Tychonic system

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Tychonic system

The Tychonic system (or Tychonian system) is a model of the Solar system published by Tycho Brahe in the late 16th century which combines 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 Valentin Naboth[1] and Paul Wittich, a Silesian mathematician and astronomer.[2] A similar yet mathematically more efficient geoheliocentric model was also proposed a century earlier[3]by Nilakantha Somayaji of the Kerala school of astronomy and mathematics.[4][5]

It is essentially a geocentric model; the Earth is at the center of the universe. The Sun and Moon and the stars revolve around the Earth, and the other five planets revolve around the Sun. It can be shown that the motions of the planets and the Sun relative to the Earth in Brahe's system are mathematically equivalent to the motions in Copernicus' heliocentric system.[6]

Motivation for the Tychonic system[edit]

Tycho admired aspects of Copernicus's heliocentric model of the solar system, but felt that it had problems as concerned physics, astronomical observations of stars, and religion. Regarding the Copernican system Tycho wrote,

This innovation expertly and completely circumvents all that is superfluous or discordant in the system of Ptolemy. On no point does it offend the principle of mathematics. Yet it ascribes to the Earth, that hulking, lazy body, unfit for motion, a motion as quick as that of the aethereal torches, and a triple motion at that.[7]

In regard to physics, Tycho held that the Earth was just too sluggish and heavy to be continuously in motion. According to the accepted Aristotelian physics of the time, the heavens (whose motions and cycles were continuous and unending) were made of "Aether" or "Quintessence"; this substance, not found on Earth, was light, strong, and unchanging, and its natural state was circular motion. By contrast, the Earth (where objects seem to have motion only when moved) and things on it were composed of substances that were heavy and whose natural state was rest—thus the Earth was a "lazy" body that was not readily moved.[8] Thus while Tycho acknowledged that the daily rising and setting of the sun and stars could be explained by the Earth's rotation, as Copernicus had said, still




Copernicans offered a religious response to Tycho's geometry: titanic, distant stars might seem unreasonable, but they were not, for the Creator could make his creations that large if He wanted.[14] In fact, Rothmann responded to this argument of Tycho's by saying



Tycho advocated as an alternative to the Ptolemaic geocentric system a "geo-heliocentric" system (now known as the Tychonic system), which he developed in the late 1570s. In such a system, the sun, moon, and stars circle a central Earth, while the five planets orbit the Sun.[17] The essential difference between the heavens (including the planets) and the Earth remained: Motion stayed in the aethereal heavens; immobility stayed with the heavy sluggish Earth. It was a system that Tycho said violated neither the laws of physics nor sacred scripture — with stars located just beyond Saturn and of reasonable size.[18][19]

Precursors to Geo-heliocentrism[edit]

Tycho was not the first to propose a geoheliocentric system. It used to be thought that Heraclides in the 4th century BC had suggested that Mercury and Venus revolve around the Sun, which in turn (along with the other planets) revolves around the Earth.[20] Macrobius Ambrosius Theodosius (395–423 AD) later described this as the "Egyptian System," stating that "it did not escape the skill of the Egyptians," though there is no other evidence it was known in ancient Egypt.[21][22] The difference was that Tycho's system had all the planets (with the exception of Earth) revolving around the Sun, instead of just the interior planets of Mercury and Venus. In this regard, he was anticipated in the 15th century by the Kerala school astronomer Nilakantha Somayaji, whose geoheliocentric system also had all the planets revolving around the Sun.[23][24] The difference to both these systems was that Tycho's model of the Earth does not rotate daily, as Heraclides and Nilakantha claimed, but is static.

History and development of the Tychonic system[edit]

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.[25] This was foreshadowed by the Irish Carolingian scholar Johannes Scotus Eriugena in the 9th century, who went a step further than Capella by suggesting both Mars and Jupiter orbited the sun as well.[26] In the 15th century, his work was anticipated by Nilakantha Somayaji, an Indian astronomer of the Kerala school of astronomy and mathematics, who first presented a geoheliocentric system where all the planets (Mercury, Venus, Mars, Jupiter and Saturn) orbit the Sun, which in turn orbits the Earth.[4][5][27]

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]

Legacy of the Tychonic system[edit]

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. In 1616, during the Galileo affair, the papal Congregation of the Index banned all books advocating the Copernican system, including works by Copernicus, Galileo, Kepler and other authors until 1758.[28][29] The Tychonic system was an acceptable alternative as it explained the observed phases of Venus with a static Earth. 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 Jesuit scientists 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.[30]

The discovery of stellar aberration in the early 18th century by James Bradley proved that the Earth did in fact move around the Sun and Tycho's system fell out of use among scientists.[31] In the modern era, some of the modern geocentrists use a modified Tychonic system with elliptical orbits, while rejecting the concept of relativity.[32][33]


  1. ^ Westman, Robert S. (1975). The Copernican achievement. University of California Press. p. 322. ISBN 978-0-520-02877-7. OCLC 164221945. 
  2. ^ Owen Gingerich, The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus, Penguin, ISBN 0-14-303476-6
  3. ^ Nilakantha Somayaji#cite note-6
  4. ^ 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. 
  5. ^ 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
  6. ^ "The Tychonic system is, in fact, precisely equivalent mathematically to Copernicus' system." (p. 202) and "[T]he Tychonic system is transformed to the Copernican system simply by holding the sun fixed instead of the earth. The relative motions of the planets are the same in both systems ..." (p. 204), Kuhn, Thomas S. , The Copernican Revolution (Harvard University Press, 1957).
  7. ^ Owen Gingerich, The eye of heaven: Ptolemy, Copernicus, Kepler, New York: American Institute of Physics, 1993, 181, ISBN 0-88318-863-5
  8. ^ Blair, Ann, "Tycho Brahe's critique of Copernicus and the Copernican system", Journal of the History of Ideas, 51, 1990: 355-377, doi:10.2307/2709620, pages 361-362. Moesgaard, Kristian Peder, "Copernican Influence on Tycho Brahe", The Reception of Copernicus' Heliocentric Theory (Jerzy Dobrzycki, ed.) Dordrecht & Boston: D. Reidel Pub. Co. 1972. ISBN 90-277-0311-6, page 40. Gingerich, Owen, "Copernicus and Tycho", Scientific American 173, 1973: 86 – 101, page 87.
  9. ^ Blair, 1990, 361.
  11. ^ The sizes Tycho measured turned out to be illusory -- an effect of optics, the atmosphere, and the limitations of the eye (see Airy disk or Astronomical seeing for details). By 1617, Galileo estimated with the use of his telescope that the largest component of Mizar measured 3 seconds of arc, but even that turned out to be illusory -- again an effect of optics, the atmosphere, and the limitations of the eye [see L. Ondra (July 2004). "A New View of Mizar". Sky & Telescope: 72–75. ]. Estimates of the apparent sizes of stars continued to be revised downwards, and, today, the star with the largest apparent size is believed to be R Doradus, no larger than 0.057 ± 0.005 seconds of arc.
  12. ^ Blair, 1990, 364. Moesgaard, 1972, 51.
  13. ^ Blair, 1990, 364.
  14. ^ Moesgaard, 1972, 52. Vermij R., "Putting the Earth in Heaven: Philips Lansbergen, the early Dutch Copernicans and the Mechanization of the World Picture", Mechanics and Cosmology in the Medieval and Early Modern Period (M. Bucciantini, M. Camerota, S. Roux., eds.) Firenze: Olski 2007: 121-141, pages 124-125.
  15. ^ Graney, C. M., "Science Rather Than God: Riccioli's Review of the Case for and Against the Copernican Hypothesis", Journal for the History of Astronomy 43, 2012: 215-225, page 217.
  16. ^ Blair, 1990,362-364
  17. ^ Gingerich, 1973. Moesgaard, 1972, 40-43.
  18. ^ Moesgaard 40, 44
  19. ^ Graney, C. M. (March 6, 2012). The Prof says: Tycho was a scientist, not a blunderer and a darn good one too! The Renaissance Mathematicus. http://thonyc.wordpress.com/2012/03/06/the-prof-says-tycho-was-a-scientist-not-a-blunderer-and-a-darn-good-one-too/
  20. ^ Eastwood, B. S. (1992-11-01). "Heraclides and Heliocentrism - Texts Diagrams and Interpretations". Journal for the History of Astronomy. 23: 233. Bibcode:1992JHA....23..233E. 
  21. ^ Neugebauer, Otto E. (1975). A history of ancient mathematical astronomy. Birkhäuser. ISBN 3-540-06995-X. 
  22. ^ Rufus, W. Carl (1923). "The astronomical system of Copernicus". Popular Astronomy. 31: 510–521 [512]. Bibcode:1923PA.....31..510R. 
  23. ^
  25. ^ [1]
  26. ^ Stanford Encyclopedia of Philosophy. "John Scottus Eriugena." First published Thu Aug 28, 2003; substantive revision Sun Oct 17, 2004. Accessed April 30, 2014.
  27. ^ Ramasubramanian, K., "Model of planetary motion in the works of Kerala astronomers", Bulletin of the Astronomical Society of India, 26: 11–31 [23–4], Bibcode:1998BASI...26...11R, retrieved 2010-03-05 
  28. ^ Finochiario, Maurice (2007). Retrying Galileo. University of California Press. 
  29. ^ Heilbron (2010), p.218-9
  30. ^ Pantin, Isabelle (1999). "New Philosophy and Old Prejudices: Aspects of the Reception of Copernicanism in a Divided Europe". Stud. Hist. Phil. Sci. 30 (237–262): 247. 
  31. ^ Seligman, Courtney. Bradley's Discovery of Stellar Aberration. (2013). http://cseligman.com/text/history/bradley.htm
  32. ^ Plait, Phil. (Sept. 14, 2010). Geocentrism Seriously? Discover Magazine. http://blogs.discovermagazine.com/badastronomy/2010/09/14/geocentrism-seriously/#.UVEn7leiBpd
  33. ^ Musgrave, Iam. (Nov. 14, 2010). Geo-xcentricities part 2; the view from Mars. Astroblog. http://astroblogger.blogspot.com/2010/11/geo-xcentricities-part-2-view-from-mars.html

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