2018版高中英语（人教版）选修9同步教师用书：Unit 2 Period Ⅰ 单元预习课.doc

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1、Unit2　SailingtheoceansPeriodⅠ　单元预习课当今航海技术达到前所未有的水平，那么你知道古代一些有关航海方面的仪器吗？Sinan，theancientChinesecompassItwasinventedbyZhangHengintheHanDynasty.Itismadeupofabronzefoundation(青铜底盘)andmagneticspoon(磁勺)whichismadeofnaturalmagnet，positionedrightinthecenterofthefoundation.Thehandleofthespoonpoints

2、tothesouth，whiletheothersidepointstothenorth.WhentheSinanisinthestill，thehandleofthespoonpointstothesouthbecauseoftheinfluenceoftheterrestrialmagnetism(地磁)．AstrolabeIthas17starslistedaswellasamapoftheskyoverhead(for37degrees)andtheecliptic(黄道)．Thetimeofdayornightisontheoutsideedgewithnoona

3、tthetopoftheAstrolabeandmidnightatthebottom.Itcomeswithacarryingchain，apouch，andabookonitsuse.Thereversesidehasasightformeasuringtheelevationsoftheheavenlybodies.SextantThesextantisanavigationalinstrumentformeasuringtheanglebetweenthehorizonandsomeobjectinthesky.Firstasailorlooksatthehoriz

4、onthroughaneyepiece.Atthesametimehecanseelightfromthesunorastarreflectedoffasmallmirrorontopoftheinstrument，ontoasecondmirrorandintotheeyepiece.Thenavigatorcanthenseetwoimages，thehorizonandthesunsidebyside.Hecanthenmeasuretheanglebetweenthemonascaleatthebottomoftheinstrument.Thescalegoesfr

5、om0to120degrees.Anearlierinstrument，calledaquadrant，measuredinangleinthesamewaybutitcouldonlymeasureanglesfrom0to90degrees.NauticalchartNauticalchartsaremapsofthedepthoftheseaandthecurrentsoftheoceans.Theyprovidemodernsailorswithroutesthroughtheseas，ratherlikeroadsthroughthecountryside.The

6、informationbegantobecollectedinthenineteenthcenturyandhascontinuedtobeupdatedeversince.ThesechartswerenotavailabletoCaptainBlighorZhengHe.1．WhatisthetheoryoftheSinaninventedbyZhangHeng?_________________________________________________________________________________________________________

7、_______________________2．WhyweretheNauticalchartsnotabletobeusedbyCaptainBlighorZhengHe?________________________________________________________________________________________________________________________________【答案】　1．Theinfluenceoftheterrestrialmagnetism