Sky Fortress + Net

[IlPalazzo]

I just found a nice example in which it will be clear that tie to something doesn't mean speed fixed at 0 - at least with my knowledge about the english language.

That's right, I think the wording and meaning might be the same in German and English... It's not the wording but general intuition that leads one to think that being tied/fixed to the ground means zero speed because ground itself isn't generally isn't considered moving, thus the object it's tied to shouldn't be moving either.