Concerning the Face which Appears in the Orb Of the Moon (6)

Even while I was still speaking Pharnaces spoke: Here we are faced again with that stock manoeuvre of the Academy[*]: on each occasion that they engage in discourse with others they will not offer any accounting of their own assertions but must keep

their interlocutors on the defensive lest they become the prosecutors. Well, me you will not to-day entice into defending the Stoics against your charges until I have called you people to account for turning the universe upside down. Thereupon Lucius laughed and said: Oh, sir, just don’t bring suit against us for impiety as Cleanthes thought that the Greeks ought to lay an action for impiety against Aristarchus the Samian on the ground that he was disturbing the hearth of the universe because he sought to save (the) phenomena by assuming that the heaven is at rest while the earth is revolving along the ecliptic and at the same time is rotating about its own axis.[*] We[*] express no opinion of our own now; but those who suppose that the moon is earth, why do they, my dear sir, turn things upside down any more than you[*] do who station the earth here suspended in the air? Yet the earth is a great deal larger than the moon[*] according to the mathematicians who during the occurrences of eclipses and the transits of the moon through the shadow calculate her magnitude by the length of time that she is obscured.[*] For the shadow of the earth grows smaller the further it extends, because the body that casts the light is larger than the earth[*]; and that the upper part of the shadow itself is taper and narrow was recognized, as they say, even by Homer, who called night nimble because of the sharpness of the shadow.[*] Yet captured by this part in eclipses[*] the moon barely escapes from it in a space thrice her own magnitude. Consider then how many times as large as the moon the earth is, if the earth casts a shadow which at its narrowest is thrice as broad as the moon.[*] All the same, you fear for the moon lest it fall; whereas concerning the earth perhaps Aeschylus has persuaded you that Atlas

Stands, staying on his back the prop of earth And sky no tender burden to embrace.[*]

Or, while under the moon there stretches air unsubstantial and incapable of supporting a solid mass, the earth, as Pindar says, is encompassed by steel-shod pillars[*]; and therefore Pharnaces is himself without any fear that the earth may fall but is sorry for the Ethiopians or Taprobanians,[*] who are situated under the circuit of the moon, lest such a great weight fall upon them. Yet the moon is saved from falling by its very motion and the rapidity of its revolution, just as missiles placed in slings are kept from falling by being whirled around in a circle.[*] For each thing is governed by its natural motion unless it be diverted by something else. That is why the moon is not governed by its weight: the weight has its influence frustrated by the rotatory motion. Nay, there would be more reason perhaps to wonder if she were absolutely unmoved and stationary like the earth. As it is, while [the] moon has good cause for not moving in this direction, the influence of weight alone might reasonably move the earth, since it has no part in any other motion; and the earth is heavier than the moon not merely in proportion to its greater size but still more, inasmuch as the moon has, of course, become light through the action of heat and fire.[*] In short, your own statements seem to make the moon, if it is fire, stand in greater need of earth, that is of matter to serve it as a foundation, as something to which to adhere, as something to lend it coherence, and as something that can be ignited by it, for it is impossible to imagine fire being maintained without fuel,[*] but you people say that earth does abide without root or foundation. [*] Certainly it does, said Pharnaces, in occupying the proper and natural place that belongs to it, the middle, for this is the place about which all weights in their natural inclination press against one another and towards which they move and converge from every direction, whereas all the upper space, even if it receive something earthy which has been forcibly hurled up into it, straightway extrudes it into our region or rather lets it go where its proper inclination causes it naturally to descend. [*]