The rubidium-strontium method has been a popular method to determine the absolute age of geological processes. When discussing decay rates, scientists refer to “half-lives”—the length of time it takes for one-half of the original atom of the radioactive isotope to decay into an atom of a new isotope.The rubidium-strontium method has been a popular method to determine the absolute age of geological processes. When discussing decay rates, scientists refer to “half-lives”—the length of time it takes for one-half of the original atom of the radioactive isotope

How is half-life used to determine age?

To determine the absolute age of this mineral sample, we simply multiply y (=0.518) times the half life of the parent atom (=2.7 million years). Thus, the absolute age of sample = y * half-life = 0.518 * 2.7 million years = 1.40 million years.