Renewed Interest in Geography. Some of the early Greeks had studied geography and knew that the world is round; however, in the period of confusion which followed the break-up of the Roman Empire, interest in geographical studies had practically disappeared. Along with the general ignorance which was prevalent in the period, many superstitions concerning geography arose. The Atlantic Ocean was generally thought of as a sea of darkness. Sailors were afraid to get far away from shore; they had heard many strange stories of huge monsters in the ocean, which would destroy their ships; they had heard stories of worms that would bore holes in the hulls of the ships so they would sink; and there were stories about boiling water in the distant ocean.
Most people believed that the earth was flat. Indeed it appeared so, and few had any further knowledge concerning its shape. Sailors reasoned that if they ventured out too far, they would get to the edge of the earth and drop off. To those who maintained that the earth is round, the reply was made that it was impossible for ships to sail up hill; hence they dared not venture out too far. This lack of information was a serious hindrance to exploration.
With the freedom and enlightenment of the Renaissance came a renewed interest in geography. The revival of learning created interest in other parts of the world at a time when the desire for gain through commerce with the distant lands of the East was uppermost in the minds of many people. Some students of geography then maintained that since the earth is round, the wealth of the East could be reached by sailing west. In the meantime, two important instruments had been invented to guide mariners at sea. One of these was the compass, which had been known since the twelfth century. It was a balanced magnetic needle which pointed toward the north, thereby enabling sailors on the ocean to tell the direction in all kinds of weather. The other instrument was the more recently invented astrolabe, which enabled sailors to calculate the altitude of stars, and thus to determine their distance north or south of the equator.