Tycho maintains that heaven and air are made of two distinct substances. But in truth, with some small qualification, they share one and the same opinion about the substance and matter of the heavens: that it is not hard and impenetrable, as the Aristotelians hold—a transparent “fifth essence”—but penetrable and soft as air itself, and that the planets move in it as birds do in the air and fish in the sea.

They prove this by the motion of comets and in other ways, though Chiaramonti firmly opposes it in his Anti-Tycho. Comets are not generated, as Aristotle teaches, in the region of air from a hot, dry exhalation and then consumed, but consist of celestial matter, as Anaxagoras and Democritus held long ago.

Tycho, Eliseus, Roeslin, Thaddeus, Hagecius, Pena, Rothmann, and Fracastoro demonstrate this from their courses, parallaxes, and refractions, and from the motions of the planets, which intersect and cut across one another’s spheres, now higher and then lower. Mars, among the rest, sometimes comes nearer to the earth than the sun, as Kepler confirms from his own and Tycho’s accurate observations, and at another time is again high in Jupiter’s sphere.

There are other sufficient reasons for placing them far above the moon. Meanwhile, this rejects that element of fire, those imaginary first watery movers—I mean the heavens above the firmament affirmed by Del Río, Lodovicus Imola, Patrizi, and many of the Church Fathers—and those monstrous spheres of eccentrics, and eccentric circles carrying epicycles.

However firmly Ptolemy, Alhazen, Witelo, Peurbach, Magini, Clavius, and many of their associates maintain that these are real spheres—eccentric, concentric, equant circles, and so on—they are absurd and ridiculous. Who is so mad as to think there are so many circles, like interconnected wheels in a clock, all hard and impenetrable, as these men imagine, adding and subtracting at will?

Magini makes eleven heavens, subdivided into their spheres and circles, and all are too few to account for those particular appearances. Fracastoro makes seventy-two concentric spheres. Tycho Brahe, Nicolaus Reimers, Heliseus, and Roeslin have peculiar hypotheses of their own invention; and they are only inventions, as most of them acknowledge. Just as we admit equators, tropics, colures, and Arctic and Antarctic Circles for the sake of teaching—though Ramius thinks them all unnecessary—they would have these supposed only for method and order.

Tycho has devised I know not how many subdivisions of epicycles within epicycles, and so on, to calculate and represent the moon’s motion. Yet, when all is said and done, they are a supposition and nothing more: not, as he maintains, hard, impenetrable, subtle, transparent, and so on, or making music, as Pythagoras maintained long ago and Robert Constantin more recently, but always quiet, fluid, open, and so on.

If, then, the heavens are penetrable, as these men say, and offer no obstacles, it would be no bad thing, on this aerial journey, to make wings and fly up, as that Turk in Busbecq made his fellow citizens in Constantinople believe he would do. Some ingenious lover of novelties, I think, ought sooner or later to discover how. If that cannot be done, then with a telescope like Galileo’s, or the wings of Icaromenippus in Lucian, we might at least survey the spheres and heavens, and see what happens among them.

Whether things come into being and pass away in the heavens, as some think on the evidence of celestial comets—the one in Cassiopeia in 1572, that in Cygnus in 1600, that in Sagittarius in 1604, and many others. The Italian philosopher Giulio Cesare La Galla will by no means admit this in chapter 9 of his physical disputation with Galileo, On Phenomena in the Lunar Orb. Or were they created from the beginning and do they show themselves at set times, with poles, axes, circles of their own, and regular motions, as Helisaeus Roeslin contends?

For “they do not perish, but diminish and disappear,” Blancanus holds. They come and go at intervals, casting their tails away from the sun—some of them as a burning glass projects the sun’s beams. Yet not always: sometimes a comet casts its tail away from Venus, as Tycho observes; and, as Helisaeus Roeslin says of some others, away from the moon, with little stars around them, “to the astonishment of astronomers, together with many other wonders in heaven.” All these, along with those Medicean, Austrian, and Bourbon stars, indicate that the heaven of the planets is undivided, pure, and open, and that the planets move in it “under fixed laws and within fixed bounds.”

Examine likewise: “Is heaven coloured?” Are the stars as large and as distant as astronomers report? Are there as many as they say—1,026, or 1,725 according to Johann Bayer; or, as some rabbis say, 29,000 myriads; or an infinite number, as Galileo discovers through his telescopes? Is the Milky Way a mingled light of small stars, like so many nails in a door, or all in a row like those 12,000 islands of the Maldives in the Indian Ocean? Is the smallest visible star in the eighth sphere eighteen times larger than the earth and, as Tycho calculates, 14,000 earth radii away from it?

Are they denser parts of the spheres, as Aristotle teaches, or so many habitable worlds, as Democritus holds? Do they have light of their own or receive it from the sun, or cast light all around, as Patrizi discusses? “Are they equally distant from the centre of the world?” Does light belong to their essence, and is that light a substance or an accidental property? Are they hot in themselves, or do they produce heat incidentally? Is there such a precession of the equinoxes as Copernicus holds, or does the eighth sphere move?