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1、GeodesyandtheSizeandShapeofthePlanetEarthMeasuringtheSizeandShapeofEarthEarth,withaveragedistanceof92,955,820miles(149,597,890km)fromthesun,isthethirdplanetandoneofthemostuniqueplanetsinthesolarsystem.Itformedaround4.5-4.6billionyearsagoandistheonlyplanetknowntosustainlife.Thisisbecausefactorslikei
2、tsatmosphericcompositionandphysicalpropertiessuchasthepresenceofwaterover70.8%oftheplanetallowlifetothrive.Earthisalsouniquehoweverbecauseitisthelargestoftheterrestrialplanets(onethatiscomposedofathinlayerofrocksasopposedtothosethataremostlymadeupofgaseslikeJupiterorSaturn)basedonitsmass,density,an
3、ddiameter.Earthisalsothefifthlargestplanetintheentiresolarsystem.Earth'sSizeAsthelargestoftheterrestrialplanets,Earthhasanestimatedmassof5.9736x1024kg.Itsvolumeisalsothelargestoftheseplanetsat108.321x1010km3.Inaddition,Earthisthedensestoftheterrestrialplanetsasitismadeupofacrust,mantleandcore・TheEa
4、rth'scrustisthethirrnestoftheselayerswhilethemantlecomprises84%ofEarth'svolumeandextends1,800miles(2,900km)belowthesurface.WhatmakesEarththedensestoftheseplanetshoweverisitscore.Itistheonlyterrestrialplanetwithaliquidoutercorethatsurroundsasolid,denseinnercore.Earth'saveragedensityis5515x10kg/m3.Ma
5、rs,thesmallestoftheterrestrialplanetsbydensity,isonlyaround70%asdenseasEarth.Earthisclassifiedasthelargestoftheterrestrialplanetsbasedonitscircumfereneeanddiameteraswell.Attheequator,Earth'scircumfereneeis24,901.55miles(40,075.16km).ItisslightlysmallerbetweentheNorthandSouthpolesat24,859.82miles(40
6、,008km).Earth'sdiameteratthepolesis7,899.80miles(12,713.5km)whileitis7,926.28miles(12,756.1km)attheequator.Forcomparison,thelargestplanetinEarth'ssolarsystem,Jupiter;hasadiameterof88,846miles(142,984km).Earth'sShapeEarth'scircumfereneeanddiameterdifferbecauseitsshapeisclassifiedasanoblatespheroidor
7、ellipsoid,insteadofatruesphere.Thismeansthatinsteadofbeingofequalcircumfereneeinallareas,thepolesaresquished,resultinginabulgeattheequator,andthusalargercircumferenceanddiameterthere.TheequatorialbulgeatEar
