PUH Theorem 374 — Time Begins With Two: A Lone Massless Seed Cannot Be Told From the SPF; Two Share One Relational Number, Their Mass, and Make the First Clock; More Seeds Break E8 to E7, E6, SO(8)

Photonic Universe Hypothesis (PUH) — Derivation- What is the source of time part 2. THE OCCASION. An outside review of T373 (ChatGPT, 30 September 2026) accepted its algebra and asked four questions: what is a state, what makes two configurations distinguishable, how does physical time arise without an outside clock, and what drives a seed. THE DEFINITIONS. A state is the Lie–Poisson momentum of a region (T172, T238), and the momenta of combined regions add. With no external frame — the SPF premise — only quantities unchanged by all of E8 can be observed, so distinguishability is relational. Time is a change in such a quantity (T242). Every number is computed from the E8(−24) build of T373. RESULT 374.1. A lone massless seed has every invariant of the SPF — its own orbit reaches toward zero (shrunk by e⁻⁶ = 0.0025 at s = 3) — so no observation can tell it from the SPF. Its growth is energy-neutral (B(P, Y) = 0) and changes nothing observable, and a flow applied to every region changes no relation (the pairing stays at −240). T373's "directions of distinction" is NARROWED: distinction needs a second region. RESULT 374.2. Two massless seeds share exactly one relational number: their common stabiliser is 133-dimensional, so 58 + 58 − 115 = 1, for the opposite pair and for four random pairs alike. It is their Killing pairing B. RESULT 374.3. That number is their mass: the quadratic invariant of their total is exactly 2B (−480.000 for the opposite pair), the identity that gives two photons a mass as a pair. Masses combine by I₂(μ₁ + μ₂) = I₂(μ₁) + I₂(μ₂) + 2B and add exactly only when B = −m₁m₂, as for parallel states; a boosted pair gives more than the sum (ratio 1.255) and clocks at orthogonal roots give less (1/√2), which Minkowski space never allows but E8(−24), with 136 time-like directions, does. RESULT 374.4. Inside gravity's sl(2,ℝ) (T303–T304) the Killing form is diag(−120, +120, +120): a 2+1 light cone whose null directions are the seeds. Pairs combine into clocks (B < 0), descents (B > 0) or massless states (B = 0); seeds at orthogonal roots make a 92-direction massless state. RESULT 374.5. A lone seed has no clock: all its frequencies are zero and its flow grows as a power of time. Two seeds make one, with a purely imaginary spectrum and rate √(|B|/15) — 4, 8 and 12 for B = −240, −960 and −2,160, unchanged by boosts, and the same law for random pairs — so the clock's rate is proportional to the pair's mass, the Compton relation of matter-wave clocks. Mass and the first clock appear together. The clocks of one rate form the hyperbolic plane SL(2,ℝ)/SO(2), the kind of target T302 found rotation requires, and a relative flow between two regions returns its own time parameter exactly from their relation (0.500, 1.000, 2.000). RESULT 374.6. As generic seeds accumulate, the relational numbers run 0, 1, 4, 12, 42, 100 and the unbroken symmetry steps E8 → E7 → E6 → SO(8) → nothing, while the seeds generate sl(2), sl(3), so(8) and all of E8 — E8's dual pairs (A1, E7), (A2, E6), (D4, D4), identified by dimension, rank and a single root length. They include the E7 × SU(2) of the weak sector (T212, T265) and the E6 × SU(3) whose SU(3) T257 reads as the family triplet. Unlike T353's cascades, this chain needs no step rule. RESULT 374.7. T320's bond energy between two massless neighbours is −J·B, the same number (+240 J for the opposite pair). In E8(−24) the Killing norm is indefinite, so the bond is negative when B > 0 (−60 J computed, with J positive as the archive fixes it) — which T338 and T350 forbid, while T264's indefinite metric implies it. T338 named this as its own kill-condition (ii). WHAT CHANGES: T373 Result 373.3 NARROWED and 373.5 QUALIFIED; T336 DERIVED from the substrate and EXTENDED; T172's merged Casimir values MADE EXPLICIT for the quadratic invariant; T287's mass-conserving mergers — CONDITION NAMED (B = −m₁m₂); T302–T304 OBSERVATION (the space of clocks is their hyperbolic plane; the reduction is still not derived); T338 and T350 against T264 and T320 — IN CONFLICT. KILL-CONDITIONS: an external frame in the substrate (Result 374.1 would not apply); momenta of combined regions that do not add (the composition rule changes); a folding form other than E8(−24) (Tables 1 and 2 must be recomputed). NOT CLAIMED: that PUH's dynamics produces pairs of seeds; that the pair's invariant equals any measured mass; that the three-seed sl(3) is the family symmetry of T257; that gravity's reduction lands in this sl(2,ℝ); any rate in seconds. OPEN: whether the lattice equations generate relative flows, and from what seeds; the sign conflict, which decides whether the substrate's energy is bounded below; whether core mergers meet B = −m₁m₂.