SIDEREAL OBSERVATIONS

Let us first speak of the surface of the Moon which faces us. For the sake of easier understanding, I distinguish two parts: namely, one brighter and the other darker. The brighter part appears to surround and overflow the entire hemisphere, while the darker part infects the face itself like a certain cloud and renders it spotted. These somewhat dark and quite large spots are obvious to everyone, and every age has seen them; for this reason, we shall call them the large or ancient spots, to distinguish them from other spots smaller in size, but so thickly scattered that they sprinkle the entire Lunar surface, especially the brighter part.

These, in fact, have been observed by no one before us. From repeated inspections of them, we have been led to the opinion that we certainly understand the surface of the Moon to be not polished, even, and of a most exact sphericity—as a great cohort of Philosophers Galileo refers here to the Aristotelian school, which maintained that celestial bodies were perfect, smooth spheres. has thought concerning it and the other celestial bodies—but on the contrary, it is uneven, rough, and crowded with cavities and protrusions, not otherwise than the face of the Earth itself, which is marked here and there by mountain ridges and depths of valleys. The appearances from which it was possible to gather these conclusions are of this sort.

On the fourth or fifth day after conjunction original: "coniunctionem"; this refers to the New Moon, when the Moon is between the Earth and the Sun., when the Moon offers itself to us with shining horns, the boundary dividing the dark part from the luminous part The "terminator" line between day and night on the lunar surface. does not extend evenly according to an oval line, as would happen in a perfectly spherical solid; rather, it is designated by an uneven, rough, and very wavy line, just as the accompanying figure represents. For many bright excrescences, as it were, extend beyond the confines of light and darkness into the dark part, and conversely, dark particles enter into the light. Furthermore, a great number of blackish spots...