How many continents are there, by the usual count?

Seven is the answer taught in Britain, the United States, China and Australia. It is not the only answer taught. Much of Latin America and southern Europe teaches six, treating the Americas as one landmass, which they are. Russia, eastern Europe and Japan also often teach six, but by a different merger - Europe and Asia as a single Eurasia. The Olympic rings represent five, leaving out Antarctica as nobody's home.

The disagreement exists because a continent is a cultural unit wearing a geological costume. Europe is not a separate landmass by any physical test; it is the western end of Asia, and the Ural mountains became the boundary largely because an eighteenth-century Swedish officer in Russian service proposed them and the idea suited everybody.

Geology has also been quietly adding to the list. In 2017 a group of researchers made the case that Zealandia - a continental crust of about five million square kilometres that is 94 per cent underwater, with New Zealand and New Caledonia poking above the surface - meets every criterion for a continent except being dry.