Initial reaction in the Arab world among leaders and the public at large has been overwhelmingly positive to the news that President Obama is the winner of this year's Nobel Peace Prize.

VOA: standard.2009.10.09

Within 20 degrees of separation from you initial smile to the three people, the entire world will be smiling.

只需要20度的分隔,从你用笑容感染三个人开始，全世界就会笑起来。

哈佛公开课 - 幸福课课程节选