椰子11月大第五次課版

托福寫(xiě)作11綜合寫(xiě)作技綜合寫(xiě)閱讀部分 點(diǎn)（開(kāi)頭段）注意最后一句話 綜合寫(xiě)部分聽(tīng)完注意花15s順一遍大意再打文TPO30Alittleover2,200yearsago,theRomannavyattackedtheGreekportcityofSyracuse.Accordingtosomeancienthistorians,theGreeksdefendedthemselveswithaningeniousweaponcalleda"burningmirror"：apolishedcoppersurfacecurvedtofocustheSun'sraysontoRomanships,causingthemtocatchfire.However,wehaveseveralreasonsthatthestoryoftheburningmirrorisjustamyththeGreeksofSyracuseneverrallybuiltsuchaFirst,theancientGreekswerenottechnologicallyadvancedenoughtomakesuchadevice.Amirrorthatwouldfocussunlightwithsufficientintensitytosetshipsonfirehavetobeseveralmeterswide.Moreover,themirrorhavetohaveaverypreciseparaboliccurvature(acurvaturederivedfromageometricshapeknownastheparabola).Thetechnologyformanufacturingalargesheetofcopperwithsuchspecificationsdidnotexistintheancientworld.Second,theburningmirrorwouldhavetakenalongtimetosettheshipsonfire.Inanexperimentconductedtodeterminewhetheraburningmirrorwasfeasible,adeviceconcentratingtheSun'sraysonawoodenobject30metersaway

ten

tosettheobjectonfire;andthattime,theobjecthadtobeunmoving.ItisunlikelythatRomanshipsstayedperfectlystillforthatmuchtime,suchaweaponwouldthereforehavebeenveryimpracticalandThird,Third,aburningmirrordoesnotseemlikeanimprovement Shootingatanenemy'sshipswithflamingarrowswascommonwayofsettingtheshipsonfire.Theburningmirrorandflamingarrowswouldhavebeeneffectiveataboutthesamedistance.SotheGreekshadnoreasontobuildaweaponlikeaburningmirror.TPO30First,theGreeksdidnotneedtoformasinglesheetoftomakealarge,burningmirror.Anexperimenthasthatdozensofsmallindividuallyflatpiecesofpolishedcouldbearrangedintoaparabolicshapeandformalarge,burningmirror.TheGreekmathematiciansknowthepropertiesoftheparabolaandsocouldhavedirectedtheassemblyofsmallmirrorpiecesintotheparabolicshape.Second,abouthowlongitwouldtaketosetashiponfirewithaburningmirror.Theexperimentthereadingselectionmentionsassumesthattheburningmirrorwasusedtosetwoodoftheboatonfire,that’swhattakestenminutes.Romanboatswerenotmadejustofwood.Therewereothermaterialsinvolvedaswell.Forexample,tosealthespacesbetweenwoodenboardsandmakethemwaterproof,theancientboat-buildersusedastickysubstancecalledpitch.Pitchcatchesfirequickly.Anexperimentshowedthatpitchcouldbesetonfirebyaburningmirrorinseconds.Andoncethepitchwasburning,thefirewouldspreadtothewoodeveniftheshipwasmoving.Soaburningmirrorcouldhaveworkedquicklyenoughtobeaneffectiveweapon. Third,whybotherwithaburningmirrorinsteadofflamingarrows? arrowsandwouldhavebeenwatchingforthemandwerereadytoputoutthefirestheymightcause.Butyoucannotseetheburningraysfromamirror.Youjustseethemirror.Butthensuddenlyandmagicallyafirestartsatsomeunobservedplaceontheship.Thatwouldhavebeenmuchmoresurprisingandthereforemuoreeffectivethanaflamearrow.TPO40ManyscientistsbelieveitwouldbepossibletomaintainapermanenthumanpresenceonMarsortheMoon.Ontheotherhand,conditionsonVenusaresoextremeandinhospitablethatmaintainingahumanpresencetherewouldbeimpossible.First,atmosphericpressureatVenus’surfaceisatleast90timesgreaterthanthepressureatEarth’ssurface.Thismeansthataforceof100kilogramsispressingdownoneverysquarecentimeterofsurface.AllspacecraftthathavelandedonVenushavebeencrushedbythisextremepressurewithinanhouroflanding.AlmostanythinghumansmightlandonVenuswould

asSecond,asfarasweknow,therearenoreservoirsofwateronofcarbondioxide,nitrogen,andsulfuricacid,

thereforeprobablyhaveto dtoVenusfromTheideaofensuringaregularsupplyofwaterandfromEarth

intheextremeandwoulddefeatthepurposeofestablishingapermanentstationThird,verylittlesunlightreachestheplanet’ssurface.About60percentofthesunlightthathitsVenusisreflectedintospaceby

thick

thatfilltheatmosphere,meansthatonly40percentofthesunlightcangettheclouds.Belowthesecloudsisadenselayerofcarbondioxide,whichblocksevenmorelight,soverylittlelightreachesthesurface.Thelackoflightwouldpreventtheuseof powertheirmachinesandequipment.

ectricity TPO40SettingupapermanentstationonVenusmaynotbechallenges,butitiscertainlypossible.OnesolutionbeenproposedistoestablishastationthatwouldbefloatinginVenus'satmosphere,likeaballoon,ratherthanstandingonitssurface.Thestationwouldfloatabout50kilometersaboveVenus'ssurface.Onastationlocatedhighintheatmosphere,theproblemsthereadingmentionscanbeFirst,atmosphericpressure.Well,itisawell-knownphysicalfactthathighupintheatmosphere,thepressureismuchlowerthanatthesurface.SowhilethepressureatVenus'ssurfaceistoohighforhumans,50kilometersupintheatmosphere,thepressure'sequaltothenormalpressurewe'reusedtohereonEarth.Therewouldbenodangerofthestationgettingcrushed. Venus'satmospherecontainscompoundssuchascarbondioxideandsulfuricacid.Therearechemicalprocessesthatcouldbeused thesecompounds.SothewaterandoxygennecessaryforhumansurvivalcouldbeproducedusingchemicalmaterialsthatcanbeeasilyobtainedfromVenus'satmosphere.Itwouldnotnecessary

Third,thelightblockingclouds.Well,itistruethattherearestillclouds50kilometersaboveVenus'ssurface.However,cloudsabovethatlevelarenotverythick,sotherewouldbeaconsiderableamountofsunlightfilteringthrough.Moreover,atyouread,thecloudsreflectsunlight.Thestationcanmakeuseofthisreflectedlighttoo.Inotherwords,itssolar-poweredcellscouldcollectboththedirectsunlightfilteringfromaboveandthesunlightreflectedbythecloudsbelow.Morethanenoughelectricitycouldbegeneratedthiswaytopowerthestation.TPO47Pterosaurswereanancientgroupofwingedreptilesthatlivedalongsidethedinosaurs.Manypterosaurswereverylarge,someaslargeasagiraffeandwithawingspanofover12meters.Paleontologistshavelongwonderedwhetherlargepterosaurswerecapableofpoweredflight(flyingbyflaptheirwings)orwhethertheywereableonlytoglide.Severalargumentshavebeenmadeagainstpoweredflight.Doubterspointoutthatsincemodernreptilesarecold-blooded,ancientreptilessuchaspterosaurswereprobablycold-bloodedaswell.Cold-bloodedanimalstypicallyhaveaslowmetabolismandareunabletoproducealotofenergy.Poweredflightisanactivityrequiringalotofenergy,whichiswhyallmodernvertebratesthatflyarewarm-blooded,notcold-blooded.Itseemedunlikelythatpterosaurswouldhavebeenabletogeneratetheenergyneededtofly.Second,thereisalimittotheweightofanimalsthatcanbekeptairbornebypoweredflight.Pterosaursthatwereaslargeasagiraffewereprobablysoheavythattheywouldnothavebeenabletoflaptheirwingsfastenoughtostayaloftforanylengthoftime.Third,allanimalswithpoweredflightareabletotakeofftheground.For

takeoffby fromlegsorrunningtogainspeedandthenjum.Butthesemethodswouldnothaveworkedforlargepterosaurs.Largepterosaurswouldhaveneededbig,powerfulmusclesintheirbacklegstolaunchthemselvesintotheair,andweknowfromfossilizedbonesthattheirbacklegmusclesweretoosmallandweaktoallowthepterosaurstorunfastenoughorjumphighenoughtolaunchthemselvesintotheair.TPO47Recentresearchhasrevealedthepterosaursmayinfacthavebeencapableofpoweredflight.First,theissueofpterosaurmetabolism.Somerecentlydiscoveredpterosaurfossilsindicatethatpterosaurshadadense,hair-likecovering,somewhatsimilartofur.Hairorfurcoveringistypicalofwarm-bloodedanimalsbecausethoseanimalsneedtomaintainahighbodytemperaturewhenexternalconditionsarecold.Soifthemetabolismofpterosaurswasmorelikethatofwarm-bloodedanimalsandsofasterthanthereadingsuggests,th