The difficulty is, however, doubled, inasmuch as a second very important problem presents itself.

If, namely, that powerful motion is ascribed to the heavens, it is absolutely necessary to regard it as opposed to the individual motion of all the planets, every one of which indubitably has its own very leisurely and moderate movement from west to east.

If, on the other hand, you let the earth move about itself, this opposition of motion disappears.
"The improbability is tripled by the complete overthrow of that order which rules all the heavenly bodies in which the revolving motion is definitely established.

The greater the sphere is in such a case, so much longer is the time required for its revolution; the smaller the sphere the shorter the time.

Saturn, whose orbit surpasses those of all the planets in size, traverses it in thirty years.