And in 1961, during the Cold War with the Soviet Union, John Kennedy urged people to take an active part in the future: "And so, my fellow Americans, ask not what your country can do for you - ask what you can do for your country.

VOA: special.2009.01.19

the zeroth law, which is the common-sense law, which says that if you take a hot object next to a cold object, heat will flow from the hot to the cold in a way that is well defined, and it allows you to define temperature.

上节课我们讨论了，热力学第零定律,这一定律源自常识：如果把一个热的物体,与一个冷的物体挨在一起，热量就会以确定的方式。

麻省理工公开课 - 热力学与动力学课程节选

And so what I'm really doing is inviting you to take a good, cold, hard look at death, and to face it and think about it in a way that most of us don't do.

那就是我要你们做的，认清，死亡的好和坏，面对它，然后思考它,用我们从没用过的方式。

耶鲁公开课 - 死亡课程节选

Take a perspective of the cold virus.

从感冒病毒的角度看。

耶鲁公开课 - 心理学导论课程节选