The Globular Form of the Earth.
THERE are parts of Plato’s writings which have been adduced as bearing upon the subsequent progress of science; and especially upon the globular form of the earth, and the other views which led to the discovery of America. In the Timæus we read of a great continent lying in the Ocean west of the Pillars of Hercules, which Plato calls Atlantis. He makes the personage in his Dialogue who speaks of this put it forward as an Egyptian tradition. M. H. Martin, who has discussed what has been written respecting the Atlantis of Plato, and has given therein a dissertation rich in erudition and of the most lively interest, conceives that Plato’s notions on this subject arose from his combining his conviction of the spherical form of the earth, with interpretations of Homer, and perhaps with traditions which were current in Egypt (Etudes sur le Timée, Note xiii. § ix.). He does not consider that the belief in Plato’s Atlantis had any share in the discoveries of Columbus.
It may perhaps surprise modern readers who have a difficulty in getting rid of the persuasion that there is a natural direction upwards and a natural direction downwards, to learn that both Plato and Aristotle, and of course other philosophers also, had completely overcome this difficulty. They were quite ready to allow and to conceive that down meant nothing but towards some centre, and up, the opposite direction. (Aristotle has, besides, an ingenious notion that while heavy bodies, as earth and water, tend to the centre, and light bodies, as fire, tend from the centre, the fifth element, of which the heavenly bodies are composed, tends to move round the centre.)
Plato explains this in the most decided manner in the Timæus (62, c). “It is quite erroneous to suppose that there are two opposite regions in the universe, one above and the other below; and that heavy things naturally tend to the latter place. The heavens are spherical, and every thing tends to the centre; and thus above and below have no real meaning. If there be a solid globe in the middle, [506] and if a person walk round it, he will become the antipodes to himself, and the direction which is up at one time will be down at another.”
The notion of antipodes, the inhabitants of the part of the globe of the earth opposite to ourselves, was very familiar. Thus in Cicero’s Academic Questions (ii. 39) one of the speakers says, “Etiam dicitis esse e regione nobis, e contraria parte terræ, qui adversis vestigiis stant contra nostra vestigia, quos Antipodas vocatis.” See also Tusc. Disp. i. 28 and v. 24.
The Heliocentric System among the Ancients.
As the more clear-sighted of the ancients had overcome the natural prejudice of believing that there is an absolute up and down, so had they also overcome the natural prejudice of believing that the earth is at rest. Cicero says (Acad. Quest. ii. 39), “Hicetas of Syracuse, as Theophrastus tells us, thinks that the heavens, the sun, the moon, the stars, do not move; and that nothing does move but the earth. The earth revolves about her axis with immense velocity; and thus the same effect is produced as if the earth were at rest and the heavens moved; and this, he says, Plato teaches in the Timæus, though somewhat obscurely.” Of course the assertion that the moon and planets do not move, was meant of the diurnal motion only. The passage referred to in the Timæus seems to be this (40, c)—“As to the Earth, which is our nurse, and which clings to the axis which stretches through the universe, God made her the producer and preserver of day and night.” The word εἱλλομένην, which I have translated clings to, some translate revolves; and an extensive controversy has prevailed, both in ancient and modern times (beginning with Aristotle), whether Plato did or did not believe in the rotation of the earth on her axis. (See M. Cousin’s Note on the Timæus, and M. Henri Martin’s Dissertation, Note xxxvii., in his Etudes sur le Timée.) The result of this discussion seems to be that, in the Timæus, the Earth is supposed to be at rest. It is however related by Plutarch (Platonic Questions, viii. 1), that Plato in his old age repented of having given to the Earth the place in the centre of the universe which did not belong to it.
In describing the Prelude to the Epoch of Copernicus (Book v. [Chap. i.]), I have spoken of Philolaus, one of the followers of Pythagoras, who lived at the time of Socrates, as having held the doctrine that the earth revolves about the sun. This has been a current [507] opinion;—so current, indeed, that the Abbé Bouillaud, or Bullialdus, as we more commonly call him, gave the title of Philolaus to the defence of Copernicus which he published in 1639; and Chiaramonti, an Aristotelian, published his answer under the title of Antiphilolaus. In 1645 Bullialdus published his Astronomia Philolaica, which was another exposition of the heliocentric doctrine.
Yet notwithstanding this general belief, it appears to be tolerably certain that Philolaus did not hold the doctrine of the earth’s motion round the sun. (M. H. Martin, Etudes sur le Timée, 1841, Note xxxvii. Sect. i.; and Bœckh, De vera Indole Astronomiæ Philolaicæ, 1810.) In the system of Philolaus, the earth revolved about the central fire; but this central fire was not the sun. The Sun, along with the moon and planets, revolved in circles external to the earth. The Earth had the Antichthon or Counter-Earth between it and the centre; and revolving round this centre in one day, the Antichthon, being always between it and the centre, was, during a portion of the revolution, interposed between the Earth and the Sun, and thus made night; while the Sun, by his proper motion, produced the changes of the year.