Carbon dating printing
Common materials for radiocarbon dating are: The radiocarbon formed in the upper atmosphere is mostly in the form of carbon dioxide. Because the carbon present in a plant comes from the atmosphere in this way, the radio of radiocarbon to stable carbon in the plant is virtually the same as that in the atmosphere.
Plant eating animals (herbivores and omnivores) get their carbon by eating plants.
For radiocarbon dating to be possible, the material must once have been part of a living organism.
This means that things like stone, metal and pottery cannot usually be directly dated by this means unless there is some organic material embedded or left as a residue.
Many experts have stood by a 1988 carbon-14 dating of scraps of the cloth carried out by labs in Oxford, Zurich and Arizona that dated it from 1260 to 1390, which, of course, would rule out its used during the time of Christ.
The new test, by scientists at the University of Padua in northern Italy, used the same fibers from the 1988 tests but disputes the findings.
New scientific tests on the Shroud of Turin, which went on display Saturday in a special TV appearance introduced by the Pope, dates the cloth to ancient times, challenging earlier experiments dating it only to the Middle Ages.
The Shroud of Turin, shown in 1979, is a 14-foot linen revered by some as the burial cloth of Jesus.
The dating process is always designed to try to extract the carbon from a sample which is most representative of the original organism.
In general it is always better to date a properly identified single entity (such as a cereal grain or an identified bone) rather than a mixture of unidentified organic remains.
All animals in the food chain, including carnivores, get their carbon indirectly from plant material, even if it is by eating animals which themselves eat plants.
The net effect of this is that all living organisms have the same radiocarbon to stable carbon ratio as the atmosphere.