听力原文及答案4.docx
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听力原文及答案4
Conversation1
Listentoaconversationbetweenastudentandaprofessor.
Professor:
Ok,Carl,howcanIhelpyou?
Student:
It’saboutmytermpaperfortheurbanplanningclass.Insteadofjustdoinglibraryresearch,Iwasthinkingofdoingasurveyofmyownandusingthedatainthereport.
Professor:
That’saniceidea.Ithinkdoingthiskindofhands-onprojectisgreatexperience,especiallyifyoudecidetogotograduateschool.
Student:
But,I’vebeenhavingalotofproblemsdesigningthesurvey.
Professor:
Ahh…It’snotaseasyasitlooksisit?
Student:
No,nowI’mnotevensureifIshouldstickwithmyplanorswitchbacktoamoretraditionalpaper.
Professor:
Well,youmightaswellgetsomeexperiencesoonerratherthanlater.What’syourtopicagain?
Student:
Nothingreallycomplex.IjustwantedtosurveylocalpeopleabouttheproposaltowidenRoute62fromatwolaneroadtoafourlanehighway.
Professor:
Ok…
Student:
So,howdoIgoaboutselectingthepeopleIwanttosurvey?
AlotofwhatIreadhasstressedhavingarepresentativesample,butI’mnotsurehowtodoit.
Professor:
Well,yesarepresentativesampleiscrucial.Youwantthepeopleyousurveytobeasclosetoanaccuratereflectionofthelargerpopulationyou’reinterestedinaspossible.Imaginethatthetownisacakewithraisinsinitandimaginethatforsomereasonmostoftheraisinsendupononesideofthecake.Ifyoucutapiecefromtheotherside,wouldthatbetrulyrepresentative?
Woulditbeanaccuratereflectionofthecake?
Student:
No,you’dbemissingtheraisins.
Professor:
Exactly,soforyourprojectwhatifyouonlysurveyedpeoplewholivedinhousesalongRoute62?
Doyouthinkthatwouldbeuseful?
Student:
Well,nobecauseeveryonetherewouldprobablybeopposedtothewidening.
Professor:
Yes,andthat’swhyarepresentativesampleisimportant.Youdon’twantasamplethat’sbiasedtoostronglyonewayortheother,sohowdoyoudothat?
Student:
Well,Icouldmakesuremysurveyreachespeopleinallpartsofthetown.
Professor:
Good!
So,howcanyoudothat?
Student:
Well,Iwasgoingtomakephonecalls,justchoosenumbersatrandomfromthelocalphonedirectory.It’sbetterthanpassingoutquestionnairesbecausepeopleoftendon’tmailthemback,butIdon’tseehowIcangetarepresentativesampleusingthephone.
Professor:
Well,makesureyou’regettinganicebalanceofnumbers.Thephonecompanycantellyouwhatnumbershavebeenassignedtodifferentpartsoftown;forexample,phonenumbersinmyneighborhoodstartwith256andIliveontheedgeoftown…where,Iguessyou’regoingtofindalotof‘pro-highway’people,somakesureyoudon’tcallmostly256numbers.
Lecture1
Listentopartofalectureinanancienthistoryclass.
Professor:
Alright,solikemanyancientcivilizations,theRomanshelpeddevelopimportanttechnologies.Todaywe’regoingtofocusononeparticulartechnologicaldevelopmentthatwasasartistic,aspleasingtotheeye,asitwasfunctional.I’mtalkingabouttheirwaterdistributionsystem,alsoknownasaqueducts.Aqueductsarechannelsthatleadwaterfromitssource,likeanundergroundspring,toanotherlocation,usuallyacity.Thisisimportantbecausewell,citiesneedlargewatersuppliesandtheRomanEmpirehadalotoflargecities.Rememberitwasoneofthelargestancientempires.Withouttheaqueducts,whichwerebigthroughouttheempire,welltheRomanEmpireprobablywouldn’thavespreadsofarorhadsuchhighlypopulatedcities.TakethecityofRome,thecapitaloftheRomanEmpire;it’sestimatedthatithadbetween500,000andamillionresidents.Tosupportallthesepeoplewithwaterwasamajorengineeringachievement.Overaperiodofseveralhundredyears,elevenaqueductswerebuilttobringwatertoRomefromasfarawayas90kilometersandsomeestimatethattheydeliveredaboutathousandmetersofwaterperpersonperday.Well,thatamountofwaterwouldhavebeenimpossibletofindinRomeandtheareaimmediatelysurroundingit,plustheonlywatersourceinorclosetothecitywouldhavequicklybecomepolluted.Imeanwe’retalkingabouthalfamillionpeopleormore.Speakingofallthosepeople,aqueductsalsohelpedkeepancientRomeclean.Theconstantoverflowofwaterwouldflushthecity’strashout.
So,howwereaqueductsbuilt?
Well,firsttheyhadtofindafreshwatersource,usuallyanundergroundspring.Onceaspringwaslocatedandtestedforquality,engineerswouldfindthebestroute;theroutewiththemostgradual,gentlegradient,orslope,downwardstowardsthecity.Thatmeansthesourcehadtobehigher,atahigherelevationthanthecityitwasservingsincethesystemofaqueductsreliedentirelyongravitytoleadthewaterdownthroughthepipesandchannels.TheRomanaqueductswerebuiltoutofpipes,generallyleadorearthenwarepipes,whichmadeupthebulkofanaqueduct.Tunnelsortrenchesweredugandthepipeswerelaidandcovered.Thiswaymostofanaqueductwashiddenandthelandabovecouldstillbeutilized.Alsotunnelswerelessvulnerabletoenemiesandsooneofthefirstaqueductswasbuiltentirelyunderground.Someofthesetunnels,specificallytheonesdeepunderthemountains,aresuchamazingengineeringachievements,it’sstillamysterytoushowancientRomanswentaboutsurveyingandbuildingthemandifthelandscapeinsomeareasdidn’tfitthespecificationsneededfortheaqueduct,ifsaytherewasasharpdip,ariverbed,orvalley,thenengineersbuiltanarcade.
AsyoucanseeaRomanarcadeisaseriesofarches.Anopenconcretechannelrunsalongthetopwhichkeptthewateratacertainleveleventhoughthelanddippeddownbecauseifyoulostthatlevelitwashardtogetitbackupagain.Thearcadesarewhatmanypeoplethinkofwhentheyhear‘Romanaqueducts’eventhoughthegreaterportionoftheaqueductssystemwasunderground,butthearcadesareabovegroundwhereeveryonecanseethemandthisiswheretheconjunctionofengineeringtechniquesandartisticcreationcomesin.
Thearcadeswerecertainlybeautiful.Infact‘rainbow’means…(Incomprehensible)…wellthey’rekindoflikelandscapeartbutthebeautycanmakeusforgetthepurposetheyserved,theirpracticaltechnologicalvalue.So,itwasn’tjustthepracticalaspectsofarcadesthatwereimportanttotheRomansandthearchedarcadeswereobviouslypractical,right?
Sayyouhadtobuildahighstructure.Buildingarchesrequireslessmaterialthanbuildingsolidwalls,right?
AndifyoucompareRomanaqueductsyou’llseetherefinedRomanskillsinbothstyleandscale.Arcades,especiallythosethatwerebuiltlater,areperfectexamplesofthemarriageoffunctionalityandelegance;qualitiesthatwereveryimportanttoRomanarchitects;qualitiesarchitectsstillstrivetoemulatetoday.
Lecture2
Listentopartofalectureinageologyclass.
Student:
Professor,Iwasalittleconfusedbyourreading.Imean,Iunderstoodit;thestuffaboutradioactivedecay,butI’mnotsureabouthowitfitsin.
Professor:
That’sunderstandable.Imeanttogiveyousomebackgroundinformationonradioactivedecaylastweek,butweranoutoftimeandIdidn’tgetachancetoexplainitsimportancetounderstandinggeology.So,togetanideaofwhywe’llbediscussingatopicthatmightseemmoreappropriatetoaphysicsclassthanageologyclass,let’squicklyreviewalittlehistory.Upuntilthe18thcentury,geologydidn’treallyexist,atleastnotasweknowittodayandthemostpopulartheoryabouttheageofEarthsuggestedtheworldwasjustseveralthousandyearsold,butthenJamesHuttoncamealong.
JamesHuttoncouldbeconsideredthefatherofmoderngeology.Heusedscientificobservations,notingphenomenalikeerosion,toformulateatheoryabouthowandwhenEarthwasformed.HuttoncorrectlyassertedthatEarth’ssurfacewasconstantlychangingandheattributedthatconstantchangetoafundamentalforce:
Earth’sinternalheat.ThatinternalheatwassupposedlyproducedbyanunendingseriesofchemicalreactionsinEarth’sinteriorandthereisoneotherimportantideaHuttonhad.Hebelievedthatgeologicalforcesthatareatworkinourtime,volcaniceruptions,orerosion,orwhatever,allthesethingswerealsohappeninginthepastatapproximatelythesamepacestheyarenow.Buildingonthatideaandonhisestimatesofhowlongitmusthavetakenformanyoftherockformationsweseetodaytohaveformed,HuttonhypothesizedthattheEarthwasmucholderthanpeoplehadpreviouslythought.
Student:
Excuseme,butyousaidEarth’sheatcamefromanunendingtheoryofchemicalreactionsinEarth’sinterior?
But,unendingmeansitgoesonforever,sortoflikeaperpetualmotionmachine.Ithoughtthat’snotpossible.
Professor:
You’reright.Anunendingseriesofchemicalreactionswouldbelikeperpetualmotionandthelawsofphysicsareclearthere’snowaytokeeponproducingenergylikethatwithoutusingupwhatever’sfuelingthosereactions,sothesechemicalreactionscouldnotgoonforever.OnescientistwhostronglyemphasizedthispointwasWilliamThompson,betterknownasLordKelvin.
LordKelvin,herejectedtheideathatcontinualchemicalreactionsproducedEarth’sinternalheat.Instead,heassumedthatEarthhadstartedoutasmoltenrock,hotliquidrock,andhadbeencoolingeverysinceitwasinitsoriginalmoltenstate.Kelvinthencombinedthisassumptionwithsomesolidfacts.HeknewfromdescentsdownintosomeofthedeepminesinEuropethatEarth’stemperaturepredictablyincreaseswithdepth.It’shotteratthebottomofamineshaft.KelvinreasonedthatenergyfromEarth’shotinteriorwasbeinglost,drainedawayupatthesurfacea