Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Christopher Columbus's efforts to obtain support for his voyages were not hampered by a European belief in a flat Earth. Sailors and navigators of the time knew that the Earth was spherical, but (correctly) disagreed with Columbus's estimate of the distance to India, which was approximately 1/6th of the actual distance. If the Americas did not exist, and had Columbus continued to India, he would have run out of supplies before reaching it at the rate he was traveling. Without the ability to determine longitude at sea, he could not have corrected his error.[clarification needed] This problem remained unsolved until the 18th century, when the lunar distance method emerged in parallel with efforts by inventor John Harrison to create the first marine chronometers. The intellectual class had known that the Earth was spherical since the works of the Greek philosophers Plato and Aristotle. Eratosthenes made a very good estimate of the Earth's diameter in the third century BC. (See also: Myth of the Flat Earth)