Library of Congress
Loc: Mediterranean World on the Eve of Conquest
The Library of Congress provides an essay on the reasons for exploration during the 15th century.
CK-12 Foundation
Ck 12: Earth Science: Revolutions and Rotations of the Earth Study Guide
[Free Registration/Login may be required to access all resource tools.] Summarizes the key points about how our understanding of the Earth's movements evolved from ancient times and what we know today. Includes some questions to check...