Ian Wilson and Barrie Schwortz on carbon dating
Ian Wilson and Barrie Schwortz on the carbon dating of the Shroud from their book, The Turin Shroud: The Illustrated Evidence:
That high personal respect for the science upon which the dating result had been based was very much my difficulty also. Invented in the 1940s by Chicago physicist Willard F Libby, radiocarbon dating is founded on the principle that all living things, while they are alive, take in the very mildly radioactive isotope carbon 14 which `decays' at a steady rate on death, relative to the stable carbon 12. Libby's achievement was to develop a form of Geiger counter to measure this `decay' in samples of ancient organic material, whether the skin and bones of a body or the flax of linen fabric, and thereby read when the original living organism had died, rather in the manner of reading an atomic clock. Although the need for certain adjustments of this clock became evident when datings of ancient wood samples were checked against tree-ring dating, these re-calibrations have long been routine for every test conducted. Further, the last two decades have seen the invention and development of the accelerator mass spectrometry (AMS) version of radiocarbon dating, which can date samples hundredths of the size originally needed by the Libby method; in the case of linen cloth the size was reduced from pocket handkerchief to fingernail. This, therefore, made it the ideal choice for the Shroud. As a result of its minimally destructive properties AMS has steadily been taking over from its older counterpart, and radiocarbon dating in general has become a thoroughly well-established technology called upon whenever archaeologists around the world seek hard dates for ancient materials that they have unearthed. Indeed, such was my personal confidence in the technique that as long ago as the late 1970s, in my first book on the Shroud, I unequivocally advocated the AMS version of radiocarbon dating, which was then just emerging, for the Shroud. At around this same time I also struck up an amicable acquaintance with some of the leading scientists in the field, among them Dr Bob Otlet of the Atomic Energy Research Establishment (AERE) Harwell, who had done a great deal to refine the Libby `proportional counter' method, Prof. Harry Gove of Rochester, New York, who pioneered the small sample AMS method, Prof. Paul Damon of the Arizona AMS laboratory, Prof. Teddy Hall of the Oxford AMS laboratory and Dr Michael Tite of the British Museum's laboratory. All the last three would ultimately take part in the Shroud carbon dating. During the run-up to the sample-taking for this in April 1988, also during the nail-biting months while the result was awaited, I was in cordial touch with these men, all highly respected, world-class experts in their field. So, when I learnt of their findings, blithely to reject them out of hand because they conflicted with my long-held understanding of the Shroud's date was simply not an option.