A suggestive - but, alas, only suggestive - discussion of the relationship in modern physics between empirical verification and theoretical models. The question arises because some of today's physicists posit some entities (e.g., the other universes of multiverse theory) that are not (directly?) observable.
Adam Frank & Marcelo Gleiser:
A Crisis at the Edge of Physics
NYTimes (Op., June 5, 2015)
