What is radioactive dating used for
When living things die, they stop taking in carbon-14, and the radioactive clock is "set"!
Any dead material incorporated with sedimentary deposits is a possible candidate for carbon-14 dating.
Plants are then eaten by animals, making C-14 a part of the cellular structure of all living things.
As long as an organism is alive, the amount of C-14 in its cellular structure remains constant.
Carbon-14 is a method used for young (less than 50,000 year old) sedimentary rocks.
This method relies on the uptake of a naturally occurring radioactive isotope of carbon, carbon-14 by all living things.
They need to be active long enough to treat the condition, but they should also have a short enough half-life so that they don’t injure healthy cells and organs.
Knowing about half-lives is important because it enables you to determine when a sample of radioactive material is safe to handle.
The rule is that a sample is safe when its radioactivity has dropped below detection limits. So, if radioactive iodine-131 (which has a half-life of 8 days) is injected into the body to treat thyroid cancer, it’ll be “gone” in 10 half-lives, or 80 days.
This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Some do not change with time and form stable isotopes (i.e.
those that form during chemical reactions without breaking down).