Unit2Sailingtheoceans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
Thehandleofthespoonpointstothesouth,whiletheothersidepointstothenorth
WhentheSinanisinthestill,thehandleofthespoonpointstothesouthbecauseoftheinfluenceoftheterrestrialmagnetism(地磁).AstrolabeIthas17starslistedaswellasamapoftheskyoverhead(for37degrees)andtheecliptic(黄道).ThetimeofdayornightisontheoutsideedgewithnoonatthetopoftheAstrolabeandmidnightatthebottom
Itcomeswithacarryingchain,apouch,andabookonitsuse
Thereversesidehasasightformeasuringtheelevationsoftheheavenlybodies
SextantThesextantisanavigationalinstrumentformeasuringtheanglebetweenthe