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VOA英语听力原文Weusuallythinkofpollutionasaharmfulwastesubstancethatthreatenstheairandwater.Butsomepeoplehavebecomeconcernedaboutanotherkindofpollution.Itcanbeeverywhere,dependingonthetimeofday.Anditisnotthoughtofasasubstance.Itislight.Theideaoflightpollutionhasdevelopedwiththeincreaseoflightsincities.Inmanyareas,thislightmakesitdifficultorimpossibletoobservestarsandplanetsinthenightsky.InNineteen-Eighty-Eight,theb5E2RGbCAPInternationalDark-SkyAssociationformed.Thisorganizationwantstoreducelightpollutioninthenightsky.Italsourgestheeffectiveuseofelectriclighting.p1EanqFDPwThereareanumberofreasonswhylightpollutionisimportant.OnehasbecomeclearattheMountWilsonObservatorynearLosAngeles,California.MountWilsonObservatorywashometothelargesttelescopesintheworldduringthefirsthalfoftheNineteen-Hundreds.DXDiTa9E3dDuringthatperiod,LosAngelesgrewtobecomeoneofAmerica'sbiggestcities.Today,lightfromLosAngelesmakesthenightskyaboveMountWilsonverybright.Itisnolongeranimportantresearchcenterbecauseoflightpollution.RTCrpUDGiTLightpollutionthreatenstoreducethescientificvalueofresearch5PCzVD7HxAtelescopesinotherimportantobservatories.TheyincludeLickObservatorynearSanJose,CaliforniaandYerkesObservatorynearChicago,Illinois.Lightpollutionistheresultofwastedenergy.BrightlightthatshinesintotheskyisnotbeingusedtoprovidelightwhereitisneededonEarth.Poorlydesignedlightingcausesagreatdealoflightpollution.Lightsthatarebrighterthannecessaryalsocauselightpollution.jLBHrnAILgRecently,twoItalianastronomersandanAmericanenvironmentalscientistcreatedaworldmapofthenightsky.ThemapshowsthatNorthAmerica,WesternEuropeandJapanhavethegreatestamountoflightpollution.xHAQX74J0XMostpeopleinAmericaaresurprisedtofindoutthattheyareabletoseeourowngalaxy,TheMilkyWay,withtheirowneyes.Butaboutthree-fourthsofAmericanscannotseetheMilkyWaybecauseofman-madelight.LDAYtRyKfEObjectsinthenightskyareresourcesthatprovideeveryonewithwonder.Butlightpollutionthreatenstopreventthosewonderfulsightsfrombeingseen.Zzz6ZB2Ltk