sciencehabit writes: Pity the builders of nuclear waste repositories. They have to preserve records of what they've buried and where, not for a few years but for tens of thousands of years, perhaps even millions. Trouble is, no current storage medium lasts that long. Today, Patrick Charton of the French nuclear waste management agency ANDRA presented one possible solution to the problem: a sapphire disk inside which information is engraved using platinum. The prototype shown costs €25,000 to make, but Charton says it will survive for a million years. The aim, Charton says, is to provide "information for future archaeologists." But, he concedes: "We have no idea what language to write it in."