英语阅读.(2-1)
Theairsurroundingusisimportanttoeveryone.Withoutair,wecouldnotexist.Everyoneunderstandsthat.Butairisnecessaryinmanyotherways—waysthatarenotalwayssoobviousorwidelyknown.
Forexample,ifwedidnothaveair,therewouldbenosound.Soundtravelsthroughair.Wherethereisnoair,thereisnosound.Withoutair,therewouldbenofire.Therewouldbenoautomobiles,sincemotorsneedairinordertooperate.
Withoutair,therewouldbenowindorclouds.Therewouldbenoweather,asweknowit.Thenighttimewouldbeverycoldandthedaysveryhot.Wewouldbeforcedtoseekshelterfromthesun,astherewouldbenoatmospheretoprotectusfromthesun’sdeadlyrays.
Theatmosphereisalltheairsurroundingtheearth.Atmosphericpressureistheweightofallthatairagainstthesurfaceoftheearth.Ifwedidnothaveatmosphericpressure,wecouldnothaveautomobiletires.Thetireswouldswellorburstiftheydidnothavethepressureoftheatmosphereagainsttheirsurfaces.
Largeandpowerful,theatmosphereconsistsofanoceanofgaseshundredsofmileshigh.Itpressesdownonourbodieswithaforceofmorethanfourteenpoundspersquareinch.Thenarrowcolumnofairwhichrestsuponourshouldersweighsalmost2,000pounds.Butourbodiesarebuiltinsuchawaythatitsweightdoesnotcrushus.
Inthishugeoceanofairthereismoreenergythaninallthecoal,oil,andgaswehaveonearth.Electricalenergyiscollectedintheatmosphereaswateriscollectedandstoredinadam.Theexistenceofelectricityintheairhasbeenknownforcenturies.Menhavegazedinwonderatthebrightpatternsoflightninginstormclouds.Butathoroughstudyofelectricityintheatmospherewasnotpossibleuntilthedevelopmentofradioandradar.
Onescientist,Dr.SydneyChapman,hastriedtoexplaintheelectricfieldwhichsurroundstheearth.Hebelievesthatthegreatstormsonthesuncreatelargeamountsofelectricenergy.Thisenergyiscontainedinaverylightgascalledhydrogen.Theearthpullsthegastowardit,andaringisformedaroundtheearthseveralthousandfeetaboveitssurface.Thegreatspaceringisapowerfulcurrentofelectricalenergy.Sometimestheringcomesdownandcurvesintotheloweratmosphere,causingstrange