` ::::: Eh, but don't you think that quantities which are conserved and invariant no matter who looks, aren't somehow more real? I suppose this is a philosophical question, but what else do we mean by ``real`` except: ``That which everyone measures the same, and thus agrees on`` ? Thus, it's not this or that component of the field that is ``real``, but rather the amount of ``charge`` that gives rise to all components of the field, measured in all directions and integrated. Some of which vary accoding to observer, but each observer somehow sees the sum-total (some volume-integral through all space) as being the same. Invariant mass is sort of a gravitational ``charge.``  `