But carbon 14 is extremely rare and extremely unstable, and it decays, slowly, to nitrogen 14, which has a half-life of around 5,730 years. As a result, and depending on how much of the carbon I can detect in a sample in the first place, my experiments can only go back as far as about 40,000 years. After that, kaput. There’s no more carbon 14 left to detect.”
