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. Jupiter[4] completes its smaller course in
twelve years, Mars in two; the moon performs its much smaller
revolution within a month. Just as clearly in the Medicean stars,
we see that the one nearest Jupiter completes its revolution in a
very short time--about forty-two hours; the next in about three
and one-half days, the third in seven, and the most distant one
in sixteen days. This rule, which is followed throughout, will
still remain if we ascribe the twenty-four-hourly motion to a
rotation of the earth. If, however, the earth is left motionless,
we must go first from the very short rule of the moon to ever
greater ones--to the two-yearly rule of Mars, from that to the
twelve-yearly one of Jupiter, from here to the thirty-yearly one
of Saturn, and then suddenly to an incomparably greater sphere,
to which also we must ascribe a complete rotation in twenty-four
hours. If, however, we assume a motion of the earth, the rapidity
of the periods is very well preserved; from the slowest sphere of