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Science
Ptolemy’s Geography, c. AD 150
Alexandria, Egypt, C. AD 150
Sailing to Alexandria by sea from the east, the first thing a classical traveller saw on the horizon was the colossal stone tower of the Pharos, on a small island at the entrance to the city’s port. At more than 100 metres high, the tower acted as a landmark for sailors along the largely featureless Egyptian coastline. During the day a mirror, positioned at its apex, beckoned sailors, and at night fires were lit to guide pilots into shore. But the tower was more than just a navigational landmark. It announced to travellers that they were arriving in one of the great cities of the ancient world. Alexandria was founded by Alexander the Great in 334 BC, who named the city after himself. Following his death it became the capital of the Ptolemaic dynasty (named after one of Alexander’s generals) that would rule Egypt for more then 300 years, and spread Greek ideas and culture throughout the Mediterranean and the Middle East.1 Gliding past the stone Pharos, a traveller entering the port in the third century BC was confronted by a city laid out in the shape of a chlamys, the rectangular woollen cloak worn by Alexander and his soldiers, an iconic image of Greek military might. Alexandria, like the rest of the civilized world at the time, was wrapped in the mantle of Greek influence, the ‘umbilicus’ of the classical world. It was a living example of a Greek polis transplanted onto Egyptian soil.
The city’s rise represented a decisive shift in the political geography of the classical world. Alexander’s military conquests had transformed the Greek world from a group of small, insular Greek city states into a series of imperial dynasties spread across the Mediterranean and Asia. This concentration of wealth and power within empires like the Ptolemaic dynasty brought with it changes to warfare, technology, science, trade, art and culture. It led to new ways of people interacting, doing business, swapping ideas and learning from each other. At the centre of this evolving Hellenistic world, stretching from Athens to India between c. 330 BC and c. 30 BC, stood Alexandria. From the west it welcomed the merchants and traders from the great Mediterranean ports and cities as distant as Sicily and southern Italy, and grew rich from its trade with the rising power of Rome. From the north, it took its cultural influences from Athens and the Greek city-states. It acknowledged the influence of the great Persian kingdoms to the east, and from the south it absorbed the wealth of the fertile Nile Delta and the vast trading routes and ancient kingdoms of the sub-Saharan world.2
Like most great cities that stand at a crossroads of people, empires and trade, Alexandria also became a nucleus for learning and scholarship. Of all the great monuments that define Alexandria, none is more potent in the Western imagination than its ancient library. Founded by the Ptolemies c. 300 BC, the Alexandria library was one of the first public libraries, designed to hold a copy of every known manuscript written in Greek, as well as translations of books from other ancient languages, particularly Hebrew. The library held thousands of books, written on papyrus rolls, and all catalogued and available for consultation. At the heart of their network of royal palaces, the Ptolemies established a ‘Mouseion’, or museum, originally a shrine dedicated to the nine Muses (or goddesses), but which the Ptolemies redefined as a place for the worship of the muses of learning and scholarship. Here, scholars were invited to study, with promises of lodging, a pension and, best of all, access to the library. From across Greece some of the period’s greatest minds were lured to work in the museum and its library. Euclid (c. 325–265 BC), the great mathematician, came from Athens; the poet Callimachus (c. 310–240 BC) and the astronomer Eratosthenes (c. 275–195 BC) both came from Libya; Archimedes (c. 287–212 BC), the mathematician, physicist and engineer, travelled from Syracuse.
The Alexandria library was one of the first systematic attempts to gather, classify and catalogue the knowledge of the ancient world. The Ptolemies decreed that any books entering the city were to be seized by the authorities and copied by the library’s scribes (although their owners sometimes discovered that only a copy of their original book was returned). Estimates of the number of books held in the library have proved notoriously difficult to make due to wildly contradictory claims by classical sources, but even conservative assessments put the number at more than 100,000 texts. One classical commentator gave up trying to count. ‘Concerning the number of books and the establishment of libraries,’ he wrote, ‘why need I even speak when they are all the memory of men?’3 The library was indeed a vast repository for the collective memory of a classical world contained within the books it catalogued. It was, to borrow a phrase from the history of science, a ‘centre of calculation’, an institution with the resources to gather and process diverse information on a range of subjects, where ‘charts, tables and trajectories are commonly at hand and combinable at will’, and from which scholars could synthesize such information in the search for more general, universal truths.4
It was here, in one of the great centres of calculation and knowledge, that modern mapmaking was born. Around AD 150 the astronomer Claudius Ptolemaeus wrote a treatise entitled , or ‘Guide to Geography’, which would become known simply as the Geography. Sitting in the ruins of the once great library, Ptolemy compiled a text that claimed to describe the known world and which would come to define mapmaking for the next two millennia. Written in Greek on a papyrus roll over eight sections, or ‘books’, the Geography summarized a thousand years of Greek thinking on the size, shape and scope of the inhabited world. Ptolemy defined his task as a geographer as being to ‘show the known world as a single and continuous entity, its nature and how it is situated, by taking account only of the things that are associated with it in its broader, general outlines’, which he listed as ‘gulfs, great cities, the more notable peoples and rivers, and the more noteworthy things of each kind’. His method was simple: ‘The first thing one has to investigate is the earth’s shape, size, and position with respect to its surroundings, so that it will be possible to speak of its known part, how large it is and what it is like,’ and ‘under which parallels of the celestial sphere each of the localities is known’.5 The Geography that resulted was many things simultaneously: a topographical account of the latitude and longitude of more than 8,000 locations in Europe, Asia and Africa; an explanation of the role of astronomy in geography; a detailed mathematical guide for making maps of the earth and its regions; and the treatise that provided the Western geographical tradition with an enduring definition of geography – in short, a complete mapmaking kit as conceived by the ancient world.6
No text before or since Ptolemy’s would provide such a comprehensive account of the earth and how to describe it. After its completion, Ptolemy’s Geography disappeared for a thousand years. No original copies from Ptolemy’s own time have survived, and it only reappeared in thirteenth-century Byzantium, with maps, drawn by Byzantine scribes, which were clearly based on Ptolemy’s description of the earth and the position of its 8,000 locations, and which show the classical world as it appeared to him in second-century Alexandria. In ascending order, the Mediterranean, Europe, North Africa, the Middle East and parts of Asia look relatively familiar. The Americas and Australasia, southern Africa and the Far East, unknown to Ptolemy, are all missing, as is the Pacific and most of the Atlantic Ocean. The Indian Ocean is shown as an enormous lake, with southern Africa running right round the bottom half of the map to join an increasingly speculative Asia east of the Malaysian peninsula. Nevertheless, this is a map that we seem to understand: oriented with north at the top, it has place names marking key regions, and is constructed using a graticule. Like most of his Greek forebears as far back as Plato, Ptolemy understood that the earth was round, and used this grid to address the difficulty of projecting a spherical earth onto a plane, or flat surface. He acknowledged that drawing a rectangular map required a graticule ‘to achieve a resemblance to a picture of a globe, so that on a flattened surface, too, the intervals established on it will be
in as good proportion as possible to the true intervals’.7
All this makes it tempting to see Ptolemy’s Geography as a remarkably early harbinger of modern mapmaking. Unfortunately, it is not that simple. Scholarly opinion remains divided as to whether or not Ptolemy ever himself drew maps to accompany the Geography: many historians argue that the thirteenth-century Byzantine copies contain the first maps to illustrate his text. Unlike disciplines such as medicine, there was no field or ‘school’ of Greek geography. There are virtually no recorded examples of the practical use of maps in classical Greece, and certainly no instances of Ptolemy’s book being used in this way.
Turning to Ptolemy’s biography to try to understand the significance of his book offers little help. Virtually nothing is known about his life. There is no autobiography, no statue, not even an account written by a contemporary. Many of his other scientific treatises remain lost. Even the Geography itself was scattered across the Christian and Muslim communities that emerged to fill the void left by the collapse of the Roman Empire. The early Byzantine manuscripts bear few clues as to how much the text had changed since Ptolemy first wrote it. The little we do know about Ptolemy is based on his surviving scientific works, and vague descriptions of him written by much later Byzantine sources. His taking the name ‘Ptolemaeus’ indicates that he was probably a native and inhabitant of Ptolemaic Egypt, which, during his lifetime, was already under the control of the Roman Empire. ‘Ptolemaeus’ also suggests, although does not prove, descent from Greek ancestors. ‘Claudius’ indicates that he possessed Roman citizenship, possibly granted to a forebear by the emperor Claudius. The astronomical observations recorded in his earliest scientific works suggest that he flourished during the reigns of the emperors Hadrian and Marcus Aurelius, giving approximate dates of a birth around AD 100, and death no later than AD 170.8 This is all that we know about Ptolemy’s life.
The creation of Ptolemy’s Geography is in some respects a paradox. Though the book is arguably the most influential in the history of mapmaking, it is uncertain, as we have seen, if it even contained maps. Its author, a mathematician and astronomer, did not regard himself as a geographer, and his life is a virtual blank. He lived in one of the great cities of late-Hellenistic learning, but at a time when its power and influence were already past their apogee. Rome had overthrown the Ptolemies in 30 BC, and oversaw the gradual decline and dispersal of the once great library. But Ptolemy was fortunate. It was only as the great flowering of the Hellenistic world began its slow decline that conditions were conducive for the creation of the book that would define both geography and mapmaking; the world had to reach its nadir before it was possible to describe its geography. If the Alexandria library assembled and then lost the ‘memory of men’, Ptolemy’s Geography represented the memory of a significant part of man’s world. But such a text still required its author’s immersion in nearly a millennium of Greek literary, philosophical and scientific speculation on the heavens and the earth before it could be written.
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Although archaic Greece had no word for ‘geography’, from at least the third century BC the early Greeks referred to what we would call a ‘map’ as pinax. The other term often used was periodos , literally ‘circuit of the earth’ (a phrase that would form the basis of many subsequent treatises on geography). Although both these terms for maps would eventually be superseded by the Latin term mappa, the later classical Greek formulation of geography has endured, formed by the compound of the noun , or earth, with the verb graphein, to draw or write.9 These terms offer some insight into the ways in which the Greeks approached maps and geography. A pinax is a physical medium on which images or words are inscribed, and periodos implies a physical activity, specifically ‘going round’ the earth in a circular fashion. The etymology of geo-graphy also suggests that it was both a visual (drawn) activity and a linguistic (written) statement. Although all these terms were increasingly used from the third century BC, they were subsumed within the more recognizable branches of Greek learning, namely mythos (myth), historia (history), or physiologia (natural science).
From its earliest beginnings, Greek geography emerged from philosophical and scientific speculations on the origins and creation of the universe, rather than any specifically practical need. Looking back on its origins while writing his own seventeen-book Geography at around the time of the birth of Christ, the Greek historian and self-styled geographer Strabo (c. 64 BC–AD 21) claimed that ‘the science of Geography’ was ‘a concern of the philosopher’. The knowledge needed to practise geography was, for Strabo, ‘possessed solely by the man who has investigated things both human and divine’.10 For the Greeks, maps and geography were part of a wider speculative enquiry into the order of things: explanations, both written and visual, of the origins of the cosmos and mankind’s place within it.
The earliest account of what we would call Greek geography appears in the work of the poet Strabo calls ‘the first geographer’: Homer, whose epic poem the Iliad is usually dated to the eighth century BC. At the end of book 18, as the war between the Greeks and Trojans reaches its climax, Thetis, mother of the Greek warrior Achilles, asks Hephaestus, the god of fire, to provide her son with armour in which to fight his Trojan adversary, Hector. Homer’s description of the ‘huge and mighty shield’ that Hephaestus fashions for Achilles is one of the earliest literary examples of ekphrasis, a vivid description of a work of art. But it can also be seen as a cosmological ‘map’, or what one Greek geographer would call a ‘kosmou ’, or ‘image of the world’,11 a moral and symbolic depiction of the Greek universe, in this case composed of five layers or concentric circles. At its centre were ‘the earth, and sky, and sea, the weariless sun and the moon waxing full, and all the constellations that crown the heavens’. Moving outwards, the shield portrayed ‘two fine cities of mortal men’, one at peace, one at war; agricultural life showing the practice of ploughing, reaping and vintage; the pastoral world of ‘straight-horned cattle’, ‘white-woolled sheep’; and finally ‘the mighty river of Ocean, running on the rim round the edge of the strong-built shield’.12
Fig. 1 The shield of Achilles, bronze cast designed by John Flaxman, 1824.
Although Homer’s description of the shield of Achilles may not immediately strike the modern reader as either a map or an example of geography, the Greek definitions of both terms suggest otherwise. Strictly speaking, Homer provides a geo-graphy – a graphic account of the earth – which gives a representation, symbolic in this instance, of the origins of the universe and mankind’s place within it. It also adheres to Greek definitions of a map as pinax or periodos : the shield is both a physical object on which words are inscribed, as well as a circuit of the earth, circumscribed within the limits of ‘the mighty river of Ocean’, which defines the boundary (peirata) of a potentially boundless (apeiron) world. Later Greek commentators saw Homer’s description as providing not just a geography, but also a story of creation itself: a cosmogony. Hephaestus, god of fire, represents the basic element of creation, and the construction of the circular shield is an allegory of the formation of a spherical universe. The shield’s four metals (gold, silver, bronze and tin) represent the four elements, while its five layers correspond to the earth’s five zones.13
As well as a cosmogony, the shield of Achilles is also a description of the known world as it appears to anyone who looks up from the horizon and gazes at the sky. The earth is a flat disc, encircled all around by sea, with the sky and stars above, and the sun rising in the east and setting in the west. This was the shape and scope of the , the Greek term for the inhabited world. Its root lay in the Greek oikos, ‘house’ or ‘dwelling space’. As the word tells us, the early Greek perception of the known world, like that of most archaic communities, was primarily egocentric, emanating outwards from the body and its sustaining domestic space. The world began with the body, was defined by the hearth, and ended at the horizon. Anything beyond this was boun
dless chaos.
For the Greeks, geography was intimately connected to an understanding of cosmogony, because to understand the origins of the earth () was to understand creation. For poets like Homer and more explicitly Hesiod in his Theogony (c. 700 BC), creation begins with Chaos, the formless mass that precedes the three other entities, Tartaros (the primordial god of the gloomy pit beneath the earth), Eros (the god of love and procreation) and, most importantly, Gaia (the female personification of Earth). Both Chaos and Gaia produce children, Nyx (Night) and Uranus (Sky). From her subsequent union with Uranus, Gaia produces the twelve Titan deities: six sons – Oceanus, Hyperion, Coeus, Cronus, Iapetus and Crius – six daughters – Mnemosyne, Phoebe, Rhea, Tethys, Theia and Themis – who in turn are defeated by the Olympian gods led by Zeus. Unlike the Christian tradition, human creation in the earliest Greek accounts is contradictory and often secondary to the struggles of the deities. Homer never provides an explicit account of mortal creation, in contrast with Hesiod, who claims that mankind is created by the Titan Cronus, but with little explanation as to why. In other versions of the myth, mortals are created by the Titan Prometheus, who incurs the wrath of Zeus by providing humans with the gift of ‘fire’, or spirit of self-conscious knowledge. In other versions of the creation myth, in Hesiod and others, mankind is denied any explicitly divine identity, and is born from the soil or earth.14
These ambiguous explanations of the birth of humanity in early Greek mythical accounts of creation contrast with emerging scientific and naturalist accounts of ‘the order of things’ which began to appear in the sixth century BC in the Ionian city of Miletus (in modern-day Turkey), among a group of thinkers who offered a recognizably scientific argument to explain creation. Miletus was well positioned to absorb the influence of Babylonian theories of creation and astronomical observations on the movement of the stars that stretched back as far as 1800 BC, represented, as we saw at the beginning of this book, on clay tablets which showed the earth encircled by water and with Babylon near its centre. The Milesian philosopher Anaximander (c. 610–546 BC) was, according to Diogenes Laertius, a third-century AD biographer, ‘the first to draw the outline of the sea and the land’, and who ‘published the first geographical map [geographikon pinaka]’.15
A History of the World in 12 Maps Page 4