The Voyager Golden Record has a small sample of uranium electroplated onto its cover, put there so that whoever finds it can measure how far the metal has decayed and work out how long the record has been drifting, a built-in clock for a message engineered to last around a billion years. (opens in new tab)

Two identical records left Earth in 1977, one bolted to each Voyager spacecraft. The disc is the part most people picture: gold-plated copper, about thirty centimetres across, assembled by a committee led by Carl Sagan and carrying greetings, music and the sounds of a planet. The cover is the part worth slowing down on. Among […]