Because positing them allows you explain things about the rotation of the star or the gravitational fluctuations, what have you.

因为这样假定能帮助你解释,诸如星体运行,引力波动,等现象

耶鲁公开课 - 死亡课程节选

And the winery had a management rotation program.

这个酒庄有一个管理轮岗项目。

我的职业是 - SpeakingMax英语口语达人

So it's very important to be keeping in mind that any time you see a double bond, you have a pi bond there, so you're not going to see any rotation around the bond axis.

所以你们要记住,任何时候你们看到一个双键，这里面有π键，你们不会看到关于键轴的任何转动。

麻省理工公开课 - 化学原理课程节选

Actually, the view of vectors we take nowadays is that vectors are associated with a pair of numbers which, on the rotation of axes, transform like this.

实际上,今天我们讲矢量所用的观点是,矢量是和一组坐标值相对应的,在坐标轴旋转的过程中像这样变换

耶鲁公开课 - 基础物理课程节选

The idea that he had was, if you go from me to you, with a clockwise rotation, you go from you to me by a counterclockwise rotation.

他的方法是这样的,如果这个矢量从这转到那是顺时针方向,那么这个矢量转回来就是逆时针方向

耶鲁公开课 - 基础物理课程节选

When we have just a single bond in them molecule, you have all the free rotation you want, you can just spin it around, there's nothing keeping it in place.

当我们在分子力只有一个单键时，你可以随意旋转，你可以让它转起来，没有什么东西能固定住它。

麻省理工公开课 - 化学原理课程节选