Editing Earth (section)

=== Size and shape ===
{{Main|Figure of the Earth}}
{{Further|Earth radius|Earth's circumference|Spherical Earth{{!}}Earth curvature|Geomorphology}}
{{See also|List of highest mountains on Earth}}
[[File:Earth2014shape SouthAmerica small.jpg|thumb|upright=1.3|Earth's western hemisphere showing topography relative to Earth's center instead of to [[mean sea level]], as in common topographic maps]]
[[Figure of the Earth|Earth has a rounded shape]], through [[hydrostatic equilibrium]],<ref name="Horner 2021">{{cite web | last=Horner | first=Jonti | title=I've always wondered: why are the stars, planets and moons round, when comets and asteroids aren't? | website=The Conversation | date=16 July 2021 | url= https://theconversation.com/ive-always-wondered-why-are-the-stars-planets-and-moons-round-when-comets-and-asteroids-arent-160541 | access-date=3 March 2023 | archive-date=3 March 2023 | archive-url=https://web.archive.org/web/20230303211236/https://theconversation.com/amp/ive-always-wondered-why-are-the-stars-planets-and-moons-round-when-comets-and-asteroids-arent-160541 | url-status=live }}</ref> with an average diameter of {{convert|12742|km|mi}}, making it the [[List of Solar System objects by size|fifth largest]] [[Planet#Planetary-mass object|planetary sized]] and largest [[terrestrial planet|terrestrial object]] of the [[Solar System]].<ref>{{Cite web |last=Lea |first=Robert |date=6 July 2021 |title=How big is Earth? |url=https://www.space.com/17638-how-big-is-earth.html |archive-url=https://web.archive.org/web/20240109225632/https://www.space.com/17638-how-big-is-earth.html |archive-date=9 January 2024 |access-date=11 January 2024 |website=Space.com |language=en}}</ref>

Due to [[Earth's rotation]] it has the shape of an [[Earth ellipsoid|ellipsoid]], [[equatorial bulge|bulging at its equator]]; its diameter is {{convert|43|km|mi}} longer there than at its [[Geographical pole|poles]].<ref name="ngdc2006" /><ref name= "milbert_smith96" /> Earth's shape also has local [[topography|topographic]] variations; the largest local variations, like the [[Mariana Trench]] ({{convert|10925|m|ft|disp=or|abbr=}} below local sea level),<ref>{{Cite journal |last1= Stewart|first1=Heather A.|last2=Jamieson|first2=Alan J.|date=2019|title=The five deeps: The location and depth of the deepest place in each of the world's oceans| journal=Earth-Science Reviews |language=en |volume=197 |pages= 102896 |doi= 10.1016/j.earscirev.2019.102896|bibcode=2019ESRv..19702896S|issn=0012-8252|doi-access=free}}</ref> shortens Earth's average radius by 0.17% and [[Mount Everest]] ({{convert|8848|m|ft|disp=or}} above local sea level) lengthens it by 0.14%.{{refn|group=n| If Earth were shrunk to the size of a [[billiard ball]], some areas of Earth such as large mountain ranges and oceanic trenches would feel like tiny imperfections, whereas much of the planet, including the [[Great Plains]] and the [[abyssal plain]]s, would feel smoother.<ref>{{cite web |url=http://billiards.colostate.edu/bd_articles/2013/june13.pdf |title=Is a Pool Ball Smoother than the Earth? |publisher=Billiards Digest |date=1 June 2013 |access-date= 26 November 2014 |archive-date=4 September 2014 |archive-url= https://web.archive.org/web/20140904201722/http://billiards.colostate.edu/bd_articles/2013/june13.pdf |url-status=live }}</ref>}}<ref>{{cite web|url= https://serc.carleton.edu/quantskills/activities/botec_himalayas.html|title=Back-of-the-Envelope Calculations: Scale of the Himalayas|work=[[Carleton University]] |last1=Tewksbury|first1=Barbara|access-date=19 October 2020|archive-date=23 October 2020 |archive-url= https://web.archive.org/web/20201023091247/https://serc.carleton.edu/quantskills/activities/botec_himalayas.html|url-status=live}}</ref> Since Earth's surface is farthest out from its [[center of mass]] at its equatorial bulge, the summit of the volcano [[Chimborazo]] in Ecuador ({{convert|6384.4|km|mi|1|abbr=on|disp=or}}) is its farthest point out.<ref name=ps20_5_16 /><ref>{{cite web |url= https://www.npr.org/templates/story/story.php?storyId=9428163 |title=The 'Highest' Spot on Earth |last1=Krulwich |first1=Robert |author-link=Robert Krulwich |work= NPR.org |date=7 April 2007 |access-date=31 July 2012 |archive-date=30 January 2013 |archive-url= https://web.archive.org/web/20130130164111/http://www.npr.org/templates/story/story.php?storyId=9428163 |url-status=live }}</ref> Parallel to the rigid land topography [[Ocean surface topography|the ocean exhibits a more dynamic topography]].<ref>{{Cite web |title=Ocean Surface Topography |url=https://sealevel.jpl.nasa.gov/ocean-observation/ocean-surface-topography |access-date=16 June 2022 |website=Ocean Surface Topography from Space |publisher=[[NASA]] |language=en |archive-date=29 July 2021 |archive-url= https://web.archive.org/web/20210729095927/https://sealevel.jpl.nasa.gov/ocean-observation/ocean-surface-topography/ |url-status=live }}</ref>

To measure the local variation of Earth's topography, [[geodesy]] employs an idealized Earth producing a [[geoid]] shape. Such a shape is gained if the ocean is idealized, covering Earth completely and without any perturbations such as tides and winds. The result is a smooth but irregular geoid surface, providing a mean sea level as a reference level for topographic measurements.<ref>{{Cite web |title=What is the geoid?|url=https://oceanservice.noaa.gov/facts/geoid.html | website= oceanservice.noaa.gov |access-date=10 October 2020 |publisher=[[National Ocean Service]]|language=EN-US|archive-date=17 October 2020 |archive-url= https://web.archive.org/web/20201017000735/https://oceanservice.noaa.gov/facts/geoid.html|url-status=live}}</ref>