The desire to explore the unknown has been a driving force in human history since the dawn of time. From the earliestdocumented accounts, ancient civilizations have explored the earth by sea. Early adventurers were motivated by religious beliefs, the desire forconquest, the need to establish trade routes, and hunger for gold. Modern history books begin the age of exploration with the fourteenth century, but there is evidence that exploration between Europe and Asia began much earlier. Travel between Greece and India, for instance, was common in Alexander the Great's time because his vast empire included territories of both countries. The Han Dynasty of China and the Roman Empire, likewise, had regular trade relations and even exchanged a few diplomats.