Originariamente Scritto da sgksgk
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There seems no valid basis to consider claims that have been made to the effect that the radiocarbon date is wrong due to some conspiracy or fraud.
However, there are certain aspects to the procedure carried out which in retrospect could cause doubt to be shed on the results.
Three independent laboratories were used in the carbon dating, all of which used the same procedure9. The labs were sent three samples each—one from the Shroud and two others from cloths with known dates. The dates of the dummy cloth samples were included, although the samples were not identified. All the Shroud samples were cut from the same fragment of the linen. None of the three laboratories carried out a chemical analysis of the samples before they were carbon dated, and as the procedure necessarily destroys the material no chemical analysis was possible afterwards. All three laboratories produced dates consistent with each other. The basis of carbon dating is the radioactive decay of the isotope carbon-14. Living plant matter respires and continually processes carbon from the atmosphere into its structure. As long as the proportion of carbon-14 in the atmosphere remains at predictable levels during extended periods of history (and it remains in balance due to a combination of factors including the production of carbon-14 in the upper atmosphere by cosmic rays), then the amount of carbon-14 in a living plant will be reasonably constant. However, once the plant dies then the decay of carbon-14 alters the ratio between it and other carbon isotopes present in the plant matter’s structure. This provides a means of dating the death of any plant-based material, such as linen.
The carbon dating of Egyptian mummies sometimes throws up some strange results. In the early 1980s samples of Manchester Museum’s Egyptian Mummy no 1770 were given to the British Museum’s radiocarbon dating laboratory. The results suggested that the linen wrappings were 800–1000 years younger than the body (David 1978). More recently, Dr Leoncio Garza-Valdes has suggested that bacteriological contamination can explain some of these dating discrepancies and also lead to a revision of the Shroud result. A coating of live bacteria on cloth wrappings would be processing carbon right up to the dating. In a pilot experiment using the mummy of an Egyptian ibis Garza-Valdes studied the bacteriological film coating the wrappings and predicted that there would be a 500 year discrepancy between the date of the linen and that of the contents. The dates turned out to be 550 years apart. Garza-Valdes has had access to fibres from the Shroud and claims that there are sufficient bacteria there to explain the carbon-14 date. A chemical analysis of the Shroud samples would have revealed the presence of bacteria or other contaminations but, as already noted, this was not done. As is typical with Shroud issues, the bacteriological explanation is disputed. Some scientists have found evidence for live bacteria on Shroud samples, while others claim that the mass of bacteria required to skew the date by 1000 years is unreasonably high. What is clear, however, is that the site of the samples taken for the dating was not judiciously chosen for scientific purposes. It has been pointed out that the region from which the sample was cut corresponds to where the Shroud was frequently lifted and held during exhibitions. Also a large water stain is nearby and it has been suggested that this could have swept carbon residue into the region.
However, there are certain aspects to the procedure carried out which in retrospect could cause doubt to be shed on the results.
Three independent laboratories were used in the carbon dating, all of which used the same procedure9. The labs were sent three samples each—one from the Shroud and two others from cloths with known dates. The dates of the dummy cloth samples were included, although the samples were not identified. All the Shroud samples were cut from the same fragment of the linen. None of the three laboratories carried out a chemical analysis of the samples before they were carbon dated, and as the procedure necessarily destroys the material no chemical analysis was possible afterwards. All three laboratories produced dates consistent with each other. The basis of carbon dating is the radioactive decay of the isotope carbon-14. Living plant matter respires and continually processes carbon from the atmosphere into its structure. As long as the proportion of carbon-14 in the atmosphere remains at predictable levels during extended periods of history (and it remains in balance due to a combination of factors including the production of carbon-14 in the upper atmosphere by cosmic rays), then the amount of carbon-14 in a living plant will be reasonably constant. However, once the plant dies then the decay of carbon-14 alters the ratio between it and other carbon isotopes present in the plant matter’s structure. This provides a means of dating the death of any plant-based material, such as linen.
The carbon dating of Egyptian mummies sometimes throws up some strange results. In the early 1980s samples of Manchester Museum’s Egyptian Mummy no 1770 were given to the British Museum’s radiocarbon dating laboratory. The results suggested that the linen wrappings were 800–1000 years younger than the body (David 1978). More recently, Dr Leoncio Garza-Valdes has suggested that bacteriological contamination can explain some of these dating discrepancies and also lead to a revision of the Shroud result. A coating of live bacteria on cloth wrappings would be processing carbon right up to the dating. In a pilot experiment using the mummy of an Egyptian ibis Garza-Valdes studied the bacteriological film coating the wrappings and predicted that there would be a 500 year discrepancy between the date of the linen and that of the contents. The dates turned out to be 550 years apart. Garza-Valdes has had access to fibres from the Shroud and claims that there are sufficient bacteria there to explain the carbon-14 date. A chemical analysis of the Shroud samples would have revealed the presence of bacteria or other contaminations but, as already noted, this was not done. As is typical with Shroud issues, the bacteriological explanation is disputed. Some scientists have found evidence for live bacteria on Shroud samples, while others claim that the mass of bacteria required to skew the date by 1000 years is unreasonably high. What is clear, however, is that the site of the samples taken for the dating was not judiciously chosen for scientific purposes. It has been pointed out that the region from which the sample was cut corresponds to where the Shroud was frequently lifted and held during exhibitions. Also a large water stain is nearby and it has been suggested that this could have swept carbon residue into the region.
Originariamente Scritto da sgksgk
Originariamente Scritto da sgksgk
Originariamente Scritto da sgksgk
Originariamente Scritto da sgksgk
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