Age of Earth

The time elapsed since Earth formed, estimated at about 4.54 billion years. The estimate rests chiefly on radiometric dating of meteorites and ancient terrestrial materials.

Radiometric dating: A method for determining ages from predictable changes in radioactive isotopes within materials. Radioactive decay provides the clocks used to estimate Earth’s formation time.
Solar System formation: The formation of the Sun and orbiting bodies from a collapsing cloud of gas and dust. Earth’s age is tied to the early history of the Solar System.
Clair Cameron Patterson: An American geochemist who used lead isotopes in meteorites to estimate Earth’s age in 1956. His meteorite measurements established the widely accepted estimate near 4.55 billion years.
Acasta Gneiss: A group of ancient rocks in Canada’s Northwest Territories, with dated components around four billion years old. It shows that terrestrial rocks preserve evidence from early in Earth’s history.
Age of the universe: The time elapsed since the universe began expanding from its hot, dense early state, about 13.8 billion years. Earth formed billions of years after the universe began.
Uranium–lead dating: A radiometric dating method that uses uranium isotopes decaying into lead isotopes. Uranium–lead measurements anchor ages for meteorites and the oldest terrestrial minerals.
Meteorite: A fragment of extraterrestrial material that survives passage through a planetary atmosphere and reaches the ground. Many meteorites preserve primitive Solar System material close to Earth’s formation age.
Arthur Holmes: A British geologist who advanced radiometric dating and argued for an ancient Earth. His work made radioactive decay central to geological timescales.
Nuvvuagittuq Greenstone Belt: An ancient rock formation in Quebec whose precise age remains disputed. Its uncertain dating shows why the oldest claimed terrestrial rocks do not define Earth’s formation age.
Geologic time scale: A system that organizes Earth’s history into eons, eras, periods, epochs, and ages. It divides Earth’s 4.54-billion-year history into named intervals rather than measuring its total age.

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