But from the point of view of a phonon, the solid is indistinguishable from a vacuum. What distinguishes the 'real' vacuum from what the phonon sees? Why is wh

But from the point of view of a phonon, the solid is indistinguishable from a vacuum. What distinguishes the 'real' vacuum from what the phonon sees? Why is what we call 'the universe' necessarily primal? Maybe it is 'vibrating solids' all the way down. If there is something primal, then what are its characteristics that allows what we see as the vacuum to emerge?