Christopher Columbus is an unlikely figure to be considered the discoverer of America and the leading symbol of European exploration overseas. When he made landfall somewhere in the Bahamas on October 12, 1492, he was not the first mariner to have made the crossing from Europe. There are legends of Celtic and Phoenician seafarers making the Atlantic crossing, perhaps blown off course by storms, centuries before Christ. The Navigation of St. Brendan, a tenth-century chronicle recounting the sea journeys of the sixth-century Irish monk in the skin-covered open boats known as curraghs, has him reaching the "land of Promise." Described as vast and temperate, it has been identified speculatively with Florida.
       
       None of this is certain and probably never will be. What is certain now is that the Vikings, whose longboats bore the raiding parties from Scandinavia that terrorized Christian Europe, reached Newfoundland and established a settlement there toward the end of the tenth century. Their land-hopping wanderings took them from Norway to the Faeroe Islands, thence to Iceland, and to Greenland, establishing settlements.
       
       Around the year 1000 Leif Eriksson took a party west and south from Greenland, made landfall in a place they called Vinland, and established a short-lived settlement there. Archaeologists have discovered the remains of Norse longhouses near the northern tip of Newfoundland. The story of the settlement is recorded in the Norse sagas, but that was the only record of their arrival in North America. It was little known beyond Norse society and changed no one's view of the world. Eriksson and his Viking companions had, in other words, no sense of what they had discovered.
       
       By contrast, Columbus was a self-conscious explorer driven by the desire for discovery. He knew what he was looking for--a sea passage that would carry him to the fabled wealth of China by sailing west from Europe. This is not what he found. The irony of his life is that, until the end of his days, he refused to recognize that he had not reached the Orient but had stumbled upon vast lands totally new to the European mind. It was left to others--much later--to appreciate the full significance of the discoveries that he had inadvertently set in motion, and it is not insignificant that the new lands were eventually named America (after a later explorer) rather than Coluia.
       
        Christian Europe emerges
       
        In fact, Columbus and his voyages received little attention from historians for some three hundred years. Since 1792, however, he has been resurrected in a number of guises to serve a variety of causes. For the youthful American republic, he was the lone pioneer who broke with tradition to explore new pathways. That he was not Anglo-Saxon added to his stature as a symbol of American independence.
       
       By 1992 Columbus was reviled as much as he was lauded. Accused of genocide and ecocide, he was labeled the guilty symbol of the excesses, real and imagined, of European conquest and colonization. This Columbus is more myth than history, molded and remolded to reflect the positions of various parties in contemporary cultural debate. Such a depiction has little to do with the Columbus of 1492, who was quintessentially a man of his era.
       
       In hindsight it is clear that the Europe of his time was on the verge of breaking out in new directions. Rivers and seas played a vital role in the earliest civilizations. Egypt was built along the Nile and Babylon between the Tigris and Euphrates. Later, Greek and then Roman civilization centered on the Mediterranean. After the Roman Empire collapsed in the west, the center of gravity shifted north, as Roman Christianity reached out to the Germanic tribes, creating the seed of the future Europe.
       
       The shift away from the Mediterranean was intensified by the appearance of Islam and its whirlwind conquest of the Mediterranean littoral, from Syria in the east across North Africa to Spain in the West, during the hundred years after the Prophet's death in 632. Muslim warriors crossed the Pyrenees into France. Their advance was finally turned back by Charles Martel, grandfather of Charlemagne, at the battle of Poitiers in 732. For centuries, though, the Mediterranean would remain a Muslim lake.
       
       At the start of the millennium, the power, wealth, and learning of Islam far outshone those of its Christian neighbor and rival to the north. Throughout the first half of the millennium Christian Europe gradually reasserted itself against Islam, a process that drew it back toward the Mediterranean. From 1095, the Crusades inspired Europe's feudal knighthood to challenge Muslim supremacy in the eastern Mediterranean by trying to wrest control of Jerusalem and Christianity's holy sites.
       
       In the west, the centuries-long reconquista gradually rolled back the area of Muslim rule. By 1275, only the Muslim kingdom of Granada in the south remained of the Emirate of Cordoba, Islam's great Iberian empire. Granada survived until 1492. It was no coincidence that Queen Isabella's final approval of funds for Columbus' proposed expedition west came shortly after the fall of Granada. Spain was then ready to take on new challenges.
       
        Openings to the Orient
       
        The religious zeal that drew Europe inexorably into the Mediterranean sphere was inextricably mixed with the desire for honor through conquest and for wealth through both conquest and trade. The zeal was not pure certainly, but neither was it insincere. This complex mixture of motives was a feature of Christian Europe's clash with Islam. It drove forward the early voyages of discovery and was part of Columbus himself, shaping his fascinatingly complicated character.
       
       The Italian cities grew rich transporting crusaders to the Levant, supplying them, and shipping back to Europe the silks and spices, ivory, and gold purchased there. They also learned the ways of the sea and produced capable mariners, especially the great trade cities, Genoa and Venice. Much of the wealth traded for in the Levant did not originate there but in Cathay (China) and the Indies. The merchants of Italy were attracted by the prospect of direct trade with those regions.
       
       They got their wish with the help of Genghis Khan. In the first half of the thirteenth century, Mongol horsemen poured out of the steppes of Central Asia and conquered an empire that stretched from Poland to the Pacific and included China. While Mongol conquest was terrifying, Mongol rule opened up the land trade route to China along the old Silk Road and maintained it in peace and stability. For about a hundred years, European traders along this route enjoyed a golden age.
       
       One of them was a young Venetian named Marco Polo who lived in the Far East from 1273 to 1293, serving in the Mongol court of Kublai Khan in China and traveling extensively. He wrote Description of the World as a result of his experiences, including in it an account of the Arab trade network in the Indian Ocean and how Arab sailors planned their voyages to the east and back to coincide with the cycle of the monsoon seasons. His book would have a great influence on Columbus' calculation that he would find the eastern shores of Asia no farther than about three thousand miles west of Europe's Atlantic Coast.
       
       In 1368 ethnic Chinese overthrew Mongol rule and established the Ming dynasty. Its vision of a self-contained Chinese empire put a stop to foreign trade, while also curtailing China's own remarkable maritime expeditions. The disintegration of the Mongol empire made the trade route overland to China too dangerous in any case. European trade, especially that of the Italian city-states, suffered a further setback through the growth in power of the Ottoman Turks from the middle of the fourteenth century. This aggressive Islamic people launched a countercrusade against Christendom, particularly the neighboring Byzantine Empire. In 1453 they conquered Constantinople. With it went the Genoese trading quarter and Genoa's extensive trade on the Black Sea. Venice's trade in the region was also seriously curtailed. Islamic resurgence in the eastern Mediterranean and hostility to Christian traders led Europe to look for alternate routes to the rich spice markets of the Orient.
       
       It also led the mariners of Italy's great trading cities to turn west. Many of them offered their services to the new and growing enterprise of searching for oceanic routes to the East. Columbus was born in Genoa, while Amerigo Vespucci, after whom the newly discovered continents of the West were ultimately named, was a Florentine. John Cabot, who was authorized in 1496 by England's King Henry VII to make a voyage of exploration, hailed from Venice. He reached Newfoundland but, like Columbus, believed he had found a remote shore of China. His voyage launched a long and ultimately fruitless series of expeditions to find the Northwest Passage, around the top of the American continent, to Asia.
       
        Prince Henry the Navigator
       
        As European pioneers began to look outward from the Mediterranean, their conception of the world had to change. In medieval Christian cosmography, the earth was made up of three continents: Asia, Europe, and Africa, arranged with Jerusalem at the center, the meeting point of the three. This world was bounded by the Ocean Sea, conceived as a barrier, a trackless waste. Now the pioneers began to think of the ocean as a potentially navigable pathway to desirable destinations.
       
       Yet these pioneers were still animated by the attitudes of the Crusades and the reconquista. Columbus hoped to gain titles and personal wealth through his voyages, but he also envisioned that the riches he dreamed of finding would be used to fund a new crusade to liberate Jerusalem from the Muslims. The leader and guiding spirit of Portugal's oceanic explorations, Prince Henry the Navigator, began his career by overseeing the construction of a fleet and leading it on a crusade against the Muslim fortress and trading center of Ceuta on the African coast, across the Straits of Gibraltar.
       
       Prince Henry wanted to continue his career as a crusader by assaulting the formidable Islamic stronghold of Gibraltar. His father, King John I of Portugal, vetoed the idea. Prince Henry was not pleased. He abandoned the court in Lisbon and took up residence in Lagos (after which the present capital of Nigeria is named) in southern Portugal. It was just a few miles from Cape St. Vincent, the southwestern tip of Portugal, known as the "street corner of Europe." All the vessels headed from the Mediterranean to northern Europe or voyaging south from there had to weather Cape St. Vincent. Its flat, barren surface and sheer cliffs leave a stark impression as it juts out boldly from the land toward the southwest, the direction Prince Henry's captains followed in their exploration of West Africa.
       
       In the nearby village of Sagres, Prince Henry established a center where he redirected his thwarted crusading zeal to the enterprise of maritime exploration. The center is known by history as the "School of Navigators," though it was not a school in any usual sense. To be there, you had to know what you were doing. From there the expeditions south along the African coast were sent out year after year. Information was gathered, and practical experimentation in shipbuilding and navigational techniques were coordinated to support the voyages.
       
       Consistently supported with royal leadership and funding and the input of groups of experts, this was the first really modern research enterprise conducted on a national scale. If anyone should be a symbol of the start of the age of exploration, it should be Prince Henry the Navigator.
       
       He gathered expert mapmakers at Sagres, including Jehuda Cresques, a Catalan Jew driven from Aragon by Spanish Christian persecution. He was the son of Abraham Cresques, the maker of the famous Catalan Atlas of 1375, which incorporated knowledge of China from Marco Polo's writings for the first time. Portugal was to profit greatly in this period from Jewish scholars skilled in mathematics and astronomy who had been expelled from Spain.
       
       Cresques coordinated the mapmaking at Sagres. The use of portolani, or pilots' maps, was already well established both in the Mediterranean and northern Europe. These maps charted coastlines in great and accurate detail, with distances to scale and compass directions from major navigational features indicated. These were the sailor's practical aids, an early example of the empirical spirit applied systematically. The Portuguese added meridians of latitude and longitude to such charts. They also had their captains bring back accurate logs and charts from voyages of exploration and incorporated this information into new maps.
       
        Negotiating the ocean barrier
       
       If the ocean was not to be a trackless waste, sailors needed instruments for reading its signposts. Many of these--the compass, astrolabe, cross-staff, and quadrant--had already been developed, and the Portuguese refined their use. The Chinese had first applied the properties of a magnetized needle to navigation--thus inventing the compass--around a.d. 1000. Europeans followed suit over two centuries later. The compass enabled mariners to follow a set direction when out of sight of land and the sun. Even in the Mediterranean a ship could easily become lost in a persistent overcast, and, as a result, merchant fleets had not ventured out in the winter. The compass changed all that.
       
       Knowledge of latitude was not that important for Mediterranean navigation, but for the Portuguese sailing south along thousands of miles of the African coast, it was critical. It was even more critical for the return journey when the ships might swing west, far out of sight of land, to pick up favorable winds. The astrolabe, a complicated instrument, and the simpler cross-staff and quadrant were used to measure the height of the North Star above the horizon. This measurement, converted into an angle, gave the observer's latitude north of the equator.
       
       As the Portuguese approached the equator, the North Star dropped nearer to the horizon until it disappeared. South of the equator a new technique was needed. The Portuguese approach to a solution was symptomatic of their conduct of exploration as a joint national venture. King John II, the great-nephew of Prince Henry, established a commission of experts in the 1480s, headed again by two Jewish scholars, émigrés from Spain. They developed and tested the method of judging latitude by measuring the height of the sun above the horizon at noon.
       
       Both Sagres and Lagos had shipyards. Under Prince Henry's direction, shipwrights developed ship design and building techniques. The result of their labors was the caravel, which was small, maneuverable, of shallow draft--important for sailing in unknown coastal waters--and seaworthy. It was the product of observation and experience, combining elements from Portuguese fishermen's craft and Arab dhows. In particular, it took from the dhows the triangular lateen sails that enabled it to sail much closer into the wind than the square-rigged merchant ships of the time.
       
       This was of the utmost importance in enabling the ships to get back to their port of origin against prevailing winds. Of Columbus' three ships, the Ni–a and the Pinta were true caravels. The Santa Mar’a was a hybrid design, and no one spoke highly of its sailing qualities. Columbus sailed back to Spain in the Ni–a on his first voyage, after the Santa Maria was lost in the Caribbean, and praised her handling. In the caravel, mariners found the ideal instrument for exploration.
       
       What drove Prince Henry and his crews has been described as "Christians and spices"--although gold should figure prominently in the mix. These motives are recorded in the account of Prince Henry's endeavors by a contemporary Portuguese chronicler, Zurara, and they are certainly true. At the conquest of Ceuta, Prince Henry had seen the great wealth in gold, spices, and ivory of the Arab market there. His research told him of the Arab trade routes into the interior. His access blocked by Arab control of the North African coast, he sought an alternative route to the wealth of Africa. He also hoped to discover the legendary Prester John, the mythical leader of an imagined lost Christian kingdom. At the time, Prester John's realm was popularly believed to be somewhere in Africa. If Prince Henry located him, they could form an alliance to press the Muslims in North Africa from two directions. The spirit of the crusader still burned inside the prince.
       
        To know the unknown
       
        But Henry seems to have also been driven by another, more modern motive, one so modern, in fact, that the chronicler Zurara could not give a name to it. We would call it the spirit of inquiry, the desire to know what had been unknown. For twenty years from 1424 he sent out expeditions that brought little financial return and was criticized for wasting public wealth as a result. Yet he persisted with an unswerving patience, urging his expedition leaders forward past obstacles they encountered.
       
       Finally, in 1444, one of his men, Eanes, returned with a cargo of two hundred Africans who were sold as slaves in Lagos. Thus, the first commercial fruit of Portuguese exploration was the trade in human beings. Slavery became one of the pillars of the developing Atlantic economy; its legacy still troubles us today. To the people of that time, however, in most cultures, slavery was unremarkable--although within a century a fierce debate was going on in Spain over the rights of the native peoples in the New World. Zurara records that Prince Henry's critics now considered him a new Alexander "and their covetousness now began to wax greater."
       
       Prince Henry died in 1460, but the trade already established ensured that the impetus for exploration continued. His nephew, King Alfonso V, pioneered new incentives to encourage the further exploration of the African coast, bringing profit to the crown without any financial outlay. Fernao Gomes, a rich Lisbon merchant, contracted to open at least one hundred leagues (three hundred miles) of the coast each year in return for a monopoly of any resulting trade, with the crown getting a percentage. Under this arrangement, Gomes traveled as far in five years along the coast as Prince Henry's men had in thirty. He opened up a thriving trade in pepper and commodities for which the regions were named--the Slave Coast, Gold Coast, and Ivory Coast. The last two names are still in use today. The wealth that flowed into the royal coffers from this trade enabled Alfonso's son, King John II, to finance further expeditions even without immediate returns. In 1482, Diogo Cao reached the mouth of the Congo River.
       
       Just five years later, John II planned and equipped an expedition under Bartolomeu Dias to look for a passage around Africa into the Indian Ocean. According to Ptolemy, the second-century a.d. Hellenized Egyptian geographer who introduced the concept of meridians of latitude and longitude, there was no passage around Africa. He speculatively extended the Dark Continent in a continuous band around the globe, making the Indian Ocean an enclosed sea. But the empirical spirit now gripped the Portuguese. They would no longer simply accept a classical authority. They knew there was a thriving trade in the Indian Ocean and wanted to reach it. They were ready to put Ptolemy to the test. Below the equator, Dias' ships were driven south for thirteen days by a fierce storm. They ended up in the cold southern ocean and thought they would perish. Dias then sailed east and over four hundred miles north before making landfall east of the Cape of Good Hope. He followed the coast east and then northeast until he was certain that he had found the passage. He wanted to continue and cross the Indian Ocean, but his crews insisted on returning.
       
       They arrived in Lisbon just as Columbus was petitioning the king for a second time to support his project of a westward voyage to the Indies. It was fateful coincidence. The news that Dias brought ensured Columbus' rejection. With a sea passage east around Africa now assured, the Portuguese had no need for speculative westward adventures. So Columbus returned to Queen Isabella, and the pioneering of the westward passage fell largely to Spain.
       
        Columbus pursues an 'earthly paradise'
       
        Columbus had already learned much of the craft of Atlantic navigation from the Portuguese. In 1476, when he was 25, he sailed west out of the Mediterranean with a Genoese merchant convoy bound for northern Europe and England. Off the south coast of Portugal they were attacked by the French pirate de Casanove, and Columbus' ship was sunk. He clung to a floating oar and was washed ashore near Lagos. He settled in Lisbon, where there was a Genoese trading quarter, and took up the trade of chartmaker.
       
       He also undertook several voyages, sailing to England and Iceland, to the Portuguese island colony of Madeira, and to Africa's Gold Coast. These trips taught him the pattern of the winds in the North Atlantic, and he put his knowledge to good use on his first transatlantic journey.
       
       Columbus sailed south to the Canary Islands then headed west before the prevailing winds at that latitude and returned on a more northerly route, taking advantage of the circular pattern of the trade winds. The route he pioneered was followed by sailors until the era of steam began.
       
       Columbus' route west was an important navigational discovery, but knowing where he arrived at the end of that route was more problematic. Before he was able to embark, Columbus lobbied the monarchs of Spain and Portugal for his project twice each. On the first occasion in each case they asked a commission to study his proposal, and in each case these scholars recommended against supporting it. In Life and Voyages of Christopher Columbus (1828), Washington Irving portrayed him as a pioneer of knowledge upholding his view of a round earth against the flat-earth obscurantism of medieval Spanish clerics--a totally apocryphal scenario.
       
       The men who considered Columbus' idea all knew that the earth was round. What was at issue was how far did the ocean stretch westward from Europe before washing Asia's eastern shore. This in turn depended on questions about the earth's circumference, the proportion of land to ocean in the globe, and how far eastward Asia extended. On all these questions there were legitimate differences of opinion. Ptolemy overestimated the extent of Asia, but Marco Polo increased that estimate and then placed the island of Cipangu (Japan) a full fifteen hundred miles east of the Asian mainland.
       
       Columbus thought he should make landfall no more than three thousand miles to the west. The commissioners thought Asia might lie three times or more that distance away. They were both right. What nobody had even imagined was that a continent totally unknown to Europe and the east might lie right where Columbus expected to find Asia. Columbus could never accept this fact.
       
       He was certain he had found the Indies. He discovered plants, one cinnamon scented, another gum producing, and believed these could only be the flora of the Spice Islands. He heard a native use the word Cubacan and thought the reference was to China's Great Khan. On his second voyage in 1493--94 he sailed along Cuba's southern coast, believing this was the Chinese mainland. On his fourth voyage of 1502--1504 he explored the coast of Central America, but in his mind he was sailing down the Malay Peninsula, looking for its southernmost point to turn east and reach India.
       
       There was something of the character of Cervantes' marvelous creation, Don Quixote, in this aspect of Columbus. On his third voyage in 1498 he explored Trinidad, which lies off what is now Venezuela, opposite the Orinoco delta. The river pushed a huge volume of fresh water well out to sea. Columbus noted this and realized it could only come from a mighty river flowing out of a great landmass where his geography told him none should be. He retreated into Christian mythology and wrote "there are great indications of this being the terrestrial paradise."
       
        The New World identified
       
        It was left to others to frame the realization that Columbus had arrived neither in Asia nor the earthly paradise. When Amerigo Vespucci sailed with a Spanish expedition that explored the coasts of Venezuela and the Guyanas, he, too, believed he was off the shores of Asia. Yet he was a child of the Florentine Renaissance with a probing mind. He wrote in a letter to a Florentine friend: "Rationally, let it be said in a whisper, experience is certainly worth more than theory."
       
       His subsequent voyages, under the auspices of Portugal, more than two thousand miles down the coast of Brazil, to Patagonia, changed his assessment of where he was. His account of his journey and his observations of the natives and their customs were published in 1507 under the title Mundus Novus (New World). Of it he wrote: "We arrived at a new land which, for many reasons ... we observed to be a continent." Martin Waldseemüller was an obscure canon in a monastery in Alsace with an interest in geography. He was about to publish a new edition of Ptolemy's Geography when he read Mundus Novus. He and his colleagues were so excited that they scrapped the plans for Ptolemy and published instead Cosmographiae Introductio, which added a fourth, new world as described by Vespucci to the three continents of the Ptolemaic universe. The new continent appeared on a map, labeled with the latinized version of Vespucci's first name, America. The printing press did the rest.
       
       Now that the lands Columbus had stumbled upon had become known for what they were and named, it remained to complete the circle of exploration around the globe to east and west. Portugal had already sent Vasco da Gama through the door Dias had opened.
       
       Da Gama set sail in 1498, rounding the Cape of Good Hope and making his way up the east coast of Africa in search of a pilot to take him across to India. Not surprisingly, he met with suspicion and hostility from the Arab traders and sailors there. Finally, in the port of Malindi, he found a man, Ibn Majid, willing to guide him. He could not have done better. It is one of history's ironies that Majid was the master of navigation in the region, the author of many authoritative books, who became the patron saint of Muslim mariners. Later Arab historians speculated that he must have been drunk when he agreed to show a Christian navigator the way to India.
       
       Da Gama reached Calicut in southwest India and was received somewhat contemptuously there by the ruler, who would soon have cause to regret that. It was clear that the Portuguese could not enter the Arab-dominated trade of the region peacefully. Da Gama returned in 1502 with a well-armed fleet of fifteen ships. He used exemplary terror to secure the submission of the king of Calicut, seizing traders and fishermen at random, then killing and dismembering them. Da Gama sent the pieces to the king, suggesting he make himself a curry. The extremes of the Muslim-Christian conflict around the Mediterranean were spilling over into a new theater.
       
       Over the next decades, the Portuguese systematically wrested control of the Indian Ocean from the Arabs. They destroyed a Muslim fleet and seized Muslim strongholds. From this base they traded east, to Canton, Nagasaki, and the Spice Islands. Finally, they would encounter the Spanish, coming from the opposite direction, in the Philippines. These expeditions opened up a hugely profitable trade for Portugal, bypassing the monopoly on Asian trade with Europe held for centuries by the merchants of Venice, Egypt, and the Levant.
       
        The first circumnavigation
       
        The Spanish pressed west, looking for a route across or around the new continent. They found both. In 1513, Vasco Nœ–ez de Balboa led an expedition through the jungles and snake-infested swamps of the Panama isthmus and became the first European to set eyes on the Pacific Ocean from the western shores of the Americas. Ferdinand Magellan, a Portuguese captain in the service of Spain, in 1519 led the expedition that opened the sea route west and became the first to circumnavigate the globe.
       
       Magellan's voyage is an epic story worthy of a Homer. His five ships, none larger than 120 tons, crossed the Atlantic to Brazil and coasted south to Patagonia, where they wintered. Just two decades earlier, such a journey would have been a major new advance in discovery. The next spring he found the narrow passage that became known as the Straits of Magellan. With no idea where it would lead him, he took a month to negotiate its sinuous 334 miles, beset by unpredictable winds and treacherous currents. Emerging into the ocean he later named the Pacific because of the calm weather he experienced on his crossing, Magellan believed Asia was 3,000--4,000 miles away. It was three times that distance. Antonio Pigafetta, who kept a record of the expedition, wrote: "We issued forth from the said strait and into the Pacific sea where we remained three months and twenty days without taking on board provisions. ... and we ate only old biscuit turned to powder. All full of worms and the urine which the rats had made on it ...." They gnawed ox hides soaked in seawater and caught rats they sold to one another for gold coin.
       
       They made landfall on Guam and proceeded to the Philippines, where Magellan was wounded after becoming involved in an intertribal conflict. He died on a beach, covering his men's retreat to their boats. The rest of the expedition limped home through the other half of the world, eluding capture by the Portuguese whose domain it had become. Led by del Cano, they finally returned to Spain in September 1522, in the Vittoria. Just 18 men, from an original 250, survived. They were the first circumnavigators of the globe. The hardihood of the discoverers of that time is difficult for modern people to comprehend. Americans have explored space and sent men to the moon and back with the loss of a dozen lives. Every major voyage into the unknown in this first age of maritime discovery meant certain death for a good proportion of those on it and serious privations for the rest. After the Pacific crossing, Pigafetta noted: "I believe that nevermore will any man undertake to make such a voyage." In fact, there were plenty ready to follow.
       
       The circumnavigation by the Magellan expedition makes a fitting conclusion to the opening of the age of European global exploration. That work continued through the next centuries, exploring interiors, discovering Australia and Antarctica, refining geography, until today we are reaching out beyond the bounds of earth. But the outlines were definitively established by these first voyagers, who left behind Ptolemy and medieval Christian cosmography and gave us the world we know with new continents and a continuous ocean, transformed from barrier to passageway.
       
       The enterprise of exploration was also the first great manifestation of the empirical spirit in action. Ancient authorities were tested against the experience of voyagers. Theory was wedded to practice as mathematics and astronomy were applied to the problems of navigation and then tested on the oceans. The experiences of mariners were gathered and turned into a systematic body of knowledge, producing accurate charts and information on winds and currents. Leif Erikkson reached Vinland, but knowledge of his journey was not disseminated. Each of the voyages of discovery produced information that others could use and build upon.
       
        Conceiving the world as one
       
        The world was not only conceived as one as a result of the explorations, it became one in practice. Globalization of trade and manufacture are often featured in the news today, but the origin of this process lay back in the sixteenth century. Asian silks and spices flowed westward around Africa to Europe's Atlantic coast and eastward across the Pacific to Spanish America. There they were transported across Panama and shipped to Seville. Silver flowed from Spain's Peruvian mines, west to Asia and east to Spain, from whence various manufactures came back to the settlers.
       
       The interconnections were intensified later through the trading empires of the English and Dutch and the development of European manufactures. New flows of goods and people developed, not all of them benign. From the Americas, Europe got potatoes, maize, and tobacco. Horses and cattle moved in the opposite direction, as did devastating disease and human beings in th e form both of European settlers and African slaves.
       
       Cultures came into new contact, often violent and traumatic. The clash of cultures was intensified by the process of colonization and empire, the consequences of which are still being worked out today. This face of European expansion might be summed up by the motto of a book on the West Indies by the Spaniard Vargas Machuca: "By the sword and by the compass, More and more and more and more."
       
       The concept of human rights applied to dealing with the people of other cultures also arose from the discovery experience. In 1510, the Spanish Dominican Fra Anton Montecino delivered a blistering sermon in Santo Domingo in Hispaniola (now the Dominican Republic). "For they are God's people, these innocents whom you destroyed. By what right do you make them die? ... They lived in peace in this land before you came, in peace in their own homes. They did nothing to harm you to cause you to slaughter them wholesale. ... Are you not under God's comma to love them as you love yourselves?"
       
       Others took up this theme, most notably another Dominican, Bartolomé de las Casas, who became bishop of Chiapas, Mexico. His views of the rights of the natives and moral responsibility of the colonizers sparked heated debate in Spain and modified colonial policy. They also rehearsed the later arguments against slavery and shaped the development of theories of human rights that should be enjoyed regardless of religious faith or perceived levels of civilization.
       
       In all these areas, the age of exploration set in motion processes practical and intellectual, economic and moral, that shaped subsequent centuries. They showed the world to be one. We are still working out the consequences of that oneness, particularly in the realm of sharing the planet as different cultures. Through the exploration of space, we are able for the first time to see a visual image of the one earth. That picture was first imagined, however, by the age of exploration.
       
       

by Michael Marshall
Michael Marshall is executive editor of THE WORLD & I.