In carbon 14 dating
Plants take in carbon dioxide, incorporating in their tissues both carbon-14 (unstable) and normal carbon-12 (stable) in the same proportion as they occur in the atmosphere .
Carbon-14 then moves up the various food chains to enter animal tissueagain, in about the same ratio carbon-14 has with carbon-12 in the atmosphere.
Half of it will decay in about 5,730 years to form nitrogen.
A 10 gram sample of U-238Now that has changed, and some important discoveries are being made.This element is locked in tiny zircons within the granite. While it stays within the zircon for a period of time, being a very small atom, helium escapes the zircon within a few thousand years.When creation scientists studied granite samples, they made interesting discoveries.The samples were from a mile below the earth, which, according to inflated evolutionary years, were 1.5 billion years old.The helium still locked in the samples was studied as well as the rate at which the helium diffused from the rock.