You spend a lot of time talking about the transition between alchemy and modern chemistry.

在高中化学你很多时间是花在,了解从炼金术到化学的改变上。

麻省理工公开课 - 化学原理课程节选

Your mortgage payment is constant through time but the fraction of it that goes to paying off principal versus interest changes through time and it just changes as dictated by this formula.

抵押贷款每月还款是固定的,但是其中本金和利息的比例关系,会随时间而改变,这是由这个公式所决定的

耶鲁公开课 - 金融市场课程节选

But I want to give you at least some sense of the development of the pro-slavery argument, the kinds of arguments that were used, how they changed over time, who made the arguments.

但我至少想提供给你们一些,支持奴隶制方的论据,他们曾经用来论证的一些理由,是如何随着时间的推移而改变,又是谁提出了这些理由

耶鲁公开课 - 美国内战与重建课程节选