1. Carbon-14 Formation: Carbon-14 (¹⁴C) is a radioactive isotope of carbon that is naturally produced in the Earth's atmosphere by the interaction of cosmic rays with nitrogen atoms.
2. Carbon Absorption: Living organisms, including plants and animals, absorb carbon from the environment, including ¹⁴C, while they are alive. Once an organism dies, it stops exchanging carbon with the atmosphere, and the amount of ¹⁴C within its remains begins to decrease.
3. Radioactive Decay: ¹⁴C decays into nitrogen-14 (¹⁴N) through beta decay with a known half-life of 5,730 years. This means that every 5,730 years, half of the ¹⁴C atoms in a sample will decay into ¹⁴N.
4. Age Calculation: By measuring the amount of ¹⁴C remaining in an organic sample compared to the known levels of ¹⁴C in the atmosphere, scientists can calculate how long ago the organism died. The older the sample, the less ¹⁴C it will contain.
5. Sample Preparation: To determine the age of an artefact using carbon-14 dating, a small sample of organic material is carefully extracted from the artefact. This could be wood, leather, cloth, or any other type of organic material associated with the artefact.
6. Carbon-14 Measurement: The sample is then processed to extract the carbon and measure the concentration of ¹⁴C within it. This can be done using various techniques, such as liquid scintillation counting or accelerator mass spectrometry.
7. Calibration: Carbon-14 dating results are calibrated against known-age reference materials to account for variations in ¹⁴C levels over time due to natural fluctuations in the Earth's atmosphere. Calibration curves help determine the true age of the sample by correcting for these variations.
8. Age Determination: By comparing the measured ¹⁴C concentration in the sample to the calibrated reference curve, scientists can determine the age of the artefact. The resulting age estimate represents the time elapsed since the organism died and stopped exchanging carbon with the atmosphere.
Carbon-14 dating is a valuable tool in archaeology, palaeontology, geology, and other fields that require the dating of organic materials. However, it has certain limitations and is not suitable for materials older than approximately 50,000 years due to the decreasing accuracy of the method. Nevertheless, it remains a fundamental technique for understanding the chronological context of human history and various scientific investigations.