The conceptions of the ancients respecting the fixed stars were not less clear than ours. Indeed, the opinions of the moderns on this subject have been adopted within a century from those great masters, after having been rejected during many ages. It would be reckoned almost an absurdity at present, to doubt of those stars being suns like ours, each respectively having planets of their own, revolving around them, and forming various solar systems, more or less resembling ours. Philosophy, at present, admits this theory, derived from the ancients, and founded on the most solid reasonings of astronomical science. The elegant work of Fontenelle, on the “Plurality of Worlds,” first rendered the conception familiar to common minds.
This notion of a plurality of worlds was generally inculcated by the Greek philosophers. Plutarch, after giving an account of it, says, that “he was so far from finding fault with it, that he thought it highly probable there had been, and were, like this of ours, an innumerable, though not absolutely infinite, multitude of worlds; wherein, as well as here, were land and water, invested by sky.”
Anaximenes was one of the first who taught, that “the stars were immense masses of fire, around which certain terrestrial globes, imperceptible to us, accomplished their periodic revolutions.” By these terrestrial globes, turning round those masses of fire, he evidently meant planets, such as ours, subordinate to their own sun, and forming a solar system.
Anaximenes agreed with Thales in this opinion, which passed from the Ionic to the Italic sect; who held, that every star was a world, containing in itself a sun and planets, all fixed in that immense space, which they called ether.
Heraclides, and all the Pythagoreans likewise taught, that “every star was a world, or solary system, having, like this of ours, its sun and planets, invested with an atmosphere of air, and moving in the fluid ether, by which they were sustained.” This opinion seems to have been of still more ancient origin. There are traces of it in the verses of Orpheus, who lived in the time of the Trojan war, and taught that there was a plurality of worlds; a doctrine which Epicurus also deemed very probable.
Origen treats amply of the opinion of Democritus, saying, that “he taught, that there was an innumerable multitude of worlds, of unequal size, and differing in the number of their planets; that some of them were as large as ours, and placed at unequal distances; that some were inhabited by animals, which he could not take upon him to describe; and that some had neither animals, nor plants, nor any thing like what appeared among us.” The philosophic genius of the illustrious ancient discerned, that the different nature of those spheres necessarily required inhabitants of different kinds.
This opinion of Democritus surprised Alexander into a sudden declaration of his unbounded ambition. Ælian reports, that this young prince, upon hearing Democritus’s doctrine of a plurality of worlds, burst into tears, upon reflecting that he had not yet so much as conquered one of them.
It appears, that Aristotle also held this opinion, as did likewise Alcinoüs, the Platonist. It is also ascribed to Plotinus; who held besides, that the earth, compared to the rest of the universe, was one of the meanest globes in it.
Satellites.—Vortices.
In consequence of the ancient doctrine of the plurality of worlds, Phavorinus remarkably conjectured the possibility of the existence of other planets, besides those known to us. “He was astonished how it came to be admitted as certain, that there were no other wandering stars, or planets, but those observed by the Chaldeans. As for his part, he thought that their number was more considerable than was vulgarly given out, though they had hitherto escaped our notice.” Here he probably alludes to the satellites, which have since been manifested by means of the telescope; but it required singular penetration to be capable of forming the supposition, and of having, as it were, predicted this discovery. Seneca mentions a similar notion of Democritus; who supposed, that there were many more of them, than had yet come within our view.