大学英语精读文本1-6册(txt下载) 分节阅读 7

,collectionsorarraysofradiotelescopes,sensitiveradiodetectors,advancedcomputersforprocessingreceiveddate,,ifwearewiseenoughtomaketheeffort,

Somescientistsworkingonthequestionofextraterrestrialintelligence,myselfamongthem,haveattemptedtoestimatethenumberofadvancedtechnicalcivilizations--definedoperationallyassocietiescapableofradioastronomy--;theabundanceofplanetarysystemsandthelikelihoodoftheoriginoflife,whichweknowlesswell;andtheprobabilityoftheevolutionofintelligentlifeandthelifetimeoftechnicalcivilizations,

Whenwedothearithmetic,thesortsofnumberswecomeupwithare,characteristically,,anditisexhilaratingtoimaginethediversity,,andevenwithamillioncivilizations,lessthanonestarin200,,

Despiteclaimsaboutancientastronautsandunidentifiedflyingobjects,,ofthelong-distancetechniquesavailabletoourtechnology,;radiosignalstravelatthespeedoflight,fasterthanwhichnothingcango;andtheuseofradioforcommunicationisnotashort---,thereareonlyafewobviousmethods,

ThefirstseriousattempttolistenforpossibleradiosignalsfromothercivilizationswascarriedoutattheNationalRadioAstronomyObservatoryinGreenbank,WestVirginia,,nowatCornelUniversity,andwascalledProjectOzma,aftertheprincessoftheLandofOz,aplaceveryexotic,,

SinceProjectOzma,therehavebeensixoreightothersuchprograms,allatarathermodestlevel,intheUnitedStates,

However,,handinhandwiththerecentspectacularadvancesinradiotechnology,,

Butalongwiththeburgeoningdedicationtoaserioussearch,:Ifextraterrestrialintelligenceisabundant,whyhavewenotalreadyseenitsmanifestations?