Then, I tell you I went for 5 km on the second day and another 5 km on the third day.

然后我第二天行进了5公里,第三天又走了5公里

耶鲁公开课 - 基础物理课程节选

You can deal with this by saying not just 5 km, but plus or minus 5 km.

你不能只说5公里,而应该是+5或者-5公里

耶鲁公开课 - 基础物理课程节选

Yeah. So I spent two years in Israel studying in the place called Gush at Etsyon the Etsyon Block which is about 20 km south of Jerusalem.

对，所以说我在以色列待了两年,在Etsyon的Gush学习,在距耶路撒冷以南20公里的Etsyon地区。

普林斯顿公开课 - 人性课程节选

So I could be 10 km from home, I could be 0 km from home, or I could be -10, if I'd gone two steps to the left.

我有可能距营地10公里,也可能是0公里,也可能是 -10,如果我两次都是向左的话

耶鲁公开课 - 基础物理课程节选

But, you know, in 2D, the options are not just left and right or north and south, but infinity of possible directions in which I could go those 5 km.

但在二维空间中,不仅可以向左向右或者向南向北,我在走那5公里的时候可以有无数个方向

耶鲁公开课 - 基础物理课程节选

It's not enough to say I went 5 km.

只知道我走了5公里是不够的

耶鲁公开课 - 基础物理课程节选

These two guys are 5 km long.

这两段都是5公里长

耶鲁公开课 - 基础物理课程节选