ERATOSTHENES ( MÖ.276-MÖ.194)
Arşimet'ten sonra en büyük öncülerden biridir Eratosthenes. Geniş bilgisi, pek çok konularda yazdığı kitaplarıyla daha yaşam döneminde ün kazanan Eratosthenes, İskenderiye Kütüphanesi'nin de 2.yöneticisiydi.
Arzın küresel olduğunu ileri süren, güneşin dünyadan uzaklığını 92 milyon mil olarak hesaplayan da odur. (Gerçek uzaklık 93 milyon mildir!)
Eratosthenes özellikle coğrafya alanındaki çalışmalarıyla tanınırdı. ama onu bilim tarihinde unutlmazlar arasına sokan asıl başarısı, arzın çevrel çemberinin uzunluğunu belirleme çalışmasıdır.
Asıl amacı güneş ile Ay'ın boyutlarını belirlemek, dünyadan uzaklığını hesaplamaktı. Ama bunun için öncelikle arzın büyüklüğünü bilmesi gerekiyordu. hiç bir optik araç yoktu, gözlemsel bilgi ve geometrik kurallar gerektiriyordu. Örneğin: Arzın küreselliği, daire çemberinin 360 derece olduğu, güneş ışınlarının yer yüzüne paralel düştüğü, vb.
Bilindiği gibi yer yüzeyi düz değil, eğmeçlidir. Bu nedenle gün ortasında güneş değişik yüksekliklerde görünür. bu gözlemi dikkate alan Eratosthenes yaklaşık aynı boylam ve üzerine düşen iki yer seçer. Bunlardan biri Syene (bugünkü Asvan barajına yakın bir kasaba) , diğeri dönemin en ünlü bilim merkezi İskenderiye kenti idi. Syene'de yaz ortasında güneş öğle vakti tam tepede bir konumdadır ; öyle ki , dik duran bir direk gölge düşüremediği gibi , derin bir kuyu dibinden bakıldığında, güneş görülür. İskenderiye'de ise durum değişiktir. Syene'nin yaklaşık 514 mil kuzeyinde bulunan bu kentte güneş ışınları hiç bir zaman dik düşmez.
Eratosthenes bu verilere dayanarak İskenderiye'de güneş ışınlarının arzın merkezine dik inen bir dooğru üzerinde oluşturduğu açıyı ölçer. Adı geçekn iki yerin arzın merkezinde oluşturdukları açıya eşit olan ve iki yer arasındaki mesafeyi temsil eden bu açı yaklaşık 7,5 derecedir. Her daire çemberi gibi yer kürenin çevrel çemberinin de 360 derece olduğunu varsayan Eratosthenes basit bir orantı işlemiyle bu çemberin 24.670 mil olduğunu hesaplar. (doğrusu 24.870 mildir !) Bu kadarla da kalmaz , 60 millik bir hatayla arzın çapını da belirler.
Teknolojinin henüz bazı basit el araçlarının ötesine geçmediği bir dönemde bu türden sonuçlara ulaşma gerçekten olağanüstü bir zeka ve imgelem gücü demekti.
Eratosthenes'in azımsanamayacak bir başarısı da ,o zaman bilinen dünyanın haritasını çıkarmasıdır. Harita İngiliz adaları dahil Avrupa, Afrika ve Asya anakaralarını kapsıyordu. Küresel bir yüzeyi düz kağıt parçasına çizmek kolay değildi. Tıpkı bir portakal kabuğunu masa üzerine dümdüz yerleştirmek gibi. Eratosthenes enlem paralelleriyle boylam meridyenlerini kullanarak oldukça duyarlı ve güvenilir bir projeksiyonla güçlüğün üstesinden gelmişti. Yaptığı harita yüzyıllarca denizcilikte ve başka alanlarda kullanıldı.
Hint ve Atlas okyanuslarındaki gelgit devinimleri arasındaki yakın benzerliği göz önüne alarak iki okyanusun aslında birleşik olduğunu, üç anakaranın (Avrupa-Asya ve Afrika) da bir ada oluşturduğunu ileri sürer. Kimi kaynaklara göre de Atlantik ötesi yeni bir anakaranın varlığından bile söz etmiştir. Ona göre okyanusun öte yakasında bilinen dünyayı dengeleyen bir başka dünyanın varlığı büyük bir olasılıktı.
Roma yönetiminde zamanla İskenderiye'deki parlak bilim meşalesi sönmeye yüz tutar. O dönemin bilim öncülerinin son temsilcisi Hero'nun matematik, fizik ve teknolojideki başarılarını, kendisinden 300 yıl önce yaşamış Eratosthenes'e borçlu olduğunu söylemiş olması ,büyük bilginin bilim dünyasındaki kalıcı etkisini yansıtmaktadır.
Eratosthenes 81 yaşında öldüğünde en küçük bir mal varlığı yoktu. Ama bıraktığı dünya doğduğundaki dünyadan bilgi birikimi ve araştırma yöntemi bakımından çok daha zengindi.
Bilimin Öncüleri - Cemal Yıldırım
Eratosthenes' "Geography" - Duane W. Roller
This is the first modern edition and first English translation of one of the earliest and most important works in the history of geography, the third-century Geographika of Eratosthenes. In this work, which for the first time described the geography of the entire inhabited world as it was then known, Eratosthenes of Kyrene (ca. 285-205 BC) invented the discipline of geography as we understand it. A polymath who served as librarian at Alexandria and tutor to the future King Ptolemy IV, Eratosthenes created the terminology of geography, probably including the word geographia itself. Building on his previous work, in which he determined the size and shape of the earth, Eratosthenes in the Geographika created a grid of parallels and meridians that linked together every place in the world: for the first time one could figure out the relationship and distance between remote localities, such as northwest Africa and the Caspian Sea. The Geographika also identified some four hundred places, more than ever before, from Thoule (probably Iceland) to Taprobane (Sri Lanka), and from well down the coast of Africa to Central Asia.
This is the first collation of the more than 150 fragments of the Geographika in more than a century. Each fragment is accompanied by an English translation, a summary, and commentary. Duane W. Roller provides a rich background, including a history of the text and its reception, a biography of Eratosthenes, and a comprehensive account of ancient Greek geographical thought and of Eratosthenes' pioneering contribution to it. This edition also includes maps that show all of the known places named in the Geographika, appendixes, a bibliography, and indexes.
Crates of Mallos
These slides show modern reconstructions of the globe of Crates of Mallos, which was originally constructed at Pergamum in Asia Minor in 180 B.C. The various measurements of the earth's size by Eratosthenes raised a curious problem. The known dimensions of the oikumene [inhabited world] were too small relative to the estimated size of the earth sphere, the oikumene occupied only one quadrant of the sphere. Such an imbalance in a spherical object was contrary to the Greek sense of symmetry. Crates, therefore, solved the problem on his globe by drawing three other "continents " (an anticipation/prediction of the existence of the Americas, Antarctica and Australia) to provide the necessary "balance" and symmetry. Here was born the concept of the "Antipodes", or the great southern continent, the "Terra Australis", that would be conjured up in medieval and renaissance period maps.
It appears to have been the polymath grammarian Crates of Mallos, a contemporary of Hipparchus, and a member of the Stoic School of Philosophers, who made the first recorded attempt to construct a terrestrial globe, and that he exhibited the same in Pergamum, not far from the year 150 B.C. About 168 B.C. Crates, who wrote among other things on Homer and the wanderings of Odysseus, visited Rome.
He was professionally interested in the city's drainage system, but while exploring the Cloaca Maxima broke his leg. He used the period of recovery to give lectures in Rome, which are said to have created a great impression. His view of terrestrial mapping was that the shape could only be right if it was drawn on a globe, and eventually that the scale could only be effective if the globe was at least ten feet in diameter. In designing his 'orb', if indeed he put his theory into practice, Crates favored an unusual form of symmetry. There were, he said, separated by two intersecting belts of ocean, four symmetrical landmasses:
(a) Europe, Asia and the part of Africa known at that time;
(b) south of them, that of the Antoikoi, 'dwellers opposite';
(c) west of them, the Perioikoi, 'dwellers round';
(d) south of the Perioikoi, the Antipodes.
The break between the landmass known at that time and that of the Antoikoi came, according to him, at a belt on each side of the equator, and there were Ethiopians (Aethiopes, 'black-faces') on each side of this water divide. Homer had written of the Ethiopians, split in two, some in the East, some by the setting sun. Later Greek writers interpreted this passage in various ways. No doubt, as a Homeric scholar, Crates was more concerned to give a plausible account of Homeric descriptions than to investigate explanations which suggested the existence of a continuous African landmass stretching across the equator. The idea however, was taken up by Cicero in the somnium Scipionis [ 'Dream of Scipio'] which he incorporated in his De republica. When Macrobius wrote a commentary on the somnium Scipionis about AD 390, he defended and amplified Crates' theory, aspects of which thus found their way into medieval cartography; the Perioikoi and Antipodes were then omitted, although discussed by Cicero and Macrobius .
It seems to have been Crates' idea that the earth's surface, when represented on a sphere, should appear as divided into four island-like habitable regions. On the one hemisphere, which is formed by a meridional plane cutting the sphere, lies our own oikumene, and that of the Antoecians in corresponding longitude and in opposite latitude; on the other hemisphere lies the oikumene of the Perioecians in our latitude and in opposite longitude, and that of the Antipodes in latitude and longitude opposite to us. Through the formulation and expression of such a theory the existence of an antipodal people was put forth as a speculative problem, an idea frequently discussed in the Middle Ages, and settled only by the actual discovery of antipodal regions and antipodal peoples in the day of great transoceanic discoveries of the 17th and 18th centuries.
A belief in the existence of antipodal peoples, very clearly was also accepted by Pythagoras, Eratosthenes, Posidonius, Aristotle, Strabo, and later Capella. Numerous others presupposed the earth to be globular in shape. [see Kretschmer, K., Die physische Erdkunde im christlichen Mittelalter. Wien, 1889. pp. 54-59, wherein the author gives consideration to the doctrine of the Antipodes as held in the Middle Ages. Berger, Geschichte, pt. 3, p. 129, notes that the idea of the earth's division into four parts or quarters persisted for centuries after Crates' day, if not among scientific geographers, at least among those who could be said to have possessed general culture. Cleomedes, Ampelius, Nonnus, and Eumenius mention the idea as one to be accepted.
It was thought that Africa did not extend to the equator, or at least was not habitable to the equator. Below the equator there was thought to be water but beyond the uninhabitable and impassable torrid zone, a habitable region existed. The map of Lambertus well represents this early theory. Pomponius Mela called the inhabitants of this southern region Antichthoni, their country being unknown to us because of the torrid zone intervening. Pliny, and after him Solinus, says that for a long time the island of Taprobana [Ceylon/Sri Lanka] was thought to be the region occupied by the Antichthoni.
That Strabo , at a later date, had this Pergamenian example in mind when stating certain rules to be observed in the construction of globes seems probable, since he makes mention of Crates' globe. Strabo alone among ancient writers, so far as we at presently know, treats terrestrial globes practically. He thought that a globe to be serviceable should be of large size, and his reasoning can readily be understood, for what at that time was really known of the earth's surface was small indeed in comparison with what was unknown. Should one not make use of a sphere of large dimensions, the habitable regions in comparison with the earth's entire surface, would occupy but small space. What Strabo states in his geography is interesting and may here well be cited.
Whoever would represent the real earth as near as possible by artificial means, should make a sphere like that of Crates, and upon this draw the quadrilateral within which his chart of geography is to be placed. For this purpose however a large globe is necessary since the section mentioned, though but a very small portion of the entire sphere, must be capable of containing properly all the regions of the habitable earth and of presenting an accurate view of them to those who wish to consult it. Anyone who is able will certainly do well to obtain such a globe. But it should have a diameter of not less than ten feet; those who cannot obtain a globe of this size, or one nearly as large, had better draw their charts on a plane surface of not less than seven feet. Draw straight lines for the parallels, and others at right angles to these. We can easily imagine how the eye can transfer the figure and extent (of these lines) from a plane surface to one that is spherical. The meridians of each country on the globe have a tendency to unite in a single point at the poles; nevertheless on the surface of a plane map there would be no advantage if the right lines alone which should represent the meridians were drawn slightly to converge.
Crates' motive for his cartography was partly literary, interpreting Ulysses' wanderings, and historical rather than purely scientific. As a Stoic, he proclaimed Homer the founder of geography, crediting him with belief in a spherical earth and commenting on his poems accordingly. To explain Homer's line, "The Ethiopians who dwell sundered in twain, the farthermost of men", Crates argued that on each side of an equatorial ocean there lived the Ethiopians, divided by the ocean, one group in the Northern Hemisphere, the other group in the Southern, without any interchange between them. Again Strabo reports:
Crates, following the mere form of mathematical demonstration, says that the torrid zone is "occupied" by Oceanus, and that on both sides of this zone are the temperate zones, the one being on our side, while the other is on the opposite side of it. Now, just as these Ethiopians on our side of Oceanus, who face the south throughout the whole length of the inhabited world, are called the most remote of the one group of peoples, since they dwell on the shores of Oceanus, so too, Crates thinks, we must conceive that on the other side of Oceanus also there are Ethiopians, the most remote of the other group of peoples in the temperate zone, since they dwell on the shores of this same Oceanus.
The scientific thinking behind the geography of Crates' globe was derived directly from the teaching of Eratosthenes about the relative size of the known world. By combining the geometric approach of his predecessor with his own interpretation of Homer , he represented four inhabited worlds on the surface of his terrestrial globe. Two were in the Northern Hemisphere, the one where the Greeks lived, occupying far less than half of the Northern Hemisphere, and another symmetrically situated in the other half. Two other inhabited worlds are found in the Southern Hemisphere, symmetrical with the two north of the equator. These four worlds were separated by oceans along the equator (occupying the torrid zone made uninhabitable by heat) and along a meridian. The inhabited areas were thus islands, with no communication between them.
It is clear that this conception of four symmetrical land areas was a direct consequence of the geometry of the sphere and the size Eratosthenes attributed to the inhabited world in relation to the total globe. Crates demonstrated this by drawing the four areas on the surface of his globe and suggesting that the three unknown lands could be similar to the known one. To give it further credibility, he also drew in the main parallel circles, emphasizing those defining the zones: these were the tropics (at 24° distance from the equator), between which flowed the Ocean as envisaged by Homer, and the two polar circles (at 66° distance from the equator).
Crates' globe was thus a product of theoretical mathematical cartography, communicating an image of the world that was very far from reality. Our understanding of the globe's physical characteristics is meager, and there is no evidence to suggest how or of what material it was made, but its influence on the history of cartographic thought has been considerable. The concept of the equatorial ocean was transmitted to medieval Europe through Macrobius' commentary on Cicero's Dream of Scipio. Scholars of later times also vied eagerly to give adequate names to these unknown worlds, but on the whole they did not doubt their existence. (this globe only exists as a reconstruction)
Posidonius' World Map ,150-130 B.C. - Posidonius (Petrus Bertius)
This slide shows a 1630 reconstruction by Petrus Bertius (Pieter Bert) of the world view of the Greek philosopher Posidonius who proposed that the earth was sling-shaped, broad in the middle, with tapered ends and an estimated circumference that was three-quarters of its true size, resulting in an oikumene [inhabited world] that stretched half way around a globe. The Bertius reconstruction, published in his Ancient Geography (Paris, 1630), represents a literal interpretation of Posidonius' "sling", complete with looped handles.
The better-known contemporary of Theodosius, Posidonius(ca. 135-51/50 B.C.),is generally associated with his measurement of the circumference of the earth. By some scholars, who view the history of mapping as mainly concerned with the diagnosis of increasing accuracy, this measurement has been "deemed disastrous in the history of geography." Depending on the value of the stade that is adopted, it may be true that Posidonius, seeking to improve on Eratosthenes, underestimated the size of the earth, and this measurement, copied by Ptolemy, was thereafter transmitted to Renaissance Europe.
But Posidonius clearly did more than measure the earth: such was his reputation as an educator that Strabo described him as "one of the most learned philosophers in our time." He was born in Apamea in Syria; after traveling widely in the western Mediterranean countries and visiting Rome on several occasions, he established himself in Rhodes, where he opened a school. This was patronized by distinguished visitors, including Pompey, the Roman general and statesman, and Cicero, from whom some of our knowledge of Posidonius derives. It was also at Rhodes that he constructed a planetarium in the style of Archimedes, intended for teaching students the laws of the cosmos. Cicero describes "the orrery recently constructed by our friend Posidonius, which at each revolution reproduces the same motions of the sun, the moon and the five planets that take place in the heavens every twenty-four hours."
Besides demonstrating his mechanical skill in this way, Posidonius was engaged in reassessing some of the theories about the earth current in his day. Indeed, in this respect his writing was to serve as an important conceptual link between cartography in the ancient and medieval worlds. In his treatise The Ocean (now lost but known to us through Strabo), for example, he discussed the problem of terrestrial zones, which is relevant to an understanding of the zonal mappaemundi of the Middle Ages.
In this text, inspired by the work of Pytheas, Posidonius began by criticizing the usual division of the earth into five zones - one uninhabited (torrid) zone, two inhabitable (temperate) zones, and two uninhabited (frigid) zones - for he considered the limits between them to be uncertain and inaccurate. According to Strabo's Geography ,Posidonius criticized Parmenides' division of the earth into five zones because he represented the torrid zone as almost double its real breadth, and he criticized Aristotle for calling the region between the tropics "torrid" and the regions between the tropics and the arctic circles "temperate." Posidonius disagreed with both Parmenides and Aristotle and asked "how one could determine the limits of the temperate zones, which are nonvariable, by means of the 'arctic circles,' which are neither visible among all men nor the same everywhere." Instead of employing the traditional terms for the zones, based on temperature or habitability, he proposed terms based on clearly defined astronomical criteria. He divided the terrestrial globe by means of the tropics and the polar circles and named the zones as in the table below.
POSIDONIUS' TERRESTRIAL ZONES
ZONE AREA MEANING
Amphiskian Between the tropics Where the shadow of the
(one zone) gnomon is directed alternately
to the north and to the south.
Heteroskian Between each tropic Where the shadow of the
(two zones) and each polar circle
gnomon is directed either
to the north or to the south,
depending on the hemisphere.
Note: The Greek skia means shadow.
At the same time, Posidonius appreciated that if he altered the criteria for the division, so as to take temperature distribution more fully into account, the earth could be divided into seven zones. These he identified as the two frigid zones around the poles, the two temperate zones in their usual places, two narrow, extremely arid zones along the terrestrial tropics having the sun directly over head for about half a month each year, and finally the equatorial zone, more temperate and better watered than the two tropical ones. At one point Posidonius also proposed dividing the inhabited world not into continents, as was usual in his day, but by means of circles parallel to the equator, indicating variations in fauna, flora, and climate. However, Strabo commented unfavorably on this innovative idea. It was, he said, "a mere matter of argument, with no useful end in view."
Equally revisionist was Posidonius' challenge to Eratosthenes' measurement of the circumference of the earth. Our knowledge of his methods, as with the earlier reasoning of Eratosthenes, is derived from Cleomedes, and it becomes clear that it was based on assumptions that were sometimes false. These assumptions included the belief that Rhodes and Alexandria lay on the same meridian and that the distance between the two places was 5,000 stades. Then Posidonius (according to Cleomedes), noting that Canopus was seen just on the horizon at Rhodes but rose as far as a quarter of a zodiacal sign (7.5°) above the horizon at Alexandria, concluded that the center angle intercepting the Rhodes-Alexandria arc of meridian was one-forty-eighth of the total circle or 4.5° (the arc is actually 5°14') . Thus, he argued, the total length of the meridian was forty-eight times the distance between Rhodes and Alexandria, and, assuming this latter to be 5,000 stades, this gave a figure of 240,000 stades for the circumference of the earth.
This, however, is only a partial history of the confusion attached to the measurement. As a teacher interested in promoting discussion, Posidonius seems to have criticized his own assumptions, in particular the estimate of 5,000 stades for the distance from Rhodes to Alexandria. Evidently, at some point in his calculations he employed an alternative value of 3,750 stades, derived from a careful estimate Eratosthenes made "by means of shadow-catching sundials." When applied to the 1:48 ration, this gave a correspondingly smaller length for the circumference of the earth of 180,000 stades.
What is important for the history of cartography is that it was this measurement - whether directly or through an intermediary -that was later adopted by both Marinus of Tyre and Ptolemy. Its main effect was greatly to exaggerate the portion of the globe occupied by the inhabited world, so that the length from the Straits of Gibraltar to India, along the parallel of Rhodes, came to be considered half of the entire parallel around the earth. And such was the authority of Ptolemy that this misconception was carried forward by geographers, cosmographers, and cartographers into the sixteenth century. Historians of discovery have noted that it long colored the perception of that age as to the size of the unknown portion of the world. Most famously in Columbus' belief in the proximity of the Indies when sailing westward. (this map only exists as a reconstruction)
Strabo's World Map, A.D. 18
This slide shows a 19th century reconstruction of the world view of the Greek philosopher Strabo who wrote his famous geography at the beginning of the Christian era and compiled his map from travelers' reports and the "writings" of ancients. The now lost map by Strabo represented the sum total of cartographic knowledge before the Christian Era.
The contribution of Strabo as a scholar of great stature as philosopher, historian, and geographer, epitomizes the continuing importance of the Greek intellectual heritage - and contemporary practice - to the development of cartography in the early Roman world. As the reviser of Eratosthenes, he also illustrates the continuous way later generations had built on the cartographic concepts first clearly set out in the Hellenistic Age.
We are fortunate in possessing all seventeen books of the Geographia by Strabo, written in good Greek although he himself was mixed Asiatic and Greek stock; it is through his writings that most of our knowledge of Eratosthenes' mapping has come down. He was born at Amasia [Amasya] in Pontus in 64 or 63 B.C. Strabo was educated at Nysa near Tralles in Caria and in 44 B.C. went to Rome, where he studied under the Phoenician freedman Tyrannio and the Stoic philosopher Athenodorus. He showed himself a keen supporter of Augustus and visited Rome several times. From about 25 to 20 B.C. he was in Egypt, based at Alexandria. His Geographia was written between 9 and 5 B.C. and parts revised in AD 18-19. Surprisingly, though, it seems not to have been read in Rome in the first century, judging from the fact that it is not even mentioned by the elder Pliny.
Strabo claimed to have traveled widely to bring together an enormous amount of geographical knowledge. It is generally accepted, however, that he must have compiled much of this information in the great library at Alexandria, where he had access to many earlier texts now lost. All his writings were firmly set in, if not direct extensions of, the work of his predecessors. Thus his Historical Memoirs in forty-seven books, now lost, was a continuation of Polybius. The Geographia is of key importance to our whole knowledge of the history of Greek cartography as well as to the history of science in general. Cortesão states that as a source it was "second to none in the history of geography and cartography" of this period. Many of the earlier treastises that touch upon maps are known to us only through Strabo, while the interest of his commentary on these writers is in its critical handling of their theories, albeit he sometimes fails to advance truth by this process.
In many ways the most interesting passages relating to cartography in Strabo's Geographia are those that, although they contain no maps, give an account, for the first time in a surviving text, of how a description of the known world should be compiled. His motives for writing such a geography (so he tells us) were that he felt impelled to describe the inhabited world because of the considerable strides in geographical knowledge that had been made through the numerous campaigns of the Romans and Parthians. The world map had to be adjusted to take account of these facts, and thus Strabo almost certainly proceeded by taking Eratosthenes' map - and the criticism of it by Polybius, Crates, Hipparchus, and Posidonius - as the basis for his own work.
In this task of compilation Strabo seems to have worked systematically. The first stage was to locate the portion of the terrestrial globe that was known to be inhabited. Strabo reasoned that it lay in a northern quadrant of a globe, in a quadrilateral bounded by the frigid zone, the equator, and two meridians on the sides. Strabo locates the frigid zone, or arctic circle, at 54° distance from the equator. The so-called quadrilateral, bounded by half of this arctic circle, half of the equator, and segments of two meridians, is a spherical quadrilateral, a portion of a sphere. In this design Strabo had been influenced not only by Eratosthenes' measurement of the earth but also by the concept of the four inhabited worlds, known and unknown, expounded by Crates , to whom he refers explicitly. Thus far Strabo had relied on theoretical argument derived from his authorities. But he also adduced good empirical grounds for this cartographic reasoning. He continued:
But if anyone disbelieves the evidence of reason, it would make no difference, from the point of view of the geographer, whether we make the inhabited world an island, or merely admit what experience has taught us, namely, that it is possible to sail round the inhabited world on both sides, from the east as well as from the west, with the exception of a few intermediate stretches. And, as to these stretches, it makes no difference whether they are bounded by sea or by uninhabited land; for the geographer undertakes to describe the known parts of the inhabited world, but he leaves out of consideration the unknown parts of it - just as he does what is outside of it. And it will suffice to fill out and complete the outline of what we term "the island" by pining with a straight line the extreme points reached on the coasting-voyages made on both sides of the inhabited world.
Despite the extension of the geographical horizons of the inhabited world since the time of Eratosthenes, Strabo's oikumene [inhabited world] was smaller. Although Pythæs, Eratosthenes, and perhaps Posidonius had fixed its northern limit on the parallel through Thule [Iceland ? 66° N], Strabo, like Polybius, refused to believe that human life was possible so far north, and he blamed Pytheas for having misled so many people by his claim that the "summer tropic" becomes the "arctic circle" at the island of Thule. Again following Polybius, Strabo thus chose as the northern limit of the map and of the inhabited world the parallel through Ierne [Irelandl, "which island not only lies beyond Britain but is such a wretched place to live in on account of the cold that the regions on beyond are regarded as uninhabitable." This parallel (54° N) is the projection of the celestial arctic circle constructed for the latitude of Rhodes (36° N); it coincides with the one mentioned by Geminus as the northern limit of the temperate zone. The southern limit of habitable land, for Strabo as for Eratosthenes, is the parallel through the "Cinnamon-producing country" [Ethiopia/Somaliland] at about 12° N. He estimated the latitudinal extent of the inhabited world as less than 30,000 stades (compared with Eratosthenes' 38,000 stades) and reduced its length to 70,000 stades instead of Eratosthenes' 78,000.
In order to avoid the deformational problems of flat maps, Strabo stated that he preferred to construct his map on a globe large enough to show all the required detail. He recommended that it be at least ten feet (approximately three meters) in diameter and mentions Crates in this regard. On the other hand, if a globe of this size could not be constructed, Strabo was familiar from Eratosthenes with the transformation necessary to draw it on a plane surface. For a graticule, Strabo adopted the straight forward rectangular network of parallels and meridians. He defended his projection on the ground that it would make only a slight difference if the circles on the earth were represented by straight lines, "for our imagination can easily transfer to the globular and spherical surface the figure or magnitude seen by the eye on a plane surface." The dimensions of this flat map were also to be generous. Strabo envisaged that it would be at least seven feet long and presumably three feet wide, which would suit the length of the inhabited world (70,000 by 30,000 stades ), one foot being equivalent to 10,000 stades. Taking eight stades to a Roman mile, the scales becomes 1:6,250,000.
As with all Greek world maps, the great impediment to study for the historian of cartography is that we have only these verbal descriptions, not the images themselves. Nevertheless, apart from the reduced size of the inhabited world, the map Strabo envisaged was similar in its overall shape to that drawn by Eratosthenes . In describing its detailed geography, however, Strabo did not employ, at least overtly, Eratosthenes' division of the world into irregular quadrilaterals or sphragides, but he often used geometric figures or comparisons to everyday objects to describe the general outline of a country. For instance, he says that the province of Gallia Narbonensis presents the shape of a parallelogram; that the rivers Garumma [Garonne] and Liger [Loire] are parallel to the Pyrenæus [Pyrenees], forming with the ocean and the Cemmenus Mountains [Cevenne] two parallelograms; that Britain is triangular; that Italy has been shaped sometimes like a triangle, sometimes like a quadrilateral; that Sicily is indeed triangular, though one side is convex and the two others slightly concave. Similarly, Strabo compares the shape of Iberia to an ox-hide, the Peloponnese to a plane-leaf; and the northern part of Asia, east of the Caspian, to a kitchen knife with the straight side along the Taurus range and the curved side along the northern coastline. India, with two adjacent sides (south and east) much longer than the two others, he described as Rhomboidal; Mesopotamia, between the Tigris and Euphrates rivers, he saw as being like a boat drawn in profile, with the deck on the Tigris side and the keel near the Euphrates. Strabo repeats that the river Nile was described by Eratosthenes as a reversed N, and that its mouth was named after the Greek capital letter delta.
It is not clear how we should interpret these familiar graphic similes Strabo employed to describe to his readers the land areas and other features on the world map. But they do suggest that he was writing with a map in front of him. In some cases, where alternative descriptions are provided, he may have been attempting to collate the outlines of more than one map. It is also probable that students were expected to consult the text of the Geographia with the help of maps, so that the shapes thus enumerated may have served as a simple mnemonic. Yet if such suggestions must remain speculative, there can be little doubt that by the early Roman period world maps and globes drawn by Greek scholars were encouraging a distinctively geographical way of thinking about the world. And it is likely, among the educated group at least, that an increasingly standard image of the inhabited world had come to be more widely accepted through the use of these maps.
Strabo was a lengthy and discursive writer, but demonstrated good critical power in assessing earlier geographical writers and has given us a verbal picture of the known world of the time. He treats Homer as the first writer on geography, and defends the Homeric picture of the known world as substantially true. But within the Homeric chapters he has a section in which he attempts to analyze navigation of the oceans over the ages. Thus he says: "It is not reasonable to suppose that the Atlantic consists of two seas, confined by narrow isthmuses so as to prevent circumnavigation; rather it must be confluent and continuous." His argument is that explorers tried to sail around Africa but turned back when not obstructed by any landmass. The problems of the armchair geographer are revealed in the journalistic trick of quotes from quotes on an important exploration: 'Posidonius says Herodotus thinks that certain men sent by Neco completed the circumnavigation'. This is all he reports, so that we have to beware of using all his work as scientifically worthy material. Perhaps because he is drawing on an account at second hand, he is afraid to support what may have seemed like science fiction. He does not deal extensively with Hanno the Carthaginian, instead spending much effort on questioning the explorations of Eudoxus of Cyzicus, who must have added to the accumulation of knowledge about the remote parts of Africa.
Strabo likes to represent myths and poetic phraseology geographically. Thus he says that the legend of the Golden Fleece brought back from Colchis by the Argonauts reflects the search for gold by early Greeks in areas of the Black Sea. When Homer made Hera say: "For I shall see the bounds of fertile earth and Oceanus, father of the gods", what he means, says Strabo, is that the Ocean touches all the extremities of the land. Or again, when Homer describes Odysseus as seeing land as he was on the crest of a great wave, he must have been referring to the curvature of the earth, a phenomenon familiar to sailors. Some of this was polemic against Eratosthenes, who would not have if that early epic poetry could contribute anything to scientific theory.
The most detailed examination of a term arising from Homeric geography is in respect of Ethiopians. What did Homer mean by saying they were 'divided in two, some where Hyperion rises and some where he sets'? The historian Ephorus (c.405-330 B.C.) mentioned an early tradition that Ethiopians had overrun Libya, i.e. north Africa, as far as Dyris [the Atlas Mountains], and that some had stayed there . Crates' view was based upon an unorthodox view that the division was north-south rather than the obvious interpretation of east-west. Aristarchus of Samothrace (ca. 155 B.C.) criticized Crates' interpretation, but claimed that Homer was simply wrong and there was only one area in which Ethiopians lived. Strabo's own view is that there were two groups of Ethiopians, one living in Asia and one in Africa; and that Homer thought likewise, though not to the extent of placing the eastern group in India, of which he had no knowledge. However, this idea of eastern Ethiopians living in some area of India and resembling Indians in appearance and customs persisted throughout antiquity.
The function of geography, according to Strabo, is to be an interpreter, not of the whole world, but of the inhabited world. Thus, accepting Eratosthenes' measurement of 252,000 stades for the circumference of the earth, the geographer ought not to include the equatorial zone, since that in Strabo's view is uninhabitable. Instead he should start his analysis with the Cinnamon Country [near the mouth of the Red Sea, Somaliland], about 8,800 stades north of the equator, in the south, and with Ireland in the north. He categorizes regions from south to north according to greatest length of day in equinoctial hours. This list, starting at Meroe with thirteen hours and ending at an area north of the Sea of Azov with seventeen hours, is similar to that given by the elder Pliny. As mentioned earlier, in the extreme north, Strabo denied the existence of a Thule Island [Iceland ?]. To him the most northerly inhabited area was Ierne [Ireland], itself 'only wretchedly inhabitable because of the cold, to such an extent that regions beyond it are regarded as uninhabitable'. Likewise, if one were to go not more than 4,000 stades [500 Roman miles] north from the center of Britain, one would find an area near Ireland, which like the latter would be barely inhabitable.
Strabo's idea of the shape of the inhabited world is defined as follows:
Let it be taken as hypothesis that the earth together with the sea is spherical . . ., though not as complete a sphere as if turned on a lathe . . . Let the sphere be thought of as having five zones. Let the equator be conceived as a circle on n, and let a second circle be conceived parallel to it, delimiting the frigid zone in the northern hemisphere, and through the poles a circle cutting these at right angles. Then, since the northern hemisphere contains two-fourths of the earth . . ., in each of these fourths a quadrilateral is delimited . . . In one of these two quadrilaterals . . . we say that an inhabited world is settled, surrounded by sea and like an island.
He goes on to suggest that the quadrilateral in which the Atlantic lies resembles in shape half the surface of a spinning-wheel, and that the oikumene [inhabited world] resembles a chlamys, a Greek mantle. This suggests that the eastern and western extremities of the oikumene were thought of as tapering and convex. Again, he estimated the length of the oikumene as 70,000 stades and its width as less than 30,000.
As the ideal method of mapping the world, Strabo writes in far more cartographic terms than before,
We have now inscribed on a spherical surface the area in which we say the inhabited world is settled; and anyone most closely modelling reality by means of man-made representations should make a sphere of the earth, as Crates did , mark off the quadrilateral on it, and inside this should place his map of the geographia,i.e., of the inhabited world. But one needs a large globe, so that the section mentioned, being only a fraction of it, may clearly show the appropriate parts of the oikumene, which win present a recognizable shape to users. If one can construct such a globe, it should be not less than 10 feet in diameter. If one cannot make it as big or not much smaller, one should construct a map of the oikumene on a plane surface at least seven feet long. For it will make little difference if instead of the circles, vis. parallels and meridians, we draw straight lines between which to place the klimata with the winds and the other differences, and the positions of parts of the earth relative to each other and to celestial phenomena.
He goes on to say there is little point in making the meridians converge slightly in such a map, so was it rectangular, a forerunner of something like Mercator's projection?
Like Herodotus , Strabo had travelled himself from Armenia and western Italy, from the Black Sea to Egypt and up the Nile to Philæ. But his seventeen volumes-vastly important to his contemporaries- read like a romance to us today, and a glance at the map laid down according to his descriptions is like a vague and distorted caricature of the real thing. And yet, according to the men of his times, he "surpasses all the geographical writings of antiquity, both in grandeur of plan and in abundance and variety of its materials."
Strabo has summed up for us the knowledge of the ancient world as it was in the days of the Emperor Cæsar Augustus of the great Roman Empire, as it was when in far-off Syria the Christ was born and the greater part of the known earth was under the sway of Rome. A wall-map had already been designed by order of Augustus to hang in a public place in Rome - the heart of the Empire - so that the young Romans might realize the size of their inheritance, while a list of the chief places on the roads, which, radiating from Rome, formed a network over the Empire, was inscribed on the Golden Milestone in the Forum.
Strabo begins his book with a detailed account of southern Spain where he tells of her two hundred towns.
Those best known are situated on the rivers, estuaries, and seas; but the two which have acquired the greatest name and importance are Cordova and Cadiz. After these Seville is the most noted . . . A vast numberof people dwell along the Guadalquivir, and you may sail up it almost a hundred and twenty miles from the sea to Cordova and the places a little higher. The banks and little inlets of this river are cultivated with the greatest diligence. The eye is also delighted with groves and gardens, which for this district are met with in the highest perfection. For fifty miles the river is navigable for ships of considerable size, but for the cities higher up smaller vessels are employed, and thence to Cordova river-boats. These are not constructed of planks pined together, but they were formerly made out of a single trunk. A chain of mountains, rich in metal, runs parallel to the Guadalquivir, approaching the river, sometimes more, sometimes less, toward the north.
He grows enthusiastic over the richness of this part of southern Spain, famous from ancient days under the name of Tartessus for its wealth.
Large quantities of corn and wine are exported, besides much oil, which is of the first quality, also wax, honey, and pitch . . . the country furnishes the timber for their shipbuilding. They have likewise mineral salt and not a few salt streams. A considerable quantity of salted fish is exported, not only from hence, but also from the remainder of the coast beyond the Pillars. Formerly they exported large quantities of garments, but they now send the unmanufactured wool remarkable for its beauty. The stuffs manufactured are of incomparable texture. There is a superabundance of cattle and a great variety of game, while on the other hand there are certain little hares which burrow in the ground (rabbits). These creatures destroy both seeds and trees by gnawing their roots. They are met with throughout almost the whole of Spain. It is said that formerly the inhabitants of Majorca and Minorca sent a deputation to the Romans requesting that a new land might be given them, as they were quite driven out of their country by these animals, being no longer able to stand against their vast multitudes." The seacoast on the Atlantic side abounds in fish, says Strabo. "The congers are quite monstrous, far surpassing in size those of Our Sea. Shoals of rich fat tunny fish are driven hither from the sea coast beyond. They feed on the fruit, of stunted oak, which grows at the bottom of the sea and produces very large acorns. So great is the quantity of fruit, that at the season when they are ripe the whole coast on either side of the Pillars is covered with acorns thrown up by the tides. The tunny fish become gradually thinner, owing to the failure of their food as they approach the Pillars from the outer sea.
He describes, too, the metals of this wondrous land - gold, silver, copper, and iron. It is astonishing to think that in the days of Strabo the silver mines employed forty thousand workmen, and produced the modern-day equivalence of approximately $1,800 a day !
But we cannot follow Strabo over the world in all his detail. He tells us of a people living north of the Tagus, who slept on the ground, fed on acorn-bread, and wore black cloaks by day and night. He does not think Britain is worth conquering - Ireland lies to the north, not west, of Britain; it is a barren land full of cannibals and wrapped in eternal snows - the Pyrenees nun parallel to the Rhine - the Danube rises near the Alps - even Italy herself runs east and west instead of north and south. His remarks on India are interesting.
"The reader," he says, "must receive the accounts of this country with indulgence. Few persons of our nation have seen it; the greater part of what they relate is from report. Very few of the merchants who now sail from Egypt by the Nile and the Arabian Gulf to India have proceeded as far as the Ganges."
He is determined not to be led astray by the fables of the great size of India. Some had told him it was a third of the whole habitable world, some that it took four months to walk through the plain only. "Ceylon is said to be an island lying out at sea seven days' sail from the most southerly parts of India. Its length is about eight hundred miles. It produces elephants."
Strabo died about the year A.D. 21, and a century passed before Pliny wrote An Account of Countries, Nations, Seas, Towns, Havens, Mountains, Rivers, Distances, and Peoples who now Exist or Formerly Existed.
Strange to say, he never refers in the most distant way to his famous predecessor Strabo. He has but little to add to the earth-knowledge of Strabo. But he gives us a fuller account of Great Britain, based on the fresh discovers of Roman generals. (this map only exists as reconstruction)
Brown, L., The Story of Maps, p. 56.
Bunbury, E., History of Ancient Geography, Plate III.
Dilke, O.A.W., Greek and Roman Maps, pp. 23, 26, 30-34, 37, 43-46, 52, 60-65, 134, 137,157.
Harley, J.B., The History of Cartography, Volume One, pp. 173-175.
Stevenson, E., Terrestrial Globes, p. 9.
Bunbury, E., History of Ancient Geography, Plate III.
Dilke, O.A.W., Greek and Roman Maps, pp. 23, 26, 30-34, 37, 43-46, 52, 60-65, 134, 137,157.
Harley, J.B., The History of Cartography, Volume One, pp. 173-175.
Stevenson, E., Terrestrial Globes, p. 9.
“Geographika – Antik Anadolu Coğrafyası” - STRABON
Coğrafya anlamına gelen Geographika, Strabon’un olgunluk dönemi eserlerindendir. Tam olarak hangi tarihte yazıldığı belli değildir. Bazı araştırmacılar eseri MÖ 7 yılına tarihlerken, kimleri Strabon’un bu çalışmayı MS 18-19 yıllarında yazdığı görüşünü savunmaktadırlar. Grekçe (Eski Yunanca) olarak yazılmış Geographika, bir bütün olarak 17 kitaptan oluşmaktadır. Antik Anadolu’yu anlattığı bölümler ise XII-XIII-XIV numaralı kitaplarda bulunmaktadır.
Strabon (MÖ 65 - MS 23) , o tarihlerde Amaseia olarak isimlendirilen Amasya’da doğmuştur. Bir seyyah olarak Roma İmparatorluğu’nun büyük bir bölümünü dolaşmıştır. Gezileri sırasında uzun süreli olarak imparatorluğun başkenti Roma’da ve o dönemin görkemli şehirlerinden olan İskenderiye’de yaşamıştır.
Strabon’un “Tarihî Hatıralar (Historika Hypomnemata)” isimli 43 ciltlik bir kitabı daha olduğu bilinmektedir. Ama bu eser kayıptır. Korinthos ile ünlü Kartaca’nın yıkılmasından Sezar’ın ölümü ve Aksium Savaşı’na kadar olan tarihsel dönemi anlattığı bu kitabın (19 parçası dışında) tamamının günümüze erişmesi mümkün olmamıştır. Bu eser, MÖ 2’nci yüzyılda yaşamış olan Eski Yunanlı tarihçi Polybios’un o dönemi anlatan tarih kitabının devamı kabul edilir.
Strabon’un Geographika veya kimi zaman Geographumena olarak isimlendirilen eseri, ağırlıklı olarak Eski Yunan ve Roma kültürlerinin tanınması açısından önemlidir. Kitabın kaleme alınmasındaki hedef kitle, o dönem toplumun yüksek kültürlü kişileridir. Geographika üzerinde ayrıntılı çalışma yapan araştırmacılar, eserin yazarın kendisinden önceki Eratosthenes, Hipparkhos, Ephoros, Polybios ve Poseidonios gibi tarihçi ve düşünürlerden esintiler içerdiğini ifade etmektedirler. Strabon’un bu eseri, özellikle 16’ncı yüzyıldan sonra tarih ve düşünce çevrelerinde yoğun ilgi görmeye başlamıştır. (alıntıdır)
DÜNYANIN EN BÜYÜK DENİZCİLERİNDEN PİRİ REİS