Controversy over the Comets
Systems of the Universe
Earth-centered models of the universe, geocentric, and sun-centered models of the universe, heliocentric, equally predicted the position and movement of the planets. Given that the competing systems produced identical planetary predictions, astronomers searched for other kinds of observations that might decide between them. Comets seemed to cross through multiple spheres. The spheres of Mars and the Sun seemed likely to intersect. Several systems predicted that Venus might show phases. The Copernican system predicted stellar parallax, that stars should appear to slightly shift in position, which was not observed. Definitive evidence that could decide the true system of the universe proved elusive.
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Three Jesuit Portraits: Loyola, Bellarmine, Clavius |
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Tycho Brahe prints: Portrait (6); Copenhagen (7); Hven (8); Gardens (9); Uraniborg (10); Architectural plan (11) |
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New Brandenburg Ephemerides of the Celestial Motions Origanus, David (1609) |
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Ecstatic Journey through the Heavens Kircher, Athanasius (1660) Six chief world systems were debated in Galileo’s world: • Ptolemaic: All planets revolve around the central Earth. Geocentric. • Platonic: Like the Ptolemaic, except switches the positions of Venus and Mercury. Geocentric. • Cappellan or Egyptian: Venus and Mercury revolve around the Sun. |
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Principles of Astronomy Naibod, Valentin (1580) This Copernican cosmic section, the first published in Italy, appears in a sympathetic account, known to Tycho and to Kepler, which may have influenced Galileo. Naibod was a professor of mathematics at Padua who likely studied with Erasmus Reinhold in Wittenberg. |
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Commentary on the Sphere of Sacrobosco Clavius, Christoph (1570) Clavius taught mathematical astronomy in the Rome College (Collegio Romano), the leading Jesuit university in Rome. Aristotle did not emphasize mathematics, but Clavius’ lifelong work established mathematics and astronomy as essential areas of study for Jesuit schools. |
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Galileo shows the satellites of Jupiter to the Venetian Senators Figuier, Louis (1870) Galileo offered first-hand telescopic demonstrations to influential colleagues and supporters across Venice and Tuscany. In early 1611, Galileo visited Rome, invited by Clavius and the Jesuits. |
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Robert Bellarmine, portrait Robert, Bellarmine Robert Bellarmine was a prominent Jesuit theologian at the time of Galileo. Before several remarkable novas appeared, and 40 years before Galileo’s evidence of sunspots, Bellarmine had already come to believe on the basis of biblical authority that the heavens are not eternal but corruptible. |
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Instruments for the Restoration of Astronomy Brahe, Tycho (1602) For two decades, Tycho and his assistants at Uraniborg produced thousands of astronomical observations of unprecedented quality. Tycho’s large-scale observing instruments, together with sophisticated new error correction techniques, increased observational precision by a factor of twenty. |
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Astronomical Letters Brahe, Tycho (1596) In this work, Tycho explained two problems posed for Copernicus by the absence of stellar parallax: 1. Due to the annual movement of the Earth around the Sun, one would expect to see stars appear to shift in position. This parallax evaded detection, even at Uraniborg. 2. |
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Complete Works Brahe, Tycho (1648) In De mundi aetherei (1588), Tycho reported that the comet of 1577 displayed no detectable parallax and thus moved, contrary to Aristotle, in the regions of the heavens beyond the Moon, passing through multiple celestial spheres. The ancient solid spheres melted. |
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The World of Jupiter Mayr, Simon (1614) With a telescope, Mayr observed the four satellites of Jupiter, accurately determining their periods of revolution. He named them Europa, Io, Ganymede and Callisto, names which are still used today. In this work Mayr also considered Tycho’s objection to Copernicus based upon star sizes. |
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Sphere of the Universe Biancani, Giuseppe (1620) After Clavius, Jesuits tended to adopt Tycho’s system. Biancani’s Sphaera replaced Clavius as the standard introduction to astronomy in many Jesuit colleges. Biancani favored Tycho’s system, which preserved the mathematical elegance of Copernicus and accommodated the absence of stellar parallax... |
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Astronomical Foundation Ursus, Nicolaus Reimarus (1588) The cosmological system of Ursus is similar to that of Tycho Brahe. Both place the Earth in the center, and set the other planets revolving around the Sun. For Ursus, in contrast to Tycho, the Earth rotates around its axis once a day, allowing the sphere of stars to stand still. |
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The New Almagest, part 1 Riccioli, Giambattista (1651) The frontispiece of Riccioli’s treatise depicts not two, but three major systems of the world. The Ptolemaic system rests discarded (lower right corner) because of the phases of Venus and Mercury (upper left corner). All-seeing Argus looks on, holding a telescope. |
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The New Almagest, part 2 Riccioli, Giambattista (1651) The frontispiece of Riccioli’s treatise depicts not two, but three major systems of the world. The Ptolemaic system rests discarded (lower right corner) because of the phases of Venus and Mercury (upper left corner). All-seeing Argus looks on, holding a telescope. |
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The Three Spheres Beati, Gabriele (1662) Which of Kircher’s six world systems are compatible with Beati’s cosmic section? Despite Galileo’s rhetorical attempt to cast cosmological debate as a choice between two chief world systems, Beati’s cosmic section is neither Ptolemaic nor Copernican. |
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The Use of Celestial and Terrestrial Globes, and Spheres, according to the different Systems of the World Bion, Nicolas (1710) Even today, while we adopt the Copernican system, we still teach observational astronomy and navigation by the stars using the traditional geocentric instruments: nocturnal dials, celestial globes, and armillary spheres. |
