In addition to his well-known works in astronomy, Claudius Ptolemy was important in the history of geography and cartography (making maps). He was influential up to the 16th century. Then his ideas were disproved by Nicolaus Copernicus. Ptolemy knew that the Earth is a sphere. Ptolemy's is the first known projection of the sphere onto a plane. His "Geography" remained the main work on the subject until the time of Christopher Columbus. But he had Asia extending much too far east, which may have been a factor in Columbus's decision to try to reach India by sailing west from Europe.