下面小编跟大家一起了解托福听写阅读理解分享，希望对大家的学习有所帮助。

NARRATOR:Listentopartofalectureinanastronomyclass.

MALEPROFESSOR:Saturn’sringshavealwaysbaffledastronomers.Untilabout30yearsago,wethoughttheringswerecomposedofparticlesoficeandrockthatwereleftoverfromSaturn’sformation—extramaterialthatnevermanagedtoform,uh,coalesceintoamoon.Asyouknow,it’sbelievedthatSaturn,andalltheplanetsinoursolarsystemcoalescedfromaswirlingcloudofgassome4.8billionyearsago.However,iftheringsaremadeofleftoversfromthatprocess,thenthey’dalsobeabout4.8billionyearsold.Theproblemisthatanythinggatheringspacedustforthatlongwouldcertainlyhavedarkenedbynow.ButSaturn’srings—mostofthem,anyway—arepristine...sobrightandshinythattheymakeSaturnthejewelofthesolarsystem.

Sothehypothesisthattheringsarejustmadeofmaterialleftoverfromthetimeofplanetaryformation—thathypothesismustbewrong.Saturn’sringsaremuchyoungerthantheplanetitself.Theymayhaveformedonlyafewhundredmillionyearsago—aroundthetimetheearliestdinosaurslivedonEarth.Werealizenowthattheringparticles,which,uh,rangeinsizefrommicroscopicdusttobouldersbiggerthanlargehouses.Well,alotoftheseparticlesareeventuallylost.Webelievetheygraduallyspiraldownoutoftheringsandintotheplanet’satmosphere.Thisoccursasaresultoftheplanet’sgravity,andalsobecauseoftheeffectsofitsmagneticfield...Now,ifmaterialfromSaturn’sringsisbeinglostandnothingnewisaddedfromtimetotime,theringswouldbedisappearing.

Butthat’snothappening!Sosomehow,theremustbenewmaterialfeedingtheringsystem.Questionis:Where’sthisnewmaterialcomingfrom?Sowe’rebacktosquareone.But,insteadofasking,Howdidtheringsform?"Weshouldbeasking…uh,anyone?Beth?

FEMALESTUDENT:Howdotheringsform?MALEPROFESSOR:Howdotheringsform!Becausethey’reapparentlyreplenishingthemselvessomehow.

Uh,OK,here’sonepossibility—themoons,thedozensofmoonsthatorbitSaturnareprovidingrawmaterialfortherings.AmooninasystemascomplexasSaturn’s—andSaturnhasatleast49knownmoons,whichvarytremendouslyinsizeandshape.Um,amooninsuchacomplexsystemisnotonlyaffectedbythegravitationalforceoftheplanet,butalsobythatoftheothermoons.

FEMALESTUDENT:Sotheplanetmaybepullingamoononeway,andothermoonsmaybepullingit...otherways?MALEPROFESSOR:Exactly.Suchforcescouldactuallyalteramoon’sorbit,andasaresult,theremightbeacollision—onemoonmightcrashintoanother—andthedebrisfromthatcollisioncouldbecomepartoftherings.Thentherearetidalforces.AmoonmightgettooclosetotheplanetandgetbrokenapartbySaturn’stidalforces.

FEMALESTUDENT:Excuseme.Youmean,tidalforces,likehightideandlowtideontheoceans?MALEPROFESSOR:Well,bytidalforce,"I’mreferringtothegravitationalpullofSaturnonitsmoons.Um,inthemid-1800s,aFrenchscientistnamedédouardRochewasstudyingtheeffectsofaplanet’stidalforcesonitsmoons.

Rochewasabletoshowmathematicallythatifonecelestialbody—say,amoon—uh,ifitpassestooclosetoanother—say,aplanet—thathasagravitationalforcestrongerthantheforceofself-attractionthatholdsthemoontogether,well,thatfirstbody,thatmoon,it’dberippedapart.WecallthedistanceatwhichthishappenstheRochelimit."SoifoneofSaturn’smoonsreachestheRochelimitoftheplanetorevenalargermoon,itwoulddisintegrate—betornapart,andthusaddmorematerialtotheringsystem.

Andthere’sanotherwaynewmaterialmightbeaddedtoSaturn’srings—anasteroidcrashingintooneofthemoons.Thishypothesisissupportedbythefactthatsomeofthemanyringsareabitreddishincolor.Uh,yes,George?

MALESTUDENT:I’msorry.Idon’tfollowthelogic.MALEPROFESSOR:Well,thisreddishcolorationsuggeststhepresenceofcomplexorganicmolecules—uh,carbon-basedmolecules—mixedinwiththewater-ice.Remember,therestofSaturn’sringsaremadealmostentirelyofwater-ice.AndnoneofSaturn’smoonsisred.Butasteroidscouldbe...andthuscouldendupcontributingtotheringsystemthekindofcarbon-basedmoleculeswe’retalkingabout.