You can only do this because it's reversible. What else do I know?

这一步,只对可逆过程成立，还有什么已知条件？

麻省理工公开课 - 热力学与动力学课程节选

You can only do it at zero degrees Kelvin.

你只能在0下做到这点。

麻省理工公开课 - 热力学与动力学课程节选

There's only one occasion where it helps to go to three dimensions because there are certain things you can do in 3D you cannot do in less than 3D.

只有一种情况下进入三维是有意义的,因为有些事情你能在三维空间内完成,但低于三维就做不到了

耶鲁公开课 - 基础物理课程节选