Ever since the writings of Aristotle and other ancient authors were rediscovered in the 12th century, all educated people knew very well that the world was round. This is clear in, for instance, Dante’s “Divine Comedy”, written almost two centuries before Columbus. Dante even has an understanding of gravity, attracting everything towards the centre of the earth. (Strictly speaking, Dante and other mediaeval writers had no evidence to support this belief in a round earth, but they approached the ancient writers in an entirely uncritical spirit: if Aristotle said so, it had to be true!) One ancient Greek scientist, Eratosthenes of Alexandria, had attempted to measure the size of the earth, and had produced an estimate surprisingly close to the true figure.
Marco Polo’s account of his travels to China in the 13th century was very widely read, and European explorers and traders longed to gain access to the vast riches of the East of which he wrote. But with the arrival of the Turks, the overland route across Central Asia was no longer open. What to do instead? Some of the ancient geographers had believed there was a way south round Africa, from the Atlantic to the Indian Ocean, and for a generation before Columbus Portuguese explorers had been venturing down the west coast of Africa. But what they discovered was that Africa was very much bigger than expected, so that a voyage round the Cape to India and back might take years rather than months. Furthermore, the Portuguese kept their navigation charts top secret, and prevented any other ships from venturing that way.
Columbus therefore had the idea of reaching India and China by sailing westwards across the Atlantic. The trouble was, he grossly overestimated the size of Asia, and he did not believe the ancient Greek calculations of the size of the earth: he thought it was much smaller! He therefore believed that the coast of China lay approximately at the position of Kansas City, in terms of distance. He spent years attempting to get one of the kings of Europe (including Henry VII of England) to sponsor his voyage. The reason his efforts were fruitless for so long was nothing to do with a belief the world was flat. What happened instead was that the kings would consult their learned men, who would say, “This fellow Columbus doesn’t know what he’s talking about! The world is much bigger than he thinks, and China is much further away - so far away, in fact, that no ship can carry enough food and water for such a long voyage. Columbus’s crew will all have died of starvation long before they get to China!”
The irony is, of course, that these learned men were quite right: Columbus didn’t know what he was talking about! Eventually Ferdinand and Isabella of Spain thought Columbus was worth a speculative punt, if only to try and outflank the Portuguese.
Although Columbus made four transatlantic voyages altogether, he never realised he had discovered a new continent, but believed he had found the western route to the fabled Indies, and that the coast of China couldn’t be far away. This is why the islands he discovered are still called the West Indies, and the inhabitants of North America were called, until very recently, Red Indians.
On a world map produced in 1507 the new continent was named not after Columbus, but after a slightly later explorer, Amerigo Vespucci; though the reason for this remains unclear. It was left to Magellan, a generation after Columbus, to find a way round South America and across the Pacific to the actual Indies - and, incidentally, to disprove Columbus‘s estimate of the size of the earth.