Galilei, Galileo, The systems of the world, 1661

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SALV. I am ready to ſerve you. You have already ſeen me
draw the form of the Copernican Syſteme; againſt the truth of

which Mars himſelf, in the firſt place, makes an hot charge; who, in
caſe it were true, that its diſtances from the earth ſhould ſo much
vary, as that from the leaſt diſtance to the greateſt, there were
twice as much difference, as from the earth to the Sun; it would be
neceſſary, that when it is neareſt unto us, its diſcus would ſhew
more than 60. times bigger than it ſeems, when it is fartheſt from
us; nevertheleſs that diverſity of apparent magnitude is not to be
ſeen, nay in its oppoſition with the Sun, when its neareſt to the
Earth, it doth not ſhew ſo much as quadruple and quintuple in
bigneſs, to what it is, when towards the conjunction it cometh to
be occulted under the Suns rayes.
Another and greater difficulty
doth Venus exhibit; For if revolving about the Sun, as Copernicus

affirmeth, it were one while above, & another while below the ſame,
receding and approaching to us ſo much as the Diameter of the
cle deſcribed would be, at ſuch time as it ſhould be below the Sun,
and neareſt to us, its diſcus would ſhew little leſs than 40 times
ger than when it is above the Sun, near to its other conjunction; yet
nevertheleſſe, the difference is almoſt imperceptible Let us add

other difficulty, that in caſe the body of Venus be of it ſelf dark, and
onely ſhineth as the Moon, by the illumination of the Sun, which
ſeemeth moſt reaſonable; it would ſhew forked or horned at ſuch
time as it is under the Sun, as the Moon doth when ſhe is in like
manner near the Sun; an accident that is not to be diſcovered in
her.
Whereupon Copernicus affirmeth, that either ſhe is light of

her ſelf, or elſe that her ſubſtance is of ſuch a nature, that it can
imbue the Solar light, and tranſmit the ſame through all its whole
depth, ſo as to be able to appear to us alwayes ſhining; and in this
manner Copernicus excuſeth the not changing figure in Venus: but
of her ſmall variation of Magnitude, he maketh no mention at all;

and much leſs of Mars than was needful; I believe as being
ble ſo well as he deſired to ſalve a Phænomenon ſo contrary to his
Hypotheſis, and yet being convinced by ſo many other occurrences
and reaſons he maintained, and held the ſame Hypotheſis to be true.
Beſides theſe things, to make the Planets, together with the Earth,
to move above the Sun as the Centre of their converſions, and the

Moon onely to break that order, and to have a motion by it ſelf
about the earth; and to make both her, the Earth, and the whole
Elementary Sphere, to move all together about the Sun in a year,
this ſeemeth to pervert the order of this Syſteme, which rendreth
it unlikely and falſe.
Theſe are thoſe difficulties that make me
wonder how Aristarchus and Copernicus, who muſt needs have
ſerved them, not having been able for all that to ſalve them, have
yet notwithſtanding by other admirable occurrences been induced

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