Scientists know the half-life of C-14 (5,730 years), so they can figure out how long ago the organism died.
I also think I would get more pushback of the kind hiring managers sometimes get when we reject an applicant. Part of it is just a difference in conventions — the professional conventions for hiring are different than the conventions for online dating.
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 stuff is important to know when using radioactive isotopes as medical tracers, which are taken into the body to allow doctors to trace a pathway or find a blockage, or in cancer treatments.
Carbon-14 (C-14), a radioactive isotope of carbon, is produced in the upper atmosphere by cosmic radiation.
The primary carbon-containing compound in the atmosphere is carbon dioxide, and a very small amount of carbon dioxide contains C-14.