Exploring the Globe

This page attempts some coverage – by no means exhaustive! – of the topic of exploration and its place in the history of science. Although I will deal primarily with European exploration, it is important to note at the outset that a desire to explore the world beyond one’s immediate borders and boundaries of language and culture was not unique to Europeans. Exploration is connected to a variety of scientific subjects: geography and cartography (because creating accurate maps was both a reason for exploring and a crucial tool for explorers), astronomy (because the stars were essential to navigators), anthropology (because observations of different peoples and their customs was important to all explorers), and biology (because explorers routinely described the flora and fauna of places they visited, often with accounts of how local people used them). The subject of exploration is also deeply intertwined with two other topics that I take up in separate pages: encounters with indigenous knowledge systems (or indigenous science) and constructions of racial and ethnic differences. There is no getting around the fact that European voyages of exploration were ultimately incredibly destructive for peoples around the world, in Africa, the Caribbean and North and South America, and that we still live with the devastating consequences of these voyages today.


Let’s begin with ancient Greek attempts to measure and map the earth. Although, as you know, there were no serious debates after Aristotle’s day about the sphericity of the earth, there were considerable debates about the size of the earth. There were numerous methods devised for calculating the circumference of the earth. The most accurate of these methods by modern standards, was that of Eratosthenes (ca. 275 – 194 B.C.), a mathematician, geographer, and astronomer. He is believed to have been chief librarian at the famed Library of Alexandria in Egypt.


Eratosthenes method was simple and elegant. He noted that at noon on the summer solstice the sun cast no shadow in the city of Syene (modern day Aswan in Egypt). Syene, he reasoned, must be directly under the Tropic of Cancer. Alexandria, Egypt, where Eratosthenes lived, was directly north of Syene. The distance between the two cities was 5,000 stades (an ancient Greek measurement roughly equal to 185 meters or one-eighth of a mile). Eratosthenes measured the angle between the direction of the sun and the vertical in Alexandria at midday on the summer solstice. This angle was a little over seven degrees, or one-fiftieth of a circle. This angle was also equivalent to the angular distance between Syene and Alexandria. So Eratosthenes simply multiplied 5,000 stades by 50, and calculated that the circumference of the earth was 250,000 stades. This turns out to be pretty close to the modern figure. However, Eratosthenes was not the only person to try to figure out the circumference of the earth. The following picture shows some other estimates and how they compare in accuracy to Eratosthenes’ estimate. While it’s clear to us today that Eratosthenes came the closest; that was by no means obvious to ancient, medieval or early modern people.

Estimates of earths size

Sources: Both of the images above come from Determining the earth’s size.

The other important Greek is one you should be very familiar with: Claudius Ptolemy (ca. A.D. 90 – 168), author of the Almagest (astronomy) and the Tetrabiblos (astrology). Ptolemy also wrote a book on geography and cartography, called Geography.ZoroasterPtolemyPtolemy’s Geography not translated into Latin until fifteenth century, so its impact in Europe came later than that of the Almagest. In the Geography, Ptolemy gave a description of the all the parts of the known world, which for him was comprised of Ireland, Britain, Iberian peninsula, Gaul [roughly France], Germany, Italy, Greece, North Africa, Egypt, Libya, Ethiopia, Asia Minor, Armenia, Cyprus, Syria, Palestine, Mesopotamia, Babylonia, Persia [roughly Iran], Scythia and India. Not only did Ptolemy describe the known world, he invented and explained techniques of map projections, that is, techniques for representing the curved surface of the earth on a flat piece of paper. He used a system of lines of longitude and latitude, so each place on earth could be described by a unique set of coordinates. In the fifteenth and sixteenth centuries, Europeans would employ Ptolemy’s mapping techniques to map parts of the world that had been unknown to Ptolemy.

Ptolemaic map of known world.


Page from a French translation of The Travels of Marco Polo. Livre des merveilles fol. 58r. The Khan at war, Faksimile UB Graz Sig.: HB 15 210/P 778. Wikimedia Commons.

Marco Polo (1254-1324) is undoubtedly the most famous medieval European traveler. His account of his travels through the Middle East and China remains fascinating reading to this day.

Marco Polo was from a Venetian merchant family. In 1271, when he was seventeen, Marco Polo joined his father and uncle on a journey to China. Marco Polo and his family traveled along the famous “Silk Road,” a land route from the Mediterranean through central Asia and into China. During the Middle Ages there was an active trade in luxury goods from the far East: silk from China, gemstones and carpets from Persia, spices from Ceylon and Java. Mediterranean merchants, primarily from the Italian cities of Venice, Genoa, and Pisa, sold luxury goods that had been transported across the Silk Road to the ports of the eastern Mediterranean. However, these merchants did not themselves travel to China. The Polos were able to do this because of a unique set of political circumstances. Up until about 1250, Muslim rulers controlled the Silk Road (or the parts of it up to the border with China). Muslim merchants traded with European merchants at Alexandria, Aleppo or Damascus, but they did not allow Europeans to travel to China themselves. That changed from about 1250 to about 1350, due to the Mongol conquests of the 13th century. Genghis Khan and his army came down from Mongolia to Peking in 1214.  In the next fifty years, they conquered nearly all of eastern Asia, then turned westward across Russia, and into Poland and Hungary. The Mongol empire at its height was twice the size of the Roman empire at its greatest extent. And Mongol rulers allowed European merchants to travel the Silk Road. This empire collapsed in about 1350, and the Silk Road was again closed to Europeans. During this century a few bold and enterprising European merchants took caravans across the Silk Road to the cities of India and China. The Polos were among this intrepid few. The journey itself took three and a half years, and the Polos stayed at court of Kublai Khan in China for seventeen years. During this time, Marco Polo traveled all over China. The Polos returned home to Venice in the winter of 1295, after an absence of twenty-four years. Marco Polo dictated an account of his travels to Rustichello da Pisa, a writer of romances.   The book soon spread throughout Europe in manuscript form, and became known as The Travels of Marco Polo.  Marco Polo’s travel narrative was very popular in his own day and for a long time thereafter. It was translated into numerous European languages, and was later printed. It is still in print today! This was the only first-hand account of the Silk Road and of China by a European traveler until the sixteenth century.

Travels of Marco Polo. Wikimedia Commons.

To give you a flavor of the book, with its observations on people, places, customs and natural resources, here is Marco Polo’s chapter on Persia [modern day Iran]:

Now you must know that Persia is a very great country, and contains eight kingdoms. I will tell you the names of them all.

The first kingdom is that at the beginning of Persia, and it is called CASVIN; the second is further to the south, and is called CURDISTAN; the third is LOR; the fourth SUOLSTAN; the fifth ISTANIT; the sixth SERAZY; the seventh SONCARA; the eighth TUNOCAIN, which is at the further extremity of Persia. All these kingdoms lie in a southerly direction except one, to wit, Tunocain; that lies towards the east, and borders on the (country of the) Arbre Sol.

In this country of Persia there is a great supply of fine horses; and people take them to India for sale, for they are horses of great price, a single one being worth as much of their money as is equal to 200 livres Tournois; some will be more, some less, according to the quality.  Here also are the finest asses in the world, one of them being worth full 30 marks of silver, for they are very large and fast, and acquire a capital amble. Dealers carry their horses to Kisi and Curmosa, two cities on the shores of the Sea of India, and there they meet with merchants who take the horses on to India for sale.

In this country there are many cruel and murderous people, so that no day passes but there is some homicide among them. Were it not for the Government, which is that of the Tartars of the Levant, they would do great mischief to merchants; and indeed, maugre the Government, they often succeed in doing such mischief. Unless merchants be well armed they run the risk of being murdered, or at least robbed of everything; and it sometimes happens that a whole party perishes in this way when not on their guard. The people are all Saracens, i.e. followers of the Law of Mahommet.

In the cities there are traders and artisans who live by their labor and crafts, weaving cloths of gold, and silk stuffs of sundry kinds. They have plenty of cotton produced in the country; and abundance of wheat, barley, millet, panick, and wine, with fruits of all kinds.


The Travels of Marco Polo – Volume 1.

The Travels of Marco Polo – Volume 2.

Ibn Battuta (or Battutah or Batuta, 1304 – ca. 1369) was a medieval Muslim explorer who visited every country and region in the Islamic world, and several other places as well. He set off as a young man on a pilgrimage to Mecca. In his account of his travels, he states:

I left Tangier, my birthplace, on Thursday, 2nd Rajab 725 [June 14, 1325], being at that time twenty-two years of age [22 lunar years; 21 and 4 months by solar reckoning], with the intention of making the Pilgrimage to the Holy House [at Mecca] and the Tomb of the Prophet [at Medina].

While a pilgrimage to Mecca was (and is) a typical religious activity for an observant Muslim, Ibn Battuta fell in love with traveling and never stopped. As you can see from the map of his various journeys, he spent time in Asia, the Arabian peninsula, and northern and western Africa.


In 1354, he dictated an account of his travels to Ibn Juzayy, a Spanish scholar and court official. Ibn Battuta’s travel narrative was the most comprehensive account of the Muslim world available in the Middle Ages. He includes his observations of the people and customs as well as the natural resources of different areas. To take just a few examples:

During his travels in Africa, Ibn Battuta stops in the town of Kilwa, on the eastern coast.  (Look on the map above — this is the southernmost city on Ibn Battuta’s journeys.)  He describes the city and its inhabitants as follows:

Map of Kilwa from Georg Braun and Franz Hogenberg, Civitates orbis terrarum (1572). Wikimedia Commons.

The majority of its inhabitants are Zanj, jet-black in colour, and with tattoo marks on their faces. I was told by a merchant that the town of Sufala lies a fortnight’s journey [south] from Kilwa and that gold dust is brought to Sufala from Yufi in the country of the Limis, which is a month’s journey distant from it. Kilwa is a very fine and substantially built town, and all its buildings are of wood. Its inhabitants are constantly engaged in military expeditions, for their country is contiguous to the heathen Zanj.

During his travels in India, Ibn Battuta observes strange and exotic plants and explains how the local people use them:

Betel plants in Bangladesh. Wikimedia Commons.

They grow also betel-trees and coco-palms, which are found only in India and the town of Dhafari. Since we have mentioned these trees, we shall describe them and their properties here.  Betel-trees are grown like vines on cane trellises or else trained up coco-palms. They have no fruit and are grown only for their leaves. The Indians have a high opinion of betel, and if a man visits a friend and the latter gives him five leaves of it, you would think he had given him the world, especially if he is a prince or notable. A gift of betel is a far greater honour than a gift of gold and silver. It is used in this way. First one takes areca-nuts, which are like nutmegs, crushes them into small bits and chews them. Then the betel leaves are taken, a little chalk is put on them, and they are chewed with the areca-nuts. They sweeten the breath and aid digestion, prevent the disagreeable effects of drinking water on an empty stomach, and stimulates the faculties.

Coconut tree. Wikimedia Commons.

The coco-palm [coconut] is one of the strangest of trees, and looks exactly like a date-palm. The nut resembles a man’s head, for it has marks like eyes and a mouth, and the contents, when it is green, are like the brain. It has fibre like hair, out of which they make ropes, which they use instead of nails to bind their ships together and also as cables. Amongst its properties are that it strengthens the body, fattens, and adds redness to the face. If it is cut open when it is green it gives a liquid deliciously sweet and fresh. After drinking this one takes a piece of the rind as a spoon and scoops out the pulp inside the nut. This tastes like an egg that has been broiled but not quite cooked, and is nourishing. I lived on it for a year and a half when I was in the Maldive islands.

Ibn Battuta’s account of his travels was written in Arabic and was not translated into European languages until the 19th century.


All quotes from Ibn Battuta’s writings from Fordham University Internet Sourcebook.

Franz Rosenthal, “Ibn Battuta” Complete Dictionary of Scientific Biography. Vol. 1.  Detroit: Charles Scribner’s Sons, 2008. 516-517.

For more information, see The Travels of Ibn Battuta.


In the fifteenth and sixteenth centuries, European exploration of the globe took on a new character. Medieval travelers like Marco Polo and Ibn Battuta were solitary figures, motivated by a desire for personal gain or just a love of travel and a hankering for novel experiences. In the fifteenth and sixteenth centuries, the Portuguese and the Spanish embarked on large scale, state-funded programs of exploration. They were subsequently joined in these endeavors by other European countries. The Portuguese were the first to make exploration a high priority. The key figure in this development was Prince Henry (1394 – 1460), who was later nicknamed Prince Henry the Navigator. Henry was the third of six sons of King John I. He initiated, organized, funded and commanded expeditions to Africa. He was motivated by a desire to convert Muslims and other non-Christians (recall that northern Africa was part of the Islamic world), as well as a desire to find treasure, especially gold. And the Portuguese did indeed establish a rich trade in pepper, ivory, gold and eventually slaves.Henry_the_Navigator1

Henry sent out a series of ships to explore the western coast of Africa. He funded a number of technological and scientific innovations as part of his mission to explore and exploit the wealth of Africa. For example, ship builders working for Henry developed a new type of ship, the square-rigged sailing caravel, which was suited to extended voyages into unknown lands and waters. The caravel replaced the galley for long voyages. The galley was a long, thin ship powered by rowers. It took between 150 and 200 men to row. This was great for sailing around the Mediterranean, where one was never too far from land. The galley had the advantage of being fast and highly maneuverable. However, it was unsuited to long sea voyages because it couldn’t carry much cargo – so there was no way to keep that large crew fed! The caravel required a much smaller crew, because the sails could take advantage of winds from different directions, and it could hold a much larger amount of cargo.

Portuguese square-rigged caravels. Wikimedia Commons.

Henry also funded innovations in cartography and navigation, including new methods to determine latitude a sea. He put together a team in Lisbon that pieced together facts brought back by sailors to make new maps and charts. Ptolemy’s maps from Geography showed the part of Africa below the equator as “Terra Incognita,” which means “unknown land.” Year after year Henry dispatched expeditions, each reaching a bit farther into this unknown (from a European perspective) territory. Part of his motivation (in addition to conversion and exploitation of African resources) was to see if it might be possible to sail around the southern end of Africa and into the Indian Ocean, and from there find a sea route to China. Prince Henry was certainly familiar with Marco Polo’s account of the splendors of China, and he knew of the rich trade in luxury products along the Silk Road. By Henry’s day, the Silk Road was once again closed to Europeans because it was back under Muslim control. And trade with Muslim merchants was completely dominated by Italians. Portugal had no outlet to the Mediterranean sea, but there was just a short strait between Portugal and Africa. If the Portuguese could find a sea route to Africa, they would be able to bypass Italian and Islamic middlemen and trade directly with the Chinese.

One of the tragic consequences of the Portuguese desire to exploit the riches of Africa was the beginnings of the slave trade. In 1444 the first Portuguese ships carrying human cargo – 200 Africans to be sold as slaves – arrived back in Lisbon. This trade ended up being enormously lucrative and long-lived. Prince Henry’s death in 1460 caused only a brief hiatus in exploring enterprise. It was continued by the next two kings, Alfonso and John II.

Voyage of Bartholomeu Dias, 1487. Wikimedia Commons.

In 1487, the Portuguese nobleman Bartholomeu Dias (1450 – 1500) became the first European to reach the southern tip of Africa. Like many Portuguese explorers before him, he set out on a voyage down the coast of Africa. When he was quite far south, he encountered severe storms and was driven off course. After the storm, he steered east, but went several days without sighting land. He turned north and eventually spotted mountains. He followed the coast, which ran northeast, and realized that he had rounded the southern tip of Africa. He wanted to press forward into Indian Ocean and on to India, but his crew refused. Their provisions were low, so they returned to Portugal. Dias was lost at sea somewhere near the Cape of Good Hope in 1500.

The most famous (or infamous) of the early modern European explorers is the Italian Christopher Columbus (1451 – 1506), who “in 1492, sailed the ocean blue.” Columbus is the only one of the explorers to have his own national holiday in many parts of the world, although whether he deserves this or not is hotly contested. Columbus is probably also the least well-understood explorer. To this day, many schoolchildren are taught that he “discovered” that the world was round. In fact Columbus did no such thing, and his voyages of exploration need to be situated in historical context.


What was Columbus trying to do? Quite simply, Columbus was trying, like the Portuguese explorers, to find a sea route to China. We know Columbus read and was impressed by Marco Polo’s book, because we the copy he owned and extensively annotated has survived. The Portuguese were trying to find a sea route to China by sailing around the southern tip of Africa into the Indian Ocean. Columbus proposed to get to China by sailing west across the Atlantic Ocean, presuming he would reach the east coast of China this way.

Columbus’ notes on Marco Polo’s Travels. Wikimedia Commons.

What made Columbus believe he could do this? First, you have to understand that Columbus didn’t know there was anything (let alone two whole continents!) in the Atlantic Ocean between the west coast of Europe and the east coast of China. Now recall that there were multiple different estimates of the circumference of the earth. Some of them (most notably Ptolemy’s) were considerably smaller than the true value. Further, there were wildly varying estimates of how much of the earth was covered by water, ranging from one quarter up as high as seven eighths. Columbus picked the very smallest estimate he could find of the circumference of the earth and the very smallest estimate of the percentage of the earth covered by water. These estimates convinced him that sailing west across the Atlantic was a reasonable way to get to China. By “reasonable,” I mean that he thought he could make the journey in a short enough time that he wouldn’t run out of provisions and starve before he got to China.

Christopher_ColumbusWhy did most people believe this voyage was impossible?   It certainly wasn’t because they thought the earth was flat. Most of Columbus’ European contemporaries believed (correctly) that the earth was larger than he thought, and that the oceans covered a much larger percentage of the earth. Thus they believed the voyage would be too long. There would be no way to stock a ship with enough provisions to prevent the crew from starving long before land was sighted.

Columbus tried to convince the Portuguese King John II to fund his voyage. Unfortunately for Columbus, Dias had just demonstrated that it was possible to go around the southern tip of Africa, and the Portuguese wanted to devote their resources to this route to India and China. Columbus eventually convinced the Spanish monarchs, King Ferdinand and Queen Isabella, to fund his voyage. The Spanish were behind the Portuguese in exploration and eager to find a way to catch up. They were willing to take a chance on Columbus.

Of course, this gamble paid off, and the Spanish rapidly embarked on an extensive program of exploration that eventually came to overshadow the Portuguese. Like the Portuguese, they established a central, state-funded institution, the House of Trades (Casa de Contraction) to coordinate and promote scientific and technological innovations that would further their mission to convert, colonize and exploit new regions of the globe.

Let me end with a lesser known, but quite fascinating explorer, whose life was very directly affected by both the Portuguese and the Spanish voyages of exploration.  Stephen the Moor (1503 – 1539), also known as Estévanico and Estévan, was born in the Morroccan city of Azemmour. This city was conquered by the Portuguese in 1513, and Stephen (almost certainly a name given to him by his European captors) was sold into slavery. He ended up in Spain as the slave of Andrés Dorantes de Carranza (ca. 1500 – 1550), one of the first Spanish explorers. In 1527, Stephen accompanied Dorantes on an expedition to conquer Florida led by Pánfilo de Narváez (1470–1528). The expedition was composed of five ships and 600 men. When they reached Tampa Bay, Florida, they were attacked by the natives, and forced to flee through the jungle. They built boats and sailed for the Mexican coast, but ended up in Texas, near Galveston, on November 6, 1528. Of the original 600 men, only 80 were still alive, including Stephen and his master Dorantes. The survivors were captured and enslaved by natives in Texas and only four survived, including Stephen, Dorantes, Cabeza de Vaca and Alonso Castillo. These four men escaped in 1534, traveled inland where they encountered another tribe of natives. These natives were considerably friendlier. The four men were taught the skills of healing and became medicine men. They became fluent in several native dialects. Members of the tribe guided the men to Sinaloa in Mexico. From there, the group traveled to Mexico City, arriving in July 1536. Stephen the Moor stayed in Mexico City for a few years. In 1539, the Viceroy of Mexico asked him to lead an expedition into Arizona and New Mexico. When the expedition reached northwest New Mexico they encountered Hawikuh, a Zuni pueblo. Stephen went out alone to speak with Zuni leaders, but they did not trust him (in part because he was carrying a medicine gourd trimmed with owl feathers, and this bird was a symbol of death for the Zuni). They killed Stephen, although they left other members of his party unharmed.  In an article for the Dallas African American History Examiner, Vicki Davey comments: “This guy just could not get a break!” Stephen the Moor is the first person born in Africa to travel to the continental United States.



Stephen himself did not write about his adventures, but one of the other men who survived with him did.  See Álvar Núñez Cabeza de Vaca, “Relation that Álvar Núñez Cabeza de Vaca gave of what befell the armament in the Indies whither Panfilo de Narvaez went for Governor from the year 1527 to the year 1536 [1537] when with three comrades he returned and came to Sevilla.” In Spanish Explorers in the Southern United States, 1528-1543, edited by Frederick Webb Hodge.  Reproduction of the 1555 edition, Austin: Texas State Historical Association, 1982.

Article on “Stephen the Moor” from The Mariners’ Museum website.

ASSIGNMENT: Read Myth of the Flat Earth by Jeffrey Burton Russell.  This is a brief summary of the main arguments of his book, Inventing the Flat Earth: Columbus and Modern Historians (1997).

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