Describe how many people believed about placement of land and water on the earth during the 15th century. What did Columbus use to support this idea? (Site 2)

Those who had said that the earth was round were the Greek philosopher Eratosthenes, Posidonius and the Arab Caliph El Ma'mun. Then in the 15th century the roundness of the Earth was already fully accepted by the geographers of the time.

Columbus designed his trip using the calculations of a Greek sage who lived 17 centuries before. His name was Eratosthenes and he deduced at that time that the Earth was a sphere, and even measured its diameter by making calculations from the projection of shadows in different latitudes of the world. Columbus proposed to get from Europe to the east coast of Asia by a shorter route, traveling in the west, a revolutionary idea for a time when security was sailing with the African coast in sight. Columbus left with his 3 caravels and on the way discovered that the doctors had more reason than their optimistic calculations. Therefore, his crew was about to mutiny because the trip was longer than promised. Columbus never reached Asia, but halfway there he found a new continent and this coincidence saved his life and earned him a place in history.