The Shroud of Turin remains a mystery: millions of Christians see in the linen, which dimly shows the features of a martyred and crucified man, the shroud of Jesus mentioned in the Bible and thus a first-rate document of his crucifixion and resurrection. For others it is a forgery. Now an Italian physicist has presented a thesis on the origin, which shows a scientific track, but at the same time raises new questions.
Since 1898, the cloth relic, 4.4 meters long and 1.1 meters wide, has been the subject of a debate among researchers. It was then that photographer Secondo Pio discovered that the faint brownish discolorations on the tie in the photo negative showed the plastic image of a crucified man.
Explanations speculated about a lightning or chemical reactions due to decomposition gases. Discussed the possibility of an impression with plaster dust, with a heated or acid-treated relief. It was thought to be a kind of medieval photography, in which a glass plate with the image of the Crucified had been placed on a cloth impregnated with light-sensitive substances, or saw in the cloth the work of a painter genius like Leonardo da Vinci.
On the basis of previous studies, Giulio Fanti, professor of mechanical and thermal measurement in Padua, has listed 24 features that are characteristic of the image of Turin. They include data such as the depth of discoloration (0.2 microns, the outermost layer of a fiber) to the phenomenon that the image appears on the front and back of the fabric.
The majority of the proposed methods, according to Fanti in the "Journal of Imaging Science and Technology", fail in at least one third of the points. Most of the criteria are met by one group of approaches alone: These reckon with an origin by radiation.
Fanti leaves aside those hypotheses according to which the radiant energy came from the man in the shroud itself – "as far as we know, a corpse cannot produce the energy necessary to create an image on a linen fabric". However, two models appear promising: strong electromagnetic radiation, such as that produced by excimer lasers, and the so-called corona effect; the latter could have been triggered, for example, by ball lightning or radon gas escaping during an earthquake.
A strong pulse of electromagnetic waves in the UV range would be able to create an image on a shroud, so to speak, by abruptly aging certain parts of the tie. This would also have all the characteristics of a dead body and would have a 3D effect. The Italian governmental energy research center ENEA has carried out corresponding tests in recent years and achieved remarkable results.
But the main problem is the energy requirement: In the laboratory, such effects can only be achieved with an excimer laser on pieces of material the size of a square centimeter. To create an image of the size of the shroud, 34.000 billion watts, which is well over twice the power currently used on Earth.
Fanti therefore tends to the amption of a corona discharge. This is a phenomenon that occurs in nature as Elmsfeuer and was used in the 80s in plasma lamps for lighting effects at parties. Such an electrical discharge produces UV radiation, heat and ozone. They create aging marks on a fabric that resemble the discolored parts of the shroud.
Fanti was able to produce a corresponding image by holding a hand covered with a cloth on a commercially available plasma lamp.
The only point for which Fanti says experimental proof is lacking is whether the image generation also works with a whole human being. A test would be tricky. Possibly tens of thousands of volts would be needed, plus possibly quantities of radioactive gas as a charge carrier. Perhaps, the researcher concedes, any laboratory experiment would also fail: namely, if the legendary relic were actually "a by-product of the resurrection".