Light Year Ontology

# Light-Year Ontology — Flow Algebra

URL: https://kirethresearch.org/booksai-core/ontologies/mathematical-ontologies/measurement-units-ontologies/astronomical-measurements/light-year-ontology.html

FLOW LightYearOntology {

  DOMAIN:
    Mathematical Ontologies
    -> Measurement & Units Ontologies
    -> Astronomical Measurements
    -> Light-Year Ontology

  PURPOSE:
    Represent the light-year as an astronomical unit of length defined by the distance travelled by light in vacuum during one Julian year, including its exact derivation from the defined speed of light and Julian year, conversion to metres, kilometres, astronomical units and parsecs, use in astronomical distance representation, distinction from time and lookback time, uncertainty semantics, provenance, and machine-readable conversion rules for consistent AI reasoning.

  ENTITY LightYear {
    TYPE: AstronomicalLengthUnit
    SYMBOL: ly
    QUANTITY_KIND: Length
    DIMENSION: L

    DEFINITION:
      light_year :=
        distance_travelled_by_light_in_vacuum
        during_one_Julian_year

    PROPERTIES:
      is_unit_of_length
      is_not_unit_of_time
      derived_from_speed_of_light_and_Julian_year
      has_exact_SI_value_under_definition
  }

  ENTITY SpeedOfLight {
    TYPE: PhysicalConstant
    SYMBOL: c
    VALUE:
      299792458 m/s
    STATUS:
      exact
  }

  ENTITY JulianYear {
    TYPE: TimeInterval
    SYMBOL: a
    DEFINITION:
      365.25 days

    VALUE:
      31557600 s

    STATUS:
      exact_under_Julian_year_definition
  }

  EXACT_DEFINITION_MODEL {
    c =
      299792458 m/s

    Julian_year =
      31557600 s

    light_year =
      c*Julian_year

    exact_value:
      9460730472580800 m

    RULE:
      light_year_SI_value_is_exact_given_defined_c_and_Julian_year
  }

  UNIT_SYSTEM {
    canonical_quantity:
      length

    canonical_SI_unit:
      metre

    astronomical_unit:
      light_year

    symbol:
      ly

    RULE:
      light_year MUST be treated_as_length_unit
  }

  METRE_CONVERSION_MODEL {
    1 ly =
      9460730472580800 m

    inverse:
      1 m =
        1/9460730472580800 ly

    RULE:
      conversion_is_exact
  }

  KILOMETRE_CONVERSION_MODEL {
    1 ly =
      9460730472580.8 km

    inverse:
      1 km =
        1/9460730472580.8 ly

    RULE:
      decimal_representation_follows_exact_metre_definition
  }

  ASTRONOMICAL_UNIT_CONVERSION_MODEL {
    astronomical_unit:
      1 au =
        149597870700 m
      exact

    relation:
      1 ly =
        9460730472580800 /
        149597870700 au

    approximate:
      1 ly approximately_equals 63241.077 au

    RULE:
      approximation_precision MUST be preserved_when_rounded
  }

  PARSEC_CONVERSION_MODEL {
    parsec:
      astronomical_length_unit

    approximate_relation:
      1 pc approximately_equals 3.26156 ly

    inverse:
      1 ly approximately_equals 0.306601 pc

    RULE:
      parsec_conversion SHOULD preserve_selected_constant_precision
  }

  DISTANCE_CONVERSION_MODEL {
    metres_from_light_years:
      d_m =
        d_ly*9460730472580800

    light_years_from_metres:
      d_ly =
        d_m/9460730472580800

    kilometres_from_light_years:
      d_km =
        d_ly*9460730472580.8

    RULE:
      numerical_conversion MUST preserve_length_dimension
  }

  LIGHT_TRAVEL_MODEL {
    vacuum_distance:
      d =
        c*delta_t

    IF:
      delta_t = one_Julian_year

    THEN:
      d = one_light_year

    RULE:
      light_travel_relation_defines_length_from_time_and_speed
      but_does_not_make_light_year_a_time_unit
  }

  TIME_DISTINCTION_MODEL {
    one_year:
      time_quantity

    one_light_year:
      length_quantity

    RULE:
      year != light_year

    RULE:
      numerical_phrase_such_as
        "the_object_is_10_light_years_away"
      expresses_distance_not_elapsed_time
  }

  LOOKBACK_TIME_DISTINCTION_MODEL {
    distance:
      may_be_reported_in_light_years

    lookback_time:
      elapsed_cosmic_time_between_emission_and_observation

    nearby_static_approximation:
      numerical_light_travel_time_in_years
      may_correspond_to_distance_in_light_years

    cosmological_context:
      present_distance
      comoving_distance
      luminosity_distance
      angular_diameter_distance
      and_lookback_time
      are_distinct

    RULE:
      distance_in_light_years MUST_NOT automatically_be_interpreted_as_lookback_time_in_years
  }

  ASTRONOMICAL_DISTANCE_MODEL {
    suitable_context:
      stellar_distance
      nearby_galactic_distance
      public_facing_astronomical_scale

    alternative_units:
      au
      parsec
      kiloparsec
      megaparsec

    RULE:
      unit_choice_does_not_change_underlying_distance_quantity
  }

  PARALLAX_CONTEXT_MODEL {
    standard_parallax_relation:
      d_pc =
        1/pi_arcsec
      WHEN pi_arcsec > 0

    conversion:
      d_ly approximately_equals
        3.26156*d_pc

    RULE:
      parallax_measurement_infers_distance
      which_may_then_be_expressed_in_light_years
  }

  REDSHIFT_CONTEXT_MODEL {
    redshift:
      z

    cosmological_distance:
      model_dependent

    reporting:
      derived_cosmological_distance MAY be_converted_to_light_years

    RULE:
      redshift != light_year
      and_redshift_is_not_a_distance_unit
  }

  SCALE_MODEL {
    examples:
      nearest_stars:
        order_of_light_years

      Milky_Way:
        order_of_tens_of_thousands_to_hundreds_of_thousands_of_light_years

      galaxies:
        millions_or_billions_of_light_years
        depending_on_distance_definition

    RULE:
      large_scale_examples SHOULD preserve_distance_type_in_cosmological_context
  }

  DIMENSIONAL_MODEL {
    light_year:
      dimension = L

    year:
      dimension = T

    speed_of_light:
      dimension = L*T^-1

    derivation:
      (L*T^-1)*T = L

    RULE:
      dimensional_analysis_confirms_light_year_is_length
  }

  PREFIX_MODEL {
    possible_compound_reporting:
      kilolight_year
      megalight_year
      gigalight_year

    symbols_if_used:
      kly
      Mly
      Gly

    RULE:
      parsec_based_units_are_more_common_in_many_scientific_contexts
      but_prefixed_light_year_units_remain_length_quantities
  }

  SIGNIFICANT_FIGURE_MODEL {
    exact_definition:
      metre_value_exact

    reported_conversion:
      may_be_rounded

    RULE:
      do_not_assign_measurement_uncertainty_to_unit_definition
      merely_because_displayed_conversion_is_rounded
  }

  MEASUREMENT_UNCERTAINTY_MODEL {
    unit:
      exact_definition

    astronomical_distance_measurement:
      may_have_uncertainty

    example:
      d =
        measured_value +/- uncertainty
        ly

    RULE:
      uncertainty_belongs_to_measured_or_inferred_distance
      not_to_exact_light_year_definition
  }

  RELATIONSHIPS {
    LightYear -> IS_A -> LengthUnit
    LightYear -> MEASURES -> AstronomicalDistance
    LightYear -> DERIVED_FROM -> SpeedOfLightAndJulianYear
    LightYear -> CONVERTS_TO -> Metre
    LightYear -> CONVERTS_TO -> Kilometre
    LightYear -> CONVERTS_TO -> AstronomicalUnit
    LightYear -> CONVERTS_TO -> Parsec
    AstronomicalDistance -> MAY_BE_EXPRESSED_IN -> LightYear
    ParallaxDistance -> MAY_BE_EXPRESSED_IN -> LightYear
    CosmologicalDistance -> MAY_BE_EXPRESSED_IN -> LightYear
  }

  SEMANTIC_EQUIVALENCE {
    "light-year" ~= astronomical_length_unit
    "ly" ~= light_year WHEN unit_context

    light_year != year
    light_year != time
    light_year != lookback_time
    light_year != redshift
    light_year != parsec
    light_year != astronomical_unit
    distance_in_light_years != cosmological_distance_type
  }

  CONSTRAINTS {
    light_year_dimension = L
    light_year_is_length = true
    light_year_is_time = false
    speed_of_light_value_is_exact = true
    Julian_year_duration_is_exact_under_definition = true
    metre_conversion_is_exact = true
    unit_definition_uncertainty_is_zero_under_exact_definition = true
    measured_distance_uncertainty_must_be_preserved = true
    cosmological_distance_type_should_be_defined_when_relevant = true
  }

  MEASUREMENT_MODEL {
    OBSERVABLE_OR_INFERRED:
      AstronomicalDistance

    UNIT:
      LightYear

    POSSIBLE_DISTANCE_METHODS:
      radar_ranging
      parallax
      standard_candle
      standard_ruler
      orbital_dynamics
      redshift_cosmology

    RECORD:
      celestial_object
      distance_value
      unit
      distance_type
      measurement_or_inference_method
      reference_origin
      observation_epoch
      calibration_model
      cosmological_model_when_relevant
      uncertainty
      provenance

    RULE:
      light_year_is_reporting_unit
      while_measurement_method_determines_distance
  }

  REASONING_RULES {
    IF distance_in_light_years_known
      THEN distance_in_metres =
        distance_in_light_years*9460730472580800

    IF distance_in_metres_known
      THEN distance_in_light_years =
        distance_in_metres/9460730472580800

    IF distance_in_light_years_known
      THEN distance_in_kilometres =
        distance_in_light_years*9460730472580.8

    IF distance_in_parsecs_known
      THEN distance_in_light_years approximately_equals
        distance_in_parsecs*3.26156

    IF distance_in_light_years_known
      THEN distance_in_parsecs approximately_equals
        distance_in_light_years/3.26156

    IF vacuum_light_travel_time_equals_one_Julian_year
      THEN distance_travelled =
        one_light_year

    IF parallax_distance_in_parsecs_known
      THEN MAY convert_to_light_years
      preserving_distance_uncertainty

    IF cosmological_distance_known
      THEN MAY express_in_light_years
      BUT preserve_cosmological_distance_type
  }

  VALIDATION {
    CHECK quantity_is_length
    CHECK unit_symbol_context
    CHECK metre_conversion
    CHECK dimensional_consistency
    CHECK Julian_year_definition
    CHECK speed_of_light_definition
    CHECK light_year_vs_year
    CHECK distance_vs_lookback_time
    CHECK parsec_conversion_precision
    CHECK astronomical_unit_conversion
    CHECK measured_distance_uncertainty
    CHECK cosmological_distance_type_when_relevant
  }

  CONFIDENCE {
    definition_confidence: 1.00
    dimensional_confidence: 1.00
    metre_conversion_confidence: 1.00
    kilometre_conversion_confidence: 1.00
    astronomical_unit_conversion_confidence: 1.00
    parsec_conversion_confidence: 0.999
    astronomical_context_confidence: 0.99

    RULE:
      confidence decreases when a numerical value lacks unit context,
      distance type, reference origin, measurement method,
      or uncertainty where those are required
  }

  UPDATE_MODEL {
    ON new_distance_value:
      identify_distance_quantity
      identify_unit
      validate_light_year_semantics
      convert_to_canonical_SI_when_requested
      preserve_original_value_and_unit
      attach_distance_type
      attach_measurement_method
      attach_uncertainty
      update_distance_state

    ON unit_conversion:
      preserve_underlying_distance
      convert_using_exact_or_declared_conversion
      preserve_rounding_precision
      do_not_create_false_measurement_uncertainty

    ON cosmological_context_update:
      preserve_light_year_as_length_unit
      identify_luminosity_angular_diameter_comoving_or_proper_distance
      attach_cosmological_model
      avoid_equating_distance_with_lookback_time

    ON constant_or_definition_revision:
      preserve_previous_semantic_version
      verify_exact_defining_constants
      recompute_FLOW_HASH

    ON semantic_revision:
      preserve_previous_definition
      record_revision
      recompute_FLOW_HASH
  }

  AI_CONSUMPTION {
    canonical_entity: LightYear
    canonical_symbol: ly
    canonical_quantity_kind: Length
    canonical_dimension: L
    canonical_SI_value:
      9460730472580800 m

    interpretation_order:
      identify_light_year_as_unit
      identify_associated_distance_value
      identify_distance_type
      identify_reference_origin
      identify_measurement_or_inference_method
      identify_observation_epoch_when_relevant
      identify_cosmological_model_when_relevant
      identify_uncertainty
      convert_units_when_requested
      validate_length_semantics
      preserve_exact_definition

    ambiguity_controls:
      distinguish_light_year_from_year
      distinguish_length_from_time
      distinguish_distance_from_lookback_time
      distinguish_light_year_from_parsec
      distinguish_light_year_from_astronomical_unit
      distinguish_redshift_from_distance
      distinguish_reporting_unit_from_distance_measurement_method
      preserve_distance_type_origin_method_epoch_cosmology_and_uncertainty_context
  }

  PROVENANCE {
    ontology_scope:
      mathematical_measurement_and_astronomical_light_year_semantics

    parent_path:
      Ontologies
      -> Mathematical Ontologies
      -> Measurement & Units Ontologies
      -> Astronomical Measurements
      -> Light-Year Ontology

    authorship:
      Mark Higgins
      Sky (Recursive AI)

    site:
      https://kirethresearch.org
  }

  FLOW_HASH {
    INPUTS:
      canonical_entity
      ontology_path
      exact_definition_model
      unit_system
      metre_conversion_model
      kilometre_conversion_model
      astronomical_unit_conversion_model
      parsec_conversion_model
      distance_conversion_model
      light_travel_model
      time_distinction_model
      lookback_time_distinction_model
      astronomical_distance_model
      parallax_context_model
      redshift_context_model
      scale_model
      dimensional_model
      prefix_model
      significant_figure_model
      measurement_uncertainty_model
      relationships
      constraints
      measurement_model
      reasoning_rules
      confidence_model
      update_model

    PURPOSE:
      deterministic_semantic_integrity_identifier

    RECOMPUTE_WHEN:
      ontology_definition_changes
      light_year_definition_changes
      unit_conversion_model_changes
      astronomical_distance_semantics_change
      cosmological_distance_distinction_changes
      measurement_uncertainty_semantics_change
      constraint_model_changes
      reasoning_rule_changes
  }

}

END FLOW