Radiohiilimenetelmä

Radiohiilimenetelmä, also known as radiocarbon dating, is a scientific method used to determine the age of organic materials. It is based on the measurement of the remaining amount of the radioactive isotope carbon-14 (¹⁴C) in a sample.

Carbon-14 is produced naturally in the Earth's upper atmosphere when cosmic rays interact with nitrogen atoms. This ¹⁴C then oxidizes to carbon dioxide and is incorporated into plants through photosynthesis. Animals consume plants or other animals that have eaten plants, thus acquiring ¹⁴C into their own tissues. While an organism is alive, it continuously exchanges carbon with its environment, maintaining a relatively constant ratio of ¹⁴C to stable isotopes of carbon (¹²C and ¹³C).

When an organism dies, this exchange stops. Carbon-14 is radioactive and decays back into nitrogen-14 with a known half-life of approximately 5,730 years. This means that after 5,730 years, half of the original ¹⁴C in the sample will have decayed. Over time, the amount of ¹⁴C in the dead organism decreases, while the amount of stable carbon isotopes remains constant.

By measuring the ratio of ¹⁴C to ¹²C in a sample and comparing it to the ratio in a living organism or the atmosphere, scientists can calculate how much time has passed since the organism died. This method is effective for dating materials up to around 50,000 years old, after which the amount of remaining ¹⁴C becomes too small to measure accurately. Radiohiilimenetelmä has been crucial in fields such as archaeology, paleontology, and geology for establishing timelines of past events.