Earth | Definition, Size, Composition, Temperature, Mass, & Facts

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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/place/Earth">Earth</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="/place/Earth">Introduction & Top Questions</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref54194"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/place/Earth/Basic-planetary-data">Basic planetary data</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref54195"><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="/place/Earth/Basic-planetary-data#ref54195">The atmosphere and hydrosphere</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref54196"><a class="w-100 link-gray-900" href="/place/Earth/The-atmosphere">The atmosphere</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54197"><a class="w-100 link-gray-900" href="/place/Earth/The-atmosphere#ref54197">The hydrosphere</a></li></ul></div></li><li data-target="#ref54198"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/place/Earth/The-outer-shell">The outer shell</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref54199"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/place/Earth/The-interior">The interior</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref54200"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/place/Earth/The-interior#ref54200">The geomagnetic field and magnetosphere</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref242081"><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="/place/Earth/Development-of-Earths-structure-and-composition">Development of Earth’s structure and composition</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref242082"><a class="w-100 link-gray-900" href="/place/Earth/Accretion-of-the-early-Earth">Accretion of the early Earth</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref242083"><a class="w-100 link-gray-900" href="/place/Earth/Effects-of-planetesimal-impacts">Effects of planetesimal impacts</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref242084"><a class="w-100 link-gray-900" href="/place/Earth/Planetary-differentiation">Planetary differentiation</a></li></ul></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/place/Earth/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/Earth">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/place/Earth/images-videos">Images, Videos & Interactives</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/25/160325-050-EB1C8FB7/image-instruments-Earth-satellite-NASA-Suomi-National-2012.jpg" data-href="/media/1/175962/169506" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/25/160325-004-AD594C66/image-instruments-Earth-satellite-NASA-Suomi-National-2012.jpg" alt="Earth" height="50" /> </a> <a href="/video/universe/203957" data-href="/media/1/175962/203957" 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/00/185400-138-6E452A70/universe.jpg?w=400&h=225&c=crop" alt="Examine the observable universe's place within the whole 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="" data-href="/media/1/175962/276091" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/18/238518-049-AC2B446B/planets-solar-system-size-comparison.jpg" alt="Planets of Our Solar System" height="50" /> </a> 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Lunine</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Professor of Theoretical Planetary Physics, Lunar and Planetary Laboratory, University of Arizona, Tucson. Author of <i>Earth: Evolution of a Habitable World</i>.</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"> Jonathan I. Lunine</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/Clark-R-Chapman/3919" > <div class="editor-title font-16 font-weight-bold">Clark R. Chapman</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Senior Scientist, Department of Space Studies, Southwest Research Institute, Boulder, Colorado. Coauthor of <em>Cosmic Catastrophes</em>; author of <em>Planets of Rock and Ice</em>.</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"> Clark R. Chapman</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/place/Earth/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="2025-02-13T00:00:00CST" >Feb 13, 2025</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/place/Earth/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> <script type="application/ld+json"> { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type" : "Question", "name" : "<div>What is Earth?<\/div><em><\/em>", "acceptedAnswer" : { "@type" : "Answer", "text" : "Earth is the third <a href=\"https:\/\/www.britannica.com\/science\/planet\">planet<\/a> from the <a href=\"https:\/\/www.britannica.com\/place\/Sun\">Sun<\/a> and the fifth largest planet in the <a href=\"https:\/\/www.britannica.com\/science\/solar-system\">solar system<\/a> in terms of size and mass. Its near-surface environments are the only places in the <a href=\"https:\/\/www.britannica.com\/science\/universe\">universe<\/a> known to harbour life." } } , { "@type" : "Question", "name" : "<div>Where is Earth in the Milky Way Galaxy?<\/div><em><\/em>", "acceptedAnswer" : { "@type" : "Answer", "text" : "Earth is located in the Orion-Cygnus Arm, one of the four spiral arms of the <a href=\"https:\/\/www.britannica.com\/place\/Milky-Way-Galaxy\">Milky Way<\/a>, which lies about two-thirds of the way from the centre of the Galaxy." } } , { "@type" : "Question", "name" : "<div>What is Earth named for?<\/div><em><\/em>", "acceptedAnswer" : { "@type" : "Answer", "text" : "Earth\u2019s name in English, the international language of <a href=\"https:\/\/www.britannica.com\/science\/astronomy\">astronomy<\/a>, derives from <a href=\"https:\/\/www.britannica.com\/topic\/Old-English-language\">Old English<\/a> and Germanic words for <em>ground<\/em> and <em>earth<\/em>, and it is the only name for a <a href=\"https:\/\/www.britannica.com\/science\/planet\">planet<\/a> of the <a href=\"https:\/\/www.britannica.com\/science\/solar-system\">solar system<\/a> that does not come from Greco-Roman mythology." } } , { "@type" : "Question", "name" : "<div>What was Earth like when it was first formed?<\/div><em><\/em>", "acceptedAnswer" : { "@type" : "Answer", "text" : "Earth and the other planets in the solar system formed about 4.6 billion years ago. The early Earth had no <a href=\"https:\/\/www.britannica.com\/science\/ozone-layer\">ozone layer<\/a> and no free oxygen, lacked oceans, and was very hot." } } , { "@type" : "Question", "name" : "<div>What does Earth look like?<\/div><em><\/em>", "acceptedAnswer" : { "@type" : "Answer", "text" : "Viewed from another planet, Earth would appear bright and bluish in colour. In latitudinal belts, swirling white <a href=\"https:\/\/www.britannica.com\/science\/cloud-meteorology\">cloud<\/a> patterns of midlatitude and <a href=\"https:\/\/www.britannica.com\/science\/tropical-storm\">tropical storms<\/a> can be seen. The polar regions would appear white because of ice, the oceans a dark blue-black, the <a href=\"https:\/\/www.britannica.com\/science\/desert\">deserts<\/a> a tawny beige, and forests and jungles a vibrant green." } } ] } </script> <div class="top-questions qa-accordion d-flex flex-column module-spacing"><div class="font-weight-bold font-14 mb-5"> Top Questions </div><div id="intent-accordion" class="md-intent-accordion"><div class="top-question bg-gray-50 rounded" data-value="1"> <h3 class="accordion--question font-14 font-weight-normal cursor-pointer rounded"><div class="pe-none d-flex justify-content-between align-items-center"><div>What is Earth?</div><em class="material-icons" data-icon="expand_more"></em></div></h3> <div class="accordion--answer hidden p-15 pt-5 font-16 mb-5"><div class="accordion--answer-copy"><p>Earth is the third <a href="https://www.britannica.com/science/planet" class="md-crosslink " data-show-preview="true">planet</a> from the <a href="https://www.britannica.com/place/Sun" class="md-crosslink " data-show-preview="true">Sun</a> and the fifth largest planet in the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink " data-show-preview="true">solar system</a> in terms of size and mass. Its near-surface environments are the only places in the <a href="https://www.britannica.com/science/universe" class="md-crosslink " data-show-preview="true">universe</a> known to harbour life.</p></div></div> </div><div class="top-question bg-gray-50 rounded" data-value="2"> <h3 class="accordion--question font-14 font-weight-normal cursor-pointer rounded"><div class="pe-none d-flex justify-content-between align-items-center"><div>Where is Earth in the Milky Way Galaxy?</div><em class="material-icons" data-icon="expand_more"></em></div></h3> <div class="accordion--answer hidden p-15 pt-5 font-16 mb-5"><div class="accordion--answer-copy"><p>Earth is located in the Orion-Cygnus Arm, one of the four spiral arms of the <a href="https://www.britannica.com/place/Milky-Way-Galaxy" class="md-crosslink " data-show-preview="true">Milky Way</a>, which lies about two-thirds of the way from the centre of the Galaxy.</p></div></div> </div><div class="top-question bg-gray-50 rounded" data-value="3"> <h3 class="accordion--question font-14 font-weight-normal cursor-pointer rounded"><div class="pe-none d-flex justify-content-between align-items-center"><div>What is Earth named for?</div><em class="material-icons" data-icon="expand_more"></em></div></h3> <div class="accordion--answer hidden p-15 pt-5 font-16 mb-5"><div class="accordion--answer-copy"><p>Earth’s name in English, the international language of <a href="https://www.britannica.com/science/astronomy" class="md-crosslink " data-show-preview="true">astronomy</a>, derives from <a href="https://www.britannica.com/topic/Old-English-language" class="md-crosslink " data-show-preview="true">Old English</a> and Germanic words for <em>ground</em> and <em>earth</em>, and it is the only name for a <a href="https://www.britannica.com/science/planet" class="md-crosslink " data-show-preview="true">planet</a> of the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink " data-show-preview="true">solar system</a> that does not come from Greco-Roman mythology.</p></div></div> </div><div class="top-question bg-gray-50 rounded" data-value="4"> <h3 class="accordion--question font-14 font-weight-normal cursor-pointer rounded"><div class="pe-none d-flex justify-content-between align-items-center"><div>What was Earth like when it was first formed?</div><em class="material-icons" data-icon="expand_more"></em></div></h3> <div class="accordion--answer hidden p-15 pt-5 font-16 mb-5"><div class="accordion--answer-copy"><p>Earth and the other planets in the solar system formed about 4.6 billion years ago. The early Earth had no <a href="https://www.britannica.com/science/ozone-layer" class="md-crosslink " data-show-preview="true">ozone layer</a> and no free oxygen, lacked oceans, and was very hot.</p></div></div> </div><div class="top-question bg-gray-50 rounded" data-value="5"> <h3 class="accordion--question font-14 font-weight-normal cursor-pointer rounded"><div class="pe-none d-flex justify-content-between align-items-center"><div>What does Earth look like?</div><em class="material-icons" data-icon="expand_more"></em></div></h3> <div class="accordion--answer hidden p-15 pt-5 font-16 mb-5"><div class="accordion--answer-copy"><p>Viewed from another planet, Earth would appear bright and bluish in colour. In latitudinal belts, swirling white <a href="https://www.britannica.com/science/cloud-meteorology" class="md-crosslink " data-show-preview="true">cloud</a> patterns of midlatitude and <a href="https://www.britannica.com/science/tropical-storm" class="md-crosslink " data-show-preview="true">tropical storms</a> can be seen. The polar regions would appear white because of ice, the oceans a dark blue-black, the <a href="https://www.britannica.com/science/desert" class="md-crosslink " data-show-preview="true">deserts</a> a tawny beige, and forests and jungles a vibrant green.</p></div></div> </div><button class="show-more-button js-toggle-top-questions btn btn-unstyled font-14 d-flex pr-10 rounded-sm"><em class="material-icons" data-icon="expand_more"></em></button></div></div><div class="bg-gray-50 p-15 rounded module-spacing recent-news d-flex flex-column float-false"> <div> <h2 class="font-weight-bold font-14 m-0 d-inline"> News <span class="text-gray-600">•</span> </h2> <div class="recent-news-item first-recent-news-item d-inline"> <a class="font-14 gtm-ap-news-link" href="/news/175962/5c353e2ee53bb1ecd68a562611d54062" rel="nofollow">Why asteroid 2024 YR4 is unlikely to hit Earth in 2032 and how scientists keep track</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 13, 2025, 6:54 PM ET (AP) <button class="btn btn-link d-inline p-0 font-12 js-toggle-recent-news"> <span class="text-gray-500">...</span><span>(Show more)</span> </button> </span> </div> </div> <div class="rest-of-recent-news-items"> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="/news/175962/87b227fc0a5ef3c95203091d73c5ebb7" rel="nofollow">Innovators gear up work on ‘green’ hydrogen plane with plans for nonstop 9-day trip around Earth</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 13, 2025, 6:07 PM ET (AP) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="/news/175962/1ee410a50cb2413d62c208ecc6946614" rel="nofollow">NASA's 2 stuck astronauts may return to Earth sooner under new plan</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 11, 2025, 5:18 PM ET (AP) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="/news/175962/f0d4e29fc8052fd3fb162e9cbe745309" rel="nofollow">Correction: Poland-Astronauts-Mission story</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 6, 2025, 11:20 AM ET (AP) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="/news/175962/2c44da947d4b892448d18b61202a1457" rel="nofollow">The US is freezing and La Nina usually eases warming. Earth just set another heat record anyway</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 6, 2025, 6:08 AM ET (AP) </span> </div> <button class="js-toggle-recent-news d-flex btn btn-unstyled font-14 pr-10 rounded-sm mt-10" aria-label="Toggle additional news items"> Show less <em class="material-icons" data-icon="expand_less"></em> </button> </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="ref514433"></span>Earth</strong>, third <a href="https://www.britannica.com/science/planet" class="md-crosslink " data-show-preview="true">planet</a> from the <a href="https://www.britannica.com/place/Sun" class="md-crosslink " data-show-preview="true">Sun</a> and the fifth largest planet in the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink " data-show-preview="true">solar system</a> in terms of size and mass. Its single most outstanding feature is that its near-surface <a href="https://www.britannica.com/science/environment" class="md-crosslink " data-show-preview="true">environments</a> are the only places in the <a href="https://www.britannica.com/science/universe" class="md-crosslink " data-show-preview="true">universe</a> known to harbour life. It is <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="designated" href="https://www.britannica.com/dictionary/designated" data-type="EB">designated</a> by the symbol ♁. Earth’s name in <a href="https://www.britannica.com/topic/English-language" class="md-crosslink " data-show-preview="true">English</a>, the international language of <a href="https://www.britannica.com/science/astronomy" class="md-crosslink " data-show-preview="true">astronomy</a>, derives from <a href="https://www.britannica.com/topic/Old-English-language" class="md-crosslink " data-show-preview="true">Old English</a> and Germanic words for <em>ground</em> and <em>earth</em>, and it is the only name for a <a href="https://www.britannica.com/science/planet" class="md-crosslink " data-show-preview="true">planet</a> of the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink " data-show-preview="true">solar system</a> that does not come from Greco-Roman mythology. Earth is part of the "<a href="https://www.britannica.com/topic/observable-universe" class="md-crosslink " data-show-preview="true">observable universe</a>," the region of <a href="https://www.britannica.com/science/space-physics-and-metaphysics" class="md-crosslink autoxref " data-show-preview="true">space</a> that <a href="https://www.britannica.com/topic/human-being" class="md-crosslink " data-show-preview="true">humans</a> can actually or theoretically observe with the aid of <a href="https://www.britannica.com/technology/technology" class="md-crosslink " data-show-preview="true">technology</a>. Unlike the observable universe, the <a href="https://www.britannica.com/science/universe" class="md-crosslink " data-show-preview="true">universe</a> is possibly <a href="https://www.britannica.com/science/infinity-mathematics" class="md-crosslink " data-show-preview="true">infinite</a>.</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="203957" data-asm-type="video"><div class="md-assembly-wrapper card-media" data-type="video" video-id="185400"><a data-id="185400" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/universe/-203957"><img src="https://cdn.britannica.com/00/185400-138-6E452A70/universe.jpg?w=800&h=450&c=crop" alt="Examine the observable universe's place within the whole universe" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/mMJeLTfP.m3u8" } ], "image": "https://cdn.britannica.com/00/185400-138-6E452A70/universe.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/UEZIUWEw", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/t1e6VW3d.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="185400">Examine the observable universe's place within the whole universe</span><span>Learn about defining and measuring the observable universe within the “whole” universe.</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="/place/Earth/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">Since the Copernican revolution of the 16th century, at which time the Polish astronomer <a href="https://www.britannica.com/biography/Nicolaus-Copernicus" class="md-crosslink " data-show-preview="true">Nicolaus Copernicus</a> proposed a Sun-centred model of the universe (<em>see</em> <span id="ref514436"></span><a href="https://www.britannica.com/science/heliocentrism" class="md-crosslink " data-show-preview="true">heliocentric system</a>), <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="enlightened" href="https://www.merriam-webster.com/dictionary/enlightened" data-type="MW">enlightened</a> thinkers have regarded Earth as a planet like the others of the solar system. <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="Concurrent" href="https://www.merriam-webster.com/dictionary/Concurrent" data-type="MW">Concurrent</a> sea voyages provided practical proof that Earth is a globe, just as <a href="https://www.britannica.com/biography/Galileo-Galilei" class="md-crosslink " data-show-preview="true">Galileo</a>’s use of his newly invented telescope in the early 17th century soon showed various other planets to be globes as well. It was only after the dawn of the space age, however, when photographs from rockets and orbiting <a href="https://www.britannica.com/technology/spacecraft" class="md-crosslink " data-show-preview="true">spacecraft</a> first captured the dramatic curvature of Earth’s <a href="https://www.britannica.com/science/horizon-astronomy" class="md-crosslink " data-show-preview="true">horizon</a>, that the <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="conception" href="https://www.merriam-webster.com/dictionary/conception" data-type="MW">conception</a> of Earth as a roughly spherical planet rather than as a flat entity was verified by direct <a href="https://www.britannica.com/topic/human-being" class="md-crosslink autoxref " data-show-preview="true">human</a> observation. Humans first witnessed Earth as a complete orb floating in the inky blackness of space in December 1968 when <span id="ref514437"></span><a href="https://www.britannica.com/science/Apollo-space-program" class="md-crosslink " data-show-preview="true">Apollo</a> 8 carried astronauts around the <a href="https://www.britannica.com/place/Moon" class="md-crosslink autoxref " data-show-preview="true">Moon</a>. Robotic space probes on their way to destinations beyond Earth, such as the <a href="https://www.britannica.com/topic/Galileo-spacecraft" class="md-crosslink " data-show-preview="true">Galileo</a> and the <a href="https://www.britannica.com/topic/Near-Earth-Asteroid-Rendezvous-Shoemaker" class="md-crosslink autoxref " data-show-preview="true">Near Earth Asteroid Rendezvous</a> (NEAR) spacecraft in the 1990s, also looked back with their cameras to provide other unique portraits of the planet.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">Viewed from another planet in the solar system, Earth would appear bright and bluish in colour. Easiest to see through a large telescope would be its atmospheric features, chiefly the swirling white <a href="https://www.britannica.com/science/cloud-meteorology" class="md-crosslink autoxref " data-show-preview="true">cloud</a> patterns of midlatitude and <a href="https://www.britannica.com/science/tropical-storm" class="md-crosslink " data-show-preview="true">tropical storms</a>, ranged in roughly latitudinal belts around the <a href="https://www.britannica.com/science/planet" class="md-crosslink " data-show-preview="true">planet</a>. The polar regions also would appear a brilliant white, because of the clouds above and the snow and ice below. Beneath the changing patterns of clouds would appear the much darker blue-black oceans, interrupted by occasional tawny patches of <a href="https://www.britannica.com/science/desert" class="md-crosslink " data-show-preview="true">desert</a> lands. The green landscapes that harbour most human life would not be easily seen from space. Not only do they <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constitute" href="https://www.merriam-webster.com/dictionary/constitute" data-type="MW">constitute</a> a modest fraction of the land area, which itself is less than one-third of Earth’s surface, but they are often obscured by <a href="https://www.britannica.com/science/cloud-meteorology" class="md-crosslink " data-show-preview="true">clouds</a>. Over the course of the seasons, some changes in the storm patterns and cloud belts on Earth would be observed. Also prominent would be the growth and recession of the <a href="https://www.britannica.com/science/winter" class="md-crosslink autoxref " data-show-preview="true">winter</a> snowcap across land areas of the Northern Hemisphere.</p><span class="marker MOD3 mod-inline"></span><div class="mb-20"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="276091" data-asm-type="infogram"><div class="md-assembly-wrapper card-media" data-type="infogram"><script id="infogram_0__/kq1AKnmJvA2RSNx54jy1" src="https://e.infogram.com/js/dist/embed.js?Itp" type="text/javascript" title="Planets of Our Solar System"></script></div></figure></div></div><span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">Scientists have applied the full battery of modern instrumentation to studying Earth in ways that have not yet been possible for the other planets; thus, much more is known about its structure and <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>. This detailed knowledge, in turn, provides deeper insight into the mechanisms by which planets in general cool down, by which their <a href="https://www.britannica.com/science/magnetic-field" class="md-crosslink " data-show-preview="true">magnetic fields</a> are generated, and by which the separation of lighter elements from heavier ones as planets develop their internal structure releases additional <a href="https://www.britannica.com/science/energy" class="md-crosslink autoxref " data-show-preview="true">energy</a> for geologic processes and alters crustal <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="compositions" href="https://www.merriam-webster.com/dictionary/compositions" data-type="MW">compositions</a>.</p><span class="marker MOD4 mod-inline"></span><span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">Earth’s surface is traditionally subdivided into seven continental masses: <a href="https://www.britannica.com/place/Africa" class="md-crosslink " data-show-preview="true">Africa</a>, <a href="https://www.britannica.com/place/Antarctica" class="md-crosslink " data-show-preview="true">Antarctica</a>, <a href="https://www.britannica.com/place/Asia" class="md-crosslink " data-show-preview="true">Asia</a>, <a href="https://www.britannica.com/place/Australia" class="md-crosslink " data-show-preview="true">Australia</a>, <a href="https://www.britannica.com/place/Europe" class="md-crosslink " data-show-preview="true">Europe</a>, <a href="https://www.britannica.com/place/North-America" class="md-crosslink " data-show-preview="true">North America</a>, and <a href="https://www.britannica.com/place/South-America" class="md-crosslink " data-show-preview="true">South America</a>. These continents are surrounded by five major bodies of water: the <a href="https://www.britannica.com/place/Arctic" class="md-crosslink " data-show-preview="true">Arctic</a>, <a href="https://www.britannica.com/place/Atlantic-Ocean" class="md-crosslink " data-show-preview="true">Atlantic</a>, <a href="https://www.britannica.com/place/Indian-Ocean" class="md-crosslink " data-show-preview="true">Indian</a>, <a href="https://www.britannica.com/place/Pacific-Ocean" class="md-crosslink " data-show-preview="true">Pacific</a>, and <a href="https://www.britannica.com/place/Southern-Ocean" class="md-crosslink " data-show-preview="true">Southern</a> oceans. However, it is convenient to consider separate parts of Earth in terms of concentric, roughly spherical layers. Extending from the interior outward, these are the core, the mantle, the crust (including the rocky surface), the <a href="https://www.britannica.com/science/hydrosphere" class="md-crosslink " data-show-preview="true">hydrosphere</a> (predominantly the <a href="https://www.britannica.com/science/ocean" class="md-crosslink " data-show-preview="true">oceans</a>, which fill in <a href="https://www.britannica.com/science/cyclone-meteorology" class="md-crosslink autoxref " data-show-preview="true">low</a> places in the crust), the <a href="https://www.britannica.com/science/atmosphere" class="md-crosslink " data-show-preview="true">atmosphere</a> (itself divided into spherical zones such as the <a href="https://www.britannica.com/science/troposphere" class="md-crosslink " data-show-preview="true">troposphere</a>, where <a href="https://www.britannica.com/science/weather" class="md-crosslink autoxref " data-show-preview="true">weather</a> occurs, and the <a href="https://www.britannica.com/science/stratosphere" class="md-crosslink " data-show-preview="true">stratosphere</a>, where lies the <a href="https://www.britannica.com/science/ozone-layer" class="md-crosslink " data-show-preview="true">ozone layer</a> that shields Earth’s surface and its organisms against the <a href="https://www.britannica.com/place/Sun" class="md-crosslink " data-show-preview="true">Sun</a>’s ultraviolet rays), and the <a href="https://www.britannica.com/science/magnetosphere" class="md-crosslink " data-show-preview="true">magnetosphere</a> (an enormous region in space where Earth’s magnetic field dominates the behaviour of electrically charged particles coming from the Sun).</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/27-true-or-false-questions-from-britannicas-most-difficult-science-quizzes" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg" alt="Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph." 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">27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes</div> </div> </a><div class="one-good-fact-module"> </div><span class="marker MOD5 mod-inline"></span><span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">Knowledge about these divisions is summarized in this astronomically oriented overview. The discussion complements other treatments oriented to the <a href="https://www.britannica.com/science/Earth-sciences" class="md-crosslink " data-show-preview="true">Earth sciences</a> and life sciences. Earth’s figure and dimensions are discussed in the article <a href="https://www.britannica.com/science/geodesy-science" class="md-crosslink " data-show-preview="true">geodesy</a>. Its magnetic field is treated in the article <a href="https://www.britannica.com/science/geomagnetic-field" class="md-crosslink " data-show-preview="true">geomagnetic field</a>. The early <a href="https://www.britannica.com/science/evolution-scientific-theory" class="md-crosslink autoxref " data-show-preview="true">evolution</a> of the solid Earth and its atmosphere and oceans is covered in <a href="https://www.britannica.com/science/geologic-history-of-Earth" class="md-crosslink " data-show-preview="true">geologic history of Earth</a>. The geologic and <a href="https://www.britannica.com/science/biological-development" class="md-crosslink autoxref " data-show-preview="true">biological development</a> of Earth, including its surface features and the processes by which they are created and modified, are discussed in <a href="https://www.britannica.com/science/geochronology" class="md-crosslink " data-show-preview="true">geochronology</a>, <a href="https://www.britannica.com/science/continental-landform" class="md-crosslink " data-show-preview="true">continental landform</a>, and <a href="https://www.britannica.com/science/plate-tectonics" class="md-crosslink " data-show-preview="true">plate tectonics</a>. The behaviour of the atmosphere and of its <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="tenuous" href="https://www.merriam-webster.com/dictionary/tenuous" data-type="MW">tenuous</a>, ionized outer reaches is treated in <a href="https://www.britannica.com/topic/evolution-of-the-atmosphere-1703862" class="md-crosslink " data-show-preview="true">atmosphere</a>, while the <a href="https://www.britannica.com/science/water-cycle" class="md-crosslink autoxref " data-show-preview="true">water cycle</a> and major hydrologic features are described in <a href="https://www.britannica.com/science/hydrosphere" class="md-crosslink " data-show-preview="true">hydrosphere</a>, <a href="https://www.britannica.com/science/ocean" class="md-crosslink " data-show-preview="true">ocean</a>, and <a href="https://www.britannica.com/science/river" class="md-crosslink " data-show-preview="true">river</a>. The solid Earth as a <a href="https://www.britannica.com/science/field-physics" class="md-crosslink autoxref " data-show-preview="true">field</a> of study is covered in <a href="https://www.britannica.com/science/geology" class="md-crosslink " data-show-preview="true">geologic sciences</a>, the methods and instruments employed to investigate Earth’s surface and interior are discussed in <a href="https://www.britannica.com/topic/Earth-exploration" class="md-crosslink " data-show-preview="true">Earth exploration</a>, and the history of the study of Earth from antiquity to modern times is surveyed in <a href="https://www.britannica.com/science/Earth-sciences" class="md-crosslink " data-show-preview="true">Earth sciences</a>. The global <a href="https://www.britannica.com/science/ecosystem" class="md-crosslink autoxref " data-show-preview="true">ecosystem</a> of living organisms and their life-supporting stratum are detailed in <a href="https://www.britannica.com/science/biosphere" class="md-crosslink " data-show-preview="true">biosphere</a>.</p><span class="marker MOD6 mod-inline"></span></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":9,"pageId":175962,"pageLength":916,"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":"D","adLeg":"C","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>

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Earth | Definition, Size, Composition, Temperature, Mass, & Facts | Britannica