(h/t +Andreas Schou)
Reshared post from +Gary Ray R
Why Really Old Lead Is Important to Physicists
This is a story about an old Roman shipwreck, its cargo of lead; and why it is important to the study of dark matter.
The shipwreck:
In about 50 AD, a ship set sail from Cadiz in Spain carrying cargo to Italy (probably to Rome). Having passed through the Straits of Gibraltar, the ship hugged the coastline, a course wholly different from the usual open-sea direct course that would normally be taken. The ship sank in 25 m (82 ft) of water not far off the coast of Villajoyosa, about 15 km (9 mi) NE of Alicante in Spain, after perhaps 500 km (300 mi) of sailing. Its cargo included hundreds of amphorae of garum (the Roman version of Worcestershire sauce) and about two thousand bars of lead each weighing about 33 kg (52 lb). When discovered in 2000, the remnants of the 36 m (120 ft) long ship were named the Bou Ferrer shipwreck. ⓐNuclear physicists finance the archeological recovery of the ship.
The expense of examining such a wreck using proper archaeological techniques was considerable. When Ettore Fiorini, a nuclear physicist at the University of Milan-Bicocca, read about the find, he offered the National Archaeological Museum of Cagliari in Sardinia the financial support of the Italian National Institute for Nuclear Physics (INFN) in excavating the vessel and its cargo. In return, a portion of the antique lead (amounting to less than 15 percent, or about 9 metric tons) would be turned over to INFN for use in physics experiments. Archaeological support always being excruciatingly tight, Cagliari agreed to the bargain. ⓐWhy use the old lead.
Why would an expensive archeological shipwreck recovery be financed by nuclear physicists? It was for the 2000 year old lead.
Lead, offering as it does a convenient combination of density and formability, is the first line of defense for radiation shielding. However, newly smelted lead contains a radioactive lead isotope, Pb-210, which is generated in the decay of U-238. While the uranium and other radioactive elements are largely removed during the smelting process, the Pb-210 remains, producing a low-level radioactive decay (about 200 decays per kilogram per second) that restricts the ability of the most sensitive nuclear and particle physics experiments to function. ⓐPb-210, however, has a 22.3 year half-life. When lead bars have lain underwater for 2,000 years, all of the Pb-210 has decayed, leaving "Roman lead" (or old lead) with a radioactive level roughly 100,000 times lower than is found in new lead. ⓐ
The use of old lead for shielding increases the sensitivity of our most delicate experiments by orders of magnitude, an increase that is crucial when looking for a reaction that sheds light on new physics. Lead recovered from roofs, old plumbing, and even stained glass windows has been used, but Roman lead from a shipwreck is the best you can find. ⓐ
The archeologists got the expensive study of the Bou Ferrer shipwreck funded, and the physicists got small portion of the valuable lead to use in the study of dark matter. It was a win win for both branches of science.
Ethical issues
There are ethical issues that arise from the destruction of ancient artifacts for a modern physics study. And scientists on both sides are concerned. University of Birmingham Professor Elena Perez Alvaro, has written a paper on the subject.
Experiments on Particle Physics Using Underwater Cultural Heritage: The Dilemma
He concludes:
The study of sunken vessels is essential to history because entire continents have been discovered, colonized, invaded and defended by sea. The salvage of this material should be done under the surveillance of an archaeological team. ⓑOn the other hand, not so far in the future, the development and operation of new sciences and technologies – make it likely that further investigation, development and use of the underwater cultural heritage for other purposes may occur. If boundaries are not well defined, a “first come, first served” approach may occur. ⓑ
New uses of the oceans and their patrimony have recently been invoked by relevant international law of sea actors and their instruments. It is necessary to identify gaps and suggestions in order to analyse whether and to what extent the existing rules can be applied or modified to adequately deal with these new uses. Compromise does not equal defeat; sometimes, it is the only path to success. Guidelines are necessary ‘for the benefit of humankind’ ⓑ
ⓐ http://www.gizmag.com/relics-physics-archaeology-roman-lead/30032/
ⓑ http://www.rosetta.bham.ac.uk/Colloquium2013/perezalvaro.pdf
Photo: Directorate-General de Cultura, Alicante, Spain
