The thing on the right is yelling at me for replying too many times. Of course if we had the proven solution for gravity we could wade through a lot of theories but even here I don’t see a self-contained universe as one precluding the existence of a larger box that we could be inside of, only potentially precluding its necessity. I only brazenly argue with confidence about boxes within boxes because I know no one can currently argue against it affirmatively rooted in absolute fact, not because of some innate wisdom. When gravity has a solution and people need to do real science and math I’ll gladly keep my silence and absorb while people put the puzzle together 
It’s funny because this is related to the idea of space time itself being reflective of an atomic structure which in turn makes me think of a fractal. Or, perhaps not a fractal and we can go back to the cave allegory and our perception of space time is just an imperfect reflection of actual space-time (or something else?), which would again, take us outside the original box.
I’m just resistant to the idea that we can ever solve the existence of humanity through physics. I think at best it’s the model in which to test our ideas of the meaning of humanity. And with that pseudo-scientific dribble I leave the conversation to you fine sirs since we’ve already established I submit to authority and I don’t want to test that dialog box on the right.