Sunday, November 6

The shroud of Turin and other nonsense

Inspired by Exploring the Science of Miracles: Channeling Galileo, an Italian Chemist Conjures Reason to Debunk Myth By Daniel Williams
Luigi Garlaschelli is a chemist who from his perch at Pavia University skeptically eyes Italy's parade of miracles. He belongs to a group called the Italian Committee to Investigate Claims of the Paranormal, made up of Italian scientists, including two Nobel Prize winners, who use science to try to explain the inexplicable.

"Miracles are just paranormal events in religious clothing," he says. "I'm a chemist. I look for the substance behind things." He's not trying to undermine people's religious beliefs, he says, explaining: "We're just trying to study phenomena. If there's a non-miraculous answer, we say so."

These days, he contends, it is more and more important to champion scientific methods in the face of assaults from religious authorities and fundamentalist believers. The attack on Charles Darwin's theory of evolution in the United States by promoters of a rival explanation known as intelligent design is a symptom of the danger, he said. "Science should not be lethargic."


Garlaschelli recently completed a periodic imitation of the miracle of San Gennaro, an event that has been celebrated in Naples since the 14th century. The city's archbishop pulls out a vial containing a maroon-colored solid substance from a case, then rotates and shakes the container until the contents liquefy.

The liquid is said to be the blood of San Gennaro, a pious bishop who was beheaded in A.D. 305 by Diocletian, a Roman emperor. Liquefaction promises a peaceful future for Naples -- a pledge popular with residents of a city that sits in the shadow of Mount Vesuvius. The shaking of San Gennaro's vial draws crowds of frenzied spectators.

Scientific studies of the composition of the substance have not conclusively identified it as blood, though one purported to find traces of hemoglobin. Keepers of the relic have not provided a sample of the material for thorough testing.

Garlaschelli put together a cocktail of material available near Naples -- which would have been obtainable in the Middle Ages -- to try to replicate the miracle. His mixture of limestone powder, iron and pigments was solid when left still, but turned fluid when stirred or shaken. The process is called thixotropy. Ketchup is a thixotropic substance, Garlaschelli explained.


[The shroud of Turin] bears an image of Jesus that believers say was miraculously acquired when the cloth covered his body after the crucifixion. Carbon dating found that the fabric dates from around the 14th century, but defenders say the tests were inaccurate because the cloth could have picked up pollutants in its travels through various European cathedrals.

Garlaschelli runs experiments with a cloth of his own that he thinks provide plenty of reasons for skepticism. For one thing, if the shroud were wrapped around a face, the features should have been distorted, much like the map projection of continents from a globe onto a flat surface -- Greenland appears larger than South America, though in fact it's much smaller. On the shroud, the face is in perfect proportion.

To prove his point, Garlaschelli put a student in a bathing suit, had him lie on a slab, cover himself with paint and then pull a shroud over himself. The image left on the cloth looks similar to the Turin shroud's, except that it has a distorted face.
In the original, "shroud" is capitalized. Not here!

What I learned from the internet:
Substances which are thick like a solid, but which flow like a liquid when a sideways force is applied, are called thixotropic....The opposite of thixotropic is dilantant. These substances get more viscous (even hard) when you apply a force.

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