{
  "id": "huxa-astronomy-02",
  "version": "0.1",
  "date": "2026-10-23",
  "language": "is",
  "title": "Stjörnufræði, stærðfræði og Málkerfið",
  "kind": "source-based-study-and-design-proposal",
  "sources": [
    {
      "id": "calendar",
      "url": "https://aa.usno.navy.mil/faq/calendars",
      "read": "Introduction, Intercalation"
    },
    {
      "id": "sidereal",
      "url": "https://aa.usno.navy.mil/faq/GAST",
      "read": "Definition and degrees-to-hours conversion"
    },
    {
      "id": "month",
      "url": "https://eclipse.gsfc.nasa.gov/LEsaros/LEperiodicity.html",
      "read": "1.4 Saros; mean periods around 2000 CE"
    },
    {
      "id": "year",
      "url": "https://aa.usno.navy.mil/faq/leap_years",
      "read": "Background"
    },
    {
      "id": "jupiter",
      "url": "https://userpage.fu-berlin.de/ossendrijver/ossendrijver-2016-science-all.pdf",
      "doi": "10.1126/science.aad8085",
      "read": "Science pp. 482–484; supplementary methods/Text A; Figure 2 inspected"
    },
    {
      "id": "kepler",
      "url": "https://science.nasa.gov/solar-system/orbits-and-keplers-laws/",
      "read": "Kepler laws and Newton generalization"
    }
  ],
  "constants": {
    "synodic_month_days": 29.530589,
    "tropical_year_days": 365.2422,
    "scope": "Approximate mean values for teaching, not an ephemeris. Lunar value circa 2000 CE.",
    "source_ids": [
      "month",
      "year"
    ]
  },
  "calculations": {
    "twelve_lunations_days": 354.367068,
    "year_minus_twelve_lunations_days": 10.875132000000008,
    "metonic_lunar_minus_solar_hours": 2.0787599999821396,
    "equal_sectors_formula": "angle_degrees = 360 / n",
    "jupiter": {
      "tablet": "BM 40054",
      "source": "jupiter",
      "days": 60,
      "initial_degrees_per_day": 0.2,
      "final_degrees_per_day": 0.15833333333333333,
      "formula": "days * (initial + final) / 2",
      "displacement_degrees": 10.75,
      "assumption": "linear rate change; reconstruction of model, not observed position verification"
    },
    "kepler_period_ratio_for_doubled_semimajor_axis": 2.8284271247461903
  },
  "new_record_fields": [
    "reference_frame",
    "cycle_definition",
    "equation",
    "assumptions",
    "observed_value",
    "calculated_value",
    "residual",
    "uncertainty",
    "epoch"
  ],
  "synthesis": {
    "status": "our-design-proposal",
    "text": "Tákn varðveitir samband; varpa má lotu yfir í horn, tíma, tölur eða skráningu og prófa hvað varðveitist."
  },
  "next_test": "Compare fixed-model predictions with independent observation data; not performed.",
  "limits": [
    "Equal sectors are a modern geometric illustration, not evidence of an eight-sign ancestral alphabet.",
    "Approximate calendar constants drift over long times.",
    "Historical tablet dating is approximate.",
    "No common origin of writing systems established.",
    "Kepler example assumes same primary mass, negligible secondary mass, and no perturbations."
  ]
}