Geochronology is the science of determining the age of rocks, minerals, fossils, and geologic events. It uses both absolute dating methods, such as radiometric decay, and relative dating principles to build a timeline of Earth’s history. By establishing when events like mountain building, volcanic eruptions, or mass extinctions occurred, geochronology provides the chronological framework that underpins all of geology. Geochronology’s main controversies center on debates over dating accuracy, especially when different radiometric methods yield conflicting ages for the same rock or event. Some critics also challenge the assumptions behind decay constants or closed‑system behavior, leading to ongoing scientific discussion about how best to refine and calibrate Earth’s deep‑time timeline.