Galilei, Galileo Dialogues on two world systems 1661, tr. Salusbury, Thomas

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without encompassing the Earth; about the same Sun you make
the three superiour Planets Mars, Jupiter, and Saturn, to move,
comprehending the Earth within their circles. The Moon in the
next place can move in no other manner than about the Earth,
without taking in the Sun, and in all these motions you agree also
with the same Copernicus. There remains now three things to be
decided between the Sun, the Earth, and fixed stars, namely,

Rest, which seemeth to belong to the Earth; the annual motion
under the Zodiack, which appeareth to pertain to the Sun; and the
diurnal motion, which seems to belong to the Starry Sphere, and
to be by that imparted to all the rest of the Universe, the Earth
excepted, And it being true that all the Orbs of the Planets, I

mean of Mercury, Venus, Mars, Jupiter, and Saturn, do move
about the Sun as their centre; rest seemeth with so much more
reason to belong to the said Sun, than to the Earth, in as much
as in a moveable Sphere, it is more reasonable that the centre
stand still, than any other place remote from the said centre; to
the Earth therefore, which is constituted in the midst of move­
able parts of the Universe, I mean between Venus and Mars, one
of which maketh its revolution in nine moneths, and the other in
two years, may the motion of a year very commodiously be as­

signed, leaving rest to the Sun. And if that be so, it followeth
of necessary consequence, that likewise the diurnal motion be­
longeth to the Earth; for, if the Sun standing still, the Earth
should not revolve about its self, but have onely the annual mo­
tion about the Sun, our year would be no other than one day and
one night, that is six moneths of day, and six moneths of night,
as hath already been said. You may consider withal how commo­
diously the precipitate motion of 24 hours is taken away from
the Universe, and the fixed stars that are so many Suns, are made
in conformity to our Sun to enjoy a perpetual rest. You see more­
over what facility one meets with in this rough draught to render
the reason of so great appearances in the Celestial bodies.

Rest, the annual
motion and the di­
urnal ought to be
distributed be­
twixt the Sun,
Earth, and Fir­
mament.

In a moveable
sphere, it seemeth
more veasonable
that its centre be
stable, than any o­
ther of its parts.

Granting to the
Earth the annual,
it must of necessity
also have the diur­
nal motion assign­
ed to it.

SAGR. I very well perceive that facility, but as you from this
simplicity collect great probabilities for the truth of that System,
others haply could make thence contrary deductions; doubting,
not without reason, why that same being the ancient Systeme of
Pythagoreans, and so well accommodated to the Phænomena,
hath in the succession of so many thousand years had so few fol­
lowers, and hath been even by Aristotle himself refuted, and
since that Copernicus himself hath had no better fortune.

SALV. If you had at any time been assaulted, as I have been,
many and many a time, with the relation of such kind of frivolous
reasons, as serve to make the vulgar contumacious, and difficult to
be perswaded to hearken, (I will not say to consent) to this novel­