Concerning the Face which Appears in the Orb Of the Moon (19)

When all had applauded Lucius, I said: Congratulations upon having added to an elegant account an elegant proportion, for you must not be defrauded of what belongs to you, He smiled thereat and said: Well then proportion must be used a second time, in order that we may prove the moon to be like the earth not only because the effects of the same agent are the same on both but also because the effects of both on the same patient are the same. Now, grant me that nothing that happens to the sun is so like its setting as a solar eclipse. You will if you call to mind this conjunction recently which, beginning just after noonday, made many stars shine out from many parts of the sky[*] and tempered the air in the manner of twilight.[*] If you do not recall it, Theon here will cite us Mimnermus[*] and Cydias[*] and

Archilochus[*] and Stesichorus besides and Pindar,[*] who during eclipses bewail the brightest star bereft [*] and at midday night falling [*] and say that the beam of the sun [is sped] the path of shade [*]; and to crown all he will cite Homer, who says the faces of men are covered with night and gloom[*] and the sun has perished out of heaven[*] speaking with reference to the moon and [hinting that] this naturally occurs

When waning month to waxing month gives say.[*]

For the rest, I think that it has been reduced by the precision of mathematics to the [clear] and certain [formula] that night is the shadow of earth[*] and the eclipse of the sun is the shadow of the moon[*] whenever the visual ray encounters it. The fact is that in setting the sun is screened from our vision by the earth and in eclipse by the moon; both are cases of occultation, but the vespertine is occultation by the earth and the ecliptic by the moon with her shadow intercepting the visual ray.[*] What follows from this is easy to perceive. If the effect is similar, the agents are similar, for it must be the same agents that cause the same things to happen to the same subject. Nor should we marvel if the darkness of eclipses is not so deep or so oppressive of the air as night is. The reason is that the body which produces night and that which produces the eclipse while the same in substance are not equal in size. In fact the Egyptians, I think, say that the moon is one seventy-second part (of the earth),[*] and Anaxagoras that it is the size of the Peloponnesus[*]; and Aristarchus demonstrates that the ratio of [the earth’s diameter to] the diameter of the moon is smaller than 60 to 19 and greater than 108 to 43.[*] Consequently the earth because of its size removes the sun from sight entirely, for the obstruction is large and its duration is that of the night. Even if the moon, however, does sometimes cover the sun entirely, the eclipse does not have duration or extension; but a kind of light is visible about the rim which keeps the shadow from being profound and absolute.[*] The ancient Aristotle gives this as a reason besides some others why the moon is observed in eclipse more frequently than the sun, saying that the sun is eclipsed by interposition of the moon but the moon [by that of the earth, which is much larger].[*] Posidonius gave this definition: The following condition is an eclipse of the sun, conjunction of the moon’s shadow with whatever [parts of the earth it may obscure], for there is an eclipse only for those whose visual ray the shadow of the moon intercepts and screens from the sun[*]; — since he concedes then that a shadow of the moon falls upon us, he has left himself nothing to say that I can see. Of a star there can be no shadow, for shadow means the unlighted and light does not produce shadow but naturally destroys it.[*]