As European civilization emerged from the Middle Ages, it came into contact with advanced cultures like Arabia and China. These cultures provided the West with scientific knowledge that provoked a new age of learning and exploration. As technology progressed, Renaissance sailors used newfound navigational devices to chart their paths across hitherto uncharted waters.
During the late Middle Ages, mariners used navigational charts known as wind roses that showed the four cardinal directions in which the winds blew. During the 12th century, the magnetic needle was introduced into Europe, allowing sailors like Christopher Columbus to use absolute directions no matter where they were in the world. Over time, sea captains had the idea to combine the wind rose with the magnetic needle, creating the modern compass rose. However, it was some time before the compass was universally accepted among sailors. Some considered its method of finding direction to be akin to witchcraft, though others maintained that the needle formed a cross and was therefore holy. During the time of Columbus, captains were sometimes obliged to conceal their use of the compass, though within the next 100 years its efficiency as an instrument of navigation made it indispensable to sailors.
Advances in Map-making
During the Middle Ages, cartography, the science of map-making, was primitive and inaccurate. Cartographers had filled the margins of their maps with mythical creatures and fantastic locations of legend and theology such as the garden of Eden. However, the rediscovery at the end of the 13th century of the “Geography” of Ptolemy, who had surveyed and charted much of the known world, laid the foundation for a new science of cartography in which locations were mapped according to latitude and longitude. This, combined with the building of swifter, sleeker ships that could make voyages across the ocean in a fraction of the time needed by larger sailing vessels, spurred the exploration of Africa and the East Indies by Spain and Portugal in the 1500s.
As longitude and latitude became instrumental in navigation, the mariner’s astrolabe came into vogue as a tool for measuring latitude. The astrolabe had been used by the Greeks on land for millennia, but during the Renaissance, it was adapted into a seafaring instrument. Sailors held the astrolabe, a circular device, perpendicular to the ocean. The sun or a star would shine through one of the astrolabe’s two pinholes and illuminate the other. This revealed to the user the altitude of the sun or star being measured, which gave him the information he needed to determine the ship’s latitude. The first recorded use of a mariner’s astrolabe took place in 1481 on a Portuguese sailing vessel, and it became a ubiquitous tool of navigation in the following century.
Like the astrolabe, Europeans acquired the quadrant from Arab merchants and explorers who had honed it into a finely tuned mathematical instrument. During the 15th century, the two instruments were typically used together to determine altitude, though the quadrant was the easier to wield for sailors unskilled in mathematics. Demanding the use of two people, it was a semicircular device consisting of a 90-degree scale, a pair of sights and a string fixed with a metallic plumb bob. One sailor observed the sun through the pair of sights while the other sailor noted where the plumb bob fell along the scale; thereby, discerning the sun’s altitude.