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《【托福聽力備考】tpo13 聽力文本——lecture 4》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在應(yīng)用文檔-天天文庫(kù)。
1、【托福聽力備考】TPO13聽力文本——Lecture4眾所周知，托福TPO材料是備考托福聽力最好的材料。相信眾多備考托福的同學(xué)也一直在練習(xí)這套材料，那么在以下內(nèi)容中我們就為大家?guī)硗懈PO聽力練習(xí)的文本，希望能為大家的備考帶來幫助。TPO13Lecture4AstronomyNarrator:Listentopartofalectureinanastronomyclass.Professor:OK,Iwannagooverthedifferenttypesofmeteorites,andwhatwe’velearnedfromthemabouttheformationofEar
2、th,andthesolarsystem.Uh…thethingiswhat’sespeciallyinterestingaboutmeteoritesisthattheycomefrominterplanetaryspace,buttheyconsistofthesamechemicalelementsthatareinmatteroriginatingonEarth,justindifferentproportions.Butthatmakesiteasiertoidentifysomethingasameteorite,asopposedto…tojustaterrestr
3、ialrock.Sototalkaboutwheremeteoritescomefrom,weneedtotalkaboutcometsandasteroids,whichbasically...they’rebasicallymadeupofdebrisleftoverfromtheoriginofthesolarsystem4.6billionyearsago.NowI’mgoingabitoutofaorderhere…um…I’mnotgoingtogointoanydepthoncometsandasteroidsnow,butwe’llcomebacklaterand
4、dothat.Fornow,I’lljustcoversomebasicinfoaboutthem.OK,cometsandasteroids.Itmighthelpifyouthinkof...rememberwetalkedaboutthetwoclassesofplanetsinoursolarsystem?Andhowtheydifferincomposition?Theterrestrialplanets--likeMarsandEarth--composedlargelyofrocksandmetals,andthelargegasgiants,likeJupiter
5、.Well,thesolarsystemalsohastwoanalogousclassesofobjects,smallerthanplanets--namely,asteroidsandcomets.Relativelynearthesun,intheinnersolarsystem,betweenJupiterandMarstobeprecise,we’vegottheasteroidbelt,whichcontainsabout90percentsofallasteroidsorbitingthesun.Theseasteroidsare…uh…liketheterres
6、trialplanets,inthatthey’recomposedmostlyofrockymaterialandmetals.Farfromthesun,intheoutersolarsystem,beyondJupiter’sorbit,temperaturesarelowenoughtopermiticestoformoutofwaterand…andoutofgaseslikemethaneandcarbondioxide.Loosecollectionsoftheseicesandsmallrockyparticlesformintocomets.Socometsar
7、esimilarincompositiontothegasgiants.Bothcometsandasteroidsare...typicallyaresmallerthanplanets.Anevensmallertypeofinterplanetarydebrisisthemeteoroid.Andit’sfrommeteoroidsthatwegetmeteorsandmeteorites.“Roids”are,forthemostpartanyway,theyarejus
