走向未来TED英文字幕.docx
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走向未来TED英文字幕.docx
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走向未来TED英文字幕
Walktothefuture
Thedreamofbecomingacitizenofthecosmoswasbornhere,morethantwomillenniumagointhecityofAlexandria,namedafterandconceivedbyitsdeadconqueror,AlexandertheGreat.ThePtolemys,theGreekkings,whoinheritedtheEgyptianportionofAlexander’sempirebuiltthislibraryanditsassociatedresearchinstitution.Rarely,ifever,beforeorsince,hastherebeenagovernmentthatwaswillingtospendsomuchofitsnationalproductontheacquisitionofknowledge.Anditpaidoff.Bigtime.EveryshipenteringAlexander’harborwassearched--notforcontraband,butforbooksthatmightbecopiedandstoredhere,inwhatwasthenthegreatestlibraryonearth.Here,Eratosthenes,oneofthechieflibrarians,accuratelythesizeoftheearthandinventedgeography.Pythagoras.Hypatia.Euclid.Euclidsetforththepreceptsofgeometryinatextbookthatremainedinusefor2,300years.TheOldtestamentBiblecomesdowntousmainlyfromtheGreektranslationsmadehere.TheoriginalmanuscriptsofmasterpiecesofGreekcomedyanddrama,poetry,science,engineering,medicineandhistory-thetotalworkproductoftheawakeningofancientcivilization-werekepthere.Estimatesvaryonthetotalnumberofscrolls.Theyrangefrom500,000tonearlyamillion.Andallofit...allofthisisbutatinyfractionofinformationthatyouhaveatyourfingeratthisverymoment.Thecollectiveknowledgeofourspecies,ourownelectronicLibraryofAlexander,maybeaccessedbyanyonewhohasadeviceandtheinterestandthefreedomtodoso.ThiswasnottrueinAlexander,whereknowledgebelongedtoelite.SointhefourthcenturyAD,whenthemobcametodestroythelibraryandgeniusofclassicalcivilization,therewerenotenoughpeopletodefendit.Whatwillhappenthenexttimethemobcomes?
We’vecomealongwaytogether,travelingfromdeepinsidetheheartofanatom,clearouttothecosmichorizon,andfromthebeginningoftimetothedistantfuture.Ithinkwe‘rereadytoperformanexperiment.It’snotkindofexperimentthatrequiresalaboratory.Youcandoitinyourhead.It’scalleda“thoughtexperiment.”
Pickastar-anyoneofthehundredsofbillionofstarsinourMilkyWayGalaxy,whichisjustonegalaxyoutofthehundredsbillionintheknowuniverse.Howaboutthatstars?
Orthatone?
Okay,thisone.It’sorbitedbydozensofPlanetsandmoons.Suppose,ononeofthem,therelivesanintelligentspecies,oneoftenmillionlife-formonthatPlanets,andthere’sasubgroupofthatspecieswhobelievetheyhaveitallfigureout-theirworldisthecenteroftheuniverse,auniversemadeforthem,andtheyknoweverythingtheyneedtoknowaboutit-theirknowledgeiscomplete.Howseriouslywouldyoutaketheirclaim?
Ourancestorbelievedtheuniversewasmadeforthem.Itwasnaturaltoassumethatwewereatthecenter.Afterall,itlookslikethesunandstarsallrevolvearoundus.Westillspeakofthesun“rising”.Thearchitectureofourlanguage,mythsanddreamscomesfromthatpre-scientificage.Thisisourplanetasitwasknownthen,justbeforeColumbussetsail.Thisfirstglobeofearthwascutting-edgewhenMartinBehaimmadeitin1492.Likeeveryoneelse,hebelievedthatjigsawpuzzleofgeographywascomplete.Therewerethreecontinents...Europe,AfricaandAsia,andonlythegreatworldoceaninbetween.BehaimhadnocluethatNorthandSouthAmericaevenexisted.It’seasytofeelsmug,right?
Well,thefactisMartinBehaimknewinfinitelymoreabouthisworldtheearththanweknowaboutours,theuniverse.
Arecentlessoninhumilitywillservetoillustrate.In1912,VictorHessmadeaseriesofvoyagesintotheshyaboveAustria,andfoundthethingthatscientistslovebest...amysterythatdefiedunderstandingintermsofconventionalscientificwisdom.Andeventoday,acenturylater,wearestillsearchingforacompleteexplanationofwhatHessfound.Anewkindofenergyhadrecentlybeendiscovered,radioactivity.Itwasgivenoffbycertainelements,likeradium.Butitwasalsofoundintheair,evenfarawayfromradioactiverocks.Itwaseverywhere.Wheredidthisstrangeenergycomefrom?
Nooneknows.Hesssuspectedthatitmightcomefromabovetheearth.Totestthishypothesis,hecarriedradiationdetectorshighintothesky.Duringariskyascentinahydrogenballoon,heattainedanaltitudeofmorethanthreemiles.Whenhereachedthethin,cold,upperhalfoftheatmospere...Hefoundtheradiationwasmorethantwiceasstrongasontheground.Theradiationmustbecomingfromabove.That’swhyitsintensitywasweakerontheground-theEarth’satmospherewasabsorbingmostofit.Somethoughtthatradiationmightcomefromthesun.Totestthatidea,Hesstimedoneofhisascentstocoincidewithasolareclipse.Buttheeclipsehadnoeffectontheradiation.Hessalsofoundthattheradiationwasjustasstrongatnightasindaylight.Itwascomingfromabove,butnotfromtheSun.WhatHessdidnotknowwasthatthesolarwinddoesn’tmovethatquickly-cured.Andso,forthewrongreason,hecametotherightconclusion.Hesshaddiscoveredcosmicrays-showersofsubatomicparticlesthatcrisscrosstheuniverseatliterallythespeedoflight.WithouttheshieldingeffectofEarth’satmosphere,theywouldbelethal.Somecosmicrayscancarryasmuchasenergyasabulletfiresfromarifle.Itwouldtakedecadestotracecosmicraysbacktoadeathofunimaginableviolence.
ThecosmicraysthatVictorHessdetectedintheskiesaboveAustriaposedamysterytoscientists.Radioactivityinmineralonearth-likeuraniumore--comesfromthedisintegrationofatoms.Butcosmicrayswereofadifferentnature.TheywerefarmorepowerfulthananythingknowninHess’sworld.Scientistwonderedfortwodecadeswhatcouldpossiblyproducecosmicrays.EnterFritzZwicky,themostbrilliantmanyou’veneverheardof.In1933,heandacolleaguediscoveredthatsomestarsflareuptobecomeasbrightastheirentiregalaxyforafewweeks,beforefadingoutagain.FritzZwickywasthefirstpersontounderstandwhatjusthappened.Hecorrectlysurmisedthatthisisthewayamassivestardies--itblowsitsgutsoutintospace.Hecalledthiskindofstellardeatha“supernova”...andpredictedthatthedyingstarwouldshrinkfromamillionmilesacrosstoonlyten.ThiscorpsewouldbesodensethatasingleofitwouldweightasmuchastheGreatPyramidinEgypt.Itwouldconsistalmostentirelyofsubatomicparticlescalledneutrons,sohenamedthesebizarreobjects“neutronstars”.And35yearsafterZwickypredictedtheirexistence,astronomersbegantofindthem.Wecallthem“pulsars”whentheyspinrapidlyandemitregularpulsesofradioenergy.Supernovasandneutronstarscouldaccountforawiderangeofcosmicrays,butnotthemostenergeticones.Nothingyetknowntosciencecanexplainthem,andwe’refinewiththem.It’soneofthethingsIlovescience,wedon’thavetopretendwehavealltheanswers.Zwickyalsocameupwiththeideathatthegravityofagalaxywarpsthefabricofspacearoundit,toactlikealens.Thisdistortsandmagnifieslightfromanyothergalaxylyingdirectlybehindit.So,astronomersonEarthwouldseemultipleimagesofthatsamedistantgalaxy,deformed,asinafunhousemirror.40yearsafterthisprediction,westartedfindingthem,too.
AndZwickymadeyetanotherdiscoverybackin1930s.WhilestudyingtheComaClusterofgalaxies,henoticedsomethingfunnyaboutthewaytheymoved.Thegalaxiesweregoingwaytoofast,sofasttheyshould’vebeenflyingapartfromeachother,becauseallthestarinallthosegalaxieshadfartoolittlegravitytoholdtheclustertogether.Zwickythoughtthatsomethingelsemustbebindingthemtoeachother.Thatmysteriouscomponentwouldhavetoweightsomethinnglike50timesasmuchasthestarsthemselves.Butnoonepaidmuchattentiontothiswildnotion.JustanotheroneofZwicky’soneofcrazyideas.Inoursolarsystem,theinnermostplanet,Mercury,movemuchfasterthantheoutermostone,Neptune.Andthatmakessense,right?
Theharderyoupushorpullonsomething,thefasteritgoes.TheSun’sgravityweakenswithincreasingdistance,so,thePlanetsthatarefartherfromtheSunmovemoreslowly.Everyoneexpectedthattheoutermoststarinagalaxywouldactasthesameway.Mostofthestarareconcentratedtowardsthecenter,sotheircollectivegravitypullsontheotherstarthesamewaytheSunpullsonthePlanets.Butinthe1970s,whenastronomerVerandaRubinstudiedtheAndromedaGalaxy,shediscoveredthattheouterstarsobeyednosuchrule.UnliketheouterPlanetsofsolarsystem,theouterstarsinthegalaxywereallgoingatthesamespeedasthestarsthatwerecloserin,andtheymovingwayfasterthanexpected.“That’sfunny,”Verathought.“theremustbesomethingweirdabouttheAndromedaGalaxy”.Soshelookedanothergalaxy.Samestory.Andanother.Verandastudies60galaxiesandfoundthatallofthemseemedtobeviolatingthelawofGravity,acoreprincipleofphysics.Aftersomeinitialhealthyskepticism,hercolleagueslookedforthemselves,andfoundthatVerawasright.It’snotthatIsaacNewtonhadgottentheLawofGravitywrong;VerandaRubinhaddiscoveredthatthegravityofsomethingmassiveandinvisiblewasforcingstarstogofast.AndthensomeonerememberedcrazyoldFritzZwicky,andtheunknownsourceofgravityinthegalaxyclusterthathecalled“darkmatter”backin1933.VeraRubinhadverifiedtheexistenceofanew,muchlargercosmic.Andjustliketheonewethoughtweknew,itwasfilledwithmystery.Darkmatteriscompletelyunobservable,exceptforitsgravitationaleffect,whichmakesvisiblestarsandgalaxiesmovefaster.Itsnat
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