A useful application of half-lives is radioactive dating. It takes a certain amount of time for half the atoms in a sample to decay. It then takes the same amount of time for half the remaining radioactive atoms to decay, and the same amount of time for half of those remaining radioactive atoms to decay, and so on.

## How is half-life used in radioactive dating?

Radiometric dating is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes. Each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life or, in other words, the time required for a quantity to fall to half of its starting value.

## How are half-lives used in absolute dating?

The half-life of 238U is 4.5 billion years, i.e., the time it takes for half of the parent isotope atoms to decay into the daughter isotope. This isotope of uranium, 238U, can be used for absolute dating the oldest materials found on Earth, and even meteorites and materials from the earliest events in our solar system.

## How isotope half-lives are used to date materials?

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.