Use of ancient lead in modern physics experiments ignites debate

Physicists and archaeologists are at odds over the use in contemporary experiments in particle physics of lead recovered from ancient shipwrecks. Scientists from a dark matter detection project in Minnesota and from a neutrino observatory in Italy have begun to use the specimens, but archaeologists have raised alarm about what they say is the destruction of cultural heritage artifacts. More than 100 lead ingots from a Roman ship recovered in the waters off Sardinia have been used to build the advanced detector of neutrinos -- almost weightless subatomic particles -- in Italy. Lead ingots recovered from an 18th century shipwreck off the French coast have found their way into dark matter detector located in a mine in Minnesota. Why the desire for ancient lead in modern experiments? "Roman lead is essential for conducting these experiments because it offers purity and such low levels of radioactivity -- all the more so the longer it has spent underwater -- which current methods for producing this metal cannot reach," underwater heritage expert Elena Perez-Alvaro from the University of Birmingham said. "Lead extracted today is naturally contaminated with the isotope Pb-210, which prevents it from being used as shielding for particle detectors," physicist Fernando Gonzalez Zalba from the University of Cambridge said. The two researchers, writing in the journal Rosetta, address the dilemma: Should we sacrifice part of our cultural heritage to achieve greater knowledge of the universe? "Underwater archaeologists see destruction of heritage as a loss of our past, our history, whilst physicists support basic research to look for answers we do not yet have," said Perez-Alvaro, "although this has led to situations in which, for example, private companies ... trade lead recovered from sunken ships." Perez-Alvaro and Zalba say they encourage dialogue between both disciplines, and call for legislation that regulates such activities without limiting them exclusively to archaeologists, and to allow use by physicists. "Recovery for knowledge in both fields, and not merely for commercial reasons," they stress.