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体。这个概念囊括了简单的细菌到具有高度智慧的外星人。研究和测试关于外星生命猜想的学科被称作地外生物学或天体生物学。Possiblebasis(存在与否）ScientificsearchBackgroundCulturalimpactCONTENTS1952年美国新泽西州所拍摄的UFO人类普遍对外星人的刻板印象BackgroundPossiblebasisAlienlife,suchasmicroorganisms（微生物）,hasbeenhypothesizedtoexistintheSolarSystemandthroughouttheuniverse.Thishypothesisreliesonthevastsize（广博的面积）andconsistentphysicallaws（一致的物理定律）oftheobservableuniverse.Accordingtothisargument,madebyscientistssuchasCarlSagan(卡尔·萨根:太空科学家)andStephenHawking(史蒂芬·霍金),itwouldbeimprobableforlifenottoexistsomewhereotherthanEarth.ThisargumentisembodiedintheCopernicanprinciple,whichstatesthatEarthdoesnotoccupyauniquepositionintheUniverse,andthemediocrityprinciple,whichsuggeststhatthereisnothingspecialaboutlifeonEarth.PossiblebasisPossiblebasisPossiblebasisAlllifeonEarthisbasedupon26chemicalelements.However,about95%ofthislifeisbuiltupononlysixoftheseelements:carbon,hydrogen,nitrogen,oxygen,phosphorusandsulfur,abbreviatedCHNOPS（碳、氢、氧、磷及硫）.ThesesixelementsformthebasicbuildingblocksofvirtuallyalllifeonEarth,whereasmostoftheremainingelementsarefoundonlyintraceamounts（微量）.PossiblebasisPossiblebasis认为地球之外存在生命有着很简单的事实的支持：仅仅在银河系中就有2000亿至4000亿颗恒星，而银河系只是宇宙中超过1000亿星系中的一员。据估计至少有十分之一的类似太阳的恒星具有行星系统。Possiblebasis科学家在搜索外星生命时，多以液态水和有机物的存在作为外星生命存在之前提条件。水为地球生命体内各种化学反应提供了场所。有人批评这样以地球生物为蓝本的先入为主的观点阻碍了外星生命的探索。卡尔·萨根在1973年提出碳沙文主义，认为这些以人类为中心的思想限制了我们对于地外生命可能性的想像。例如在宜居带之外，有可能通过地热等方式维持地底的生物圈；也有生物能够在高砷低磷的环境下存活，这说明生物组成“必备”的六大基本元素：碳、氢、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间接探索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，美国国家航空航天局分别发射了勇气号和机遇号火星探测器，其目标是探测火星上水存在的可能性、分析火星岩石和土壤的成分、评估火星是否适合生命生存等。这两个双胞胎探测器均在2004年1月在火星成功着陆。在2011年11月26日发射的好奇号火星探测器也在2012年8月6日成功登陆火星，用于评估火星上是否存在过适合微生物生存的环境TerrestrialPlanetFinderTheNASAKeplerforthesearchforextrasolarplanets.IndirectsearchScientistshaveproposedradiated

heat

fromaplanetasawaytofindadvancedcivilizations.

Large-scalepowergenerationreleaseslargeamountsofheat,whichcanbedetectedusinganadvancedtelescope,suchastheproposedColossus

interferometric

telescope.

Thefactthattheheatsignatureswouldbecomingfrompowergeneration,especiallyinurbanareas,where

heatislands

arecreated,wouldalsoconfirmthattheobservedcivilizationisadvanced.Largerpowerconsumptioncorrelateswithmore-advancedsocieties.Detectingthermalsignaturesallowstheabilitytodetectadvancedcivilizationsindirectly,asopposedtotryingtomakedirectcontactthroughmessageslikethosecreatedby

ActiveSETI.SETI对外星智能的探索(searchforextraterrestrialintelligence).科学家认为生命可能曾经存在过或者依然存在的地方包括金星、火星、木星的卫星、土星的卫星。除了太阳系的行星和卫星之外，科学家在太阳系外也找到了数十颗位于宜居带太阳系以外的行星。科学家保守估计每两颗恒星中就有一颗拥有行星，每200颗恒星中就有一颗位于宜居地带。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.内华达375号州道旁的路牌，由于靠近51区而被称命名为“外星人公路”。火星侦察轨道器的高分辨率成像科学设备拍摄的高分辨率“火星人脸”影像，右下角为海盗号拍摄的影像。Theoreticalphysicist

StephenHawking

in2010warnedthathumansshouldnottrytocontactalienlifeforms.HewarnedthataliensmightpillageEarthforresources."Ifaliensvisitus,theoutcomewouldbemuchaswhen

Columbus

landedin

America,whichdidn'tturnoutwellfo