Ifyouwatchtheskyforaboutanhourafterthesungoesdown,youma...
問題詳情：Ifyouwatchtheskyforaboutanhourafterthesungoesdown,youmayseesome“movingstars”.Butthey’renotrealstars.They’reman-madesatellites(人造衛星).AndthebiggestofallistheInternationalSpaceStation(ISS...