SALVIATUS: I do not ask the Peripatetics, I ask Aristotle. As for the
Peripatetics, they, as humble vassals of Aristotle, would deny all the
experiments and all the observations in the world; nay, would also
refuse to see them, and would say that the universe is as Aristotle
writeth, and not as Nature will have it; for, deprived of the shield of
his authority, with what do you think they would appear in the field?
Tell me, therefore, what Aristotle himself would do.
SIMPLICIUS: To tell you the truth, I do not know how to decide which is
the lesser inconvenience.
SALVIATUS: Seeing you do not know, let us examine which would be the
more rational choice, and let us assume that Aristotle would have chosen
so. Granting with Aristotle that the universe has a spherical figure and
moveth circularly round a centre, it is reasonable to believe that the
starry orbs move round the centre of the universe or round some separate
centre?
SIMPLICIUS: I would say that it were much more reasonable to believe
that they move with the universe round the centre of the universe.
SALVIATUS: But they move round the sun and not round the earth;
therefore the sun and not the earth is the centre of the universe.
SIMPLICIUS: Whence, then, do you argue that it is the sun and not the
earth that is the centre of the planetary revolutions?
SALVIATUS: I infer that the earth is not the centre of the planetary
revolutions because the planets are at different times at very different
distances from the earth. For instance, Venus, when it is farthest off,
is six times more remote from us than when it is nearest, and Mars rises
almost eight times as high at one time as at another.
SIMPLICIUS: And what are the signs that the planets revolve round the
sun as centre?
SALVIATUS: We find that the three superior planets--Mars, Jupiter, and
Saturn--are always nearest to the earth when they are in opposition to
the sun, and always farthest off when they are in conjunction; and so
great is this approximation and recession that Mars, when near, appears
very nearly sixty times greater than when remote. Venus and Mercury also
certainly revolve round the sun, since they never move far from it, and
appear now above and now below it.
SAGREDUS: I expect that more wonderful things depend on the annual
revolution than upon the diurnal rotation of the earth.
SALVIATUS: YOU do not err therein. The effect of the diurnal rotation of
the earth is to make the universe seem to rotate in the opposite
direction; but the annual motion complicates the particular motions of
all the planets. But to return to my proposition. I affirm that the
centre of the celestial convolutions of the five planets--Saturn,
Jupiter, Mars, Venus, and Mercury, and likewise of the earth--is the
sun.
As for the moon, it goes round the earth, and yet does not cease to go
round the sun with the earth. It being true, then, that the five planets
do move about the sun as a centre, rest seems with so much more reason
to belong to the said sun than to the earth, inasmuch as in a movable
sphere it is more reasonable that the centre stand still than any place
remote from the centre.
To the earth, therefore, may a yearly revolution be assigned, leaving
the sun at rest. And if that be so, it follows that the diurnal motion
likewise belongs to the earth; for if the sun stood still and the earth
did not rotate, the year would consist of six months of day and six
months of night. You may consider, likewise, how, in conformity with
this scheme, the precipitate motion of twenty-four hours is taken away
from the universe; and how the fixed stars, which are so many suns, are
made, like our sun, to enjoy perpetual rest.
SAGREDUS: The scheme is simple and satisfactory; but, tell me, how is it
that Pythagoras and Copernicus, who first brought it forward, could make
so few converts?
SALVIATUS: If you know what frivolous reasons serve to make the vulgar,
contumacious and indisposed to hearken, you would not wonder at the
paucity of converts. The number of thick skulls is infinite, and we need
neither record their follies nor endeavour to interest them in subtle
and sublime ideas. No demonstrations can enlighten stupid brains.
My wonder, Sagredus, is different from yours. You wonder that so few are
believers in the Pythagorean hypothesis; I wonder that there are any to
embrace it. Nor can I sufficiently admire the super-eminence of those
men's wits that have received and held it to be true, and with the
sprightliness of their judgments have offered such violence to their
senses that they have been able to prefer that which their reason
asserted to that which sensible experience manifested. I cannot find any
bounds for my admiration how that reason was able, in Aristarchus and
Copernicus, to commit such a rape upon their senses, as in despite
thereof to make herself mistress of their credulity.
SAGREDUS: Will there still be strong opposition to the Copernican
system?
SALVIATUS: Undoubtedly; for there are evident and sensible facts to
oppose it, requiring a sense more sublime than the common and vulgar
senses to assist reason.
SAGREDUS: Let us, then, join battle with those antagonistic facts.
SALVIATUS: I am ready. In the first place, Mars himself charges hotly
against the truth of the Copernican system. According to the Copernican
system, that planet should appear sixty times as large when at its
nearest as when at its farthest; but this diversity of magnitude is not
to be seen. The same difficulty is seen in the case of Venus. Further,
if Venus be dark, and shine only with reflected light, like the moon, it
should show lunar phases; but these do not appear.
Further, again, the moon prevents the whole order of the Copernican
system by revolving round the earth instead of round the sun. And there
are other serious and curious difficulties admitted by Copernicus
himself. But even the three great difficulties I have named are not
real. As a matter of fact, Mars and Venus do vary in magnitude as
required by theory, and Venus does change its shape exactly like the
moon.
SAGREDUS: But how came this to be concealed from Copernicus and revealed
to you?