[I.] To show that the globe of the Earth is at the center of the heaven and of this visible World, many arguments are wont to be brought, drawn from those things which appear to us concerning the heaven and the celestial [bodies]; about which [see] Aristotle (2nd On the Heaven, ch. 13, texts 97 & 103, and the interpreters there); Ptolemy (bk. 1 of the Almagest, chs. 5 & 6); Cleomedes (bk. 1 of the Cyclic Theory, ch. 9); Alfraganus (difference 4); Sacrobosco (in the Sphere, ch. 1, and there Clavius from p. 135 to 143); Maurolyco (Dialogue 1 of the Cosmography, p. 9); Barozzi (bk. 1 of the Cosmography, p. 33); Blancanus (in the Sphere, bk. 4, ch. 1); Liceti (in the disputations On the single center of the Earth’s motion); and George Buchanan (bk. 1 of the Sphere), with whose verses it seems [fitting] to make a prelude.

[Margin: Buchanan’s verses for the Earth’s situation in the middle of the World.]

Nor is it less easy to know this by sure signs: if the earth were less distant from the eastern gate than from the Tartessian boundary that receives the wearied axles [of day, the West], then Phoebus, rising at morning, gleaming with conspicuous rays, as he lifted his head would show a larger orb, and again, in the coming night, a smaller. Why should I recount the stars — both those which glide along the same perpetual track, and those which, with unequal steps, wander constantly through the liquid fields of heaven — [since,] when they pass nearer, they will seem to us of greater bodily growth; while, when they are farther off, by reason of distance they will show a smaller face? Nay, observe the Sun: when, straight from the summit of heaven, he strikes the Ethiopians with no point of his rays; when the vine-leaf protects the tender fruits with its shade — if the eastern ruler of light then drove his chariot nearer to the lands, a greater part of his course would have to be traversed when the light is spent, and the Sun would scale heaven’s heights in few morning hours up the opposite slope, and, late, would bury his team in the western ocean over a greater space. On the contrary, if the earth, near the western goal, were far distant from the eastern, then Titan, long climbing at morning to the lofty peak of the aether, would swiftly plunge into the Hesperian waves; nor would he, midmost, from his throne of the high aether, divide the times of light by equal spaces, as now he does. Moreover, if the Sun showed himself nearer to the Indians [the East] than he sets to the Hesperians [the West], he would — laying down smaller shadows — cast them in equal hours, than the shores of Calpe [Gibraltar] when, descending, he seeks the night, shaking the reins: for if an opaque body be set before a light, it stretches its shadows the longer and darker, the more you remove the light from the dense body. Now, since the Sun casts equal shadows in equal spaces, he looks back upon the earth on every side with equal spaces — the earth’s western orb and its eastern equally near to the [dawn-]gate; but it neither, sloping, leans toward the warm South [Auster], nor rises up toward the Maenalian Bear [the North]; but, hanging in the middle interval between either Pole, it divides the surrounding heaven by an equal boundary.

Do you not see, when the swallow, messenger of gentle spring, warns that the darkness is equal with the daylight [the spring equinox]? Or when Libra tempers the days and nights by a just balance [the autumn equinox], and, milder, fosters the grapes with gentle heat — when, rising in the new morning with rosy dawn, Phoebus pours the darts of his rays upon the moist lands, and the towered houses, and the battlements armed with pinnacles, and the boundary which shuts out quarrels from the neighbors: the field’s tree casts the straight points of its shadows toward the late couch of Phoebus [the West]; again, departing late in the evening, while panting Phoebus buries his horses in the waves, the rosy point of the shadows is stretched toward the [eastern] risings; and when the Sun, descending, holds Capricorn in the rainy South, or when, lofty, he flashes in the [northern] Bears and kindles the watery arms of Cancer, now the shadow seeks the oblique South [Notus], now the North [Boreas]. But if the earth, abandoning the middle station of the world, leaned more toward the Parrhasian Bear [the North], every shadow would extend itself toward the cold North; but if it inclined more toward the moist South, every shadow would extend itself toward the moist South, and, flowing crosswise, the evening [shadow] would then cut the shadow stretched far from the eastern mountains. But neither, were the earth not on the axis midway between either pole, would the earth’s Delian [Moon] grow suddenly pale from the shadow, the light of her brother [the Sun] withdrawn — as often as, the heaven divided by an equal boundary, [the earth] casts its orb opposite to the Solar rays.

Yet very many of the aforesaid arguments, which the other Authors indicated above also adduce, are valid only so far as to show that the Earth cannot be outside the plane of the celestial Ecliptic, or running out beyond the center of the Equator toward the South or North — which not even the Copernicans say; therefore, those [arguments] being passed over, we shall select the remaining arguments.

I. General Argument, from the Phenomena agreeing with the Earth’s situation in the middle of the World

[Margin: 1st Argument. Form.]

[II.] If the Earth is placed at the center of the World, all the celestial Phenomena are saved, and this supposition corresponds to the observations made by Astronomers. Therefore the Earth is at the center of the World.

[Margin: Aristotle’s argument for the Earth’s situation.]

This indeed is Aristotle’s argument (2nd On the Heaven, text 103), saying: Those things also which are said by the Mathematicians concerning Astronomy bear witness; for the [phenomena] which appear come to pass with the figures [configurations] transferred, by which the order of the stars is determined — the Earth being placed, as it were, in the middle.

[Margin: Response to Argument 1.]

The Copernicans respond, the Antecedent being conceded, by denying the Consequence and turning the argument back: for the same Phenomena are saved if the Earth be supposed to be turned about its own axis by the motion of whirling, and about the Sun by the annual motion of translation; therefore the Earth is so moved. Since, then, the said Phenomena are saved in either way, the consequence is necessary for neither hypothesis; and the argument, reduced to form, rests on two particular affirmatives — from which nothing is necessarily concluded.

II. Argument, from the Two apparent motions in the Planets

[Margin: 2nd Argument.]

[III.] If the Earth were moved circularly, it would have to be moved by more than one motion. But it cannot be moved by more than one motion. Therefore the Earth is not moved circularly.

The Major is clear from an induction made in all the spheres which are moved circularly; wherefore, if the Earth were placed among the Planets, it too would have to be moved by more than one motion. The Minor is proved, because great changes would appear in the fixed stars, and in their rising and setting, which do not appear. And this is Aristotle’s argument (bk. 2, On the Heaven, text 97), which it is pleasing to express in his own words:

[Margin: Aristotle’s other argument for the Earth’s situation.]

Moreover, all things which are carried by a circular carrying seem to fall behind [lag], and to be moved by more than one carrying, except the first sphere; wherefore it is necessary that the Earth too — whether it be carried placed around the middle, or in the middle — be moved by two carryings. But if this happen, it is necessary that there come about a chan[ge]…

[…continues on p. 449 (PDF 484) with the catchword “tatio-” (mu-tatio-nes) — “…a change and conversion of the fixed stars; but this does not seem to happen,” completing Aristotle’s text 97.]

(printed p. 449 — within Chapter XXVII: Arguments II–VII from the celestial phenomena, each conceded physically but denied under astronomical rigor. They argue from the fixed stars’ constant risings and settings, the always-visible celestial hemisphere, the stars’ equal apparent magnitude at rising and setting, gnomon shadows, the alternation of days and nights, and lunar eclipses always at opposition. The responses turn on the immense stellar distance making the Earth’s offset insensible and on the diurnal and annual motions saving the same appearances.)

[Header: DE SYSTEMATE TERRÆ MOTÆ — 449]

…[a change] and conversion of the fixed stars; but this does not seem to happen; rather, the same [stars] always rise and set at the same places of it. — But the Philosopher excepts the first sphere, that is the Primum Mobile, to which he attributes a single motion, namely the diurnal.

[Margin: Response to the argument.]

It is responded by conceding the Major concerning the real motions, [but] denying [it] concerning the apparent; and, on the contrary, by denying the Minor concerning the real [motions], [but] conceding [it] concerning the apparent — of which alone the proof holds. For since, on this hypothesis, the eyes of the observers are moved together with the Earth by both motions, the Earth’s own motions cannot appear to us; yet from its real motions it follows that the stars appear to us of the same size, according to what is soon to be said.

III. Argument, from the Hemisphere and half of the Heaven always appearing

[Margin: 3rd Argument. Form.]

[IV.] If the Earth were not in the middle of the World, the whole hemisphere of the heaven (or half of any [circle] of the heaven) could not appear to us, placed wherever on earth; nor would six signs of the Zodiac always stand above the horizon. But observation of all places of the earth and of all ages teaches the contrary. Therefore, etc.

[Margin: Response.]

It is responded by distinguishing the Major, and conceding it if neither the Earth were moved by the diurnal motion of 24 hours, nor the semidiameter of the annual orb were of insensible proportion to the semidiameter of the sphere of the fixed [stars], nor, finally, the semidiameter of the terrestrial globe were small (to sense) in relation to the semidiameter of the heavens; but otherwise, the Major is denied. For from the diurnal motion of 24 hours it comes about that [the Earth] behaves, as regards the rising and setting of the stars, just as if they revolved around the Earth as the center of their revolution. And from the immense distance of the Fixed [stars] and of the visible signs of the Zodiac, in relation to the distance of the Earth from the center of the World and of the Fixed [stars] — which is, to sense, nothing — it comes about that six signs always appear, and the whole hemisphere of the sphere of the Fixed [stars]. Finally, from the smallness of the terrestrial semidiameter, compared with the semidiameter of the other spheres pertaining to the Planets, it comes about that a very tiny and scarcely sensible portion of the planetary heaven is hidden from us; nor does the Earth’s semidiameter snatch from us — turned toward one quadrant of the heaven — an arc greater than the horizontal parallax of each Planet (which, in the Moon, is a little more than one degree, but in the other Planets less than one degree; how great it is, is clear from what was said in bk. 3, ch. 8, where [I treat] of the Sun’s; bk. 4, ch. 14, of the Moon’s parallaxes; and bk. 7, sect. 6, ch. 7, of the other Planets’ parallaxes). Therefore, the horizontal parallax being subtracted from the quadrant (or from the 90 degrees), there remain 89 degrees and more (if you except the Moon), which we see turned toward the East, and as many turned toward the West; wherefore it is no wonder if we see almost the whole half of the heaven, even the Planetary. And hence too it comes about that the earth seems a point in relation to the heaven (especially the supreme), as Ptolemy (bk. 1, Almagest, ch. 6), Alfraganus (diff. 4), Proclus (in the Sphere), Clavius (in the Sphere, p. 143), and others contend.

IV. Argument, from the apparent Magnitude of the Stars

[Margin: 4th Argument. Form.]

[V.] If the Earth were not in the middle of the visible World, the same Stars would not appear equal to themselves at rising, at midnight, and at setting; but they do appear equal to themselves. Therefore, etc.

The Major is proved, because from that part of the Earth which was nearer the heaven they would appear larger. But if you say that the vapors of the horizon hinder this view, let stars be taken seen near the Meridian in different horizons (says Clavius, p. 136 of the Sphere); for all then see Arcturus of the same magnitude, and so of the rest — even at different times of the year.

[Margin: Response.]

It is responded by conceding the Major if the distance of the Earth from the World’s center were sensible (or of notable proportion) to the Stars’ distance; or if the Earth were not physically and to sense in the middle of the World; but [the Major is] denied if the proportion between the said distances be insensible — or if the Earth be in the middle physically, granted not mathematically.

V. Argument, from the Shadows of Gnomons

[Margin: 5th Argument. Form.]

[VI.] If the Earth were not in the middle of the World, the eastern shadows of Gnomons would not be equal to the western at an equal altitude of the Sun, nor would they describe a straight line on the horizontal plane on the Equinoctial days. The consequent is false and against observations; therefore also the antecedent, from which it follows.

The Major is proved by Cleomedes (bk. 1, Cyclic Theory, ch. 9), because, if the Earth came nearer to the East, the shadows of gnomons at sunrise would be shorter than at sunset (for the nearer a luminous body is, other things being equal, the more contracted the shadows become); on the contrary, if the Earth came nearer to the West, the shadows of the setting Sun would be shorter than of the rising; but if the Earth came nearer to one of the poles, the equinoctial shadows would describe a curved line, as on the days outside the equinoxes.

[Margin: Response.]

It is responded by conceding the Major if the Earth came notably nearer to the rising Sun than to the setting, on account of [its] position in the annual orb; but otherwise [it is] denied. For in fact the Earth is no more distant from the Sun (whether rising or setting) than the Sun is distant from the Earth on the other hypothesis — since the Sun is placed at the center of the Earth’s Great Orb, or as near as possible to this center. And in the same way it is responded to the argument taken from the forenoon semidiurnal arc, which does not seem [likely] to be equal to the afternoon.

VI. Argument, from the Alternation of days and nights

[Margin: 6th Argument. Form and Response.]

[VII.] If the Earth were outside the world’s center, the two Equinoxes each year would not occur, nor the two Solstices, nor the rest of the vicissitudes of days which appear in the threefold sphere — namely the Right, the Parallel, and the Oblique. The consequent is false. Therefore, etc.

It is responded, the Major being conceded, if the Earth were not carried round annually in the Plane of the Ecliptic about the Sun [placed] at, or near, the immovable center of the world; or [if it were carried] not in such a way that the terrestrial Equator were inclined to the Ecliptic by 23½ degrees and always parallel to itself; but otherwise, the Major is denied.

VII. Argument, from the Eclipses of the Moon

[Margin: 7th Argument. Form.]

[VIII.] If the Earth were not in the middle of the World, Eclipses of the Moon would not always occur with the Moon existing under that place of the Zodiac opposite to [the place] under which the Sun is. But Eclipses of the Moon always occur with the Moon and the Sun existing under opposite places of the Zodiac. Therefore the Earth is in the middle of the World.

The Minor is acknowledged among the Astronomers of every age. The Major seems to be shown by Ptolemy (bk. 1, Almagest, ch. 5) in these words: And, to touch on it briefly: the whole order which appears in the increments and decrements of days and nights would be utterly confounded, unless the earth held the middle situation. Moreover, the Eclipses of the Moon too, [which now] happen in whatever parts of the heaven, could not occur in the place opposite the Sun, since the Earth would more often oppose itself to it not in opposition, but in spaces smaller than a semicircle. Which argument Averroes (bk. 2, On the Heaven, at text 103), Johann Regiomontanus (bk. 1 of the Epitome of the Almagest), Maurolyco (Dialogue 1 of the Cosmography, p. 9), and our Clavius (on the Sphere, p. 142) urge; but Maurolyco and Clavius lean upon this proof more earnestly, each of whom thinks the matter can be made out from only two Eclipses, using this diagram, in which are represented two Lunar Eclipses made at different places of the Zodiac — but in such a way that the Sun’s place under the Zodiac is opposite to the Moon’s place under the Zodiac, and so when the centers of the Luminaries are opposed through a diameter; from which they say it follows that the Earth — whose shadow C eclipses the Moon — is on both diameters, and so in their common section; wherefore, since all the diameters of the World intersect one another at the center of the World, it is necessar[y]…

[Engraved figure (#40) — the two-eclipse demonstration. A circle (the Zodiac) with two radiant Suns drawn at the upper left and upper right; from each Sun a straight line (a diameter, drawn as an arrow) crosses the circle through its interior; the two diameters intersect at the central point C — the Earth’s shadow that eclipses the Moon. Since the shadow C lies on both diameters at once, it sits at their common intersection; and as all diameters of the World cross at the World’s center, the Earth (at C) is necessarily at that center.]

[…continues on p. 450 (PDF 485) with the catchword “se” (neces-se) — “…it is necessary [that the Earth be at the center of the World],” completing the Maurolyco–Clavius two-eclipse proof, and Riccioli’s response.]

(printed p. 450 — within Chapter XXVII, the last two arguments conclude the chapter, and Chapter XXVIII opens. Argument VII (lunar eclipses) and Argument VIII (horizontal lunar eclipses, Argoli’s boast) are answered: both strike only an immovable off-center Earth, not the Copernican system, where the Earth lies on the line between the luminaries. Argument IX, from the evidence of the Sun’s motion, receives the Copernican response, with Riccioli’s verdict that physical evidence still favors the Sun’s motion. Chapter XXVIII then opens with three arguments from the parallax of the annual orb, defining that parallax.)

[Header: BOOK IX. SECTION IV.]

…it is necessary, they think, that the Earth be at the center of the World; and Maurolyco thinks this so manifest that he concludes nothing of doubt remains.

[Margin: Response to Argument 7.]

It is responded, nevertheless, by distinguishing the Major, and conceding it if the Earth were so outside the center of the World that not the Earth itself, but the Sun (just as the Moon also) revolved around it — the Sun annually, the Moon monthly. But the same Major is denied if the center of the Earth, carrying the Lunar heaven with it, revolves annually about the Sun [placed] nearest the world’s center, while the Moon performs monthly revolutions about the Earth: for then the Sun can be beheld from the Earth under any place of the Zodiac, and the Moon under the opposite place, and thus any Lunar Eclipse [can] occur in the diametrical opposition of the Luminaries. Wherefore the argument of the aforesaid Astronomers does not assail the Copernicans, but those who might perhaps imagine that the Sun moves annually about the center of the World, and that the Earth, devoid of an annual revolution, is outside the center of the World. But for the Copernicans, look at the Diagram set out in ch. 4, no. 17.

VIII. Argument, from Horizontal Eclipses of the Moon

[Margin: 8th Argument. Form.]

[IX.] If the Earth were outside the center of the World, Eclipses of the Moon could never occur with both luminaries appearing on the Horizon. But Eclipses of this kind do sometimes occur. Therefore the Earth is not outside the center of the World.

This indeed is the argument in which, through inexperience, Andreas Argoli sang a triumph against Copernicus (in the Ephemeris of the year 1668), on the occasion of a Lunar Eclipse to come on the 25th of May, which, with respect to the Roman Horizon, will be so disposed that, in the morning at sunrise, the Moon — diametrically opposite to it and now about to set beneath the Horizon — will appear Eclipsed. The words of this author are:

[Margin: Argoli’s argument, but empty against the Copernicans.]

The second Lunar Eclipse [is on] the 25th of May, at hour 16, 26′; whose calculation and figure we have set down on purpose, since it occurs nearly at sunrise, and for this reason — that one may see whether, in the opposition of the Luminaries, both are beheld from the Horizon — [it is] an indication that the earth is established in the middle of the Firmament, against the Copernicans. Although this can constantly be observed from the rising or setting of the Palilician [Aldebaran], or Antares — stars diametrically opposite — one of which, established in the East, the other is offered to be beheld in the West, and conversely.

The Major, therefore, of the proposed argument is thus proved: If a Lunar Eclipse must occur in such a way that the Moon is not only diametrically opposite the Sun, but also both Luminaries appear at the same time on the Horizon, it is necessary that a whole hemisphere (or semicircle of the Zodiac) be seen, since the Luminaries are then distant from each other by a whole semicircle; but a whole semicircle of the Zodiac cannot be seen by us unless we and our Earth be at the center of the celestial Zodiac, and so unless [it be] at the center of the Firmament. The Minor is proved by examples of Horizontal Eclipses, and by the witnesses Pliny (bk. 2, ch. 13) and Mästlin (in [his work] on Eclipses) — about which [see] more in our bk. 5, ch. 5, proposition 5; nay, there is no Lunar Eclipse which, with respect to some Horizon, is not such — since there is no moment in which the Sun does not rise to some Horizon.

[Margin: Response to Argument 8.]

It is responded, nevertheless, by distinguishing the Major, and conceding it if the Earth were outside the center of the World but immovable, and the Sun were turned in the annual orb about the World’s center (as Argoli still imagines); but denying the Major if the center of the Earth revolves with an annual period about the Sun (set near the World’s center), and the Moon [revolves] about the Earth with a monthly circuit. For it is not necessary, for the Phenomenon of such Eclipses, that we see a whole semicircle of the celestial Zodiac; but it suffices that the Earth be in that Ecliptic which it describes by its center, so placed that it sees the Sun under one point of this Ecliptic, and the Moon under the opposite (so far as the Moon’s Latitude permits), and so that the Earth be in a straight line interposed between the Luminaries: all the rest are joined per accidens with these Eclipses. Yet, for this — that at the same time Aldebaran can be beheld in the East and Antares in the West, and that by each of the inhabitants of the Earth — it is required that the Earth be in the middle of the World physically, and so that its distance from the center of the World have no sensible proportion to the distance of the Fixed [stars]: as has been said more than once.

IX. Argument, from the Evidence of the Sun’s motion

[Margin: 9th Argument. Form.]

[X.] If it be evident, physically, that the Sun is moved annually about the center of the World, it is evident that the Earth is not so moved, but is at the center of the World. But it is evident, physically, that the Sun is moved annually about the center of the World. Therefore it is evident that the Earth is not so moved, but is at the center of the World.

The Major is certain, at least on the Copernican hypothesis, in which the Earth is carried round in the annual orb about the immovable Sun only for this — that through it there may be furnished that which the Sun, in the annual orb about the resting earth, is supposed by others to furnish; granted that, in Astronomical rigor, it is not repugnant for both globes to be carried round annually, at equal pace, under the Zodiac. The Minor is proved, because it is no less — nay, more — evident physically that the Sun is moved by its proper motion, than that the other Planets [are moved] by their proper motion toward the East; since both the motions of the others are attempered to the Sun’s motion, and the daily elongation of the Planets from some Fixed [star] toward the East (which is the argument of their proper motion) appears no less, nay more, in the Sun. But now it is so evident physically that the other Planets are moved by their proper motion, that their motion cannot be commuted into the Earth’s motion; wherefore not even the Sun’s apparent motion can be commuted into the Earth’s motion, without injury to Physical evidence.

[Margin: Response to Argument 9, but invalid.]

They respond: let the Major pass; [we respond] by denying the Minor; for it is evident only by a sub-disjunction — that either the Sun is moved annually about the Earth, or the Earth about the Sun — since it is certain that, if we were on the Sun, the Earth would appear to us to be moved under the Zodiac, just as now, [we] being established on the Earth, the Sun appears to us to be moved. But that we cannot perceive the Earth’s annual motion (if there be any) — the cause is that it is common to us and to our eyes, which are transferred if the Earth is transferred; on account of which we would not perceive even the Sun’s motion, [we] being established on the Sun, even if it were really moved and the Earth at rest. Since these things are so, those who Philosophize circumspectly ought not (they say) to deduce from this appearance the real motion of one rather than of the other, but only the apparent motion of the Sun. — To the proof of the Minor it is responded by denying the parity, because the Phenomena of all the Planets cannot be saved if the Earth be supposed to be moved about them [at rest] and to perform their periods in reality; but both their phenomena and the Sun’s can stand, if the Earth be supposed to be moved annually about the Sun (resting near the center of the World) in such a way that its motion is between the orb of Mars and of Venus, etc., according to the system set out in ch. 4, no. 15, and ch. 8, no. 22.

Nevertheless that disjunctive proposition is evident not only physically, but mathematically; but Physical evidence alone, taken absolutely, stands for the motion of the Sun, and that suffices, so long as the opposite is not demonstrated.

✠ [Chapter XXVII ends here.]