How Does Radiocarbon Dating Work? - Instant Egghead #28

Radiocarbon Dating

Radiocarbon dating estimates the age of once-living material by comparing its carbon-14 to carbon-12. Living organisms take in carbon while alive. After death, they stop replenishing carbon-14, which decays into nitrogen. Carbon-12 remains comparatively stable, so the changing ratio provides an estimate of the time since death.

• Carbon-12 has six protons and six neutrons; carbon-14 has six protons and eight neutrons.
• Carbon-14 forms in the atmosphere when cosmic rays cause nitrogen atoms to become carbon-14.
• Carbon-14 has a half-life of about 5,730 years: roughly half decays after one half-life, a quarter remains after two, and an eighth remains after three.
• Radiocarbon dating works for material up to about 60,000 years old. For older material, scientists use other unstable elements with longer half-lives.

Featured presenter/source: Michael Moyer, Scientific American.