Life › Life & humans today › Deep time & the age of the Earth
Clair Patterson dates the Earth
1956: 4.55 billion years· Event· Earth, climate & extinctions
Well establishedStrong fossil, genetic or geological evidence.
Geochemist Clair Patterson measured lead in meteorites and showed that Earth is about 4.55 billion years old.
See it on the Life map →What happened
Earth's oldest rocks have been recycled, so Patterson (1922–1995) turned to meteorites, leftovers from the cloud that formed the planets. Uranium decays to lead at a known rate, and lead isotopes in the Canyon Diablo meteorite, from Arizona's Meteor Crater, gave 4.55 billion years, published in 1956. To get clean results he built an ultra-clean lab and found that lead from gasoline was contaminating everything. He then campaigned for decades to ban leaded fuel.
Why it matters
It fixed the length of Earth's history, the time scale for all of life's story, and led to removing lead from gasoline.
The evidence (fossils, genes, rocks)
His 1956 paper; today's best estimate, 4.54 billion years plus or minus 50 million, agrees. Blood lead levels fell sharply after leaded gasoline was phased out in the U.S. (1970s to 1996).
Still debated
Exactly how long Earth took to finish assembling after the first solar-system solids formed 4.567 billion years ago, perhaps tens of millions of years.
Connections (2)
▸Clair Patterson dates the Earth measured the age of Formation of EarthWell established
The connection
Earth's surface has been recycled, so its earliest rocks are gone. Patterson assumed that meteorites formed at the same time from the same material, and that lead in ocean sediments represents Earth's average. Both fell on one uranium-lead age line at 4.55 billion years, dating Earth's formation itself rather than its oldest surviving rocks.
When and how
Measured in 1953 at Argonne National Laboratory near Chicago, with Patterson based at Caltech; published in 1956 in the journal Geochimica et Cosmochimica Acta.
The evidence
Later meteorite dates, Moon rocks from Apollo and 4.4-billion-year-old zircon crystals from Western Australia all fit; today's figure is 4.54 billion years, plus or minus 50 million.
Debates and open questions
Earth grew over tens of millions of years, so 'formation' is a span, not a moment; when the Moon-forming impact happened within that span is still debated.
▸Clair Patterson dates the Earth fixed the scale of Deep time & the age of the EarthWell established
The connection
Before 1956, estimates of Earth's age varied widely: Kelvin's tens of millions of years, then early radiometric figures of roughly 1.6 to 3.4 billion. Patterson's meteorite measurement set the figure at 4.55 billion years, which has barely changed since. It became the fixed frame for dating the whole history of life.
When and how
Caltech and Argonne National Laboratory, 1953; published 1956. Earlier radiometric estimates came from Arthur Holmes in 1913 and the 1940s.
The evidence
Moon rocks, many more meteorites and better instruments have since confirmed his result to within about 1%.
Debates and open questions
Little about the number is disputed; reading Earth's first few hundred million years from the scarce minerals that survive remains a research frontier.