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1、41.Experiments tinsectsExperiments tinsectscanfunctionaspollinatorsofcycads,rare,palmliketropicalFurthermore, cycads removed from their native habisand therefore from insects native to those sareusuallyinfertile.Nevertheless,anecdotalreportsofwindpollinationincycadscannotbeignored.Thestructureofcyca

2、dsmaleconesisquiteconsistentwiththewinddispersalofpollen,cloudswhicharereleased41.Experiments tinsectsExperiments tinsectscanfunctionaspollinatorsofcycads,rare,palmliketropicalFurthermore, cycads removed from their native habisand therefore from insects native to those sareusuallyinfertile.Neverthel

3、ess,anecdotalreportsofwindpollinationincycadscannotbeignored.Thestructureofcycadsmaleconesisquiteconsistentwiththewinddispersalofpollen,cloudswhicharereleasedfromsomeofthelargercones.ThemaleconeofCycascircinalis,forle,almost100cubiccentimetersofpollen,mostofwhichisprobablydispersedbywind.Still,manym

4、alecycad cones are comparatively small and thus produce far less pollen. Furthermore, the structure of most female cycad cones seems inconsistent with direct pollination by wind. Onlyhe Cycas genus are the femalesovulessibletoairbornepollen,sincehisgenusaretherroundedbyalooseofmegasporophyllsnbyatig

5、ht实验表明，昆虫可以充科植物（cycad, 一种数量稀少的、类似棕榈树的热带植物）的传 者的角色。此外，从原栖息地迁出的铁树当然树上的昆虫也离开了它们的栖息地通常不结实。不过不能忽略有关铁树风力传粉的趣。铁树雄性球果的构造满足风力传粉的求，大量花粉从较大的球果上洒落下来。例如，Cycas circinalis 的雄性球果会散落约 100 平方厘米花粉，其中大部分花粉都很有可能随。尽管这样，许多雄性铁树球果相对较小，因此产生的粉也少。此外，大多数雌性铁树球果的结构看起来和风力传粉的要求不一致。只有卷属铁树的雌，而不是被紧密球果42.AlthoughthehormoneAlthoughtheho

6、rmoneadrenalineisknowntoregulatememorystorage,itdoesnotpassfromtheobraincells.Wearefacednapparentparadox:howcanatdoesnotactdirectlyonbrainhavesuchalargeeffectonbrain尽知道肾上腺素 adrenaline 能调力，但是肾上腺素并不从血液进入脑细胞。于是们遇到一个明显的悖论：一种并不直接作用于大脑的激素如何能对大脑的功能有如此巨大的影响Recently,wetestedtoneoftheionsoutsidetheightrespons

7、ible.Sinceoneconsequenceofadrenalinereleaseinananimalisanincreaseinbloodglucosexaminedtheeffectsofglucoseonmemoryinrats.Wetglucoseinjectedytrainingmemorytestedthenextday.Additionalevidencewasprovidedbynegativefindings:calledadrenergicantagonists,whichblockperipheraladrenalinereceptors,disruptedadren

8、alinesabilityregulatememorybutdidnotaffectmemoryenhancementsproducedbytwasnotstimulatedadrenaline.Theseresultsareastheyshouldbeifadrenalineaffectsmemorymodulationbyincreasingblood glucose levels.最近检验了其中一种大脑外激素活动调节有关的可能性。因为动肾上腺素的个结果是血液中葡萄糖含量增加，所测试了葡萄糖对老力的影响。发现，如果老在训练后马上注入葡萄糖，老鼠在第二天实验时力会提高。其他是由负向发现得到的

9、一种叫肾上腺素功能对抗剂 adrenergic antagonist 的药物，会阻碍体表肾上腺受体，扰乱肾上腺素调节忆的能力，但并不影响由非肾上腺素激发的葡萄糖引力的提高。如果肾上腺素是通过增加血中葡萄糖含量来影力的调节，那么其实验结果理应如此43.In prehistoric times InprehistorictimesbrachiopodswereoneofthemostabundantanddiverseformsoflifeonEarth:more n30,000speciesofthisclamlikecreaturehavebeencatalogedfromfossilreco

10、rds. Todaybrachiopodsarenotasnumerous,andexistingspeciesarenotwellstudied,partlybecauseneithertheanimalsfleshyenoritshasanylvalue.Moreover,incontrasttothegreaterdiversityofthespecies,they300knownsurvivingspeciesarerelativelyuniforminappearance. retedthisasattheanimalhasbeenunabletocompetesfullywithh

11、eevolutionary1(brachiopod30000 好的研究，一部分是notasnumerous,andexistingspeciesarenotwellstudied,partlybecauseneithertheanimalsfleshyenoritshasanylvalue.Moreover,incontrasttothegreaterdiversityofthespecies,they300knownsurvivingspeciesarerelativelyuniforminappearance. retedthisasattheanimalhasbeenunabletoco

12、mpetesfullywithheevolutionary1(brachiopod30000 好的研究，一部分是因为动物的内在肉状组织和它们的壳没。此外，和大的物种同的是，已知存活的大约 300 种物种在外观上相对单一。许多动物学家把这作为一个腕足动物无法在中战胜其他海洋生物的信号Severalthings,however,ttheconventionalviewneedsrevising.Forle,Lingulahasanunbrokenfossilrecordernhalfabillionyearstothepresent.Thus,if anisms extant. Further,

13、recent studieslongevityisanymeasure,brachiopodsarethemosttdiversityamongspeciesisalessimportantmeasureofevolutionarysnistheabilitywithstandenvironmentalchange,suchaswhenalayerofclaysandontheoceanbottom.relativelygreateruniformityamongtheexistingbrachiopodspeciesmayofferrotectionenvironmentalchangean

14、dhencemayreflecthighlysfuladaptive然而，有几件事情表明这个传统的观点需要修正。例如，舌形贝属腕足动物(Lingula)有从 5 多年前延续到现在的、不间。因此，如果长期生存是物种是否成功的标准的话足动物是现存最成功的物种。另外，最近的研究表明，物种的多样性与其承受类似海底泥土取代沙的环境变化的能力相比，不是那么重要。在现存腕足动物中，相对较高性也许能针对环境变对其提供更强的保护，因而这性可能展现成功适应环境的行为Theadaptiveadvantagesofuniformityforbrachiopodscanbeseenbyconsideringlizati

15、on,stoccursasaresultofprolongedcolonizationofauniformsubstrate.tcansurvivemanyarecalledgeneralists,whiletcansurviveonalimitedrangeofsubstratesarelists.Onelistspecies,forle,hasvalvesweightedatthebase,attanismisitionedforudandsimilarsubstrates;otherspeciessecreteallowingthemtosurviveonthefaceofunderwa

16、tercliffs.Thefossilrecordtbrachiopodlineageshavefollowedatrendtowardincreasedlization.However,duringperiodsenvironmentalinstability,whenaparticularsubstratetowhichalistspecieshasadaptedisnoavailable, the species quickly dies out. Generalists, on the other hand, are not dependent on a particular subs

17、trate, and are thus less vulnerable to environmental change. One study of the fossil record revealed a mass extinction of brachiopods following a change in sedimenionfromchalktoclay.Ofthe35brachiopodspecieshechalk,only6heclay,allofthem考虑到腕足动物长在单一海底底层而导致的特化lization)过程就可以看出它的一致性适应优势。那些可以在多种地表上生存的物种叫普适

18、性物种 generalists ，而那些只能在海底部有限区域内的物种叫做特定性物种 list)。例如，一个特定性物种在其底部有用来加大重量瓣膜，这个特征保证生物体粘在泥土以及相似海底底层上适当的位置，以满足其取食的要求；其它物粘液，这些粘液把它们粘在水下峭壁上使其生存下去。化显示出，大多数腕足动遵循特定的特化方向。然而，在环境不稳定的时期，即特定性生物已经适应的某块海底底部时，这些生物很快么脆弱。一个有关化。，普适性物种不依赖于某一种海底底部，因此它们对于环境变化不的研究显示，海底沉积物由白垩变为泥土之后，大量腕足动。在白垩中发现的 个腕足物种中，只有 种在泥土中存活，且存活的都是普适性物As

19、longasenoughgeneralistspeciesareained,andstudiesofarcticandsubarctictgeneralistsareoftendominantmembersofthemarinecommunitiesthere,itseemsunlikely close to extinction.tthephylum只要有足够多的普适性物种，并且北冰洋和亚北冰洋表明普适性物种是那里海洋群落的主员，那么腕足门动物看起来不太可能濒。44.UpwardsofabillionstarsinUpwardsofabillionstarsinourgalaxyhavebu

20、rntupernalenergy,andsocannoproducetheheatastarneedstoop masses, evolve, in general, muetheinwardforceofgravity.Thesestars,ofnafeworendoesastarliketheSun.Moreover,itisjustthesemassivestarswhosecollapsedoeslermediatestagestis,aswhite44.UpwardsofabillionstarsinUpwardsofabillionstarsinourgalaxyhaveburnt

21、upernalenergy,andsocannoproducetheheatastarneedstoop masses, evolve, in general, muetheinwardforceofgravity.Thesestars,ofnafeworendoesastarliketheSun.Moreover,itisjustthesemassivestarswhosecollapsedoeslermediatestagestis,aswhitedwarfsorneutronInstead,thecollapsecontinuesuntilasingularity(anydensecon

22、centrationofmatter)is的星系中有 亿多个星球已经燃尽的能源，并且再也不能发出对抗重力所需的热能。这些质量相当于的星球的演化速度，一般这样的星球要快得多。而且只这些质量大得多的星球的坍塌过程并不在中间阶段暂停（例如白矮星或中子星那样）。相反，这种坍（Itwouldbewonderfultoobserveasingularityandobtaindirectevidenceoftheundoubtedlytoccurnearone.ostcasesadistantobservercannotseetheoutgoinglightraysaredraggedbackbygravi

23、tysoteveniftheycouldstartoutwithinakilometersofthesingularity,theywouldendhesingularity如果能观察这个奇点并在附近直接体验到这个的确奇异的现象，是再好不过的。不幸的是，在绝大多数情况下，一个远距离观察者看不到这个奇点，因为发射出来的光线被重力吸引得过于强烈，以至于45.ThedarkheThedarkhestarrynightskyarenothetaredevoidofstarsaslongbeenthought.Rather,theyaredarkbecauselarthidesthestarsbehin

24、dit.itsvisualeffectissopronounced,dustisonlyaminorconstituentofthematerial,extremelylowintsnthestars.Dustaccountsforaboutonepercentofthetotalmasslarmatter.Therest lar material, rather likeishydrogenandheliumgas,withsmallamountsofotherelements.terrestrialclouds,comesinallsandsizes.Theaveragedensityla

25、rhevicinityourSunis1,000to10,000timesnthebestterrestriallaboratoryvacuum.Itisonlybecauseoflartsolittlematerialperunitofessosignificant. astronomyismostdirectlyaffected,forlargasisperfectlytransparent,thedustis繁星夜空中区并非如长期以来人们认为的那样是没有星球的。相反区的原因是元素。星际物质有点像地球上的云，有各种形状和大小。附近星际物质的平均密度是地球上验室中最佳真空的千分之一到万分之一

26、。只是由于巨大的星际距离使体积中如此稀少的物质46.ThetransferofheatandThetransferofheatandwatervaporfromtheoceantotheairaboveitdependsonadisequilibriumaterfaceofthewaterandtheair.Withinaboutamillimeterofthewater,airtemperatureisclosetofsurfacewater,andtheairisnearlysaturatedwithwatervapor.Butthe,howeversmall,areandthediseq

27、uilibriumisainedbyairnearthesurfacemixingirhigherup,whichisblycoolerandlowerinwater-vaporcontent.Theairismixedbymeansoftonthewindforergy.Aswindspeedincreases,sodoesturbulence,andthustherateofheatmoisturetransfer.Detailedunderstandingofthisphenomenonawaitsfurtherstudy.eractingcomplicatingphenomenonis

28、wind-to-watertransferoftoccurswhenwavesareWhenthewindmakeswaves,ittransfersimportantamountsofenergyenergy to provide turbulence.tisthereforenot热量和水蒸气从海洋向海洋上方的空气中进行转移，这个过程依赖于水面和空气之间的一种失 disequilibrium 。在水面上约一毫米的范围内，气温接近表层水的温度，而空气中的水蒸气也趋于和。但是，这两方面的差异无论多小，并且这种失衡可以维持下去是由于贴近水面的空（WUXOHFHrogrammers热量和水蒸气从海

29、洋向海洋上方的空气中进行转移，这个过程依赖于水面和空气之间的一种失 disequilibrium 。在水面上约一毫米的范围内，气温接近表层水的温度，而空气中的水蒸气也趋于和。但是，这两方面的差异无论多小，并且这种失衡可以维持下去是由于贴近水面的空（WUXOHFHrogrammers often rogrammersoftentcomputingmachines,perfectlackofwilldoanyfoolishthingtheyaretoldtodo.Thereasonfors,ofhenarrowfixationofcomputingmachineselligence”onthede

30、tailsofitsownperceptionsitsinabilitytobeguidedbyanycontext.Inapsychologicaldescriptionoftheelligence,threerelatedadjectivescometosingle-minded,literal-minded,andsimpleminded.Recognizingthis,weshouldatthesametimerecognize t this single-mindedness, literal-mindedness, and simplemindedness also charact

31、erizes theoreticalmathematics,thoughtoalesser电脑程序员常常说，由于计算机器缺乏完美的鉴别力，只让它做，它就会做任何傻事。当然，这么说的原因在于计算机器的“智能”被狭隘地固定在它所感知的细节上它不能被更大的环引导。在计算机智能的心理学描述中，三个相关的形容词进的脑海：思维专一的、思维同时也应该认识到这种专一、精确以及简单的思维数ciencetriestodealwithreality,eventhemostprecisenormallyworkwithmoreorless ain an appropriate skepticism.ttheSchro

32、dingerequationforimperfectlyunderstoodapproximationstowardwhichscientistsmustThus,forinstance,itmaycomeasashocktonstohydrogenatomisnotaliterallycorrectdescriptionofthisatom,butonlyanapproximationtoasomewhatcorrectequationtakingaccountofspin,magneticdipole,andrelativisticeffects;tthiscorrectedis itse

33、lf only an imperfect approximation to an infinite set of quantum field-theoretical equations. Physicists, lookingattheoriginalSchrodingerequation,learntosenseinitthepresenceofmanyinvisibletermsinaddition to thedifferential termsvisible,and thissenseinspiresan entirely appropriatedisregard forthepure

34、ly technical features of the equation. This very healthy skepticism is foreign to the mathematical approach.既然科学尝试去处理现实问题，那么即使是最精确的科学通常也会借助或多或少不精确的近似进行工作，科学家必须对这种近似保持适当的怀疑态度。例如，可能会让数学家们感的是，原子的 6FKURGLQJHU 方程并不是对原子精确描述，它只是对考虑到自旋、磁偶极子以及相对论效应的确方程的某种近似；他们还可能感的是，这种精确的方程本身也只是一种对于无限量子场 理论6KURLQJUMathematic

35、smustdealwithwell-definedsituations.Thus,nsdependoneffortoutsideofmathematicsforthelspecificationofthetmathematicsistoliterally.Givensatistheleastbitill-defined,andtheywillmakeitwell-perhapsy,butperhapsy.Insomecases,thensliteral-mayhaveunfortunate.Thensturnthescientiststheoreticalttheirconvenientsyt

36、icaloaxioms,andthentaketheseaxiomsliterally.Thisthettheymayalsopersuadethescientiststotaketheseaxiomsliterally.Thequestion,centralthescientificinvestigationbut relaxed?is thereby ignored.enselyhe mathematical contextppensiftheaxioms数学必须处理明确规定的情况。因此，数学家们依靠数学以外的知识来详细说明他们按照字面理解的近似性。给予数学家一个尽可能确切的情景，他们就会

37、把情景变成完全确切的场景，这个变化数学家把科学家做出的理论假设，即为了需要而分析强调的论点，变成公理，然后再照字面含义理解公理。这就会带来风险，即他们可能劝说科学家也照字面理解这些公理。因此，如果公理不严谨而产就被忽略了，而这个问题是一个对于科学研、但对于数学领域极其烦。Thephysicistrightlydreadspreciseargument,sinceantisconvincingonlyifitislosesallitsforceifthemptionsonwhichitisbasedareslightlychanged,whereasantconvincingthoughimpr

38、ecisemaywellbestableundersmallperturbations数学必须处理明确规定的情况。因此，数学家们依靠数学以外的知识来详细说明他们按照字面理解的近似性。给予数学家一个尽可能确切的情景，他们就会把情景变成完全确切的场景，这个变化数学家把科学家做出的理论假设，即为了需要而分析强调的论点，变成公理，然后再照字面含义理解公理。这就会带来风险，即他们可能劝说科学家也照字面理解这些公理。因此，如果公理不严谨而产就被忽略了，而这个问题是一个对于科学研、但对于数学领域极其烦。Thephysicistrightlydreadspreciseargument,sinceantisco

39、nvincingonlyifitislosesallitsforceifthemptionsonwhichitisbasedareslightlychanged,whereasantconvincingthoughimprecisemaywellbestableundersmallperturbationsofitsunderlying物理学家敬畏精确论断的做法是正确的，因为一个只有在精确情况下才有说服力的论断在其假设条件稍微改变时就会失去全部说服力，而一个不精确但却有说服力的论断，在其基本假设受到微扰时，48.ThedeterminationoftheThedeterminationofth

40、eofcopperorehemanufactureofcopperandbronzeartifactsBronzeAgecivilizationswouldaddytoourknowledgeofculturalcontactsandhatResearchers yzedartifactsandoresfortheirconcentrationsofelements,butforavarietyofthesestudieshavegenerallyfailedtoprovideevidenceoftheofthecopperheElemental com otherelements,espei

41、tioncanvaryhesamecopper-orelode,usuallybecauseofvaryingadmixturesllyiron,lead,zinc,andarsenic.Andhighconcentrationsofcobaltorzinc,noticedsomeartifacts,appearinavarietyofcopper-ore.Moreover,thesingofroducedcontrolledheconcentrationsofminorandtraceheresultingmetal.Someevaporateduringsmeltingandroastin

42、g;differenttemperaturesandsesproducedifferentdegreesofFinally,flux,whichissometimesaddedduringsmeltingtoremovewastematerialfromtheore,couldadd ties of elements to the final product.确定用于制造青铜时代文明国家铜器和青铜器的铜矿石来源，会大大们对于那个时代文交流和贸易往来的了解。研究者们分析了铜制品和铜矿石中铜的含量，但是由于种未能为制品中铜的产地提。通常是由于不同程度混合其他元素，特别是铁、中各种组成成分在同一矿藏

43、中可能会有差异。并且在一些制品中发现的高浓度钴和锌可能来源于许多产地。此外，矿石的加工会使生产出的金属中的次要和微量元素的含量发生变化，而这种变化不能很最后，为了在熔解过程中从矿石中去除废料而加入的助熔剂会给最终产物增加大量元Anelementaltisunchangedthroughthesechemicalsesistheisotopicitionetallicheore.Isotopicition,thepercentagesofthedifferentisotopesofaninagivenleoftheelement,isthereforeparticularlysuitableas

44、anindicatoroftheoftheore.course,forthiseitissarytofindanelementwhoseisotopicitionismoreorlessconstant east,fromonethroughoutagivenorebody,butvariesfromonecopperorebodytoanotheror, region to another.在这些化学处理过程中不变的元素性质就是矿石中每个金属元素的同位。是一种元素的不同同位素在给定样品中的百分比，因此它尤其适合作为矿石产地的指示物。当然，为达到需要找到一个元素，这个元素的同位在给定的矿体中几

45、乎是恒定的，但它在同矿体之间是不同的，或者至少在不同地理区域中是不同的Theidealchoice,whenisotopicitionisusedtoinvestigatethesourceofcopperore,wouldtobecopperitself.sbeentsmallbutmeasurablevariationsoccurhelesofitionofcopper.However,thevariationsarelargeenoughonlyinrareores;ncommonoremineralsofcopper,isotopicvariationsnthemeasuremente

46、rrorhavenotbeenternativechoiceislead,whichostcopperandbronzeartifactsoftheBronzeAgeinconsistentwiththeleadbeingderivedfromthecopperoressiblyfromthefluxes. Theitionofleadoftenvariesfromonesourceofcommoncopperoretoanother,withvariationsthemeasurementerror;andpreliminarystudiesindicatevirtuallyuniformi

47、sotopicitionoftheleadasinglecopper-oresource.Whilesomeoftheleadfoundinanartifactmayhaveroducedfromorwhenothermetalswereaddedtothecopperitionofleadoftenvariesfromonesourceofcommoncopperoretoanother,withvariationsthemeasurementerror;andpreliminarystudiesindicatevirtuallyuniformisotopicitionoftheleadas

48、inglecopper-oresource.Whilesomeoftheleadfoundinanartifactmayhaveroducedfromorwhenothermetalswereaddedtothecopperore,leadsoaddedinBronzeAgesingwouldusuallythesameisotopicitionasthehecopperore.LeadisotopestudiesmaythusproveusefulretingthearchaeologicalrecordoftheBronze当利用同位素来检查铜矿产地的时候，理想的选择似乎是铜自身的同位素。

49、事实表明，铜的位在天然状态下有微小但可以探测到的变化。，只有在稀有矿石中这些变化才足够大；普通铜矿石的样本中，人们还没有发现大于测量误差的同位变化。另一种选择是铅元素，它现在大多数青铜时代的铜制品或青铜制品中，含量与从铜矿石以及助熔剂中取得铅的含量一致。铅同位通常随铜矿石常见产地的不同而不同，这个波动超过了测量误差；并且初个铜矿石产地铅的同位素组成实际上是相同的。虽然在制品中发现的铅是助熔剂引铜矿石的金属，但在青铜时代加工过程中加入的铅与铜矿石中的铅有相同。因此，有铅同位素的研究对于解读青铜时代的考大有帮助49.Classical physics defines the Classicalph

50、ysicsdefinesthevacuumasaeofabsence:avacuumissaidtoexistinaregionofifthereisnothinginit.hequantumfieldtdescribethephysicsofelementaryparticles,essomewhatmorecomplicated.Eveninemptyspace,particlescanappearspontaneouslyasresultoffluctuationsofthevacuum.Forle,anelectronanditron,orantielectron,canbeoutof

51、thevoid.Particleshiswayhaveonlyafleetingexistence;theyareannihilatedalmostsoon as they appear, and their presence can never be detected directly. They are called virtual particles in order to distinguish them from real particles, whose lifetimes are not constrainedhesameway,andwhichcanbedetected.Thu

52、sitissibletotvacuumasasnorealparticlesinvauu 为了和实物粒子进行区分，它们被称为虚粒子 virtual particles ，实粒子并不像虚粒子一样受限制，而实粒子可以被检测到。因此可以把真空定义为没有实粒子的空间Onemighttthevacuumwouldalwaysbetheeofsibleenergyforaregionofspace.Ifanareaisinitiallyemptyandarealparticleisoit,thetotalenergy,itseems,beraisedeasttheenergyequivalentofthe

53、massoftheaddedparticle.Asurprisingresultofrecenttheoreticalinvestigationstthismptionisnotinvariablytrue.ThereareconditionswhichroductionofarealparticleoffiniteoanemptyregionofspacecanreducethetotalIfthereductioninenergyisgreatenough,anelectronanditronwillbespontaneouslycreated.theseconditionstheelectronitronarenotaresultofvacuumfluctuationsbutarerealparticles,existyandcanbedetected.Inotherwords,undertheseconditionsthevacuumisanunstableandcanoaeoflowerenergy;i.e.,oneinwhichrealparticlesare人们可能会认为，真空是在一片给定区域空间内具有最低能量的状态。如果一片区域初始是的把一个实粒子放入其中，总能量应该至少增加了那个被加入粒子的能量。近期的一些理论究的结果令人吃惊：上述假设不一定总是正确。某些情况下