测量不是一件容易的事情。为什么？

因为不确定性（uncertainty）。

量子水平上有测不准原理：The Heisenberg’s uncertainty principle says that at the quantum level, if you can quantify one aspect of a particle (say, its position) then you cannot quantify another (its momentum or where it is going).

在物理学中有一个更普遍的原理，叫做观察者效应（Observer Effect ），它指出对于某些系统，测量某物的行为会影响或改变某物。（There is a more general principle in physics called the Observer Effect that states for certain systems, the act of measuring something affects or changes that thing.）

从心理学家和社会科学家唐纳德·坎贝尔（Donald Campbell）那里，我们得到了坎贝尔定律（Campbell’s Law），它警告我们：

The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.

It’s not so easy to gain the true measure of things

https://theconversation.com/its-not-so-easy-to-gain-the-true-measure-of-things-92741