The illustration is the frontispiece
from Almagestum Novum (Bologna, 1651) by the Jesuit astronomer Giambattista
In the decades following the condemnation
of Galileo, Riccioli was an ardent critic of the Copernican theory.
He conceded that Galileo’s discovery of the phases of Venus had refuted
the Ptolemaic system but insisted that Tycho Brahe’s system, in which the
earth does not move, captured all the observational and mathematical advantages
of the Copernican theory with none of its physical and theological disadvantages.
Riccioli’s book (whose title is a deliberate reference to the “old” Almagest
of Ptolemy, now discredited) gives an exhaustive survey of arguments for
and against the Copernican theory, and concludes that Tycho Brahe’s system
(modified slightly by Riccioli) is more plausible.
frontispiece shows his own version of the Tychonic system weighing more
heavily in the scales of evidence than its Copernican rival. In Riccioli’s
variant, Mercury, Venus, and Mars are satellites of the Sun but, unlike
Brahe’s original scheme, Jupiter and Saturn are centered on the Earth.
The figure holding the scales and the armillary sphere combines features
of Urania (the muse of astronomy) and Astraea (the goddess of justice).
On the left is hundred-eyed Argus, observing the Sun through a telescope
held to an eye on his knee. His words allude to Psalm 8, verse 3:
“When I consider thy heavens, the work of thy fingers....” At the
bottom lies the Ptolemy with his discarded system. Ptolemy rests
his hand on the coat of arms of the Prince of Monaco (to whom the Almagestum
Novum was dedicated) magnanimously acknowledging the correction of
his errors. At the top are depicted recent astronomical discoveries
of the seventeenth century: Mercury and Venus displaying crescent phases;
Saturn with two “handles”—this was prior to Huyghens’s ring hypothesis;
Jupiter with four moons and two bands parallel to its equator (a feature
first noted by Riccioli); a heavily-cratered Moon and what appears to be
a meteorite soaring through the heavens like a spotted cannonball.
In the center at the top is the Hebrew word Yah-Veh and a reference
to the Wisdom of Solomon 11, verse 20: “But thou hast ordered all things
by measure and number and weight.” On the left and right are quotations
from Psalm 19, verse 2: “Day unto day uttereth speech, and night unto night
book had no effect on the debate over the Copernican theory—by the middle
of the seventeenth century, almost all scientists and astronomers were
Copernicans—it illustrates one of the classic cases of theory choice in
the history of science.