托福听力十大必背段子2.doc

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1、托福听力十大必背段子22.000143理科段子：天文学　　Inancienttimes,manypeoplebelievedtheearthwasaflatdisc.Wellover2,000yearsago;theancientGreekphilosopherswereabletoputforwardtwogoodargumentsprovingthatitwasnot.Directobservationsofheavenlybodieswerethebasisofboththesearguments

2、.First,theGreeksknewthatduringeclipsesofthemoontheearthwasbetweenthesunandthemoon,andtheysawthatduringtheseeclipses,theearth'sshadowonthemoonwasalwaysround,theyrealizedthatthiscouldbetrueonlyiftheearthwasspherical,Ittheearthwasaflatdisc,thenitsshadowduri

3、ngeclipseswouldnotbeaprefectcircle;itwouldbestretchedoutintoalongellipse.ThesecondargumentwasbasedonwhattheGreekssawduringtheirtravels.TheynoticedthattheNorthStar,orPolaris,appearedlowerintheskywhentheytraveledsouth,inthemorenortherlyregions,theNorthStar

4、appearedtothemtobemuchhigherinthesky.Bytheway,itwasalsofromthisdifferenceintheapparentpositionoftheNorthStarthattheGreeksfirstcalculatedtheapproximatedistancearoundthecircumferenceoftheearth,afigurerecordedinancientdocumentssays400.000stadium,that'sthepl

5、uraloftheworldstadium.Today,it'snotknownexactlywhatlengthonestadiumrepresents,butlet'ssayitwasabout200meters,thelengthofmanyathleticstadiums.ThiswouldmaketheGreek'sestimateabouttwicethefigureacceptedtoday,averygoodestimateforthosewritingsolongbeforeevent

6、hefirsttelescopewasinvented.