The chiefe reasons for the confirmation of this truth, are implyed in the inconveniences of this Hypothesis above any other; whereby wee may resolve the motions and appearances of the Heavens into more easie and naturall causes.
Hence will the frame of nature bee freed from that deformitie, which it ha’s according to the Systeme of Tycho: who though he make the Sunne to be in the midst of the Planets, yet without any good reason, denies it to be in the midst of the fixed Starres; as if the Planets, which are such eminent parts of the World, should bee appointed to move about a distinct centre of their owne, which was beside that of the Vniverse.
Hence likewise are wee freed from many of those inconveniences in the Hypothesis of Ptolomy, who supposed in the Heavens, Eppicides and Eccentrickes, and other Orbes, which he calls the differents of the Apoge and the Perige. As if nature in framing this great engine of the World, had been put unto such hard shifts, that shee was faine to make use of wheeles and screwes, and other the like artificiall instruments of motion.
There bee sundry other particulars, whereby this opinion concerning the Sunnes being in the centre, may bee strongly evidenced: which because they relate unto severall motions also, cannot therefore properly be insisted on in this place. You may easily enough discerne them, by considering the whole frame of the Heavens, as they are according to the Systeme of Copernicus; wherein, all those probable resolutions that are given for divers appearances amongst the Planets, doe mainly depend upon this supposition, that the Sunne is in the centre. Which Arguments (were there no other) might be abundantly enough for the confirmation of it. But for the greater plenty, there are likewise these probabilities considerable.
1 It may seem agreeable to reason, that the light which is diffused in severall Starres through the circumference of the World, should be more eminently contained, and (as it were) contracted in the centre of it, which can only be by placing the Sunne there.
2 ‘Tis an Argument of1 Clavius, and frequently urged by our adversaries, That the most naturall scituation of the Sunnes body was in the midst, betwixt the other Planets; and that for this reason, because from thence he might more conveniently distribute amongst them both his light and heate. The force of which, may more properly bee applyed to proove him in the centre.
3 ‘Tis probable that the planetarie Orbes (which are speciall parts of the Vniverse) doe moove about the centre of the World, rather than about any other centre which is remote from it. But now ‘tis evident, that the Planet Saturne, Iupiter, Mars, Venus, Mercury, doe by their motion encompasse the body of the Sunne. ‘Tis likely therefore, that this is scituated in the midst of the World.
As for the three upper Planet, ‘tis found by observation, that they are alwaies neerest to the Earth, when in opposition to the Sunne, and farthest from us, when in conjunction with it: which difference is so eminent, that Mars in his Perige do’s appeare sixty times bigger than when hee is in the Apoge, and at the greatest distance.
Now, that the revolution of Venus and Mercury also is about the Sun, may from hence be evidenced: first, because they are never at any great distance from him: secondly, because they are seen sometimes above, and sometimes below him: thirdly, because Venus, according to her different scituations, do’s change her appearance, as the Moone.
4 There is yet another Argument, which2 Aristotle himselfe do’s repeat from Pythagoras. The most excellent body should have the best place; but the Sunne is the most excellent body, and the centre is the best place; therfore ‘tis likely the Sunne is in the centre. In the frame of nature (which is supposed to be of an orbicular forme) there are but two places of any eminency, the circumference and the centre. The circumference being of so wide a capacity, cannot so fitly be the peculiar seat of a body, that is so little in respect of it: and besides, that which is the most excellent part of the World, should bee equally preserved in it selfe, and shared in it’s vertues by all the other parts, which can only be done by it’s being placed in the midst of them. This is intimated unto us in that frequent speech of Plato, that the Soule of the World do’s reside in the innermost place of it: and that in3 Macrobius, who often compares the sun in the World, to the Heart in a living creature.
Vnto this Aristotle answers by a distinction: There is medium magnitudinis, so the centre is the middle of a Sphaere: and there is medium naturae, or informationis, which is not alwayes the same with the other; for in this sence the Heart is the middle of a man; because from thence (saith hee) as from the centre, the vitall spirits are conveied to all the members: and yet we know that it is not the centre of Magnitude, or at an equall distance from all the other parts.
And besides, the middle is the worst place, because most circumscribed, since that is more excellent which do’s limit any thing, than that which is bounded by it. For this reason is it, that Matter is amongst those things which are terminated, and Forme, that which do’s circumscribe.
But against this answer of Aristotle, it is againe replyed:
1 Though it be true,4 that in living creatures the best and chiefest part is not placed alwaies just in the midst, yet this may be, because they are not of an orbicular forme, as the World is.
2 Though that which bounds another thing be more excellent than that which is terminated by it, yet this do’s not proove the centre to bee the worst place, because that is one of the tearmes or limits of a round body, as well as the circumference.
There are likewise other Arguments to this purpose, much insisted on by eminent Astronomers,5 taken from that harmonicall proportion which there may be betwixt the several distance and bignesse of the Orbs, if we suppose the Sun to be in the centre.
For according to this (say they) wee may conceive an excellent Harmonie both in the number and the distance of the Planets: (and if God made all other things numero & mensurâ, much more then those greater Works, the Heavens) for then the five Mathematicall bodies, so much spoken of by6 Euclid, wil beare in them a proportion answerable to the severall distances of the Planets from one another.
Thus a Cube will measure the distance betwixt Saturne and Iupiter; a Pyramis or Tetraëdron, the distance betwixt Iupiter and Mars; a Dodecaëdron, the distance betwixt Mars and the Earth; an Icosaëdron, the distance betwixt the Earth and Venus; and an Octoëdron, the distance betwixt Venus and Mercury; that is, if we conceive a circumference described immediately without the Cube, and another within it, the distance betweene these two will shew what proportionall distance there is betwixt the Orbe of Saturne, and that of Iupiter. Thus also, if you conceive a circumference described on the outside of a Pyramis or Tetraëdron, and another within it, this will shew such a proportionall distance, as there is betwixt the Orbe of Mars, from that of Iupiter. And so of the rest.
Now if any aske why there are but six Planetary Orbs? Keplar answers: Quia non oportet plures quàm quinque proportiones esse, totidem nempè quot regularia sunt in Mathesi corpora. Sex autèm termini consummant hunc proportionum numerum: Because there are but five proportions, so many as there are regular bodies in Mathematickes, each of whose sides and angles are equall to one another. But now there are six tearmes required to consummate this number of proportions; and so consequently, there can bee but six primary Planets.
Thus likewise by placing the Sunne in the centre,7 wee may conceive such a proportion betwixt the Bodies of the Planets, as will be answerable unto their severall Sphaeres: Then Mercury, which ha’s the least Orbe, will have the least Body; Venus bigger than that, but lesse than any of the other; our Earth bigger than Venus, but lesse than the rest; Mars bigger than the Earth, but lesse than Iupiter; Iupiter bigger than Mars, and lesse than Saturne; Saturne being the highest, should also be the biggest. All which Harmony would bee disturbed by putting in the Sunne amongst them; and therfore, it may be more convenient for him to sit still in the centre.
There are sundry other Arguments in this kinde to be found out, by a consideration of this whole Hypothesis: Hee that do’s rightly understand it, may therein easily discerne many strong probabilities, why the Sun should be in the midst of the World, rather than in any other position.
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