If you behold the Moone a little before or after the conjunction, when she is in a sextile with the Sunne, you may discerne not onely the part which is enlightned, but the rest also to have in it a kind of a duskish light; but if you chuse out such a situation, where some house or chimney (being some 70 or 80 paces distant from you) may hide from your eye the enlightned hornes, you may then discerne a greater and more remarkable shining in those parts unto which the Sunne beames cannot reach; nay there is so great a light, that by the helpe of a good perspective you may discerne its spots. In so much that Blancanus the Jesuite speaking of it, sayes,⁹ Haec experientia ita me aliquando fefellit, ut in hunc fulgorem casu ac repente incidens, existimarim novo quodam miraculo tempore adolescentis lunae factum esse plenilunium. This experiment did once so deceive mee, that happening upon the sight of this brightnesse upon a sudden, I thought that by some new miracle the Moone had beene got into her full a little after her change.

But now this light is not proper to the Moone; it doth not proceed from the rayes of the Sunne which doth penetrate her body, nor is it caused by any other of the Planets and Starres. Therefore it must necessarily follow, that it comes from the earth. The two first of these I have already proved, and as for the last, it is confidently affirmed by Caelius,¹⁰ Quod si in disquisitionem evocet quis, an lunari syderi lucem foenerent planetae item alii, asseveranter astruendum non foenerare. If any should aske whether the other Planets lend any light to the Moone? I answer, they doe not. True indeed, the noble Tycho discussing the reason of this light attributes it to the Planet Venus;¹¹ and I grant that this may convey some light to the Moone; but that it is not the cause of this whereof wee now discourse, is of it selfe sufficiently plaine, because Venus is sometimes over the Moone, when as shee cannot convey any light to that part which is turned from her.

It doth not proceed from the fixed starres; for then it would retaine the same light in ecclipses, whereas the light at such times is more ruddy and dull. Then also the light of the Moone would not be greater or lesser, according to its distance from the edge of the earths shadow, since it did at all times equally participate this light of the starres.

In briefe, this is neither proper to the Moone, nor does it proceed from any penetration of the Suns rays, or the shining of Venus, or the other Planets, or the fixed starrs. Now because there is no other body in the whole Universe, save the earth, it remaines that this light must necessarily be caused by that, which with a just gratitude repaies to the Moone such illumination as it receives from her.

And as loving friends equally participate of the same joy and griefe, so doe these mutually partake of the same light from the Sunne, and the same darkenesse from the eclipses, being allo severally helped by one another in their greatest wants: For when the Moone is in conjunction with the Sun, & her upper part receives all the light, then her lower Hemispheare (which would otherwise be altogether darke) is enlightened by the reflexion of the Sunne-beames from the earth. When these two Planets are in opposition, then that part of the earth which could not receive any light from the Sunne-beames, is most enlightened by the Moone, being then in her full; and as shee doth most illuminate the earth when the Sunne-beames cannot, so the gratefull earth returnes to her as great (nay greater) light when shee most wants it; so that alwayes that visible part of the Moone which receives nothing from the Sunne, is enlightened by the earth, as is proved by Galilaeus, with many more arguments, in that Treatise which he calls Systema mundi. True indeed, when the Moone comes to a quartile, then you can neither discerne this light, nor yet the darker part of her body, and that for a double reason.

1. Because the neerer it comes to the full, the lesse light dos it receive from the earth, whose illumination dos always decrease in the same proportion as the Moone dos increase.

2. Because of the exuperancy of the light in the other parts. Quippe illustratum medium speciem recipit valentiorem,¹² the clearer brightnesse involves the weaker, it being with the species of sight, as it is with those of sound; and as the greater noise drowns the lesse, so the brighter object hides that which is more obscure. But as they do always in their mutuall vicissitudes participate of one anothers light; so also doe they partake of the same defects and darknings; for when our Moone is eclipsed, then is their Sunne darkned; and when our Sun is eclipsed, then is their Moon deprived of its light, as you may see affirmed by Meslin. Quod si terram nobis ex alto liceret intueri,¹³ quemadmodum deficientem lunam ex longinquo spectare possumus, videremus tempore eclipsis solis terrae aliquam partem lumine solis deficere, eodem planè modo sicut ex opposito luna deficit. If we might behold this globe of earth at the same distance, as we doe the Moon in her defect, wee might discerne some part of it darkened in the Sunnes eclipses, just so as the Moone is in hers. For as our Moone is eclipsed by the interposition of our earth, so is their Moone eclipsed by the interposition of theirs. The manner of this mutuall illumination betwixt these two you may plainly discerne in this Figure following.

Where A represents the Sunne, B the Earth, and C the Moone; Now suppose the Moone C to be in a sextile of increase, when there is onely one small part of her body enlightened, then the earth B will have such a part of its visible Hemispheare darkned, as is proportionable to that part of the Moone which is enlightened; and as for so much of the Moone, as the Sun-beames cannot reach unto, it receives light from a proportionall part of the earth which shines upon it, as you may plainly perceive by the Figure.

You see then that agreement and similitude which there is betwixt our earth and the Moone. Now the greatest difference which makes them unlike, is this, that the Moone enlightens our earth round about, whereas our earth gives light onely to that Hemispheare of the Moone which is visible unto us, as may be certainly gathered from the constant appearance of the same spots, which could not thus come to passe, if the Moone had such a diurnall motion about its owne axis as perhaps our earth hath. And though some suppose her to move in an epicycle, yet this doth not so turne her body round, that wee may discerne both Hemispheares; for according to that hypothesis (say they) the motion of her eccentrick doth turne her face towards us, as much as the other doth from us.

But now, if any question what they doe for a Moone who live in the upper part of her body? I answer, the solving of this, is the most uncertaine and difficult thing that I know of, concerning this whole matter. But yet unto mee this seemes a probable conjecture.

That the upper Hemispheare of the Moone doth receive a sufficient light from those Planets about it; and amongst these, Venus (it may bee) bestowes a more especiall brightnesse, since Galilaeus hath plainly discerned that she suffers the same increases and decreases; as the Moone hath, and ‘tis probable that this may bee perceived there, without the help of a glasse, because they are farre neerer it than wee. When Venus (saith Keplar) lies downe in the Perige or lower part of her supposed Epicycle, then is she in conjunction with her husband the Sunne, from whom after shee hath departed for the space of ten moneths, shee gets plenum uterum, and is in the full.

But you’ll reply, though Venus may bestow some light when she is over the Moone, and in conjunction, yet being in opposition, she is not visible to them, and what shall they then doe for light?

I answer, then they have none; nor doth this make so great a difference betwixt those two Hemispheares, as there is with us, betwixt the places under the poles, and the line. And besides, ‘tis considerable, that there are two kinde of Planets.

1. Primarie, such whose proper circles doe encompasse the body of the Sunne, whereof there are six. Saturne, Iupiter, Mars, Ceres or the Earth, Venus, Mercury. As in the Frontispice.

2. Secondary, such whose proper circles are not about the Sunne, but some of the other primarie Planets. Thus are there two about Saturne, foure about Iupiter, and thus likewise dos the Moone encompasse our earth. Now tis probable that these lesser, secondary Planets, are not so accommodated with all conveniences of habitation, as the others that are more principall.

But it may seeme a very difficult thing to conceive, how so grosse and darke a body as our earth, should yeeld such a cleere light as proceeds from the Moone; and therefore the Cardinall de Cusa (who thinks every Starre to be a severall wo[…]ld) is of opinion that the light of the Sunne is not able to make them appeare so bright;¹⁴ but the reason of their shining is, because wee behold them at a great distance through their regions of fire which doe set a shining lustre upon those bodies that of themselves are darke. Vnde si quis esset extra regionem ignis, terra ista in circumferentia suae regionis per medium ignis lucida stella appareret. So that if a man were beyond the region of fire, this earth would appeare through that, as a bright Starre. But if this were the onely reason, then would the Moone be freed from such increases and decreases as shee is now lyable unto.

Keplar thinks that our earth receives that light whereby it shines, from the Sunne, but this (saith he) is not such an intended cleare brightnes as the Moon is capable of, and therefore he guesses, that the earth there, is of a more chokie soyle, like the Ile of Crete, 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 bee a needlesse conjecture, since our earth, if all things were well considered, will bee 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 cleerely 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 we 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. ‘Tis considerable that though the Moon dos in the night time seeme to be of so cleere a brightnesse, yet when wee looke upon it in the day, it appeares like some little whitish cloud: Not but that at both times, she is of an equall light in her selfe. The reason of this difference is, because in the night wee looke upon it through a darke and obscure medium, there being no other enlightned body, whose brightnesse may abate from this: Whereas in the day time, the whole heavens round about it, are of an equall clearenesse, and so make it to appeare with a weaker light. Now because wee cannot see how the enlightned parts of our earth doe looke in the night, therefore in comparing it with the Moone, wee must not consider her, as she is beheld through the advantage of a darke medium, but as she seemes in the day-time: Now, in any cleere Sun-shine-day, our earth does appeare as bright as the Moone, which at the same time does seeme like some duskish cloud (as any little observation may easily manifest.) Therefore we need not doubt but that the earth is as well able to give light, as the Moone. To this, it may be added that those very clouds, which in the day-time seeme to be of an equall light to the moone, doe in the evening become as darke as our earth; and as for those of them, which are looked upon at any great distance, they are often mistaken for the mountaines.

4. Tis considerable, that though the moone seeme to bee of so great a brightnesse in the night, by reason of its neerenesse unto those severall shadowes which it casts, yet is it of it selfe weaker than that part of twilight, which usually wee have for halfe an houre after Sunne-set, because wee cannot till after that time discerne any shadow to be made by it.

5. Consider the great distance at which we behold the Planets, for this must needs adde much to their shining; and therefore Cusanus (in the above cited place) thinks 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, we 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 brightnes, whereas then he could onely see some small parts of it; 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 we 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 we 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.

But here it may bee objected, that with us, for many days in the yeare, the heavens are so overclowded, that wee cannot see the Sunne at all, and for the most part, in our brightest dayes, there are many scattered clouds which shade the earth in sundry places; so that in this respect, it must needs be unlike the Moon and will not be able to yeeld so cleare, unintermitted a light, as it receives from that planet.

To this I answer.

1. As for those lesser brighter clouds which for the most part are scattered up and down in the clearest days, these can be no reason why our earth should be of a darker appearance, because these clouds being neere unto the earth, and so not distinguishable at so great a distance from it, and likewise being illuminated on their back parts by the Sunne that shines upon them,¹⁵ must seeme as bright to those in the Moone, as if the beames were immediately reflected from our earth.

2. When these clouds that are interposed, are of any large extension or great opacity, as it is in extraordinary lasting and great rains, then there must be some discernable alteration in the light of our earth; But yet this dos not make it to differ from the Moone: since it is so also with that Planet, as is shewed in the later part of the next chapter.

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Footnotes

1. De gen animal. l. 4. 12. ↩

2. Golden Number. ↩

3. Plut. de fac. lunae. ↩

4. Somn. Scip. l. 1. c. 19. ↩

5. Ant. lect. l. 1. c. 4. ↩

6. In epist. ad Sebast. Fantonum. ↩

7. Praefat. ad Austriaca syd. ↩

8. Meteor. l. 1. c. 2. Art. 2. ↩

9. De mundi fab. p. 3. c. 3. ↩

10. Ant. Lect. l. 20. c. 5. ↩

11. Progym. 1. ↩

12. Scal. exerc. 62. ↩

13. Epit. Astro. l. 4. part. 2. ↩

14. De doct. ig. l. 2. c. 12. ↩

15. LIB. 1. Cap. 12. ↩