The Pristine Bubble: Why You Can't Detect the Substrate from Inside dc1 substrate (has a definite rest frame) Counter-rotating boundary layer EM modons cannot cross p e observer's atom (also a quasiparticle!) modon (light) speed = c everywhere INSIDE: Lorentz-invariant acoustic metric All instruments, clocks, rulers, and light are quasiparticles of the same superfluid He-4 Analogy Phonons in superfluid helium obey ω² = c₁²k² — Lorentzian with c₁ = 238 m/s as "light speed" A phonon MM experiment inside He-4 would also give a null result Why It Works Speed of excitations is set by collective dynamics (equation of state), not individual particle frame The substrate is the metric. You can't step outside it to look. The Key Insight Your rulers contract. Your clocks dilate. Your light bends. All by exactly the amount needed to make the substrate undetectable — because they're all made of it.