Carbon dating is a scientific method used to determine the age of once-living things by measuring the amount of carbon-14, a radioactive form of carbon, remaining in their remains. It works because living organisms absorb carbon-14 from the atmosphere or food while alive, and it begins to decay at a known rate after death. By measuring the remaining carbon-14, scientists can estimate how long it has been since the organism died, effective for ages up to about 50,000 years.
Key Notes:
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How Carbon-14 Works:
- Carbon-14 is a rare, radioactive Isotope of carbon present in the atmosphere.
- Living organisms take in carbon-14 through breathing, eating, or photosynthesis, keeping the carbon-14 in their bodies in balance with the environment.
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When Organisms Die:
- The intake of carbon-14 stops.
- Carbon-14 starts decaying into nitrogen-14 at a steady rate (half-life of ~5,730 years).
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Half-Life:
- After 5,730 years, half the original carbon-14 has decayed. This predictable decay allows scientists to date the sample.
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Sources of Carbon-14:
- Plants absorb it directly from the atmosphere.
- Herbivores ingest it by eating plants.
- Carnivores inherit it indirectly through the food chain.
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Applications:
- Used to date fossils, wood, bones, or other organic materials.
- Effective for items up to ~50,000 years old; beyond that, there’s too little carbon-14 left to measure accurately.
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Limitations:
- Only works for once-living materials (not rocks or metals).
- Requires assumptions about the original amount of carbon-14 and constant atmospheric levels, though these are generally well understood.