Scratching around in a cave in the middle of nowhere, you find a bone. How do you find out if it’s the remains of an ancient animal that stomped the land tens of thousands of years ago or a discarded scrap from a cooking fire only a few hundred years back?
An archaeologist’s staple is radiocarbon dating: judging the age of an organic sample from its carbon-14 – also known as radiocarbon – content.
Around 99% of carbon on earth is carbon-12 – atoms with six protons and six neutrons in its nucleus. Radiocarbon is an isotope with two extra neutrons, created by cosmic rays interacting with nitrogen in Earth’s atmosphere.