Thinker in Geographical Thought Eratosthenes – Father of Geography

According to NEP 2020, the syllabus has been changed at the university level. New content has been added. Several changes are also noticeable in the subject of geography. The syllabus of the subject of development of geographical thought has also been updated, it has got a touch of modernity. According to the syllabus, the books required for the development of geographical thought are almost insufficient. In an attempt to overcome this predicament, our smallest attempt to develop geographical thought is the post named Eratosthenes – Father of Geography.

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Eratosthenes – Father of Geography 

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Eratosthenes (276-196 BC): After Aristotle, Alexander, Pythias and Theophrastus, Greek geography or the current geography, through whose works, initially began to take on a regular and systematic character based on fixed scientific principles, was Eratosthenes, and the school of geography that began to take on this character was: the Alexandrian School. Eratosthenes was born in 276 BC in the ancient Greek colony of Cyrene, Libya (now the city of Shahat in the Jabal al-Akhdar district of northeastern Libya). That is, he was about 108 years younger than Aristotle, about 80 years younger than Alexander, 104 years younger than Pythias and 41 years younger than Theophrastus. Eratosthenes was born 10 years after the death of Theophrastus. Information about Eratosthenes’s biography is limited, but what is known about him suggests that he was born into a poor family and that his father’s name was Aglaos. Around 260 BC, at the age of 16, he came to Athens, Greece, to study, where he studied under Ariston of Chios, Arkesilaos of Pitane, and Bion of Borysthenes for about 20 years. Around 240 BC, at the age of 36, he came to Alexandria at the invitation of Ptolemy III, the ruler of Egypt, and was appointed tutor to Ptolemy’s son Philopator; He immediately succeeded Zenodotus as the third chief librarian of the Great Library of Alexandria. He served as the chief librarian of the Library of Alexandria for about 44 years until his death in 196 BC. Incidentally, he died of starvation at the end of his life, fearing that he would go blind if he lost his eyesight. Eratosthenes was a librarian, mathematician, astronomer, geographer and a multi-talented person. He was a contemporary and friend of Archimedes. He was called “Beta” as a second-class scientist; where “Alpha” was replaced by Archimedes himself. After being appointed to the Library of Alexandria, he found that while there were many books on medicine and philosophy, there were none that described the Earth. To remedy this deficiency, he began writing a book called “Geographika” and was the first person to introduce the word “Geography“. He created a terminology consistent with his ideas by using the new words “Geography” (γεωγραφία) and “Geographer” (γεωγράφος). These words are based on the verb “Geographeo” (γεωγραφέω), “to write [about] the earth.” Eratosthenes’ book was entitled “Γεωγραφικά” (Geographica), and the word “Geography” is probably “γεωμετρέω” (Geōmetréō); (where Gaía = earth/land and μετρέω (metréō) – to measure) or was coined in analogy to words like “to measure [or survey] the land”.

Eratosthenes – Father of Geography

Eratosthenes and Greek Geography: Eratosthenes was a bridge figure between the philosophical and scientific geographical thought eras, who collected the information available from the Greek geographers before him, recorded it and left it as a form for the geographers who came after him. All the information that the philosophical geographers before him had kept was not really organized in a geographical sense, Eratosthenes initiated the task of organizing this. Let us see how his works influenced the development of geographical thought.

Eratosthenes – Father of Geography

i. The beginning of a geographical geography: Eratosthenes, through his works, brought together the scattered information in the development of geographical thought and introduced geographical geography in his book “Geographika“. Although most of Eratosthenes’ writings are now lost, fortunately, his extensive works were recorded by his successors, such as Strabo, Pliny, and Ptolemy. Strabo mentions three books of “Geography of Eratosthenes” in his entire works and quotes 105 fragments. On the other hand, 16 fragments are quoted from Pliny’s works. Thus, 155 quotations of Eratosthenes are currently available through the works of various ancient authors. Based on all these works, Seidel (Günther Carl Fridrich Seidel) modernly revealed the geographical works of Eratosthenes in his book “Eratosthenis Geographicorvm Fragmenta” published in 1789. Almost a century later, Ernst Hugo Berger attempted to restore Eratosthenes’ works in his 1880 book Die Geographischen Fragmente des Eratosthenes. Although both editions are significant, Berger’s efforts have contributed to the reconstruction of fragments, ancient geography, and the Hellenistic world. The most recent attempt to restore Eratosthenes’ works is Duane W. Roller’s 2010 book Eratosthenes’ Geography: Fragments collected and translated, with commentary and additional material. In this book, Roller discusses the contents of the three books of the Geography of Eratosthenes in detail. According to Roller, the first book was “a survey of the history of geography from the time of Homer”; The second book was entitled “Eratosthenes’ Theory of the Shape of the Earth and the Inhabited World” and the third book was entitled “Discussion on the Landforms of the Inhabited World”. In other words, Eratosthenes, through his works, explored the historical context of geography and recorded the scientific and geophysical data of the then known world, literally initiating geographical geography. For these works, he is called the “Father of Geography“.

ii. Calculating the Earth’s Circumference: Eratosthenes heard about a famous well in the city of Sine (now Aswan) in Egypt, located on the banks of the Nile River, where the sun is directly overhead at noon on the summer solstice between June 20 and 22 every year, so that the sun’s rays illuminate the bottom of the deep well without casting a shadow, and the vertical pillars do not cast any shadow. Out of curiosity, he set up a pole in Alexandria to verify the truth of the matter and on the summer solstice he noticed that the pole was casting a shadow to its north. From this he concluded that on the summer solstice the sun was not directly overhead in Alexandria but slightly to the south. He realized that if the earth were flat, the shadow would be the same in both cities. This difference in shadow supported the curvature of the earth. He measured the angle of the shadow cast by the pole in Alexandria and found it to be 7.2 degrees. He divided this value by the circumference of the circle (360 degrees) to get the result of 50 degrees. From this he concluded that the distance between Alexandria and Syene was exactly 1/50 of the total circumference of the earth. Now it became easy for him to determine the circumference of the earth from the land distance between Alexandria and Syene. He obtained the distance between Syene and Alexandria from the information of professional “Bemastists” as 5,000 stadia (about 800 km). That is, the circumference of the Earth is: 50X5,000 stadia = 25,000 stadia or 50X800 km = 40,000 km. That is, he first determined the circumference of the Earth as 40,000 km, which is only 8 km less than the current determined polar circumference of the Earth (40,008 km) and only 75 km less than the equatorial circumference (40,075 km). That is, Eratosthenes was able to determine the approximate circumference of the Earth about 2250 years ago, in 230 BC. In this way, he laid the foundation stone of the present “Geodesy”.

Eratosthenes – Father of Geography

iii. Coordinate System & Map Drawing: Eratosthenes was the first person to introduce a grid system of parallels (latitudes) and meridians (longitudes) in cartography to specify the location of the Earth’s surface. He used mathematical methods to create a map of the Oecumene (inhabited world) based on remarkably accurate calculations of the Earth’s circumference and axial angles. However, Eratosthenes chose the most accurate known map of the Oecumene (inhabited area) made by Aristotle’s student Dicaearchus® (Dicaearchus of Messina: 345-285 B.C.) for the essential improvement of his map. Dicaearchus, in turn, based his map on the locations described by Pythias. Dicaearchus was the first person to use the Mean Parallel and the Mean Meridian in his map, drawing his map across the Rhode Island in the Mediterranean Sea. Eratosthenes and earlier geographers drew a straight line across the Strait of Gibraltar, the Strait of Messina, Rhode Island, and the Taurus Mountains to the very end of the eastern Oecumen, called the Diaphragm (“Kartografija”: Chomskis, V.; 1979). Considering Rhode Island as the intersection of the mean parallel and the mean meridian, Eratosthenes drew 10 parallels and 11 meridians on his map, according to measurements on local features. In this way, he invented a geographical grid map. The map he developed later served as the basis for the use of the Cylindrical Cartographical Projection. He also gave his own names to both the parallels and meridians, according to the names of local features. He also indicated the value of the line in stadia (1 stadia = about 0.152 km) next to the grid. His map extends from the equator to the western meridian of the Ethiopian Ocean. A notice in the southwest corner of the map states that each degree from the equator is 700 stadia.
Eratosthenes’ map, made in 220 BC, depicts the center of civilization (the Mediterranean) of that time, including the geographical knowledge of the settled regions of the world. The map includes parts of Europe and Asia, the Indian Ocean, the Bay of Bengal (Mer Orientale) and Sri Lanka (Taprobene); to the south, the Ethiopian Ocean (Ocean Ethiopien) and North and Central Africa, including Libya, Ethiopia and Nubia, are included, and the map is limited to the Arabian Sea (Mer Erythri). The map covers a 12,000×6000 km rectangle, according to the values ​​of the marginal parallels and meridians. Researchers of Eratosthenes’ map claim that he marked several places based on astronomical measurements. It is possible to give each of Eratosthenes’ names a modern geographical name, with the exception of the value of the meridian of Thule.

Eratosthenes – Father of Geography

iv. Five Climate Zones: Eratosthenes divided the Earth into five distinct climate zones based on latitude: a central warm (equatorial) zone, two temperate zones, and two cold (polar) zones. This basic model, described in his Geographica, helped organize the known world using a system of parallels and meridians. Although the Geographica is lost, fragmentary quotations from it indicate that he used this system to map over 400 cities. This idea has survived for centuries as the primary way to classify global climates.
Eratosthenes was the first to combine mathematical, physical, and descriptive geography, moving away from purely speculative descriptions and toward a scientific approach. Eratosthenes was the first to impressively determine the tilt of the Earth’s axis with near-perfect accuracy. He also calculated the distances of the Moon and Sun from the Earth with low accuracy. He listed 675 stars. He also created a calendar of leap years. He established a chronology based on when historical events occurred. He also organized the dates of events from the siege of Troy (c. 1194–1184 BC) to his own time. “We also learn from Strabo that, in order to prove that the earth was not perfectly round, Eratosthenes entered into a long calculation of the changes in its surface caused by the action of water, fire, earthquakes, volcanic eruptions, and other similar causes”.

Eratosthenes – Father of Geography Eratosthenes – Father of Geography

Eratosthenes – Father of Geography