it's clear that you want to add a vector that looks like that, because then you go from the start of this to the finish of that, you end up at the same point and you get this invisible 0 vector.

显然应该给它加上这样一个矢量,因为从这个矢量的起点指向那个矢量的终点,最终指向的是同一个点,你就得到这个不可见的零矢量

耶鲁公开课 - 基础物理课程节选

So one of the things that the Allies very specifically wanted to do in World War II was to hijack one of these devices, take it from a U-boat because if they had this physical machine, certainly can they start decrypting then the German messages.

所以同盟国在二战中想做的一件事,就是劫持其中一个装置，携带在U型潜水艇中，因为如果他们拥有了这种物理装置，他们就可以解码,德国人的密文。

哈佛公开课 - 计算机科学课程节选