Scientific method
Determination of numerical ages from the decay of long-lived radioactive isotopes in rocks and minerals. It dates the last time a sample was melted or sufficiently disturbed, which is why the age of a rock and the age of the Earth are different questions.
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Radioactive decay converts a parent isotope into a daughter isotope at a rate expressed as a half-life; isotopes that decay slowly serve as geological clocks.
Evidence support: Supported by the cited evidence one source
Evidence: Newman 1997 Primary authority
Radiometric dating measures the last time the sample was melted or disturbed enough to rehomogenise its radioactive elements — not, in general, the age of the material it is made from.
Evidence support: Supported by the cited evidence one source
Evidence: Newman 1997 Primary authority
Record last updated 2026-09-06. Corrections follow the published corrections policy; superseded claims are retained, never silently edited.