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.sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar sidebar-collapse nomobile nowraplinks"><tbody><tr><th class="sidebar-title" style="padding-bottom:0.4em;"><a href="/wiki/Geodesy" title="Geodesy">Geodesy</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"><a href="/wiki/File:Globe_Atlantic.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Globe_Atlantic.svg/120px-Globe_Atlantic.svg.png" decoding="async" width="120" height="121" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Globe_Atlantic.svg/180px-Globe_Atlantic.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Globe_Atlantic.svg/240px-Globe_Atlantic.svg.png 2x" data-file-width="717" data-file-height="721" /></a></span></td></tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Fundamentals</div><div class="sidebar-list-content mw-collapsible-content hlist"> <ul><li><a href="/wiki/Geodesy" title="Geodesy">Geodesy</a></li> <li><a href="/wiki/Geodynamics" title="Geodynamics">Geodynamics</a></li> <li><a href="/wiki/Geomatics" title="Geomatics">Geomatics</a></li> <li><a href="/wiki/History_of_geodesy" title="History of geodesy">History</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Concepts</div><div class="sidebar-list-content mw-collapsible-content hlist"> <ul><li><a href="/wiki/Geographical_distance" title="Geographical distance">Geographical distance</a></li> <li><a href="/wiki/Geoid" title="Geoid">Geoid</a></li> <li><a href="/wiki/Figure_of_the_Earth" title="Figure of the Earth">Figure of the Earth</a> <small>(<a href="/wiki/Earth_radius" title="Earth radius">radius</a> and <a class="mw-selflink selflink">circumference</a>)</small></li> <li><a href="/wiki/Geodetic_coordinates" title="Geodetic coordinates">Geodetic coordinates</a></li> <li><a href="/wiki/Geodetic_datum" title="Geodetic datum">Geodetic datum</a></li> <li><a href="/wiki/Geodesic" title="Geodesic">Geodesic</a></li> <li><a href="/wiki/Horizontal_position_representation" title="Horizontal position representation">Horizontal position representation</a></li> <li><span class="nowrap"><a href="/wiki/Latitude" title="Latitude">Latitude</a> / <a href="/wiki/Longitude" title="Longitude">Longitude</a></span></li> <li><a href="/wiki/Map_projection" title="Map projection">Map projection</a></li> <li><a href="/wiki/Reference_ellipsoid" class="mw-redirect" title="Reference ellipsoid">Reference ellipsoid</a></li> <li><a href="/wiki/Satellite_geodesy" title="Satellite geodesy">Satellite geodesy</a></li> <li><a href="/wiki/Spatial_reference_system" title="Spatial reference system">Spatial reference system</a></li> <li><a href="/wiki/Spatial_relation" title="Spatial relation">Spatial relations</a></li> <li><a href="/wiki/Vertical_position" title="Vertical position">Vertical positions</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Technologies</div><div class="sidebar-list-content mw-collapsible-content hlist"> <ul><li><a href="/wiki/Satellite_navigation" title="Satellite navigation">Global Nav. Sat. Systems (GNSSs)</a></li> <li><a href="/wiki/Global_Positioning_System" title="Global Positioning System">Global Pos. System (GPS)</a></li> <li><a href="/wiki/GLONASS" title="GLONASS">GLONASS <span style="font-size:85%;">(Russia)</span></a></li> <li><a href="/wiki/BeiDou" title="BeiDou">BeiDou (BDS) <span style="font-size:85%;">(China)</span></a></li> <li><a href="/wiki/Galileo_(satellite_navigation)" title="Galileo (satellite navigation)">Galileo <span style="font-size:85%;">(Europe)</span></a></li> <li><a href="/wiki/Indian_Regional_Navigation_Satellite_System" title="Indian Regional Navigation Satellite System">NAVIC <span style="font-size:85%;">(India)</span></a></li> <li><a href="/wiki/Quasi-Zenith_Satellite_System" title="Quasi-Zenith Satellite System">Quasi-Zenith Sat. Sys. (QZSS) <span style="font-size:85%;">(Japan)</span></a></li> <li><a href="/wiki/Discrete_Global_Grid" class="mw-redirect" title="Discrete Global Grid">Discrete Global Grid and Geocoding</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content"> <div class="sidebar-list mw-collapsible mw-collapsed plainlist"><div class="sidebar-list-title" style="color: var(--color-base)">Standards (history)</div><div class="sidebar-list-content mw-collapsible-content hlist"><table class="nowrap" style="width:100%;border-collapse:collapse;border-spacing:0px 0px;border:none;line-height:1.2em;"><tbody><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/Sea_Level_Datum_of_1929" class="mw-redirect" title="Sea Level Datum of 1929">NGVD 29</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Sea Level Datum 1929</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/OSGB36" class="mw-redirect" title="OSGB36">OSGB36</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Ordnance Survey Great Britain 1936</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/SK-42_reference_system" title="SK-42 reference system">SK-42</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Systema Koordinat 1942 goda</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/ED50" title="ED50">ED50</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> European Datum 1950</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/South_American_Datum#SAD69" title="South American Datum">SAD69</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> South American Datum 1969</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/GRS_80" class="mw-redirect" title="GRS 80">GRS 80</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Geodetic Reference System 1980</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/ISO_6709" title="ISO 6709">ISO 6709</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Geographic point coord. 1983</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/North_American_Datum#North_American_Datum_of_1983" title="North American Datum">NAD 83</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> North American Datum 1983</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/World_Geodetic_System" title="World Geodetic System">WGS 84</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> World Geodetic System 1984</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/North_American_Vertical_Datum_of_1988" title="North American Vertical Datum of 1988">NAVD 88</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> N. American Vertical Datum 1988</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/European_Terrestrial_Reference_System_1989" title="European Terrestrial Reference System 1989">ETRS89</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> European Terrestrial Ref. Sys. 1989</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/Restrictions_on_geographic_data_in_China" title="Restrictions on geographic data in China">GCJ-02</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Chinese obfuscated datum 2002</td></tr><tr style="vertical-align:top"><td style="text-align:left;padding-left:0.5em;"> <a href="/wiki/Geo_URI_scheme" title="Geo URI scheme">Geo URI</a></td><td style="text-align:right;font-size:90%;padding-right:0.55em;"> Internet link to a point 2010</td></tr></tbody></table> <ul><li><a href="/wiki/International_Terrestrial_Reference_System" class="mw-redirect" title="International Terrestrial Reference System">International Terrestrial Reference System</a></li> <li><a href="/wiki/SRID" class="mw-redirect" title="SRID">Spatial Reference System Identifier (SRID)</a></li> <li><a href="/wiki/Universal_Transverse_Mercator_coordinate_system" title="Universal Transverse Mercator coordinate system">Universal Transverse Mercator (UTM)</a></li></ul></div></div></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Geodesy" title="Template:Geodesy"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Geodesy" title="Template talk:Geodesy"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Geodesy" title="Special:EditPage/Template:Geodesy"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p><b>Earth's circumference</b> is the <a href="/wiki/Circumference" title="Circumference">distance</a> around <a href="/wiki/Earth" title="Earth">Earth</a>. Measured around the <a href="/wiki/Equator" title="Equator">equator</a>, it is 40,075.017 km (24,901.461 mi). Measured passing through the <a href="/wiki/Geographical_pole" title="Geographical pole">poles</a>, the circumference is 40,007.863 km (24,859.734 mi).<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Measurement of Earth's circumference has been important to <a href="/wiki/Navigation" title="Navigation">navigation</a> since ancient times. The first known scientific measurement and calculation was done by <a href="/wiki/Eratosthenes" title="Eratosthenes">Eratosthenes</a>, by comparing altitudes of the mid-day sun at two places a known north–south distance apart.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> He achieved a great degree of precision in his computation.<sup id="cite_ref-russo273277_3-0" class="reference"><a href="#cite_note-russo273277-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Treating the Earth as a <a href="/wiki/Sphere" title="Sphere">sphere</a>, its circumference would be its single most important measurement.<sup id="cite_ref-ShekharXiong2007_4-0" class="reference"><a href="#cite_note-ShekharXiong2007-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Earth deviates from spherical by about 0.3%, as characterized by <a href="/wiki/Flattening" title="Flattening">flattening</a>. </p><p><span class="anchor" id="Earth's_circumference_in_nautical_miles"></span> In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the <a href="/wiki/Nautical_mile" title="Nautical mile">nautical mile</a> in the seventeenth century and the <a href="/wiki/Metre" title="Metre">metre</a> in the eighteenth. Earth's polar circumference is very near to 21,600 nautical miles because the nautical mile was intended to express one <a href="/wiki/Minute_and_second_of_arc" title="Minute and second of arc"> minute</a> of latitude (see <a href="/wiki/Meridian_arc" title="Meridian arc">meridian arc</a>), which is 21,600 partitions of the polar circumference (that is 60 minutes × 360 degrees). The polar circumference is also close to 40,000 kilometres because <a href="/wiki/History_of_the_metre" title="History of the metre">the metre was originally defined</a> to be one ten millionth (i.e., a kilometre is one ten thousandth) of the arc from pole to equator (<a href="/wiki/Quarter_meridian" class="mw-redirect" title="Quarter meridian">quarter meridian</a>). The accuracy of measuring the circumference has improved since then, but the physical length of each unit of measure had remained close to what it was determined to be at the time, so the Earth's circumference is no longer a <a href="/wiki/Round_number" title="Round number">round number</a> in metres or nautical miles. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/History_of_geodesy" title="History of geodesy">History of geodesy</a>, <a href="/wiki/Spherical_Earth#History" title="Spherical Earth">Spherical Earth § History</a>, <a href="/wiki/Earth_radius#History" title="Earth radius">Earth radius § History</a>, and <a href="/wiki/Meridian_arc#History" title="Meridian arc">Meridian arc § History</a></div> <div class="mw-heading mw-heading3"><h3 id="Eratosthenes">Eratosthenes</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=2" title="Edit section: Eratosthenes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Eratosthenes.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Eratosthenes.png/220px-Eratosthenes.png" decoding="async" width="220" height="170" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/98/Eratosthenes.png/330px-Eratosthenes.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/98/Eratosthenes.png/440px-Eratosthenes.png 2x" data-file-width="701" data-file-height="542" /></a><figcaption>Illustration showing a portion of the globe showing a part of the African continent. The sun beams shown as two rays hitting earth at Syene and Alexandria. Angle of sun beam and the gnomons (vertical sticks) is shown at Alexandria which allowed Eratosthenes' estimate of the circumference of Earth.</figcaption></figure> <p>The measure of Earth's circumference is the most famous among the results obtained by <a href="/wiki/Eratosthenes" title="Eratosthenes">Eratosthenes</a>,<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> who estimated that the meridian has a length of 252,000 <a href="/wiki/Stadion_(unit)" title="Stadion (unit)">stadia</a>, with an error on the real value between −2.4% and +0.8% (assuming a value for the stadion between 155 and 160 metres;<sup id="cite_ref-russo273277_3-1" class="reference"><a href="#cite_note-russo273277-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> the exact value of the stadion remains a subject of debate to this day; see <a href="/wiki/Stadion_(unit)#Calculations" title="Stadion (unit)">stadion</a>). </p><p>Eratosthenes described his technique in a book entitled <i>On the measure of the Earth</i>, which has not been preserved; what has been preserved is the simplified version described by <a href="/wiki/Cleomedes" title="Cleomedes">Cleomedes</a> to popularise the discovery.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Cleomedes invites his reader to consider two Egyptian cities, <a href="/wiki/Alexandria" title="Alexandria">Alexandria</a> and Syene (modern <a href="/wiki/Aswan" title="Aswan">Aswan</a>): </p> <ol><li>Cleomedes assumes that the distance between Syene and Alexandria was 5,000 <a href="/wiki/Stadion_(unit)" title="Stadion (unit)">stadia</a> (a figure that was checked yearly by professional <a href="/wiki/Bematist" title="Bematist">bematists</a>, <i>mensores regii</i>).<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup></li> <li>He assumes the simplified (but inaccurate) hypothesis that Syene was precisely on the <a href="/wiki/Tropic_of_Cancer" title="Tropic of Cancer">Tropic of Cancer</a>, saying that at <a href="/wiki/Solar_noon" class="mw-redirect" title="Solar noon">local noon</a> on the summer <a href="/wiki/Solstice" title="Solstice">solstice</a> the Sun was directly overhead. Syene was actually north of the tropic by something less than a degree.</li> <li>He assumes the simplified (but inaccurate) hypothesis that Syene and Alexandria are on the same meridian. Syene was actually about 3 degrees of longitude east of Alexandria.</li></ol> <p>According to <a href="/wiki/Cleomedes" title="Cleomedes">Cleomedes</a>' <a href="/wiki/Cleomedes#On_the_Circular_Motions_of_the_Celestial_Bodies" title="Cleomedes"><i>On the Circular Motions of the Celestial Bodies</i></a>, around 240 BC, Eratosthenes calculated the <a href="/wiki/Earth_radius" title="Earth radius">circumference of the Earth</a> in <a href="/wiki/Ptolemaic_Kingdom" title="Ptolemaic Kingdom">Ptolemaic Egypt</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Using a vertical rod known as a <a href="/wiki/Gnomon" title="Gnomon">gnomon</a> and under the previous assumptions, he knew that at <a href="/wiki/Noon#Solar_noon" title="Noon">local noon</a> on the summer solstice in <a href="/wiki/Syene" class="mw-redirect" title="Syene">Syene</a> (modern <a href="/wiki/Aswan" title="Aswan">Aswan</a>, Egypt), the Sun was directly overhead, as the gnomon cast no shadow. Additionally, the shadow of someone looking down a deep well at that time in Syene blocked the reflection of the Sun on the water. Eratosthenes then measured the Sun's angle of elevation at noon in Alexandria by measuring the length of another gnomon's shadow on the ground.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Using the length of the rod, and the length of the shadow, as the legs of a triangle, he calculated the angle of the sun's rays.<sup id="cite_ref-:6_10-0" class="reference"><a href="#cite_note-:6-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> This angle was about 7°, or 1/50th the circumference of a <a href="/wiki/Circle" title="Circle">circle</a>; assuming the Earth to be perfectly spherical, he concluded that its circumference was 50 times the known distance from Alexandria to Syene (5,000 stadia, a figure that was checked yearly), i.e. 250,000 <a href="/wiki/Stadion_(unit)" title="Stadion (unit)">stadia</a>.<sup id="cite_ref-stade_11-0" class="reference"><a href="#cite_note-stade-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Depending on whether he used the "Olympic stade" (176.4 m) or the Italian stade (184.8 m), this would imply a circumference of 44,100 km (an error of 10%) or 46,100 km, an error of 15%.<sup id="cite_ref-stade_11-1" class="reference"><a href="#cite_note-stade-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> A value for the stadion of 157.7 metres has even been posited by L.V. Firsov, which would give an even better precision, but is plagued by calculation errors and false assumptions.<sup id="cite_ref-engels_12-0" class="reference"><a href="#cite_note-engels-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> In 2012, Anthony Abreu Mora repeated Eratosthenes's calculation with more accurate data; the result was 40,074 km, which is 66 km different (0.16%) from the currently accepted polar circumference.<sup id="cite_ref-:6_10-1" class="reference"><a href="#cite_note-:6-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Eratosthenes_measure_of_Earth_circumference.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Eratosthenes_measure_of_Earth_circumference.svg/310px-Eratosthenes_measure_of_Earth_circumference.svg.png" decoding="async" width="310" height="206" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Eratosthenes_measure_of_Earth_circumference.svg/465px-Eratosthenes_measure_of_Earth_circumference.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Eratosthenes_measure_of_Earth_circumference.svg/620px-Eratosthenes_measure_of_Earth_circumference.svg.png 2x" data-file-width="512" data-file-height="341" /></a><figcaption>Measure of Earth's circumference according to Cleomedes' simplified version, based on the approximation that <a href="/wiki/Aswan" title="Aswan">Syene</a> is on the <a href="/wiki/Tropic_of_Cancer" title="Tropic of Cancer">Tropic of Cancer</a> and on the same meridian as <a href="/wiki/Alexandria" title="Alexandria">Alexandria</a></figcaption></figure> <p>Eratosthenes' method was actually more complicated, as stated by the same Cleomedes, whose purpose was to present a simplified version of the one described in Eratosthenes' book. Pliny, for example, has quoted a value of 252,000 stadia.<sup id="cite_ref-Pliny_13-0" class="reference"><a href="#cite_note-Pliny-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>The method was based on several <a href="/wiki/Surveying" title="Surveying">surveying</a> trips conducted by professional <a href="/wiki/Bematist" title="Bematist">bematists</a>, whose job was to precisely measure the extent of the territory of Egypt for agricultural and taxation-related purposes.<sup id="cite_ref-russo273277_3-2" class="reference"><a href="#cite_note-russo273277-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Furthermore, the fact that Eratosthenes' measure corresponds precisely to 252,000 stadia (according to Pliny) might be intentional, since it is a number that can be divided by all natural numbers from 1 to 10: some historians believe that Eratosthenes changed from the 250,000 value written by Cleomedes to this new value to simplify calculations;<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> other historians of science, on the other side, believe that Eratosthenes introduced a new length unit based on the length of the meridian, as stated by Pliny, who writes about the stadion "according to Eratosthenes' ratio".<sup id="cite_ref-russo273277_3-3" class="reference"><a href="#cite_note-russo273277-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Pliny_13-1" class="reference"><a href="#cite_note-Pliny-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Posidonius">Posidonius</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=3" title="Edit section: Posidonius"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Posidonius#Earth's_circumference" title="Posidonius">Posidonius § Earth's circumference</a></div> <p><a href="/wiki/Posidonius" title="Posidonius">Posidonius</a> calculated the Earth's circumference by reference to the position of the star <a href="/wiki/Canopus_(star)" class="mw-redirect" title="Canopus (star)">Canopus</a>. As explained by <a href="/wiki/Cleomedes" title="Cleomedes">Cleomedes</a>, Posidonius observed Canopus on but never above the horizon at <a href="/wiki/Rhodes" title="Rhodes">Rhodes</a>, while at <a href="/wiki/Alexandria" title="Alexandria">Alexandria</a> he saw it ascend as far as <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac">7<span class="sr-only">+</span><span class="num">1</span>⁄<span class="den">2</span></span> degrees above the horizon (the <a href="/wiki/Meridian_arc" title="Meridian arc">meridian arc</a> between the latitude of the two locales is actually 5 degrees 14 minutes). Since he thought Rhodes was 5,000 <a href="/wiki/Stadion_(unit_of_length)" class="mw-redirect" title="Stadion (unit of length)">stadia</a> due north of Alexandria, and the difference in the star's elevation indicated the distance between the two locales was 1/48 of the circle, he multiplied 5,000 by 48 to arrive at a figure of 240,000 stadia for the circumference of the earth.<sup id="cite_ref-fragment_202_15-0" class="reference"><a href="#cite_note-fragment_202-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> It is generally thought<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Words_to_watch#Unsupported_attributions" title="Wikipedia:Manual of Style/Words to watch"><span title="The material near this tag may use weasel words or too-vague attribution. (April 2023)">by whom?</span></a></i>]</sup> that the stadion used by Posidonius was almost exactly 1/10 of a modern statute mile.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (April 2023)">citation needed</span></a></i>]</sup> Thus Posidonius's measure of 240,000 stadia translates to 24,000 mi (39,000 km), not much short of the actual circumference of 24,901 mi (40,074 km).<sup id="cite_ref-fragment_202_15-1" class="reference"><a href="#cite_note-fragment_202-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Strabo" title="Strabo">Strabo</a> noted that the distance between Rhodes and Alexandria is 3,750 stadia, and reported Posidonius's estimate of the Earth's circumference to be 180,000 stadia or 18,000 mi (29,000 km).<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Pliny_the_Elder" title="Pliny the Elder">Pliny the Elder</a> mentions Posidonius among his sources and—without naming him—reported his method for estimating the Earth's circumference. He noted, however, that <a href="/wiki/Hipparchus" title="Hipparchus">Hipparchus</a> had added some 26,000 stadia to Eratosthenes's estimate. The smaller value offered by Strabo and the different lengths of Greek and Roman stadia have created a persistent confusion around Posidonius's result. <a href="/wiki/Ptolemy" title="Ptolemy">Ptolemy</a> used Posidonius's lower value of 180,000 stades (about 33% too low) for the earth's circumference in his <a href="/wiki/Geography_(Ptolemy)" title="Geography (Ptolemy)"><i>Geography</i></a>. This was the number used by <a href="/wiki/Christopher_Columbus" title="Christopher Columbus">Christopher Columbus</a> in order to underestimate the distance to India as 70,000 stades.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Aryabhata">Aryabhata</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=4" title="Edit section: Aryabhata"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Around AD 525, the Indian mathematician and astronomer <a href="/wiki/Aryabhata" title="Aryabhata">Aryabhata</a> wrote <i><a href="/wiki/Aryabhatiya" title="Aryabhatiya">Aryabhatiya</a></i>, in which he calculated the diameter of earth to be of 1,050 <i><a href="/wiki/Yojanas" class="mw-redirect" title="Yojanas">yojanas</a></i>. The length of the <i>yojana</i> intended by Aryabhata is in dispute. One careful reading gives an equivalent of 14,200 kilometres (8,800 mi), too large by 11%.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> Another gives 15,360 km (9,540 mi), too large by 20%.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> Yet another gives 13,440 km (8,350 mi), too large by 5%.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Islamic_Golden_Age">Islamic Golden Age</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=5" title="Edit section: Islamic Golden Age"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Around AD 830, <a href="/wiki/Caliph" class="mw-redirect" title="Caliph">Caliph</a> <a href="/wiki/Al-Ma%27mun" title="Al-Ma'mun">Al-Ma'mun</a> commissioned a group of <a href="/wiki/Muslim_astronomers" class="mw-redirect" title="Muslim astronomers">Muslim astronomers</a> led by <a href="/wiki/Muhammad_ibn_Musa_al-Khwarizmi" class="mw-redirect" title="Muhammad ibn Musa al-Khwarizmi">Al-Khwarizmi</a> to measure the distance from Tadmur (<a href="/wiki/Palmyra" title="Palmyra">Palmyra</a>) to <a href="/wiki/Raqqa" title="Raqqa">Raqqa</a>, in modern <a href="/wiki/Syria" title="Syria">Syria</a>. They calculated the Earth's circumference to be within 15% of the modern value, and possibly much closer. How accurate it actually was is not known because of uncertainty in the conversion between the medieval Arabic units and modern units, but in any case, technical limitations of the methods and tools would not permit an accuracy better than about 5%.<sup id="cite_ref-HOC2_1_21-0" class="reference"><a href="#cite_note-HOC2_1-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Abu_Reyhan_Biruni-Earth_Circumference.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Abu_Reyhan_Biruni-Earth_Circumference.svg/220px-Abu_Reyhan_Biruni-Earth_Circumference.svg.png" decoding="async" width="220" height="198" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Abu_Reyhan_Biruni-Earth_Circumference.svg/330px-Abu_Reyhan_Biruni-Earth_Circumference.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Abu_Reyhan_Biruni-Earth_Circumference.svg/440px-Abu_Reyhan_Biruni-Earth_Circumference.svg.png 2x" data-file-width="1000" data-file-height="900" /></a><figcaption>Diagram showing how al-Biruni was able to calculate the Earth's circumference by measuring the dip of the horizon from a point at a known height.</figcaption></figure> <p>A more convenient way to estimate was provided in <a href="/wiki/Al-Biruni" title="Al-Biruni">Al-Biruni</a>'s <i>Codex Masudicus</i> (1037). In contrast to his predecessors, who measured the Earth's circumference by sighting the Sun simultaneously from two locations, <a href="/wiki/Al-Biruni" title="Al-Biruni">al-Biruni</a> developed a new method of using <a href="/wiki/Trigonometry" title="Trigonometry">trigonometric</a> calculations, based on the angle between a <a href="/wiki/Plain" title="Plain">plain</a> and <a href="/wiki/Mountain" title="Mountain">mountain</a> top, which made it possible for it to be measured by a single person from a single location.<sup id="cite_ref-HOC2_1_21-1" class="reference"><a href="#cite_note-HOC2_1-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> From the top of the mountain, he sighted the <a href="/wiki/Horizon#Zenith_angle" title="Horizon">dip angle</a> which, along with the mountain's height (which he determined beforehand), he applied to the <a href="/wiki/Law_of_sines" title="Law of sines">law of sines</a> formula. This was the earliest known use of dip angle and the earliest practical use of the law of sines.<sup id="cite_ref-Savizi_22-0" class="reference"><a href="#cite_note-Savizi-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> However, the method could not provide more accurate results than previous methods, due to technical limitations, and so al-Biruni accepted the value calculated the previous century by the <a href="/wiki/Al-Ma%27mun" title="Al-Ma'mun">al-Ma'mun</a> expedition.<sup id="cite_ref-HOC2_1_21-2" class="reference"><a href="#cite_note-HOC2_1-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Columbus's_error"><span id="Columbus.27s_error"></span>Columbus's error</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=6" title="Edit section: Columbus's error"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>1,700 years after Eratosthenes's death, <a href="/wiki/Christopher_Columbus" title="Christopher Columbus">Christopher Columbus</a> studied what Eratosthenes had written about the size of the Earth. Nevertheless, based on a map by <a href="/wiki/Toscanelli" class="mw-redirect" title="Toscanelli">Toscanelli</a>, he chose to believe that the Earth's circumference was 25% smaller. If, instead, Columbus had accepted Eratosthenes's larger value, he would have known that the place where he made landfall was not <a href="/wiki/Asia" title="Asia">Asia</a>, but rather a <a href="/wiki/New_World" title="New World">New World</a>.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Historical_use_in_the_definition_of_units_of_measurement">Historical use in the definition of units of measurement</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=7" title="Edit section: Historical use in the definition of units of measurement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/History_of_the_metre#Meridional_definition" title="History of the metre">History of the metre § Meridional definition</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Meridian_arc#History_of_measurement" title="Meridian arc">Meridian arc § History of measurement</a>, <a href="/wiki/Earth_radius#History" title="Earth radius">Earth radius § History</a>, and <a href="/wiki/Arc_measurement_of_Delambre_and_M%C3%A9chain" title="Arc measurement of Delambre and Méchain">Arc measurement of Delambre and Méchain</a></div> <p>In 1617 the Dutch scientist <a href="/wiki/Willebrord_Snellius" title="Willebrord Snellius">Willebrord Snellius</a> assessed the circumference of the Earth at 24,630 Roman miles (24,024 statute miles). Around that time British mathematician <a href="/wiki/Edmund_Gunter" title="Edmund Gunter">Edmund Gunter</a> improved navigational tools including a new <a href="/wiki/Quadrant_(instrument)" title="Quadrant (instrument)">quadrant</a> to determine latitude at sea. He reasoned that the lines of latitude could be used as the basis for a unit of measurement for <a href="/wiki/Distance" title="Distance">distance</a> and proposed the nautical mile as one minute or one-sixtieth (<style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">60</span></span>⁠</span>) of one <a href="/wiki/Degree_(angle)" title="Degree (angle)">degree</a> of latitude. As one degree is <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">360</span></span>⁠</span> of a circle, one minute of arc is <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">21600</span></span>⁠</span> of a circle – such that the polar circumference of the Earth would be exactly 21,600 miles. Gunter used Snellius's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>In 1793, France defined the metre so as to make the polar circumference of the Earth 40,000 kilometres. In order to measure this distance accurately, the <a href="/wiki/French_Academy_of_Sciences" title="French Academy of Sciences">French Academy of Sciences</a> commissioned <a href="/wiki/Jean_Baptiste_Joseph_Delambre" title="Jean Baptiste Joseph Delambre">Jean Baptiste Joseph Delambre</a> and <a href="/wiki/Pierre_M%C3%A9chain" title="Pierre Méchain">Pierre Méchain</a> to lead <a href="/wiki/Arc_measurement_of_Delambre_and_M%C3%A9chain" title="Arc measurement of Delambre and Méchain">an expedition</a> to attempt to accurately measure the distance between a belfry in <a href="/wiki/Dunkirk" title="Dunkirk">Dunkerque</a> and <a href="/wiki/Montju%C3%AFc_Castle_(Barcelona)" class="mw-redirect" title="Montjuïc Castle (Barcelona)">Montjuïc castle</a> in <a href="/wiki/Barcelona" title="Barcelona">Barcelona</a> to estimate the length of the <a href="/wiki/Meridian_arc" title="Meridian arc">meridian arc</a> through Dunkerque. The length of the first <a href="/wiki/Metre#International_prototype_metre_bar" title="Metre">prototype metre bar</a> was based on these measurements, but it was later determined that its length was short by about 0.2 millimetres because of miscalculation of the <a href="/wiki/Flattening" title="Flattening">flattening</a> of the Earth, making the prototype about 0.02% shorter than the original proposed definition of the metre. Regardless, this length became the French standard and was progressively adopted by other countries in Europe.<sup id="cite_ref-Alder2003_25-0" class="reference"><a href="#cite_note-Alder2003-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> This is why the polar circumference of the Earth is actually 40,008 kilometres, instead of 40,000. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=8" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Earth_radius" title="Earth radius">Earth radius</a></li> <li><a href="/wiki/Spherical_Earth" title="Spherical Earth">Spherical Earth</a></li> <li><a href="/wiki/Nautical_mile" title="Nautical mile">Nautical mile</a> <ul><li><a href="/wiki/Geographical_mile" title="Geographical mile">Geographical mile</a></li> <li><a href="/wiki/Arabic_mile" title="Arabic mile">Arabic mile</a></li></ul></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=9" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFHumerfelt2010" class="citation web cs1">Humerfelt, Sigurd (26 October 2010). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110424104419/http://home.online.no/~sigurdhu/WGS84_Eng.html">"How WGS 84 defines Earth"</a>. Archived from <a rel="nofollow" class="external text" href="http://home.online.no/~sigurdhu/WGS84_Eng.html">the original</a> on 24 April 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">29 April</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=How+WGS+84+defines+Earth&rft.date=2010-10-26&rft.aulast=Humerfelt&rft.aufirst=Sigurd&rft_id=http%3A%2F%2Fhome.online.no%2F~sigurdhu%2FWGS84_Eng.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRidpath2001" class="citation book cs1">Ridpath, Ian (2001). <i>The Illustrated Encyclopedia of the Universe</i>. New York, NY: Watson-Guptill. p. 31. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-8230-2512-1" title="Special:BookSources/978-0-8230-2512-1"><bdi>978-0-8230-2512-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Illustrated+Encyclopedia+of+the+Universe&rft.place=New+York%2C+NY&rft.pages=31&rft.pub=Watson-Guptill&rft.date=2001&rft.isbn=978-0-8230-2512-1&rft.aulast=Ridpath&rft.aufirst=Ian&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-russo273277-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-russo273277_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-russo273277_3-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-russo273277_3-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-russo273277_3-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRusso2004" class="citation book cs1"><a href="/wiki/Lucio_Russo" title="Lucio Russo">Russo, Lucio</a> (2004). <span class="id-lock-limited" title="Free access subject to limited trial, subscription normally required"><a rel="nofollow" class="external text" href="https://archive.org/details/forgottenrevolut00russ_217"><i>The Forgotten Revolution</i></a></span>. Berlin: Springer. p. <a rel="nofollow" class="external text" href="https://archive.org/details/forgottenrevolut00russ_217/page/n277">273</a>–277.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Forgotten+Revolution&rft.place=Berlin&rft.pages=273-277&rft.pub=Springer&rft.date=2004&rft.aulast=Russo&rft.aufirst=Lucio&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fforgottenrevolut00russ_217&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged November 2023">dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup></span> </li> <li id="cite_note-ShekharXiong2007-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-ShekharXiong2007_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFShashi_ShekharHui_Xiong2007" class="citation book cs1">Shashi Shekhar; Hui Xiong (12 December 2007). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=6q2lOfLnwkAC&pg=PA638"><i>Encyclopedia of GIS</i></a>. Springer Science & Business Media. pp. 638–640. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-387-30858-6" title="Special:BookSources/978-0-387-30858-6"><bdi>978-0-387-30858-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Encyclopedia+of+GIS&rft.pages=638-640&rft.pub=Springer+Science+%26+Business+Media&rft.date=2007-12-12&rft.isbn=978-0-387-30858-6&rft.au=Shashi+Shekhar&rft.au=Hui+Xiong&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D6q2lOfLnwkAC%26pg%3DPA638&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRusso" class="citation book cs1">Russo, Lucio. <i>The Forgotten Revolution</i>. p. 68.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Forgotten+Revolution&rft.pages=68&rft.aulast=Russo&rft.aufirst=Lucio&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text">Cleomedes, <i>Caelestia</i>, i.7.49–52.</span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">Martianus Capella, <i>De nuptiis Philologiae et Mercurii</i>, VI.598.</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVan_Helden1985" class="citation book cs1">Van Helden, Albert (1985). <i>Measuring the Universe: Cosmic Dimensions from Aristarchus to Halley</i>. University of Chicago Press. pp. 4–5. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-226-84882-2" title="Special:BookSources/978-0-226-84882-2"><bdi>978-0-226-84882-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Measuring+the+Universe%3A+Cosmic+Dimensions+from+Aristarchus+to+Halley&rft.pages=4-5&rft.pub=University+of+Chicago+Press&rft.date=1985&rft.isbn=978-0-226-84882-2&rft.aulast=Van+Helden&rft.aufirst=Albert&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.eg.bucknell.edu/physics/astronomy/astr101/specials/eratosthenes.html">"Astronomy 101 Specials: Eratosthenes and the Size of the Earth"</a>. <i>www.eg.bucknell.edu</i><span class="reference-accessdate">. Retrieved <span class="nowrap">19 December</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.eg.bucknell.edu&rft.atitle=Astronomy+101+Specials%3A+Eratosthenes+and+the+Size+of+the+Earth&rft_id=https%3A%2F%2Fwww.eg.bucknell.edu%2Fphysics%2Fastronomy%2Fastr101%2Fspecials%2Feratosthenes.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-:6-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-:6_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:6_10-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://anthonybloggeneral.wordpress.com/2012/07/03/eratosthenes-earth-circumference/">"How did Eratosthenes measure the circumference of the earth?"</a>. 3 July 2012.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=How+did+Eratosthenes+measure+the+circumference+of+the+earth%3F&rft.date=2012-07-03&rft_id=https%3A%2F%2Fanthonybloggeneral.wordpress.com%2F2012%2F07%2F03%2Feratosthenes-earth-circumference%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-stade-11"><span class="mw-cite-backlink">^ <a href="#cite_ref-stade_11-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-stade_11-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.maa.org/publications/periodicals/convergence/eratosthenes-and-the-mystery-of-the-stades-how-long-is-a-stade">"Eratosthenes and the Mystery of the Stades – How Long Is a Stade? – Mathematical Association of America"</a>. <i>www.maa.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.maa.org&rft.atitle=Eratosthenes+and+the+Mystery+of+the+Stades+%E2%80%93+How+Long+Is+a+Stade%3F+%E2%80%93+Mathematical+Association+of+America&rft_id=http%3A%2F%2Fwww.maa.org%2Fpublications%2Fperiodicals%2Fconvergence%2Feratosthenes-and-the-mystery-of-the-stades-how-long-is-a-stade&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-engels-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-engels_12-0">^</a></b></span> <span class="reference-text">Donald Engels (1985). <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/295030">The Length of Eratosthenes' Stade</a>. <i>American Journal of Philology</i> <b>106</b> (3): 298–311. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.2307%2F295030">10.2307/295030</a> <span style="font-size:0.95em; font-size:95%; color: var( --color-subtle, #555 )">(subscription required)</span>.</span> </li> <li id="cite_note-Pliny-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-Pliny_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Pliny_13-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Pliny, <i>Naturalis Historia</i>, Book 2, Chapter 112.</span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRawlins1983" class="citation journal cs1">Rawlins, Dennis (1983). <a rel="nofollow" class="external text" href="https://link.springer.com/article/10.1007/BF00348500">"The Eratosthenes-Strabo Nile Map. Is It the Earliest Surviving Instance of Spherical Cartography? Did It Supply the 5000 Stades Arc for Eratosthenes' Experiment?"</a>. <i>Archive for History of Exact Sciences</i>. <b>26</b> (3): 211–219. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2FBF00348500">10.1007/BF00348500</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118004246">118004246</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Archive+for+History+of+Exact+Sciences&rft.atitle=The+Eratosthenes-Strabo+Nile+Map.+Is+It+the+Earliest+Surviving+Instance+of+Spherical+Cartography%3F+Did+It+Supply+the+5000+Stades+Arc+for+Eratosthenes%27+Experiment%3F&rft.volume=26&rft.issue=3&rft.pages=211-219&rft.date=1983&rft_id=info%3Adoi%2F10.1007%2FBF00348500&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118004246%23id-name%3DS2CID&rft.aulast=Rawlins&rft.aufirst=Dennis&rft_id=https%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2FBF00348500&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-fragment_202-15"><span class="mw-cite-backlink">^ <a href="#cite_ref-fragment_202_15-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-fragment_202_15-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Posidonius, <a rel="nofollow" class="external text" href="http://www.attalus.org/translate/poseidonius.html#202.K">fragment 202</a></span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text">Cleomedes (<a rel="nofollow" class="external text" href="http://adsabs.harvard.edu/abs/1975QJRAS..16..152F">in Fragment 202</a>) stated that if the distance is measured by some other number the result will be different, and using 3,750 instead of 5,000 produces this estimation: 3,750 x 48 = 180,000; see Fischer I., (1975), <i>Another Look at Eratosthenes' and Posidonius' Determinations of the Earth's Circumference</i>, Ql. J. of the Royal Astron. Soc., Vol. 16, p.152.</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><a href="/wiki/John_Freely" title="John Freely">John Freely</a>, <a rel="nofollow" class="external text" href="https://books.google.com/books?id=MfhjAAAAQBAJ"><i>Before Galileo: The Birth of Modern Science in Medieval Europe</i></a> (2012)</span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKak2010" class="citation arxiv cs1">Kak, Subhash (2010). "Aryabhata's Mathematics". <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1002.3409">1002.3409</a></span> [<a rel="nofollow" class="external text" href="https://arxiv.org/archive/cs.CR">cs.CR</a>].</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=preprint&rft.jtitle=arXiv&rft.atitle=Aryabhata%27s+Mathematics&rft.date=2010&rft_id=info%3Aarxiv%2F1002.3409&rft.aulast=Kak&rft.aufirst=Subhash&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=rtroKSuAQU4C&q=Aryabhata+yojana&pg=RA1-PA655">"Journal of the Royal Asiatic Society of Great Britain and Ireland"</a>. 1907.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Journal+of+the+Royal+Asiatic+Society+of+Great+Britain+and+Ireland&rft.date=1907&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DrtroKSuAQU4C%26q%3DAryabhata%2Byojana%26pg%3DRA1-PA655&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://archive.org/stream/The_Aryabhatiya_of_Aryabhata_Clark_1930#page/n19/mode/2up">"The_Aryabhatiya_of_Aryabhata_Clark_1930"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The_Aryabhatiya_of_Aryabhata_Clark_1930&rft_id=https%3A%2F%2Farchive.org%2Fstream%2FThe_Aryabhatiya_of_Aryabhata_Clark_1930%23page%2Fn19%2Fmode%2F2up&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-HOC2_1-21"><span class="mw-cite-backlink">^ <a href="#cite_ref-HOC2_1_21-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-HOC2_1_21-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-HOC2_1_21-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMercier1992" class="citation encyclopaedia cs1">Mercier, Raymond (1992). "Geodesy". In Harley, J.B.; Woodward, David (eds.). <i>The History of Cartography, Volume 2, Book 1</i>. The University of Chicago Press. pp. 175–188. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780226316352" title="Special:BookSources/9780226316352"><bdi>9780226316352</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Geodesy&rft.btitle=The+History+of+Cartography%2C+Volume+2%2C+Book+1&rft.pages=175-188&rft.pub=The+University+of+Chicago+Press&rft.date=1992&rft.isbn=9780226316352&rft.aulast=Mercier&rft.aufirst=Raymond&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-Savizi-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-Savizi_22-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBehnaz_Savizi2007" class="citation cs2">Behnaz Savizi (2007), "Applicable Problems in History of Mathematics: Practical Examples for the Classroom", <i>Teaching Mathematics and Its Applications</i>, <b>26</b> (1), <a href="/wiki/Oxford_University_Press" title="Oxford University Press">Oxford University Press</a>: 45–50, <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1093%2Fteamat%2Fhrl009">10.1093/teamat/hrl009</a></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Teaching+Mathematics+and+Its+Applications&rft.atitle=Applicable+Problems+in+History+of+Mathematics%3A+Practical+Examples+for+the+Classroom&rft.volume=26&rft.issue=1&rft.pages=45-50&rft.date=2007&rft_id=info%3Adoi%2F10.1093%2Fteamat%2Fhrl009&rft.au=Behnaz+Savizi&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text">Gow, Mary. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=hWv-WUOHfSIC&pg=PA6&vq=Columbus&dq=Measuring+the+Earth:+Eratosthenes+and+His+Celestial+Geometry.&output=html_text&source=gbs_search_r&cad=1"><i>Measuring the Earth: Eratosthenes and His Celestial Geometry</i></a>, p. 6 (Berkeley Heights, NJ: Enslow, 2010).</span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text">Marine Insight, <a rel="nofollow" class="external text" href="https://www.marineinsight.com/guidelines/nautical-mile-knot-units-used-sea/">Why Nautical Mile and Knot Are The Units Used at Sea?</a></span> </li> <li id="cite_note-Alder2003-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-Alder2003_25-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAlder2003" class="citation book cs1">Alder, Ken (October 2003). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=jwsDERPMPhsC"><i>The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World</i></a>. Simon and Schuster. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7432-1676-0" title="Special:BookSources/978-0-7432-1676-0"><bdi>978-0-7432-1676-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Measure+of+All+Things%3A+The+Seven-Year+Odyssey+and+Hidden+Error+That+Transformed+the+World&rft.pub=Simon+and+Schuster&rft.date=2003-10&rft.isbn=978-0-7432-1676-0&rft.aulast=Alder&rft.aufirst=Ken&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DjwsDERPMPhsC&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Bibliography">Bibliography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=10" title="Edit section: Bibliography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Earth%27s_circumference" class="extiw" title="commons:Category:Earth's circumference">Earth's circumference</a></span>.</div></div> </div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKrebsKrebs2003" class="citation book cs1">Krebs, Robert E.; Krebs, Carolyn A. (2003). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=0H0fjBeseVEC&pg=PA52">"Calculating the Earth's Circumference"</a>. <i>Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World</i>. Greenwood Publishing Group. p. 52. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-313-31342-4" title="Special:BookSources/978-0-313-31342-4"><bdi>978-0-313-31342-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Calculating+the+Earth%27s+Circumference&rft.btitle=Groundbreaking+Scientific+Experiments%2C+Inventions%2C+and+Discoveries+of+the+Ancient+World&rft.pages=52&rft.pub=Greenwood+Publishing+Group&rft.date=2003&rft.isbn=978-0-313-31342-4&rft.aulast=Krebs&rft.aufirst=Robert+E.&rft.au=Krebs%2C+Carolyn+A.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D0H0fjBeseVEC%26pg%3DPA52&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFNicastro2008" class="citation book cs1">Nicastro, Nicholas (25 November 2008). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/isbn_9780312372477"><i>Circumference: Eratosthenes and the Ancient Quest to Measure the Globe</i></a></span>. St. Martin's Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-4299-5819-6" title="Special:BookSources/978-1-4299-5819-6"><bdi>978-1-4299-5819-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Circumference%3A+Eratosthenes+and+the+Ancient+Quest+to+Measure+the+Globe&rft.pub=St.+Martin%27s+Press&rft.date=2008-11-25&rft.isbn=978-1-4299-5819-6&rft.aulast=Nicastro&rft.aufirst=Nicholas&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fisbn_9780312372477&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGow2009" class="citation book cs1">Gow, Mary (1 July 2009). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=hWv-WUOHfSIC"><i>Measuring the Earth: Eratosthenes and His Celestial Geometry</i></a>. Enslow Publishing, LLC. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7660-3120-3" title="Special:BookSources/978-0-7660-3120-3"><bdi>978-0-7660-3120-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Measuring+the+Earth%3A+Eratosthenes+and+His+Celestial+Geometry&rft.pub=Enslow+Publishing%2C+LLC&rft.date=2009-07-01&rft.isbn=978-0-7660-3120-3&rft.aulast=Gow&rft.aufirst=Mary&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DhWv-WUOHfSIC&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLowrie2007" class="citation book cs1">Lowrie, William (20 September 2007). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=h2-NjUg4RtEC&pg=PA43"><i>Fundamentals of Geophysics</i></a>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-139-46595-3" title="Special:BookSources/978-1-139-46595-3"><bdi>978-1-139-46595-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Fundamentals+of+Geophysics&rft.pub=Cambridge+University+Press&rft.date=2007-09-20&rft.isbn=978-1-139-46595-3&rft.aulast=Lowrie&rft.aufirst=William&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dh2-NjUg4RtEC%26pg%3DPA43&rfr_id=info%3Asid%2Fen.wikipedia.org%3AEarth%27s+circumference" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Earth%27s_circumference&action=edit&section=11" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=8hZl3arO7SY">Carl Sagan demonstrates how Eratosthenes determined that the Earth was round and the approximate circumference</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Earth%27s_circumference&oldid=1247520443">https://en.wikipedia.org/w/index.php?title=Earth%27s_circumference&oldid=1247520443</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Earth" title="Category:Earth">Earth</a></li><li><a href="/wiki/Category:Units_of_length" title="Category:Units of length">Units of length</a></li><li><a href="/wiki/Category:Geodesy" title="Category:Geodesy">Geodesy</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:All_articles_with_dead_external_links" title="Category:All articles with dead external links">All articles with dead external links</a></li><li><a href="/wiki/Category:Articles_with_dead_external_links_from_November_2023" title="Category:Articles with dead external links from November 2023">Articles with dead external links from November 2023</a></li><li><a href="/wiki/Category:Pages_containing_links_to_subscription-only_content" title="Category:Pages containing links to subscription-only content">Pages containing links to subscription-only content</a></li><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li><li><a href="/wiki/Category:Use_dmy_dates_from_November_2019" title="Category:Use dmy dates from November 2019">Use dmy dates from November 2019</a></li><li><a href="/wiki/Category:Use_British_English_from_February_2023" title="Category:Use British English from February 2023">Use British English from February 2023</a></li><li><a href="/wiki/Category:Articles_with_specifically_marked_weasel-worded_phrases_from_April_2023" title="Category:Articles with specifically marked weasel-worded phrases from April 2023">Articles with specifically marked weasel-worded phrases from April 2023</a></li><li><a href="/wiki/Category:All_articles_with_unsourced_statements" title="Category:All articles with unsourced statements">All articles with unsourced statements</a></li><li><a href="/wiki/Category:Articles_with_unsourced_statements_from_April_2023" title="Category:Articles with unsourced statements from April 2023">Articles with unsourced statements from April 2023</a></li><li><a href="/wiki/Category:Commons_category_link_is_on_Wikidata" title="Category:Commons category link is on Wikidata">Commons category link is on Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 24 September 2024, at 17:23<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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