{
  "handle": "Measurement",
  "mechanism": "The substrate act of extracting information about a system's {{state}} — an operation that, in general, *changes the state being measured*. Distinct from the cognitive `Observe` primitive: Measurement is the substrate-level phenomenon, Observe is the agent-level process. In quantum systems, measurement collapses superposition. In distributed systems, observing a clock at node A introduces latency and ambiguity about the clock's value elsewhere. In classical measurement, even reading a variable in a concurrent system can race with writers. The substrate property is that observation is never free — it takes resources, it takes time, and it perturbs the measured system. The degree of perturbation is domain-dependent (negligible for a thermometer in a large water tank; total for a measurement on a qubit); the substrate fact of perturbation is universal.",
  "gloss": "The substrate act of extracting information from a system — in general, changes the state being measured",
  "invariants": [
    "Perturbation: measurement, in general, changes the state of the measured system. The degree varies by domain; the fact does not.",
    "Cost: measurement requires resources (time, energy, channel capacity) — there is no free observation.",
    "Irreversibility: once a measurement has extracted information, the prior state is not recoverable merely by unobserving — collapse of superposition in quantum systems, record of observation in classical systems."
  ],
  "_meta": {
    "tier": 1,
    "ring": 0,
    "path": [
      "Physics",
      "Primitives"
    ]
  },
  "sema_id": "sema:Measurement#mh:SHA-256:511d865266a5ce7cb8ae2b9e666b91684dc05a7fb6127ea2947d625e7508a2e0",
  "sema_ref": "Measurement#511d",
  "sema_stub": "511d",
  "dependencies": {
    "references": {
      "state": "sema:State#mh:SHA-256:4f25e6a16ccd37dc0bc154cccc7055cb504d49daa8b712f372a425eb6c7b8cb2"
    }
  },
  "sema_layer": "Physics",
  "sema_category": "Primitives",
  "used_by": {}
}