Radioactive dating used for dating the turin shroud
Instruments working at lower energies cannot make such sharp distinctions. Donahue said that in dealing with a postage stamp-size sample from the shroud, the linen was first ''carefully cleaned, using both chemical and mechanical methods.'' Next, the sample was burned in oxygen, thereby converting the carbon in its molecules into carbon dioxide gas.
The gas was then reduced to pure carbon in the form of graphite by heating the gas in the presence of iron powder.
The method developed in the 1940's and was a ground-breaking piece of research that would change dating methods forever. Libby calculated the rate of radioactive decay of the C isotope (4) in carbon black powder.
As a test, the team took samples of acacia wood from two Egyptian Pharaohs and dated them; the results came back to within what was then a reasonable range: 2800BC /- 250 years whereas the earlier independent dates (largely the dendrochronology records) were 2625 /- 75 years (3), (5).
But in the case of the Shroud of Turin, this conventional testing technique would have required the use of relatively large amounts of material, the size of a handkerchief for each laboratory, more than Vatican authorities were willing to allow to be cut from the shroud.Radiocarbon dating may only be used on organic materials.Typically (6): The above list is not exhaustive; most organic material is suitable so long as it is of sufficient age and has not mineralised - dinosaur bones are out as they no longer have any carbon left.The other two isotopes in comparison are more common than carbon-14 in the atmosphere but increase with the burning of fossil fuels making them less reliable for study (2); carbon-14 also increases, but its relative rarity means its increase is negligible. After this point, other Absolute Dating methods may be used.Today, the radiocarbon-14 dating method is used extensively in environmental sciences and in human sciences such as archaeology and anthropology.