Mercury is a liquid metal, and mercury, the planet, is the fastest moving naked eye heavenly body. Mars, iron, why is Mars red?

水银是液态金属，水银，行星，是肉眼能看到的运动最快的天体,火星，铁，为什么火星是红色的？

麻省理工公开课 - 固态化学导论课程节选

That is why we don't worry about the motion of the nucleus 1 because the ratio of mass is about 2,000 to one.

这就解释了为什么我们不担心,原子核运动起来,因为原子核和电子的质量比约为2000：

麻省理工公开课 - 固态化学导论课程节选

Dynamics then tells you why the object goes up, why the object goes down and why is it pulled down and so on.

而动力学则会告诉你为什么物体向上运动,为什么向下运动,为什么停下来,等等

耶鲁公开课 - 基础物理课程节选

Or a football player--when you're running down the field, why did you go to this way instead of that way ? when you're running down the field?

或者是问一个橄榄球运动员--当你在操场上奔跑时，你为什么要往这边跑而不是那边呢,当你在操场上跑的时候？

耶鲁公开课 - 金融市场课程节选

It's related to the frequency with which you go around the circle Why is that?

它也跟圆周运动的频率有关,为什么呢

耶鲁公开课 - 基础物理课程节选