Carbon 14 is continually being created in the Earth's atmosphere by the interaction of nitrogen and gamma rays from outer space.
One known example where this assumption was used is very misleading.
ANSWER: Relative dating is used to determine the relative ages of geologic strata, artifacts, historical events, etc.
This technique does not give specific ages to items.
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.