The document summarizes factors that enabled European exploration in the 15th and 16th centuries, including: 1) Economic changes and the development of joint-stock companies provided funding for voyages that would be too expensive for individual sponsors. 2) Knowledge from the Renaissance era, including astronomy and navigation tools like the astrolabe, gave sailors improved abilities to navigate oceans. 3) A new attitude from the Renaissance embraced exploration and the idea that humans could achieve great feats. 4) Existing trade routes with Africa and Asia were costly and dangerous, motivating Portugal and Spain to seek new maritime routes under sponsors like Prince Henry of Portugal.