2012年雅思考试阅读模拟试题8

1、2012年雅思考试阅读模拟试题（含答案）There'sadimmerswitchinsidethesunthatcausesitsbrightnesstoriseandfallontimescalesofaround100,000yearsexactlythesameperiodasbetweeniceagesonEarth.Sosaysaphysicistwhohascreatedacomputermodelofourstar'score.RobertEhrlichofGeorgeMasonUniversityinFairfax,Virginia,modelledtheeff

2、ectoftemperaturefluctuationsinthesun'sinterior.Accordingtothestandardview,thetemperatureofthesun'scoreisheldconstantbytheopposingpressuresofgravityandnuclearfusion.However,Ehrlichbelievedthatslightvariationsshouldbepossible.HetookashisstartingpointtheworkofAttilaGrandpierreoftheKonkolyObserv

3、atoryoftheHungarianAcademyofSciences.In2005,Grandpierreandacollaborator,Gboragoston,calculatedthatmagneticfieldsinthesun'scorecouldproducesmallinstabilitiesinthesolarplasma.Theseinstabilitieswouldinducelocalisedoscillationsintemperature.Ehrlich'smodelshowsthatwhilstmostoftheseoscillationscan

4、celeachotherout,somereinforceoneanotherandbecomelong-livedtemperaturevariations.Thefavouredfrequenciesallowthesun'scoretemperaturetooscillatearounditsaveragetemperatureof13.6millionkelvinincycleslastingeither100,000or41,000years.Ehrlichsaysthatrandominteractionswithinthesun'smagneticfieldcou

5、ldflipthefluctuationsfromonecyclelengthtotheother.1 ThesetwotimescalesareinstantlyrecognisabletoanyonefamiliarwithEarth'siceages:forthepastmillionyears,iceageshaveoccurredroughlyevery100,000years.Beforethat,theyoccurredroughlyevery41,000years.Mostscientistsbelievethattheiceagesaretheresultofsubt

6、lechangesinEarth'sorbit,knownastheMilankovitchcycles.OnesuchcycledescribesthewayEarth'sorbitgraduallychangesshapefromacircletoaslightellipseandbackagainroughlyevery100,000years.ThetheorysaysthisalterstheamountofsolarradiationthatEarthreceives,triggeringtheiceages.However,apersistentproblemwi

7、ththistheoryhasbeenitsinabilitytoexplainwhytheiceageschangedfrequencyamillionyearsago."InMilankovitch,thereiscertainlynogoodideawhythefrequencyshouldchangefromonetoanother,"saysNeilEdwards,aclimatologistattheOpenUniversityinMiltonKeynes,UK.NoristhetransitionproblemtheonlyonetheMilankovitch

8、theoryfaces.EhrlichandothercriticsclaimthatthetemperaturevariationscausedbyMilankovitchcyclesaresimplynotbigenoughtodriveiceages.However,EdwardsbelievesthesmallchangesinsolarheatingproducedbyMilankovitchcyclesarethenamplifiedbyfeedbackmechanismsonEarth.Forexample,ifseaicebeginstoformbecauseofaslight

9、cooling,carbondioxidethatwouldotherwisehavefounditswayintotheatmosphereaspartofthecarboncycleislockedintotheice.ThatweakensthegreenhouseeffectandEarthgrowsevencolder.AccordingtoEdwards,thereisnolackofsuchmechanisms."Ifyouaddtheireffectstogether,thereismorethanenoughfeedbacktomakeMilankovitchwor

10、k,"hesays."Theproblemnowisidentifyingwhichmechanismsareatwork."ThisiswhyscientistslikeEdwardsarenotyetreadytogiveuponthecurrenttheory."Milankovitchcyclesgiveusiceagesroughlywhenweobservethemtohappen.Wecancalculatewhereweareinthecycleandcompareitwithobservation,"hesays."

11、Ican'tseeanywayoftestingEhrlich'sideatoseewhereweareinthetemperatureoscillation."Ehrlichconcedesthis."Ifthereisawaytotestthistheoryonthesun,Ican'tthinkofonethatispractical,"hesays.That'sbecausevariationover41,000to100,000yearsistoogradualtobeobserved.However,theremaybe

12、awaytotestitinotherstars:reddwarfs.Theircoresaremuchsmallerthanthatofthesun,andsoEhrlichbelievesthattheoscillationperiodscouldbeshortenoughtobeobserved.Hehasyettocalculatethepreciseperiodortheextentofvariationinbrightnesstobeexpected.NigelWeiss,asolarphysicistattheUniversityofCambridge,isfarfromconv

13、inced.HedescribesEhrlich'sclaimsas"utterlyimplausible".EhrlichcountersthatWeiss'sopinionisbasedonthestandardsolarmodel,whichfailstotakeintoaccountthemagneticinstabilitiesthatcausethetemperaturefluctuations.(716words)Questions1-4CompleteeachofthefollowingstatementswithOneorTwonameso

14、fthescientistsfromtheboxbelow.WritetheappropriatelettersA-Einboxes1-4onyouranswersheet.A. AttilaGrandpierreB. GaboragostonC. NeilEdwardsD. NigelWeissE. RobertEhrlich1. .claimsthere担adimmerswitchinsidethesunthatcausesitsbrightnesstoriseandfallinperiodsaslongasthosebetweeniceagesonEarth.2. .calculated

15、thattheinternalsolarmagneticfieldscouldproduceinstabilitiesinthesolarplasma.holdsthatMilankovitchcyclescaninducechangesinsolarheatingonEarthandthechangesareamplifiedonEarth.3. .doesn'tbelieveinEhrlich'sviewpointsatall.Questions5-9Dothefollowingstatementsagreewiththeinformationgiveninthereadi

16、ngpassage?Inboxes5-9onyouranswersheetwriteTRUEifthestatementistrueaccordingtothepassageFALSEifthestatementisfalseaccordingtothepassageNOTGIVENiftheinformationisnotgiveninthepassage4. Theiceageschangedfrequencyfrom100,000to41,000yearsamillionyearsago.ThesoleproblemthattheMilankovitchtheorycannotsolve

17、istoexplainwhytheiceagefrequencyshouldshiftfromonetoanother.5. Carbondioxidecanbelockedartificiallyintoseaicetoeliminatethegreenhouseeffect.SomescientistsarenotreadytogiveuptheMilankovitchtheorythoughtheyhaven'tfiguredoutwhichmechanismsamplifythechangesinsolarheating.6. BothEdwardsandEhrlichbeli

18、evethatthereisnopracticalwaytotestwhenthesolartemperatureoscillationbeginsandwhenends.Questions10-14Completethenotesbelow.ChooseonesuitablewordfromtheReadingPassageaboveforeachanswer.Writeyouranswersinboxes10-14onyouranswersheet.Thestandardviewassumesthattheopposingpressuresofgravityandnuclearfusion

19、hesun'sinterior,buttheslightchangesintheearth's.11.alterthetemperatureontheearthandcauseiceagesevery100,000years.ABritishscientist,however,challengesthisviewbyclaimingthattheinternalsolarmagnetic.12.caninducethetemperatureoscillationsinthesun'sinterior.Thesun

20、9;scoretemperatureoscillatesarounditsaveragetemperaturein.13.lastingeither100,000or41,000years.Aeractionswithinthesun'smagneticfieldcouldflipthefluctuationsfromonecyclelengthtotheother,whichexplainswhytheiceageschangedfrequencyamillionyearsago.Answerkeysandexplanations:1. ESeethesent

21、encesinparagraph1(There'sadimmerswitchinsidethesunthatcausesitsbrightnesstoriseandfallontimescalesofaround100,000yearsexactlythesameperiodasbetweeniceagesonEarth.Sosaysaphysicistwhohascreatedacomputermodelofourstar'score.)andpara.2(RobertEhrlichofGeorgeMasonUniversityinFairfax,Virginia,model

22、ledtheeffectoftemperaturefluctuationsinthesun'sinterior.)2. ABSeepara.3:?istyle='normal'>Grandpierreandacollaborator,Gaboragoston,calculatedthatmagneticfieldsinthesun'scorecouldproducesmallinstabilitiesinthesolarplasma.3. CSeepara.8:Edwardsbelievesthesmallchangesinsolarheatingprod

23、ucedbyMilankovitchcyclesarethenamplifiedbyfeedbackmechanismsonEarth.4. DSeepara.11:NigelWeiss,asolarphysicistattheUniversityofCambridge,isfarfromconvinced.HedescribesEhrlich'msasa"utterlyimplausible5. FalseSeepara.5:forthepastmillionyears,iceageshaveoccurredroughlyevery100,000years.Beforeth

24、at,theyoccurredroughlyevery41,000years.6. FalseSeepara.7:"InMilankovitch,thereiscertainlynogoodideawhythefrequencyshouldchangefromonetoanother,".NoristhetransitionproblemtheonlyonetheMilankovitchtheoryfaces.7. NotGivenSeepara.8:ifseaicebeginstoformbecauseofaslightcooling,carbondioxide?islo

25、ckedintotheice.Thatweakensthegreenhouseeffect.(Thepassagedoesn抉mentionanythingaboutlockingCo2intoiceartificially.)8. TrueSeepara.9:thereisnolackofsuchmechanisms."Ifyouaddtheireffectstogether,thereismorethanenoughfeedbacktomakeMilankovitchwork,”?”Theproblemnowisidentifyingwhichmechanismsareatwork."ThisiswhyscientistslikeEdwardsarenotyetreadytogiveuponthecurrenttheory.9. TrueSeethesentencesinpara.9(AccordingtoEdwards,勘esays."Ican'tseeanywayoftestingEhrlich'sideatoseewhereweareinthetemperatureoscillation.")andpara.10(Ehrlichconcedesthis."Ifthereisawaytotestthist