Alfred Wegener said the continents move, and for evidence of it happening now he had longitudes. Expeditions had fixed positions on the coast of Greenland across the nineteenth century, and when he set the old numbers side by side the island seemed to be sliding west by something like thirty metres a year. In the 1930s Danish surveyors measured again with better instruments and found the shift was mostly error in the old observations, which were never as exact as he had trusted them to be. The real drift, it turned out decades later, is a couple of centimetres a year, more than a thousand times smaller. So the one measurement he had of the thing moving was wrong, and the thing was moving. He was right about the earth and wrong about his proof, and he died on the Greenland ice in November 1930, before anyone had settled either half.