Every entry maps one thing in the crystal to one thing in the cosmos. The mathematics translates cleanly — until the final page, where one word has no translation at all.
Filled valence band, nothing excited. The crystal at rest. Every "particle" that will ever appear is an excitation above this state.
The quantum vacuum. Lowest-energy state of the fields. Every Standard Model particle is an excitation above this state.
Season one ended on a suspicion: the exciton might not be a counterfeit particle, but an honest particle of a different vacuum. Season two takes the suspicion seriously and builds the dictionary. First entry, the easiest: both worlds define "nothing" the same way — not as absence, but as the lowest rung. Everything else is bookkeeping above it.
This entry is green because it isn't an analogy at all. Effective field theory treats both identically; the vacuum is a ground state by definition on both sides of the arrow.
The hole: an unoccupied state in a filled band. Positive charge, effective mass, drifts backward in a field.
The positron: originally "an unoccupied state in the sea of filled negative-energy levels." Dirac, 1930.
The exciton: electron bound to hole, drifting as one neutral object, annihilating into a photon.
Positronium: electron bound to positron, unstable, ends in light. Same Bohr math, different vacuum.
This is the entry where the dictionary stops being a metaphor and becomes genealogy. Antimatter was invented as hole theory. Condensed matter kept the sea and the picture; particle physics quietly dropped the sea and kept the particle. Season one's protagonist, the exciton, is positronium's twin raised in a different household.
One asymmetry survives translation: positronium annihilates into pure radiation and the constituents cease to exist. The exciton's recombination refills a band state — the crystal's sea is real and observable, Dirac's was scaffolding.
Inside a superconductor the photon acquires mass from the condensate. Fields are expelled past the London depth λ_L. The Meissner effect is a massive gauge boson.
The W and Z acquire mass from the Higgs condensate filling all space. The weak force is short-ranged for exactly the reason magnetic fields die inside niobium.
The Anderson–Higgs mechanism was discovered in a superconductor first. Anderson published the mass-generation argument in 1962; the particle-physics papers arrived in 1964. On this entry the universe is, with a straight face, a superconductor — and the W and Z are its heavy photons.
The photon's borrowed mass is measurable and computable: m_γc² = ħc / λ_L. Drag the penetration depth and watch the photon gain and lose weight.
Near graphene's Dirac points, electrons obey the massless Dirac equation with v_F ≈ c/300 in the role of light speed. Emergent Lorentz invariance, complete with a cone.
Relativity: one invariant speed, a light-cone causal structure, Dirac fermions. The things we take as bedrock.
Nobody installed relativity in graphene. It emerged — the honeycomb lattice's band structure conspires, near two special points, to reproduce the massless Dirac equation with its own private light speed. Electrons there don't know about the lattice any more than we know about whatever underlies spacetime.
Amber, and the amber is the interesting part: the symmetry is exact only at low energy. Push toward the cutoff and the lattice shows through — the cone warps, invariance dies. If our Lorentz invariance is likewise emergent, this predicts what its violation would look like near the Planck scale. So far, searches for that violation have found nothing: either the cutoff is farther than we can see, or the bedrock is real bedrock.
Flow a condensate faster than its own sound speed: phonons inside can't escape upstream. A sonic horizon, emitting a thermal whisper of phonon pairs at ~nK.
An event horizon emitting Hawking radiation — entangled pairs split at the boundary, one falls, one escapes.
Unruh noticed in 1981 that sound in a moving fluid obeys the same wave equation as light near a black hole. Decades later, Steinhauer's group built the flowing condensate and reported the spontaneous, entangled phonon emission — the analog Hawking effect, in a lab, at roughly a nanokelvin.
Red chip, deliberately. The experiment is real and beautiful, but it imports the horizon by hand — the flow profile is imposed, not gravitating. It shares Hawking's kinematics (fields on a horizon) while having none of Einstein's dynamics. It tests the robustness of Hawking's derivation, which is genuinely valuable; it does not test gravity. Anyone selling it as more is over-claiming, and this series doesn't.
Ground states translate. Antiparticles translate. Mass generation, light cones, even horizons translate. One word has no silicon-side entry: gravity itself. Nobody has made a lattice whose collective modes obey Einstein's equations. The graveyard of attempts is the most instructive page in the dictionary.
Don't put gravity in; integrate out matter fluctuations and the Einstein–Hilbert action falls out, the way elasticity falls out of atoms. Mechanism beautiful. Fails on the numbers: the cosmological constant comes out wrong by ~10¹²⁰.
A real fluid with emergent Weyl fermions, gauge fields, and an effective metric. Everything emerges except the one thing needed. The metric obeys hydrodynamics, not Einstein. Names the problem; doesn't solve it.
Assume entropy ∝ horizon area and δQ = TdS locally; Einstein's equations drop out as an equation of state — like the ideal gas law from molecular chaos. A consistency argument, not a construction. Says gravity is thermodynamic; silent on the molecules.
Gravity as an entropic force of hidden information; the 2016 version tried to eat dark matter and made testable predictions. Credit for falsifiability; lensing and dwarf-galaxy data have mostly not cooperated.
Bulk geometry reconstructed from boundary entanglement; cut the entanglement and space literally disconnects. The closest thing to the missing entry. Rigorous only in anti-de Sitter. We live in de Sitter. The solved case is the one we're not in.
A theorem: no massless spin-2 particle composite from a theory with a Lorentz-covariant stress tensor. Every emergent-gravity proposal must show its dodge at the door. AdS/CFT's dodge: the graviton lives in a different spacetime than its constituents. The honest ones wear the dodge openly.
The scorecard: thermodynamics says gravity smells emergent, explicit media deliver everything but the dynamics, the entanglement program delivers the dynamics in the wrong universe, and a theorem checks IDs at the door. Spin-1 is easy to fake. Spin-2 is provably hard. The wafer's curvature stays unmapped — and that gap, not any entry above it, is the finding.