Carbon Dating
RADIOCARBON DATING (or carbon-14 dating) is one of archaeology's most powerful tools. It measures how much CARBON-14 — a radioactive form of carbon — remains in organic material (wood, bone, cloth, charcoal). Living things absorb C-14 from the atmosphere. When they die, intake stops and the C-14 starts decaying at a known rate (half-life ~5,730 years).
The math. After 5,730 years, half the C-14 is gone. After ~11,460 years, three-quarters is gone. After ~23,000 years, nearly 95% is gone. By measuring REMAINING C-14, scientists calculate the age. The technique works for organic material up to about 50,000 years old. Beyond that, too little C-14 remains. For older fossils, OTHER radioactive isotopes (potassium-argon, uranium-lead) extend the technique to billions of years.
You find a wooden bowl. Carbon-14 testing shows it has 1/4 of the original C-14 remaining. About how old is it?
Limitations. Carbon dating ONLY works on once-living things (organic). Stone, metal, glass need different methods. Contamination (modern carbon mixed in) can skew results. Calibration curves correct for atmospheric variations. Despite limits, C-14 dating revolutionized archaeology — making it possible to date sites accurately for the first time.
Pick a Find
Research a famous carbon-dated artifact — Otzi the Iceman, the Shroud of Turin, Dead Sea Scrolls. What did C-14 dating reveal? Did results surprise scientists?
Carbon dating is one of the most beautiful applications of physics to archaeology. Atomic decay becomes a clock for human history.
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