外星生命中英presentation

Extraterrestrialcivilizations

(地外文明）ExtraterrestriallifeContentsExtraterrestriallifeislifethatdoesnotoriginatefromEarth.Itisalsocalledalienlife,or,ifitisasentientandrelativelycomplexindividual,an"extraterrestrial"or"alien“.外星生命指存在于地球以外的生命體。這個(gè)概念囊括了簡(jiǎn)單的細(xì)菌到具有高度智慧的外星人。研究和測(cè)試關(guān)于外星生命猜想的學(xué)科被稱作地外生物學(xué)或天體生物學(xué)。Possiblebasis(存在與否）ScientificsearchBackgroundCulturalimpactCONTENTS1952年美國(guó)新澤西州所拍攝的UFO人類普遍對(duì)外星人的刻板印象BackgroundPossiblebasisAlienlife,suchasmicroorganisms（微生物）,hasbeenhypothesizedtoexistintheSolarSystemandthroughouttheuniverse.Thishypothesisreliesonthevastsize（廣博的面積）andconsistentphysicallaws（一致的物理定律）oftheobservableuniverse.Accordingtothisargument,madebyscientistssuchasCarlSagan(卡爾·薩根:太空科學(xué)家)andStephenHawking(史蒂芬·霍金),itwouldbeimprobableforlifenottoexistsomewhereotherthanEarth.ThisargumentisembodiedintheCopernicanprinciple,whichstatesthatEarthdoesnotoccupyauniquepositionintheUniverse,andthemediocrityprinciple,whichsuggeststhatthereisnothingspecialaboutlifeonEarth.PossiblebasisPossiblebasisPossiblebasisAlllifeonEarthisbasedupon26chemicalelements.However,about95%ofthislifeisbuiltupononlysixoftheseelements:carbon,hydrogen,nitrogen,oxygen,phosphorusandsulfur,abbreviatedCHNOPS（碳、氫、氧、磷及硫）.ThesesixelementsformthebasicbuildingblocksofvirtuallyalllifeonEarth,whereasmostoftheremainingelementsarefoundonlyintraceamounts（微量）.PossiblebasisPossiblebasis認(rèn)為地球之外存在生命有著很簡(jiǎn)單的事實(shí)的支持：僅僅在銀河系中就有2000億至4000億顆恒星，而銀河系只是宇宙中超過1000億星系中的一員。據(jù)估計(jì)至少有十分之一的類似太陽(yáng)的恒星具有行星系統(tǒng)。Possiblebasis科學(xué)家在搜索外星生命時(shí)，多以液態(tài)水和有機(jī)物的存在作為外星生命存在之前提條件。水為地球生命體內(nèi)各種化學(xué)反應(yīng)提供了場(chǎng)所。有人批評(píng)這樣以地球生物為藍(lán)本的先入為主的觀點(diǎn)阻礙了外星生命的探索?？枴に_根在1973年提出碳沙文主義，認(rèn)為這些以人類為中心的思想限制了我們對(duì)于地外生命可能性的想像。例如在宜居帶之外，有可能通過地?zé)岬确绞骄S持地底的生物圈；也有生物能夠在高砷低磷的環(huán)境下存活，這說明生物組成“必備”的六大基本元素：碳、氫、氧、氮、磷、硫，可能不是必需的。LifeonEarthrequires

water

asits

solvent

inwhichbiochemicalreactionstakeplace.Sufficientquantitiesofcarbonandtheotherelementsalongwithwater,mayenabletheformationoflivingorganismsonotherplanetswithachemicalmake-upandtemperaturerangesimilartothatofEarth.PossiblebasisPossiblebasisScientificsearchScientificsearchScientificsearchScientificsearchDirectsearch直接探索Indirectsearch間接探索Extrasolarplanets可能存在的外星生命ScientistsaredirectlysearchingforbiosignatureswithintheSolarSystem,carryingoutstudiesonthesurfaceofMarsandexaminingmeteorsthathavefallentoEarth.Atthemoment,noconcreteplanexistsforexplorationofEuropaforlife.In2008,ajointmissionbyNASAandtheEuropeanSpaceAgencywasannouncedthatwouldhaveincludedstudiesofEuropa.However,in2011NASAwasforcedtodeprioritizethemissionduetoalackoffunding,anditispossiblethattheESAwilltakeonthemissionbyitself.Directsearch2003年6月10日和7月7日，美國(guó)國(guó)家航空航天局分別發(fā)射了勇氣號(hào)和機(jī)遇號(hào)火星探測(cè)器，其目標(biāo)是探測(cè)火星上水存在的可能性、分析火星巖石和土壤的成分、評(píng)估火星是否適合生命生存等。這兩個(gè)雙胞胎探測(cè)器均在2004年1月在火星成功著陸。在2011年11月26日發(fā)射的好奇號(hào)火星探測(cè)器也在2012年8月6日成功登陸火星，用于評(píng)估火星上是否存在過適合微生物生存的環(huán)境TerrestrialPlanetFinderTheNASAKeplerforthesearchforextrasolarplanets.IndirectsearchScientistshaveproposedradiated

heat

fromaplanetasawaytofindadvancedcivilizations.

Large-scalepowergenerationreleaseslargeamountsofheat,whichcanbedetectedusinganadvancedtelescope,suchastheproposedColossus

interferometric

telescope.

Thefactthattheheatsignatureswouldbecomingfrompowergeneration,especiallyinurbanareas,where

heatislands

arecreated,wouldalsoconfirmthattheobservedcivilizationisadvanced.Largerpowerconsumptioncorrelateswithmore-advancedsocieties.Detectingthermalsignaturesallowstheabilitytodetectadvancedcivilizationsindirectly,asopposedtotryingtomakedirectcontactthroughmessageslikethosecreatedby

ActiveSETI.SETI對(duì)外星智能的探索(searchforextraterrestrialintelligence).科學(xué)家認(rèn)為生命可能曾經(jīng)存在過或者依然存在的地方包括金星、火星、木星的衛(wèi)星、土星的衛(wèi)星。除了太陽(yáng)系的行星和衛(wèi)星之外，科學(xué)家在太陽(yáng)系外也找到了數(shù)十顆位于宜居帶太陽(yáng)系以外的行星?？茖W(xué)家保守估計(jì)每?jī)深w恒星中就有一顆擁有行星，每200顆恒星中就有一顆位于宜居地帶。ExtrasolarplanetsAstronomerssearchforextrasolarplanetsthatmaybeconducivetolife,narrowingthesearchtoterrestrialplanetswithinthehabitablezone.Currentradiodetectionmethodshavebeeninadequateforsuchasearch,becausetheresolutionaffordedbyrecenttechnologyisinadequateforadetailedstudyofextrasolarplanetaryobjects.CultureimpactThefailuresofaroftheSETIprogramtodetectanintelligentradiosignalafterdecadesofeffort,hasatleastpartiallydimmedtheprevailingoptimismofthebeginningofthespaceage.Notwithstanding,beliefinextraterrestrialbeingscontinuestobevoicedinpseudoscience,conspiracytheories,andinpopularfolklore,notably"Area51"andlegends.Ithasbecomeapopculturetropegivenless-than-serioustreatmentinpopularentertainmentwithe.g.theALFTVseries(1986–1990),TheX-Files(1993–2002),etc.內(nèi)華達(dá)375號(hào)州道旁的路牌，由于靠近51區(qū)而被稱命名為“外星人公路”。火星偵察軌道器的高分辨率成像科學(xué)設(shè)備拍攝的高分辨率“火星人臉”影像，右下角為海盜號(hào)拍攝的影像。Theoreticalphysicist

StephenHawking

in2010warnedthathumansshouldnottrytocontactalienlifeforms.HewarnedthataliensmightpillageEarthforresources."Ifaliensvisitus,theoutcomewouldbemuchaswhen

Columbus

landedin

America,whichdidn'tturnoutwellfo