The half-life of a radioactive isotope can be used to determine the age of materials through a process called radiometric dating. By measuring the remaining quantity of a radioactive isotope and knowing its half-life—the time it takes for half of the isotope to decay—scientists can estimate how long it has been since the material was formed. This method is widely used in archaeology, geology, and other fields to date ancient artifacts and geological formations, providing valuable insights into past events.