"The concentric Revolutions of the Planets about the Sun, proceed from a Compound Motion; a Gravitation towards the Sun, which is a constant Energy infused into Matter, by the Author of all Things; and a Projected, Transverse Impulse, in Tangents to their several Orbs, that was also Imprinted at first by the Divine Arm upon them, & will carry them around, until the End of all Things. Now, admitting, that Gravity may bee essential to Matter; and that a Transverse Impulse might likewise bee acquired by Natural Causes; yett, for all the Planets to move about the Sun, in Circular Orbs, there must bee given to each, a Determinate Impulse, & these present particular Degrees of Velocity, which they now have, in Proportion to their Distances from the Sun, & to the quantity of the Solar Matter. For, had the Velocities of the several Planets, been greater or smaller than they are, at the same Distances from the Sun, or, had their Distance from the Sun, or the quantity of the Suns Matter, & consequently his Attractive Power, been greater or smaller than they are; now with the same Velocities; They would not have Revolved in Concentric Circles, as they do, but have moved in Hyperbola’s or Parabola’s, or in Ellipses very Eccentric. And what wee thus assert about the Primary Planets, may also bee applyed unto the Secondary. Now, that all these Distances, and Motions, and Quantities of Matter, should bee so accurately & Harmoniously adjusted, in this great Variety of our System, it is above the Fortuitous Hitts, of meer, blind, material Causes; it must certainly flow, from the Disposals of that infinitely Wise and Good Being, who, as Plato saies, αεί γεωµετρει, j alwayes acts geometrically. If the Planets had moved in such Lines, as wee have described, sometimes they would have approached the Sun, as near as the Orb of Mercury, and sometimes have exorbitate{d} beyond the Distance of Saturn, & some of them, would have quite left the Sun, with{out} ever seeing him any more. Now, the very Constitution of a Planet, would have been Corrupted, & Ruined, by such a Change of Interval, between It, and the Sun; and no Animals could ever have endured such Excesses of Heat and Cold.
"Furthermore, The Æthereal Spaces are perfect{ly} Fluid; they neither do assist, nor, do they retard, the Revolutions of the Planets, which rowl thro’ those Regions, as unresisted, as if they moved in a Vacuum. They might, any of them have moved in Courses opposite unto the present, and in Planes crossing the Planes of the Ecliptic, in any kind of Angles. Now if the System had been fortuitously framed by the convening Matter of a Chaos, how should all the Planets, as well the primary as the secondary, move the Same Way, from the West to the East, & in the Same Plane too, without any considerable Variation? Here would bee Millions of Millions of Odds to an Unit, in such a Cast of a Chance; and therefore, tis to some Divine Conduct, that such a Regular Harmony must bee ascribed. Especially, if wee consid{er,} that the smallest Planets, are scituated nearest the Sun, & each other; whereas Jupiter and Saturn, that are vastly greater than the rest, & have many Satell{ites} about them, are happily placed at the extreme Regions of the System, and Immensely Distant. At so wide a Distance, they do in their Conjunctions, a little Disturb one another, by their Gravitating Powers; but if such huge Masses of Matter had been scituated much nearer to the Sun, or to one another, the Disturban{ce} in the World, must have been consider{able.}
"To pass on; Our Ear{th par}ticularly, is placed so conveniently, {that} the Creatures which inhabit it, live and {thrive} in their Habitation. The Distance fro{m}{the Sun as it now turns, most likely is} Better, than any greater or smaller Distance would have been. Tis mathematically certain, That the Heat of the Sun, is, according to the Density of the Sun-beams, and is Reciprocally Proportional to the Square of the Distance, from the Body of the Sun. By this Calculation, if the Earth should now Revolve, suppose, in the Orbit of Mercury, the whole Ocean would boil with Extremity of Heat, & bee exhal’d into Vapours, and all that growes upon the Dry Land, would bee consumed as in a Fiery Furnace. But suppose the Earth should bee carried as far off as the Orbit of Saturn; There the whole Globe would bee one Frigid Zone, the deepest Seas under the very Equator, would bee frozen to the bottom, and there would bee nothing of Animation, or Germination in these forlorn Regions of the Universe. Place the Earth yett at any other Distance, and still you alter it for the worse, proportionally to the Alteration. Tis then in a Place, which an infinitely Intelligent, & Voluntary Agent hath assign’d unto it. But if any one think, How then can any thing live in Mercury, or in Saturn? Lett him also think, That the Matter of each Planet, may have a Texture very Different, which will dispose the same to bee acted on, by greater or smaller Degrees of Heat, according to their several Scituations, & that the Lawes of Life, and Vegetation & Propagation, are the Arbitrary Pleasure of God, and may vary in every Planet, as Hee pleases, to us Incomprehensibly. Tis enough, that the Texture of Ours, is inconsistent with any other Scituation: Wee could not wear Flesh and Blood, any where else.
"Moreover; The Earth Revolves with a Double Motion: while tis carried round the Sun, in the Orbis Magnus once a Year, it perpetually wheels about its own Axis, once in a Day, in every twenty four Hours, turning all the Parts of the Equinoctial to the Rayes of the Sun. Conspicuous are the Uses of this Vertiginous Motion; this tis that successively gives Day and Night, over the Face of the whole Earth, and makes it all over Habitable; Without this Diurnal Rotation, one Hæmisphære would ly Dead, in perpetual Darkness, Frost, and Cold, and the best Part of the other, wasted with a permanent Heat wherein it must ly basking without Intermission. The Vicissitudes made by the Earths Moving about its own Center, are better, than an Exposing of the same Side alwayes unto the Sun.
"But whence came these Vicissitudes? The Earth might Annually have compassed the Sun, without such a daily Turn; as wee see the Moon ever showes the same Face unto us. Indeed, Shee does in her menstrual Orb, turn all her Globe to the Sun, and enjoy Dayes and Nights, alternately Fourteen Times as long as ours. But should the Earth bee deprived of its Diurnal Motion, one half of it, must never see any Dayes at all. Behold, that Glory of Him, that made Things, as now they are Besides; Compare the Diurnal and the An{nu}al Revolutions of the Earth, which have a {ve}ry Different Degree of Velocitie. In {ev}ery Natural Day, all Parts of the Equator {h}ave some thing more than Three of the Earths Diameters, which makes about Eleven Hundred in the Space of a Year. But within the same Space, the Center of the Earth is carried more than fifty times as far, once round the Orbis Magnus, whose Wideness wee now assume to bee Twenty Thousand Terrestrial Diameters. The Annual Motion therefore is more than Fifty Times swifter than the Diurnal. But it must bee acknowledged, That since the Earth Revolves not upon a Material, but a Geometrical Plane, their Proportions may bee varied in Innumerable Degrees, any of which might have happened as easily as the present. What was it then that præscribed this particular Proportion and Celerity to each Motion? Tis certain, That there is a Meliority in the present Constitution. Suppose the Annual Motion of the Earth, were now performed in Six Months rather than Twelve; The Seasons then, would bee Twice as short as they are, and the cold Winters would overtake us before any of our Fruits could bee Ripe. Were the Motion Retarded, the Mischief would on the other Side be as fatal; for most Countreyes would bee so parched & effæte, by the Draught of the Summers, that they could never have an Harvest of a Store sufficient for the Consumption of a Double Year.
"And then, for the Diurnal Motion of the Earth; suppose it made only Twelve Circuits in a Year; Then every Day & Night, would bee Thirty Times as long as they are Now, and not at all suited unto any Humane Affayrs. But on the other Hand, suppose it wheeled a Thousand Times about its own Center, while the Center describes one Circle about the Sun; Then an Equinoctial Day would bee but Four Hours; and such Hasty Returns of Evening would sadly confound, all our Labours, and our Journeyes, & our other Affayrs.
"Yett further; Lett the Mode of the Earths Diurnal Motion bee considered. Conceive an Imaginary Plane, which passing thro’ the Centers of the Sun, & of the Earth, extends itself on all Sides as far as the Firmament; This Plane is called, The Ecliptic; and in this, the Center of the Earth is carried without any Deviation. But then the Axis of the Earth, about which its Diurnal Rotation is made, is not erect, unto the Plane of this Ecliptic, but Inclines towards it, from the Perpendiculum, in an Angle of Twenty Three Degrees, and an Half. Now, why is the Axis of the Earth, in this Particular Posture, and not in any other? Was this, by Chance, or from Choice? Wee all know, that this Inclined Position of the Axis, which keeps alwayes the same Direction, and to construct Parallelism to itself, is the sole Cause of those grateful, and needful Vicissitudes, of the Four Seasons of the Year, and the Variation in the Length of Dayes. If wee take away the Inclination, it would absolutely undo our Northern Nations; the Sun would never come nearer us, than hee doth now, on the Tenth of March, or the Twelfth of September. But would wee rather part with the Parallelism? Suppose then, that the Axis of the Earth, keeps alwayes the same Inclination towards the Body of the Sun. This would cause indeed a Varietie of Dayes, and Nights, and Seasons, on the Earth, but then every particular Countrey, would have alwayes the same Diversity of Day and Night, and the same Constitution of Season, without any Alternation; some would alwayes have Long Nights and Short Dayes: others again perpetually Long Dayes and Short Nights: one Climate would bee sweltered with everlasting Dog-Dayes, while an eternal December blasted another. But shall the Axis rather observe no constant Inclination to any thing, but vary and waver in all Manner of Uncertainty? Truly, there could bee no Health, no Life, no Subsistence in such an Irregular System: by the surprizing Nods of the Pole, wee might bee tossed backward or forward, from January to June, yea, possibly from the January of Greenland, to the June of Abyssinia. Certainly, the present Constitution, is more Beneficial for us, than any other. Some have Imagined, that if the Poles had been erect unto the Plane of Ecliptic, all Mankind had enjoy’d a Perpetual Spring, & a very Paradise upon Earth, with all the Comforts, in the utmost Measures of Longævity. But this perpetual, and universal Spring, is a meer Poetical Fancy; & bating the Equalitie of Dayes and Nights, in all other Points tis an Impossible Imagination. To the People, who dwell near the Equator, the Spring, so much admired, would bee an Insupportable Summer: and as for the Countreyes nearer the Pole, tis not a Spring that would answer their Necessities; they must have nearer Approaches of the Sun, with longer Dayes, & a less Obliquity of his Rayes, a Summer, & an Harvest, for the Ripening of their Fruits, or else bid an eternal adieu to the very best of their Sustenance. An equal Distribution of the same yearly Heat, would no more bring our Fruits unto Maturity, than such a quantity of Fuel, gradually & successively lighted, would make Water to boil, which being all kindled at once, will do it immediately. A perpetual Equinox would render the best Parts of the Globe, no other than perpetually Desolate. And the Expectation of a Constant Serenity, from such a Position of the Sphære, this also, is but precarious: For the affections of the Atmosphære, do not proceed only from the Course of the Sun, but also from the Scituations and Exhalations of the Earth, & many other uncertain Causes. Nor are the Equinoxes of our Year, upon Experience found, more free from Tempestuous Exorbitances, than any of the other Seasons, which also dismisses the Fond Hopes of Longævity, from such a Spring, as these do talk of: Longævity, can’t bee prov’d, the Effect of meer Calm; and the Inhabitants of the Torrid Zone, are generally, both shorter-lived than other People, & inferiour to them in Strength, Stature, & courage, as well as Intellectual Capacities."
Leonardo: Salvator Mundi
