What isotopes are used for radioactive dating
Scientists look at half-life decay rates of radioactive isotopes to estimate when a particular atom might decay.
A useful application of half-lives is radioactive dating.
Many rocks and organisms contain radioactive isotopes, such as U-235 and C-14.
The realisation that radioactive materials emit rays indicated a constant change of those materials from one element to another.
It might take a millisecond, or it might take a century. But if you have a large enough sample, a pattern begins to emerge.