Dating the Shroud of Turin

The Shroud of Turin, which many people believe was used to wrap Christ’s body, bears detailed front and back images of a man who appears to have suffered whipping and crucifixion. It was first displayed at Lirey (France) in the 1350s. After many journeys the shroud was finally brought to Turin in 1578, where later, in 1694, i t was placed in the Royal Chapel of the Turin Cathedral in a specifically designed shrine.

Photography of the shroud by Secondo Pia in 1898 indicated that the image resembled a photographic ‘negative’ and represents the first modern study to determine its origin. Subsequently, the shroud was made available for scientific examination, first in 1969 and 1973 by a committee’ and then again in 1978 by the Shroud of Turin Research Project2. Even for the first investigation, there was a possibility of using radiocarbon dating to determine the age of the linen from which the shroud was woven. The size of the sample then required, however, was about z 500 cm’, which would have resulted in unacceptable damage, and i t was not until the development in the 1970s of accelerator-mass spectrometry techniques (AMS) together with small gas-counting methods (requiring only a few square centimetres) that radiocarbon dating of the shroud became a real possibility.

To confirm the feasibility of dating by these methods an intercomparison, involving four AMS and two small gas-counter radiocarbon laboratories and the dating of three known-age textile samples, was coordinated by the British Museum in 1983.

Following this intercomparison, a meeting was held in Turin over September-October 1986 at which seven radiocarbon laboratories recommended a protocol for dating the shroud. In October 1987, the offers from three AMS laboratories (Arizona, Oxford and Zurich) were selected.

The sampling of the shroud took place in the Sacristy at Turin Cathedral on the morning of 21 April 1988. Three samples, each FZ 50 mg in weight were prepared from the shroud in well prepared and controlled conditions. At the same time, samples weighing 50 mg from two of the three controls were similarly packaged. The three containers, holding the shroud (sample 1) were then handed to representatives of each of the three laboratories together with a sample of the third control (sample 4),which was in the form of threads.

The laboratories were not told which container held the shroud sample. The three laboratories undertook not to compare results until after they had been transmitted to the British Museum. Also, at two laboratories (Oxford and Zurich), after combustion to gas, the samples were recoded so that the staff making the measurements did not know the identity of the samples.

Double Beta-Decay

The first direct evidence of the double beta-decay of a nucleus has been reported by Elliott, Hahn and Moe in the issue of Physical Review Letters. Double beta-decay is an extremely rare process in which two electrons are emitted. Elliott et al observed the decay of ⁸²Se into ⁸²Kr plus two electrons and two electron antineutrinos with a measure of T = 1.1 ^+0.8 _-0.3 x 10²⁰ y, making i t the rarest natural decay process ever observed under laboratory conditions. More details are described in a review article on double beta-decay and in figure 5 b.1 we present the salient features that led to the above decay processes. The captions discuss the most important steps of the experimental set-up, as well as the observed electron energy spectra.

The ultimate goal is to find out if double beta-decay Mithout neutrinos can be observed. Such decay modes would violate lepton-number conservation, one of the few conservation laws thought to be rigidly fulfilled. Lepton number is defined +1 for an electron and neutrino, and -1 for their antiparticles! Therefore, in the standard model of particle physics, the emission of an electron must be accompanied by an antineutrino: the neutrino in this model is called a Dirac neutrino.

There exists a Majorana theory of neutrinos in which the neutrino and antineutrino are the same particle. The only distinction is that neutrinos are left-handed and antineutrinos right-handed. If neutrinos are exactly massless, there is no way to distinguish the Dirac neutrino from the Majorana neutrino. Thus, the observation of neutrinoless beta-decay would not only demonstrate lepton-number non-conservation but would prove that the neutrino's mass is not exactly zero!

The right- and left-handedness of the various beta-decay processes is illustrated in figure 5b.2, and is discussed in the section on parity violation in beta-decay.

The present stage of theory and experiment suggests that if electron neutrinos are Majorana particles, the effective mass is ≲ 1 eV. Now, a direct two-neutrino measurement exists, and as long as the possibility of a measurable neutrino mass exists, the quest for neutrinoless double beta-decay will go on.