Absolute dating

Absolute dating assigns numerical ages or calendar dates to objects, events, or geological materials, rather than only placing them in sequence.

Radiometric dating: A dating method that calculates age from predictable changes in radioactive isotopes. Radioactive decay provides one of the most widely used clocks for geological materials.
Half-life: The time required for half of the atoms in a radioactive sample to decay. It sets the timescale over which a radioactive isotope can date a sample.
Archaeological chronology: The arrangement of archaeological evidence into a dated sequence of past human activity. Absolute dates connect artifacts and sites to calendar time.
Relative dating: A method that determines whether an object or event is older or younger than another without assigning a numerical age. It orders evidence without supplying the numerical ages that absolute methods seek.
Radiocarbon dating: A method that estimates the age of once-living material from its carbon-14 content. It dates archaeological and environmental remains within a limited recent timescale.
Radioactive decay: The spontaneous transformation of unstable atomic nuclei into more stable nuclei or particles. Radiometric ages rely on decay occurring at a predictable rate.
Geochronology: The science of determining the age and sequence of rocks, fossils, and geological events. Absolute dating supplies numerical ages for geological histories.
Stratigraphy: The study of layered rocks and their relationships through time and space. Layer order establishes relative sequence that numerical dates can anchor.
Dendrochronology: The science of dating and studying trees through patterns in their annual growth rings. Tree-ring sequences can assign calendar years to wood and calibrate other dating methods.
Isotope: One of two or more forms of an element with the same proton number but different neutron numbers. Dating systems distinguish isotopes that decay from those that accumulate.

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