Otzi radiocarbon dating
Through photosynthesis, plants absorb both forms from carbon dioxide in the atmosphere.When an organism dies, it contains a ratio of carbon 14 to carbon 12.Radiocarbon dating, or simply carbon dating, is a technique that uses the decay of carbon 14 to estimate the age of organic materials.This method works effectively up to about 58,000 to 62,000 years.Radiocarbon dating uses isotopes of the element carbon. Cosmic rays – high-energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 isotopes.Because the cosmic ray bombardment is fairly constant, there’s a near-constant level of carbon-14 to carbon-12 ratio in Earth’s atmosphere.Using radiocarbon dating, archaeologists during the past years have been able to obtain a much needed global perspective on the timing of major prehistoric events such as the development of agriculture in various parts of the world.
Here’s an example using the simplest atom, hydrogen. Carbon-14 is an unstable isotope of carbon that will eventually decay at a known rate to become carbon-12.
But when gas exchange is stopped, be it in a particular part of the body like in deposits in bones and teeth, or when the entire organism dies, the ratio of carbon-14 to carbon-12 begins to decrease.
The unstable carbon-14 gradually decays to carbon-12 at a steady rate. Scientists measure the ratio of carbon isotopes to be able to estimate how far back in time a biological sample was active or alive.
As the carbon 14 decays with no possibility of replenishment, the ratio decreases at a regular rate. The measurement of carbon 14 decay provides an indication of the age of any carbon-based material.
Dates may be expressed as either uncalibrated or calibrated years.
This plot shows the level of carbon-14 in the atmosphere as measured in New Zealand (red) and Austria (green), representing the Southern and Northern Hemispheres, respectively.