NICHOLAS COPERNICUS

...occupies a space that, compared to their length, is rendered incomparable to the senses, in the manner demonstrated in the Optics Referring to the mathematical study of light and perspective, likely referencing the works of Euclid or Ptolemy.. By this argument, it is clear enough that the heavens are immense in comparison to the Earth and present the appearance of an infinite magnitude; but by the estimation of the senses, the Earth is to the heavens as a point is to a body, and as the finite is to the infinite in magnitude. Nothing else seems to have been demonstrated.

Nor does it follow that the Earth must rest in the middle of the universe. Indeed, we should wonder even more if such a vast world revolved in the space of twenty-four hours rather than its smallest part, which is the Earth.

For as they say the center is immobile and the things closest to the center move the least, this does not prove that the Earth rests in the middle of the universe. It is no different than if you were to say that the sky turns while the poles rest, and the things closest to the poles move the least. Just as Cynosura The constellation Ursa Minor (the Little Bear), often used to refer to the North Star. is seen to move much slower than Aquila The Eagle constellation. or Canicula The "Little Dog" star (Procyon) or sometimes the "Dog Star" (Sirius). because it describes a smaller circle near the pole, since they all belong to a single sphere. The mobility of that sphere, which fades away at its axis, does not allow all its parts an equal motion; yet the revolution of the whole brings them back in an equality of time, though not in an equality of distance.

The logic of the argument rests on this: as if the Earth were a part of the celestial sphere, sharing its nature and motion, so that being close to the center, it would move very little. Therefore, as a body itself and not the center, it will also move, covering similar celestial arcs as the heavens in the same time, though they be smaller.

How false this is, is clearer than light. For it would be necessary for it to be noon always in one place and midnight in another, so that daily sunrises and sunsets could not occur, since the motion of the whole and the part would be one and inseparable.

But for those things which are distinguished by a difference in nature, the logic is far different; things enclosed in a smaller circuit revolve faster than those tracing a larger circle. Thus, Saturn, the highest of the wandering stars planets, completes its revolution in thirty years, and the Moon, which is undoubtedly closest to the Earth, completes its circuit in a month. Finally, the Earth itself will be thought to circle through the space of a day and a night.

Thus, the same doubt about the daily revolution arises again. Moreover, its location is still sought and remains even less certain from the things said above. For that demonstration provides nothing other than the indefinite magnitude of the heavens relative to the Earth. But how far this immensity extends is not at all clear.