Tycho Brahe


Tycho Brahe : biography

14 December 1546 – 24 October 1601

Religion played a role in Tycho’s geocentrism also – he cited the authority of scripture in portraying the Earth as being at rest. He rarely used Biblical arguments alone (to him they were a secondary objection to the idea of Earth’s motion) and over time he came to focus on scientific arguments, but he did take Biblical arguments seriously.Blair, 1990,362-364

Tycho advocated 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.Gingerich, 1973. Moesgaard, 1972, 40-43. 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.Moesgaard 40, 44

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. 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. 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.K. Ramasubramanian, M. D. Srinivas, M. S. Sriram (1994). "", Current Science 66, p. 784-790.George G. Joseph (2000). The Crest of the Peacock: Non-European Roots of Mathematics, p. 408. Princeton University Press. 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.

Another crucial difference between Tycho’s 1587 geo-heliocentric model and those of other geo-heliocentric astronomers, such as Paul Wittich, Reimarus Ursus, Helisaeus Roeslin and David Origanus, was that the orbits of Mars and the Sun intersected.Ibid This was because Tycho had come to believe the distance of Mars from the Earth at opposition (that is, when Mars is on the opposite side of the sky from the Sun) was less than that of the Sun from the Earth. Tycho believed this because he came to believe Mars had a greater daily parallax than the Sun. But in 1584 in a letter to a fellow astronomer, Brucaeus, he had claimed that Mars had been further than the Sun at the opposition of 1582, because he had observed that Mars had little or no daily parallax. He said he had therefore rejected Copernicus’s model because it predicted Mars would be at only two-thirds the distance of the Sun.See p178-80 of Dreyer’s 1890 ‘Tycho Brahe’ But he apparently later changed his mind to the opinion that Mars at opposition was indeed nearer the Earth than the Sun was, but apparently without any valid observational evidence in any discernible Martian parallax.See p171 The Wittich Connection Gingerich and Westman 1988 Such intersecting Martian and solar orbits meant that there could be no solid rotating celestial spheres, because they could not possibly interpenetrate. Arguably this conclusion was independently supported by the conclusion that the comet of 1577 was superlunary, because it showed less daily parallax than the Moon and thus must pass through any celestial spheres in its transit.


Although Tycho’s planetary model was soon discredited, his astronomical observations were an essential contribution to the scientific revolution. The traditional view of Tycho is that he was primarily an empiricist who set new standards for precise and objective measurements.Kragh, pp. 220–22 This appraisal originated in Pierre Gassendi’s 1654 biography, Tychonis Brahe, equitis Dani, astronomorum coryphaei, vita. It was furthered by Johann Dreyer’s biography in 1890, which was long the most influential work on Tycho. According to historian of science Helge Kragh, this assessment grew out of Gassendi’s opposition to Aristotelianism and Cartesianism, and fails to account for the diversity of Tycho’s activities.