A Model of the Cosmos

<!doctype html> <html lang="en" class="story-desktop ui-ie7 ui-ie"> <head prefix="og: https://ogp.me/ns# fb: https://ogp.me/ns/fb#"> <meta charset="utf-8"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <link rel="dns-prefetch" href="https://cdn.britannica.com/mendel-resources/3-130"> <link rel="preconnect" href="https://cdn.britannica.com/mendel-resources/3-130"> <link rel="preload" as="script" href="https://www.googletagservices.com/tag/js/gpt.js" /> <link rel="icon" href="/favicon.png" /> <meta name="description" content="What if the Earth was the size of a Ping-Pong ball?" /> <meta name="keywords" content="encyclopedia, britannica, encyclopedia britannica, list, lists, scale, model, universe, cosmos, solar system, space, astronomy" /> <link rel="canonical" href="https://www.britannica.com/story/a-model-of-the-cosmos" /> <title>A Model of the Cosmos | Britannica</title> <script type="text/javascript" data-type="Init Mendel"> window.$UI = {}; window.Constants = {"LICENSE_URL": "/bps/license","DEFAULT_TEST_VERSION": "A","DEFAULT_STATE": "XX","QUIZ_URL": "/quiz","SPOTLIGHT_BROWSE_URL": "/stories/spotlight","CONTENT_TYPE_TEXT": "text/plain;charset=UTF-8","TOPIC_FACTS_DATA_URL": "/facts","QUIZ_BROWSE_IMAGE_QUIZZES": "images","TOPIC_MEDIA_PATH": "/images-videos","USER_PROFILE_URL": "/user","DEBUG_URL": "/debug","ONE_GOOD_FACT_URL": "/one-good-fact","ERROR_404_URL": "/error404","PROCON_CITED_IN_THE_NEWS_URL": "/procon/ProCon-in-the-News","PROCON_URL": "/procon","TOPIC_PAGE_CONTENT_AJAX_URL": "/topic-content/page","INFINITE_SCROLL_PREFIX_URL": "/scroll","TOPIC_TOP_QUESTION_BROWSE_URL": "/questions","CC_USD": "USD","domain": "britannica.com","SURVEY_URL": "/survey","CATEGORY_BROWSE_URL": "/browse","STORY_BROWSE_URL": "/stories","COUNTRY_US": "US","OPEN_MEDIA_OVERLAY_PARAMETER": "/media","NEWSLETTER_SUBSCRIPTION_URL": "/newsletter-subscription","MAINTENANCE_ERROR_URL": "https://maintenance.eb.com","IMARS_EDITOR_ID": "12365882","PROFILE_EB_EDITOR_URL": "/editor","WEB_INF_RESOURCES_PATH": "WEB-INF/resources","AI_ABOUT_PAGE_URL": "/about-britannica-ai","TOPIC_ADDITIONAL_INFO_PATH": "/additional-info","SUDOKU_GAME_URL": "/games/sudoku","CC_INR": "INR","ARTICLE_PRINT_URL": "/print/article","FIRST_EDITION_URL": "/subscriber/firstedition","WW1_PORTAL_URL": "/discover/World-War-I","MENDEL_COOKIE": "__mendel","DEMYSTIFIED_BROWSE_URL": "/stories/demystified","LIST_BROWSE_URL": "/list/browse","PROFILE_EXPERT_URL": "/contributor","ASSEMBLY_IMAGE_URL": "/image/assembly","DAY_IN_HISTORY_URL": "/on-this-day","DEFAULT_CURRENCY": "USD","CONTENT_TYPE_XML": "text/xml;charset=UTF-8","PORTAL_FINANCE_BROWSE_URL_PREFIX": "/money/browse","MONEY_IMARS_CATEGORY": "13000","AJAX_PREFIX_URL": "/ajax","TOPIC_BROWSE_URL": "/topic-browse","MARKETING_CONTENT": "/marketing-content","ENV_RUNTIME": "runtime","GALLERY_URL": "/gallery","topicUrlClassesList": "topic|animal|art|biography|event|place|plant|science|sports|technology|procon","CONTENT_TYPE_HTML": "text/html;charset=UTF-8","ENV_LOCAL": "override","MEDIA_OVERLAY_URL": "/media-overlay","CHATBOT_PAGE_URL": "/chatbot","NEWSLETTER_PAGE_URL": "/newsletters","ENV_DEV": "development","MEDIA_URL": "/media","TOPIC_TOP_QUESTION_URL": "/question","PORTAL_FINANCE_URL_PREFIX": "/money","PODCASTS_URL": "/podcasts","STAND_ALONE_VIDEO_URL": "/video","MORE_ON_THIS_DAY_URL": "/more-on-this-day","TOPIC_QUOTES_URL": "/quotes","SEARCH_PAGE_URL": "/search","PROCON_CLASS": "PROCON","KUSTOM_MENDEL_APPLICATION_ID": "1","TOPIC_CONTENT_AJAX_URL": "/topic-content/topic","ENV_BRANCH": "branch","ERROR_URL": "/error","MAIN_VERSION": "mainVersion","DEFAULT_S3_REGION": "US_EAST_1","TOPIC_COLLECTION_URL": "/summary","LOGINBOX_URL": "/auth/loginbox","ONE_GOOD_FACT_BROWSE_URL": "/one-good-fact/all-good-facts","QUIZ_BROWSE_URL": "/quiz/browse","BIO_BROWSE_URL": "/browse/biographies","LIST_URL": "/list","TIGHTROPE_QUIZ_URL": "/quiz/tightrope","ALPHA_BROWSE_URL": "/sitemap","CONTENT_TYPE_JSON": "application/json","DICTIONARY_URL": "/dictionary","COBRAND_IMAGE_URL": "/image/cobrand","PROCON_IN_THE_NEWS_URL": "/procon/pro-and-con-issues-in-the-news","PROCON_BROWSE_URL": "/procon","QUIZ_BROWSE_VOCAB_QUIZZES": "vocabulary-quizzes","SUBMISSION_URL": "/submission","EB_LOG_OUT": "/auth2/logout","ENV_PRODUCTION": "production","EXPLORE_PORTAL_URL": "/explore","TOPIC_AJAX_URL": "/ajax/topic","TOPIC_SUMMARY_BROWSE_URL": "/summaries","WTFACT_BROWSE_URL": "/stories/wtfact","VIDEO_CHANNEL_URL": "/videos","GALLERY_BROWSE_URL": "/gallery/browse","CACHE_URL": "/cache","PROCON_ABOUT_URL": "/procon/About-ProCon","COMPANION_BROWSE_URL": "/stories/companion","MEDIA_FOLDER": "/eb-media","SHOW_ALL_CONTRIBUTORS": "/additional-info#contributors","BRITANNICA_EDITORS_ID": "4419","ENV_CACHE_DISABLED": "mendelCache","CALCULATORS_BROWSE_URL": "/calculators","STORY_URL": "/story","DEFAULT_COUNTRY": "US","NAVBAR_URL": "/ajax/navbar","EB_LOGIN_URL": "/auth/eb-login","NEW_ARTICLES_URL": "/new-articles",}; window.CDN = "https://cdn.britannica.com"; window.CAM_LOGIN_URL = "https://cam.britannica.com"; window.CAM_SIGN_UP_URL = "https://cam.britannica.com/registration" window.Mendel = { "config" : { "domain": "britannica.com", "page": "Story", "videoPlayerId": "UyMCoK2v", "sharedUrl": "https://www.britannica.com/story/a-model-of-the-cosmos", "amuselabsUrl": "https://cdn3.amuselabs.com", "resourcesPrefixUrl": "https://cdn.britannica.com/mendel-resources/3-130/[url]?v=3.130.14", "date": 20241201, "userInfo": { "type": "ANONYMOUS" ,"currency": "AUUS" ,"country": "SG" ,"state": "XX" ,"timezone": "Asia/Singapore" ,"bcomId": "-9027643150598735645" ,"hasAds": true ,"testVersion": "B" ,"adsTestVersion": "B" ,"consumerId": "" ,"instId": "" ,"consumerUserName": "" ,"instUserName": "" ,"cognito": null }, "tvs":{ "r":[25,25,25,25], "a": [25,25,25,25]}, "isLoggedInAsUser": false, "isPhone": false, "isDesktop": true, "logoutUrl": "/auth2/logout", "selfServiceUrl": "https://myaccount.britannica.com", "cdnUrl": "https://cdn.britannica.com", "chatbotApi": "https://www.britannica.com/chat-api", "fetchOffset": 800, "mendelCookieName": "__mendel", "mendelCookie": {"surveyShown":false,"visitedTopicId":0,"currentDate":20241201}, "autocompleteToSearchPage": false,"pagesInfo": [{"url":"a-model-of-the-cosmos","title":"A Model of the Cosmos"},{"url":"why-is-it-called-black-friday","title":"Why Is It Called Black Friday?"},{"url":"why-is-thanksgiving-in-the-us-celebrated-on-a-thursday","title":"Why Is Thanksgiving in the U.S. Celebrated on a Thursday?"},{"url":"why-do-we-eat-turkey-on-thanksgiving","title":"Why Do We Eat Turkey on Thanksgiving?"},{"url":"why-is-christmas-in-december","title":"Why Is Christmas in December?"},{"url":"thanksgiving-day-in-the-united-states","title":"Thanksgiving Day in the United States"},{"url":"why-is-the-mona-lisa-so-famous","title":"Why Is the <em>Mona Lisa</em> So Famous?"},{"url":"whats-the-difference-between-buffalo-and-bison","title":"What’s the Difference Between Bison and Buffalo?"},{"url":"was-martin-luther-king-jr-a-republican-or-a-democrat","title":"Was Martin Luther King, Jr., a Republican or a Democrat?"},{"url":"whats-the-difference-between-venomous-and-poisonous","title":"What’s the Difference Between Venomous and Poisonous?"},{"url":"are-bats-really-blind","title":"Are Bats Really Blind?"}] ,"currentFeature": 3780 ,"storyType": "WTFACT" }, "GA": {"leg":"B","adLeg":"B","userType":"ANONYMOUS","pageType":"Story","pageSubtype":"WTFACT","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} }; </script> <meta property="fb:app_id" content="1887621861548296"/ <meta name="twitter:card" content="summary_large_image" /> <meta name="twitter:site" content="@britannica" /> <meta name="twitter:image" content="https://cdn.britannica.com/51/157551-131-44092D74/Solar-system-illustration.jpg" /> <meta name="twitter:description" content="What if the Earth was the size of a Ping-Pong ball?"/> <meta property="og:type" content="ARTICLE"/> <meta property="og:title" content="A Model of the Cosmos | Britannica"/> <meta property="og:description" content="What if the Earth was the size of a Ping-Pong ball?"/> <meta property="og:site_name" content="Encyclopedia Britannica" /> <meta property="og:url" content="https://www.britannica.com/story/a-model-of-the-cosmos"/> <meta property="og:image" content="https://cdn.britannica.com/51/157551-131-44092D74/Solar-system-illustration.jpg" /> <meta property="og:image:type" content="image/jpeg" /> <script type="text/javascript" data-type="init opengraph"> Mendel.openGraph = {"type":"ARTICLE","title":"A Model of the Cosmos","description":"What if the Earth was the size of a Ping-Pong ball?","imageUrl":"https://cdn.britannica.com/51/157551-131-44092D74/Solar-system-illustration.jpg","imageType":"image/jpeg","pageUrl":"https://www.britannica.com/story/a-model-of-the-cosmos"}</script> <link rel="preconnect" href="https://fonts.googleapis.com/"> <link rel="dns-prefetch" href="https://fonts.googleapis.com/" > <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons"> <link href="https://cdn.britannica.com/mendel-resources/3-130/dist/vendor-bundle.css?v=3.130.14" rel="stylesheet" /> <link href="https://cdn.britannica.com/mendel-resources/3-130/dist/mendel-css.css?v=3.130.14" rel="stylesheet" /> <link href="https://cdn.britannica.com/mendel-resources/3-130/dist/story-page.css?v=3.130.14" rel="stylesheet" /> <script type="text/javascript"> if (self !== top) { top.location = self.location; } // if ('scrollRestoration' in history) { history.scrollRestoration = 'manual'; } </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/at.js?v=3.130.14" async ></script> <script> dataLayer = []; </script> <script type="text/javascript">(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src= '//www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f); })(window,document,'script','dataLayer','GTM-5W6NC8'); </script> </head> <body data-leg="B" class="popular-topics-story user-ANONYMOUS user-ads md-desktop leg-bb-ie">  <script>Mendel.config.adProvider='ay';</script> <script async src="https://securepubads.g.doubleclick.net/tag/js/gpt.js"></script> <script> window.googletag = window.googletag || {cmd: []}; googletag.cmd.push(function() { googletag.defineSlot('/15510053/CMP_1x1', [1, 1], 'div-gpt-ad-1709766812090-0').addService(googletag.pubads()); googletag.pubads().enableSingleRequest(); googletag.enableServices(); }); </script> <script async defer src="https://launchpad-wrapper.privacymanager.io/0ccc6fe8-1870-4ad8-b47b-6d029ac116fc/launchpad-liveramp.js"></script> <script async src="https://JRyhoywLYXNLYMAhs.ay.delivery/manager/JRyhoywLYXNLYMAhs" type="text/javascript" referrerpolicy="no-referrer-when-downgrade" ></script><div class="ie-warning d-flex align-items-center align-self-center justify-content-center site-alert bg-orange"> <div> You are using an <strong>outdated</strong> browser. Please <a class="text-white text-underscore" href="https://browsehappy.com/">upgrade your browser</a> to improve your experience and security. </div> </div> <script id="json-navbar-info" type="application/json"> {"topSectionLinks":[{"title":"Ask the Chatbot","url":"/chatbot","navbarId":"CHATBOT"},{"title":"Games & Quizzes","url":"/quiz/browse","navbarId":"QUIZZES"},{"title":"ProCon","url":"/procon","navbarId":"PROCON"},{"title":"History & Society","url":"/History-Society","navbarId":"HISTORY"},{"title":"Science & Tech","url":"/Science-Tech","selected":true,"navbarId":"SCIENCE"},{"title":"Biographies","url":"/Biographies","navbarId":"BIOS"},{"title":"Animals & Nature","url":"/Animals-Nature","navbarId":"ANIMALS"},{"title":"Geography & Travel","url":"/Geography-Travel","navbarId":"GEOGRAPHY"},{"title":"Arts & Culture","url":"/Arts-Culture","navbarId":"ART"},{"title":"Money","url":"/money","navbarId":"MONEY"},{"title":"Videos","url":"/videos","navbarId":"VIDEOS"}],"selectedSuperCategory":{"id":6,"title":"Science & Tech","url":"Science-Tech","description":"Explore science and technology; astronomy; biology; chemistry; earth science; mathematics; physics; technology, agriculture, cars, computers, engineering, industry, inventions, communication","keywords":"astronomy; biology; chemistry; earth science; mathematics; physics; technology, agriculture, cars, computers, engineering, industry, inventions, communication","classId":"SCIENCE","sortOrder":2},"selectedNavbarLink":{"title":"Science & Tech","url":"/Science-Tech","selected":true,"navbarId":"SCIENCE"}} </script> <script id="json-hamburger-menu" type="application/json"> {"britannicaMenu1":[{"title":"Home","url":"/"},{"title":"ProCon","url":"/procon"},{"title":"History & Society","url":"/History-Society"},{"title":"Science & Tech","url":"/Science-Tech"},{"title":"Biographies","url":"/Biographies"},{"title":"Animals & Nature","url":"/Animals-Nature"},{"title":"Geography & Travel","url":"/Geography-Travel"},{"title":"Arts & Culture","url":"/Arts-Culture"},{"title":"Money","url":"/money"}],"britannicaMenu2":[{"title":"Games & Quizzes","url":"/quiz/browse"},{"title":"Videos","url":"/videos"},{"title":"On This Day","url":"/on-this-day"},{"title":"One Good Fact","url":"/one-good-fact"},{"title":"Dictionary","url":"/dictionary"},{"title":"New Articles","url":"/new-articles"}],"browseByCategory":[{"title":{"id":5,"title":"History & Society","url":"/History-Society"},"links":[{"title":"Lifestyles & Social Issues","url":"/browse/Lifestyles-Social-Issues"},{"title":"Philosophy & Religion","url":"/browse/Philosophy-Religion"},{"title":"Politics, Law & Government","url":"/browse/Politics-Law-Government"},{"title":"World History","url":"/browse/World-History"}]},{"title":{"id":6,"title":"Science & Tech","url":"/Science-Tech"},"links":[{"title":"Health & Medicine","url":"/browse/Health-Medicine"},{"title":"Science","url":"/browse/Science"},{"title":"Technology","url":"/browse/Technology"}]},{"title":{"id":3,"title":"Biographies","url":"/Biographies"},"links":[{"title":"Browse Biographies","url":"/browse/biographies"}]},{"title":{"id":1,"title":"Animals & Nature","url":"/Animals-Nature"},"links":[{"title":"Birds, Reptiles & Other Vertebrates","url":"/browse/Birds-Reptiles-Vertebrates"},{"title":"Bugs, Mollusks & Other Invertebrates","url":"/browse/Bugs-Mollusks-Invertebrates"},{"title":"Environment","url":"/browse/Environment"},{"title":"Fossils & Geologic Time","url":"/browse/Fossil-Geologic-Time"},{"title":"Mammals","url":"/browse/Mammals"},{"title":"Plants","url":"/browse/Plants"}]},{"title":{"id":4,"title":"Geography & Travel","url":"/Geography-Travel"},"links":[{"title":"Geography & Travel","url":"/browse/Geography-Travel"}]},{"title":{"id":2,"title":"Arts & Culture","url":"/Arts-Culture"},"links":[{"title":"Entertainment & Pop Culture","url":"/browse/Entertainment-Pop-Culture"},{"title":"Literature","url":"/browse/Literature"},{"title":"Sports & Recreation","url":"/browse/Sports-Recreation"},{"title":"Visual Arts","url":"/browse/Visual-Arts"}]}],"browseByFeature":[{"title":"Companions","url":"/stories/companion"},{"title":"Demystified","url":"/stories/demystified"},{"title":"Image Galleries","url":"/gallery/browse"},{"title":"Lists","url":"/list/browse"},{"title":"Podcasts","url":"/podcasts"},{"title":"Spotlight","url":"/stories/spotlight"},{"title":"Summaries","url":"/summary"},{"title":"The Forum","url":"/stories/the-forum"},{"title":"Top Questions","url":"/question"},{"title":"#WTFact","url":"/stories/wtfact"}],"moreFromBritannica":[{"title":"Britannica Kids","url":"https://kids.britannica.com/","newTab":true}],"menuType":"DEFAULT"} </script> <header id="header" class="bg-navy-dark"> <div class="global-nav-top-bar"> <div class="grid gx-0 h-100 justify-content-between align-items-center container-lg mx-auto p-0 position-relative"> <div class="d-flex align-items-center"> <button class="d-flex align-items-center justify-self-start js-toggle js-toggle-hamburger btn btn-link link-white btn-sm rounded-0 p-10"> <div class="hamburger-tooltip"> <em class="material-icons d-inline-block font-24" id="nav-toggle" data-icon="menu"></em> </div> <em class="material-icons d-inline-block font-24 global-nav-search-icon" id="nav-search-icon" data-icon="search" ></em> </button> <a href="/" class="d-flex align-items-center justify-content-center ml-10"> <img loading="lazy" src="https://cdn.britannica.com/mendel/eb-logo/MendelNewThistleLogo.png" alt="Encyclopedia Britannica" class="global-nav-logo global-nav-logo-left" /> </a> <div class="global-nav-top-search-bar global-nav-top-search-container global-nav-search-container" id="global-nav-top-search-bar"> <form method="get" action="/search" id="global-nav-search" class="md-search-form m-0 global-nav-search-bar-small"> <div class="search-box position-relative col-100"> <label class="sr-only" for="global-nav-search-query">Search Britannica</label> <input name="query" id="global-nav-search-query" placeholder="Search Britannica..." class="form-control form-control-lg rounded-lg font-16 search-query pl-20 pr-70 shadow-sm" maxlength="200" autocomplete="off" aria-label="Search Britannica" /> <button class="search-reset-btn btn btn-link px-10 position-absolute top-0 h-100 d-none" type="reset"> <em class="material-icons" data-icon="close"></em> </button> <button class="search-submit btn btn-link text-blue px-10 position-absolute top-0 right-0 h-100" type="submit" disabled> <span class="sr-only">Click here to search</span> <em class="material-icons search-icon" data-icon="search"></em> </button> </div> </form> </div> </div> <a href="/" class="d-flex align-items-center justify-content-center"> <img loading="lazy" src="https://cdn.britannica.com/mendel/eb-logo/MendelNewThistleLogo.png" alt="Encyclopedia Britannica" class="global-nav-center global-nav-logo non-homepage-logo" /> </a> <form method="get" action="/search" id="global-nav-search" class="md-search-form m-0 global-nav-search-bar-small global-nav-center search global-nav-center-search-container"> <div class="search-box position-relative col-100"> <label class="sr-only" for="global-nav-search-query">Search Britannica</label> <input name="query" id="global-nav-search-query" placeholder="Search Britannica..." class="form-control form-control-lg rounded-lg font-16 search-query pl-20 pr-70 shadow-sm" maxlength="200" autocomplete="off" aria-label="Search Britannica" /> <button class="search-reset-btn btn btn-link px-10 position-absolute top-0 h-100 d-none" type="reset"> <em class="material-icons" data-icon="close"></em> </button> <button class="search-submit btn btn-link text-blue px-10 position-absolute top-0 right-0 h-100" type="submit" disabled> <span class="sr-only">Click here to search</span> <em class="material-icons search-icon" data-icon="search"></em> </button> </div> </form> <div class="col-35 col-sm-auto text-right order-3 mr-lg-15 align-items-center d-flex justify-content-end"> <div class="d-none d-md-inline-block"> <SPAN class="marketing-HEADER_SUBSCRIPTION_DESKTOP2 marketing-content" data-marketing-id="HEADER_SUBSCRIPTION_DESKTOP2"><a href="https://subscription.britannica.com/subscribe?partnerCode=BP_Black_Friday_AUUS" class="subscribe-link btn btn-sm btn-outline-white-orange py-5 mr-10" target="_blank" rel="noopener"> Subscribe </a></SPAN></div> <div class="d-inline-block d-md-none mr-5 mr-sm-10"> <SPAN class="marketing-HEADER_SUBSCRIPTION_MOBILE marketing-content" data-marketing-id="HEADER_SUBSCRIPTION_MOBILE"><a href="https://subscription.britannica.com/subscribe?partnerCode=BP_Black_Friday_AUUS" class="subscribe-link btn btn-xs btn-orange-dark p-5" target="_blank" rel="noopener"> Subscribe </a></SPAN></div> <button class="js-toggle-user-dropdown js-toggle btn btn-sm btn-link link-white rounded-0 px-md-15 pl-5 pr-5"> <span class="d-none d-md-inline-block mr-5">Login</span> <em class="material-icons d-inline-block d-md-none font-16 font-sm-20" data-icon="account_circle"></em> <div class="d-none dropdown-menu-subscription-link">https://subscription.britannica.com/subscribe?partnerCode=BP_Black_Friday_AUUS</div> <em class="material-icons inactive-icon d-inline-block font-18" data-icon="keyboard_arrow_down"></em> <em class="material-icons active-icon d-inline-block font-18" data-icon="keyboard_arrow_up"></em> </button> </div> </div> </div> <div class="d-none hamburger-menu-subscription-link"><DIV class="marketing-HAMBURGER_MENU_CTA marketing-content" data-marketing-id="HAMBURGER_MENU_CTA"><a href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=hamburger-menu&utm_campaign=black-friday-2024" class="subscribe-link btn btn-sm btn-orange py-5" target="_blank"> Subscribe <span class="d-none d-md-inline"> Now</span> </a></DIV></div> <div id="global-nav-react"> <div class="d-none"> <ul> <li><a href="/">Home</a></li> <li><a href="/procon">ProCon</a></li> <li><a href="/History-Society">History & Society</a></li> <li><a href="/Science-Tech">Science & Tech</a></li> <li><a href="/Biographies">Biographies</a></li> <li><a href="/Animals-Nature">Animals & Nature</a></li> <li><a href="/Geography-Travel">Geography & Travel</a></li> <li><a href="/Arts-Culture">Arts & Culture</a></li> <li><a href="/money">Money</a></li> </ul> <ul> <li><a href="/quiz/browse">Games & Quizzes</a></li> <li><a href="/videos">Videos</a></li> <li><a href="/on-this-day">On This Day</a></li> <li><a href="/one-good-fact">One Good Fact</a></li> <li><a href="/dictionary">Dictionary</a></li> <li><a href="/new-articles">New Articles</a></li> </ul> <a href="/History-Society">History & Society</a> <ul> <li><a href="/browse/Lifestyles-Social-Issues">Lifestyles & Social Issues</a></li> <li><a href="/browse/Philosophy-Religion">Philosophy & Religion</a></li> <li><a href="/browse/Politics-Law-Government">Politics, Law & Government</a></li> <li><a href="/browse/World-History">World History</a></li> </ul> <a href="/Science-Tech">Science & Tech</a> <ul> <li><a href="/browse/Health-Medicine">Health & Medicine</a></li> <li><a href="/browse/Science">Science</a></li> <li><a href="/browse/Technology">Technology</a></li> </ul> <a href="/Biographies">Biographies</a> <ul> <li><a href="/browse/biographies">Browse Biographies</a></li> </ul> <a href="/Animals-Nature">Animals & Nature</a> <ul> <li><a href="/browse/Birds-Reptiles-Vertebrates">Birds, Reptiles & Other Vertebrates</a></li> <li><a href="/browse/Bugs-Mollusks-Invertebrates">Bugs, Mollusks & Other Invertebrates</a></li> <li><a href="/browse/Environment">Environment</a></li> <li><a href="/browse/Fossil-Geologic-Time">Fossils & Geologic Time</a></li> <li><a href="/browse/Mammals">Mammals</a></li> <li><a href="/browse/Plants">Plants</a></li> </ul> <a href="/Geography-Travel">Geography & Travel</a> <ul> <li><a href="/browse/Geography-Travel">Geography & Travel</a></li> </ul> <a href="/Arts-Culture">Arts & Culture</a> <ul> <li><a href="/browse/Entertainment-Pop-Culture">Entertainment & Pop Culture</a></li> <li><a href="/browse/Literature">Literature</a></li> <li><a href="/browse/Sports-Recreation">Sports & Recreation</a></li> <li><a href="/browse/Visual-Arts">Visual Arts</a></li> </ul> <ul> <li><a href="/stories/companion">Companions</a></li> <li><a href="/stories/demystified">Demystified</a></li> <li><a href="/gallery/browse">Image Galleries</a></li> <li><a href="/list/browse">Lists</a></li> <li><a href="/podcasts">Podcasts</a></li> <li><a href="/stories/spotlight">Spotlight</a></li> <li><a href="/summary">Summaries</a></li> <li><a href="/stories/the-forum">The Forum</a></li> <li><a href="/question">Top Questions</a></li> <li><a href="/stories/wtfact">#WTFact</a></li> </ul> <ul> <li><a href="https://kids.britannica.com/">Britannica Kids</a></li> </ul> </div> </div> </header> <div class="bg-navy-dark"> <div class="container-lg p-0 d-flex justify-content-center global-nav-categories-bar overflow-hidden"> <div class="slider js-slider position-relative d-inline-flex align-items-center mw-100 global-nav-slider category-snap-slider"> <div class="slider-container js-slider-container overflow-hidden d-flex font-14 overflow-hidden text-nowrap mx-5"> <a class="nav-bar-category mx-5 category-link-CHATBOT " href="/chatbot">Ask the Chatbot</a> <a class="nav-bar-category mx-5 category-link-QUIZZES " href="/quiz/browse">Games & Quizzes</a> <a class="nav-bar-category mx-5 category-link-PROCON " href="/procon">ProCon</a> <a class="nav-bar-category mx-5 category-link-HISTORY " href="/History-Society">History & Society</a> <a class="nav-bar-category mx-5 category-link-SCIENCE selected selected" href="/Science-Tech">Science & Tech</a> <a class="nav-bar-category mx-5 category-link-BIOS " href="/Biographies">Biographies</a> <a class="nav-bar-category mx-5 category-link-ANIMALS " href="/Animals-Nature">Animals & Nature</a> <a class="nav-bar-category mx-5 category-link-GEOGRAPHY " href="/Geography-Travel">Geography & Travel</a> <a class="nav-bar-category mx-5 category-link-ART " href="/Arts-Culture">Arts & Culture</a> <a class="nav-bar-category mx-5 category-link-MONEY " href="/money">Money</a> <a class="nav-bar-category mx-5 category-link-VIDEOS " href="/videos">Videos</a> </div> <button disabled class="prev-button js-prev-button position-absolute btn btn-circle shadow btn-blue " aria-label="Previous"> <span class="material-icons md-24" data-icon="keyboard_arrow_left"></span> </button> <button disabled class="next-button js-next-button position-absolute btn btn-circle shadow btn-blue " aria-label="Next"> <span class="material-icons md-24" data-icon="keyboard_arrow_right"></span> </button> </div> </div> </div> <main> <div class="md-page-wrapper"> <div id="content" class="md-content"> <script type="application/ld+json"> {"headline":"A Model of the Cosmos","image":{"url":"https://cdn.britannica.com/51/157551-131-44092D74/Solar-system-illustration.jpg","@type":"ImageObject"},"author":[{"name":"Terrence Jacobs","url":"https://www.britannica.com/contributor/Terrence-Jacobs/9471798","@type":"Person"}],"keywords":"A Model of the Cosmos","url":"https://www.britannica.com/story/a-model-of-the-cosmos","description":"What if the Earth was the size of a Ping-Pong ball?","publisher":{"logo":{"url":"https://corporate.britannica.com/wp-content/themes/eb-corporate/_img/logo.png","@type":"ImageObject"},"name":"Encyclopedia Britannica","@type":"Organization"},"@context":"https://schema.org","@type":"article"} </script> <main id="story-container" class="WTFACT"> <div class="story-content"> <div class="story-content story-container qa-content" data-bc-category="Science" data-feature-id="3780"> <div class="md-article-container"> <div class="feature-container container-lg p-0 pb-40 p-md-20"> <aside class="d-none d-lg-block feature-left-rail p-20 pb-60 clear-catfish-ad"> <div class="feature-section"> <div class="label mb-15 font-serif">Discover</div> <div class="mobile-carousel-items"> <ul class="pl-0 lr-image-list font-14 m-0 mb-30 d-flex flex-md-column slider-container js-slider-container overflow-hidden discover"> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/quiz/27-true-or-false-questions-from-britannicas-most-difficult-science-quizzes" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg?w=68&h=68&s=crop" alt="Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph." /> </a> <div class="link-container"> <a class="" href="/quiz/27-true-or-false-questions-from-britannicas-most-difficult-science-quizzes">27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/quiz/exploring-earth-fact-or-fiction" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/40/157740-131-DD5F3B63/Planet-Earth-section-illustration-background.jpg?w=68&h=68&s=crop" alt="Planet Earth section illustration on white background." /> </a> <div class="link-container"> <a class="" href="/quiz/exploring-earth-fact-or-fiction">Exploring Earth: Fact or Fiction?</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/story/a-doorway-on-mars-how-we-see-things-in-space-that-arentthere" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/56/222356-131-19F4FC94/geography-travel-health-medicine-science-technology.jpg?w=68&h=68&s=crop" alt="Mendel third-party content placeholder. Categories: Geography & Travel, Health & Medicine, Technology, and Science" /> </a> <div class="link-container"> <a class="" href="/story/a-doorway-on-mars-how-we-see-things-in-space-that-arentthere">A ‘doorway’ on Mars? How we see things in space that aren’t there</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/list/7-important-dates-in-mercury-history" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/89/186789-131-1A5BC9A1/Planet-Mercury-spacecraft-MESSENGER-Colors-images-color.jpg?w=68&h=68&s=crop" alt="Planet Mercury photographed by the MESSENGER spacecraft. Colors produced by images from color base map imaging. Colors are not what Mercury looks to human eye. See NOTES:" /> </a> <div class="link-container"> <a class="" href="/list/7-important-dates-in-mercury-history">7 Important Dates in Mercury History</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/quiz/everything-in-space-in-25-minutes" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/45/111345-131-71FE3796/Pinwheel-Galaxy-image-Hubble-Space-Telescope.jpg?w=68&h=68&s=crop" alt="M101 (NGC 5457, The Pinwheel Galaxy). Hubble Space Telescope image of face-on spiral galaxy Messier 101 (M101). Largest most detailed photo of a spiral galaxy that has ever been released from Hubble. Created from 1994-2003" /> </a> <div class="link-container"> <a class="" href="/quiz/everything-in-space-in-25-minutes">Everything in Space in a 25-Minute Quiz</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/quiz/climate-change-fact-or-fiction" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/57/150357-131-B933CFBD/lightning-discharge-field-cumulonimbus-cloud.jpg?w=68&h=68&s=crop" alt="Thunderstorm cloud-to-ground lightning discharge with cumulonimbus clouds in field. weather storm thunderstorm atmospheric disturbance cumulonimbus clouds thunder and lightning Homepage blog 2011, science and technology" /> </a> <div class="link-container"> <a class="" href="/quiz/climate-change-fact-or-fiction">Climate Change: Fact or Fiction?</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/story/new-space-race-map-and-timeline-infographic" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/10/211710-050-01CEC2D8/new-space-race-China-India-Japan-timeline.jpg?w=68&h=68&s=crop" alt="New space race infographic between China, India, and Japan. Asian space race, space exploration" /> </a> <div class="link-container"> <a class="" href="/story/new-space-race-map-and-timeline-infographic">The New Space Race</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/story/whats-the-difference-between-buffalo-and-bison" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/04/187404-131-2839AF60/bison-American-buffalo-plains-prairie.jpg?w=68&h=68&s=crop" alt="American bison (Bison bison) also known as buffalo or plains buffalo on the prairie, western U.S." /> </a> <div class="link-container"> <a class="" href="/story/whats-the-difference-between-buffalo-and-bison">What’s the Difference Between Bison and Buffalo?</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/list/10-best-sports-rivalries-of-all-time" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/53/189653-131-A7E9422A/Kevin-Garnett-shooting-Ronny-Turiaf-Boston-Celtics-2008.jpg?w=68&h=68&s=crop" alt="NBA Lakers Celtics Finals Kevin Garnett shooting." /> </a> <div class="link-container"> <a class="" href="/list/10-best-sports-rivalries-of-all-time">10 Great Sports Rivalries</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/story/thanksgiving-day-in-the-united-states" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/06/187306-131-1D18F8C1/cornucopia-pumpkins-gords-leaf.jpg?w=68&h=68&s=crop" alt="autumn, fall, pumpkins, cornucopia, gords, thanksgiving, leaf" /> </a> <div class="link-container"> <a class="" href="/story/thanksgiving-day-in-the-united-states">Thanksgiving Day in the United States</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/story/was-martin-luther-king-jr-a-republican-or-a-democrat" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/57/203257-131-48B2BCA1/Martin-Luther-King-Jr-marchers-speech-I-August-28th-1963.jpg?w=68&h=68&s=crop" alt="Dr. Martin Luther King Jr. addresses marchers during his "I Have a Dream" speech at the Lincoln Memorial in Washington. August 28th 1963" /> </a> <div class="link-container"> <a class="" href="/story/was-martin-luther-king-jr-a-republican-or-a-democrat">Was Martin Luther King, Jr., a Republican or a Democrat?</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/list/9-noteworthy-bog-bodies-and-what-they-tell-us" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/68/178968-131-ADEF94E7/bog-body-Head-Tollund-Man-Human-remains-1950.jpg?w=68&h=68&s=crop" alt="Bog body. Head of Tollund Man. Died at about age 30-40, Dated to about 280 BCE early Iron Age. Found Bjaeldskovdal bog Denmark in 1950 near Elling Woman. Most well preserved bog body to date. Human remains mummified in natural peat bogs. mummy, embalm" /> </a> <div class="link-container"> <a class="" href="/list/9-noteworthy-bog-bodies-and-what-they-tell-us">9 Noteworthy Bog Bodies (And What They Tell Us)</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/list/7-of-the-worlds-deadliest-shipwrecks" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/41/182141-131-32BD2459/Lusitania-sinking-U-boat-German-May-1915.jpg?w=68&h=68&s=crop" alt="Lusitania sinking, illustration from The War of the Nations (New York), December 31, 1919. World War I, WWI. This image is one of three on the page. (See source file for the other two.)" /> </a> <div class="link-container"> <a class="" href="/list/7-of-the-worlds-deadliest-shipwrecks">7 of the World’s Deadliest Shipwrecks</a> </div> <div class="item-separator d-md-none"></div> </li> <li class="mb-10 mr-10 mr-md-0 d-inline-flex"> <a href="/list/9-of-the-worlds-deadliest-spiders" class="d-block mr-10"> <img loading="lazy" src="https://cdn.britannica.com/70/62770-131-C97CD1F7/Black-widow-spider.jpg?w=68&h=68&s=crop" alt="Black widow spider" /> </a> <div class="link-container"> <a class="" href="/list/9-of-the-worlds-deadliest-spiders">9 of the World’s Deadliest Spiders</a> </div> </li> </ul> </div> </div> </aside> <div class="reading-channel"> <div class="grey-box w-100 grey-box-middle"> <div class="grey-box-content mx-auto w-100"> <script type="application/ld+json"> { "@context" : "https://schema.org", "@type" : "BreadcrumbList", "itemListElement" : [ { "@type" : "ListItem", "position" : 1, "item" : { "@id" : "https://www.britannica.com/stories/wtfact", "name": "#WTFact" } } , { "@type" : "ListItem", "position" : 2, "item" : { "@id" : "https://www.britannica.com/stories/wtfact/Science", "name": "Science" } } ] } </script> <nav class="breadcrumb mt-20 mb-30"> <span class="breadcrumb-item "> <a href="/" class="link-gray-600">Home</a> </span> <span class="breadcrumb-item "> <a class="link-gray-600" href="/stories/wtfact">#WTFact</a> </span> <span class="breadcrumb-item "> <a class="link-gray-600" href="/stories/wtfact/Science">Science</a> </span> </nav> <div class="mb-5"> <a class="SCIENCE font-weight-semi-bold super-category-badge rounded font-14" href="/Science-Tech"> Science & Tech </a> </div> <div> <div class="d-block d-md-none md-feature-tools float-right mb-15" style="right:20px" data-feature-id="3780"> <button class="js-tooltip-actions ml-10 btn btn-xs btn-outline-blue border shadow-sm pr-10" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="more_vert"></em> Actions </button> <div class="md-actions-popover popover popover-sm py-5 px-0 dropdown-menu"> <div> <button class="js-modal qa-cite-modal-button btn btn-sm btn-link gtm-topic-tool " data-modal="[data-feature-id=3780] .sm-cite-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="verified"></em> Cite </button> <div class="sm-cite-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif d-flex align-items-center pb-15 border-bottom mb-15"> <em class="material-icons text-blue mr-10">verified</em>Cite </div> <div class="font-serif"> While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. </div> <div class="label mt-20 mb-10">Select Citation Style</div> <select class="js-citation-format-select form-select"> <option selected value="mla">MLA</option> <option value="apa">APA</option> <option value="chicago">Chicago Manual of Style</option> </select> <div class="citation font-serif border rounded p-15 mt-20" data-authors="Terrence Jacobs" data-title="A Model of the Cosmos" data-published-date="24 Mar. 2023" data-url="https://www.britannica.com/story/a-model-of-the-cosmos" > <div class="citation-text"></div> </div> <button class="js-copy-citation-button mt-20 btn btn-xs btn-outline-blue border shadow-sm pr-10" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="file_copy"></em> <span class="js-citation-status-text">Copy Citation</span> </button> </div> </div> </div> <div> <button class="js-share-modal-button js-modal btn btn-sm btn-link gtm-topic-tool " data-modal="[data-feature-id=3780] .md-share-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="share"></em> Share </button> <div class="md-share-modal size-lg d-none qa-share-modal"> <div class="md-modal-body"> <div class="h2 font-serif d-flex align-items-center pb-15 border-bottom"> <em class="material-icons text-blue mr-10" data-icon="share"></em> Share </div> <div class="label my-20">Share to social media</div> <div class="md-social-toolbar-circle d-flex align-items-start inverted" data-value="share" title="A Model of the Cosmos" data-url="https://www.britannica.com/story/a-model-of-the-cosmos" > <a class="social-icon facebook justify-content-center d-flex align-items-center align-self-center" data-provider="facebook" href="https://www.facebook.com/BRITANNICA/" target="_blank" rel="noopener"><span>Facebook</span></a> <a class="social-icon x justify-content-center d-flex align-items-center align-self-center" data-provider="x" href="https://x.com/britannica" target="_blank" rel="noopener"><span>X</span></a> </div> <div class="label pt-20 mt-20 mb-5 border-top">URL</div> <a class="font-serif text-truncate d-inline-block" href="https://www.britannica.com/story/a-model-of-the-cosmos">https://www.britannica.com/story/a-model-of-the-cosmos</a> </div> </div> </div> </div> </div> <h1 class="mb-5">A Model of the Cosmos</h1> <div class="d-none d-md-flex my-15"> <div class="mr-5"> <a href="javascript:window.print()" class=" btn btn-xs btn-outline-blue border shadow-sm pr-10" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="print"></em> Print </a> </div> <div class="mr-5"> <button class="js-modal qa-cite-modal-button gtm-topic-tool btn btn-xs btn-outline-blue border shadow-sm pr-10" data-modal="[data-feature-id=3780] .md-cite-modal"> <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="verified"></em> Cite </button> <div class="md-cite-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif d-flex align-items-center pb-15 border-bottom mb-15"> <em class="material-icons text-blue mr-10">verified</em>Cite </div> <div class="font-serif"> While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. </div> <div class="label mt-20 mb-10">Select Citation Style</div> <select class="js-citation-format-select form-select"> <option selected value="mla">MLA</option> <option value="apa">APA</option> <option value="chicago">Chicago Manual of Style</option> </select> <div class="citation font-serif border rounded p-15 mt-20" data-authors="Terrence Jacobs" data-title="A Model of the Cosmos" data-published-date="24 Mar. 2023" data-url="https://www.britannica.com/story/a-model-of-the-cosmos" > <div class="citation-text"></div> </div> <button class="js-copy-citation-button mt-20 btn btn-xs btn-outline-blue border shadow-sm pr-10" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="file_copy"></em> <span class="js-citation-status-text">Copy Citation</span> </button> </div> </div> </div> <div> <button class="js-share-modal-button js-modal gtm-topic-tool btn btn-xs btn-outline-blue border shadow-sm pr-10" data-modal=".md-share-modal"> <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="share"></em> Share </button> <div class="md-share-modal size-lg d-none qa-share-modal"> <div class="md-modal-body"> <div class="h2 font-serif d-flex align-items-center pb-15 border-bottom"> <em class="material-icons text-blue mr-10" data-icon="share"></em> Share </div> <div class="label my-20">Share to social media</div> <div class="md-social-toolbar-circle d-flex align-items-start inverted" data-value="share" title="A Model of the Cosmos" data-url="https://www.britannica.com/story/a-model-of-the-cosmos" > <a class="social-icon facebook justify-content-center d-flex align-items-center align-self-center" data-provider="facebook" href="https://www.facebook.com/BRITANNICA/" target="_blank" rel="noopener"><span>Facebook</span></a> <a class="social-icon x justify-content-center d-flex align-items-center align-self-center" data-provider="x" href="https://x.com/britannica" target="_blank" rel="noopener"><span>X</span></a> </div> <div class="label pt-20 mt-20 mb-5 border-top">URL</div> <a class="font-serif text-truncate d-inline-block" href="https://www.britannica.com/story/a-model-of-the-cosmos">https://www.britannica.com/story/a-model-of-the-cosmos</a> </div> </div> </div> </div> <div class="md-byline module-spacing font-12"> <div class="font-serif font-12"> <span class="written-by text-gray-700"> Written by </span> <div class="editor-popover popover p-0"> <a class="d-block p-20 gtm-byline font-12 byline-contributor" href="/contributor/Terrence-Jacobs/9471798" > <div class="editor-title font-16 font-weight-bold">Terrence Jacobs</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Contributor to Britannica.com</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Terrence Jacobs</span></div> <div class="font-serif font-12 text-gray-700"> <span class="qa-fact-checked-by">Fact-checked by</span> <div class="editor-popover popover p-0"> <a class="d-block p-20 font-12" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div></div> </div> <article class="topic-content content"><div class="topic-paragraph font-serif md-list-intro pt-15 pb-20"><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/51/157551-131-44092D74/Solar-system-illustration.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*0"><img src="https://cdn.britannica.com/51/157551-131-44092D74/Solar-system-illustration.jpg?w=1000" alt="Solar system illustration. (Sun; planets)" data-width="900" data-height="675" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span></span></div><cite class="credit d-block mt-5">© matamu/Fotolia</cite></figcaption></figure><p class="topic-paragraph">Sometimes it’s hard to get a handle on the vastness of the universe. How far is an astronomical unit, anyhow? In this list we’ve brought the universe down to a more manageable scale.</p><span class="MOD"></span></div><ul class="md-list-order-reverse md-mendel-list" style="counter-reset: item 15"><li><h2>Earth</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/79/92879-050-578C3D92/spacecraft-Astronauts-Apollo-17-image-Earth-Moon-1972.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*97341"><img src="https://cdn.britannica.com/79/92879-050-578C3D92/spacecraft-Astronauts-Apollo-17-image-Earth-Moon-1972.jpg?w=1000" alt="View of the Earth as seen by the Apollo 17 crew traveling toward the moon, 1972. This image and others like it captured whole hemispheres of water, land and weather. This photo was the first view of the south polar ice cap. Blue Marble 1972." data-width="1600" data-height="1322" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/79/92879-050-578C3D92/spacecraft-Astronauts-Apollo-17-image-Earth-Moon-1972.jpg" data-href="*97341">Earth</a><span>The planet Earth.</span></span></div><cite class="credit d-block mt-5">NASA</cite></figcaption></figure><p class="topic-paragraph">The universe is a big place, but let’s cut it down to size by making the Earth the size of a Ping-Pong ball. On that scale it would be placed 500 yards (460 meters) from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-1"></span></li><li><h2>Sun</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/19/73319-050-065E4F9B/Sun-ultraviolet-light-satellite-Earth-Solar-and.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*68803"><img src="https://cdn.britannica.com/19/73319-050-065E4F9B/Sun-ultraviolet-light-satellite-Earth-Solar-and.jpg?w=1000" alt="1 July 2002: The Solar and Heliospheric Observatory (SOHO) satellite reveals a massive solar eruption more than 30 times the Earth's diameter. The eruption formed when a loop of a magnetic field over the surface of the Sun trapped hot gas." data-width="1025" data-height="1121" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/19/73319-050-065E4F9B/Sun-ultraviolet-light-satellite-Earth-Solar-and.jpg" data-href="*68803">imaging using ultraviolet light</a><span>The Sun as imaged in extreme ultraviolet light by the Earth-orbiting Solar and Heliospheric Observatory (SOHO) satellite. A massive loop-shaped eruptive prominence is visible at the lower left. Nearly white areas are the hottest; deeper reds indicate cooler temperatures.</span></span></div><cite class="credit d-block mt-5">NASA</cite></figcaption></figure><p class="topic-paragraph">The Sun would be a little over 14 feet (4 meters) in diameter, about the size of a large gazebo.</p><span class="MOD"></span></div><span class="LIST-ITEM-2"></span></li><li><h2>Moon</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/29/23329-050-E4D2ABF7/Earth-impact-basins-side-Moon-way-spacecraft-December-7-1992.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*19095"><img src="https://cdn.britannica.com/29/23329-050-E4D2ABF7/Earth-impact-basins-side-Moon-way-spacecraft-December-7-1992.jpg?w=1000" alt="Near side of the Earth's Moon, photographed by the Galileo spacecraft on its way to the Jupiter system on December 7, 1992. The dark areas are impact basins: Oceanus Procellarum (left), Mare Imbrium (centre left), Mare Serenitatis and MareTranquillitatis" data-width="1600" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/29/23329-050-E4D2ABF7/Earth-impact-basins-side-Moon-way-spacecraft-December-7-1992.jpg" data-href="*19095">Moon</a><span> <p>The familiar near side of Earth's Moon, photographed on December 7, 1992, by the Galileo spacecraft on its way to Jupiter. Two primary kinds of terrain are visible—the lighter areas, which constitute the heavily cratered and very old highlands, and the darker, roughly circular plains, traditionally called maria, which are relatively young lava-filled impact basins.</p> <p>Among the maria are (from left) the crescent-shaped Oceanus Procellarum near the left limb, the large, almost perfectly circular Mare Imbrium, or Imbrium Basin (with the crater Copernicus a bright dot at its lower margin), Mare Serenitatis immediately to the right of Imbrium, Mare Tranquillitatis to the lower right of Serenitatis, and Mare Crisium, isolated near the right limb. Another bright crater, Tycho, stands out at the bottom left of the image.</p> </span></span></div><cite class="credit d-block mt-5">NASA/JPL/Caltech (NASA photo # PIA00405)</cite></figcaption></figure><p class="topic-paragraph">On this scale the Moon would be a marble 4 feet (1.2 meters) from Earth.</p><span class="MOD"></span></div><span class="LIST-ITEM-3"></span></li><li><h2>Mercury</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/16/75516-050-C40070F2/Photo-mosaic-Mercury-Mariner-10-spacecraft-1974.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*69378"><img src="https://cdn.britannica.com/16/75516-050-C40070F2/Photo-mosaic-Mercury-Mariner-10-spacecraft-1974.jpg?w=1000" alt="Photo mosaic of images of Mercury taken from 125,000 miles away by Mariner 10 spacecraft in 1974." data-width="1046" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/16/75516-050-C40070F2/Photo-mosaic-Mercury-Mariner-10-spacecraft-1974.jpg" data-href="*69378">Mercury</a><span>Photo mosaic of Mercury, taken by the Mariner 10 spacecraft, 1974.</span></span></div><cite class="credit d-block mt-5">NASA/JPL</cite></figcaption></figure><p class="topic-paragraph">The planet Mercury would be the size of a large marble 2 American football fields away from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-4"></span></li><li><h2>Venus</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/09/78009-050-49FFFBA9/ultraviolet-light-Venus-spacecraft-Pioneer-Orbiter-bands-Feb-26-1979.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*72954"><img src="https://cdn.britannica.com/09/78009-050-49FFFBA9/ultraviolet-light-Venus-spacecraft-Pioneer-Orbiter-bands-Feb-26-1979.jpg?w=1000" alt="Ultraviolet image of Venus' clouds as seen by the Pioneer Venus orbiter; February 26, 1979." data-width="1498" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/09/78009-050-49FFFBA9/ultraviolet-light-Venus-spacecraft-Pioneer-Orbiter-bands-Feb-26-1979.jpg" data-href="*72954">Venus</a><span>Venus photographed in ultraviolet light by the Pioneer Venus Orbiter (Pioneer 12) spacecraft, February 26, 1979. Although Venus's cloud cover is nearly featureless in visible light, ultraviolet imaging reveals distinctive structure and pattern, including global-scale V-shaped bands that open toward the west (left). Added color in the image emulates Venus's yellow-white appearance to the eye.</span></span></div><cite class="credit d-block mt-5">NASA/JPL</cite></figcaption></figure><p class="topic-paragraph">Venus would approximate a Ping-Pong ball placed 375 yards (340 meters; slightly less than 2 blocks) from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-5"></span></li><li><h2>Mars</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/64/73464-050-56C80D3A/view-composite-images-Mars-spacecraft-Global-Surveyor-April-1999.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*70910"><img src="https://cdn.britannica.com/64/73464-050-56C80D3A/view-composite-images-Mars-spacecraft-Global-Surveyor-April-1999.jpg?w=1000" alt="Global image of "homey" Earthlike Mars (Tharsis side) with wispy clouds, taken from Mars Global Surveyor, April 1999." data-width="1600" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/64/73464-050-56C80D3A/view-composite-images-Mars-spacecraft-Global-Surveyor-April-1999.jpg" data-href="*70910">Mars</a><span>An especially serene view of Mars (Tharsis side), a composite of images taken by the Mars Global Surveyor spacecraft in April 1999. The northern polar cap and encircling dark dune field of Vastitas Borealis are visible at the top of the globe. White water-ice clouds surround the most prominent volcanic peaks, including Olympus Mons near the western limb, Alba Patera to its northeast, and the line of Tharsis volcanoes to the southeast. East of the Tharsis rise can be seen the enormous near-equatorial gash that marks the canyon system Valles Marineris.</span></span></div><cite class="credit d-block mt-5">NASA/JPL/Malin Space Science Systems</cite></figcaption></figure><p class="topic-paragraph">Mars would be a gumball sitting 3 ¼ blocks from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-6"></span></li><li><h2>Jupiter</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/08/21208-050-D228E4D8/planets-planet-sun-Jupiter-one-Great-Red-1979.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*17762"><img src="https://cdn.britannica.com/08/21208-050-D228E4D8/planets-planet-sun-Jupiter-one-Great-Red-1979.jpg?w=1000" alt="Jupiter, the fifth planet from the Sun and largest planet in the solar system. The Great Red Spot is visible in the lower left. This image is based on observations made by the Voyager 1 spacecraft in 1979." data-width="840" data-height="840" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/08/21208-050-D228E4D8/planets-planet-sun-Jupiter-one-Great-Red-1979.jpg" data-href="*17762">Jupiter</a><span>Jupiter, the fifth planet from the Sun and largest planet in the solar system. The Great Red Spot is visible in the lower left. This image is based on observations made by the Voyager 1 spacecraft in 1979.</span></span></div><cite class="credit d-block mt-5">Photo NASA/JPL/Caltech (NASA photo # PIA00343)</cite></figcaption></figure><p class="topic-paragraph">Jupiter would be a large beach ball situated 1.5 miles (2.4 kilometers) from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-7"></span></li><li><h2>Saturn</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/67/21167-004-6B1CF05E/Saturn-storm-Earth-region-observations-image-Hubble-December-1-1994.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*17713"><img src="https://cdn.britannica.com/67/21167-004-6B1CF05E/Saturn-storm-Earth-region-observations-image-Hubble-December-1-1994.jpg?w=1000" alt="Saturn, showing an Earth-sized storm in its northern hemisphere. Such large storms are relatively rare on Saturn, which compared with Jupiter has a generally less turbulent atmosphere. Image based on observations made by the Hubble Space Telescope, Dec.1" data-width="550" data-height="380" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/67/21167-004-6B1CF05E/Saturn-storm-Earth-region-observations-image-Hubble-December-1-1994.jpg" data-href="*17713">Saturn</a><span>Saturn, showing an Earth-sized storm (light-coloured patch) in its northern equatorial region, in a composite image made from observations with the Hubble Space Telescope on December 1, 1994, more than two months after the storm's discovery. Large storms are relatively rare on Saturn, which has a less-active atmosphere than Jupiter.</span></span></div><cite class="credit d-block mt-5">Photo AURA/STScI/NASA/JPL (NASA photo # PIA01464, STScI-PRC94-53)</cite></figcaption></figure><p class="topic-paragraph">Saturn would be a slightly smaller beach ball located 2.8 miles (4.5 kilometers) from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-8"></span></li><li><h2>Uranus</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/85/145485-004-62E4BA89/Visible-Image-Uranus-Hubble-Space-Telescope-satellites-1998.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*155673"><img src="https://cdn.britannica.com/85/145485-004-62E4BA89/Visible-Image-Uranus-Hubble-Space-Telescope-satellites-1998.jpg?w=1000" alt="Hubble Space Telescope view reveals Uranus surrounded by its 4 major rings and by 10 of its 17 known satellites.Hubble recently found about 20 clouds--nearly as many clouds on Uranus as the previous total in the history of modern observations.Dated 1998." data-width="487" data-height="450" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/85/145485-004-62E4BA89/Visible-Image-Uranus-Hubble-Space-Telescope-satellites-1998.jpg" data-href="*155673">Hubble Space Telescope: Uranus</a><span>Image of Uranus captured by the Hubble Space Telescope, 1998. Visible are four of its major rings and 10 of its satellites.</span></span></div><cite class="credit d-block mt-5">Erich Karkoschka, University of Arizona and NASA</cite></figcaption></figure><p class="topic-paragraph">The planet Uranus would be the size of a cantaloupe placed 5.6 miles (9 kilometers) from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-9"></span></li><li><h2>Neptune</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/95/4295-050-42B3B41B/Clouds-Great-Dark-Spot-atmosphere-Neptune-Voyager-August-1989.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*3490"><img src="https://cdn.britannica.com/95/4295-050-42B3B41B/Clouds-Great-Dark-Spot-atmosphere-Neptune-Voyager-August-1989.jpg?w=1000" alt="Voyager 2 image of clouds in Neptune's atmosphere. The Great Dark Spot and its associated bright methane-ice clouds are shown slightly to the left of centre, the small dark spot is at the lower left, and the bright "Scooter" is justnorthward of the small" data-width="1209" data-height="1311" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/95/4295-050-42B3B41B/Clouds-Great-Dark-Spot-atmosphere-Neptune-Voyager-August-1989.jpg" data-href="*3490">clouds in Neptune's atmosphere</a><span>Clouds in Neptune's atmosphere, photographed by Voyager 2 in August 1989. The view is from below the planet's equator, and north is up. The Great Dark Spot (centre left) is 13,000 km (8,100 miles)—about the diameter of Earth—in its longer dimension. Accompanying it are bright, wispy clouds thought to comprise methane ice crystals. At higher southern latitudes lies a smaller, eye-shaped dark spot with a light core (bottom left). Just above that spot is a bright cloud dubbed Scooter. Each of these cloud features was seen to travel eastward but at a different rate, the Great Dark Spot moving the slowest.</span></span></div><cite class="credit d-block mt-5">NASA/JPL</cite></figcaption></figure><p class="topic-paragraph">Neptune would be approximately the size of a medium acorn squash 8.8 miles (14 kilometers) from the Sun.</p><span class="MOD"></span></div><span class="LIST-ITEM-10"></span></li><li><h2>Proxima Centauri</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/31/148331-050-1E969398/stars-Ursa-Major-Big-Dipper.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*154325"><img src="https://cdn.britannica.com/31/148331-050-1E969398/stars-Ursa-Major-Big-Dipper.jpg?w=1000" alt="Night sky showing Ursa Major stars (Big Dipper) in the northern sky. (constellation, astronomy)" data-width="1600" data-height="1176" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/31/148331-050-1E969398/stars-Ursa-Major-Big-Dipper.jpg" data-href="*154325">Big Dipper</a><span>The stars of the Big Dipper in the constellation Ursa Major.</span></span></div><cite class="credit d-block mt-5">© Rastan—iStock/Getty Images</cite></figcaption></figure><p class="topic-paragraph">The nearest star, Proxima Centauri, has to be placed 78,450 miles (126,250 kilometers) from the Sun on this scale!</p><span class="MOD"></span></div><span class="LIST-ITEM-11"></span></li><li><h2>Milky Way Galaxy</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/90/2590-050-6C33CB5C/Milky-Way-Galaxy-Earth.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*8113"><img src="https://cdn.britannica.com/90/2590-050-6C33CB5C/Milky-Way-Galaxy-Earth.jpg?w=1000" alt="Milky Way Galaxy as seen from Earth" data-width="1580" data-height="1052" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/90/2590-050-6C33CB5C/Milky-Way-Galaxy-Earth.jpg" data-href="*8113">Milky Way Galaxy</a><span>The Milky Way Galaxy as seen from Earth.</span></span></div><cite class="credit d-block mt-5">© Dirk Hoppe</cite></figcaption></figure><p class="topic-paragraph">The Milky Way galaxy would be 2,000,000 miles (3,200,000 kilometers) across!</p><span class="MOD"></span></div><span class="LIST-ITEM-12"></span></li><li><h2>Andromeda</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/39/155239-050-674BBCE2/Image-Andromeda-Galaxy-NASA-Wide-field-Infrared-Survey.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*167249"><img src="https://cdn.britannica.com/39/155239-050-674BBCE2/Image-Andromeda-Galaxy-NASA-Wide-field-Infrared-Survey.jpg?w=1000" alt="View of the Andromeda Galaxy (Messier 31, M31) taken by NASA's Wide-field Infrared Survey Explorer, or WISE. Blue highlights mature stars, while yellow and red show dust heated by newborn, massive stars." data-width="1600" data-height="1085" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/39/155239-050-674BBCE2/Image-Andromeda-Galaxy-NASA-Wide-field-Infrared-Survey.jpg" data-href="*167249">Andromeda Galaxy</a><span>Image of the Andromeda Galaxy taken by NASA's Wide-field Infrared Survey Explorer (WISE). Blue indicates mature stars, while yellow and red show dust heated by newborn massive stars.</span></span></div><cite class="credit d-block mt-5">NASA/JPL-Caltech/UCLA</cite></figcaption></figure><p class="topic-paragraph">Andromeda, the nearest spiral galaxy, would be 47,000,000,000 miles (76,000,000,000 kilometers) away on this scale!</p><span class="MOD"></span></div><span class="LIST-ITEM-13"></span></li><li><h2>Light</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/91/44791-050-FE8E43BB/Spectrum-light-diffraction-grating-end-prism-violet.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*37362"><img src="https://cdn.britannica.com/91/44791-050-FE8E43BB/Spectrum-light-diffraction-grating-end-prism-violet.jpg?w=1000" alt="Plate 1: Spectrum of white light by a diffraction grating. With a prism, the red end of the spectrum is more compressed than the violet end." data-width="1043" data-height="731" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/91/44791-050-FE8E43BB/Spectrum-light-diffraction-grating-end-prism-violet.jpg" data-href="*37362">Diffraction grating</a><span>Spectrum of white light by a diffraction grating. With a prism, the red end of the spectrum is more compressed than the violet end.</span></span></div><cite class="credit d-block mt-5">Courtesy of Bausch & Lomb, Rochester, N.Y.</cite></figcaption></figure><p class="topic-paragraph">The speed of light (in reality 186,282 m/sec) would be 2.1 miles per hour (3.4 kilometers per hour).</p><span class="MOD"></span></div><span class="LIST-ITEM-14"></span></li></ul><span class="AM-END-OF-ARTICLE am-inline"></span></article> </div> </div> </div> <aside class="cm-rightrail d-none d-md-block ad-rail"></aside> </div> </div> </div> </div> </main> <div class="grid gx-0"> <div class="col"> <div class="md-loading hidden display-4 font-weight-normal"></div> <div class="text-center my-20 mb-100"> <button class="md-infinite-load-next btn btn-blue" data-value="next-page">Load More</button> </div> </div> <div class="col-md-da-320 hidden-xs"> </div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Story","templateName":"WTFACT","pageNumber":1,"pagesTotal":11,"pageId":3780,"pageLength":null,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/story-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"B","adLeg":"B","userType":"ANONYMOUS","pageType":"Story","pageSubtype":"WTFACT","articleTemplateType":null,"gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

CINXE.COM

A Model of the Cosmos | Britannica