The discovery of a world in the moone

by John Wilkins

Keplar thinkes that our earth receives that light whereby it shines from the Sunne, but this (saith he) is not such an intended cleare brightnesse as the Moone is capable of, and therefore hee guesses, that the earth there is of a more chokie soyle like the Ile of Creete, and so is better able to reflect a stronger light, whereas our earth must supply this intention with the quantity of its body, but this I conceive to be a needlesse conjecture, since our earth if all things were well considered, will be found able enough to reflect as great a light. For

1. Consider its opacity, if you marke these sublunary things, you shall perceive that amongst them, those that are most perspicuous, are not so well able to reverberate the Sunne beames as the thicker bodies. The rayes passe singly through a diaphanous matter, but in an opacous substance they are doubled in their returne and multiplyed by reflexion. Now if the moone and the other Planets can shine so clearely by beating backe the Sunne beames, why may not the earth also shine as well, which agrees with them in the cause of this brightnesse their opacity?

2. Consider what a cleare light wee may discerne reflected from the earth in the middest of Summer, and withall conceive how much greater that must bee which is under the line, where the rayes are more directly and strongly reverberated.

3. Consider the great distance at which wee behold the Planets, for this must needs adde much to their shining and therefore Cusanus (in the above cited place) thinkes that if a man were in the Sunne, that Planet would not appeare so bright to him, as now it doth to us, because then his eye could discerne but little, whereas here wee may comprehend the beames as they are contracted in a narrow body. Keplar beholding the earth from a high mountaine when it was enlightned by the Sunne confesses that it appeared unto him of an incredible brightnesse, whereas then the reflected rayes entered into his sight obliquely; but how much brighter would it have appeared if hee might in a direct line behold the whole globe of earth and these rayes gathered together? So that if wee consider that great light which the earth receives from the Sunne in the Summer, and then suppose wee were in the Moone, where wee might see the whole earth hanging in those vast spaces where there is nothing to terminate the sight, but those beames which are there contracted into a little compasse; I say, if wee doe well consider this, wee may easily conceive, that our earth appeares as bright to those other inhabitants in the Moone, as theirs doth to us.

Proposition 12.

That tis probable there may bee such Meteors belonging to that world in the Moone, as there are with us.

Plutarch discussing this point affirmes that it is not necessary there should be the same meanes of growth and fructifying in both these worlds, since nature might in her policy finde out more waies then one how to bring about the same effect. But however he thinks its probable that the Moone her selfe sendeth forth warme winds, and by the swiftnesse of her motion there should breathe out a sweet and comfortable ayer, pleasant dewes and gentle moysture, which might serve for the refreshing and nourishment of the inhabitants and plants in that other world.

But since they have all things alike with us, as sea and land, and vaporous ayer encompassing both, I should rather therefore thinke that nature there should use the same way of producing meteors as she doth with us (and not by a motion as Plutarch supposes) because shee doth not love to vary from her usuall operations without some extraordinary impediment, but still keepes her beaten path unlesse she be driven thence.

One argument whereby I shall manifest this truth, may be taken from those new Starres which have appeared in divers ages of the world, and by their parallax have beene discerned to have been above the Moone, such as was that in Cassiopeia, that in Sagittarius, with many others betwixt the Planets. Hipparchus in his time tooke especiall notice of such as these, Plin. nat. hist. l. 2. c. 26. and therefore fancied out such constellations in which to place the Starres, shewing how many there were in every asterisme, that so afterwards posterity might know, whether there were any new Starre produced or any old one missing. Now the nature of these Comets may probably manifest, that in this other world there are other meteors also; for these in all likelihood are nothing else but such evaporations caused by the Sunne, from the bodies of the Planets. I shall prove this by shewing the improbabilities and inconveniences of any other opinion.

For the better pursuite of this ’tis in the first place requisite that I deale with our chiefe adversary, Cæsar la Galla, who doth most directly oppose that truth which is here to bee proved. Hee endeavouring to confirme the incorruptibility of the Heavens, and being there to satisfie the argument which is taken from these comets, He answers it thus: Aut argumentum desumptum ex paralaxi non est efficax, aut si est efficax, eorum instrumentorum usum decipere, vel ratione astri vel medii, vel distantiæ, aut ergo erat in suprema parte aeris, aut si in cœlo, tum forsan factum erat ex reflectione radiorum Saturni & Jovis, qui tunc in conjunctione fuerant.