Carbon dating only works for objects that are younger than about 50,000 years, and most rocks of interest are older than that. Scientists can determine how long ago an organism died by measuring how much carbon-14 is left relative to the carbon-12.

How does carbon dating fossils work?

The Carbon 14 (C-14) dating method is a radiometric dating method. A radiometric dating uses the known rate of decay of radioactive isotopes to date an object. Each radioactive isotope has a known, fixed rate of decay, which we call a half-life. Once C-14 is produced, it starts to decay back to nitrogen.