I hear different things all over the place and would like to clear up the confusion: So I understand that, under HUP, position and momentum are things we can't know with arbitrary precision at the same time because momentum implies a measure of wavelength, but measuring wavelength means we're intrinsically introducing an uncertainty in position based on the probability function defined by that wave. When we talk about the Casimir effect and particles popping in and out of existence (even in "empty space"), do we say we can really get something from nothing? Or do we say it's simply consistent with HUP? Does pair production imply that the Big Bang could happen out of "nothing" via quantum fluctuations? Or does pair-production only make sense with respect to our universal framework as opposed to the creation of that framework itself?