Say I have a vector space $V$ over a field $L$ with a subfield $K$ (so that it's a field extension $L/K$), it's not hard to see that the dimension of $V$ over $K$ can be larger than over $L$ (for instance, take a tower of three fields, consider the top as a vector space over the bottom 2, the degrees multiply, etc.) -- but can the dimension ever decrease when you restrict the scalars to a subfield? Is that possible? (I can't find an example.)
@LucasHenrique it's inertia in disguise, from a different frame of reference, google "fictitious force"