两千年之前欧亚大陆的两端,雄踞着两大帝国,各自统治着所属的区域~([1])。西边是正在征战欧洲的罗马帝国,而东边则是继短命的秦王朝之后统治着现今中国大部分地区的汉王朝。尽管这两个帝国在其鼎盛时期的疆域面积旗鼓相当,但它们衰落之后的政治遗产却大不相同~([2])。在罗马帝国的疆域内再也没能重现这样的盛况,而中国则在公元前221年秦朝统一之后,基本上延续了这种大一统的局面,尽管其间有过暂时 Two thousand years ago, the two ends of Eurasia dominated the two great empires and ruled their respective regions ~ ([1]). To the west is the Roman Empire that is experiencing Europe, and to the east is the Han dynasty that ruled most of China today following the short-lived Qin Dynasty. Although the two empires were equally large in the area of ​​their heyday, their political legacy after the decline was quite different (2). This grand occasion was never repeated in the Roman Empire, and China, after the unification of the Qin and Qin dynasties in 221 BC, basically continued this grand unification despite the temporary