Talk:Radiocarbon 14 dating of the Shroud of Turin/May2012Version

The Shroud of Turin, a linen cloth commonly associated with the crucifixion and burial of Jesus Christ, has undergone numerous scientific tests, the most notable of which is radiocarbon dating, in an attempt to determine the relic's authenticity. In 1988, researchers at three separate laboratories dated samples from the Shroud to a range of 1260–1390 CE, providing "conclusive evidence that the linen of the Shroud of Turin is mediaeval".

Once generally accepted by the scientific community by those who consider the shroud to be inauthentic, and by some members of the Catholic Church, these results have since been questioned in peer-reviewed journals by Raymond Rogers in Thermochimica Acta and by M.Sue Benford and Joseph G. Marino in Chemistry Today. Criticisms have been raised about aspects of the study as doubts were raised regarding the original nature of the sample that was taken for testing, not the quality of the radiocarbon testing itself.

History

1978: the creation of S.Tu.R.P.

The idea of scientifically dating the shroud had first been proposed in the 1960s, but permission had been refused because the procedure would have required the destruction of too much fabric (almost 0.05 sq m ≅ 0.538 sq ft). The development in the 1970s of new techniques for radio-carbon dating, which required lower quantities of source material, prompted the Catholic Church to found the Shroud of Turin Research Project (S.Tu.R.P.), which involved about 30 scientists of various religious faiths, including non-Christians.

The S.Tu.R.P. group initially planned to conduct a range of different studies on the cloth, including radio-carbon dating. A commission headed by chemist Robert H. Dinegar and physicist Harry E. Gove consulted numerous laboratories which were able at the time (1982) to carbon-date small fabric samples. The six labs that showed interest in performing the procedure fell into two categories, according to the method they utilised:

• Two used a proportional counter approach:
  • Brookhaven National Laboratory, Upton, New York, USA:-
  • Atomic Energy Research Establishment, Harwell, Oxfordshire, UK;
• Four used accelerator mass spectrometry:
  • the Rochester laboratory, New York, USA;
  • the University of Oxford, UK;
  • University of Arizona, Tucson, Arizona, USA;
  • ETH Zurich, Switzerland.

To obtain independent and replicable results, and to avoid conflict between the laboratories, it was decided to let all interested laboratories perform the tests at the same time.

The 1985 rift between S.Tu.R.P. and the candidate labs

In 1982, the S.Tu.R.P. group published the list of tests to be performed on the shroud; these aimed to identify how the image was impressed onto the cloth, to verify the relic's purported origin, and to identify better-suited conservation methods. However, a disagreement between the S.Tu.R.P. group and the candidate laboratories devolved into a P.R. rift: the S.Tu.R.P. group expected to perform the radiometric examination under its own aegis and after the other examinations had been completed, while the laboratories considered radio-carbon dating to be the priority test, which should be completed at the detriment of other tests, if necessary.

During a conference on radio-carbon dating in Trondheim in 1985, representatives from all candidate laboratories jointly announced the end of collaboration with the S.Tu.R.P. group, and proposed an alternative program:

• the British Museum would direct the protocol;
• the S.Tu.R.P. group would only be responsible for sampling the shroud and other (undisclosed) similar objects—a process which would yield actual and "control" shroud samples;
• all samples would be provided in such a way as to be unidentifiable, with only the British Museum knowing which samples were from the shroud and which were from a control object;
• the laboratories would be given samples by the British Museum and would conduct carbon-dating analyses; they must not reveal the dating to anyone but the co-director of the British Museum, Michael Tite;
• the laboratories would be free to perform the prescribed carbon-dating test, along with any other test they elected to, following the method of their choice;
• the results would be communicated to the Vatican before publication.

Carlos Chagas Filho, neurologist and president of the Pontifical Academy of Sciences, reluctantly approved the protocol, which effectively excluded the S.Tu.R.P group from the dating project after the sampling phase.

The "Turin protocol of 1986"

A meeting with ecclesiastic authorities took place on September 29, 1986 to determine which of the two protocols would be implemented - the original proposed by S.Tu.R.P. or that put forth by the laboratories. In the end, a compromise solution was reached with the so-called "Turin protocol", which stated that:

• carbon-dating would be the only test performed;
• original and control samples, indistinguishable from each other, would be provided (blind test);
• the test would be performed concurrently by seven laboratories, under the joint supervision of the Pontifical Academy of Science, the archbishop of Turin, and the British Museum;
• both dating methods would be adopted;
• the sample offered to each laboratory would weight 28 mg, equivalent to 9 sq. cm. of cloth;
• the British Museum would manage the distribution of the samples;
• laboratories would not communicate with each other during the analysis, nor divulge the results of the tests to anyone but the three supervising authorities.

The protocol was, in fact, violated by the Vatican on at least four counts:

• On April 27, 1987 a Vatican spokesperson announced to the newspaper La Stampa that the procedure would likely be performed by two or three laboratories at most;
• On October 10, cardinal Anastasio Ballestrero officially announced to the seven laboratories that only three of them, namely Oxford, Tucson and Zurich, would be provided with samples taken from the same zone of the Shroud. The British Museum would not provide each laboratory with three samples (one from the Shroud and two control samples);
• The sole supervising institution would end up being the British Museum, headed by Michael Tite;
• The proportional counter method would not be used because this method would require too much Shroud material (gram quantities rather than milligram quantities).

These deviations were heavily criticized. Professor Harry Gove, director of Rochester's laboratory (one of the four not selected by the Vatican), argued in an open letter published in Nature that discarding the blind-test method would expose the results - whatever they may be - to suspicion of unreliability. It remains unclear why the protocol was changed after its public adoption; unofficially, it was suggested that the Church may have wanted to reduce the amount of Shroud material to be removed.

In the heated debate that followed, a Church's spokesperson declared that

(t)he Church must respond to the challenge of those who want it to stop the process, who would want us to show that the Church fears the science.
We are faced with actual blackmail: unless we accept the conditions imposed by the laboratories, they will start a marketing campaign of accusations against the Church, which they will portray as scared of the truth and enemy of science. [...]
The pressure on the ecclesiastic authorities to accept the Turin protocol have almost approached illegality.

— Luigi Gonella

The final protocol

The proposed violations to the Turin protocol sparked another acrimonious debate among scientists, so vehement, in fact, that the sampling procedure, scheduled for May 1987, was postponed.

On April 17, 1988, ten years after the S.Tu.R.P. project had been initiated, British Museum scientific director Michael Tite published in Nature the "final" protocol:

• the laboratories at Oxford, Zurich and Tucson would perform the test;
• they would receive one sample weighting 40 mg., sampled from a single portion of weave;
• the laboratories would receive two more samples, clearly distinguishable from the original one—a decision calling on the ethical dependability of the laboratories;
• samples would be delivered to the laboratories' representatives in Turin;
• each test would be filmed;
• there would be no comparison of results (nor communication) between laboratories until the results be certified as definitive, univocal and complete;
• the proportional counter method would not be used because it required gram quantities rather than milligram quantities of shroud material.

Among the most obvious differences between the final version of the protocol and the previous ones stands the decision to sample from a single location on the cloth.

This is particularly significant because, should the chosen portion be not part of the original weave, should it have been contaminated by external agents, or should it be in any way not representative of the remainder of the shroud, the results would only be applicable to that portion of the cloth.

A further, relevant difference was the deletion of the blind test method, considered by most scholars as the very foundation of the scientific method.

Account of the testing process

Sampling (April 1988)

Samples were taken on April 21, 1988 in the Cathedral by Franco Testore, an expert on weaves and fabrics, and by Giovanni Riggi, a representative of the maker of bio-equipment "Numana". Testore performed the weighting operations, while Riggi made the actual cut. Also present were Cardinal Ballestrero, four priests, archdiocese spokesperson Luigi Gonella, photographers, a camera operator, Michael Tite of the British Museum and the labs' representatives (who, according the protocol, should in fact not have been present). As a precautionary measure, a piece twice as big as the one required by the protocol was cut from the Shroud; it measured 81 x 21 mm. A strip showing coloured filaments of uncertain origin was discarded. The remaining sample, measuring 81 x 16 mm and weighing 300 mg, was first divided in two equal parts, one of which was cut into three segments. The unused half was preserved in a sealed container, in case of future need. The labs were also each given three control samples (one more than those originally stated), that were:

• a fragment of weave coming from an Egyptian burial, discovered in 1964 and already carbon-dated to 1100 A.D.;
• a piece of mummy bandage carbon-dated to 200 A.D.;
• a sample of the cloak having belonged to Louis IX of France and preserved in Saint Maximin, Var, France, which had a verifiable provenance and was woven between 1240 and 1270.

The original and control pieces were placed in twelve identical metal cylinders, which allowed the labs to perform a blind test (again, contrary to the set protocol). However the dating of the control pieces, originally set to remain unknown, was published by Vatican daily newspaper Osservatore Romano on April 23. This "leak", along with the violations to the protocol, marred the credibility of this phase of the procedure and fed suspicions of tampering. The blind tests were called a "staging" by Evin and a "façade for public opinion" by Tite.

May–August 1988

In yet another violation of the agreed protocol, the labs did not work separately and simultaneously. Rather, Tucson performed the tests in May, Zurich in June, and Oxford in August, exchanging information in the meantime. The newspaper Avvenire published on October 14 a report that the directors of the three labs had secretly met in Switzerland, which allegation was later confirmed by the directors. On May 18 a BBC crew was allowed into the Zurich lab to film the opening of the cylinders and mentioned once again the dating of the control samples. The reportage, broadcast in late July, asserted that the shroud was, in fact, medieval, before tests had begun at the lab at Oxford. On August 26, news of the shroud having been dated to 1350 was leaked to the British newspaper Evening Standard, which published an article on the subject.

Official announcement

On September 28, 1988, British Museum director and coordinator of the study Michael Tite communicated the official results to the Diocese of Turin and to the Holy See. In a well-attended press conference on October 13, Cardinal Ballastrero announced the official results, i.e. that radio-carbon testing dated the shroud to a date of 1260-1390 CE, with 95% confidence. The official and complete report on the experiment was published in Nature. The uncalibrated dates from the individual laboratories, with 1-sigma errors (68% confidence), were as follows:

• Tucson: 646 ± 31 years;
• Oxford: 750 ± 30 years,
• Zurich: 676 ± 24 years old
• the weighted mean was 689 ± 16 years, which corresponds to calibrated ages of CE 1273-1288 with 68% confidence, and CE 1262-1384 with 95% confidence.

As reported in Nature, Professor Bray of the Instituto di Metrologia 'G. Colonetti', Turin, "confirmed that the results of the three laboratories were mutually compatible, and that, on the evidence submitted, none of the mean results was questionable."

Critical approach

Chemical properties of the sample site

One argument against the results of the radiocarbon tests was made in a study by Anna Arnoldi of the University of Milan and Raymond Rogers, retired Fellow of the University of California Los Alamos National Laboratory. In an interview with Harry Gove, Gove acknowledges that bacterial contamination, which was unknown during the 1988 testing, would render the tests inaccurate, although he also acknowledged that the samples had been carefully cleaned with strong chemicals before testing. By ultraviolet photography and spectral analysis they determined that the area of the shroud chosen for the test samples differs chemically from the rest of the cloth. They cite the presence of Madder-root dye and aluminum-oxide mordant (a dye-fixing agent) specifically in that corner of the shroud and conclude that this part of the cloth may have been mended at some point in its history.

In 1994, J. A. Christen applied a strong statistical test to the radiocarbon data and concludes that the given age for the shroud is, from a statistical point of view, correct. To the contrary Raymond Rogers' 20 January 2005 paper in the scientific journal Thermochimica Acta argues that the sample cut from the shroud in 1988 was not representative. Rogers concludes, based upon the vanillin loss, that the shroud is between 1,300 and 3,000 years old. Rogers said: "The fact that vanillin cannot be detected in the lignin on shroud fibers, Dead Sea scrolls linen, and other very old linens indicate that the shroud is quite old. A determination of the kinetics of vanillin loss suggest the shroud is between 1300- and 3000-years old. Even allowing for errors in the measurements and assumptions about storage conditions, the cloth is unlikely to be as young as 840 years"

The shroud was also damaged by a fire in the Late Middle Ages which could have added carbon material to the cloth, resulting in a higher radiocarbon content and a later calculated age. This analysis itself is questioned by skeptics such as Joe Nickell, who reasons that the conclusions of the author, Raymond Rogers, result from "starting with the desired conclusion and working backward to the evidence". Former Nature editor Philip Ball has said that the idea that Rogers steered his study to a preconceived conclusion is "unfair" and Rogers "has a history of respectable work".

However, the 2008 research at the Oxford Radiocarbon Accelerator Unit may revise the 1260–1390 dating toward which it originally contributed, leading its director Christopher Ramsey to call the scientific community to probe anew the authenticity of the Shroud. "With the radiocarbon measurements and with all of the other evidence which we have about the Shroud, there does seem to be a conflict in the interpretation of the different evidence" Ramsey said to BBC News in 2008, after the new research emerged. Ramsey had stressed that he would be surprised if the 1988 tests were shown to be far off, let alone "a thousand years wrong" but said that he would keep an open mind.

In 2008, an article by Sue Benford and Joseph Marino, based on x-ray analysis of the sample sites and textile analysis, find discrepancies in the radiocarbon dating area. The authors conclude that "the radiocarbon sampling area was manipulated during or after the 16th century".

In November 2008 the University of Arizona announced that Polarized Light Microscopy was used to confirm that "the major fiber content of the sample is linen".

In 2008 in a new documentary a video message from Ray Rogers, who was a director of the Shroud of Turin Research Project, came to light in which Rogers stated that after further study he was convinced that: "The worst possible sample for carbon dating was taken." The video was recorded shortly before Rogers' death in 2005, and in it Rogers states the opinion that after declaring the cloth a fake he was now coming to the conclusion that there was a very good chance that this was the piece of cloth that was used to bury Jesus.

Bacterial residue

A team led by Leoncio A. Garza-Valdes, MD, adjunct professor of microbiology, and Stephen J. Mattingly, PhD, professor of microbiology at the University of Texas at San Antonio have expounded an argument involving bacterial residue on the shroud. There are examples of ancient textiles that have been grossly misdated, especially in the earliest days of radiocarbon testing. Most notable of these is Mummy 1770 of the British Museum, whose bones were dated some 800 to 1000 years earlier than its cloth wrappings. The skewed results were thought to be caused by organic contaminants on the wrappings similar to those proposed for the shroud. Pictorial evidence dating from c. 1690 and 1842 indicates that the corner used for the dating and several similar evenly spaced areas along one edge of the cloth were handled each time the cloth was displayed, the traditional method being for it to be held suspended by a row of five bishops. Wilson and others contend that repeated handling of this kind greatly increased the likelihood of contamination by bacteria and bacterial residue compared to the newly discovered archaeological specimens for which carbon-14 dating was developed. Bacteria and associated residue (bacteria by-products and dead bacteria) carry additional carbon-14 that would skew the radiocarbon date toward the present.

Harry E. Gove of the University of Rochester, the nuclear physicist who designed the particular radiocarbon tests used on the shroud in 1988, stated, "There is a bioplastic coating on some threads, maybe most." If this coating is thick enough, according to Gove, it "would make the fabric sample seem younger than it should be." Skeptics, including Rodger Sparks, a radiocarbon expert from New Zealand, have countered that an error of thirteen centuries stemming from bacterial contamination in the Middle Ages would have required a layer approximately doubling the sample weight. Because such material could be easily detected, fibers from the shroud were examined at the National Science Foundation Mass Spectrometry Center of Excellence at the University of Nebraska. Pyrolysis-mass-spectrometry examination failed to detect any form of bioplastic polymer on fibers from either non-image or image areas of the shroud. Additionally, laser-microprobe Raman analysis at Instruments SA, Inc. in Metuchen, New Jersey, also failed to detect any bioplastic polymer on shroud fibers.

Detailed discussion of carbon-dating

There are two books with detailed treatment of the Shroud's carbon dating, including not only the scientific issues but also the events, personalities and struggles leading up to the sample taking. The books offer opposite views on how the dating should have been conducted, and both are critical of the methodology finally employed.

In Relic, Icon or Hoax? Carbon Dating the Turin Shroud (1996; ISBN 0-7503-0398-0), Harry Gove provides an account with large doses of light humor and heavy vitriol. Particular scorn is poured on STURP (the US scientific team studying the Shroud) and Luigi Gonella, then scientific adviser to the Archbishop of Turin, Cardinal Ballestrero. Gove describes in great detail the mammoth struggle between Prof Carlos Chagas, chairman of the Pontifical Academy of Sciences, and Cardinal Ballestrero, with Gove and Gonella as the main combatants from each side. He provides a detailed record of meetings, telephone conversations, faxes, letters and maneuvers. Gove initially accepted the dating as accurate, but in the epilogue notes that the bioplastic contamination theory seemed to have some evidence to support it.

The Rape of the Turin Shroud by William Meacham (2005; ISBN 1-4116-5769-1) devotes 100 pages to the carbon dating. Meacham is also highly critical of STURP and Gonella, and also of Gove. He describes the planning process from a very different perspective (both he and Gove were invited along with 20 other scholars to a conference in Turin in 1986 to plan the C-14 protocol) and focuses on what he claims was the major flaw in the dating: taking only one sample from the corner of the cloth. Meacham reviews the main scenarios that have been proposed for a possibly incorrect dating, and claims that the result is a "rogue date" because of the sample location and anomalies. He points out that this situation could easily be resolved if the Church authorities would simply allow another sample to be dated, with appropriate laboratory testing for possible embedded contaminants.

Later events

These results, much expected by experts who had written articles on the subject in the press, still surprised many worldwide. The debate remains open between those who, on the basis of these results, have denounced the shroud as a fake and those who challenge the reliability of the results.

Some, as it was to be expected, have adopted conspiracy theory approaches. The events immediately subsequent to the publication of the results were somewhat peculiar. Many of those involved in the procedure, including Michael Tite, seemed to reject or correct the official version they had subscribed to days earlier.

• In a letter to Turin diocese spokesperson Luigi Gonella dated September 14, 1988 (two weeks before communicating the results to the diocese), Tite declared: "personally, I don't believe that radio-carbon dating would demonstrate the shroud is false [...]; it provides no proof in this sense".
• Shroud expert scientist Jacques Evin, a Catholic member of the investigative team that had coordinated the research protocol, suggested that the shroud likely belongs to a man crucified during the Middle Ages.
• The Sunday Telegraph on March 25–26, 1989 published a report alleging that a one-million-pound donation had been made to Oxford University lab by "45 business men as a way of thanking the university labs for having shown that shroud is a medieval fake". The article alleged that the donation was used to fund the new school of Archaeology, whose rectorate had been entrusted to Michael Tite.
• Timothy W. Linick, a 42-year-old researcher at the University of Arizona involved in the analyses performed on the samples, was found dead on June 4, 1989. His death was ascribed to suicide, although mysterious circumstances led to (unproven) allegations of foul play.

Criticisms

In 1993 Dr. Leoncio A. Garza-Valdes discovered the presence of polyhydroxyalkanoate (mcl-PHA)-producing bacteria Leobacillus rubrus on Shroud's fabric and confirmed their presence on three Egyptian mummies. According to Garza-Valdes, "the scientists that carried out the radiocarbon dating of the Shroud of Turin in 1988, were not aware of the presence of this unsuspected contaminant (natural plastic coating)". Garza-Valdes outlines further, that while studying thin sections from the Shroud fibers it was found that "more than 60% of the fibers' area is bioplastic".

The 2008 documentary Sindone, prove a confronto (lit., "The Shroud, comparing evidence") by David Rolfe suggested that the quantity of carbon 14 found on the weave may have been significantly affected by the weather, the conservation methods employed throughout the centuries, as well as the volatile carbon generated by the fire that damaged the shroud while in Savoy custody at Chambéry.

Likewise proposed was a reaction with carbon monoxide (CO), a trace gas present in air. Because of the higher enrichment of atmospheric CO with carbon 14, compared to atmospheric carbon dioxide, contamination by 2% additional carbon molecule derived through reaction with carbon monoxide may in theory suffice to let the shroud appear almost 14 centuries younger than it really is.

The authors of the documentary credit Dr. Christopher Ramsey at Oxford university for this theory, although Dr. Ramsey has since discredited their claim. Carbon monoxide does not undergo significant reactions with linen which could result in an incorporation of a significant number of CO molecules into the cellulose structure.

Some scholars have also suggested that, because the cloth was handled carelessly for centuries, external contamination is virtually guaranteed, and that candle smoke (rich in carbon dioxide) and the volatile carbon molecules produced during the two fires may have altered the carbon content of the cloth, rendering carbon-dating unreliable as a dating tool.

Particularly, they suggest that the silver of the molten reliquiary and the water used to douse the flames may have catalysed the airborne carbon into the cloth.

The Russian Dmitri Kouznetsov, an archaeological biologist and chemist, claimed in 1994 to have managed to experimentally reproduce this purported enrichment of the cloth in ancient weaves, and published numerous articles on the subject between 1994 and 1996.

Kouznetsov's results sparked much interest in the scientific community, but could not be replicated. Professor Gian Marco Rinaldi shocked the academic world by claiming that Kouznetsov never performed the experiments described in his papers, citing non-existent fonts and sources, including the museums from which he claimed to have obtained the samples of ancient weaves on which he performed the experiments. His claims were later substantied by other authors, discrediting Kouznetsov's research altogether.

The Russian was arrested in 1997 on American soil under allegations of accepting bribes by magazine editors to produce manufactured evidence and false reports.

No actual experiments has been able to validate this theory, so far.

While critics have latched on to the above-mentioned protocol violations, they have, most significantly, identified relevant statistical errors in the conclusions published in Nature: the actual standard deviation for the Tucson study was 17 years, not 31, as published; the chi-square distribution value is 8.6 rather than 6.4, and the relative significance level (which measures the reliability of the results) is close to 1% - rather than the published 5%, which is the minimum acceptable threshold.

Conspiracy theorists have proposed that the published results are, in fact, reflective of the control piece dating back from the 14th century, insinuating that the labs would have (perhaps unwittingly) "mixed up" the samples and produced a final report predicated on analyses conducted on the wrong piece of cloth.

More realistically, Joseph G. Marino and M. Sue Benford proposed that the sampled area of the cloth may have been unoriginal (none of the sample contained a "stained" area), as almost 60% of the cloth is because of the progressive repairs throughout the centuries. Scholar Raymond Rogers argued, in a 2005 article, that the chemical analysis he performed confirmed this hypothesis - as the samples used in the carbon-dating show evident traces of tanning products, likely used by medieval weavers to match the colour of the original weave when performing repairs and backing the shroud for additional protection. Others have also presented supporting evidence in this direction.

See also

• Conservation of the Shroud of Turin