Tychonic system
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The Tychonic system (or Tychonian system) was a model of the solar system published by Tycho Brahe in the late 16th century which combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. The model may have been inspired by Paul Wittich, a Silesian mathematician and astronomer.[1] A similar geoheliocentric model was also earlier proposed by Nilakantha Somayaji of the Kerala school of astronomy and mathematics.[2][3]
It is essentially a geocentric model with the Earth at the center of the universe. The Sun and Moon revolve around the Earth, and the other five planets revolve around the Sun. It can be shown through a geometric argument that the motions of the planets and the Sun relative to the Earth in the Tychonic system are equivalent to the motions in the Copernican system.
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[edit] Motivation for the Tychonic system
Tycho argued that if the Earth is moving, then we should be able to detect a change in our position relative to stars (the technical term is parallax). But he was not able to detect that change in relative position, so he concluded that the Earth is not moving. In fact, our position relative to stars does change, but stars are so far away that the change in angles is so small that it cannot be observed by the naked eye. It was not until hundreds of years later that people built telescopes that were accurate enough to detect stellar parallax. Astronomers of Tycho's time did not realize how far away stars were.
A further consideration for Tycho and his followers was biblical scripture. Some poetic passages seem to assume that the Sun moves or the Earth is stable.[citation needed]
[edit] History and development of the Tychonic system
Tycho's system was foreshadowed, in part, by that of Martianus Capella, who described a system in which Mercury and Venus are placed on epicycles around the Sun, which circles the Earth. Copernicus, who cited Capella's theory, even mentioned the possibility of an extension in which the other three of the six known planets would also circle the Sun.[4] In the 15th century, his work was anticipated by Nilakantha Somayaji, an Indian astronomer of the Kerala school of astronomy and mathematics, who presented a similar system where the planets of Mercury, Venus, Mars, Jupiter and Saturn orbit the Sun, which in turn orbits the Earth.[2][3]
The Tychonic system became a major competitor with the Copernican system as an alternative to the Ptolemaic. After Galileo's observation of the phases of Venus in 1610, most cosmological controversy then settled on variations of the Tychonic and Copernican systems. In a number of ways, the Tychonic system proved philosophically more intuitive than the Copernican system, as it reinforced commonsense notions of how the Sun and the planets are mobile while the Earth is not. Additionally, a Copernican system would suggest the ability to observe stellar parallax, which could not be observed until the 19th century. On the other hand, because of the intersecting deferents of Mars and the Sun (see diagram), it went against the Ptolemaic and Aristotelian notion that the planets were placed within nested spheres. Tycho and his followers revived the ancient Stoic philosophy instead, since it used fluid heavens which could accommodate intersecting circles.[citation needed]
[edit] Legacy of the Tychonic system
After Tycho's death, Johannes Kepler used the observations of Tycho himself to demonstrate that the orbits of the planets are ellipses and not circles, creating the modified Copernican system that ultimately displaced both the Tychonic and Ptolemaic systems. However, the Tychonic system was very influential in the late 16th and 17th centuries. After the Galileo affair, which transpired early in the 17th century, Copernicanism was officially forbidden to astronomers in the Roman Catholic Church; the Tychonic system was a religiously acceptable alternative that matched available observations. Jesuit astronomers in China used it extensively, as did a number of European scholars. Jesuits (such as Clavius, Christoph Grienberger, Christoph Scheiner, Odo van Maelcote) were the most efficient agent for the diffusion of the Tychonic system. It was chiefly through the influence of the Jesuits that the Roman Catholic Church adopted the Tychonic system, over a period of nine years (from 1611 to 1620), in a process directly prompted by the Galilean telescopic discoveries.[5]
The discovery of stellar aberration in the early 18th century by James Bradley and convinced people that the Earth did in fact move around the Sun, after which Tycho's system fell out of use among scientists. The theory of relativity in the early 20th century taught that motion is relative and that different frames of reference are valid, including non-inertial reference frames. In the modern era, some of the few who still subscribe to geocentrism use a modified Tychonic system with elliptical orbits.
[edit] References
- ^ Owen Gingerich, The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus, Penguin, ISBN 0143034766
- ^ a b Ramasubramanian, K. (1994), "Modification of the earlier Indian planetary theory by the Kerala astronomers (c. 1500 AD) and the implied heliocentric picture of planetary motion", Current Science 66: 784-90
- ^ a b Joseph, George G. (2000), The Crest of the Peacock: Non-European Roots of Mathematics, p. 408, Princeton University Press, ISBN 978-0-691-00659-8
- ^ [1]
- ^ Isabelle Pantin (1999), "New Philosophy and Old Prejudices: Aspects of the Reception of Copernicanism in a Divided Europe", Stud. Hist. Phil. Sci. 30: 237–262, p.247
