20181130_14-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFThe_Fermi-LAT_Collaboration2018" class="citation journal cs1">The Fermi-LAT Collaboration (30 November 2018). "A gamma-ray determination of the Universe's star formation history". <i><a href="/wiki/Science_(journal)" title="Science (journal)">Science</a></i>. <b>362</b> (6418): <span class="nowrap">1031–</span>1034. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1812.01031">1812.01031</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2018Sci...362.1031F">2018Sci...362.1031F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.aat8123">10.1126/science.aat8123</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/30498122">30498122</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=A+gamma-ray+determination+of+the+Universe%27s+star+formation+history&rft.volume=362&rft.issue=6418&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1031-%3C%2Fspan%3E1034&rft.date=2018-11-30&rft_id=info%3Aarxiv%2F1812.01031&rft_id=info%3Apmid%2F30498122&rft_id=info%3Adoi%2F10.1126%2Fscience.aat8123&rft_id=info%3Abibcode%2F2018Sci...362.1031F&rft.au=The+Fermi-LAT+Collaboration&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-Loeb2002-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-Loeb2002_15-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLoeb2002" class="citation journal cs1">Loeb, Abraham (2002). "Long-term future of extragalactic astronomy". <i>Physical Review D</i>. <b>65</b> (4): 047301. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0107568">astro-ph/0107568</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2002PhRvD..65d7301L">2002PhRvD..65d7301L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1103%2FPhysRevD.65.047301">10.1103/PhysRevD.65.047301</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:1791226">1791226</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Physical+Review+D&rft.atitle=Long-term+future+of+extragalactic+astronomy&rft.volume=65&rft.issue=4&rft.pages=047301&rft.date=2002&rft_id=info%3Aarxiv%2Fastro-ph%2F0107568&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A1791226%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1103%2FPhysRevD.65.047301&rft_id=info%3Abibcode%2F2002PhRvD..65d7301L&rft.aulast=Loeb&rft.aufirst=Abraham&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLiddle2015" class="citation book cs1">Liddle, Andrew (2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=4lPWBgAAQBAJ&dq=infinite+universe+observable&pg=PA33"><i>An Introduction to Modern Cosmology</i></a>. John Wiley. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1118502143" title="Special:BookSources/978-1118502143"><bdi>978-1118502143</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=An+Introduction+to+Modern+Cosmology&rft.pub=John+Wiley&rft.date=2015&rft.isbn=978-1118502143&rft.aulast=Liddle&rft.aufirst=Andrew&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D4lPWBgAAQBAJ%26dq%3Dinfinite%2Buniverse%2Bobservable%26pg%3DPA33&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://curious.astro.cornell.edu/question.php?number=575">Is the universe expanding faster than the speed of light?</a> (see the last two paragraphs).</span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKraussScherrer2007" class="citation journal cs1">Krauss, Lawrence M.; Scherrer, Robert J. (2007). "The Return of a Static Universe and the End of Cosmology". <i>General Relativity and Gravitation</i>. <b>39</b> (10): <span class="nowrap">1545–</span>1550. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/0704.0221">0704.0221</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2007GReGr..39.1545K">2007GReGr..39.1545K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10714-007-0472-9">10.1007/s10714-007-0472-9</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:123442313">123442313</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=General+Relativity+and+Gravitation&rft.atitle=The+Return+of+a+Static+Universe+and+the+End+of+Cosmology&rft.volume=39&rft.issue=10&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1545-%3C%2Fspan%3E1550&rft.date=2007&rft_id=info%3Aarxiv%2F0704.0221&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A123442313%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1007%2Fs10714-007-0472-9&rft_id=info%3Abibcode%2F2007GReGr..39.1545K&rft.aulast=Krauss&rft.aufirst=Lawrence+M.&rft.au=Scherrer%2C+Robert+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://www.npr.org/templates/story/story.php?storyId=102715275">Using Tiny Particles To Answer Giant Questions</a>. Science Friday, 3 Apr 2009. According to the <a rel="nofollow" class="external text" href="https://www.npr.org/templates/transcript/transcript.php?storyId=102715275">transcript</a>, <a href="/wiki/Brian_Greene" title="Brian Greene">Brian Greene</a> makes the comment "And actually, in the far future, everything we now see, except for our local galaxy and a region of galaxies will have disappeared. The entire universe will disappear before our very eyes, and it's one of my arguments for actually funding cosmology. We've got to do it while we have a chance."</span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text">See also <a href="/wiki/Faster_than_light#Universal_expansion" class="mw-redirect" title="Faster than light">Faster than light#Universal expansion</a> and <a href="/wiki/Future_of_an_expanding_universe#Galaxies_outside_the_Local_Supercluster_are_no_longer_detectable" title="Future of an expanding universe">Future of an expanding universe#Galaxies outside the Local Supercluster are no longer detectable</a>.</span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLoeb2002" class="citation journal cs1">Loeb, Abraham (2002). "The Long-Term Future of Extragalactic Astronomy". <i>Physical Review D</i>. <b>65</b> (4): 047301. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0107568">astro-ph/0107568</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2002PhRvD..65d7301L">2002PhRvD..65d7301L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1103%2FPhysRevD.65.047301">10.1103/PhysRevD.65.047301</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:1791226">1791226</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Physical+Review+D&rft.atitle=The+Long-Term+Future+of+Extragalactic+Astronomy&rft.volume=65&rft.issue=4&rft.pages=047301&rft.date=2002&rft_id=info%3Aarxiv%2Fastro-ph%2F0107568&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A1791226%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1103%2FPhysRevD.65.047301&rft_id=info%3Abibcode%2F2002PhRvD..65d7301L&rft.aulast=Loeb&rft.aufirst=Abraham&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSiegel" class="citation web cs1">Siegel, Ethan. <a rel="nofollow" class="external text" href="https://www.forbes.com/sites/startswithabang/2019/03/05/how-much-of-the-unobservable-universe-will-we-someday-be-able-to-see/">"How Much Of The Unobservable Universe Will We Someday Be Able To See?"</a>. <i>Forbes</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2023-04-04</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Forbes&rft.atitle=How+Much+Of+The+Unobservable+Universe+Will+We+Someday+Be+Able+To+See%3F&rft.aulast=Siegel&rft.aufirst=Ethan&rft_id=https%3A%2F%2Fwww.forbes.com%2Fsites%2Fstartswithabang%2F2019%2F03%2F05%2Fhow-much-of-the-unobservable-universe-will-we-someday-be-able-to-see%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSiegel2021" class="citation web cs1">Siegel, Ethan (2021-10-25). <a rel="nofollow" class="external text" href="https://medium.com/starts-with-a-bang/94-of-the-universes-galaxies-are-permanently-beyond-our-reach-293c29e771be">"94% of the universe's galaxies are permanently beyond our reach"</a>. <i>Starts With A Bang!</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2023-04-04</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Starts+With+A+Bang%21&rft.atitle=94%25+of+the+universe%27s+galaxies+are+permanently+beyond+our+reach&rft.date=2021-10-25&rft.aulast=Siegel&rft.aufirst=Ethan&rft_id=https%3A%2F%2Fmedium.com%2Fstarts-with-a-bang%2F94-of-the-universes-galaxies-are-permanently-beyond-our-reach-293c29e771be&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text">Ord, Toby. (2021). The Edges of Our Universe. <a rel="nofollow" class="external autonumber" href="https://www.researchgate.net/publication/350647191_The_Edges_of_Our_Universe">[1]</a></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKazanas1980" class="citation journal cs1">Kazanas, D. (1980). <a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F183361">"Dynamics of the universe and spontaneous symmetry breaking"</a>. <i>The Astrophysical Journal</i>. <b>241</b>: <span class="nowrap">L59 –</span> <span class="nowrap">L63</span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1980ApJ...241L..59K">1980ApJ...241L..59K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F183361">10.1086/183361</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=Dynamics+of+the+universe+and+spontaneous+symmetry+breaking&rft.volume=241&rft.pages=%3Cspan+class%3D%22nowrap%22%3EL59+-%3C%2Fspan%3E+%3Cspan+class%3D%22nowrap%22%3EL63%3C%2Fspan%3E&rft.date=1980&rft_id=info%3Adoi%2F10.1086%2F183361&rft_id=info%3Abibcode%2F1980ApJ...241L..59K&rft.aulast=Kazanas&rft.aufirst=D.&rft_id=https%3A%2F%2Fdoi.org%2F10.1086%252F183361&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGuth1997" class="citation book cs1">Guth, Alan H. (1997). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/inflationaryuniv0000guth"><i>The inflationary universe: the quest for a new theory of cosmic origins</i></a></span>. Basic Books. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/inflationaryuniv0000guth/page/186">186</a>–. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0201328400" title="Special:BookSources/978-0201328400"><bdi>978-0201328400</bdi></a><span class="reference-accessdate">. Retrieved <span class="nowrap">1 May</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+inflationary+universe%3A+the+quest+for+a+new+theory+of+cosmic+origins&rft.pages=186-&rft.pub=Basic+Books&rft.date=1997&rft.isbn=978-0201328400&rft.aulast=Guth&rft.aufirst=Alan+H.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Finflationaryuniv0000guth&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBielewiczBandayGorski2013" class="citation journal cs1">Bielewicz, P.; Banday, A. J.; Gorski, K. M. (2013). Auge, E.; Dumarchez, J.; Tran Thanh Van, J. (eds.). 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title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+Reports&rft.atitle=Emergence+of+life+in+an+inflationary+universe&rft.volume=10&rft.issue=1671&rft.pages=1671&rft.date=2020-02-03&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC6997386%23id-name%3DPMC&rft_id=info%3Abibcode%2F2020NatSR..10.1671T&rft_id=info%3Aarxiv%2F1911.08092&rft_id=info%3Apmid%2F32015390&rft_id=info%3Adoi%2F10.1038%2Fs41598-020-58060-0&rft.aulast=Totani&rft.aufirst=Tomonori&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC6997386&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-Paul_Davies_2006_43-53"><span class="mw-cite-backlink"><b><a href="#cite_ref-Paul_Davies_2006_43_53-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDavies2006" class="citation book cs1">Davies, Paul (2006). <a rel="nofollow" class="external text" href="https://archive.org/details/cosmicjackpotwhy0000davi/page/43"><i>The Goldilocks Enigma</i></a>. First Mariner Books. p. <a rel="nofollow" class="external text" href="https://archive.org/details/cosmicjackpotwhy0000davi/page/43">43–</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0618592265" title="Special:BookSources/978-0618592265"><bdi>978-0618592265</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Goldilocks+Enigma&rft.pages=43-&rft.pub=First+Mariner+Books&rft.date=2006&rft.isbn=978-0618592265&rft.aulast=Davies&rft.aufirst=Paul&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fcosmicjackpotwhy0000davi%2Fpage%2F43&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-54"><span class="mw-cite-backlink"><b><a href="#cite_ref-54">^</a></b></span> <span class="reference-text">See <a href="/wiki/Friedmann_equations#Density_parameter" title="Friedmann equations">Friedmann equations#Density parameter</a>.</span> </li> <li id="cite_note-55"><span class="mw-cite-backlink"><b><a href="#cite_ref-55">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKaku2006" class="citation book cs1">Kaku, Michio (2006). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=cKULZJpcJBwC"><i>Parallel Worlds: A Journey Through Creation, Higher Dimensions, and the Future of the Cosmos</i></a>. Knopf Doubleday. p. 385. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0307276988" title="Special:BookSources/978-0307276988"><bdi>978-0307276988</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Parallel+Worlds%3A+A+Journey+Through+Creation%2C+Higher+Dimensions%2C+and+the+Future+of+the+Cosmos&rft.pages=385&rft.pub=Knopf+Doubleday&rft.date=2006&rft.isbn=978-0307276988&rft.aulast=Kaku&rft.aufirst=Michio&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DcKULZJpcJBwC&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-56"><span class="mw-cite-backlink"><b><a href="#cite_ref-56">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSchutz2003" class="citation book cs1">Schutz, Bernard F. (2003). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=iEZNXvYwyNwC&pg=PA361"><i>Gravity from the ground up</i></a>. Cambridge University Press. pp. 361–. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0521455060" title="Special:BookSources/978-0521455060"><bdi>978-0521455060</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Gravity+from+the+ground+up&rft.pages=361-&rft.pub=Cambridge+University+Press&rft.date=2003&rft.isbn=978-0521455060&rft.aulast=Schutz&rft.aufirst=Bernard+F.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DiEZNXvYwyNwC%26pg%3DPA361&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-planck_cosmological_parameters-57"><span class="mw-cite-backlink"><b><a href="#cite_ref-planck_cosmological_parameters_57-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPlanck_collaboration2013" class="citation journal cs1">Planck collaboration (2013). "Planck 2013 results. XVI. Cosmological parameters". <i>Astronomy & Astrophysics</i>. <b>571</b>: A16. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1303.5076">1303.5076</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2014A&A...571A..16P">2014A&A...571A..16P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1051%2F0004-6361%2F201321591">10.1051/0004-6361/201321591</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118349591">118349591</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy+%26+Astrophysics&rft.atitle=Planck+2013+results.+XVI.+Cosmological+parameters&rft.volume=571&rft.pages=A16&rft.date=2013&rft_id=info%3Aarxiv%2F1303.5076&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118349591%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1051%2F0004-6361%2F201321591&rft_id=info%3Abibcode%2F2014A%26A...571A..16P&rft.au=Planck+collaboration&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-58"><span class="mw-cite-backlink"><b><a href="#cite_ref-58">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.spacetelescope.org/images/potw1833a/">"Galactic treasure chest"</a>. <i>www.spacetelescope.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">13 August</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.spacetelescope.org&rft.atitle=Galactic+treasure+chest&rft_id=http%3A%2F%2Fwww.spacetelescope.org%2Fimages%2Fpotw1833a%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-59"><span class="mw-cite-backlink"><b><a href="#cite_ref-59">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.eso.org/public/videos/cluesAdler-cylindrical/">"Blueprints of the Universe"</a>. <i>www.eso.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">31 December</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.eso.org&rft.atitle=Blueprints+of+the+Universe&rft_id=https%3A%2F%2Fwww.eso.org%2Fpublic%2Fvideos%2FcluesAdler-cylindrical%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-60"><span class="mw-cite-backlink"><b><a href="#cite_ref-60">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCarrollOstlie2013" class="citation book cs1">Carroll, Bradley W.; Ostlie, Dale A. (2013). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=RLwangEACAAJ"><i>An Introduction to Modern Astrophysics</i></a> (International ed.). Pearson. p. 1178. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1292022932" title="Special:BookSources/978-1292022932"><bdi>978-1292022932</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=An+Introduction+to+Modern+Astrophysics&rft.pages=1178&rft.edition=International&rft.pub=Pearson&rft.date=2013&rft.isbn=978-1292022932&rft.aulast=Carroll&rft.aufirst=Bradley+W.&rft.au=Ostlie%2C+Dale+A.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DRLwangEACAAJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-Kirshner-61"><span class="mw-cite-backlink">^ <a href="#cite_ref-Kirshner_61-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Kirshner_61-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Kirshner_61-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKirshner2002" class="citation book cs1">Kirshner, Robert P. (2002). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/extravagantunive00kirs"><i>The Extravagant Universe: Exploding Stars, Dark Energy and the Accelerating Cosmos</i></a></span>. Princeton University Press. p. <a rel="nofollow" class="external text" href="https://archive.org/details/extravagantunive00kirs/page/71">71</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0691058627" title="Special:BookSources/978-0691058627"><bdi>978-0691058627</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Extravagant+Universe%3A+Exploding+Stars%2C+Dark+Energy+and+the+Accelerating+Cosmos&rft.pages=71&rft.pub=Princeton+University+Press&rft.date=2002&rft.isbn=978-0691058627&rft.aulast=Kirshner&rft.aufirst=Robert+P.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fextravagantunive00kirs&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-62"><span class="mw-cite-backlink"><b><a href="#cite_ref-62">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.spacetelescope.org/images/heic2003a/">"Map of the Cosmic Web Generated from Slime Mould Algorithm"</a>. <i>www.spacetelescope.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.spacetelescope.org&rft.atitle=Map+of+the+Cosmic+Web+Generated+from+Slime+Mould+Algorithm&rft_id=https%3A%2F%2Fwww.spacetelescope.org%2Fimages%2Fheic2003a%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-63"><span class="mw-cite-backlink"><b><a href="#cite_ref-63">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCarrollOstlie2013" class="citation book cs1">Carroll, Bradley W.; Ostlie, Dale A. (2013). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=RLwangEACAAJ"><i>An Introduction to Modern Astrophysics</i></a> (International ed.). Pearson. pp. <span class="nowrap">1173–</span>1174. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1292022932" title="Special:BookSources/978-1292022932"><bdi>978-1292022932</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=An+Introduction+to+Modern+Astrophysics&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1173-%3C%2Fspan%3E1174&rft.edition=International&rft.pub=Pearson&rft.date=2013&rft.isbn=978-1292022932&rft.aulast=Carroll&rft.aufirst=Bradley+W.&rft.au=Ostlie%2C+Dale+A.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DRLwangEACAAJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-redshift-64"><span class="mw-cite-backlink"><b><a href="#cite_ref-redshift_64-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGellerHuchra1989" class="citation journal cs1">Geller, M. J.; Huchra, J. P. (1989). "Mapping the universe". <i>Science</i>. <b>246</b> (4932): <span class="nowrap">897–</span>903. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1989Sci...246..897G">1989Sci...246..897G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.246.4932.897">10.1126/science.246.4932.897</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/17812575">17812575</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:31328798">31328798</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=Mapping+the+universe.&rft.volume=246&rft.issue=4932&rft.pages=%3Cspan+class%3D%22nowrap%22%3E897-%3C%2Fspan%3E903&rft.date=1989&rft_id=info%3Adoi%2F10.1126%2Fscience.246.4932.897&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A31328798%23id-name%3DS2CID&rft_id=info%3Apmid%2F17812575&rft_id=info%3Abibcode%2F1989Sci...246..897G&rft.aulast=Geller&rft.aufirst=M.+J.&rft.au=Huchra%2C+J.+P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-65"><span class="mw-cite-backlink"><b><a href="#cite_ref-65">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.newscientist.com/article/dn12546-biggest-void-in-space-is-1-billion-light-years-across/">"Biggest void in space is 1 billion light years across"</a>. <i>New Scientist</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2023-09-15</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=New+Scientist&rft.atitle=Biggest+void+in+space+is+1+billion+light+years+across&rft_id=https%3A%2F%2Fwww.newscientist.com%2Farticle%2Fdn12546-biggest-void-in-space-is-1-billion-light-years-across%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-66"><span class="mw-cite-backlink"><b><a href="#cite_ref-66">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFWall2013" class="citation web cs1">Wall, Mike (2013-01-11). <a rel="nofollow" class="external text" href="https://www.foxnews.com/science/largest-structure-in-universe-discovered/">"Largest structure in universe discovered"</a>. <a href="/wiki/Fox_News" title="Fox News">Fox News</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Largest+structure+in+universe+discovered&rft.pub=Fox+News&rft.date=2013-01-11&rft.aulast=Wall&rft.aufirst=Mike&rft_id=https%3A%2F%2Fwww.foxnews.com%2Fscience%2Flargest-structure-in-universe-discovered%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-2014paper-67"><span class="mw-cite-backlink">^ <a href="#cite_ref-2014paper_67-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-2014paper_67-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHorváthHakkilaBagoly2014" class="citation journal cs1">Horváth, I.; Hakkila, Jon; Bagoly, Z. (2014). 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Retrieved <span class="nowrap">2023-07-01</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.astro.ucla.edu&rft.atitle=Light+Travel+Time+Distance&rft_id=https%3A%2F%2Fwww.astro.ucla.edu%2F~wright%2FDltt_is_Dumb.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> <li id="cite_note-81"><span class="mw-cite-backlink"><b><a href="#cite_ref-81">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMeszaros,_Attila2009" class="citation journal cs1">Meszaros, Attila; et al. (2009). "Impact on cosmology of the celestial anisotropy of the short gamma-ray bursts". <i>Baltic Astronomy</i>. <b>18</b>: <span class="nowrap">293–</span>296. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1005.1558">1005.1558</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009BaltA..18..293M">2009BaltA..18..293M</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Baltic+Astronomy&rft.atitle=Impact+on+cosmology+of+the+celestial+anisotropy+of+the+short+gamma-ray+bursts&rft.volume=18&rft.pages=%3Cspan+class%3D%22nowrap%22%3E293-%3C%2Fspan%3E296&rft.date=2009&rft_id=info%3Aarxiv%2F1005.1558&rft_id=info%3Abibcode%2F2009BaltA..18..293M&rft.au=Meszaros%2C+Attila&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=20" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFVicent_J._MartínezJean-Luc_StarckEnn_SaarDavid_L._Donoho2005" class="citation journal cs1">Vicent J. Martínez; Jean-Luc Starck; Enn Saar; <a href="/wiki/David_Donoho" title="David Donoho">David L. Donoho</a>; et al. (2005). "Morphology Of The Galaxy Distribution From Wavelet Denoising". <i>The Astrophysical Journal</i>. <b>634</b> (2): <span class="nowrap">744–</span>755. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0508326">astro-ph/0508326</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005ApJ...634..744M">2005ApJ...634..744M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F497125">10.1086/497125</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14905675">14905675</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=Morphology+Of+The+Galaxy+Distribution+From+Wavelet+Denoising&rft.volume=634&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E744-%3C%2Fspan%3E755&rft.date=2005&rft_id=info%3Aarxiv%2Fastro-ph%2F0508326&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A14905675%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1086%2F497125&rft_id=info%3Abibcode%2F2005ApJ...634..744M&rft.au=Vicent+J.+Mart%C3%ADnez&rft.au=Jean-Luc+Starck&rft.au=Enn+Saar&rft.au=David+L.+Donoho&rft.au=Simon+Reynolds&rft.au=Pablo+de+la+Cruz&rft.au=Silvestre+Paredes&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMureika,_J._R.Dyer,_C._C.2004" class="citation journal cs1">Mureika, J. R. & Dyer, C. C. (2004). "Review: Multifractal Analysis of Packed Swiss Cheese Cosmologies". <i>General Relativity and Gravitation</i>. <b>36</b> (1): <span class="nowrap">151–</span>184. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/gr-qc/0505083">gr-qc/0505083</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2004GReGr..36..151M">2004GReGr..36..151M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1023%2FB%3AGERG.0000006699.45969.49">10.1023/B:GERG.0000006699.45969.49</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:13977714">13977714</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=General+Relativity+and+Gravitation&rft.atitle=Review%3A+Multifractal+Analysis+of+Packed+Swiss+Cheese+Cosmologies&rft.volume=36&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E151-%3C%2Fspan%3E184&rft.date=2004&rft_id=info%3Aarxiv%2Fgr-qc%2F0505083&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A13977714%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1023%2FB%3AGERG.0000006699.45969.49&rft_id=info%3Abibcode%2F2004GReGr..36..151M&rft.au=Mureika%2C+J.+R.&rft.au=Dyer%2C+C.+C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGott,_III,_J._R.2005" class="citation journal cs1">Gott, III, J. R.; et al. (May 2005). "A Map of the Universe". <i>The Astrophysical Journal</i>. <b>624</b> (2): <span class="nowrap">463–</span>484. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0310571">astro-ph/0310571</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2005ApJ...624..463G">2005ApJ...624..463G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F428890">10.1086/428890</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:9654355">9654355</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=A+Map+of+the+Universe&rft.volume=624&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E463-%3C%2Fspan%3E484&rft.date=2005-05&rft_id=info%3Aarxiv%2Fastro-ph%2F0310571&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A9654355%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1086%2F428890&rft_id=info%3Abibcode%2F2005ApJ...624..463G&rft.au=Gott%2C+III%2C+J.+R.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_journal" title="Template:Cite journal">cite journal</a>}}</code>: CS1 maint: multiple names: authors list (<a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">link</a>)</span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLabiniMontuoriPietronero1998" class="citation journal cs1">Labini, F. Sylos; Montuori, M. & Pietronero, L. (1998). "Scale-invariance of galaxy clustering". <i>Physics Reports</i>. <b>293</b> (1): <span class="nowrap">61–</span>226. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/9711073">astro-ph/9711073</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1998PhR...293...61S">1998PhR...293...61S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2FS0370-1573%2897%2900044-6">10.1016/S0370-1573(97)00044-6</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:119519125">119519125</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Physics+Reports&rft.atitle=Scale-invariance+of+galaxy+clustering&rft.volume=293&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E61-%3C%2Fspan%3E226&rft.date=1998&rft_id=info%3Aarxiv%2Fastro-ph%2F9711073&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A119519125%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1016%2FS0370-1573%2897%2900044-6&rft_id=info%3Abibcode%2F1998PhR...293...61S&rft.aulast=Labini&rft.aufirst=F.+Sylos&rft.au=Montuori%2C+M.&rft.au=Pietronero%2C+L.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AObservable+universe" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Observable_universe&action=edit&section=21" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://www.mpa-garching.mpg.de/galform/millennium/">"Millennium Simulation" of structure forming</a> – Max Planck Institute of Astrophysics, Garching, Germany</li> <li><a rel="nofollow" class="external text" href="https://apod.nasa.gov/apod/ap071107.html">NASA Astronomy Picture of the Day: The Sloan Great Wall: Largest Known Structure? (7 November 2007)</a></li> <li><a rel="nofollow" class="external text" href="http://www.astro.ucla.edu/~wright/cosmology_faq.html">Cosmology FAQ</a></li> <li><a rel="nofollow" class="external text" href="https://www.sciencedaily.com/releases/2007/04/070419125240.htm">Forming Galaxies Captured In The Young Universe By Hubble, VLT & Spitzer</a></li> <li><a rel="nofollow" class="external text" href="http://www.phys.ksu.edu/personal/gahs/phys191/horizon.html">Animation of the cosmic light horizon</a></li> <li><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0305179">Inflation and the Cosmic Microwave Background by Charles Lineweaver</a></li> <li><a rel="nofollow" class="external text" href="http://www.astro.princeton.edu/universe/">Logarithmic Maps of the Universe</a></li> <li><a rel="nofollow" class="external text" href="http://www.mso.anu.edu.au/2dFGRS/">List of publications of the 2dF Galaxy Redshift Survey</a></li> <li><a rel="nofollow" class="external text" href="http://www.atlasoftheuniverse.com/universe.html">The Universe Within 14 Billion Light Years – NASA Atlas of the Universe</a> – Note, this map only gives a rough cosmographical estimate of the expected distribution of superclusters within the observable universe; very little actual mapping has been done beyond a distance of one billion light-years.</li> <li><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=17jymDn0W6U">Video: <i>The Known Universe</i>, from the American Museum of Natural History</a></li> <li><a rel="nofollow" class="external text" href="http://ned.ipac.caltech.edu/">NASA/IPAC Extragalactic Database</a></li> <li><a rel="nofollow" class="external text" href="http://irfu.cea.fr/cosmography">Cosmography of the Local Universe</a> at irfu.cea.fr (17:35) (<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1306.0091">arXiv</a>)</li> <li><a rel="nofollow" class="external text" href="https://www.livescience.com/how-many-atoms-in-universe.html">There are about 10<sup>82</sup> atoms in the observable universe</a> – <i><a href="/wiki/LiveScience" class="mw-redirect" title="LiveScience">LiveScience</a></i>, July 2021</li> <li><a rel="nofollow" class="external text" href="https://www.forbes.com/sites/startswithabang/2019/05/21/this-is-why-we-will-never-know-everything-about-our-universe/">Limits to knowledge about Universe</a> – <i><a href="/wiki/Forbes" title="Forbes">Forbes</a></i>, May 2019</li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output 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Earth">Location of Earth</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Included</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"><a href="/wiki/Earth" title="Earth">Earth</a> <span style="font-size:120%">→</span> <a href="/wiki/Solar_System" title="Solar System">Solar System</a> <span style="font-size:120%">→</span> <a href="/wiki/Local_Interstellar_Cloud" title="Local Interstellar Cloud">Local Interstellar Cloud</a> <span style="font-size:120%">→</span> <a href="/wiki/Local_Bubble" title="Local Bubble">Local Bubble</a> <span style="font-size:120%">→</span> <a href="/wiki/Gould_Belt" title="Gould Belt">Gould Belt</a> <span style="font-size:120%">→</span> <a href="/wiki/Orion_Arm" title="Orion Arm">Orion Arm</a> <span style="font-size:120%">→</span> <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> <span style="font-size:120%">→</span> <a href="/wiki/Satellite_galaxies_of_the_Milky_Way" title="Satellite galaxies of the Milky Way">Milky Way subgroup</a> <span style="font-size:120%">→</span> <a href="/wiki/Local_Group" title="Local Group">Local Group</a> <span style="font-size:120%">→</span> <a href="/wiki/Local_Sheet" title="Local Sheet">Local Sheet</a> <span style="font-size:120%">→</span> <a href="/wiki/Virgo_Supercluster" title="Virgo Supercluster">Virgo Supercluster</a> <span style="font-size:120%">→</span> <a href="/wiki/Laniakea_Supercluster" title="Laniakea Supercluster">Laniakea Supercluster</a> <span style="font-size:120%">→</span> <a href="/wiki/Local_Hole" title="Local Hole">Local Hole</a> <span style="font-size:120%">→</span> <a class="mw-selflink selflink">Observable universe</a> <span style="font-size:120%">→</span> <a href="/wiki/Universe" title="Universe">Universe</a><br /><span style="font-size:85%;">Each arrow (<span style="font-size:120%">→</span>) may be read as "within" or "part of".</span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cosmic_View" title="Cosmic View"><i>Cosmic View</i> (1957 book)</a></li> <li><a href="/wiki/To_the_Moon_and_Beyond" title="To the Moon and Beyond"><i>To the Moon and Beyond</i> (1964 film)</a></li> <li><a href="/wiki/Cosmic_Zoom" title="Cosmic Zoom"><i>Cosmic Zoom</i> (1968 film)</a></li> <li><a href="/wiki/Powers_of_Ten_(film)" title="Powers of Ten (film)"><i>Powers of Ten</i> (1968 and 1977 films)</a></li> <li><a href="/wiki/Cosmic_Voyage_(1996_film)" title="Cosmic Voyage (1996 film)"><i>Cosmic Voyage</i> (1996 documentary)</a></li> <li><a href="/wiki/Cosmic_Eye" title="Cosmic Eye"><i>Cosmic Eye</i> (2012)</a></li> <li><a href="/wiki/History_of_the_center_of_the_Universe" title="History of the center of the Universe">History of the center of the Universe</a></li> <li><a href="/wiki/Order_of_magnitude" title="Order of magnitude">Order of magnitude</a></li> <li><a href="/wiki/Pisces%E2%80%93Cetus_Supercluster_Complex" title="Pisces–Cetus Supercluster Complex">Pisces–Cetus Supercluster Complex</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><b><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Symbol_portal_class.svg" class="mw-file-description" title="Portal"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/16px-Symbol_portal_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/23px-Symbol_portal_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/31px-Symbol_portal_class.svg.png 2x" data-file-width="180" data-file-height="185" /></a></span> <a href="/wiki/Portal:Astronomy" title="Portal:Astronomy">Astronomy portal</a></b></li> <li><b><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Symbol_portal_class.svg" class="mw-file-description" title="Portal"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/16px-Symbol_portal_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/23px-Symbol_portal_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/31px-Symbol_portal_class.svg.png 2x" data-file-width="180" data-file-height="185" /></a></span> <a href="/wiki/Portal:Space" class="mw-redirect" title="Portal:Space">Space portal</a></b></li></ul> </div></td></tr></tbody></table></div> <style data-mw-deduplicate="TemplateStyles:r1130092004">.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;justify-content:center;align-items:baseline}.mw-parser-output .portal-bar-bordered{padding:0 2em;background-color:#fdfdfd;border:1px solid #a2a9b1;clear:both;margin:1em auto 0}.mw-parser-output .portal-bar-related{font-size:100%;justify-content:flex-start}.mw-parser-output .portal-bar-unbordered{padding:0 1.7em;margin-left:0}.mw-parser-output .portal-bar-header{margin:0 1em 0 0.5em;flex:0 0 auto;min-height:24px}.mw-parser-output .portal-bar-content{display:flex;flex-flow:row wrap;flex:0 1 auto;padding:0.15em 0;column-gap:1em;align-items:baseline;margin:0;list-style:none}.mw-parser-output .portal-bar-content-related{margin:0;list-style:none}.mw-parser-output .portal-bar-item{display:inline-block;margin:0.15em 0.2em;min-height:24px;line-height:24px}@media screen and (max-width:768px){.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;flex-flow:column wrap;align-items:baseline}.mw-parser-output .portal-bar-header{text-align:center;flex:0;padding-left:0.5em;margin:0 auto}.mw-parser-output .portal-bar-related{font-size:100%;align-items:flex-start}.mw-parser-output .portal-bar-content{display:flex;flex-flow:row wrap;align-items:center;flex:0;column-gap:1em;border-top:1px solid #a2a9b1;margin:0 auto;list-style:none}.mw-parser-output .portal-bar-content-related{border-top:none;margin:0;list-style:none}}.mw-parser-output .navbox+link+.portal-bar,.mw-parser-output .navbox+style+.portal-bar,.mw-parser-output .navbox+link+.portal-bar-bordered,.mw-parser-output .navbox+style+.portal-bar-bordered,.mw-parser-output .sister-bar+link+.portal-bar,.mw-parser-output .sister-bar+style+.portal-bar,.mw-parser-output .portal-bar+.navbox-styles+.navbox,.mw-parser-output .portal-bar+.navbox-styles+.sister-bar{margin-top:-1px}</style><div class="portal-bar noprint metadata noviewer portal-bar-bordered" role="navigation" aria-label="Portals"><span class="portal-bar-header"><a href="/wiki/Wikipedia:Contents/Portals" title="Wikipedia:Contents/Portals">Portals</a>:</span><ul class="portal-bar-content"><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><a href="/wiki/File:He1523a.jpg" class="mw-file-description"><img alt="icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/16px-He1523a.jpg" decoding="async" width="16" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/25px-He1523a.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/33px-He1523a.jpg 2x" data-file-width="180" data-file-height="207" /></a></span> </span><a href="/wiki/Portal:Stars" title="Portal:Stars">Stars</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Earth-moon.jpg/21px-Earth-moon.jpg" decoding="async" width="21" height="17" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Earth-moon.jpg/32px-Earth-moon.jpg 1.5x, 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