The opening of the Indian Ocean was the European’s first world-shaking, world-shaping revision of Ptolemy. The centuries after the closing of the trader’s land routes to the East would revise Ptolemy in countless other ways. Ptolemy’s world, which had terminated at 63 degrees north latitude, about halfway up the Scandinavian peninsula, would have to be extended toward both the north and the northwest. And, of course, a whole New World between Europe and Asia would eventually be added. The scientific spirit of Ptolemy, his admissions of his ignorance, his plea for latitude and longitude, cheered on cartographers and mariners.

“The Portuguese Discoverers”, from “The Discoverers”, Daniel J. Boorstin, The National Board for the Celebration of Portuguese Discoveries, Lisbon, 1987