Ifyouwatchtheskyforaboutanhourafterthesungoesdown,youma...
问题详情：Ifyouwatchtheskyforaboutanhourafterthesungoesdown,youmayseesome“movingstars”.Butthey’renotrealstars.They’reman-madesatellites(人造卫星).AndthebiggestofallistheInternationalSpaceStation(ISS...