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1、ORIGINSOFEARTHOurplanetisoneofnineplanetscirclingtheSun.OurwholeMANTLEsolarsystemisjustoneofmanymillionsinavastuniverse.ThissectioncontainsWastherelifeonEarthfromthebeginningmoreironthanthecrustandislikemeltedplastictheneareritgetstotheDefinitelynot!Atfirst,Earth’ssurfacewasfarto
2、ohottosupportanyformofcore.life.Gradually,however,itcooleddownsothatathincrustformedroundtheHowoldisEarthoutside.Itremainedboilinghotinside—andisstillthesametoday!OUTERCOREThisisanincrediblyEarthwasformedaroundhot6,692°F(3,700°C).WhendidlifeonEarthstart4.7billionyearsagoThis,plus
3、theinnercore,islargerthanTheoldestmicrofossilfoundsofarDinosaursarrivedaroundtheplanetMars!is3,500millionyearsold.Life250millionyearsagobeganabout1,000millionINNERCOREHumansarrivedaroundThissectionisasolidyearsafterEarthwas11,000yearsagoballcomposedmainlyofformed.Scientiststendto
4、iron.Itisthehottestpart,datetheageofrockstoImagine“time”asrepresentedbythedistanceat7,772°F(4,300°C)!giveuscluestoEarth’sbetweenyouroutstretchedarms.Theuniverseage,workingonawasformedonyourlongestleft-handfinger.“calendar”thatspansOne-celllifeformsbeganbetweenyourwristmillionsofy
5、ears.EarlylifeonEarth.andyourelbow.Dinosaursdidnotappearuntilyoureachyourrighthand.Humansarrivedonthefingernailofyourlongestright-handfinger!WhatdoesEarthlooklikeORIGINSOFEARItwasNeilArmstrong,thefirstmantowalkontheMooninJuly1969,whosaidEarthlookedlike“asplendidjewelsuspendedinsp
6、ace.”HowwasEarthformedThatiswhatitlookedliketohimfromhisApollospaceship.Seenfromspace,theThelatesttheoryisthatEarthformedfromagiganticcloudofspinninggasbeautifulappearanceofEarthiscausedbyanddust.Here’swhatisthoughttohavehappened.sunlightreflectingofftheoceans.Thisgivestheplaneti
7、tsspecialsparklingblueFACTBYTESappearance.WreathsofcloudThedistanceroundTHEarthfromtoptoappearasbottomandroundswirlingwhiteTHECRUSTthemiddleisalmostAfloatingcloudGasesformedTheremainingTheplanetsThissectionisthickestthesame—40,000masses,whileattheHimalayaskilometers(24,860ofgasan
8、ddustinsidethedustcontinuedcollidedandla
