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Pseudo-Scientists Are Still Trying to Convince You That The Shroud of Turin is Real. Don't Believe Them.


A recent paper by Carpinteri et al. in the journal Meccanica (full reference in margins) demonstrates the two ways that religion is actually a pseudoscience. The first is that it relies on empirical claims to buttress its dogma. While Sophisticated Theologians may argue that God is beyond all evidence, being an imperceptible and indefinable spirit that can neither be defined nor seen as interacting with the cosmos, that’s not what most believers think. So, for instance, claims that Jesus was born of a virgin, died, and was resurrected, or that Mohammad went to heaven on a horse, or that Joseph Smith received the golden plates in New York and translated them into English, or that 75 million years ago Xenu loaded his alien minions onto planes resembling DC-8s, or that there is an afterlife and that good people go to Heaven, or that God hears and answers prayers, or that God is benevolent and all-powerful—these are claims about the way the world is. And many of those claims are testable, though most have been refuted. But the prescientific era, these claims constituted a sort of science—a hypothesis trying to explain how the universe operated. 

But as real science arose in the 15th and 16th centuries and began eroding religion’s claims, religion began transforming into a pseudoscience. That is, it still made empirical claims, but immunized itself against the refutation of those claims using a variety of tricks—the same tricks used by advocates of other pseudosciences like ESP, UFOlogy, homeopathy, and astrology. These include arguing that the propositions themselves cannot be tested, using poor standards of evidence (including reliance on “revelation” as a evidence), reliance on a priori personal biases that are not to be tested but merely confirmed, refusing to consider alternative hypotheses, and engaging in special pleading when religious tenets are disconfirmed.

We can see all of these—but especially in the last—in the paper by A. Carpinteri et al. It’s on the age of the Shroud of Turin, and has gotten a lot of publicity. It’s an attempt to refute scientific radiocarbon dating of the Shroud, which showed it to be a medieval forgery, by special pleading invoking earthquakes.

First, a short review. You almost surely know that the Shroud of Turin is a sheet of linen that reposes behind closed doors in the Cathedral of St. John the Baptist in Turin, Italy. And it bears the likeness of a man who is said to be Jesus. Indeed, the cloth is reputed to be the very burial shroud of Jesus. 

Here’s what it looks like: the image is much clearer in negative form than as a positive. Below is one image of the full the body (pictures from Wikipedia; there are actually two images on the shroud, as if the body had been enfolded): 

Giuseppe Enrie, 1931

The face in negative and positive:

Although scientists and artists aren’t yet sure how the image was made (it appears to include type AB blood, suggesting, since Mary was a virgin, that God carried either an A or a B blood-group allele (or both)). But what is not in serious dispute is that radiocarbon dating of the linen shroud by three independent labs puts its manufacture at between 1000 AD to 1260 AD. In other words, the shroud was medieval, and therefore could not have been Jesus’s burial shroud. There are other problems, too, including the fact that the proportions of the body are simply way out of line for a living human, strongly suggesting that the image is an artistic forgery. 

While religionists have raised numerous reasons why the medieval dating could be wrong—foremost among them is the claim that the dated sample was taken from a piece of cloth used to patch the shroud much later—none of these counterarguments appear credible. The Vatican itself takes no position on the authenticity of the shroud, which of course means that Catholics are free to believe that the shroud could be real.

Science has thus debunked this as Jesus’s shroud. But religionists, in their pseudoscientific way, won’t give up. They have now raised a new ad hoc hypothesis to explain why the dating was wrong—earthquakes! 

To be specific, an earthquake occurring after Jesus’s body was wrapped produced a bunch of neutrons by shaking up the rocks. Those neutrons were captured by nitrogen-14 to produce carbon-14, the parent material used in radiometric dating. (This is in fact how carbon-14 is formed in the atmosphere.) But carbon-14 also decays back to nitrogen by emitting an electron. Carbon 12, the more common isotope of carbon, does not decay. Since a carbon-containing sample will possess, when it is formed or when its possessor died (like an old piece of wood), the same ratio of carbon-14 to carbon-12 present in the atmosphere at the time of manufacture or death, the carbon-14 will gradually decay since no more carbon can be absorbed from the atmosphere. At the end, if we know the rate at which carbon-14 decays (its half-life is 5720 years), we can estimate the age of a sample by simply measuring the ratio of C-14/C-12.

You can see, then, that if a sample were to somehow be able to be infused with extra carbon-14 after it formed, radiometric dating would make it look younger than it really was: for the C-14/C-12 ratio would be abnormally high for a sample of its age. 

And that is what Carpinteri et al. suggest: an earthquake around the supposed time of Jesus’s death (33 A.D.) caused a huge emission of neutrons. Those neutrons were captured by the nitrogen in the shroud, producing a higher level of C-14 than would have been there if the shroud were really made at the time of Jesus. That, in turn, would make the shroud look younger than it really was. In other words, they’re suggesting the original dating was wrong because the assumption that no extra C-14 had gotten into the shroud was violated by a big earthquake. The point of all this, of course, is that the shroud could have been manufactured around 33 A.D.

Oh, and they also suggest that neutron capture, presumably by the body, would have produced the image, though there’s no scientific reason to think that an image could be produced by such a barrage.

Although there is evidence that some earthquakes can transitorily release substantial amounts of neutrons into the atmosphere, there are three scientific problems with the authors’ hypothesis.

1. The evidence for an earthquake is thin. The authors cite four sources. The first is Thallos, a historian in Rome who wrote about 50 A.D., and whose works mention Jesus as well as an earthquake and a solar eclipse that happened during the Crucifixion. This evidence is not credible (there was no solar eclipse then), and Biblical scholars no longer accept Thallos’s quoted words as evidence for the historicity of Jesus.

The second is the Gospel of Matthew, which also mentions an earthquake when Jesus died. Needless to say, this is not independent evidence, and the other Gospels don’t mention such an earthquake. Why not? If it had happened, wouldn’t all the Gospels have mentioned it?

The third source is Joseph of Arimathea, who, according to the Gospels, donated his own future tomb to Jesus. His “narrative,” a non-canonical Gospel that mentions an earthquake, is not accepted by scholars as independent evidence for the historicity of Jesus; indeed, I can find no credible evidence that this Joseph even lived.

Finally, Carpinteri et al. cite, of all sources, Dante’s Inferno (XXI, Canto: 106-114) as mentioning a big earthquake! But who could possibly think that that is independent evidence for an earthquake, since Dante wrote thirteen centuries after Jesus supposedly lived and, of course, based much of his opus on the Bible. The authors, however, fail to cast any doubt on the credibility of their sources.

2. There is no evidence that neutron emission during an earthquake could alter the C-14 content of a shroud. This, of course, could be tested in laboratory experiments, but the authors didn’t do it.

3. The alteration of the amount of C14 in the shroud would have to be sufficient to make it look sufficiently pre-modern, but not too young. In fact, the first accepted mention of the Shroud happens to be 1390, pretty close to the time when it was radiocarbon dated. If there was more C-14 generated by the earthquake, it would make it look like it dated from, say, 1600 or later, which wouldn’t comport with the historical records. So the earthquake managed to give it a false date that happens to correspond to its first mention. That’s too much of a coincidence, and the authors don’t mention this.

4. There is no known way that an earthquake could, by neutron emission, produce an image of a body on a shroud. The authors don’t deal with this, either.

Biblical scholar Richard Carrier has noted three other problems with this hypothesis. An earthquake of the magnitude posited by the authors would have destroyed buildings throughout the eastern Roman Empire, but there is no record of such an event; the amount of neutron radiation required to produce the requisite carbon-14 would have destroyed the entire population of Jerusalem; and, most telling, such an event would have altered the age of every artifact from that era and location, so radiometric dating from Biblical Jerusalem would show everything to be of medieval age. 

The Carpinteri paper is thus a confection of unlikely and untested hypotheses, all assembled to try to save the authenticity of the Shroud of Turin as the burial cloth of Jesus. The paper is not a piece of science but a piece of apologetics.

Nevertheless, it’s been uncritically accepted in some venues. Take a look at the February 11 article in the Telegraph, “Turin Shroud may have been created by earthquake from time of Jesus.” It presents the theory, yet offers not a single piece of counterevidence nor a single dissenting scientist (and there are many), casting doubt on the thesis. This can be attributed to shoddy journalism, to a credulous or lazy journalist (Sarah Knapton), to a desire to placate a public hungry for evidence that Jesus really lived, or all of these factors. What is certain is that the Carpinteri et al. paper is deeply flawed, is not objective science but advocacy, and has been reported uncritically by the press. I’m just a lowly website writer who spent an hour reading the paper and an hour looking stuff up and writing this piece. Why couldn’t Knapton do the same thing?

Indeed, even Wikipedia does a better job than the popular press, and points out something that Ms. Knapton should have known: Carpinteri is the editor of the journal that published this flawed paper. What does that say about the review process? As Wikipedia notes:

A team of researchers from the Politecnico di Torino, led by Professor Alberto Carpinteri (and published in the journal Meccanica, where same Alberto Carpinteri is currently the acting Editor-in-Chief, believe that if a magnitude 8.2 earthquake occurred in Jerusalem in 33 AD, it may have released sufficient radiation to have increased the level of carbon-14 isotopes in the shroud, which could skew carbon dating results, making the shroud appear younger.This hypothesis has been questioned by other scientists, including a radiocarbon-dating expert. The underlying science is widely disputed, and funding for the underlying research has been withdrawn by the Italian government after protests and pressure from more than 1000 Italian and international scientists. Dr REM Hedges, of the Radiocarbon Accelerator Unit of the University of Oxford, states that “the likelihood that [neutron irradiation] influenced the date in the way proposed is in my view so exceedingly remote that it beggars scientific credulity.” Raymond N. Rogers conducted various tests on linen fibers, and concluded that “the current evidence suggests that all radiation-based hypotheses for image formation will ultimately be rejected.”

Of course none of this counterevidence will shake the faithful, who will still see the Shroud as authentic, and will come in droves to pay homage when it has one of its rare showings. Like believers in homeopathy or ESP (or, now, Adam and Eve), they cling to their faith despite all scientific counterevidence. Tellingly, the authors of this paper want to claim the authority of science for their findings—showing that believers indeed get solace when their faith is supported by science—but a true believer could merely claim that the production of the shroud is a miracle not bound by scientific strictures. This is the double-sided logic of faith: when science supposedly supports a religious dogma, the fact is trumpeted to the skies, but when it does not, the science is simply ignored. 

Jerry A. Coyne is a Professor of Ecology and Evolution at The University of Chicago and author of Why Evolution is True, as well as the eponymous websiteThis post originally appeared on the Oxford University Press Blog.