Space is not a substance - but that does not mean it is nothing - conversely just as an electron or an atom is commonly identified as something - - in reality neither is a chunk of something - electrons and atoms have some property(s) that are localized and some that are extended throughout the universe. When Einstein was asked to summarize his General Theory in one sentence, he replied "Time and space and gravitation have no separate existence from matter." While there is no spatial motion that can be thought of as a conventional current, space nonetheless can be modeled in some situations as obeying the mathematical rules that apply to moving fluids