Radioactivity half life carbon dating
For example, uranium-lead dating can be used to find the age of a uranium-containing mineral.
It works because we know the fixed radioactive decay rates of uranium-238, which decays to lead-206, and for uranium-235, which decays to lead-207.
The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.
Because plants use carbon dioxide for photosynthesis, this isotope ends up inside the plant, and because animals eat plants, they get some as well.
When a plant or an animal dies, it stops taking in carbon-14.
When the isotope is halfway to that point, it has reached its half-life.
There are different methods of radiometric dating that will vary due to the type of material that is being dated.