EARTH × TECHNOLOGY

Four and a Half Billion Years

1956 CE

Phanerozoic · Cenozoic · Quaternary · Holocene · Meghalayan

Clair Patterson measured lead isotopes in meteorites, and in deep-ocean sediment standing in for the planet as a whole, and got 4.55 billion years, on the argument that the Earth and the meteorites formed from the same material at the same time. Getting a clean measurement meant first getting rid of the lead that leaded petrol had spread over everything, including his own laboratory, which is how a geochemist ended up spending the rest of his career fighting the fuel industry.

Why it matters

This is the number the whole timeline is drawn to: the left edge of the frieze is Patterson's measurement, and sixty years of refinement have moved it by less than one per cent. It is also a reminder that the instrument is part of the world it measures. He could not read the age of the Earth until he had subtracted us from it.

Dating & uncertainty

The figure of 4.55 billion years came from lead isotopes in meteorites, on the argument that Earth and the meteorites formed from the same material at the same time. Sixty years of refinement have moved it by less than one percent.

Sources

1. Patterson (1956), Geochimica et Cosmochimica Acta · Age of meteorites and the Earth
2. Halliday & Canup (2022), Nature Reviews Earth & Environment · The accretion of planet Earth

Earth history as one day

23:59:59.99871.3 ms before midnight

if Earth’s 4.54 billion years were compressed into a single day