Radio carbon dating for dummies
For those of you curious as to how scientists figure out the age of ancient artifacts and skeletons, I have put together a simple little article on why carbon dating works.
Carbon comes in two stable non-radioactive isotopes (meaning that it won't radioactively decay) Carbon-12 and Carbon-13. Now when scientists dig up your remains thousands of years later, they can measure the amount of decay of the Carbon-14, and if you have died within the last 60,000 years they can determine the exact time at which you died.
This means that small amounts of Carbon-14 are present in your body whenever you breathe in, or eat.
Carbon-14 unlike Carbon-12 or 13 is unstable and slowly decays into Nitrogen-14 over the course of thousands of years.
An age could be estimated by measuring the amount of carbon-14 present in the sample and comparing this against an internationally used reference standard.
In this method, the carbon 14 content is directly measured relative to the carbon 12 and carbon 13 present. Some inorganic matter, like a shell’s aragonite component, can also be dated as long as the mineral’s formation involved assimilation of carbon 14 in equilibrium with the atmosphere.
A radiocarbon measurement is termed a conventional radiocarbon age (CRA).
The CRA conventions include (a) usage of the Libby half-life, (b) usage of Oxalic Acid I or II or any appropriate secondary standard as the modern radiocarbon standard, (c) correction for sample isotopic fractionation to a normalized or base value of -25.0 per mille relative to the ratio of carbon 12/carbon 13 in the carbonate standard VPDB – Cretaceous belemnite formation at Peedee in South Carolina, (d) zero BP (Before Present) is defined as AD 1950, and (e) the assumption that global radiocarbon levels are constant.
By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known.
It must be noted though that radiocarbon dating results indicate when the organism was alive but not when a material from that organism was used.