2024剑桥雅思讲义TRUE_FALSE_NOT_GIVEN 1.docx
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1、True/False/NotGivenPaSSage1TheLayersoftheSunConsidertheearth,themoon,andalltheotherplanetsinoursolarsystem.Thinkaboutthemassthatallthoseobjectsmusthavewhentheyarealladdedtogether.Counter-intuitively,addedalltogethertheyaccountforonly0.2%ofthetotalmassofthesolarsystem.Thesunmakesuptheremaining99.8%of
2、allthemassinthesolarsystem!Thesunisthecenterofthesolarsystemandthelargestobjectinthesolarsystem.OursunisastarthatprovideslightandheatandsupportsalmostalllifeonEarth.Thesunisasphere,butunliketheearthandthemoon,itisnotsolid.Mostatomsinthesunexistasplasma,orafourthstateofmattermadeupOfsuperheatedgaswit
3、hanelectricalcharge.Oursunconsistsalmostentirelyoftheelementshydrogenandhelium,andbecausethesunisnotsolidzitdoesnothaveadefinedouterboundary.Itdoes,howevehaveadefiniteinternalstructure.Thereareseveralidentifiablelayersofthesun:Thecoreistheinnermostorcentrallayerofthesun.Thecoreisplasma,butmovessimil
4、arlytoagas.Itstemperatureisaround27milliondegreesCelsius.Inthecore,nuclearreactionscombinehydrogenatomstoformhelium,releasingvastamountsofenergyintheprocess.Theenergyreleasedthenbeginstomoveoutward,towardstheouterlayersofthesun.Justoutsidethecoreistheradiativezone,whichhasatemperatureofabout7million
5、degreesCelsius.Theenergyreleasedinthecoretravelsextremelyslowlythroughtheradiativezone.Particlesoflightcalledphotonscanonlytravelafewmillimetersbeforetheyhitanotherparticleinthesun,areabsorbedandthenreleasedagain.Itcantakeaphotonaslongas50millionyearstotravelallthewaythroughtheradiativezone.Surround
6、ingtheradiativezoneistheconvectionzone.Here,hotmaterialfromnearthesunscenterrises,coolsatthesurface,andthenplungesbackdownwardtoreceivemoreheatfromtheradiativezone.Thismovementhelpstocreatesolarflaresandsunspots.Thesefirstthreelayersmakeupwhatwewouldactuallycallthesun.Thenextthreelayersmakeupthesuns
7、atmosphere.Ofcourse,therearenosolidlayerstoanypartofthesunzsotheseboundariesarefuzzyandindistinct.Thevisiblesurfaceofthesunisknownasthephotosphere.Thisistheregionofthesunthatemitssunlight.Itsalsooneofthecoolestlayersofthesunonlyabout6700oC.Lookingataphotographofthesunssurface,youcanseethatithassever
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