How did the idea develop that in the Middle Ages people thought the Earth was a flat disc? In the seventh century, Isidore of Seville (though hardly a model of scientific accuracy) calculated the equator to be eighty thousand rods long. Therefore, he thought the Earth was round. But among Isidore’s manuscripts is a diagram that influenced many representations of our planet, the so-called T-O map.
The upper part represents Asia—at the top because, according to legend, earthly paradise was to be found in Asia. The horizontal bar represents the Black Sea on one side and the Nile on the other, and the vertical bar is the Mediterranean, so that the quarter circle on the left represents Europe and that on the right, Africa. All around it is the great circle of the ocean.
The impression that the Earth was seen as a circle is given by the maps illustrating the Commentary on the Apocalypse by Beatus of Liébana. This text, written in the eighth century but illustrated by Mozarabic illuminators in later centuries, was to have a major influence on the art of the Romanesque abbeys and Gothic cathedrals—and its model is to be found in countless other illuminated manuscripts.
How was it possible for people who thought the Earth was round to draw maps showing it to be flat? The first explanation is that we do the same ourselves. Criticizing the flatness of these maps would be like criticizing the flatness of our modern-day atlas. It was a naive and conventional form of cartographic projection.
It could be pointed out that over the same centuries the Arabs had produced more accurate maps, though they had the bad habit of representing north at the bottom and south at the top. But we have to bear in mind other considerations. The first is suggested by Saint Augustine, who was well aware of the debate begun by Lactantius about the cosmos in the shape of a tabernacle, but was at the same time aware of the views of the ancients on the roundness of the globe. Augustine’s conclusion is that we should not place too much emphasis on the biblical description of the tabernacle because, as we know, the holy scriptures often speak through metaphor, and perhaps the Earth is round. But since knowledge about whether it is spherical or not doesn’t help us to save our souls, we can ignore the question.
This doesn’t mean, as has often been suggested, that there was no medieval astronomy. We need only cite the story of Gerbert d’Aurillac, the tenth-century pope Sylvester II, who in order to obtain a copy of Lucan’s Pharsalia promised an armillary sphere in exchange; not realizing that the Pharsalia had been left incomplete on Lucan’s death, upon receiving an incomplete manuscript he gave only half of the armillary sphere in exchange. This indicates the great attention given to classical culture during the early Middle Ages, but it also indicates the interest in astronomy at the time. Ptolemy’s Almagest and Aristotle’s De caelo were translated during the twelfth and thirteenth centuries. As we all know, astronomy was one of the subjects of the quadrivium taught in medieval schools, and in the eighth century John of Holywood’s Tractatus de sphaera mundi, based on Ptolemy, was to be the undisputed authority for centuries to come.
Yet it is also true that geographical and astronomical notions had long been confused by the ideas of authors such as Pliny or Solinus, for whom astronomy was certainly not of uppermost concern. The picture of the Ptolemaic cosmos, formed perhaps indirectly through other sources, was theologically most credible. Each element of the world, as Aristotle taught, had to remain in its proper natural place, from which it could be moved only by violence and not by nature. The natural place for the earthly element was the center of the world, whereas water and air had to remain in an intermediate position, and fire was at the edge. It was a reasonable and a reassuring picture, and this idea of the universe enabled Dante to imagine his journey into the three realms of the afterlife. And if this representation did not take account of all celestial phenomena, Ptolemy himself contrived to introduce adjustments and corrections, such as the theory of epicycles and deferents, according to which, in order to explain various astronomical phenomena such as accelerations, positions, retrograde motions, and the variations in distances of various planets, it was supposed that each planet rotates around the Earth along a larger circle, called the deferent, but also moves in a small circle, or epicycle, around a point C of its own deferent.
Lastly, the Middle Ages was a period of great travel, but with the roads in disrepair, great forests to pass through, and stretches of sea to be crossed at the mercy of buccaneers, there was no possibility of drawing adequate maps. They were purely indicative, like the instructions in the Pilgrim’s Guide at Santiago de Compostela, which said, more or less, “If you want to get from Rome to Jerusalem, head southward and ask along the way.” Now, try thinking of the rail maps you find with train timetables. No one could deduce the exact shape of Italy from that series of junctions, each perfectly clear in itself when you have to take a train from Milan to Livorno (and realize that you have to change at Genoa). The exact shape of Italy is of no interest to anyone traveling to that station.
The Romans built a series of roads that linked every city in the known world, but this is how those roads were represented in the map known as the Tabula Peutingeriana, named after the man who had rediscovered it in the fifteenth century. The upper part represents Europe, with Africa below, but we are in exactly the same situation as the railway map. From this map we can see the roads, our points of departure and arrival, but have absolutely no idea about the shape of Europe, or the Mediterranean, or Africa—and the Romans certainly had a much clearer notion of geography than this. They were not interested in the shape of the continents, but rather in whether, for example, there was a road that would take them from Marseille to Genoa.
Then again, medieval journeys were imaginary. The Middle Ages produced encyclopedias, Imagines mundi, whose authors tried as far as possible to satisfy the taste for wonder, writing about far-off, inaccessible lands, and these books are all written by people who had never seen the places they are describing—the force of tradition at that time was more important than experience. A map did not seek to represent the form of the Earth but to list cities and peoples along the way.
Once again, symbolic representation was more important than empirical representation. In many maps, the illuminator was most concerned about placing Jerusalem at the center of the Earth, rather than showing how to get there. Yet most maps of that period represent Italy and the Mediterranean fairly accurately.
One last consideration. Medieval maps did not have a scientific purpose but instead responded to the audience’s need for wonder, in rather the same way that popular magazines today show us that flying saucers exist and we are told on television that the pyramids were built by an extraterrestrial civilization. The creators of these maps looked up at the sky with the naked eye to see comets, which the imagination immediately transformed into something that (today) would confirm the existence of UFOs. On many fifteenth- and sixteenth-century maps with a reasonably accurate cartographic layout, mysterious monsters are depicted in the lands where they are supposed to live, and are reproduced on the map in a not entirely mythical fashion.
So let us not be too critical of medieval maps. It is with them that Marco Polo arrived in China, the Crusaders in Jerusalem, and perhaps the Irish or the Vikings in America.
A short aside—is it really true, as legend suggests, that the Vikings reached America? We all know that the real revolution in medieval navigation came with the invention of the stern-mounted hinged rudder. On Greek and Roman ships, as well as those of the Vikings and even those of William the Conqueror who landed on the English coast in 1066, the rudder consisted of two rear side-oars, operated in such a way as to set the intended direction of the boat. The system, apart from being fairly exhausting to use, made it practically impossible to maneuver large wooden vessels. Above all, it was impossible to sail against the wind; to do so, it was necessary to tack—to move the rudder so that each side of the boat faced alternately into the wind, first one side and then the other. Sailors therefore had to limit themselves to navigating close to s
hore, following the coastlines so that they could take shelter when the wind was unfavorable.
The Vikings (and the same was true for the Irish monks) could never, therefore, have sailed from Spain to Central America, as Columbus would later do. But the picture changes if we imagine they first took a route from Iceland to Greenland, and from there to the Canadian coast. Looking at a map, we can easily see how skilled mariners in longships could succeed (with who knows how many shipwrecks along the way) in reaching the far north of the American continent and perhaps the coast of Labrador.
THE SHAPE OF THE SKY
But let us leave the Earth and look at the sky. Aristarchus of Samos had advanced a heliocentric theory between the fourth and third centuries B.C.E., as Copernicus recorded. Plutarch tells us that Aristarchus was accused of impiety precisely because he had put the Earth in movement so as to explain, through earthly rotation, astronomical phenomena that could not otherwise be accounted for. Plutarch did not agree with this theory and Ptolemy later judged it “ridiculous.” Aristarchus was way ahead of his time, and perhaps he reached his conclusion for the wrong reasons. There again, the history of astronomy is curious. A great materialist such as Epicurus developed an idea that survived for so long that it was still being discussed by Gassendi in the seventeenth century, as well as appearing in Lucretius’s De rerum natura. He suggested that the sun, the moon, and the stars (for many very serious reasons) can be neither larger nor smaller than how they appear to our senses. So Epicurus judged the sun to have a diameter of about thirty centimeters.
Copernicus’s De revolutionibus orbium coelestium was published in 1543. We imagine the world was suddenly turned upside-down and we talk about the Copernican revolution. But Galileo’s Dialogo sopra i due massimi sistemi was published in 1632 (eighty-nine years later) and we know what opposition this met. There again, the astronomies of both Copernicus and Galileo were imaginary, since they were wrong about the nature of planetary orbits.
But the most rigorous of imaginary astronomies was that of Tycho Brahe, a great astronomer and Kepler’s teacher, who admitted that planets rotate around the sun—otherwise many astronomical phenomena could not be explained—but claimed that the sun and planets rotate around the Earth, which remains immobile at the center of the universe.
Brahe’s theory was taken seriously, for example, by the Jesuits and especially by Athanasius Kircher. Kircher was a cultured man and could no longer accept the Ptolemaic system. In an illustration of solar systems in his Iter extaticum coeleste (1660 edition), alongside the Platonic system and the Egyptian system he shows us the Copernican system, explaining it accurately, but adding this note: quem deinde secuti sunt pene omnes Mathematici Acatholici et nonnulli ex Catholicis, quibus nimirum ingenium et calamus prurit ad nova venditanda. This was later accepted by almost all non-Catholic and some Catholic mathematicians, namely those who evidently had a craving to peddle new ideas in their writings. Not being of that accursed breed, Kircher thus prefers Brahe.
There were, however, very strong arguments against the idea of an Earth that moves around the sun. In his Utriusque cosmi historia of 1617, Robert Fludd uses mechanical arguments to show that if you have to turn a wheel, like that of the celestial wheel, it is easier to make it turn by exercising a force around the circumference—the point among the spheres where the primum mobile was—than by acting on the center, where the foolish Copernicans would place the sun and every generating force of life and motion. Alessandro Tassoni, in his Dieci libri di pensieri diversi of 1627, lists a range of reasons why the movement of the Earth seemed inconceivable. I will quote two of them.
Argument of the Eclipse. By removing the Earth from the center of the universe, it has to be placed either below or above the moon. If we place it below, there will never be an eclipse of the sun since the moon, being above the sun and above the Earth, will never come between the Earth and the sun. If we place it above, there will never be an eclipse of the moon, since the Earth will never be able to come between it and the sun. And what is more, astronomy could no longer predict eclipses, since it bases its calculations on the movements of the sun, and if the sun does not move, such calculations would be in vain.
Argument of the Birds. If the Earth moves, birds flying westward would never be able to keep up with its rotation and would never go forward.
Descartes, who favored Galileo’s hypothesis but never had the courage to publish his opinions about it, had developed quite an interesting theory involving vortexes, or tourbillons, in Principia philosophiae (1644). He imagined that the heavens were liquid matter, like a sea, swirling about, forming eddies or whirlpools. These vortexes carry planets with them, and the Earth is carried in a vortex around the sun. But it is the vortex that moves. The Earth remains immobile in the vortex that carries it. Descartes was shrewd in setting out these astonishing explanations—a way of getting out of the impasse between the geocentric and heliocentric arguments—as a mere hypothesis, without having to dispute the truth recognized by the church.
As Apollinaire said, Pitié, pitié pour nous qui combattons aux frontières de l’illimité et de l’avenir, pitié pour nos péchés, pitié pour nos erreurs . . . These were times when the astronomer could still commit many serious mistakes, as happened to Galileo when, through his telescope, he discovered the rings of Saturn but could not work out what they were.
First of all he declares he has seen not one single star but three joined together in a straight line parallel to the equinoctial, and represents what he has seen as three small circles. In his later writing he suggests that Saturn may appear in the shape of an olive, and finally he no longer describes three bodies or an olive, but “two semi-ellipses with two very dark little triangles in the middle of the said figures” and draws Saturn to look very much like Mickey Mouse.
Only later would Huygens describe a ring.
AN INFINITY OF WORLDS
Roaming among worlds constructed by the imagination, the imaginary astronomy of our forebears, shaded with hints of the occult, was able to create a revolutionary idea: that of the plurality of worlds. It was an idea already present among the ancient atomists—in Democritus, Leucippus, Epicurus, and Lucretius. As Hippolytus tells us in his Philosophumena, if atoms are in continuous movement in the void, they cannot but produce infinite worlds, each different from the other; and some have neither sun nor moon, for others the stars appear larger than they do for us, and from others many more stars are seen. For Epicurus, it was a hypothesis that, since it could not be contradicted, had to be taken as true until shown to be false. In the words of Lucretius (De rerum natura, book II, lines 1050–51), “Nulla est finis: uti docui, res ipsaque per se / vociferatur, et elucet natura profundi” (“There is no limit; I have shown this, the facts speak for themselves, and the nature of the void is evident”). And he continues: “Thus it is increasingly necessary you recognize that other congregations of material bodies exist elsewhere in the universe, like this of our world, which the ether encircles in eager embrace” (lines 1064–66).
Both the void and the plurality of worlds were disputed by Aristotle and, as well as Aristotle, by great scholars such as Thomas Aquinas and Roger Bacon. But when it came to the debate over the infinita potentia Dei, suspicions about the plurality of worlds would be expressed by William of Ockham, Buridan, Nicole Oresme, and others. Nicholas of Cusa spoke about an infinity of worlds in the fifteenth century, and Giordano Bruno in the sixteenth century.
The deadly poison contained in this hypothesis would emerge more clearly when it gained support from the new epicureans, the seventeenth-century freethinkers. The idea of visiting other worlds, of finding other inhabitants there, was a far more dangerous heresy than the notion of heliocentricity. The infinity of worlds casts doubt on the uniqueness of redemption: Adam’s sin and Christ’s passion are either just minor episodes relevant to our world but not to other divine creatures, or else Golgotha would have to be repeated an infinite number of times on endless planets, removing the su
blime uniqueness of the sacrifice of the Son of Man.
As Fontenelle would recall in his Entretiens sur la pluralité des mondes (1686), the suggestion was already there in the Cartesian theory of vortexes, because if every star sweeps its planets into a vortex, and the star is swept away by a larger vortex, it was possible to imagine in the sky an infinity of vortexes carrying an infinity of planetary systems.
The idea of the plurality of worlds heralded the beginning of modern science fiction in the seventeenth century, from the travels of Cyrano di Bergerac in the empires of the sun and of the moon, to Francis Godwin’s The Man in the Moone and John Wilkins’s Discovery of a World in the Moone. As to methods for takeoff, we have not yet reached Jules Verne. Cyrano, the first time, attaches to his body a great number of ampoules filled with dewdrops, and the heat of the sun, attracting the dewdrops, makes him rise. On a second occasion he uses a machine driven by firecrackers. Godwin, however, proposes an airplane ante litteram propelled by birds.