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2012年雅思考试阅读模拟试题(含答案)1There'sadimmer
\o"switch��ʲô��˼"switch
insidethesunthatcausesitsbrightnesstoriseandfallontimescalesofaround100,000years—exactlythesameperiodasbetweeniceagesonEarth.Sosaysaphysicistwhohascreatedacomputermodelofourstar's
\o"core��ʲô��˼"core.2RobertEhrlichofGeorge
\o"Mason��ʲô��˼"Mason
UniversityinFairfax,Virginia,modelledtheeffectof
\o"temperature��ʲô��˼"temperaturefluctuationsinthesun'sinterior.Accordingtothestandardview,thetemperatureofthesun's
\o"core��ʲô��˼"core
isheld
\o"constant��ʲô��˼"constant
bythe
\o"opposing��ʲô��˼"opposing
pressuresof
\o"gravity��ʲô��˼"gravityandnuclear
\o"fusion��ʲô��˼"fusion.However,Ehrlichbelievedthat
\o"slight��ʲô��˼"slight
variationsshouldbepossible.3HetookashisstartingpointtheworkofAttilaGrandpierreoftheKonkoly
\o"Observatory��ʲô��˼"Observatory
oftheHungarian
\o"Academy��ʲô��˼"Academy
ofSciences.In2005,Grandpierreanda
\o"collaborator��ʲô��˼"collaborator,Gáborágoston,\o"calculated��ʲô��˼"calculated
that
\o"magnetic��ʲô��˼"magnetic
fieldsinthesun's
\o"core��ʲô��˼"core
could
\o"produce��ʲô��˼"produce
smallinstabilitiesinthesolarplasma.Theseinstabilitieswould
\o"induce��ʲô��˼"induce
localisedoscillationsin
\o"temperature��ʲô��˼"temperature.4Ehrlich'smodelshowsthatwhilstmostoftheseoscillationscanceleachotherout,some\o"reinforce��ʲô��˼"reinforce
oneanotherandbecomelong-lived
\o"temperature��ʲô��˼"temperature
variations.Thefavouredfrequenciesallowthesun's
\o"core��ʲô��˼"core
\o"temperature��ʲô��˼"temperature
to
\o"oscillate��ʲô��˼"oscillate
arounditsaveragetemperatureof13.6millionkelvinincycles
\o"lasting��ʲô��˼"lasting
either100,000or41,000years.Ehrlichsaysthat
\o"random��ʲô��˼"random
interactionswithinthesun's
\o"magnetic��ʲô��˼"magnetic
fieldcould
\o"flip��ʲô��˼"flip
thefluctuationsfromonecyclelengthtotheother.5ThesetwotimescalesareinstantlyrecognisabletoanyonefamiliarwithEarth'siceages:forthepastmillionyears,iceageshaveoccurredroughlyevery100,000years.Beforethat,theyoccurredroughlyevery41,000years.6Mostscientistsbelievethattheiceagesaretheresultof
\o"subtle��ʲô��˼"subtle
changesinEarth'sorbit,knownastheMilankovitchcycles.OnesuchcycledescribesthewayEarth'sorbitgraduallychangesshapefroma
\o"circle��ʲô��˼"circle
toa
\o"slight��ʲô��˼"slight
\o"ellipse��ʲô��˼"ellipse
andbackagainroughlyevery100,000years.Thetheorysaysthisalterstheamountofsolar
\o"radiation��ʲô��˼"radiation
thatEarthreceives,triggeringtheiceages.However,a
\o"persistent��ʲô��˼"persistent
problemwiththistheoryhasbeenits
\o"inability��ʲô��˼"inability
toexplainwhytheiceageschanged
\o"frequency��ʲô��˼"frequency
amillionyearsago.7"InMilankovitch,thereiscertainlynogoodideawhythe
\o"frequency��ʲô��˼"frequency
shouldchangefromonetoanother,"saysNeilEdwards,aclimatologistattheOpenUniversityinMiltonKeynes,UK.Noristhe
\o"transition��ʲô��˼"transition
problemtheonlyonetheMilankovitchtheoryfaces.Ehrlichandothercritics\o"claim��ʲô��˼"claim
thatthe
\o"temperature��ʲô��˼"temperature
variationscausedbyMilankovitchcyclesaresimplynotbigenoughtodriveiceages.8However,EdwardsbelievesthesmallchangesinsolarheatingproducedbyMilankovitchcyclesarethen
\o"amplified��ʲô��˼"amplified
byfeedbackmechanismsonEarth.Forexample,ifseaicebeginstoformbecauseofa
\o"slight��ʲô��˼"slight
cooling,carbondioxidethatwouldotherwisehavefounditswayintotheatmosphereaspartofthecarboncycleislockedintotheice.Thatweakensthe
\o"greenhouse��ʲô��˼"greenhouseeffectandEarthgrowsevencolder.9AccordingtoEdwards,thereisnolackofsuchmechanisms."Ifyouaddtheireffectstogether,thereismorethanenoughfeedbacktomakeMilankovitchwork,"hesays."Theproblemnowisidentifyingwhichmechanismsareatwork."ThisiswhyscientistslikeEdwardsarenotyetreadytogiveuponthe
\o"current��ʲô��˼"current
theory."Milankovitchcyclesgiveusiceagesroughlywhenwe
\o"observe��ʲô��˼"observe
themtohappen.Wecan
\o"calculate��ʲô��˼"calculate
whereweareinthecycleandcompareitwith
\o"observation��ʲô��˼"observation,"hesays."Ican'tseeanywayoftesting[Ehrlich's]ideatoseewhereweareinthe
\o"temperature��ʲô��˼"temperature
\o"oscillation��ʲô��˼"oscillation."10Ehrlichconcedesthis."Ifthereisawaytotestthistheoryonthesun,Ican'tthinkofonethatispractical,"hesays.That'sbecause
\o"variation��ʲô��˼"variation
over41,000to100,000yearsistoogradualtobeobserved.However,theremaybeawaytotestitinotherstars:reddwarfs.Theircoresaremuchsmallerthanthatofthesun,andsoEhrlichbelievesthatthe
\o"oscillation��ʲô��˼"oscillation
periodscouldbeshortenoughtobeobserved.Hehasyetto
\o"calculate��ʲô��˼"calculate
the
\o"precise��ʲô��˼"precise
periodorthe
\o"extent��ʲô��˼"extent
of\o"variation��ʲô��˼"variation
inbrightnesstobeexpected.11NigelWeiss,asolarphysicistattheUniversityofCambridge,isfarfrom
\o"convinced��ʲô��˼"convinced.HedescribesEhrlich'sclaimsas"utterly
\o"implausible��ʲô��˼"implausible".EhrlichcountersthatWeiss'sopinionisbasedonthestandardsolarmodel,whichfailstotakeintoaccountthe
\o"magnetic��ʲô��˼"magnetic
instabilitiesthatcausethe
\o"temperature��ʲô��˼"temperature
fluctuations.(716words)Questions1-4CompleteeachofthefollowingstatementswithOneorTwonamesofthescientistsfromtheboxbelow.Writethe
\o"appropriate��ʲô��˼"appropriate
lettersA-Einboxes1-4onyouranswersheet.A.AttilaGrandpierreSeepara.5:forthepastmillionyears,iceageshaveoccurredroughlyevery100,000years.Beforethat,theyoccurredroughlyevery41,000years.6.FalseSeepara.7:"InMilankovitch,thereiscertainlynogoodideawhythe
\o"frequency��ʲô��˼"frequency
shouldchangefromonetoanother,"...Noristhe
\o"transition��ʲô��˼"transition
problemtheonlyonetheMilankovitchtheoryfaces.7.NotGivenSeepara.8:ifseaicebeginstoformbecauseofa
\o"slight��ʲô��˼"slight
cooling,carbondioxide?islockedintotheice.Thatweakensthe
\o"greenhouse��ʲô��˼"greenhouse
effect.(Thepassagedoesn抰mentionanythingaboutlockingCo2intoiceartificially.)8.TrueSeepara.9:thereisnolackofsuchmechanisms."Ifyouaddtheireffectstogether,thereismorethanenoughfeedbacktomakeMilankovitchwork,"?"Theproblemnowisidentifyingwhichmechanismsareatwork."ThisiswhyscientistslikeEdwardsarenotyetreadytogiveuponthe\o"current��ʲô��˼"current
theory.9.TrueSeethesentencesinpara.9(AccordingtoEdwards,卙esays."Ican'tseeanywayoftesting[Ehrlich's]ideatoseewhereweareinthe
\o"temperature��ʲô��˼"temperature
\o"oscillation��ʲô��˼"oscillation.")andpara.10(Ehrlichconcedesthis."Ifthereisawaytotestthistheoryonthesun,Ican’tthinkofonethatispractical).10.constantSeepara.2:Accordingtothestandardview,the
\o"temperature��ʲô��˼"temperature
ofthesun's
\o"core��ʲô��˼"core
isheld\o"constant��ʲô��˼"constant
bythe
\o"opposing��ʲô��˼"opposing
pressuresof
\o"gravity��ʲô��˼"gravity
andnuclear
\o"fusion��ʲô��˼"fusion.11.orbitSeepara.6:Mostscientistsbelievethattheiceagesaretheresultof
\o"subtle��ʲô��˼"subtle
changesinEarth’sorbit,匛arth'sorbitgraduallychangesshapefroma
\o"circle��ʲô��˼"circle
toa
\o"slight��ʲô��˼"slight
\o"ellipse��ʲô��˼"ellipse
andbackagainroughlyevery100,000years.12.instabilitiesS
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