"Which doesn't sound that far if you have a car, but it sounds very far if you have to get on a bus, and you have to carry your week's worth of groceries home with you."

VOA: standard.2010.07.28

How much energy are you going to get out, and how far are you going to be able to drive a car with this expansion, let's say, so that's the problem.

你能获得多少能量，利用这次膨胀,你可以把你的车开出多远，比如说这就是问题所在。

麻省理工公开课 - 热力学与动力学课程节选