NICOLAUS COPERNICUS

ON THE REVOLUTIONS

BOOK ONE.

Chapter 1: That the universe is spherical.

A decorative woodcut initial 'P' depicting a seated figure, possibly a scholar or deity, within an ornate frame of foliage.
In the first place, we must observe that the universe is spherical. This is either because this shape is the most perfect of all, requiring no joins and being complete in itself; or because it is the most spacious of figures, which most suits that which is to contain and preserve all things; or even because the most perfectly finished parts of the universe—I mean the Sun, the Moon, and the stars—are seen in this shape; or because all things strive to be bounded by this form, as is apparent in drops of water and other liquid bodies, when they seek to be bounded by themselves. Copernicus is referencing the natural tendency of liquids to form droplets (surface tension) as an analogy for the "natural" shape of the cosmos. Therefore, no one should doubt that such a shape has been assigned to the heavenly bodies.

Chapter 2: That the Earth is also spherical.

A decorative woodcut initial 'T' featuring a figure and architectural elements surrounded by floral patterns.
The Earth is also spherical, since from every side it rests upon its center. In the physics of this era, the "center" was the point toward which all heavy things naturally fell. Although a perfect sphere is not immediately apparent because of the great height of mountains and the depth of valleys, these do not significantly alter the overall roundness of the Earth. This is manifest for the following reasons: for those traveling North from any location, the pole of the daily revolution The celestial pole around which the stars appear to rotate. gradually rises, while the opposite pole sinks by the same amount, and more stars in the North are seen not to set, while in the South, some stars no longer rise. Thus, Italy does not see Canopus, which is visible in Egypt. And Italy sees the last star of the River original: "fluuij stellam"; referring to the constellation Eridanus, which stretches far into the southern sky., which the colder climate of our region Copernicus is writing from Frombork (Frauenburg) in modern-day Poland. does not know. Conversely, for those traveling South, those stars rise higher, while those that are high for us sink down. Furthermore, the inclinations of the poles have everywhere the same ratio to the distances measured on the Earth, which...