The Rise of Natural Philosophy, Scientific Revolution, and the Enlightenment (^) ‹ 105
Copernicus’s proposal alarmed Church authorities for several reasons:
• It questioned the authority of the Aristotelian tradition on which scholasticism relied.
• It contradicted the physical principles that served as the foundation of physics.
• It destroyed the theological coherence of the cosmos.
• It required the Church to admit it had been in error.
Shortly before Copernicus’s death in 1543, the Church allowed his theory to be published
in a work titled De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Bodies),
provided that it be accompanied by a preface stating that the theory was only being presented as
a useful hypothetical model, not as a true account of the physical nature of the cosmos. Because
Copernicus’s great work was written in Latin (which was the language of educated scholars) and
because it was a highly technical work, its publication created no great stir. But slowly, over the
course of the next 70 years, Copernicanism (as the theory came to be known) spread in circles
of men educated both within the Church and in the newer academies and societies.
Kepler’s Laws
By the seventeenth century, a loose network of Copernicans championed the new world
view as part of a new empirical and mathematical approach to the study of the natural
world. One was a German mathematician working in the Hermetic and Neoplatonic tradi-
tions, Johannes Kepler, who devoted his life to finding the mathematical harmonies of the
cosmos. Between 1609 and 1619, he developed three laws of planetary motion that would
come to be known as Kepler’s laws:- The first law broke with the tradition of conceiving of the planets as moving in uniform
circles, suggesting that the planetary orbits took the form of an ellipse, with the sun as
one of their foci. - The second law abandoned the notion that planetary motion was uniform and asserted
that a planet’s velocity varied according to its distances from the sun, sweeping out equal
areas in equal times. - The third law gave a mathematical description for the physical relationship between the
planets and the sun, asserting that the squares of the orbital periods of the planets are in
the same ratio as the cubes of their average distance from the sun.
Galileo and the Value of Empirical Knowledge
Although Kepler worked in obscurity, Galileo Galilei was an ambitious self-promoter.
Dubbing himself a “mathematical philosopher,” Galileo championed an approach to know-
ing the natural world that emphasized the need to apply reason to observational and math-
ematical data. Also, following the English philosopher Francis Bacon, Galileo combined his
approach with an appeal to the practical and pragmatic value of such knowledge.
Having dismantled and analyzed a spyglass he bought from Dutch merchants, Galileo
drew up schematics for a larger, more powerful version. The result was the world’s first tel-
escope, and Galileo immediately turned his new invention on the heavens. In 1610, Galileo
published his findings in a pamphlet titled Sidereus Nuncius (The Starry Messenger). There,
he announced several discoveries, which, although they did not explicitly promote the
Copernican theory, did implicitly call into question the veracity of the Aristotelian model.
These discoveries included the following:15_Bartolini_Ch15_099-118.indd 105 27/04/18 1:54 PM