XIII.
Sic igitur orientibus XII signis, reliqua corpora occidere et exoriri uidentur. sed ut ante diximus, nunc protinus de solis cursu dicemus. Necesse est enim solem aut ipsum per se moueri, aut cum mundo uerti uno loco manentem. quod si maneret, necesse erat eodem loco occidere et exoriri, a quo pridie fuerat exortus, quemadmodum signa eodem loco semper oriuntur et occidunt. praeterea si ita esset, necesse erat dies et noctes omnes aequales esse; ut quam longus hodiernus dies fuerit, tam longus semper sit futurus, item nox simili ratione semper aequalis permaneat. quod quoniam non est, illud quoque necesse est, cum uideamus esse dies inaequales, et solem alio loco hodie occasurum, et alio heri occidisse. si igitur aliis locis occidit et oritur, necesse est eum moueri, non stare.
XIII. The sun's course
So, with the twelve signs rising, the other bodies are seen to set and to rise. But, as we said before, we shall now speak straightaway of the sun's course. For the sun must either move of itself, or turn with the world, remaining in one place. If it remained, it would have to set and rise at the place from which it had risen the day before, as the signs always rise and set in the same place. Moreover, if so, all days and nights would have to be equal; as long as today's day was, so long would it always be, and likewise the night would always remain equal in a like manner. Since this is not so, this too is necessary, since we see that days are unequal: that the sun will set today in one place, and set yesterday at another. If, therefore, it sets and rises in different places, it must be moving, not standing still.
Solem autem contra mundi motum currere, sic possumus intellegere. eucnit enim, ut duabus in causis sidera non possimus uidere. quarum una est, cum abierint infra terram, nostrum quoque effugere conspectum, ita ut inferius hemisphaerium ostendit. altera autem est ratio, quod propter fulgorem solis et uim maximam luminis sidera obscurentur, siue quod stellis obsistit, ne candor earum ad nostros perueniat adpectus; siue sui magnitudine luminis officit oculis nostris, ne praeter eius ignem aliam rem superiorem perspiciamus: quod magis ueri simile uidetur. neque enim solis ignem eiusmodi uidemus, cuiusmodi reliquos ignes intellegimus, sed ita lumen auertit nostrum, ut ipse quoque nobis non igneus, sed albus uideatur esse. praeterea in unaquaque nocte XI signa necesse est apparere, ideo quod uno signo sol ipse nixus, iter conficere uidetur, cuius figuram corporis ipse suo lumine obscurat; cum eo enim signo et occidere et exoriri uidetur. nonnulli dicunt nos XII signa dumtaxat hac ratione perspicere posse, si in eius signi prima nouissimaue parte consistat. habent enim XII signa partes eiusmodi, ut unumquodque eorum in longitudine habeat partes XXX, in latitudine autem partes XII. itaque euenit, ut in longitudine signorum annus, in latitudine autem dies sit. in parte prima signi nihilominus reliquum corpus eius signi uideri posse nonnulli dicunt, ut simili ratione et si fuerit in extrema parte signi: quod fieri non potest. nam cum sol sit in qualibet parte signi et exoriatur, ita magnum uidetur habere fulgorem, ut omnia sidera obscuret. illud tamen potest euenire, ut cum sol sit in prima parte signi et occidat, reliquum corpus eius signi appareat. sed certius et uerius est XI signa quam XII apparere posse.
That the sun runs against the motion of the world, we can understand thus. It happens that for two reasons we cannot see the stars. One is when they have gone beneath the earth, escaping our sight, so that the lower hemisphere shows [them]. The other reason is that on account of the sun's brilliance and the very great force of its light the stars are obscured, either because it stands in the way of the stars, so that their brightness does not reach our sight; or because by the size of its light it hinders our eyes, so that apart from its fire we do not perceive anything else above: which seems more likely. For we do not see the sun's fire as being of the kind that we understand other fires to be, but it so turns away our light that it itself too appears to us not fiery but white. Besides, on every night 11 signs must appear, because the sun itself, resting on one sign, is seen to make its journey, and that sign's body it obscures with its own light; for it is seen to set and rise with that sign. Some say that we can see the 12 signs only on this condition, if the sun stands at the first or last part of that sign. For the twelve signs have parts such that each of them has 30 parts in length and 12 in breadth. So it comes about that in the length of the signs is the year, in the breadth the day. Some say that in the first part of the sign nonetheless the remaining body of that sign can be seen, and likewise also if it is in the last part of the sign: which cannot be. For when the sun is in any part of a sign and rises, it appears to have so great a brilliance that it obscures all the stars. This, however, can happen: that when the sun is in the first part of a sign and sets, the remaining body of that sign appears. But it is more certain and truer that 11 signs, rather than 12, can appear.
Praeterea quaeritur, quare sol contra mundi inclinationem currens, uideatur cum ipsa sua sphaera occidere et uerti. nam si sol non contra siderum occasum curreret, de Ariete ad Pisces, non ad Taurum transiret. exoriri etenim Pisces prius quam Aries et occidere perspiciuntur; et ita mundus uerti uidetur, ut prius Pisces quam Aries occidant. igitur diebus XXX sol in Ariete currens et eius corpus obscurans, sic dumtaxat apparet sol, ut ex eo loco, quo Aries ante, exoriri uideatur et post dies XXX sol uideatur ab eodem loco surgere, ex quo loco Taurus ante oriri uidebatur. igitur apparet solem ab Ariete ad Taurum transire. quod si ita est, necesse est eum contra mundi inclinationem currere.
Moreover it is asked why the sun, running against the inclination of the world, seems to set and turn with its own sphere. For if the sun did not run against the setting of the stars, it would pass from the Ram to the Fishes, not to the Bull. For the Fishes are seen to rise before the Ram, and to set; and the world seems to turn so that the Fishes set before the Ram. So, for 30 days running in the Ram and obscuring its body, the sun appears in such a way that it seems to rise from the place where the Ram was before, and after 30 days the sun is seen to rise from the same place from which the Bull was before seen to rise. So it appears that the sun passes from the Ram to the Bull. If this is so, it must run against the inclination of the world.
Quare autem euenit, ut ante diximus, quod uidetur cum mundo sol uerti, eius similis haec est causa. ut si quis in nauiculae rostro sedens, hinc quaerat ad puppim transire, et nihilominus ipsa nauis iter suum conficiat, ille quidem uidebitur contra nauiculae cursum ire, sed tamen eodem perueniet quo nauis. hoc autem sic etiam facilius intellegitur, si nauem diuiseris in partes CCCLX, quemadmodum sol diebus CCCLX simul mundum transigit. eodem modo, ut ante diximus, si nauis sit diuisa et in una parte de trecentis sexaginta constituatur quilibet eorum (nauis autem habet unius diei cursum), ille quidem contra nauem ire, sed cum ea ad locum definitum peruenire intellegetur. non enim extra nauem est, qui a rostro ad puppim transit, sed ipsa naui continetur. item sol cum per ipsum mundum iter conficiat et eo contineatur, uidetur contra mundum ire, sed cum eo peruenit ad occasum. cum enim mundus trecenties et sexagies se conuerterit, tunc sol iter annuum conficit
But the reason why, as we said before, the sun seems to turn with the world is like this: as if someone, sitting in the prow of a little boat, seeks to pass to the stern, and the boat itself nonetheless completes its journey, he will seem to go against the course of the boat, but will arrive all the same where the boat arrives. It is the easier to understand in this way if you divide the boat into 360 parts, as the sun passes through the world in 360 days at once. In the same way, as we said before, if the boat is divided and someone is placed on one part of the 360 (the boat, moreover, makes the course of one day), he will be understood to go against the boat but with it to arrive at the appointed place. For he who passes from prow to stern is not outside the boat but contained in the boat itself. Likewise the sun, since it makes its journey through the world itself and is contained by it, seems to go against the world, but with it arrives at setting. For when the world has turned 360 times, then the sun completes its annual journey.
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