Radiocarbon dating refers to a method to determine the age of an object using radiocarbon, a name for the isotope carbon-14.
- The American physical chemist Willard Libby is credited with conceiving the idea of using carbon-14 to date organic materials.
Key points
- Carbon-14 is created in the earth’s atmosphere when cosmic rays slam into the atoms of the gases and release neutrons. When these neutrons interact with the nitrogen-14 nitrogen isotope, they can produce carbon-14.
- Cosmic rays are ceaselessly passing through the earth’s atmosphere, hence carbon-14 is created constantly there.
- Carbon-14 combines with atmospheric oxygen to form radioactive carbon dioxide. This compound then enters the bodies of plants (via photosynthesis), animals (when they consume plants), and other biomass through the carbon cycle.
- When an organic entity (Example: human body) is ‘alive’, it constantly exchanges carbon with its surroundings by breathing, consuming food, defecating, shedding skin, etc. Through these activities, carbon-14 is both lost from the body as well as replenished, so its concentration in the body is nearly constant and in equilibrium with its surroundings.
- When this individual dies, the body no longer performs these activities and the concentration of carbon-14 in the body begins to dwindle through radioactive decay.
- The more time passes, the more the amount of carbon-14 lost, and the less there will remain. This decay rate can be predicted from theory.
- Radiocarbon dating dates an object by measuring the amount of carbon-14 left, which scientists can use to calculate how long ago the body expired.
- Since carbon-14 decays with a half-life (the time taken to decay to half its original mass) of around 5,730 years, its presence can be used to date samples that are around 60 millennia old.
- Beyond that, the concentration of carbon-14 in the sample would have declined by more than 99%.
- One of the instrument to study radioactive decay is Geiger counter. It consists of a Geiger-Muller tube connected to some electronics that interpret and display signals.
- One of the most sensitive dating setups uses accelerator mass spectrometry (AMS), which can work with organic samples as little as 50 mg.
(Source: The Hindu)
