radíókarbóntímasetningu

Radiocarbon dating, also known as carbon-14 dating, is a method for estimating the age of organic materials by measuring the amount of radiocarbon, carbon-14, remaining in a sample. It was developed by Willard Libby in 1949 and has since become a standard tool in archaeology and earth science.

Principle: Carbon-14 is produced in the atmosphere by cosmic rays and is incorporated into carbon dioxide, which enters the biosphere. Living organisms continuously exchange carbon with their surroundings, so the C-14/C-12 ratio in living tissue matches the atmosphere. After death, exchange stops and C-14 decays to nitrogen-14 with a half-life of about 5,730 years. By comparing the remaining fraction of C-14 to a modern standard, scientists estimate the time since death in radiocarbon years before present (BP), with present defined as 1950 CE.

Methods and calibration: Radiocarbon content can be measured by beta counting or accelerator mass spectrometry (AMS); AMS dominates today because it requires smaller samples and is more precise. Samples undergo pretreatment to remove contaminants; ages are then converted to calendar years using calibration curves (for example IntCal) to account for past fluctuations in atmospheric C-14. Calibrated results are reported as cal BP or cal BCE/CE with uncertainty.

Applications and limitations: Radiocarbon dating is widely used in archaeology, paleoclimatology, and geology. It is suitable for materials up to about 50,000 years old; accuracy is influenced by contamination, sample preservation, and reservoir effects (notably in marine samples, which can appear artificially older). It is not applicable to inorganic materials, and many studies combine radiocarbon dating with other dating methods to improve interpretation.