There's one quantity that's going to come out the same, no matter who is looking at the vector.

但是也有一个量是始终不变的,不管是谁在观察这个矢量

耶鲁公开课 - 基础物理课程节选

The length of the vector is the length of the vector.

这个矢量的模长是保持不变的

耶鲁公开课 - 基础物理课程节选