Radiation dating rocks
Radioactive decay is a natural process and comes from the atomic nucleus becoming unstable and releasing bits and pieces.
The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.
Scientists can use certain types of fossils referred to as index fossils to assist in relative dating via correlation.
Index fossils are fossils that are known to only occur within a very specific age range.
Wiens has a Ph D in Physics, with a minor in Geology.
His Ph D thesis was on isotope ratios in meteorites, including surface exposure dating.