Contribution of Greeks to Mathematical and Physical Geography!
The Greeks not only extended the horizon of geography from the Aegean Sea to Spain and Gaul, the Russian steppes in Central Asia, the Indus river in the east and Ethiopia in the south, but also put the subject on a sound footing by making remarkable contributions in the field of mathematical, physical, historical and regional geography.
Mathematical geography developed by Thales (C-580 B.C.), Anaximender (611 B.C.) and Aristotle (384-322 B.C.) reached its zenith with Eratosthenes (276-194 B.C.).
The sphericity of the earth was proved, its size computed accurately. The latitudes and longitudes of many places were calculated and the practice of plotting world maps on a grid was initiated. The physical geography progressed less rapidly. Various scholars speculated about the phenomena of weather, tides and volcanism. Causes of Nile’s floods and the formation of deltas were studied.
How streams slowly carved their valleys was examined and understood. Posidonius (135-150 B.C.) investigated the cause of tides at Gades, measured the depth of sea at Sardinia. The Greeks also attempted to write historical and biographical account of the known world. In the following paragraphs, their major contributions in the various branches of geography have been briefly described.
During the Golden Age of Greece—5th century B.C. to 2nd century B.C.—there was a bunch of scholars who were engaged in determining the shape, size, and climatic zones of the earth, and to ascertain the Ocean River, encompassing the habitable world. Moreover, philosophers like Plato and Aristotle encouraged their pupils to make efforts to determine the distances and latitudes with the help of astronomical observations. Heracleides Ponticus, the renowned associate of Plato, established the rotation of the earth on its axis, though still regarding it as the centre of the universe.Anaximender introduced the Babylonian gnomon to the Greek world.
He measured the latitudes of important places and prepared the first map of the world to scale. Thales and Anaximender are considered as the founders of mathematical geography. Thales and Aristotle established the spherical shape of the earth. Aristotle, by philosophical reasoning and astronomical observations, arrived at a conclusion that the earth was a sphere. His speculations about the shape of the earth were seconded by Eratosthenes based on a limited, measured arc of longitudes.
The astronomer Hipparchus of Rhodes (2nd century B.C.) developed a location system of lines on the surface of the earth—the forerunner of latitudes and longitudes. The spherical shape of the earth was a generally conceived idea among the Greeks. Hecataeus and Herodotus were, however, not the followers of the idea of the sphericity of the earth. Eudoxus of Cnidus—a contemporary of Plato—developed the theory of zones of climate based on increasing shape away from the sun on a spherical surface. All these formulations were deductions from pure theory that all observable things were created in perfect form and that the most perfect form was a sphere.
Aristotle was the first philosopher who wrote with definite arguments about the spherical shape of the earth. He gave two arguments in support of his statement about the sphericity of the earth. First, he deduced it from the law of gravitation, or, as he expressed it, the tendency of all things towards the centre. Through the operation of this principle, when the earth was in the course of formation, and the component elements were coming together equally from every quarter, the mass thus formed by acceleration was so constituted that its entire circumference must be equidistant from its centre.
Secondly, he infers it from what is seen to take place in lunar eclipses; for, when the earth is interposed between the sun and the moon, the special form of the obscured part of moon’s surface shows that the body which causes the obstruction is also spherical. Archimedes (250 B.C.) deduced from the interference that the surface of the sea must be convex—a conclusion which would naturally involve the gradual revelation of objects approaching upon it.
Archytas measured the total length of the land and sea. Aristotle agreed with the calculations of his predecessors stating that the circumference of the earth is 40, 00,000 stadia (40,000 miles). Eratosthenes who made observations at Syene (Aswan) and Alexandria calculated the circumference of the earth as 250,000 stadia (25,000 miles). Looking at the indigenous gnomon he used, it can be said that he was very near to the truth.
Herodotus attempted to determine the meridian of longitude. He drew a meridian from Meroe, Syene (Aswan), Alexandria, Troad, Byzantium and the mouth of Borysthenes (Fig. 1.6). Hipparchus pointed out that the true method of determining longitudes was by the comparative observation of eclipse. However, we have no evidence to show that any investigations were made. The Greek scholars, especially Herodotus, Anaximender, Hipparchus and Eratosthenes drew the parallels of latitudes also. The first parallel drawn by Eratosthenes passed from the Pillars of Hercules to the extremity of India.
Other parallels of latitudes were drawn through the Cinnamon region (Ethiopia), Meroe, Syene (Aswan), Alexandria, Rhodes, Troad, the mouth of Borysthenes, Pytheas and Thule. Similarly, the meridians of longitudes, drawn by Eratosthenes, passed through the Pillars of Hercules, Carthage, Alexandria, Thapsacus (on the Euphrates), the Caspian Gates, the mouth of the Indus and the mouth of the Ganges.
So far as the shape of the earth is concerned, the Ionians (Thales, Anaximender and Hecataeus) considered the earth as a circular plane, surrounded on all sides by Ocean River. The Ionians divided the habitable world into two continents, namely, Europe and Asia including Libya (Africa). Herodotus, however, did not agree with this idea of the Ionian School. He conceived the earth as a plane and was of the view that there is symmetrical arrangement of land and water and inhabited parts on the earth’s surface.
He compared not only the lands to the north and south of the Mediterranean Sea but also the rivers (Nile and Ister), their directions and deltas. Eratosthenes treated the inhabited world as an island, and made it in shape of irregular oblong, the extremities of which tapered off to a point both east and west. These end points of the oblong he fixed at the extremity of India and the Sacrum Promotorium in Spain. He divided the world by the Mediterranean Sea and the Tarus Mountains. To the north of these he called the land as Europe and to the south of it as Asia and Libya (Africa). The subsequent Roman scholars like Strabo also followed the same theory of the shape of the earth.
One of the major contributions of the Greek scholars was in the realm of theory building and hypothesis testing. Plato mostly built theories by intuition and reasoned from the general to the particular which is called the deductive approach. Contrary to this, his disciple Aristotle built theory by reasoning from the particular to the general. This is known as the inductive approach. Aristotle recognized that observations made through the senses can never provide explanations. Our senses, he said, can tell us that fire is hot but cannot tell us why it is hot.
Aristotle was also the first teleologist as he believed everything was changing in accordance with the pre-existing pattern or plan, just as a mason/carpenter building a house knows in advance what the house will be like when it is finished. Aristotle reasoned that the parts of the earth close to the equator (the Torrid Zone) were not suitable for human habitation. He also opined that, all things are not deteriorating from an ideal state, but are rather developing towards an ideal state.
The Greeks also made remarkable development in the field of physical geography. Greece was in many ways a suggestive country having diverse topographic and physical features. As has already been stated at the outset, Greece was a land of mountains, many of which were of great height to be snow-clad in winters. The rivers for the most parts were torrents which flowed with a rushing current in winter, and were dry in summer. There were perennial streams also like Acheolous and Alpheius. The capes which projected into the Aegean Sea and the straits which penetrated into the mainland inspired the Greek sailors to make observations and to explore the neighbouring islands.
There were some peculiar features also like subterranean streams in limestone areas, volcanoes and occurrence of earthquakes which provided incentives to the Greeks to find the causes of their occurrence. The effect of these features on the mind of Aristotle is especially traceable. The destruction of the cities of Helice and Bura on the coast of Achaia by an earthquake took place during the early life of Aristotle. This event seems to have greatly touched his imagination, for he refers to it more than once in his Meterologica.
The works of the Greeks contain numerous references to mountains, delta-building, winds, change of weather, rain, earthquakes and their causes, volcanoes and transformation in the topographic features. Aristotle explained the phenomena of expansion of land in the shallow seas and the formation of delta.
He correctly pointed out the process of alluvial deposition through which in so many places the land was gaining on the sea, especially in the Palus-Maeotis (Sea of Azov), which he affirmed, was continually becoming shallower, and would be one day entirely filled up and converted into dry land. The delta formation of the Nile was also attributed to the enormous silt carried by the river from its upper reaches (Ethiopia).
The Greeks were of the opinion that all the perennial rivers had their sources in great mountain ranges. Agatharchides has described the occurrence of gold ore in the Ethiopian gold mines visited by him and has narrated the process of its extraction from the veins of rock strata. Plato has discussed some of the barren lands of Attica (Greece) and has explained that such waste tracts in the past were full of vegetative covers and fertile soils.
Under the impact of the external forces, the forests had been depleted and soils leached resulting into barren topography. Such wastelands, he said, were like the skeleton of a sickman, all the fat and soft earth having been wasted away, and only the bare framework of the land being left. Plato considered man an active agent who changed the face of the earth.
From the Aegean Sea, the Greeks expanded the horizon of knowledge in the study of seas and oceans and distinguished the varying properties of their coastlines, salinity, waves, tides and winds. Posidonius wrote a book—The Ocean. On oceanography he was considered an authority.
Herodotus observed the phenomenon of tides in the Red Sea and the Matiac Gulf. Aristotle observed the tidal movements in his book—Meteorologica. But the cause of tidal waves he attributed to the winds. Later on, Nearchus observed the tides in the Arabian Sea and Pytheas in the Atlantic Ocean. Pytheas, who was a scientist, made careful observations on the regular recurrence of tides, with the aim of determining the causes which produced them.
He established the correspondence between their diurnal recurrence and movement of the moon.It was Posidonius who pointed out that at the new moon when the sun and the moon were in conjunction, and also at the full moon, the tides were the highest (spring tides), whereas at the first and last quarters they were the lowest (neap tides).
The Greeks, right from the Homeric period, recognized four major winds, having different properties and directions. These winds were called bores (north wind), eurus (east wind), notus (south wind), zephyrus (west wind). In the second century B.C., the Athenians built a tower identifying eight wind directions with sculpture illustrating the weather types associated with each. The tower still stands in the midst of a Roman market at the base of the Acropolis.
The Greeks divided the world into torrid, temperate and frigid zones. They were familiar with the excessively high temperatures to be experienced in Libya along the southern side of Mediterranean. The Greeks believed that the Libyans are black because they had burned black by exposure to the sun and deduced that further southward (near equator) life must be impossible.
Aristotle reasoned that the parts of the earth close to the equator (the torrid zone) were uninhabitable. The parts away from the equator being very cold and frigid were also uninhabitable. The Greeks established a relationship between temperatures and ecumenic regions of the world.
The mountains of Greece belong to the Alpine tectonic activity. These are the young folded mountains in which occurrence of earthquakes is a frequent phenomenon. Earthquakes attracted the attention of Greek thinkers. Herodotus expressed his opinion with regard to the disruption of Olympus and Ossa.
Anaximender described earthquakes as fractures of crust of the earth, which were produced by its passing through a process of drying, after having previously been saturated with moisture. According to Aristotle, earthquakes and volcanoes were caused by winds (gases) which were confined beneath the surface of the earth, and were trying to find a vent. The Greeks made very careful observations about volcanoes and felt that they were vents in the earth-crust, by means of which the frequency and violence of the earthquake movements were lessened.
The Greek scholars also recognized differences in the fauna and flora of the different parts of the world. Some of the pupils of Aristotle, particularly Theopharastus, described the habitat of different trees and shrubs and established a correlation between climate and natural vegetation. As regards the fauna, the Greeks described a great number of strange animals of different nations and regions.