Gravity | Definition, Physics, & Facts

<!doctype html> <html lang="en" class="topic-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/3-133"> <link rel="preconnect" href="https://cdn.britannica.com/mendel-resources/3-133"> <link rel="preload" as="script" href="https://www.googletagservices.com/tag/js/gpt.js" /> <link rel="icon" href="/favicon.png" /> <meta name="description" content="Gravity, in mechanics, is the universal force of attraction acting between all bodies of matter. It is by far the weakest force known in nature and thus plays no role in determining the internal properties of everyday matter. Yet, it also controls the trajectories of bodies in the universe and the structure of the whole cosmos." /> <meta name="keywords" content="gravity, encyclopedia, encyclopeadia, britannica, article" /> <link rel="canonical" href="https://www.britannica.com/science/gravity-physics" /> <title>Gravity | Definition, Physics, & Facts | Britannica</title>  <script> !function(){"use strict";function e(e){const t=e.match(/((?=([a-z0-9._!#$%+^&*()[\]<>-]+))\2@[a-z0-9._-]+\.[a-z0-9._-]+)/gi);return t?t[0]:""}function t(t){return e(a(t.toLowerCase()))}function a(e){return e.replace(/\s/g,"")}async function n(e){const t={sha256Hash:"",sha1Hash:""};if(!("msCrypto"in window)&&"https:"===location.protocol&&"crypto"in window&&"TextEncoder"in window){const a=(new TextEncoder).encode(e),[n,c]=await Promise.all([s("SHA-256",a),s("SHA-1",a)]);t.sha256Hash=n,t.sha1Hash=c}return t}async function s(e,t){const a=await crypto.subtle.digest(e,t);return Array.from(new Uint8Array(a)).map(e=>("00"+e.toString(16)).slice(-2)).join("")}function c(e){let t=!0;return Object.keys(e).forEach(a=>{0===e[a].length&&(t=!1)}),t}function i(e,t,a){e.splice(t,1);const n="?"+e.join("&")+a.hash;history.replaceState(null,"",n)}var o={checkEmail:e,validateEmail:t,trimInput:a,hashEmail:n,hasHashes:c,removeEmailAndReplaceHistory:i,detectEmails:async function(){const e=new URL(window.location.href),a=Array.from(e.searchParams.entries()).map(e=>`=`);let s,o;const r=["adt_eih","sh_kit"];if(a.forEach((e,t)=>{const a=decodeURIComponent(e),[n,c]=a.split("=");if("adt_ei"===n&&(s={value:c,index:t,emsrc:"url"}),r.includes(n)){o={value:c,index:t,emsrc:"sh_kit"===n?"urlhck":"urlh"}}}),s)t(s.value)&&n(s.value).then(e=>{if(c(e)){const t={value:e,created:Date.now()};localStorage.setItem("adt_ei",JSON.stringify(t)),localStorage.setItem("adt_emsrc",s.emsrc)}});else if(o){const e={value:{sha256Hash:o.value,sha1Hash:""},created:Date.now()};localStorage.setItem("adt_ei",JSON.stringify(e)),localStorage.setItem("adt_emsrc",o.emsrc)}s&&i(a,s.index,e),o&&i(a,o.index,e)},cb:"adthrive"};const{detectEmails:r,cb:l}=o;r()}(); </script> <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","PROCON_EDITOR_ID": "12941390","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","topicUrlClasses": "[topic, animal, art, biography, event, place, plant, science, sports, technology, procon, money]","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","TOPIC_COLLECTION_URL": "/summary","LOGINBOX_URL": "/auth/loginbox","PROCON_DEBATE_TOPICS_URL": "/procon/Debate-Topics","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_SETTINGS_URL = "https://cam.britannica.com/settings"; window.CAM_LOGIN_URL = "https://cam.britannica.com/login"; window.CAM_SIGN_UP_URL = "https://cam.britannica.com/registration" window.Mendel = { "config" : { "domain": "britannica.com", "page": "Topic", "videoPlayerId": "UyMCoK2v", "sharedUrl": "https://www.britannica.com/science/gravity-physics", "amuselabsUrl": "https://cdn3.amuselabs.com", "resourcesPrefixUrl": "https://cdn.britannica.com/mendel-resources/3-133/[url]?v=3.133.9", "date": 20250217, "userInfo": { "type": "ANONYMOUS" ,"currency": "AUUS" ,"country": "SG" ,"state": "XX" ,"timezone": "Asia/Singapore" ,"bcomId": "4413372566245337206" ,"hasAds": true ,"testVersion": "A" ,"adsTestVersion": "A" ,"consumerId": "" ,"instId": "" ,"consumerUserName": "" ,"instUserName": "" ,"cognito": null }, "tvs":{ "r":[25,25,25,25], "a": [25,25,45,5]}, "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":242523,"currentDate":20250217}, "autocompleteToSearchPage": false,"topicUrl": "https://www.britannica.com/science/gravity-physics", "freeTopicReason": "PERMANENT_FREE_TOPIC", "topicId": 242523, "template": "DESKTOP", "type": "CORE", "hasToc": true, "chatbotApi": "https://www.britannica.com/chat-api", "showPreview": false, }, "GA": {"leg":"A","adLeg":"A","userType":"ANONYMOUS","pageType":"Topic","articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":true} }; </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/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg" /> <meta name="twitter:description" content="Gravity, in mechanics, is the universal force of attraction acting between all bodies of matter. It is by far the weakest force known in nature and thus plays no role in determining the internal properties of everyday matter. Yet, it also controls the trajectories of bodies in the universe and the structure of the whole cosmos."/> <meta property="og:type" content="ARTICLE"/> <meta property="og:title" content="Gravity | Definition, Physics, & Facts | Britannica"/> <meta property="og:description" content="Gravity, in mechanics, is the universal force of attraction acting between all bodies of matter. It is by far the weakest force known in nature and thus plays no role in determining the internal properties of everyday matter. Yet, it also controls the trajectories of bodies in the universe and the structure of the whole cosmos."/> <meta property="og:site_name" content="Encyclopedia Britannica" /> <meta property="og:url" content="https://www.britannica.com/science/gravity-physics"/> <meta property="og:image" content="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg" /> <meta property="og:image:type" content="image/jpeg" /> <script type="text/javascript" data-type="init opengraph"> Mendel.openGraph = {"type":"ARTICLE","title":"Gravity | Definition, Physics, & Facts","description":"Gravity, in mechanics, is the universal force of attraction acting between all bodies of matter. It is by far the weakest force known in nature and thus plays no role in determining the internal properties of everyday matter. Yet, it also controls the trajectories of bodies in the universe and the structure of the whole cosmos.","imageUrl":"https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg","imageType":"image/jpeg","pageUrl":"https://www.britannica.com/science/gravity-physics"}</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/3-133/dist/vendor-bundle.css?v=3.133.9" rel="stylesheet" /> <link href="https://cdn.britannica.com/mendel-resources/3-133/dist/mendel-css.css?v=3.133.9" rel="stylesheet" /> <link href="https://cdn.britannica.com/mendel-resources/3-133/dist/topic-page.css?v=3.133.9" rel="stylesheet" /> <script type="text/javascript"> if (self !== top) { top.location = self.location; } </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/at.js?v=3.133.9" 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> <meta name="last-modified" content="2025-01-23" /> <script type="application/ld+json"> {"headline":"Gravity | Definition, Physics, & Facts","image":{"url":"https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg","@type":"ImageObject"},"author":[{"name":"Kenneth L. Nordtvedt","url":"https://www.britannica.com/contributor/Kenneth-L-Nordtvedt/2162","@type":"Person"},{"name":"Alan H. Cook","url":"https://www.britannica.com/contributor/Alan-H-Cook/3508","@type":"Person"}],"keywords":"gravity","wordcount":10595,"url":"https://www.britannica.com/science/gravity-physics","datePublished":"1998-07-20T00:00:00Z","dateModified":"2025-01-23T00:00:00Z","description":"Gravity, in mechanics, is the universal force of attraction acting between all bodies of matter. It is by far the weakest force known in nature and thus plays no role in determining the internal properties of everyday matter. Yet, it also controls the trajectories of bodies in the universe and the structure of the whole cosmos.","publisher":{"name":"Encyclopedia Britannica","@type":"Organization","logo":{"url":"https://corporate.britannica.com/wp-content/themes/eb-corporate/_img/logo.png","@type":"ImageObject"}},"@context":"https://schema.org","@type":"article"} </script> </head> <body data-leg="A" class="new-topic topic-desktop first-page-true user-ANONYMOUS user-ads md-desktop leg-a b-ie">  <script>Mendel.config.adProvider='cafemedia';</script> <script data-no-optimize="1" data-cfasync="false"> (function(w, d) { w.adthrive = w.adthrive || {}; w.adthrive.cmd = w. adthrive.cmd || []; w.adthrive.plugin = 'adthrive-ads-manual'; w.adthrive.host = 'ads.adthrive.com';var s = d.createElement('script'); s.async = true; s.referrerpolicy='no-referrer-when-downgrade'; s.src = 'https://' + w.adthrive.host + '/sites/61575e5c934c481d714b3ca9/ads.min.js?referrer=' + w.encodeURIComponent(w.location.href) + '&cb=' + (Math.floor(Math.random() * 100) + 1); var n = d.getElementsByTagName('script')[0]; n.parentNode.insertBefore(s, n); })(window, document); </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":"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":"ProCon","url":"/procon","navbarId":"PROCON"},{"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":"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":"ProCon","url":"/procon"},{"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://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=global-nav&utm_campaign=evergreen-cap" class="subscribe-link btn btn-sm btn-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://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=global-nav-mobile&utm_campaign=evergreen" class="subscribe-link btn btn-xs btn-orange 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://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=nav-login-box&utm_campaign=evergreen</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=evergreen" class="subscribe-link btn btn-sm btn-orange py-5" target="_blank"> SUBSCRIBE </a></DIV></div> <div id="global-nav-react"> <div class="d-none"> <ul> <li><a href="/">Home</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="/procon">ProCon</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-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-PROCON " href="/procon">ProCon</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"> <div class="md-article-container template-desktop infinite-pagination"> <div class="infinite-scroll-container article last"> <script> Object.assign( window.Mendel.config, { "infiniteScrollList": [{"p":7,"t":242523},{"p":1,"t":67925},{"p":1,"t":151686},{"p":10,"t":139301},{"p":1,"t":595148},{"p":1,"t":557482},{"p":10,"t":486231},{"p":2,"t":462888},{"p":1,"t":242451},{"p":5,"t":1987141}], "sequence": 1, "topics": {} }); </script> <article class="article-content container-lg qa-content px-0 pt-0 pb-40 py-lg-20 content md-expanded" data-topic-id="242523"> <div class="grid gx-0"> <div class="col-auto"> <div class="topic-left-rail md-article-drawer position-relative d-flex border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/science/gravity-physics">gravity</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/science/gravity-physics">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref61463"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/gravity-physics#ref61463">Development of gravitational theory</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref61464"><a class="w-100 link-gray-900" href="/science/gravity-physics#ref61464">Early concepts</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61465"><a class="w-100 link-gray-900" href="/science/gravity-physics/Newtons-law-of-gravity">Newton’s law of gravity</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref61466"><a class="w-100 link-gray-900" href="/science/gravity-physics/Newtons-law-of-gravity#ref61466">Weight and mass</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref61467"><a class="w-100 link-gray-900" href="/science/gravity-physics/Interaction-between-celestial-bodies">Interaction between celestial bodies</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61468"><a class="w-100 link-gray-900" href="/science/gravity-physics/Interaction-between-celestial-bodies#ref61468">Potential theory</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref61469"><a class="w-100 link-gray-900" href="/science/gravity-physics/Interaction-between-celestial-bodies#ref61469">Effects of local mass differences</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref61470"><a class="w-100 link-gray-900" href="/science/gravity-physics/Interaction-between-celestial-bodies#ref61470">Weighing the Earth</a></li></ul></li></ul></div></li><li data-target="#ref61471"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets">Acceleration around Earth, the Moon, and other planets</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref61472"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61472">Variations in <em>g</em></a><ul class="list-unstyled" data-level="h3"><li data-target="#ref61473"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61473">Changes due to location</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref61474"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61474">Changes with time</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61475"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61475">Measurements of <em>g</em></a><ul class="list-unstyled" data-level="h3"><li data-target="#ref61476"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61476">Unit of gravity</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref61477"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61477">Absolute measurements</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref61478"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61478">Relative measurements</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61480"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61480">Gravimetric surveys and geophysics</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61481"><a class="w-100 link-gray-900" href="/science/gravity-physics/Acceleration-around-Earth-the-Moon-and-other-planets#ref61481">The Moon and the planets</a></li></ul></div></li><li data-target="#ref61482"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/gravity-physics/Gravitational-theory-and-other-aspects-of-physical-theory">Gravitational theory and other aspects of physical theory</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref61483"><a class="w-100 link-gray-900" href="/science/gravity-physics/Gravitational-theory-and-other-aspects-of-physical-theory#ref61483">Field theories of gravitation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61484"><a class="w-100 link-gray-900" href="/science/gravity-physics/Gravitational-fields-and-the-theory-of-general-relativity">Gravitational fields and the theory of general relativity</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61485"><a class="w-100 link-gray-900" href="/science/gravity-physics/Gravitational-fields-and-the-theory-of-general-relativity#ref61485">The paths of particles and light</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61486"><a class="w-100 link-gray-900" href="/science/gravity-physics/Gravitational-fields-and-the-theory-of-general-relativity#ref61486">Gravitational radiation</a></li></ul></div></li><li data-target="#ref61487"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/gravity-physics/Gravitational-fields-and-the-theory-of-general-relativity#ref61487">Some astronomical aspects of gravitation</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref61488"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/gravity-physics/Experimental-study-of-gravitation">Experimental study of gravitation</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref61489"><a class="w-100 link-gray-900" href="/science/gravity-physics/Experimental-study-of-gravitation#ref61489">The inverse square law</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61490"><a class="w-100 link-gray-900" href="/science/gravity-physics/Experimental-study-of-gravitation#ref61490">The principle of equivalence</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61491"><a class="w-100 link-gray-900" href="/science/gravity-physics/Experimental-study-of-gravitation#ref61491">The constant of gravitation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61492"><a class="w-100 link-gray-900" href="/science/gravity-physics/Experimental-study-of-gravitation#ref61492">The variation of the constant of gravitation with time</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref61493"><a class="w-100 link-gray-900" href="/science/gravity-physics/Experimental-study-of-gravitation#ref61493">Fundamental character of <em>G</em></a></li></ul></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/science/gravity-physics/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/gravity-physics">Quick Facts & Related Topics</a> </div> <div class="tlr-media-slider pb-10 mb-30"> <a class="section-header link-gray-900 font-serif font-14 font-weight-bold mb-10 mx-10" href="https://www.britannica.com/science/gravity-physics/images-videos">Images & Videos</a> <div class="slider js-slider position-relative d-inline-flex align-items-center mw-100 "> <div class="slider-container js-slider-container overflow-hidden d-flex overflow-hidden text-nowrap ml-15"> <a href="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg" data-href="/media/1/242523/17790" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg" alt="gravitational lens" height="50" /> </a> <a href="/video/Explanation-gravitational-force-Isaac-Newton-1687/158977" data-href="/media/1/242523/158977" class="media-overlay-link d-inline-block mr-5"> <div class="position-relative --aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/70/151070-138-3B889A11/Explanation-gravitational-force-Isaac-Newton-1687.jpg?w=400&h=225&c=crop" alt="How gravity works on Earth and in the universe" class="col-100" /> <div class="btn btn-sm btn-white btn-circle position-absolute shadow" style="top: 50%; left:50%; transform: translate(-50%, -50%)"> <em class="material-icons font-14" data-icon="play_arrow" > </em> </div> </div> </a> <a href="https://cdn.britannica.com/81/94581-050-531CAC1F/Effects-gravity-Earth-Moon.jpg" data-href="/media/1/242523/141791" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/81/94581-004-F3DAF261/Effects-gravity-Earth-Moon.jpg" alt="effects of gravity on the Moon and Earth" height="50" /> </a> <a href="https://cdn.britannica.com/90/106990-050-7D3C55E4/Earth-force-distance.jpg" data-href="/media/1/242523/161888" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/90/106990-004-7B99A996/Earth-force-distance.jpg" alt="gravitational force" height="50" /> </a> <a href="https://cdn.britannica.com/20/96320-004-3FC5219A/variation-gravitational-field-surface-geoid-milliGals-Earth.jpg" data-href="/media/1/242523/90695" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/20/96320-004-3FC5219A/variation-gravitational-field-surface-geoid-milliGals-Earth.jpg" alt="variation in Earth's gravitational field" height="50" /> </a> <a href="/video/general-relativity/219078" data-href="/media/1/242523/219078" class="media-overlay-link d-inline-block mr-5"> <div class="position-relative --aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/06/193406-138-C5341EDE/general-relativity.jpg?w=400&h=225&c=crop" alt="View a demonstration to understand Albert Einstein's general theory of relativity" class="col-100" /> <div class="btn btn-sm btn-white btn-circle position-absolute shadow" style="top: 50%; left:50%; transform: translate(-50%, -50%)"> <em class="material-icons font-14" data-icon="play_arrow" > </em> </div> </div> </a> <a href="https://cdn.britannica.com/65/91965-004-116CAD96/Einstein-general-relativity-evidence-observation-light-prediction-1919.jpg" data-href="/media/1/242523/86707" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/65/91965-004-116CAD96/Einstein-general-relativity-evidence-observation-light-prediction-1919.jpg" alt="experimental evidence for general relativity" height="50" /> </a> <a href="/video/significance-waves-science-life/208328" data-href="/media/1/242523/208328" class="media-overlay-link d-inline-block mr-5"> <div class="position-relative --aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/67/188867-138-187EC42F/significance-waves-science-life.jpg?w=400&h=225&c=crop" alt="How are gravitational waves applied in science and in everyday life?" class="col-100" /> <div class="btn btn-sm btn-white btn-circle position-absolute shadow" style="top: 50%; left:50%; transform: translate(-50%, -50%)"> <em class="material-icons font-14" data-icon="play_arrow" > </em> </div> </div> </a> <a href="https://cdn.britannica.com/21/96321-050-B2AC5932/spacecraft-LISA-Laser-Interferometer-Space-Antenna-Beyond-2015.jpg" data-href="/media/1/242523/90798" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/21/96321-004-4F5A7298/spacecraft-LISA-Laser-Interferometer-Space-Antenna-Beyond-2015.jpg" alt="Laser Interferometer Space Antenna (LISA)" height="50" /> </a> <a href="https://cdn.britannica.com/26/205226-050-B2621B00/Black-hole-M87-centre-evidence-supermassive-black.jpg" data-href="/media/1/242523/239625" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/26/205226-004-E0B95A1E/Black-hole-M87-centre-evidence-supermassive-black.jpg" alt="black hole in M87" height="50" /> </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 class="mb-30 tlr-student-links"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> For Students </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/summary/gravity-physics"> <img loading="lazy" src="https://cdn.britannica.com/mendel-resources/3-133/images/shared/default3.png?v=3.133.9" class="default " height="200" width="200"/> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/summary/gravity-physics" >gravity summary</a> </div> </div> </div> <div class="mb-30 tlr-related-quizzes"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Quizzes </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/quiz/physics-and-natural-law"> <img loading="lazy" src="https://cdn.britannica.com/01/115001-131-7278E518/Enrico-Fermi-Italian-problem-physics-1950.jpg?w=200&h=200&c=crop" alt="Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/quiz/physics-and-natural-law" >Physics and Natural Law</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/quiz/all-about-astronomy"> <img loading="lazy" src="https://cdn.britannica.com/54/102254-131-ED1A2CE1/Nicolaus-Copernicus.jpg?w=200&h=200&c=crop" alt="Nicolaus Copernicus. Nicolas Copernicus (1473-1543) Polish astronomer. In 1543 he published, forward proof of a Heliocentric (sun centered) universe. Coloured stipple engraving published London 1802. De revolutionibus orbium coelestium libri vi." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/quiz/all-about-astronomy" >All About Astronomy</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/quiz/all-about-physics-quiz"> <img loading="lazy" src="https://cdn.britannica.com/03/221503-131-D7173869/Italian-physicist-Guglielmo-Marconi-at-work-on-his-yacht-Electra.jpg?w=200&h=200&c=crop" alt="Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/quiz/all-about-physics-quiz" >All About Physics Quiz</a> </div> </div> </div> <div class="mb-30 tlr-related-questions"> <div class="text-gray-900 p-5 pb-0 font-serif font-14 font-weight-bold mx-10 mb-15"> Related Questions </div> <ul> <li class="link-gray-900 mb-15"><a class="" href="/question/How-has-Galileo-influenced-science">How has Galileo influenced science?</a> </li> <li class="link-gray-900 mb-15"><a class="" href="/question/What-is-Isaac-Newton-most-famous-for">What is Isaac Newton most famous for?</a> </li> <li class="link-gray-900 mb-15"><a class="" href="/question/How-was-Isaac-Newton-educated">How was Isaac Newton educated?</a> </li> <li class="link-gray-900 mb-15"><a class="" href="/question/What-was-Isaac-Newtons-childhood-like">What was Isaac Newton’s childhood like?</a> </li> </ul> </div> <div class="mb-30 tlr-read-next"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Read Next </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/gravity-from-apples-to-the-universe"> <img loading="lazy" src="https://cdn.britannica.com/85/131985-131-280FFD87/Mark-C-Lee-Extravehicular-Activity-Spacewalk-Rescue-Sept-16-1994.jpg?w=200&h=200&c=crop" alt="Above the clouds 130 nautical miles below, astronaut Mark C. Lee floats freely without tethers as he tests the new Simplified Aid for Extravehicular Activity (EVA) Spacewalk Rescue (SAFER) system, Sept. 16, 1994. Space Shuttle Discovery, STS-64" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/gravity-from-apples-to-the-universe" >Gravity: From Apples to the Universe</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/100-years-of-general-relativity"> <img loading="lazy" src="https://cdn.britannica.com/09/75509-131-93B65AAF/Albert-Einstein.jpg?w=200&h=200&c=crop" alt="Albert Einstein" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/100-years-of-general-relativity" >100 Years of General Relativity</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/how-fast-is-the-universe-expanding"> <img loading="lazy" src="https://cdn.britannica.com/27/238127-131-9A610712/galaxy-cluster-Abell-2744.jpg?w=200&h=200&c=crop" alt="Galaxy clusters like Abell 2744 can act as a natural cosmic lens, magnifying light from more distant, background objects through gravity. NASA's James Webb Space Telescope may be able to detect light from the first stars in the universe if they are gravitationally lensed by such clusters. (astronomy, space exploration, galaxies)" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/how-fast-is-the-universe-expanding" >How Fast Is the Universe Expanding?</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/telescopes-seeing-stars"> <img loading="lazy" src="https://cdn.britannica.com/60/190760-131-F1576E0B/space-background-telescope-silhouette-NASA-image-elements.jpg?w=200&h=200&c=crop" alt="Infinite space background with silhouette of telescope. This image elements furnished by NASA." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/telescopes-seeing-stars" >Telescopes: Seeing Stars</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/7-important-dates-in-jupiter-history"> <img loading="lazy" src="https://cdn.britannica.com/90/186790-131-AEA5CAE9/Planet-Jupiter-moon-left-orbiter-Io-mission-2000.jpg?w=200&h=200&c=crop" alt="Planet Jupiter with its moon Io at left, photographed by the Cassini orbiter during the Cassini-Huygens mission, 2000. spacecraft" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/7-important-dates-in-jupiter-history" >7 Important Dates in Jupiter History</a> </div> </div> </div> <div class="mb-30 tlr-discover"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Discover </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/how-does-wi-fi-work"> <img loading="lazy" src="https://cdn.britannica.com/18/197118-131-00A7D6AF/Computer-Code-Binary-Internet-Password-Data-Technology.jpg?w=200&h=200&c=crop" alt="Binary Computer Code, Binary Code, Internet, Technology, Password, Data" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/how-does-wi-fi-work" >How Does Wi-Fi Work?</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/who-was-the-woman-behind-the-statue-of-liberty"> <img loading="lazy" src="https://cdn.britannica.com/61/93061-131-ABCDE075/Statue-of-Liberty-Island-New-York-Bay.jpg?w=200&h=200&c=crop" alt="Statue of Liberty in front of the skyline of Manhattan, New York City, New York." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/who-was-the-woman-behind-the-statue-of-liberty" >Who Was the Woman Behind the Statue of Liberty?</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/list/periods-of-american-literature"> <img loading="lazy" src="https://cdn.britannica.com/56/198256-131-63923156/Chapter-header-The-Adventures-of-Tom-Sawyer-1884.jpg?w=200&h=200&c=crop" alt="Chapter 4 pg 42 - Chapter header of The Adventures of Tom Sawyer by Mark Twain. Published in 1884 by The American Publishing Company" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/list/periods-of-american-literature" >Periods of American Literature</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/list/13-questions-about-how-the-human-body-works-answered"> <img loading="lazy" src="https://cdn.britannica.com/20/125820-131-D8170E4F/veins-arteries-human.jpg?w=200&h=200&c=crop" alt="pulmonary veins and arteries, circulation, cardiovascular system, human anatomy, (Netter replacement project - SSC)" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/list/13-questions-about-how-the-human-body-works-answered" >13 Questions About How the Human Body Works Answered</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/list/americas-5-most-notorious-cold-cases-including-one-you-may-have-thought-was-already-solved"> <img loading="lazy" src="https://cdn.britannica.com/71/196471-131-8FEA8DDD/Daily-Police-Bulletin-Elizabeth-Short-Black-Dahlia-January-1947.jpg?w=200&h=200&c=crop" alt="Los Angeles Police Department wanted flyer on Elizabeth Short, aka the "Black Dahlia," who was brutally murdered in January 1947. The FBI supported the Los Angeles Police Department in the case, including by identifying Short through her fingerprints that" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/list/americas-5-most-notorious-cold-cases-including-one-you-may-have-thought-was-already-solved" >America’s 5 Most Notorious Cold Cases (Including One You May Have Thought Was Already Solved)</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/which-waters-do-you-pass-through-when-you-sail-the-seven-seas"> <img loading="lazy" src="https://cdn.britannica.com/97/196697-131-0155C802/Sailboat-landscape.jpg?w=200&h=200&c=crop" alt="Sailboat against a beautiful landscape" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/which-waters-do-you-pass-through-when-you-sail-the-seven-seas" >Which Waters Do You Pass Through When You “Sail the Seven Seas”?</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/nikola-teslas-weird-obsession-with-pigeons"> <img loading="lazy" src="https://cdn.britannica.com/13/173513-131-C6E1BD52/mourning-dove-North-America.jpg?w=200&h=200&c=crop" alt="bird. mourning dove. pigeon and dove. Mourning Dove (Zenaida macroura) family Columbidae." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/nikola-teslas-weird-obsession-with-pigeons" >Nikola Tesla's Weird Obsession with Pigeons</a> </div> </div> </div> </div> </div> </div> <button class="drawerToggle btn position-sticky border btn-xs btn-white btn-circle rounded-sm d-none d-lg-flex " type="button" aria-label="Toggle Drawer"> <em class="material-icons font-18 text-blue" data-icon="keyboard_arrow_left"></em> </button> </div> </div> <div class="col"> <div class="h-100 ml-0 pr-lg-0 "> <div class="h-100 grid gx-0 gx-lg-20"> <div class="h-100 col-sm"> <div class="h-100 infinite-pagination-container d-flex flex-column position-relative"> <div class="position-absolute top-0 h-100 w-100"> <div class="toc-sticky-header d-none d-lg-none bg-gray-50 px-10 px-sm-30 position-sticky w-100 "> <div class="toc-sticky-header-inner-container align-items-center d-flex mx-auto h-100 w-100"> <button class="d-flex d-lg-none btn btn-sm btn-white text-blue border-2 border-gray-100 gtm-mobile-toc-header-button js-sections-button d-lg-none p-10"> <em class="material-icons my-n5 md-icon" data-icon="toc"></em> Contents </button> <div class="header-ai-ask-button-placeholder"></div> <div class="header-ai-summarize-button-placeholder"></div> </div> </div> </div> <div class="grey-box w-100 grey-box-top"> <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/browse/Science", "name": "Science" } } , { "@type" : "ListItem", "position" : 2, "item" : { "@id" : "https://www.britannica.com/browse/Astronomy", "name": "Astronomy" } } ] } </script> <nav class="breadcrumb mt-20"> <span class="breadcrumb-item "> <a class="link-gray-600" href="/browse/Science">Science</a> </span> <span class="breadcrumb-item "> <a class="link-gray-600" href="/browse/Astronomy">Astronomy</a> </span> </nav> <div class="page2ref-true topic-content topic-type-REGULAR" data-student-article="false"> <script class="page-description-json" type="application/json"> { "url": "/science/gravity-physics", "shareUrl": "https://www.britannica.com/science/gravity-physics", "browserTitle": "Gravity | Definition, Physics, & Facts", "firstTopicPage": true, "topicId":242523 } </script> <div class="reading-channel"> <div class="desktop-header-image module-spacing"> <figure class="md-assembly m-0 mb-20 mb-md-0 card card-borderless print-false" data-assembly-id="13684" data-asm-type="image"> <div class="md-assembly-wrapper card-media " data-type="image"> <a style="min-height: 160px;" href="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/242523/17790"> <picture> <source media="(min-width: 680px)" srcset="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg?w=300"> <img src="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg?w=400&h=300&c=crop" alt="gravitational lens" loading="eager" /> </picture> <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="card-body"> <div class="md-assembly-caption text-muted font-14 font-serif line-clamp"> <span> <a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/50/21250-004-7E580D28/lens-Hubble-Space-Telescope-field-picture-copies.jpg" data-href="/media/1/242523/17790">gravitational lens</a> <span><span>A galactic cluster, about five billion light-years away, produces a tremendous gravitational field that “bends” light around it. This lens produces multiple copies of a blue galaxy about twice as distant. Four images are visible in a circle surrounding the lens; a fifth is visible near the center of the picture, which was taken by the Hubble Space Telescope. </span></span> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"> <span class="link-blue">(more)</span> </button> </span> </div> </figcaption> </figure> </div><div class="topic-header"> <div class="d-flex align-items-top justify-content-between"> <div class="d-flex flex-column"> <div> <div> <h1>gravity</h1></div> </div> <div class="topic-identifier font-16 font-md-20">physics</div> </div> </div> <div class="d-none d-sm-flex flex-row"> <div class="mr-10 mb-15"> <button class="ai-ask-button btn border-2 btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400"> Ask the Chatbot a Question </button> </div> <div class="d-block md-topic-tools qa-action-buttons mb-15" data-topic-id="242523"> <button class="js-tooltip btn btn-sm btn-outline-blue border pr-10 border-2 text-nowrap" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="more_vert"></em> More Actions </button> <div class="md-more-popover popover popover-sm p-0 font-14 z-1"> <div> <button class="js-print-modal-button js-modal gtm-topic-tool btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal="[data-topic-id=242523] .md-print-modal" > <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="print"></em> Print </button> <div class="md-print-modal size-lg d-none"> <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">print</em> Print </div> <div class="mt-20 mb-10"> Please select which sections you would like to print: </div> <form action="/print/article/242523" method="post" target="_blank" rel="noopener"> <div class="print-box-items"> <ul class="list-unstyled"> <li><label><input class="mr-10" type="checkbox" name="sequence[]" value="0">Table Of Contents</label></li> </ul> </div> <input type="submit" class="btn btn-blue md-disabled" value="Print" /> </form> </div> </div> </div> <div> <button class="js-modal qa-cite-modal-button btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal="[data-topic-id=242523] .md-cite-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" 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="Nordtvedt, Kenneth L., Cook, Alan H., Faller, James E." data-authors-initial="Nordtvedt, K.L., Cook, A.H., Faller, J.E." data-title="gravity" data-published-date="23 Jan. 2025" data-url="https://www.britannica.com/science/gravity-physics" > <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 font-weight-bold btn-link" data-modal="[data-topic-id=242523] .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="gravity" data-url="https://www.britannica.com/science/gravity-physics" > <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/science/gravity-physics">https://www.britannica.com/science/gravity-physics</a> </div> </div> </div> <div> <button class="js-feedback-modal-button js-modal btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal=".md-feedback-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="message"></em> Feedback </button> </div> <div> <button class="qa-external-website-modal-button js-modal btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal="[data-topic-id=242523] .md-websites-modal"> <em class="material-icons md-icon ml-n10 mr-5" data-icon="link"></em> External Websites </button> </div> </div> <div class="md-feedback-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif pb-15 border-bottom"> Feedback </div> <form method="post" action="/submission/feedback/242523"> <div class="my-20"> Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). </div> <div class="type-menu"> <label for="feedback-type" class="label mb-10">Feedback Type</label> <select id="feedback-type" class="form-select mb-30" name="feedbackTypeId" required> <option value="" selected="selected">Select a type (Required)</option> <option value="1">Factual Correction</option> <option value="2">Spelling/Grammar Correction</option> <option value="3">Link Correction</option> <option value="4">Additional Information</option> <option value="5">Other</option> </select> </div> <label for="feedback" class="label mb-10">Your Feedback</label> <textarea id="feedback" class="form-control mb-30" name="feedback" maxlength="3000" rows="7" required></textarea> <button class="btn btn-blue" type="submit">Submit Feedback</button> </form> <div class="success-messaging d-none mt-30"> <div class="title">Thank you for your feedback</div> <p>Our editors will review what you’ve submitted and determine whether to revise the article.</p> </div> </div> </div> <div class="md-websites-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif pb-15 border-bottom font-weight-bold"> External Websites </div> <div class="pb-20"> <ul class="list-unstyled mt-20 lh-lg"> <li><a class="external" href="https://www.space.com/classical-gravity.html" target="_blank" rel="noopener ">Space.com - Gravity: What is it?</a></li> <li><a class="external" href="https://www.livescience.com/37115-what-is-gravity.html" target="_blank" rel="noopener ">LiveScience - What is Gravity?</a></li> <li><a class="external" href="https://iopscience.iop.org/article/10.1088/1475-7516/2024/03/045/pdf" target="_blank" rel="noopener ">IOPscience - Journal of Cosmology and Astroparticle Physics - A cosmic glitch in gravity</a></li> <li><a class="external" href="https://www.wtamu.edu/~cbaird/sq/2012/12/18/why-is-there-no-gravity-in-space/" target="_blank" rel="noopener ">West Texas A and M University - Science Questions with Surprising Answers - Why is there no gravity in space?</a></li> <li><a class="external" href="https://www.kpu.ca/sites/default/files/Faculty%20of%20Science%20%26amp%3B%20Horticulture/Physics/Physics%201100%20Uniform%20Circular%20Motion%20%26amp%3B%20Gravity.pdf" target="_blank" rel="noopener ">Kwantlen Polytechnic University - Uniform Circular Motion and Gravity (PDF)</a></li> <li><a class="external" href="https://people.astro.umass.edu/~arny/jg_esc_veltut.html" target="_blank" rel="noopener ">University of Massachusetts Amherst - Department of Astronomy - Gravity and Escape Velocity Tutorial</a></li> <li><a class="external" href="https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Supplemental_Modules_(Astronomy_and_Cosmology)/Astronomy/Gravity/1.1%3A_Discovering_Gravity" target="_blank" rel="noopener ">Physics LibreTexts - Discovering Gravity</a></li> <li><a class="external" href="https://gracefo.jpl.nasa.gov/news/5/what-is-gravity/" target="_blank" rel="noopener ">NASA - Jet Propulsion Laboratory - What is Gravity?</a></li> <li><a class="external" href="https://s3.cern.ch/inspire-prod-files-5/5a78e08557c0480929c136a45b7532bb" target="_blank" rel="noopener ">CERN - Gravity and Zero Point Energy</a></li> <li><a class="external" href="https://cod.pressbooks.pub/physics1100/chapter/gravity/" target="_blank" rel="noopener ">College of DuPage Digital Press - Conceptual Physics - Gravity</a></li> <li><a class="external" href="https://www.academia.edu/9913538/A_Unified_Theory_of_Interaction_Gravitation_Electrodynamics_and_the_Strong_Force" target="_blank" rel="noopener ">Academia - A Unified Theory of Interaction: Gravitation, Electrodynamics and the Strong Force</a></li> <li><a class="external" href="https://www.khanacademy.org/science/hs-physics/x215e29cb31244fa1:types-of-interactions/x215e29cb31244fa1:newton-s-law-of-universal-gravitation/v/introduction-to-gravity" target="_blank" rel="noopener ">Khan Academy - Introduction to gravity</a></li> <li><a class="external" href="https://www.uio.no/studier/emner/matnat/math/MEK4480/v21/oppgaver/notescapillarity_lldfilm.pdf" target="_blank" rel="noopener ">University of Oslo - Capillarity and Gravity</a></li> </ul> </div> <div class="md-websites-ebk-title">Britannica Websites</div> <div class="md-websites-ebk-subtitle">Articles from Britannica Encyclopedias for elementary and high school students.</div> <ul class="list-unstyled bps-topic-web-sites lh-lg"> <li><a class="external" href="https://kids.britannica.com/kids/article/gravity/400109" target="_blank" rel="noopener">gravity - Children's Encyclopedia (Ages 8-11)</a></li> <li><a class="external" href="https://kids.britannica.com/students/article/gravity/274634" target="_blank" rel="noopener">gravity - Student Encyclopedia (Ages 11 and up)</a></li> </ul> </div> </div> </div> </div> <div class="toc-header-marker"></div> <button class="ai-ask-button btn border-2 js-header-ai-ask-button d-none btn-sm btn-outline-red-400 border-red-400 mr-0 mr-lg-10 ml-5 ml-sm-10 ml-lg-0 p-10"> Ask the Chatbot a Question </button> <div class="caption alternate-titles">Also known as: g-force, gravitation</div> <div class="md-byline module-spacing "> <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 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Kenneth-L-Nordtvedt/2162" > <div class="editor-title font-16 font-weight-bold">Kenneth L. Nordtvedt</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Emeritus Professor of Physics, Montana State University, Bozeman.</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"> Kenneth L. Nordtvedt</span>, <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Alan-H-Cook/3508" > <div class="editor-title font-16 font-weight-bold">Alan H. Cook</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Master of Selwyn College, University of Cambridge, 1983–93; Jacksonian Professor of Natural Philosophy, University of Cambridge, 1972–90. Author of <i>The Interiors of the Planets </i>and others.</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"> Alan H. Cook</span><span class="text-gray-700 mx-5">•</span><a class="see-all border-gray-700 gtm-byline" rel="nofollow" href="https://www.britannica.com/science/gravity-physics/additional-info#contributors">All</a> </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 qa-editor-popup 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 class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2025-01-23T00:00:00CST" >Jan 23, 2025</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/gravity-physics/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Also called: </dt> <dd>gravitation</dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/biography/Kip-Thorne" topicid="2109544">Kip Thorne</a></dd> <dd><a href="/biography/Isaac-Newton" topicid="413189">Isaac Newton</a></dd> <dd><a href="/biography/Galileo-Galilei" topicid="224058">Galileo</a></dd> <dd><a href="/biography/John-Archibald-Wheeler" topicid="641682">John Archibald Wheeler</a></dd> <dd><a href="/biography/Simon-Stevin" topicid="565994">Simon Stevin</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/Lagrangian-point" topicid="327899">Lagrange point</a></dd> <dd><a href="/science/supergravity" topicid="574319">supergravity</a></dd> <dd><a href="/science/weight" topicid="638947">weight</a></dd> <dd><a href="/science/Schwarzschild-radius" topicid="242490">Schwarzschild radius</a></dd> <dd><a href="/science/gravity-anomaly" topicid="242565">gravity anomaly</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>On the Web: </dt> <dd><a href="https://www.kpu.ca/sites/default/files/Faculty%20of%20Science%20%26amp%3B%20Horticulture/Physics/Physics%201100%20Uniform%20Circular%20Motion%20%26amp%3B%20Gravity.pdf" target="_blank">Kwantlen Polytechnic University - Uniform Circular Motion and Gravity (PDF)</a> (Jan. 23, 2025)</dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/gravity-physics"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref1147142"></span>gravity</strong>, in <a href="https://www.britannica.com/science/mechanics" class="md-crosslink autoxref " data-show-preview="true">mechanics</a>, the universal <a href="https://www.britannica.com/science/force-physics" class="md-crosslink autoxref " data-show-preview="true">force</a> of attraction acting between all bodies of matter. It is by far the weakest known force in nature and thus plays no role in determining the internal properties of everyday matter. On the other hand, through its long reach and universal action, it controls the <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="trajectories" href="https://www.britannica.com/dictionary/trajectories" data-type="EB">trajectories</a> of bodies in the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink autoxref " data-show-preview="true">solar system</a> and elsewhere in the <a href="https://www.britannica.com/science/universe" class="md-crosslink autoxref " data-show-preview="true">universe</a> and the structures and evolution of stars, galaxies, and the whole <a href="https://www.britannica.com/science/Cosmos-astronomy" class="md-crosslink " data-show-preview="true">cosmos</a>. On Earth all bodies have a <a href="https://www.britannica.com/science/weight" class="md-crosslink autoxref " data-show-preview="true">weight</a>, or downward force of gravity, proportional to their mass, which Earth’s mass exerts on them. Gravity is measured by the acceleration that it gives to freely falling objects. At <span id="ref1171695"></span><a href="https://www.britannica.com/place/Earth" class="md-crosslink " data-show-preview="true">Earth</a>’s surface the acceleration of gravity is about 9.8 meters (32 feet) per second per second. Thus, for every second an object is in free fall, its speed increases by about 9.8 meters per second. At the surface of the <span id="ref1171696"></span><a href="https://www.britannica.com/place/Moon" class="md-crosslink " data-show-preview="true">Moon</a> the acceleration of a freely falling body is about 1.6 meters per second per second.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="158977" data-asm-type="video"><div class="md-assembly-wrapper card-media" data-type="video" video-id="151070"><a data-id="151070" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/Explanation-gravitational-force-Isaac-Newton-1687/-158977"><img src="https://cdn.britannica.com/70/151070-138-3B889A11/Explanation-gravitational-force-Isaac-Newton-1687.jpg?w=800&h=450&c=crop" alt="How gravity works on Earth and in the universe" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/0LrHfaHN.m3u8" } ], "image": "https://cdn.britannica.com/70/151070-138-3B889A11/Explanation-gravitational-force-Isaac-Newton-1687.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/WtGLM3NC", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/yW2dgwjA.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="151070">How gravity works on Earth and in the universe</span><span>Learn about the concept of gravitational force in Newton's theory of gravitation.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/science/gravity-physics/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">The works of <span id="ref377125"></span><a href="https://www.britannica.com/biography/Isaac-Newton" class="md-crosslink " data-show-preview="true">Isaac Newton</a> and <a href="https://www.britannica.com/biography/Albert-Einstein" class="md-crosslink " data-show-preview="true">Albert Einstein</a> dominate the development of gravitational theory. Newton’s classical theory of gravitational force held sway from his <em>Principia</em>, published in 1687, until Einstein’s <a href="https://www.britannica.com/science/work-physics" class="md-crosslink autoxref " data-show-preview="true">work</a> in the early 20th century. Newton’s theory is sufficient even today for all but the most precise applications. Einstein’s theory of <a href="https://www.britannica.com/science/general-relativity" class="md-crosslink autoxref " data-show-preview="true">general relativity</a> predicts only minute quantitative differences from the Newtonian theory except in a few special cases. The major significance of Einstein’s theory is its radical <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="conceptual" href="https://www.merriam-webster.com/dictionary/conceptual" data-type="MW">conceptual</a> departure from classical theory and its <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="implications" href="https://www.merriam-webster.com/dictionary/implications" data-type="MW">implications</a> for further growth in physical thought.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">The launch of <a href="https://www.britannica.com/science/space-physics-and-metaphysics" class="md-crosslink autoxref " data-show-preview="true">space</a> vehicles and developments of research from them have led to great improvements in measurements of gravity around Earth, other planets, and the Moon and in experiments on the nature of gravitation.</p><span class="marker MOD3 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref61463"> <h2 class="h1">Development of gravitational theory</h2> <section data-level="2" id="ref61464"> <h2 class="h2">Early concepts</h2> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">Newton argued that the movements of celestial bodies and the free fall of objects on Earth are determined by the same force. The classical Greek philosophers, on the other hand, did not consider the celestial bodies to be affected by gravity, because the bodies were observed to follow perpetually repeating nondescending trajectories in the sky. Thus, <span id="ref286998"></span><a href="https://www.britannica.com/biography/Aristotle" class="md-crosslink " data-show-preview="true">Aristotle</a> considered that each heavenly body followed a particular “natural” motion, unaffected by external causes or agents. Aristotle also believed that massive earthly objects possess a natural tendency to move toward <span id="ref286999"></span>Earth’s center. Those Aristotelian concepts prevailed for centuries along with two others: that a body moving at constant speed requires a continuous force acting on it and that force must be applied by contact rather than interaction at a distance. These ideas were generally held until the 16th and early 17th centuries, thereby <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="impeding" href="https://www.britannica.com/dictionary/impeding" data-type="EB">impeding</a> an understanding of the true principles of motion and precluding the development of ideas about universal gravitation. This impasse began to change with several scientific contributions to the problem of earthly and celestial motion, which in turn set the stage for Newton’s later gravitational theory.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">The 17th-century German astronomer <span id="ref287001"></span><a href="https://www.britannica.com/biography/Johannes-Kepler" class="md-crosslink " data-show-preview="true">Johannes Kepler</a> accepted the argument of <a href="https://www.britannica.com/biography/Nicolaus-Copernicus" class="md-crosslink " data-show-preview="true">Nicolaus Copernicus</a> (which goes back to <a href="https://www.britannica.com/biography/Aristarchus-of-Samos" class="md-crosslink " data-show-preview="true">Aristarchus of Samos</a>) that the planets <span id="ref287002"></span><a href="https://www.britannica.com/science/orbit-astronomy" class="md-crosslink " data-show-preview="true">orbit</a> the <span id="ref287003"></span><a href="https://www.britannica.com/place/Sun" class="md-crosslink " data-show-preview="true">Sun</a>, not Earth. Using the improved measurements of planetary movements made by the Danish astronomer <a href="https://www.britannica.com/biography/Tycho-Brahe-Danish-astronomer" class="md-crosslink " data-show-preview="true">Tycho Brahe</a> during the 16th century, Kepler described the planetary orbits with simple geometric and arithmetic relations. <span id="ref914145"></span><a href="https://www.britannica.com/science/Keplers-laws-of-planetary-motion" class="md-crosslink " data-show-preview="true">Kepler’s three quantitative laws of planetary motion</a> are:</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/all-about-physics-quiz" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/03/221503-131-D7173869/Italian-physicist-Guglielmo-Marconi-at-work-on-his-yacht-Electra.jpg" alt="Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920." class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">All About Physics Quiz</div> </div> </a><div class="one-good-fact-module"> </div><span class="marker MOD5 mod-inline"></span> <ol><li><div>The planets describe elliptic orbits, of which the Sun occupies one focus (a focus is one of two points inside an <a href="https://www.britannica.com/science/ellipse" class="md-crosslink " data-show-preview="true">ellipse</a>; any ray coming from one of them bounces off a side of the <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="ellipse" href="https://www.britannica.com/dictionary/ellipse" data-type="EB">ellipse</a> and goes through the other focus).</div></li><li><div>The line joining a <a href="https://www.britannica.com/science/planet" class="md-crosslink autoxref " data-show-preview="true">planet</a> to the Sun sweeps out equal areas in equal times.</div></li><li><div>The square of the period of revolution of a planet is proportional to the cube of its average distance from the Sun.</div></li></ol> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">During this same period the Italian astronomer and natural philosopher <span id="ref287004"></span><a href="https://www.britannica.com/biography/Galileo-Galilei" class="md-crosslink " data-show-preview="true">Galileo Galilei</a> made progress in understanding “natural” <span id="ref287005"></span><a href="https://www.britannica.com/science/motion-mechanics" class="md-crosslink " data-show-preview="true">motion</a> and simple accelerated motion for earthly objects. He realized that bodies that are uninfluenced by forces continue indefinitely to move and that force is necessary to change motion, not to maintain constant motion. In studying how objects fall toward Earth, Galileo discovered that the motion is one of constant <span id="ref287006"></span><a href="https://www.britannica.com/science/acceleration" class="md-crosslink " data-show-preview="true">acceleration</a>. He demonstrated that the distance a falling body travels from rest in this way varies as the square of the time. As noted above, the acceleration due to gravity at the surface of Earth is about 9.8 meters per second per second. Galileo was also the first to show by experiment that bodies fall with the same acceleration whatever their <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="composition" href="https://www.merriam-webster.com/dictionary/composition" data-type="MW">composition</a> (the weak principle of equivalence).</p><span class="marker MOD6 mod-inline"></span> </section> </section><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article> </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":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":7,"pageId":242523,"pageLength":718,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/libs/jquery-3.5.0.min.js?v=3.133.9"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-133/dist/topic-page.js?v=3.133.9' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"A","adLeg":"A","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":true} </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

Gravity | Definition, Physics, & Facts | Britannica