周三，美国航空 (American Airlines) 5342号航班通过美国最为拥挤的空中走廊之一、准备降落在里根国家机场 (Reagan National Airport)，当天已有700多架飞机在该机场起降。

Modern life makes us tired, right? But research from societies in Africa and South America suggests people in the ancient world slept only 6.5 hours a night.

Modern life makes us tired, right? But research from societies in Africa and South America suggests people in the ancient ...