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1There'sadimmerswitchinsidethesunthatcausesitsbrightnesstoriseandfallontimescalesofaround100,000years-exactlythesameperiodasbetweeniceagesonEarth.Sosaysaphysicistwhohascreatedacomputermodelofourstar'score.
2RobertEhrlichofGeorgeMasonUniversityinFairfax,Virginia,modelledtheeffectoftemperaturefluctuationsinthesun'sinterior.Accordingtothestandardview,thetemperatureofthesun'scoreisheldconstantbytheopposingpressuresofgravityandnuclearfusion.However,Ehrlichbelievedthatslightvariationsshouldbepossible.
3HetookashisstartingpointtheworkofAttilaGrandpierreoftheKonkolyObservatoryoftheHungarianAcademyofSciences.In2005,Grandpierreandacollaborator,Gáborágoston,calculatedthatmagneticfieldsinthesun'scorecouldproducesmallinstabilitiesinthesolarplasma.Theseinstabilitieswouldinducelocalisedoscillationsintemperature.
4Ehrlich'smodelshowsthatwhilstmostoftheseoscillationscanceleachotherout,somereinforceoneanotherandbecomelong-livedtemperaturevariations.Thefavouredfrequenciesallowthesun'scoretemperaturetooscillatearounditsaveragetemperatureof13.6millionkelvinincycleslastingeither100,000or41,000years.Ehrlichsaysthatrandominteractionswithinthesun'smagneticfieldcouldflipthefluctuationsfromonecyclelengthtotheother.
5ThesetwotimescalesareinstantlyrecognisabletoanyonefamiliarwithEarth'siceages:forthepastmillionyears,iceageshaveoccurredroughlyevery100,000years.Beforethat,theyoccurredroughlyevery41,000years.
6MostscientistsbelievethattheiceagesaretheresultofsubtlechangesinEarth'sorbit,knownastheMilankovitchcycles.OnesuchcycledescribesthewayEarth'sorbitgraduallychangesshapefromacircletoaslightellipseandbackagainroughlyevery100,000years.ThetheorysaysthisalterstheamountofsolarradiationthatEarthreceives,triggeringtheiceages.However,apersistentproblemwiththistheoryhasbeenitsinabilitytoexplainwhytheiceageschangedfrequencyamillionyearsago.
7"InMilankovitch,thereiscertainlynogoodideawhythefrequencyshouldchangefromonetoanother,"saysNeilEdwards,aclimatologistattheOpenUniversityinMiltonKeynes,UK.NoristhetransitionproblemtheonlyonetheMilankovitchtheoryfaces.EhrlichandothercriticsclaimthatthetemperaturevariationscausedbyMilankovitchcyclesaresimplynotbigenoughtodriveiceages.
8However,EdwardsbelievesthesmallchangesinsolarheatingproducedbyMilankovitchcyclesarethenamplifiedbyfeedbackmechanismsonEarth.Forexample,ifseaicebeginstoformbecauseofaslightcooling,carbondioxidethatwouldotherwisehavefounditswayintotheatmosphereaspartofthecarboncycleislockedintotheice.ThatweakensthegreenhouseeffectandEarthgrowsevencolder.
9AccordingtoEdwards,thereisnolackofsuchmechanisms."Ifyouaddtheireffectstogether,thereismorethanenoughfeedbacktomakeMilankovitchwork,"hesays."Theproblemnowisidentifyingwhichmechanismsareatwork."ThisiswhyscientistslikeEdwardsarenotyetreadytogiveuponthecurrenttheory."Milankovitchcyclesgiveusiceagesroughlywhenweobservethemtohappen.Wecancalculatewhereweareinthecycleandcompareitwithobservation,"hesays."Ican'tseeanywayoftesting[Ehrlich's]ideatoseewhereweareinthetemperatureoscillation."
10Ehrlichconcedesthis."Ifthereisawaytotestthistheoryonthesun,Ican'tthinkofonethatispractical,"hesays.That'sbecausevariationover41,000to100,000yearsistoogradualtobeobserved.However,theremaybeawaytotestitinotherstars:reddwarfs.Theircoresaremuchsmallerthanthatofthesun,andsoEhrlichbelievesthattheoscillationperiodscouldbeshortenoughtobeobserved.Hehasyettocalculatethepreciseperiodortheextentofvariationinbrightnesstobeexpected.
11NigelWeiss,asolarphysicistattheUniversityofCambridge,isfarfromconvinced.HedescribesEhrlich'sclaimsas"utterlyimplausible".EhrlichcountersthatWeiss'sopinionisbasedonthestandardsolarmodel,whichfailstotakeintoaccountthemagneticinstabilitiesthatcausethetemperaturefluctuations.
Questions1-4
CompleteeachofthefollowingstatementswithOneorTwonamesofthescientistsfromtheboxbelow.
WritetheappropriatelettersA-Einboxes1-4onyouranswersheet.
A.AttilaGrandpierre
B.Gáborágoston
C.NeilEdwards
D.NigelWeiss
E.RobertEhrlich
1....claimsthereadimmerswitchinsidethesunthatcausesitsbrightnesstoriseandfallinperiodsaslongasthosebetweeniceagesonEarth.
2....calculatedthattheinternalsolarmagneticfieldscouldproduceinstabilitiesinthesolarplasma.
3....holdsthatMilankovitchcyclescaninducechangesinsolarheatingonEarthandthechangesareamplifiedonEarth.
4....doesn'tbelieveinEhrlich'sviewpointsatall.
Questions5-9
Dothefollowingstatementsagreewiththeinformationgiveninthereadingpassage?
Inboxes5-9onyouranswersheetwrite
TRUEifthestatementistrueaccordingtothepassage
FALSEifthestatementisfalseaccordingtothepassage
NOTGIVENiftheinformationisnotgiveninthepassage
5.Theiceageschangedfrequencyfrom100,000to41,000yearsamillionyearsago.
6.ThesoleproblemthattheMilankovitchtheorycannotsolveistoexplainwhytheiceagefrequencyshouldshiftfromonetoanother.
7.Carbondioxidecanbelockedartificiallyintoseaicetoeliminatethegreenhouseeffect.
8.SomescientistsarenotreadytogiveuptheMilankovitchtheorythoughtheyhaven'tfiguredoutwhichmechanismsamplifythechangesinsolarheating.
9.BothEdwardsandEhrlichbelievethatthereisnopracticalwaytotestwhenthesolartemperatureoscillationbeginsandwhenends.
Questions10-14
Completethenotesbelow.
ChooseonesuitablewordfromtheReadingPassageaboveforeachanswer.
Writeyouranswersinboxes10-14onyouranswersheet.
Thestandardviewassumesthattheopposingpressuresofgravityandnuclearfusionsholdthetemperature...10...inthesun'sinterior,buttheslightchangesintheearth's...11...alterthetemperatureontheearthandcauseiceagesevery100,000years.ABritishscientist,however,challengesthisviewbyclaimingthattheinternalsolarmagnetic...12...caninducethetemperatureoscillationsinthesun'sinterior.Thesun'scoretemperatureoscillatesarounditsaveragetemperaturein...13...lastingeither100,000or41,000years.Andthe...14...interactionswithinthesun'smagneticfieldcouldflipthefluctuationsfromonecyclelengthtotheother,whichexplainswhytheiceageschangedfrequencyamillionyearsago.
1.AEuropeanspacecrafttookofftodaytospearheadthesearchforanother"Earth"amongthestars.
2.TheCorotspacetelescopeblastedoffaboardaRussianSoyuzrocketfromtheBaikonurcosmodromeinKazakhstanshortlyafter2.20pm.
3.Corot,shortforconvectionrotationandplanetarytransits,isthefirstinstrumentcapableoffindingsmallrockyplanetsbeyondthesolarsystem.Anysuchplanetsituatedintherightorbitstandsagoodchanceofhavingliquidwateronitssurface,andquitepossiblylife,althoughaleadingscientistinvolvedintheprojectsaiditwasunlikelytofind"anylittlegreenmen".
4.DevelopedbytheFrenchspaceagency,CNES,andpartneredbytheEuropeanSpaceAgency(ESA),Austria,Belgium,Germany,BrazilandSpain,Corotwillmonitoraround120,000starswithits27cmtelescopefromapolarorbit514milesabovetheEarth.Overtwoandahalfyears,itwillfocusonfivetosixdifferentareasofthesky,measuringthebrightnessofabout10,000starsevery512seconds.
5."Atthepresentmomentwearehopingtofindoutmoreaboutthenatureofplanetsaroundstarswhicharepotentialhabitats.Wearelookingathabitableplanets,notinhabitedplanets.Wearenotgoingtofindanylittlegreenmen,"ProfessorIanRoxburgh,anESAscientistwhohasbeeninvolvedwithCorotsinceitsinception,toldtheBBCRadio4Todayprogramme.
6.ProfRoxburghsaiditwashopedCorotwouldfind"rockyplanetsthatcoulddevelopanatmosphereand,iftheyaretherightdistancefromtheirparentstar,theycouldhavewater".
7.Tosearchforplanets,thetelescopewilllookforthedimmingofstarlightcausedwhenanobjectpassesinfrontofastar,knownasa"transit".Althoughitwilltakemoresophisticatedspacetelescopesplannedinthenext10yearstoconfirmthepresenceofanEarth-likeplanetwithoxygenandliquidwater,Corotwillletscientistsknowwheretopointtheirlenses.
8.MeasurementsofminutechangesinbrightnesswillenablescientiststodetectgiantJupiter-likegasplanetsaswellassmallrockyones.Itistherockyplanets-thatcouldbenobiggerthanabouttwicethesizeoftheEarth-whichwillcausethemostexcitement.Scientistsexpecttofindbetween10and40ofthesesmallerplanets.
9.Corotwillalsoprobeintostellarinteriorsbystudyingtheacousticwavesthatrippleacrossthesurfaceofstars,atechniquecalled"asteroseismology".
10.Thenatureoftheripplesallowsastronomerstocalculateastar’sprecisemass,ageandchemicalcomposition.
11."Aplanetpassinginfrontofastarcanbedetectedbythefallinlightfromthatstar.Smalloscillationsofthestaralsoproducechangesinthelightemitted,whichrevealwhatthestarismadeofandhowtheyarestructuredinternally.Thisdatawillprovideamajorboosttoourunderstandingofhowstarsformandevolve,"ProfRoxburghsaid.
12.Sincethediscoveryin1995ofthefirst"exoplanet"-aplanetorbitingastarotherthantheSun-morethan200othershavebeenfoundbyground-basedobservatories.
13.Untilnowtheusualmethodoffindingexoplanetshasbeentodetectthe"wobble"theirgravityimpartsonparentstars.ButonlygiantgaseousplanetsbiggerthanJupitercanbefoundthisway,andtheyareunlikelytoharbourlife.
14.Inthe2010s,ESAplanstolaunchDarwin,afleetoffourorfiveinterlinkedspacetelescopesthatwillnotonlyspotsmallrockyplanets,butanalysetheiratmospheresforsignsofbiologicalactivity.
15.Ataroundthesametime,theUSspaceagency,Nasa,willlaunchTerrestrialPlanetFinder,anotherspacetelescopedesignedtolocateEarth-likeplanets.
ChoosetheappropriateletterfromA-Dforquestion1.
1.Corotisaninstrumentwhich
(A)canhelptosearchforcertainplanets
(B)isusedtofindplanetsintheorbit
(C)canlocateplanetswithhumanbeings
(D)canspotanyplanetswithwater.
Dothefollowingstatementsagreewiththeinformationgiveninthereadingpassage?Forquestions2-5write
TRUEifthestatementagreeswiththeinformation
FALSEifthestatementcontraictstheinformation
NOTGIVENifthereisnoinformationonthisinthepassage
2.Scientistsaretryingtofindoutabouttheplanetsthatcanbeinhabited.
3.BBCRadio4recentlyfocusesonthebroadcastingofCorot.
4.Passingobjectsmightcauseafallinlight.
5.CorotcantellwhetherthereisanotherEarth-likeplanet.
Basedonyourreadingofthepassage,completethesentencesbelowwithwordstakenfromthepassage.UseNOMORETHANTHREEWORDSforeachanswer.
Withmeasurements,scientistswillbeabletosearchforsomegaseousandrockyplanets.Theywillbeextremelyexcitediftheycandiscoversomesmall6.__________,theexpectednumberofwhichcouldbeupto7.__________.
Corotwillenablescientiststostudythe8.__________ofstars.Inthisway,astar’smass,ageandchemicalcompositioncanbecalculated.
AccordingtoProfRoxburgh,changesinlightcanbecausedbypassingplanetsorstar9.__________.Therelatedstatisticscangainusabetter10.__________ofthestarformationandevolvement.
Observatorieshavefoundmanyexoplanets,whichare11.__________otherstarsthantheSun.Thecommonwayusedinfindingexoplanetscanonlydetecthugegasplanets,whichdonot12.___________.
WiththelaunchingofDarwin,astronomerswillbeabletoanalysewhetherthoserockyplanetshave13.__________forlife.
