Derived metric methodology, version 1.0

Independently survivable human worlds

Count of worlds whose human population could sustain itself indefinitely with no resupply from Earth, assessed against the six published criteria.

DerivedMetric page

Specification

How the value is computed

spec hash 2cc5c48ef6358c29

Formula in plain words

The custom function dated_assessment over the whole component dataset, for each geography and period. A period with any component missing produces no value.

Components

No component metrics: the value is an assessment recorded by the named function, with its basis on every row.

Combination: Named function dated_assessment, evaluated once over the whole component dataset (it reads across geographies or records an assessment) and returning the observation ids it used.
Missing data: Skip the period: no value is produced unless every component is present. Nothing is interpolated or carried forward.
Window: None: each period stands on its own.
Normalization: None: the combined value is published in its own unit.
Unit and rounding: worlds. No rounding; the value is stored as computed.
Default geography: WLD

Parameters

{
  "assessments": [
    {
      "period": "2026-01-01",
      "value": 1,
      "basis": "Earth is the only world meeting every independence criterion."
    }
  ]
}

Coverage

What has been computed

Current values: 1
Geographies: 1
Periods: 1, 2026 to 2026
Last computed: 2026-09-07 22:04 UTC
Produced by: version 1.0

Reproducibility

Last verification

Outcome: success
Run at: 2026-09-07 22:15 UTC
Examined: 5101 derived values across all metrics, 5090 reproduced, 0 issues
This metric: 1 of 1 reproduced, 0 issues

Worked example

World, 2026

Stored value

1 worlds

Observation id: 404045
Formula version: 1.0
Source revision: v1.0/e3b0c44298fc
Computed at: 2026-09-07 22:04 UTC
Coverage: 0 of 0 components (minimum 0)

Recorded with the value

{
  "basis": "Earth is the only world meeting every independence criterion."
}

Component observations used

0 observations

This value reads no component observations: it is an assessment, and its basis is recorded above.

History

Version history

metric_method_versions

Version 1.0, effective 2026-01-01 00:00 UTCcurrent

Formula count(worlds where every independence criterion is met)

Independently survivable human worlds, version 1.0

Definition. A world is counted only if it hosts a human population that could sustain itself indefinitely with no resupply from Earth. Every criterion below must hold at the same time, with no time limit, for the whole resident population:

Energy. Generates all the energy it consumes from local resources, including the energy needed to maintain and replace its own generating equipment.
Food. Produces all calories, protein and micronutrients its population needs from local agriculture or synthesis, including seed stock, inputs and the equipment to keep producing.
Water. Sources, purifies and recycles all water needed for drinking, agriculture and industry from local supplies.
Air. Maintains a breathable atmosphere for its population indefinitely, whether naturally or through locally built and locally maintained life support.
Manufacturing. Can fabricate replacement parts for every system it depends on, from raw materials extracted locally, including the machines that make the machines.
Medicine. Can produce essential medicines, medical equipment and train medical staff locally at a level that keeps the population viable across generations.

Population viability also requires a population large and diverse enough to persist across generations; this version does not set a numeric threshold because no candidate beyond Earth is close to the other criteria.

Assessment as of 2026-01-01. Earth meets all criteria. No station, base or settlement beyond Earth meets any of criteria 1 to 6 without resupply. Count = 1.

Unit. Worlds (integer count).

Update rule. The value is reassessed annually and whenever a candidate settlement publishes evidence against the criteria. A change in the count requires a new methodology version citing that evidence. Partial progress (for example a base that is energy independent but not food independent) does not change the count; it belongs in separate progress metrics.