Why can carbon-14 be used to determine the age of cultural relics?

The age of organic components in artifacts can be determined using carbon-14 (carbon-14), based on radiocarbon dating. Carbon-14 dating is a method used to determine the age of organic matter, based on the natural decay of carbon-14 isotopes. Carbon-14 (^14C) is a radioactive isotope that occurs naturally in the atmosphere in extremely small proportions and is produced by interacting with nitrogen atoms by cosmic rays in the atmosphere. Life on Earth absorbs carbon from the atmosphere, including trace amounts of carbon14, through respiration and the food chain.

When an organism dies, it no longer absorbs new carbon, and the carbon-14 in its body begins to decay. The half-life of carbon-14 is about 5730 years, which means that within 5730 years, half of the original amount of carbon-14 will decay into nitrogen-14. Scientists can calculate the approximate age of a sample by measuring the ratio of the remaining carbon-14 to nitrogen-14 in the sample.

The age of artifacts is usually measured for samples containing organic matter, such as wood, cloth, paper, bones, etc. By comparing the carbon-14 content of these samples with the current carbon-14 levels in the atmosphere, it is possible to estimate when the samples died or stopped absorbing carbon-14, thus knowing the age of the artifact.

Formation and distribution of carbon-14: carbon-14 is a radioactive isotope of carbon, which is naturally generated in the atmosphere through the interaction of cosmic rays with nitrogen, and then enters organisms through photosynthesis, and in living animals and plants, carbon-14 maintains a relatively fixed ratio with the stable isotopes carbon-12 and carbon-13.

Decay after death: After death, the organism no longer obtains new carbon-14 from the outside world due to the cessation of metabolism, while the carbon-14 already present in the organism begins to decay according to its radioactive half-life (about 5730 years). Carbon-14 is converted to nitrogen by β decay.

Ratio change and dating: Over time, the amount of C14 in the sample decreases, while the level of the stable isotope C12 remains constant. By measuring the ratio of remaining carbon-14 to carbon-12 in a sample, scientists can calculate the time that has elapsed since the sample stopped exchanging carbon with the atmosphere, which is the age of the death of organisms or the formation of organic matter.

Application limitations: It should be noted that carbon-14 dating is mainly used for the determination of cultural relics containing organic substances, such as wood, leather, bones, textiles, etc., and is not suitable for cultural relics that do not contain organic components or have long disappeared (such as ceramics, bronzes, stones, etc.). In addition, the effective range of carbon-14 dating is generally limited to a few hundred to hundreds of thousands of years, and it is difficult to accurately measure ancient samples beyond this range because the carbon-14 concentration is too low.

Carbon-14 dating is a very important tool in archaeology, geology, and paleontology, providing valuable information for our understanding of human history and the history of the planet.

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