The discovery of radioactivity in the late 1800s enabled absolute dating, the assignment of numerical ages to events in the Earth’s history, using decay of unstable radioactive isotopes. Geologic time...The discovery of radioactivity in the late 1800s enabled absolute dating, the assignment of numerical ages to events in the Earth’s history, using decay of unstable radioactive isotopes. Geologic time is vast, providing plenty of time for the evolution of various lifeforms, and some of these have become preserved as fossils that can be used for biostratigraphic correlation.
