In a time of significant change and upheaval throughout European society, Kepler was not alone in his pursuit of concepts and theories that more accurately described the world he observed. A scientist who shared Kepler’s vision of defending the Copernican system from its many critics was Galileo Galilei, an Italian astronomer who in the popular conception has all but eclipsed Kepler in not only scientific advancements of the early 17th century, but also through his notoriety for dissenting against the oppressive papacy in his ardent defense of the newly-conceived astronomical model. While both astronomers were champions of empirical observation, and even collaborated on several occasions in order to support each other’s findings, the two figures had many differences in both their methods and observations that highlighted the underlying goals that each sought to achieve. Kepler sought an abstract ideal, while Galileo rooted his methods in observation of the physical as he strived to rationalize the world around him, not just the heavenly bodies. In this sense, Galileo can be seen more as a “hard science” type, while Kepler’s self-imposed moniker of “astronomer-priest” remains appropriate. Their contributions to astronomy and physics remain the basis for many scientific discoveries today, but their motivations and methods for reaching those conclusions differed greatly at times.
Galileo became known as a great scientist not only through his arguments and writings, but his technological innovations that aided him in making revolutionary discoveries as well as paving the way for future scientists to make use of his tools to better observe the world around them. In 1608, Galileo acquired a telescope from Hans Lippershey, and the following year improved upon it to invent the refracting telescope, or the Galilean telescope. As evidenced by the name (not awarded by Galileo himself) this telescope excelled at observing distant objects on earth due to its increased magnification. Galileo continued to develop this technology until it was strong enough to observe the heavenly bodies, a monumental leap in astronomy. Galileo is also credited with developing an improved compass for military and maritime navigation, a modernized pendulum clock, and the thermometer. Though Kepler made use of the Galilean telescope, he failed to produce any original inventions of his own.
The most prominent example of ideological overlap between these two great scientists is the vehement defense of Copernicus’ heliocentric model against religious officials and scientists alike who resisted the idea. The first substantive defense of Copernicus came with Galileo’s 1609 work Sidereus Nuncius, or “Messenger of the Stars.” In this work Galileo includes observations of the moon, the moons of Jupiter, and various constellations and was the first work published that made use of a telescope to collect data. This work was corroborated the following year by Kepler who could only do so after gaining access to a telescope of his own. The work became the basis of Galileo’s defense for heliocentrism against the Catholic church. Though any substantive persecution would not come for Galileo until two decades later, he continued to defend heliocentrism against the church’s wishes for the remainder of his life. In 1632 he published a work, “The Dialogue Concerning Two Chief World Systems,” which pitted Copernicus against Ptolemy, and irrefutably took a stance for Copernicus, as he pointed out the geocentric model was full of flaws. The book’s tone, which Pope Urban VIII perceived as making a mockery of the church and its views, gave the church enough leverage to convict Galileo of heresy and place him under house arrest for the remainder of his life. Though Galileo never meant to make a mockery of the Pope, who he had been on bad terms with for almost the entirety of his career, he refused to back down on his stance advocating for the Copernican system. Although they worked together in the battle to defend Copernicus, Galileo and Kepler did not find common ground on every facet of their discoveries. No evidence is found in Galileo’s works that support Kepler’s theory of elliptical orbits, even though there was a substantive justification. Tycho Brahe, Kepler’s teacher, had proposed a model for the solar system that combined the Copernican and Ptolemaic system, and urged Kepler to continue developing his work after his death. Kepler however, forewent Brahe’s model and built on Copernicus in his own way first by observing the orbit of Mars for seven years. The culmination of his observations, contained within the Astronomia Nova, was published the same year as Galileo’s landmark work, and similarly defended Copernicus. The important distinction Kepler made however was that he did not acknowledge the heliocentric model as reality, and instead used it as a model in itself to describe the movement and velocities of the planets. Ultimately, Kepler concluded that “the sun is the engine that moves the planets,” affirming his position. Why Kepler did not receive the same response that Galileo did is not surprising. Kepler was Lutheran, and while he was excommunicated by the Catholic church, it did not affect him as greatly as it did Galileo, whose proximity to the Vatican and Catholic status earned him much more notoriety among the papacy. Though a religious man like Kepler, Galileo had no abstract ideals about his scientific discoveries and innovations – he saw the discoveries themselves as an end and did not derive any significant spiritual meaning from it. To Galileo, Platonic ideals like harmony that Kepler sought only served to complicate the meaning behind scientific discoveries. Though he abstained from including religion in his scientific life, Galileo himself became a scientific martyr of sorts for his iconic stance against the church.
Bibliography
Boner, Patrick J. Kepler’s cosmological synthesis: astrology, mechanism, and the soul. Koninklijke Brill 2013: Leiden, Netherlands. Web.
Kepler, Johannes. Astronomia nova (New Astronomy). 1609
Galilei, Galileo. “Dialogue Concerning the Two Chief World Systems.” 1632.
Galilei, Galileo. Sidereus Nuncius. 1609.
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