{"id": "card_earth_radiometric_dating", "kind": "reference", "title": "Radiometric dating — deep time from decay", "body": "A radioactive isotope halves every half-life; after two half-lives a quarter remains (sealed). The parent-to-daughter ratio dates a rock - uranium-lead gives the age of the Earth, 4.54 billion years. It is the first-order decay law, borrowed from chemical kinetics.", "source": {"label": "Narrow Highway — earth science", "url": "", "authority_tier": "engine_derived"}, "shelf": "codex", "box": "earth_science", "bands": ["earth science", "pillar", "radiometric_dating", "one map"], "subject": "Radiometric dating — deep time from decay", "connections": [{"to_card_id": "card_floor_earth_science", "relationship": "part_of", "evidence": "a pillar of earth science (Radiometric dating)"}, {"to_card_id": "card_floor_physical_chemistry", "relationship": "connects_at", "evidence": "radiometric dating is first-order decay - the half-life sealed on physical chemistry"}, {"to_card_id": "card_floor_chemistry", "relationship": "connects_at", "evidence": "isotopes and daughter products are chemistry"}], "author": "engine", "created_at": 0.0, "updated_at": 0.0, "visibility": "public", "lifecycle_stage": "public", "volatility": "permanent", "surface": "secular", "generated": false, "call": "codex.earth.science", "facets": {"subject": ["earth science", "one map", "pillar", "radiometric_dating"]}, "presentation": {"glyph": "•", "kind_label": "earth science", "by": "Narrow Highway — earth science", "authority": "engine_derived", "posted": "", "standing": ""}, "neighbors": [{"id": "card_floor_earth_science", "title": "Earth science — the planet, read in deep time", "relationship": "part of", "why": "a pillar of earth science (Radiometric dating)", "href": "/card/card_floor_earth_science", "resolved": true}, {"id": "card_floor_physical_chemistry", "title": "Physical chemistry — rate, equilibrium, acid-base, redox", "relationship": "connects at", "why": "radiometric dating is first-order decay - the half-life sealed on physical chemistry", "href": "/card/card_floor_physical_chemistry", "resolved": true}, {"id": "card_floor_chemistry", "title": "Chemistry — quantum mechanics applied, the periodic table", "relationship": "connects at", "why": "isotopes and daughter products are chemistry", "href": "/card/card_floor_chemistry", "resolved": true}], "house": {"door": "FIND", "kind": "card", "trail": "connections", "seal": "/card/card_earth_radiometric_dating", "next_step": {"do": "follow a connection: what this card rests on, and what rests on it", "door": "FIND", "tool": "card_connections", "params": {"id": "card_earth_radiometric_dating"}}, "ends": "a verdict or a card · the trail · a seal · one next step"}}