This Aristarchus of Samos, who lived about three centuries before Jesus Christ, was one of the principal defenders of the doctrine of the earth’s motion. Archimedes informs us, “That Aristarchus, writing on this subject against some of the philosophers of his own age, placed the sun immovable in the centre of an orbit, described by the earth in its circuit.” Sextus Empiricus cites him, as one of the principal supporters of this opinion.
From a passage in Plutarch it appears, that Cleanthes accused Aristarchus of impiety and irreligion, by troubling the repose of Vesta and the Larian gods; when, in giving an account of the phenomena of the planets in their courses, he taught that heaven, or the firmament of the fixed stars, was immovable, and that the earth moved in an oblique circle, revolving at the same time around its own axis.
Theophrastus, as quoted by Plutarch, says in his History of Astronomy, which has not reached our times, that Plato, when advanced in years, gave up the error he had been in, of making the sun turn round the earth; and lamented that he had not placed it in the centre, as it deserved, instead of the earth, which he had put there contrary to the order of nature. Nor is it at all strange that Plato should reassume an opinion which he had early imbibed in the schools of the two celebrated Pythagoreans, Archytas of Tarentum, and Timæus the Locrian, as we see in St. Jerome’s Christian apology against Rufinus. In Cicero we find, that Heraclides of Pontus, who was a Pythagorean, taught the same doctrine. It may be added, that Tycho Brache’s system was known to Vitruvius, as well as were the motions of Venus and Mercury about the sun.
That the earth is round, and inhabited on all sides, and of course that there are Antipodes, or those whose feet are directly opposite to ours, is one of the most ancient doctrines inculcated by philosophy. Diogenes Laertius, in one part of his history, says, that Plato was the first who called the inhabitants of the earth opposite to us “Antipodes.” He does not mean that Plato was the first who taught this opinion, but only the first who made use of the term “Antipodes;” for, in another place, he mentions Pythagoras as the first who taught of When Plutarch wrote, it was a point in. controversy; and Lucretius and Pliny, were oppose this notion, as well as St. Augustine, serve as witnesses that it must have prevailed in their time.
The proofs which the ancients brought of the sphericalness of the earth, were the same that the moderns use. Pliny on this subject observes, that the land which retires out of sight to persons on the deck of a ship, appears still in view to those who are upon the mast. He thence concludes, that the earth is round. Aristotle drew this consequence not only from the circular shadow of the earth on the disk of the moon in eclipse, but also from this, that, in travelling south, we discover other stars, and that those which we saw before, whether in the zenith or elsewhere, change their situation with respect to us.
On whatever arguments the ancients founded their theory, it is certain they clearly apprehended that the planets revolved upon their own axis. Heraclides of Pontus, and Ecphantus, two celebrated Pythagoreans, said, that the earth turned from west to east, just as a wheel does upon its axis or centre. According to Atticus, the platonist, Plato extended this observation from the earth to the sun and other planets. “To that general motion which makes the planets describe a circular course, he added another, resulting from their spherical shape, which made each of them move about its own centre, whilst they performed the general revolution of their course.” Plotinus also ascribes this sentiment to Plato; for speaking of him he says, that besides the grand circular course observed by all the stars in general, Plato thought “they each performed another about their own centre.”
The same notion is ascribed to Nicetas of Syracuse by Cicero, who quotes Theophrastus to warrant what he advances. This Nicetas is he whom Diogenes Laertius names Hycetas, whose opinion, he says, was, that “the celerity of the earth’s motion about its own axis, and otherwise, was the only cause and reason of the apparent revolutions of the heavenly bodies.”
How useful the invention of telescopes has been to the astronomical observations of the moderns is particularly evident from their discovery, that the planets revolve on their axis, a discovery founded on the periodical revolution of the spots observed on their disks; so that every planet performs two revolutions, by one of which it is carried with others about a common centre; and, by the other, moves upon its axis round its own. Yet all that the moderns have advanced in this respect, serves only to confirm to the ancients the glory of being the first discoverers, by the aid of reason alone. The moderns in this are to the ancients, as the French philosophers to sir Isaac Newton; all whose labours and travail, in visiting the poles and equator to determine the figure of the earth, served only to confirm what sir Isaac had thought of it, without so much as stirring from his closet.