Yeah, and I don’t mean to suggest that there are no further levels to discover and understand or more fundamental properties to explain the ones we know, just t

Yeah, and I don’t mean to suggest that there are no further levels to discover and understand or more fundamental properties to explain the ones we know, just that there is a limit to what we know, and that at some level things which are experimentally observed are assumed. IMO these are always excellent questions, and there are people looking to find explanations and more fundamental physics, but this is increasingly difficult as current models explain current observations very well and it is hard to go further with experiment. Even if there are further levels to be understood, those probably won’t lead to any more satisfying answers, just a swap of one axiom to ponder with a more fundamental one. I think it is like asking about epicycles prior to Kepler, or asking about Kepler’s laws prior to Newton (and on). There are new and better explanations, but always more questions than answers, and some things that just are (as far as we know).