On the Revolutions of the Heavenly Spheres

...but if it were an eighth, its diameter could not be greater than the distance from the center to the surface of the waters. So far is it from the truth that the water is ten times larger Copernicus is refuting a common medieval belief, often attributed to a misunderstanding of Aristotle or Esdras, that water was ten times more voluminous than land.. That there is no difference between the center of gravity of the Earth and the center of its magnitude can be understood from this: the convexity of the land spreading out from the ocean does not continuously swell as it moves further away; otherwise, it would block the sea waters as much as possible and would not allow internal seas or such vast gulfs to break through. Conversely, the depth of the abyss would not stop increasing from the shore of the ocean, so that no island, reef, or any bit of land would be encountered by those sailing further out.

Now, indeed, it is well known that between the Egyptian Sea The Mediterranean and the Arabian Gulf The Red Sea, barely fifteen stades original: "stadia"; an ancient unit of length, roughly 600 feet, though the exact length varied. Copernicus uses it to describe the narrow Isthmus of Suez. remain, located nearly in the middle of the world. On the other hand, Ptolemy in his Cosmography Referring to the Geography of Claudius Ptolemy, the standard geographical text of the time. extended the habitable land as far as the middle circle, leaving beyond it unknown land where more recent authors have added Cathay original: "Cathagyam"; an archaic name for Northern China. and most extensive regions as far as 60 degrees of longitude. Thus, the land is now inhabited over a greater longitude than what remains for the ocean.

This will be even clearer if we add the islands found in our own time under the Princes of Spain and Portugal, and especially America Named after Amerigo Vespucci. This is a very early mention of America in a scientific text (published 1543)., named after the discoverer who was the captain of the ships. Because of its size, which is still not fully known, they think it is another world, besides many other islands previously unknown. Therefore, we should not be surprised that there are Antipodes or Antichthones People who live on the opposite side of the Earth.. For geometric reasoning forces us to believe that America itself is diametrically opposite to India near the Ganges.

From all these facts, I think it is manifest that the land and the water together rest upon a single center of gravity, and that this is no different from the center of the Earth’s magnitude. Since the earth is heavier, its gaping parts are filled with water; and therefore, compared to the earth, the amount of water is modest, even though more water may perhaps appear on the surface. For it is necessary that the Earth, along with its surrounding waters, has the same shape that its shadow shows: for it produces a lunar eclipse with the arcs of a perfect circle.

Therefore, the Earth is not flat, as Empedocles and Anaximenes thought; nor drum-shaped original: "Tympanoides", as Leucippus; nor boat-shaped original: "Scaphoides", as Heraclitus; nor hollow in some other way, as Democritus. Nor, again, is it cylinder-shaped original: "Cylindroides" as Anaximander; nor is it an infinite thickness extending downward from its lower part, as Xenophanes; but it is of an absolute roundness, as the Philosophers hold.