Concerning the Face which Appears in the Orb Of the Moon (22)

Here Apollonides broke in. Then by the moon herself, he said, do you people think it possible that any clefts and chasms cast shadows which from the moon reach our sight here; or do you not reckon the consequence, and shall I tell you what it is? Please listen then, though it is not anything unknown to you. The diameter of the moon measures twelve digits in apparent size at her mean distance[*]; and each of the black and shadowy spots appears greater than half a digit and consequently would be greater than one twenty-fourth of her diameter. Well then, if we should suppose that the circumference of the moon is only thirty thousand stades and her diameter ten thousand each of the shadowy spots on her would in accordance with the

assumption measure not less than five hundred stades.[*] Consider now in the first place whether it is possible for the moon to have depths and corrugations so great as to cast such a large shadow; in the second place why, if they are of such great magnitude, we do not see them. Then I said to him with a smile: Congratulations for having discovered such a demonstration. Apollonides. It would enable you to prove that both you and I are taller than the famous sons of Aloeus,[*] not at every time of day to be sure but early in the morning particularly and in late afternoon, if, when the sun makes our shadows enormous. you intend to supply sensation with this lovely reasoning that, if the shadow cast is large, what casts the shadow is immense. I am well aware that neither of us has been in Lemnos; we have both, however, often heard this line that is on everyone’s lips:

Athos will veil the Lemnian heifer’s flank.[*]

The point of this apparently is that the shadow of the mountain, extending not less than seven hundred stades over the sea,[*] falls upon a little bronze heifer; [but it is not necessary, I presume,] that what casts the shadow be [seven hundred stades] high, for the reason that shadows are made many times the size of the objects that cast them by the remoteness of the light from the objects.[*] Come then, observe that, when the moon is at the full and because of the shadows depth exhibits most articulately the appearance of the face, the sun is at his maximum distance from her. The reason is that the remoteness of the light alone and not the magnitude of the irregularities on the surface of the moon has made the shadow large. Besides, even in the case of mountains the dazzling beams of the sun prevent their crags from being discerned in broad daylight, although their depths and hollows and shadowy parts are visible from afar. So it is not at all strange that in the case of the moon too it is not possible to discern accurately the reflection and illumination, whereas the juxtapositions of the shadowy and brilliant parts by reason of the contrast do not escape our sight.