XIV.
Quoniam de sole quae uisa sunt nobis utilissima esse, litteris mandauimus, nunc de luna dicemus (etsi alia conati perscribere, uelut natura uoluminis ad hoc loci deuenimus), ne nonnullis intactam huius rationem relinquentes, aut propter magnum laborem defecisse, aut inscientia superati non ualuisse persequi uideamur. nos autem non illorum existimationis timendae causa persequi instituimus, sed consuetudinis nostrae rationem demonstrasse, et quod alterius quaeri uolumen hoc perlecto noluimus, nec tamdiu rem cogitatam scriptam aliorum ad desiderium adducere. praeterea cum reliqua omnia diligentissime persecuti fuerimus, alienum uidetur esse nos non eandem persequi causam. quare, sicut ante diximus, ad inceptum reuertamur et ut necessario totidem uerbis de luna ac sole dicere uideamur, dicemus ita:
XIV. The moon, its eclipses and the planetary spheres
Since we have committed to writing what seemed to us most useful concerning the sun, we shall now speak of the moon (although, in trying to write other things, as if by the nature of the volume we have come to this point), lest, leaving the account of it untouched for some, we seem either to have given out through great labour or, overcome by ignorance, to have been unable to follow it through. We, however, did not undertake to follow it for fear of their opinion, but to have shown the system of our usual practice, and because we did not wish another volume to be sought when this has been read through, nor so long to draw to desire what has been thought out and written by others [?]. Besides, since we have followed up all the rest most diligently, it seems unfitting that we should not follow the same course here. Therefore, as we said before, let us return to what was begun, and so that we may necessarily seem to say as many words on the moon as on the sun, we shall speak thus:
Lunam per alios exortus et occasus necesse est moueri, non stare; idque facilius quam de sole licet intellegere. neque enim tam magnus ardor eius est, ut officiat oculis nostris; neque ut sol dies XXX unoquoque signo uehitur, ut difficile sit intellectu, quanta particula luminis aut ipsius signi superesse uideatur, cum ad aliud transierit signum. lunam enim cum diebus XXX XII signa percurrat, licet intellegere, II diebus et VI horis in alio signo esse. hanc autem cum a sole lumen accipiat, et ita nobis lucere uideatur, non est ueri simile de tam multis causis potius eam stare quam moueri. si enim suo lumine uteretur, illud quoque sequebatur eam semper aequalem esse oportere, nec die tricesimo tam exilem aut omnino nullam uideri, cum totum transegerit cursum, sol autem ad aliud transire signum intellegatur. praeterea si suo lumine uteretur, huius numquam eclipsin fieri oportebat. sed ne dubium fiat, quare solis eclipsis fieri possit, qui utrisque lumen dare supra sit dictus, lunae autem non facile fiat, cum alieno lumine utatur: eius haec uerissima, ut arbitramur, est causa. luna enim cum ex toto mundo et omnibus stellis maxime terrae proxima uideatur, et ad acies nostras perueniat, et quodam tempore torrens perueniat ad eundem locum signi, quo sol uehitur, obscurare lumen eius a nostro conspectu uidetur. hoc autem maxime euenit die nouissimo, cum luna transierit in XII signa, et sol ad aliud signum transire uideatur et proxima fiat illi. quod euenire sic etiam potest intellegi. ut si quis alicui manum planam ad oculos admouerit, quanto magis sic fecerit, hoc minus ille uidere poterit; et quanto longius ab eo discesserit, hoc magis illi omnia poterunt apparere. simili ratione cum luna ad solis locum peruenit, tunc proxima eius uidetur esse et radios eius obturare, ut lumen eicere non possit. cum autem luna ab eo loco discesserit, tunc sol lumen eicit, et ita ad corpora nostra adicit.
The moon must move through other risings and settings, not stand still; and this can be understood more easily than for the sun. For its heat is not so great as to harm our eyes; nor is it carried 30 days in each sign, as the sun is, so that it is hard to understand how small a part of light, or of the sign itself, appears to remain when it has passed to another sign. For since the moon runs through the 12 signs in 30 days, one can understand that it is in each sign for 2 days and 6 hours. Since it receives its light from the sun, and so seems to shine for us, it is not likely, for so many reasons, that it stands rather than moves. For if it used its own light, it would also follow that it must always be equal, and not on the thirtieth day appear so thin or not at all, when it has completed the whole course, while the sun is understood to pass to another sign. Moreover, if it used its own light, an eclipse of it ought never to occur. But lest there be doubt why an eclipse of the sun can occur — which is said above to give light to both — while one of the moon does not easily occur, since it uses another's light: this is, as we think, the truest reason for it. The moon, since of the whole world and all the stars it seems nearest to the earth, and reaches our sight, and at a certain time, hastening, arrives at the same place of the sign in which the sun is carried, seems to obscure its light from our view. This happens most on the last day, when the moon has passed through the 12 signs, and the sun is seen to pass to another sign and the moon becomes nearest to it. This can also be understood thus: as if someone holds a flat hand to another's eyes, the more he does so, the less the other will be able to see; and the farther he goes away from him, the more will everything be able to appear to him. In like manner, when the moon reaches the sun's place, it is then seen to be nearest to it and to block its rays, so that it cannot cast out light. When, however, the moon has gone away from that place, the sun then casts out its light, and so throws it upon our bodies.
Lunae autem eclipsis sic euenit, cum prope dimensione sit luna, cum abierit sol sub terram, dumtaxat hoc modo, ut per mediam terram si quid directum traieceris, contingere possit solem sub terra, lunam autem supra terram: quod cum ita euenit, necesse est solis radios propter magnitudinem terrae ita esse dimissos, ut lumen eius, quo luna lucet, non possit ad eam peruenire, et ita existimatur fieri eclipsis lunae. quae si suo lumine uteretur, licebat ne apparere quidem umquam solem, ideo quod luna nihilominus luceret. sic autem accipit lumen, ut luceat, cum sol uenerit per terras, sed non ut aliquem locum conclusiorem totumque spatium inpleat lumine. si quis nostrum steterit in eo loco, quo sol maxime lucet, reliquis partibus lumen a sole accipiens praebebit. id in luna fieri inuenitur, eam a sole lumine accepto lucere reuibratione.
The eclipse of the moon occurs thus: when the moon is near the diameter, when the sun has gone beneath the earth, in this way: that if you were to draw a straight line through the middle of the earth, it could touch the sun beneath the earth and the moon above the earth: when this happens, the rays of the sun must be so cut off by the size of the earth that its light, by which the moon shines, cannot reach it, and so an eclipse of the moon is held to occur. If the moon used its own light, it would be possible that the sun would never even be seen, because the moon would nonetheless shine. It receives light so as to shine when the sun has come through the lands, but not so as to fill some more enclosed place and the whole space with light. If one of us stands in the place where the sun shines most, he will give light to the remaining parts, receiving it from the sun. This is found to happen in the moon, that it shines with the light received from the sun by reflection.
Nonnulli existimant, cum dicitur sol in Ariete aut in quolibet signo esse, eum supra ipsas stellas Arietis iter facere. qui autem hac ratione utuntur, longe a uera ratione errant. nam neque sol, neque luna proxime sidera apparent. hac etiam de causa nonnulli VII stellas erraticas finxerunt, adiungentes eodem solem et lunam, quod cum quinque stellis feruntur. luna enim proxime terram est; itaque diebus XXX totum mundum existimatur transire. id hac euenit ratione. ut si quis intra circulum zodiacum fecerit circulos, et eos hoc interuallo finxerit, ut terra sit in medio, et unam a terra ad lunam mensionem fecerit, quam Graeci τόνον appellauerunt (hunc autem, quia non esse certum spatium potuerunt dicere, τόνον dixerunt): igitur abest luna a terra tonum unum. hac igitur re, quod breuissimo circulo deuehitur, diebus XXX ad primum peruenit signum. ab hoc circulo abest circulus tonum dimidium, quo circulo Mercurii stella uehitur; itaque diebus XXX ad alterum signum transiens tardius. ab hoc circulo abest alter tonum dimidium; quo loco Ueneris stella iter suum dirigit, tardiorem conficiens cursum, quam Mercurii stella. transit enim ad aliud signum diebus XXX. supra huius stellam solis est cursus, qui abest ab Hespero stella quae est Ueneris, tonum dimidium. ita cum inferioribus pariter peruolans anno uno XII signa percurrit, tricesimo die ad aliud transiens signum. supra solem igitur et eius circulum Martis est stella, quae abest a sole tonum dimidium. itaque dicitur diebus LX ad aliud signum transire. supra hunc circulum Iouis est stella, quae abest a Martis tonum dimidium. itaque anno uno transit ad alterum signum. nouissima stella Saturni, quae maximo uehitur circulo; haec autem abest a Ioue tonum. itaque annis XXX duodecim signa percurrit. ab ipsorum tamen siderum corporibus Saturnus abest tonum unum et dimidium.
Some think that when the sun is said to be in the Ram or in any sign, it makes its journey above the very stars of the Ram. Those who use this reasoning wander far from the true reason. For neither the sun nor the moon appears nearest the stars. For this reason too some have imagined 7 wandering stars, adding to them the sun and the moon, because they are carried with the five stars. The moon, in fact, is nearest to the earth; and so it is thought to pass through the whole world in 30 days. This happens by this reasoning: as if someone were to make circles within the zodiac circle, and were to imagine them at such an interval that the earth is in the middle, and were to make one measure from the earth to the moon, which the Greeks have called τόνον (tonos) (this, however, because they could not say that it was a fixed distance, they called τόνον): so the moon is distant from the earth by one tonus. For this reason, because it is carried on the shortest circle, in 30 days it reaches the first sign. From this circle the circle is distant by half a tonus on which the star of Hermes is carried; and so, passing in 30 days to the next sign, more slowly. From this circle another half tonus is distant; in which place the star of Aphrodite directs its journey, making a slower course than Hermes's star. For it passes to another sign in 30 days. Above this star is the sun's course, which is distant from Hesperus, the star that is Aphrodite's, by half a tonus. So, flying along equally with the lower ones, it runs through the 12 signs in one year, passing on the thirtieth day to another sign. Above the sun, then, and its circle is the star of Ares, which is half a tonus from the sun. And so it is said to pass to another sign in 60 days. Above this circle is Zeus's star, which is half a tonus from Ares's. And so in one year it passes to the next sign. The last is the star of Cronus, which is carried on the greatest circle; this is distant a tonus from Zeus's. And so in 30 years it runs through the twelve signs. From the bodies of the stars themselves, however, Cronus's star is a tonus and a half distant.
Hac igitur ratione potes scire neque solem, neque lunam contingere stellas, et nihilominus per zodiacum circulum uerti. hinc etiam possumus intellegere lunam minorem esse sole. omnia enim quae proxima sunt nobis, maiora necesse est esse, quam quae longo discedente interuallo uidemus. igitur lunam uidemus proxime nos esse, neque eam maiorem aspectui nostro esse quam solem. illud quoque necesse est, cum sol non longe absit a luna et a nobis maior uidetur, si prope nos accesserit, multo maiorem futurum. praeterea necesse est, ut ante diximus, aut nullam stellam erraticam esse, aut solem cum luna pariter ut reliquas stellas errare. si enim quisquam mihi potest demonstrare V stellarum cursum, et dicere, quod hodie quaeque earum ad aliud transeat signum, quemadmodum de sole et luna fieri uidemus, et nihilominus suum efficit cursum, non est erratica. si autem dubium est, quod hodie transeat et ad aliud signum compari ratione cum luna feratur, et suum cursum dirigat, quemadmodum stellae quae sunt dubiae, necesse est has quoque errare. sed non euenit ut errent, praesertim cum suo tempore ad cursum reuertantur. igitur ne stellae quidem, cum certo tempore ad suum signum reuertantur, possunt errare, nisi forte uolumus accipere excusationem, quod duo corpora magna facilius possint obseruari, quam singulae stellae, quae non certos cursus conficientes uidentur apparere.
By this reasoning you can know that neither the sun nor the moon touches the stars, and nonetheless they revolve through the zodiac circle. From this we can also understand that the moon is smaller than the sun. For everything nearest to us must be bigger than what we see at a long interval. Now we see that the moon is nearest to us, and that it is not larger to our sight than the sun. This too is necessary: since the sun, which is not far from the moon, already appears larger to us, if it came near us it would be much larger. Moreover it is necessary, as we said before, that either there is no wandering star, or that the sun with the moon wanders equally with the other stars. For if anyone can show me the course of the 5 stars, and say that today each of them passes to another sign, as we see happen with the sun and moon, and nonetheless completes its course, it is not wandering. If, however, it is doubtful whether it passes today and, on a like reckoning with the moon, is carried to another sign and directs its course, as the stars that are doubtful, these too must wander. But it does not come about that they wander, especially since they return to their course in their own time. So not even the stars, since they return to their own sign at a fixed time, can wander, unless perhaps we wish to accept the excuse that two great bodies can be observed more easily than single stars, which, not making fixed courses, appear to be seen [?].
Cite This Text