The discovery of a world in the moone

by John Wilkins

1. From that light which is discerned in her, when there is a totall eclipse of her owne body, or of the Sunne.

2. For the light which is discerned in the darker part of her body, when she is but a little distant from the Sunne.

1. For when there are any totall eclipses, there appeares in her body a great rednesse, and many times light enough to cause a remarkeable shade, as common experience doth sufficiently manifest: but this cannot come from the Sunne, since at such times either the earth, or her owne body shades her from the Sun-beames, therefore it must proceede from her owne light.

2. Two or three daies after the new Moone, wee may perceive light in her whole body, whereas the rayes of the Sun reflect but upon a small part of that which is visible, therefore ’tis likely that there is some light of her owne.

In answering to these objections, I shall first shew, that this light cannot be her owne, and then declare that which is the true reason of it.

That it is not her own, appeares

1. From the variety of it at divers times; for ’tis commonly observed, that sometimes ’tis of a brighter, sometimes of a darker appearance, now redder, and at another time of a more duskish colour. The observation of this variety in divers eclipses, you may see set downe by Keplar Opt. Astron. c. 7. num. 3. and many others, but now this could not be if that light were her owne, that being constantly the same, and without any reason of such an alteration: So that thus I may argue.

If there were any light proper to the Moone, then would that Planet appeare brightest when she is eclipied in her Perige, being neerest to the earth, and so consequently more obscure and duskish when she is in her Apoge or farthest from it; the reason is, because the neerer any enlightened body comes to the sight, by so much the more strong are the species and the better perceived. This sequell is granted by some of our adversaries, and they are the very words of noble Tycho, De nova stella lib. 1. c. 10. Si luna genuino gauderet lumine, utique cum in umbra terræ esset, illud non amitteret, sed eò evidentiùs exereret, omne enim lumen in tenebris, plus splendet cum alio majore fulgore non præpeditur. If the Moone had any light of her owne, then would she not lose it in the earths shadow, but rather shine more clearely, since every light appeares greater in the darke, when it is not hindered by a more perspicuous brightnesse.

But now the event falls out cleane contrary, (as observation doth manifest, and our opposites themselves doe grant) Reinhold comment. in Purb. Theor. pag. 164. the Moone appearing with a more reddish and cleare light when she is eclipsed being in her Apoge or farthest distance, and a more blackish yron colour when she is in her Perige or neerest to us, therefore shee hath not any light of her owne. Nor may we thinke that the earths shadow can cloud the proper light of the Moone from appearing, or take away any thing from her inherent brightnesse, for this were to thinke a shadow to be a body, an opinion altogether mis-becomming a Philosopher, as Tycho grants in the fore-cited place, Nec umbra terræ corporeum quid est, aut densa aliqua substantia, aut lunæ lumen obtenebrare possit, atque id visui nostro præripere, sed est quædam privatio luminis solaris, ob interpositum opacum corpus terræ. Nor is the earths shadow any corporall thing, or thicke substance, that it can cloud the Moones brightnesse, or take it away from our sight, but it is a meere privation of the Suns light, by reason of the interposition of the earths opacous body.

2. If shee had any light of her owne then that would in it selfe be, either such a ruddy brightnesse as appeares in the eclipses, or else such a leaden duskish light as wee see in the darker parts of her body, when shee is a little past the conjunction. (That it must be one of these may follow from the opposite arguments) but it is neither of these, therefore she hath none of her owne.