On the Revolutions of the Heavenly Spheres

ON THE REVOLUTIONS, BOOK I.

[if the water] were an eighth part Copernicus is responding to a traditional scholastic theory that the four elements exist in a 10:1 ratio, meaning water would be ten times the volume of earth and therefore should completely submerge it., its diameter could not be greater than the distance from the center to the surface of the waters; so far is it from the case that there is ten times more water than earth. Furthermore, that there is no difference between the earth’s center of gravity and its center of geometric magnitude can be understood from this: the convexity of the land rising out of the ocean does not swell upward in a continuous, ever-increasing heap. If it did, it would push back the sea waters as much as possible and would never allow internal seas or such vast gulfs to break through. Again, the depth of the abyss would not cease to increase as one moved away from the ocean shore; consequently, neither islands, nor reefs, nor any bit of land would be encountered by sailors who had traveled far out.

Now, it is well known that between the Egyptian Sea The Mediterranean and the Arabian Gulf The Red Sea, barely fifteen stadia original: "stadia" — a classical unit of distance; 15 stadia is roughly 1.7 miles, though Copernicus is likely referring to the narrowest part of the Isthmus of Suez. remain in nearly the middle of the world. Conversely, Ptolemy in his Cosmography Ptolemy was a 2nd-century Greco-Egyptian geographer whose work was the standard for over a millennium. extended the habitable land as far as the middle circle The Equator, leaving beyond it unknown land. There, more recent explorers have added Cathay Northern China and very extensive regions even up to 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 for Amerigo Vespucci; Copernicus is writing only a few decades after its "discovery.", named after the captain of the ships who discovered it. Because of its as-yet unknown size, they consider it to be another world. Besides this, there are many other previously unknown islands. We should therefore no longer wonder that there are Antipodes People living on the opposite side of the globe or Antichthones literally "opposite-earthers". Indeed, geometric reasoning forces us to believe that America is located diametrically opposite to India on the Ganges because of its position.

From all these facts, finally, I think it is manifest that the earth and water together lean upon a single center of gravity, and that this center is the same as the center of the earth's magnitude. Since the earth is heavier, its gaping parts are filled with water; and therefore, there is a small amount of water in comparison to the earth, even though more water may perhaps appear on the surface. For the earth, along with the waters surrounding it, must necessarily have the kind of shape that its shadow reveals: for during an eclipse of the Moon, the earth creates a darkening with the circumference of a perfect circle.

The earth, therefore, is not flat, as Empedocles and Anaximenes thought; nor drum-shaped, as Leucippus held; nor bowl-shaped, as Heraclitus believed; nor hollow in some other way, as Democritus suggested. Nor, again, is it cylindrical, as Anaximander proposed; nor does it extend downward to an infinite thickness with its roots at the bottom, as Xenophanes thought. Instead, it is a perfect roundness, as the Philosophers Referring generally to the Aristotelian/Platonic tradition of the "Physici" or natural philosophers. believe.