## Radiocarbon dating

Radioarbon dating (carbon 14 dating, carbon dating) is a scientific method
of calculating the age of carbonaceous material, plant or animal material or
objects made from such material that was at one time living. It is
accomplished by measuring the amount of
carbon 14 (C_{14} remaining in the material.
Carbon 14 is a radioactive isotope that exists in very small amounts in all
living animals and plants. While alive, Animalia, Plantae, Fungi, Protista, Archaea and
Bacteria normally have about one carbon 14 atom for every trillion
carbon atoms. At the moment of death the level of carbon 14 begins to
diminish in a predictable and measurable way.

In 1949, Willard Libby at the University of Chicago calculated that
it in a gram (0.035 oz. U.S.) of carbon there would be 14 disintegrations per
minute in which carbon 14 converted into nitrogen 14. Therefore he reasoned
that a sensitive Geiger counter could be used to determine the age of an object.
Unfortunately, to obtain an accurate measurement, requires a large
sample, which must be incinerated to obtain CO_{2
}gas.

The Shroud of Turin was not a good candidate for Libby’s radiocarbon dating method because a significant part of the Shroud would have been destroyed. But a relatively new method using Accelerator Mass Spectrometry (AMS) permitted testing in 1988 with a very small sample.