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1、UnitFourExtraterrestrialsSpaceExplorationSpaceExplorationIn1981theUSAlaunchedaspaceshuttle,thefirstreusablespacecraft.ThefirstreusablespaceshuttleSpaceExplorationOnOct.15,2003,ShenzhouVsentChina'sfirstastronautYangLiweiintospace,makingChinathethirdnationfollowingtheformerSovietUnionandtheUnitedStat
2、estoplaceahumaninorbit.ChinahopestolaunchtheShenzhouVInextyearinaflightthatwillplacetwoastronautsinorbitforbetweenfiveandsevendays.ShenzhouVTheauthorIsaacAsimov(1920-1992):Russian-bornAmericanauthorandbiochemist,widelyknownforhisfirst-rateworksofsciencefictionforthelayperson.Hepublishedabout500volu
3、mes.TheauthorAsimovisespeciallyadeptatpopularizingscientificwriting.HisimportantworksincludeI,Robot(1950),theFoundationtrilogy(1951-53),TheRobotsofDawn(1983),andOpus300(1984)CulturalNotesVenus:thesecondmajorplanetinorderofdistancefromtheSun.AlsoknownasHesperus,theeveningstar,orPhosphorus,themorning
4、star,VenuscanbethebrightestobjectintheskyaftertheSunandMoonandfollowsanear-circularpathsome106millionkilometersfromtheSun,taking225daystocompleteoneorbit.CulturalNotesExtraterrestriallife:life-formsthatmayhaveevolvedonotherplanets.ThereisnohardevidenceatpresentthatlifeexistsotherthanontheEarth.Most
5、UFOshavebeensatisfactorilyexplainedasbeingnaturalorman-made,andtheVikingmissionstoMarswereinconclusiveintestingfortheexistenceoflifeonthatplanet.CulturalNotesNevertheless,searcheshavebeenandarebeingmadeforsignsthatlifehasariseninotherpartsoftheuniverse.Certainknowledgeeitherthatlifeisconfinedtoplan
6、etEarthorhasbeenfoundelsewherewouldhavetheprofoundestphilosophicalimplicationsformankind.CulturalNotesFactorscontributingtoanyassessmentoftheprobabilitythatlifeexistselsewheremustincludethesize,age,andstructureoftheuniverse,andtheconditionsunderwhichlifeasweknowitcanoriginateandevolve.CulturalNotes
7、Otherfactorsofrelevanceinthesearchforextraterrestriallifeincludeanassessmentoftheprobabilitythatintelligenceleadingtoscientificandtechnologicalcivilizationssimilartoourownmayarise.ThePlanetsOursolarsystemha
