Science meets Religion:   Shroud of Turin

from Overcoming Prejudice in the Evolution Creation Debate by Dr R. Gary Chiang

4.3 The not-so conclusive radiocarbon dating

The easiest way to understand radiocarbon dating is to consider the sand in an hour glass.   When you see all the sand in the bottom compartment, and no sand in the upper compartment of an hourglass, you know that the hour glass was last turned over at least one hour previously.   If, however, you find half the sand in the bottom, and half in the top, and the sand is still flowing, then you can deduce that the glass was inverted 30 minutes previously.   This conclusion is intuitively correct, but if you did not actually observe the hour glass during the last half hour, your conclusion also depends on two assumptions that are not necessarily true.   First, you are assuming that when the hour glass was originally inverted at time zero all the sand was in the top compartment.   That is to say, the hour glass was fully “charged.”   Second, you need to assume that no other sand was added to the upper compartment, or to the lower compartment, so that all the sand in the lower compartment came from the upper compartment once the flow began.   Assuming it takes one hour for all the sand to empty from the top chamber, then stopping the sand at any time and measuring how much is present in the top chamber, or how much has accumulated in the lower chamber, will provide you enough information to determine how long the sand has been flowing.   It will tell you time zero, the time when the hour glass was originally inverted to start the sand flowing.

Radiocarbon dating works on the same principle as an hour glass with the radioactive isotope of carbon (carbon 14) serving as the sands of time in the upper compartment.   Living organisms incorporate radioactive carbon into their bodies until a steady-state is reached so that any living organism has a fixed amount of carbon 14 in it, an amount which is correlated with the amount of carbon 14 in today’s atmosphere.   Assuming that the amount of carbon 14 in the atmosphere has not changed over the eons, the amount of carbon 14 in any living organism at the time of its death can be estimated.   Upon death, no more carbon 14 is being incorporated into the animal, and the carbon 14 in the object begins to diminish like the sand in the upper chamber of an hour glass.   Unlike the hour glass, where sand is collected in the lower chamber, the carbon 14 decays into another element, nitrogen, which is lost from the object.   In an hour glass, it takes 30 minutes for half the sand to move from the top to the bottom of the container.   For a dead organism, it takes approximately 5700 years for half its complement of carbon 14 at the time of death to disappear.   To estimate the age of a onceliving object, radiocarbon dating laboratories use very sophisticated machines to measure extremely small amounts of carbon 14 in these objects.   The amount that is found in the object now is compared to the amount that was suppose to be in the object at the time of its death, and assuming i) that there was a steady loss of carbon 14 and ii) that no new carbon 14 was added since the object died, then the time when the object died can be calculated.

Although the radiocarbon laboratories will give you an estimate of the age of a once-living specimen, the only empirical fact they provide is the amount of carbon 14 present in the sample.   The assumptions that an organism contained a certain amount of carbon 14 at death, and that no other sources of carbon 14 were added to it after its death, are used alongside the rate of decay of carbon 14 to provide an estimate of the age of the material.   Since carbon 14 disappears at a constant rate after death, then the more carbon 14 found in the sample, the younger the sample must be; the less carbon 14 found in the sample, the older the sample must be. If no carbon 14 is found in the sample, then the sample is considered to be millions of years old.

Since the Shroud is made of materials that were once living plants, radiocarbon dating can be applied to the Shroud.   Before 1988, the Shroud had already undergone several forensic tests made by many experts in the field, and each finding supported the belief that this cloth was approximately 2000 yrs old, and that it originated from Israel.   For example, the weaving is distinctive to the time of Christ and microscopic pollen grains found embedded in the cloth are from plants endemic to regions around the Dead Sea.   Supposedly, radiocarbon dating would be able to tell us whether or not the cloth were old enough to have been around at the time of Christ.   If it were significantly younger than expected, this would support the theory that it was not the death shroud of Christ. And if, by chance, this cloth were as young as the Middle Ages, this would confirm the theory that the image was produced by someone using a natural process to help support a fledgling church.

In the winter of 1989, Damon et al. announced to the world the results of the radiocarbon dating.   Their article in Nature stated, “The results provide conclusive evidence that the linen of the Shroud of Turin is Medieval.”

It is interesting that a reputable science journal like Nature would permit any author to claim that his results were conclusive unless one takes into account the deep-seated prejudice that the scientific community has against any theory that is not purely naturalistic.   To claim conclusively that the Shroud is Medieval demonstrates this prejudice and deflects attention from the difficult questions regarding the Shroud’s origin.   The evidence they presented was not conclusive; it was, at best, supportive.   The only definitive conclusion that can be made from this data is that the Shroud has enough carbon 14 in it to suggest that it is relatively young - provided that the assumption concerning the amount of carbon 14 in it to begin with is true, and that carbon 14 was not added after the cloth was made.   To conclude that the Shroud is Medieval is an extrapolation of the facts, and should, in proper science, never be portrayed as "conclusive."   Conclusive proof should be reserved for data that are independent variables free of unprovable assumptions.   The amount of carbon 14 in the cloth, and the rate of decay of carbon 14, are testable variables that can be measured over and over again, but the amount of carbon 14 present in the cloth when it was originally made, and the exclusion of extraneous sources of carbon 14 after death, are assumptions that must be accepted by faith.

Although the popular press never reported any rebuttal of the conclusions of the Nature paper, the journal itself did entertain at least one suggestion in the same issue.  Phillips argued that the interpretation of the radiocarbon dating may have been flawed since an extra source of carbon 14 could have appeared on the cloth as a result of a singular event that occurred at the resurrection.   This argument, of course, assumes that the cloth is authentic, and goes one step further by believing in a resurrection event which produced a burst of energy to form the photographic image on the cloth.   But if such an event occurred, Phillips argued that it could have been associated with the production of extra neutrons which would have bombarded all the atoms in the cloth, not just the carbon.   These extra neutrons would have created new carbon 14 making the cloth appear much younger than it really is.   In order to test this hypothesis, Phillips proposed that the cloth should be measured for the presence of other radioactive isotopes.   If an unusual abundance of other radioactive isotopes were discovered, then the cloth could easily be 2000 years old while appearing only 500 to 700 years old according to radioactive carbon technique.

In his reply to this rebuttal, Hedges, the eleventh author on the 21-authored radiocarbon paper in Nature, stated that such an alteration in the carbon in the cloth may have occurred, and could be measured. Unfortunately, he declined to consider such experimentation because, “If a supernatural explanation is to be proposed, it seems pointless to make any scientific measurement of the shroud at all.”

In essence, Hedges agreed with Phillip’s suggestion that a resurrection event could have increased the amount of radioactive isotopes on the cloth, but argued against carrying out the definitive experiments because of his preconceived belief that the resurrection event could not, and did not, occur.   Since the neutron flux proposed by Phillips would have been produced by a supernatural event, Hedges felt no need to test this hypothesis since divine forces do not exist.   Hedges’ prejudices did not allow him to consider that a neutron flux may have been created by something other than a divine force, such as a natural phenomenon associated with the physical particulars of the cave and/or the interment, or some form of cosmic event.   Hedges’ insistence on relying on radiocarbon dating to discredit the Shroud has prevented him from seizing an opportunity which might have led him to discover some new property in nuclear physics.   His prejudice led to a missed opportunity.

Since the publication of the initial radiocarbon testing, there have been a number of theories proposed to explain why an object which should be 2000 years old could have enough carbon 14 in it to appear only 600 to 700 years old.   These theories have become of greater interest, not because of the Shroud, but because of the radiocarbon dating of other archaeological relics.   Apparently some relics taken from sites known to be thousands of years old have had enough carbon 14 on them to be dated only hundreds of years old.

Of all the theories used to explain the excess carbon 14 in ancient relics, I find that the most compelling one suggests that living microorganisms, such as bacteria, were present on these relics during their history.   As these microorganisms grew and multiplied, they would have incorporated new carbon 14 into themselves, and into their organic wastes.   This process would have resulted in the formation, on the specimen, of a bioplastic coating made up of a transparent layer of microbiological contaminants long after the specimen had died.  In this way, bacteria on the Shroud could have added the excess carbon 14 that caused the Shroud to appear younger than what it truly is. That the Shroud could have had bacteria on it is unquestionable since it has always been touched or stroked or held by human hands, and considering its passage through time, it is unlikely that many of these hands were aseptic.   Furthermore, the Shroud has never been known to have been washed.   Given these conditions, it would seem highly unlikely that bacteria were not alive and well on this relic. To confirm the theory of the presence of extraneous living material on the cloth, the Shroud would need to be examined for the presence of this bioplastic coating.

Unfortunately, the debate over the age of the Shroud has caused some serious concerns regarding the manner by which the Shroud should be revered.   At present all the existing strands of the cloth were ordered returned, and there are no plans to allow the Shroud to undergo any further scientific testing.   Possibly the Roman Catholic Church has grown tired of the exploitation of this relic by the scientific community and is saying to scientists that you can only accept the authenticity of the Shroud by faith, for if it is authentic, science will not beable to confirm it to be the image of Christ.   Unless it is proven a hoax, science will never reach a satisfactory conclusion based on the facts.   As argued by one philosopher of science, maybe “science cannot cope with the Shroud of Turin.”