Minor nit pick here, but carbon dating is not used to date fossils and rocks because C14 has a half-life of only ~5k years. With such a short half-life, the C14

Minor nit pick here, but carbon dating is not used to date fossils and rocks because C14 has a half-life of only ~5k years. With such a short half-life, the C14 all decays away to trace levels in only a few tens of thousands of years. Other radioactive isotopes with much longer half-lives are more appropriate for geologic dating. The U-Pb system is really good for most geologic applications.