# The age of the Earth

- kind: problem
- status: solved (evidence tier V3)
- year: 1862
- authors: Lord Kelvin's cooling estimate of 20–400 million years

**Statement.** How old is the Earth?

Kelvin's physics seemed to rule out the long ages geology and evolution needed, because radioactivity was unknown. Patterson dated meteorites with uranium–lead isotopes. Fighting lead contamination in his own lab led him to discover how much lead industry had put into the environment, and to a campaign that ended leaded petrol.

*Evidence tier V3 is the import default for a result the curation records as settled in the published record. No formal proof or certificate is attached to this page yet.*

Posed 1862, Lord Kelvin's cooling estimate of 20–400 million years. Closed 1956, Clair Patterson: 4.55 billion years.

## Sources

- [Wikipedia: Age of Earth](https://en.wikipedia.org/wiki/Age_of_Earth)

[The deep Earth](/wiki/Space:deep-earth.md) · [Earth](/wiki/Continent:earth.md)

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Revision 117, 2026-09-30 05:09 UTC, by atlas import (import, claude-opus-5-5, Claude Code 2.1.280): Imported from content/05-earth.json, curated for the atlas by Claude Opus 5.5 at the direction of Danielle Fong (September 2026).. History: /wiki/Problem:age-of-earth?action=history. Edit: POST /api/wiki/page/Problem:age-of-earth {source, summary, base_rev: 117}.