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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實(shí)驗(yàn)表明，昆蟲可以充科植物（cycad, 一種數(shù)量稀少的、類似棕櫚樹的熱帶植物）的傳 者的角色。此外，從原棲息地遷出的鐵樹當(dāng)然樹上的昆蟲也離開了它們的棲息地通常不結(jié)實(shí)。不過不能忽略有關(guān)鐵樹風(fēng)力傳粉的趣。鐵樹雄性球果的構(gòu)造滿足風(fēng)力傳粉的求，大量花粉從較大的球果上灑落下來。例如，Cycas circinalis 的雄性球果會(huì)散落約 100 平方厘米花粉，其中大部分花粉都很有可能隨。盡管這樣，許多雄性鐵樹球果相對(duì)較小，因此產(chǎn)生的粉也少。此外，大多數(shù)雌性鐵樹球果的結(jié)構(gòu)看起來和風(fēng)力傳粉的要求不一致。只有卷屬鐵樹的雌，而不是被緊密球果42.AlthoughthehormoneAlthoughtheho

6、rmoneadrenalineisknowntoregulatememorystorage,itdoesnotpassfromtheobraincells.Wearefacednapparentparadox:howcanatdoesnotactdirectlyonbrainhavesuchalargeeffectonbrain盡知道腎上腺素 adrenaline 能調(diào)力，但是腎上腺素并不從血液進(jìn)入腦細(xì)胞。于是們遇到一個(gè)明顯的悖論：一種并不直接作用于大腦的激素如何能對(duì)大腦的功能有如此巨大的影響Recently,wetestedtoneoftheionsoutsidetheightrespons

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

8、alinesabilityregulatememorybutdidnotaffectmemoryenhancementsproducedbytwasnotstimulatedadrenaline.Theseresultsareastheyshouldbeifadrenalineaffectsmemorymodulationbyincreasingblood glucose levels.最近檢驗(yàn)了其中一種大腦外激素活動(dòng)調(diào)節(jié)有關(guān)的可能性。因?yàn)閯?dòng)腎上腺素的個(gè)結(jié)果是血液中葡萄糖含量增加，所測試了葡萄糖對(duì)老力的影響。發(fā)現(xiàn)，如果老在訓(xùn)練后馬上注入葡萄糖，老鼠在第二天實(shí)驗(yàn)時(shí)力會(huì)提高。其他是由負(fù)向發(fā)現(xiàn)得到的

9、一種叫腎上腺素功能對(duì)抗劑 adrenergic antagonist 的藥物，會(huì)阻礙體表腎上腺受體，擾亂腎上腺素調(diào)節(jié)憶的能力，但并不影響由非腎上腺素激發(fā)的葡萄糖引力的提高。如果腎上腺素是通過增加血中葡萄糖含量來影力的調(diào)節(jié)，那么其實(shí)驗(yàn)結(jié)果理應(yīng)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?yàn)閯?dòng)物的內(nèi)在肉狀組織和它們的殼沒。此外，和大的物種同的是，已知存活的大約 300 種物種在外觀上相對(duì)單一。許多動(dòng)物學(xué)家把這作為一個(gè)腕足動(dòng)物無法在中戰(zhàn)勝其他海洋生物的信號(hào)Severalthings,however,ttheconventionalviewneedsrevising.Forle,Lingulahasanunbrokenfossilrecordernhalfabillionyearstothepresent.Thus,if anisms extant. Further,

13、recent studieslongevityisanymeasure,brachiopodsarethemosttdiversityamongspeciesisalessimportantmeasureofevolutionarysnistheabilitywithstandenvironmentalchange,suchaswhenalayerofclaysandontheoceanbottom.relativelygreateruniformityamongtheexistingbrachiopodspeciesmayofferrotectionenvironmentalchangean

14、dhencemayreflecthighlysfuladaptive然而，有幾件事情表明這個(gè)傳統(tǒng)的觀點(diǎn)需要修正。例如，舌形貝屬腕足動(dòng)物(Lingula)有從 5 多年前延續(xù)到現(xiàn)在的、不間。因此，如果長期生存是物種是否成功的標(biāo)準(zhǔn)的話足動(dòng)物是現(xiàn)存最成功的物種。另外，最近的研究表明，物種的多樣性與其承受類似海底泥土取代沙的環(huán)境變化的能力相比，不是那么重要。在現(xiàn)存腕足動(dòng)物中，相對(duì)較高性也許能針對(duì)環(huán)境變對(duì)其提供更強(qiáng)的保護(hù)，因而這性可能展現(xiàn)成功適應(yīng)環(huán)境的行為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考慮到腕足動(dòng)物長在單一海底底層而導(dǎo)致的特化lization)過程就可以看出它的一致性適應(yīng)優(yōu)勢。那些可以在多種地表上生存的物種叫普適

18、性物種 generalists ，而那些只能在海底部有限區(qū)域內(nèi)的物種叫做特定性物種 list)。例如，一個(gè)特定性物種在其底部有用來加大重量瓣膜，這個(gè)特征保證生物體粘在泥土以及相似海底底層上適當(dāng)?shù)奈恢?，以滿足其取食的要求；其它物粘液，這些粘液把它們粘在水下峭壁上使其生存下去。化顯示出，大多數(shù)腕足動(dòng)遵循特定的特化方向。然而，在環(huán)境不穩(wěn)定的時(shí)期，即特定性生物已經(jīng)適應(yīng)的某塊海底底部時(shí)，這些生物很快么脆弱。一個(gè)有關(guān)化。，普適性物種不依賴于某一種海底底部，因此它們對(duì)于環(huán)境變化不的研究顯示，海底沉積物由白堊變?yōu)槟嗤林?，大量腕足?dòng)。在白堊中發(fā)現(xiàn)的 個(gè)腕足物種中，只有 種在泥土中存活，且存活的都是普適性物As

19、longasenoughgeneralistspeciesareained,andstudiesofarcticandsubarctictgeneralistsareoftendominantmembersofthemarinecommunitiesthere,itseemsunlikely close to extinction.tthephylum只要有足夠多的普適性物種，并且北冰洋和亞北冰洋表明普適性物種是那里海洋群落的主員，那么腕足門動(dòng)物看起來不太可能瀕。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 億多個(gè)星球已經(jīng)燃盡的能源，并且再也不能發(fā)出對(duì)抗重力所需的熱能。這些質(zhì)量相當(dāng)于的星球的演化速度，一般這樣的星球要快得多。而且只這些質(zhì)量大得多的星球的坍塌過程并不在中間階段暫停（例如白矮星或中子星那樣）。相反，這種坍（Itwouldbewonderfultoobserveasingularityandobtaindirectevidenceoftheundoubtedlytoccurnearone.ostcasesadistantobservercannotseetheoutgoinglightraysaredraggedbackbygravi

23、tysoteveniftheycouldstartoutwithinakilometersofthesingularity,theywouldendhesingularity如果能觀察這個(gè)奇點(diǎn)并在附近直接體驗(yàn)到這個(gè)的確奇異的現(xiàn)象，是再好不過的。不幸的是，在絕大多數(shù)情況下，一個(gè)遠(yuǎn)距離觀察者看不到這個(gè)奇點(diǎn)，因?yàn)榘l(fā)射出來的光線被重力吸引得過于強(qiáng)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繁星夜空中區(qū)并非如長期以來人們認(rèn)為的那樣是沒有星球的。相反區(qū)的原因是元素。星際物質(zhì)有點(diǎn)像地球上的云，有各種形狀和大小。附近星際物質(zhì)的平均密度是地球上驗(yàn)室中最佳真空的千分之一到萬分之一

26、。只是由于巨大的星際距離使體積中如此稀少的物質(zhì)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熱量和水蒸氣從海洋向海洋上方的空氣中進(jìn)行轉(zhuǎn)移，這個(gè)過程依賴于水面和空氣之間的一種失 disequilibrium 。在水面上約一毫米的范圍內(nèi)，氣溫接近表層水的溫度，而空氣中的水蒸氣也趨于和。但是，這兩方面的差異無論多小，并且這種失衡可以維持下去是由于貼近水面的空（WUXOHFHrogrammers熱量和水蒸氣從海

29、洋向海洋上方的空氣中進(jìn)行轉(zhuǎn)移，這個(gè)過程依賴于水面和空氣之間的一種失 disequilibrium 。在水面上約一毫米的范圍內(nèi)，氣溫接近表層水的溫度，而空氣中的水蒸氣也趨于和。但是，這兩方面的差異無論多小，并且這種失衡可以維持下去是由于貼近水面的空（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電腦程序員常常說，由于計(jì)算機(jī)器缺乏完美的鑒別力，只讓它做，它就會(huì)做任何傻事。當(dāng)然，這么說的原因在于計(jì)算機(jī)器的“智能”被狹隘地固定在它所感知的細(xì)節(jié)上它不能被更大的環(huán)引導(dǎo)。在計(jì)算機(jī)智能的心理學(xué)描述中，三個(gè)相關(guān)的形容詞進(jìn)的腦海：思維專一的、思維同時(shí)也應(yīng)該認(rèn)識(shí)到這種專一、精確以及簡單的思維數(shù)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.既然科學(xué)嘗試去處理現(xiàn)實(shí)問題，那么即使是最精確的科學(xué)通常也會(huì)借助或多或少不精確的近似進(jìn)行工作，科學(xué)家必須對(duì)這種近似保持適當(dāng)?shù)膽岩蓱B(tài)度。例如，可能會(huì)讓數(shù)學(xué)家們感的是，原子的 6FKURGLQJHU 方程并不是對(duì)原子精確描述，它只是對(duì)考慮到自旋、磁偶極子以及相對(duì)論效應(yīng)的確方程的某種近似；他們還可能感的是，這種精確的方程本身也只是一種對(duì)于無限量子場 理論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數(shù)學(xué)必須處理明確規(guī)定的情況。因此，數(shù)學(xué)家們依靠數(shù)學(xué)以外的知識(shí)來詳細(xì)說明他們按照字面理解的近似性。給予數(shù)學(xué)家一個(gè)盡可能確切的情景，他們就會(huì)

37、把情景變成完全確切的場景，這個(gè)變化數(shù)學(xué)家把科學(xué)家做出的理論假設(shè)，即為了需要而分析強(qiáng)調(diào)的論點(diǎn)，變成公理，然后再照字面含義理解公理。這就會(huì)帶來風(fēng)險(xiǎn)，即他們可能勸說科學(xué)家也照字面理解這些公理。因此，如果公理不嚴(yán)謹(jǐn)而產(chǎn)就被忽略了，而這個(gè)問題是一個(gè)對(duì)于科學(xué)研、但對(duì)于數(shù)學(xué)領(lǐng)域極其煩。Thephysicistrightlydreadspreciseargument,sinceantisconvincingonlyifitislosesallitsforceifthemptionsonwhichitisbasedareslightlychanged,whereasantconvincingthoughimpr

38、ecisemaywellbestableundersmallperturbations數(shù)學(xué)必須處理明確規(guī)定的情況。因此，數(shù)學(xué)家們依靠數(shù)學(xué)以外的知識(shí)來詳細(xì)說明他們按照字面理解的近似性。給予數(shù)學(xué)家一個(gè)盡可能確切的情景，他們就會(huì)把情景變成完全確切的場景，這個(gè)變化數(shù)學(xué)家把科學(xué)家做出的理論假設(shè)，即為了需要而分析強(qiáng)調(diào)的論點(diǎn)，變成公理，然后再照字面含義理解公理。這就會(huì)帶來風(fēng)險(xiǎn)，即他們可能勸說科學(xué)家也照字面理解這些公理。因此，如果公理不嚴(yán)謹(jǐn)而產(chǎn)就被忽略了，而這個(gè)問題是一個(gè)對(duì)于科學(xué)研、但對(duì)于數(shù)學(xué)領(lǐng)域極其煩。Thephysicistrightlydreadspreciseargument,sinceantisco

39、nvincingonlyifitislosesallitsforceifthemptionsonwhichitisbasedareslightlychanged,whereasantconvincingthoughimprecisemaywellbestableundersmallperturbationsofitsunderlying物理學(xué)家敬畏精確論斷的做法是正確的，因?yàn)橐粋€(gè)只有在精確情況下才有說服力的論斷在其假設(shè)條件稍微改變時(shí)就會(huì)失去全部說服力，而一個(gè)不精確但卻有說服力的論斷，在其基本假設(shè)受到微擾時(shí)，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.確定用于制造青銅時(shí)代文明國家銅器和青銅器的銅礦石來源，會(huì)大大們對(duì)于那個(gè)時(shí)代文交流和貿(mào)易往來的了解。研究者們分析了銅制品和銅礦石中銅的含量，但是由于種未能為制品中銅的產(chǎn)地提。通常是由于不同程度混合其他元素，特別是鐵、中各種組成成分在同一礦藏

43、中可能會(huì)有差異。并且在一些制品中發(fā)現(xiàn)的高濃度鈷和鋅可能來源于許多產(chǎn)地。此外，礦石的加工會(huì)使生產(chǎn)出的金屬中的次要和微量元素的含量發(fā)生變化，而這種變化不能很最后，為了在熔解過程中從礦石中去除廢料而加入的助熔劑會(huì)給最終產(chǎn)物增加大量元Anelementaltisunchangedthroughthesechemicalsesistheisotopicitionetallicheore.Isotopicition,thepercentagesofthedifferentisotopesofaninagivenleoftheelement,isthereforeparticularlysuitableas

44、anindicatoroftheoftheore.course,forthiseitissarytofindanelementwhoseisotopicitionismoreorlessconstant east,fromonethroughoutagivenorebody,butvariesfromonecopperorebodytoanotheror, region to another.在這些化學(xué)處理過程中不變的元素性質(zhì)就是礦石中每個(gè)金屬元素的同位。是一種元素的不同同位素在給定樣品中的百分比，因此它尤其適合作為礦石產(chǎn)地的指示物。當(dāng)然，為達(dá)到需要找到一個(gè)元素，這個(gè)元素的同位在給定的礦體中幾

45、乎是恒定的，但它在同礦體之間是不同的，或者至少在不同地理區(qū)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當(dāng)利用同位素來檢查銅礦產(chǎn)地的時(shí)候，理想的選擇似乎是銅自身的同位素。

49、事實(shí)表明，銅的位在天然狀態(tài)下有微小但可以探測到的變化。，只有在稀有礦石中這些變化才足夠大；普通銅礦石的樣本中，人們還沒有發(fā)現(xiàn)大于測量誤差的同位變化。另一種選擇是鉛元素，它現(xiàn)在大多數(shù)青銅時(shí)代的銅制品或青銅制品中，含量與從銅礦石以及助熔劑中取得鉛的含量一致。鉛同位通常隨銅礦石常見產(chǎn)地的不同而不同，這個(gè)波動(dòng)超過了測量誤差；并且初個(gè)銅礦石產(chǎn)地鉛的同位素組成實(shí)際上是相同的。雖然在制品中發(fā)現(xiàn)的鉛是助熔劑引銅礦石的金屬，但在青銅時(shí)代加工過程中加入的鉛與銅礦石中的鉛有相同。因此，有鉛同位素的研究對(duì)于解讀青銅時(shí)代的考大有幫助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 為了和實(shí)物粒子進(jìn)行區(qū)分，它們被稱為虛粒子 virtual particles ，實(shí)粒子并不像虛粒子一樣受限制，而實(shí)粒子可以被檢測到。因此可以把真空定義為沒有實(shí)粒子的空間Onemighttthevacuumwouldalwaysbetheeofsibleenergyforaregionofspace.Ifanareaisinitiallyemptyandarealparticleisoit,thetotalenergy,itseems,beraisedeasttheenergyequivalentofthe

53、massoftheaddedparticle.Asurprisingresultofrecenttheoreticalinvestigationstthismptionisnotinvariablytrue.ThereareconditionswhichroductionofarealparticleoffiniteoanemptyregionofspacecanreducethetotalIfthereductioninenergyisgreatenough,anelectronanditronwillbespontaneouslycreated.theseconditionstheelectronitronarenotaresultofvacuumfluctuationsbutarerealparticles,existyandcanbedetected.Inotherwords,undertheseconditionsthevacuumisanunstableandcanoaeoflowerenergy;i.e.,oneinwhichrealparticlesare人們可能會(huì)認(rèn)為，真空是在一片給定區(qū)域空間內(nèi)具有最低能量的狀態(tài)。如果一片區(qū)域初始是的把一個(gè)實(shí)粒子放入其中，總能量應(yīng)該至少增加了那個(gè)被加入粒子的能量。近期的一些理論究的結(jié)果令人吃驚：上述假設(shè)不一定總是正確。某些情況下