But what brings these speculations to the subject we have now in hand is this: that when Aristotle thus proves the earth to be immovable in the centre of the universe, he is led on to inquire how it is possible for it to remain in one fixed place. He observed that even a small fragment of earth, when it is raised into the air and then let go, immediately falls without ever stopping in one place—falling, as he supposed, all the quicker according to its weight; and he was therefore puzzled to know why the whole mass of the earth, notwithstanding its weight, could be kept from falling.
Aristotle examines one by one the answers that have been given to this question. Thus Xenophanes gave to the earth infinitely extended roots, against which Empedocles uses such arguments as we should use now. Thales of Miletus makes the earth rest upon water, without finding anything on which the water itself can rest, or answering the question how it is that the heavier earth can be supported on the lighter water. Anaxemenes, Anaxagoras, and Democritus, who make the earth flat, consider it to be sustained by the air, which is accumulated below it, and also presses down upon it like a great coverlet. Aristotle himself says that he agrees with those philosophers who think that the earth is brought to the centre by the primitive rotation of things, and that we may compare it, as Empedocles does, to the water in glasses which are made to turn rapidly, and which does not fall out or move, even though upside down. He also quotes with approval another opinion somewhat similar to this, namely, that of Anaximander, which states that the earth is in repose, on account of its own equilibrium. Placed in the centre and at an equal distance from its extremities, there is no reason why it should move in one direction rather than the other, and rests immovable in the centre without being able to leave it.
The result of all is that Aristotle concludes that the earth is immovable, in the centre of the universe, and that it is not a star circulating in space like other stars, and that it does not rotate upon its axis; and he completes the system by stating that the earth is spherical, which is proved by the different aspects of the heavens to a voyager to the north or to the south.
Such was the Aristotelian system, containing far more error than truth, which was the first of any completeness. Scattered ideas, however, on the shape and method of support of the earth and the cause of various phenomena, such as the circulation of the stars, are met with besides in abundance.
The original ideas of the earth were naturally tinged by the prepossessions of each race, every one thinking his own country to be situated in the centre. Thus among the Hindoos, who lived near the equator, and among the Scandinavians, inhabiting regions nearer the pole, the same meaning attaches to the words by which they express their own country, medpiama and medgard, both meaning the central habitation. Olympus among the Greeks was made the centre of the earth, and afterwards the temple of Delphi. For the Egyptians the central point was Thebes; for the Assyrians it was Babylon; for the Indians it was the mountain Mero; for the Hebrews Jerusalem. The Chinese always called their country the central empire. It was then the custom to denote the world by a large disc, surrounded on all sides by a marvellous and inaccessible ocean. At the extremities of the earth were placed imaginary regions and fortunate isles, inhabited by giants or pigmies. The vault of the sky was supposed to be supported by enormous mountains and mysterious columns.
Numerous variations have been suggested on the earliest supposed form of the earth, which was, as we have seen in a former chapter, originally supposed to be an immense flat of infinite depth, and giving support to the heavens.
As travels extended and geography began to be a science, it was remarked that an immense area of water circumscribed the solid earth by irregular boundaries—whence the idea of a universal ocean.
When, however, it was perceived that the horizon at sea was always circular, it was supposed that the ocean was bounded, and the whole earth came to be represented as contained in a circle, beneath which were roots reaching downwards without end, but with no imagined support.
Fig. 25.—The Earth Floating.