The gradual acceptance of the Copernican theory of the universe

by Dorothy Stimson

Secondly, it is proved by reason. All the heavens and stars were made in man's behalf and, with other terrestrial bodies, are the servants of man to warm, light, and vivify him.

This they could not do unless in moving they applied themselves by turns to different parts of the world. And it is more likely that they would apply themselves by their own movement to man and the place in which man lives, than that man should come to them by the movement of his own seat or habitation. For they are the servants of man; man is not their servant; therefore it is more probable that the heavens are moved and the earth is at rest than that the reverse is true.

Thirdly; no probable argument can be thought out from philosophy to prove that the earth is moved and the heavens are at rest. Nor can it be done by mathematics. By saying that the heavens are moved and the earth is at rest, all phenomena of the heavenly bodies can be solved. Just as in the same way in optics all can be solved by saying either that sight comes from the thing to the eye, or that rays go from the eye to the thing seen; so is it in astronomy. Therefore one ought rather to abide in the ancient and general opinion than in one received recently without justification.

Fourthly; the earth is the center of the universe; all the heavenly bodies are observed to be moved around it; therefore it itself ought to be motionless, for anything that moves, it seems, should move around or above something that is motionless.

Fifthly; if the earth is moved in a circle, either it moves that way naturally or by force, either by its own nature or by the nature of another. It is not by its own nature, for straight motion from above downward is natural to it; therefore circular motion could not be natural to it. Further, the earth is a simple body; and a simple body can not have two natural motions of distinct kinds or classes. Nor is it moved by another body; for by what is it moved? One has to say it is moved either by the sun or by some other celestial body; and this cannot be said, since either the sun or that body is said to be at rest or in motion. If it is said to be at rest, then it cannot impart movement to another. If it is said to be in motion, then it can not move the earth, because it ought to move either by a motion similar to its own or the opposite of it. It is not similar, since thus it would be observed to move neutrally as when two boats moving in the same direction, appear not to move but to be at rest. It is not the opposite motion, since nothing could give motion contrary to its own. And because Galileo seems to say, in so far as I have learned from your lordships, that the earth was moved by the sun; I prove anyway that this is not true since the movement of the sun and of the earth ought to be from contrary and distinct poles. The sun, however, can not be the cause of the other's movement because it is moved above different poles. Lastly, the earth follows the motion of no other celestial body; since if it is moved, it moves in 24 hours, and all the other celestial bodies require the space of many days, months and years. Ergo. Finally, if the earth is moved by another, its motion would be violent; but this is absurd, for no violence can be regular and perpetual.

Sixthly; even so it is declared that the earth is moved. Nevertheless, it must be admitted to this that either the planets themselves or their spheres are moved, for in no other way can the diversities of aspects among themselves be solved; nor can a reason be given why the sun does not leave the Ecliptic and the moon does; and how a planet can be stationary or retrograde, high or low,—and many other phenomena. For this reason those who said the earth moved, as Bernardus Patricius and the others said, claimed that the primum mobile, forsooth, was stationary and that the earth was moved in its place; yet they could not in the least deny that the planets themselves were moved, but admitted it. That is the reason why both ancient and modern mathematicians, aside from the motion of the primum mobile, were forced to admit and consider the peculiar movements of the planets themselves. If therefore it must be acknowledged, and it is certain, that the stars and the celestial bodies are moved; then it is more probable that all movement perceived in the universe belongs rather to the heavenly bodies than to the earth. For if movement were ascribed to all the rest, why for that same reason is not diurnal rotation ascribed rather to the primum mobile than to the earth, particularly when our senses seem to decide thus? Although one may well be mistaken, sometimes, concerning other similar movements; yet it is not probable that all ages could be at fault, or should be, about the movements of its most important objects, of course the celestial luminaries.

Seventhly; it is proved by experience. For if the earth is moved, then an arrow shot straight up on high could never fall back to the place whence it was shot, but should fall somewhere many miles away. But this is not so. Ergo.

This can be answered and is so customarily in this way: this does not follow because the air is swept along with the earth, and so, since the air which carries the arrow is turning in the same way with the earth, the arrow also is borne along equally with it, and thus returns to the same spot. This in truth is a pure evasion and a worthless answer for many reasons.

It is falsely observed that the air is moved and by the same motion as the earth. For what should move the earth? Truly, if the air is moved by the same motion as the earth, either it ought to be moved by the earth itself, or by that other which moves the earth, or by itself. It is not moved by itself; since it has another motion, the straight one of course natural to itself, and also since it has a nature, an essence and qualities all different from the nature and the essence of the earth; therefore it could not by its own nature have the same motion as that other, but of necessity ought to have a different one.

Nor is it moved by any other that may move the earth; as that which moves the earth could not at the same time and with like motion move the air. For since the air is different from the earth in essence, in both active and passive qualities, and in kind of substance, it can not receive the impelling force of the acting body, or that force applied in the same way as the earth, and so could not be moved in the same way. The virtues [of bodies] acting and of moving diversely are received by the recipients according to the diversity of their dispositions. Also it can not be moved by the earth; since if it were moved by the earth, it must be said to be moved by force, but such motion appears to be impossible. Ergo. The minor premise is proved: for if air is thus moved by the earth by force the air ought to be moved more rapidly than the earth, because air is larger [than the earth].