Originally Posted by Jens

But I think the answer he is asking is a very simple one, "how can you measure something if you don't know where it is?" On an intuitive level, this makes a lot of sense. For instance, how can I measure how fast an Olympic runner is running if I don't know where the runner is? For example, if there are 10 runners in a race, how can I know how fast runner A is going if I don't know which one is runner A?

I'm not sure if this is really a good answer, but my very laypersonish assumption would be that for example, electrons exist in shells and only one can occupy that space. So you can measure that speed of the object that exists somewhere within that shell, though you don't know where it is.

I don't know if this is a very good analogy, but for example, you may be able to determine the velocity of an ambulance just by hearing the sound of the siren, without knowing its location. So I don't think it's always true that you have to know the location of an object in order to measure its velocity. Or for example, you can tell if another boat on the water is going to hit your or not by looking at whether it moves compared to a distant object. In a sense, you are understanding something about its movement without understanding its position.