Jefferson B, Fourth Floor 02 Nov 2018 Contributed Papers Session
Physical Sciences 15:45 - 17:45

The Controversy over the Comets of 1618: Reflections for the 400th Anniversary
15:45 - 16:15

2018 marks the 400th anniversary of the controversy over the comets between Orazio Grassi and Galileo Galilei. The appearance of three comets in 1618 initiated a scientific and polemical exchange between the two. A central issue of the debate was the location of the comets, either above or below the lunar sphere, and the role of observational evidence in contemporary cosmology and natural philosophy. The debate over the comets had implications for the substance of the heavens, the existence of change and corruption in the celestial region, as well as the utility of mathematical demonstrations for natural philosophy. However, historians of science have not fully explored the religious, political and scientific import of this episode in the history of science. The most glaring omission in the historiography is the ease with which historians of science have glossed over Grassi’s final response the Galileo, his Ratio ponderum librae simbellae (1626 Paris, 1627 Rome), for example Drake and O’Malley excluded any translation of Grassi’s last response to Galileo and instead chose to include a translation of Kepler’s Hyperaspistes in their 1960 publication The Controversy on the Comets of 1618. In this paper I will explore the connections between the scientific, religious and political aspects of the controversy with special emphasis on its import for the history of Jesuit science and the role of the Society of Jesus in the development of early modern mathematics.and natural philosophy.

Comets and Courts in Early Modern Germany
16:15 - 16:45

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Soon after a bright light blazed in the sky in 1604, Johannes Krabbe declared that he had accurately predicted it down to the month and year. From the royal court at Wolfenbüttel, Krabbe measured the magnitude and motion of the comet “beyond the sphere of Saturn.” Krabbe represented a growing number of astronomers who projected the principle of parallax to the heavens, abolishing the solid celestial spheres and countering the cometary theory of Aristotle.

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In the following presentation, I examine the career and cosmology of Krabbe, including his conflict with Johannes Kepler, who defined the comet as a new star deprived entirely of parallax. While Krabbe considered novel ideas about the physical nature of the heavens, his account reflected a relatively standard view of astrology across Lutheran Germany. Despite uncertainty in the science of the stars, Krabbe held out hope for the future. “Wise astrologers will one day determine the causes for why comets appear,” he concluded.

Kepler's Rejection of Circularity, as shown on the Crucial Folium P356 of the Mars Notebook
16:45 - 17:15

In early April of 1602, Kepler took what was to prove a fateful step in working out his Mars theory. He had already formulated a prototype of the “area law,” which we now know as his Second Law. This, he thought, would be a more accurate replacement for Ptolemy’s equant, which he saw as a stand-in for a dynamic principle. But, he wondered, would it really be more accurate than Ptolemy’s geometrical model?

To answer this question, Kepler conducted a simple and methodical test, comparing positions and times generated using the area law on a circular orbit with the empirically correct positions and times. The test covers two sides of a single sheet of paper (folium P356 of the Mars Notebook), and by the end of the inquiry Kepler had concluded that the test failed for a circular orbit, but would succeed if the orbit were made very slightly oval. Rather than abandoning the area law, Kepler took the radical step of developing the physics and geometry of the orbit, now presumed to be some kind of oval.

Using photographs of the manuscript page, Kepler’s reasoning will be summarized step-by-step. We will see, as if looking over his shoulder, how he arrived at the crucial discovery of the nine arc-minute discrepancy that led to the abandonment of circularity in planetary theory.

Transmutations of Light: Phosphors in the Early Eighteenth Century
17:15 - 17:45

In 1700 Johann Bernoulli (1667-1748) brought barometric light under control with his 'new phosphor'. It initiated a wave of inquiries that resulted, among other things, in the development of the first electrical engines. Bernoulli's apparatus was just one instance of phosphor at that time. Light-bearers attracted wide interest of early modern inquirers: stones, animals, the new substance created from urine, the luminescence of vacuum, or the bright light of foci. These phosphors indicated new conceptions of light as a reactive substance that could be operated and employed to create material transformations. In this way, light became the heart of inquiries into matter and forces that bring together early Enlightenment developments in experimental philosophy. Modern disciplines tend to comminute the historiography of early modern natural philosophy. To overcome this, I approach the history of phosphors from the perspective of early-eighteenth-century protagonists like Bernoulli, Gottfried Wilhelm Leibniz (1646-1716), Wilhelm Homberg (1652-1715), Daniël Gabriël Fahrenheit (1686-1736).


Speakers
University of Twente/Vrije Universiteit
University of Oklahoma
University of Oklahoma
St. John's College, Santa Fe
Moderators
Attendees

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