Astronomical Images : Copernican world system, first edition

Nicholas Copernicus

Astronomical Images

<p style='text-align: justify;'>Copernicus was born in Torun, Poland, in 1473. He first studied at the University of Cracow (1491-94), where he may have learnt astronomy and astrology from John of Glogau and Albertus of Brudzewo. Through his uncle, Lukas Watzenrode (who later became the bishop of Varmia), Copernicus was elected a canon of the cathedral chapter of Frombork (Frauenburg). As part of his conditions of office, he went to the University of Bologna (1496-1500) to study both canon and civil laws. There, he lodged with and worked as an assistant to Domenico Maria da Novara (1454-1504), Professor of Mathematics and Astrology and also the official compiler of prognostications for the university. Domenico Maria was probably the source of Copernicus's knowledge of Regiomontanus's <i>Epitome</i> which spelt out the proposition that all epicyclic models could be transferred to eccentric ones (a point that Ptolemy had denied). While at Bologna, Copernicus made some astronomical observations, and most likely came across Giovanni Pico della Mirandola's (1463-94) <i>Disputationes adversus astrologiam divinatricem</i> (Disputations Against Divinatory Astrology) (1496). Among various arguments set forth by Pico against the validity of astrology was the uncertainty of astronomy, including uncertainties about the order of planets. After briefly returning to Frombork, Copernicus studied medicine at the University of Padua (1501-3) and then moved on to the University of Ferrara where he obtained a doctorate in Canon Law (1503). While at Padua, he probably came across Giorgio Valla's <i>De expetendis et fugiendis rebus opus</i> (Concerning What to Seek and What to Shun) (1501), which was his source for Aristarchus's geocentric theory. Copernicus then returned to Varmia, where he was based for the rest of his life. He acted as medical advisor and secretary to his uncle at Heilsberg, and was later heavily involved with the administrative tasks in the diocese of Frombork. In 1514, the Lateran Council sought Copernicus's opinion on calendar reform. Around the same time, he began to circulate in manuscript the '<i>Commentariolus</i>' (A Brief Description), in which he criticized the current Ptolemaic system for not adhering to the principle of uniform circular motions and suggested instead a system in which the Earth and all the other planets rotate around the Sun. By the 1530s, Copernicus's reputation as a skilled mathematician had even reached the ears of the Pope. A professor of mathematics at the University of Wittenberg, Georg Joachim Rheticus (1514-1574), visited Copernicus in 1539. Copernicus shared his ideas with him, and Rheticus published the <i>Narratio prima</i> (First Report) in 1540 at Gdansk, in which he reported Copernicus's heliostatic theory in an astrological framework: the changing fortunes of the kingdom of the World, according to Rheticus, depended on the changing eccentricity of the Sun. Following the favourable reception of the <i>Narratio prima</i>, Rheticus persuaded Copernicus to publish a full account. This became <i>De revolutionibus orbium coelestium</i> (On the Revolutions of the Heavenly Spheres), published in March 1543 at Nuremberg by Johannes Petreius. This contained an unauthorized preface by Andreas Osiander (1498-1552), presenting Copernicus's world system not as an account of the true form of the cosmos, but as a set of devices fabricated for predictive purposes. Copernicus died two months later. <i>De revolutionibus</i> follows closely the structure of Ptolemy's <i>Almagest</i>, and is based on parameters and data from Ptolemy. Copernicus's dedication to the Pope Paul III is written in a fashionable humanistic style. He does indeed provide a model of the Universe in which the Earth and all the other planets orbit around the Sun and the Earth has a daily rotation, but the Sun itself was not quite in the centre of that universe. He established the order of planets and devised a system that accounted for the movements of planets without equants, but he was motivated by the desire to establish uniform circular motion, itself a classical ideal. Copernicus certainly believed that this was the true system of the physical Universe, but this conviction was not shared widely by his contemporaries (including Osiander) for various reasons. Robert Westman has recently suggested that Copernicus's planetary ordering was a response to Pico's criticism of astronomy as part of his diatribe against astrology. This iconic figure of planetary order, taken from book 1, chapter 10 of <i>De revolutionibus</i> (1543), represents Nicholas Copernicus's heliostatic view of the Universe. It is well known that this figure printed in <i>De revolutionibus</i> does not exactly match the sketch in the original manuscript (the facsimile edition of the original manuscript is available as the first volume of Czartoryski (1973); a modern rendering of the original diagram may be found in Rosen (1992), p. 21). In the original figure, Arabic numerals are used instead of Roman numerals to denote the spheres, numbered from the outside to the inside. The original figure had eight concentric circles, with the following inscriptions for the spaces between the circle: 1. Immovable sphere of the fixed stars (in the space between the seventh and eighth circles) 2. Saturn revolves in thirty years (in the space between the sixth and seventh circles) 3. Jupiter's revolution in twelve years (in the space between the fifth and sixth circles) 4. Mars' revolution in two years (in the space between the fourth and fifth circles) 5. The annual revolution of the Earth, together with the Moon (in the space between the third and fourth circles) 6. Venus' revolution in nine months (in the space between the second and third circles) 7. Mercury's revolution in eighty days (in the space between the first and second circles) At the centre is the word, 'Sun'. In the printed figure, there is a small circle with a thick circumference and a black dot in the centre ' the standard symbol for the Sun. This may have been a misinterpretation of the hole in the original manuscript made by the foot of a compass. There are then nine concentric circles. Inscriptions for Mercury and Venus are placed in the same position as the original (i.e. in the space between the first and second, and second and third circles respectively). The major modification occurs next, with three circles pertaining to 'the annual revolution of the Earth together with the lunar orb'. It shows a circle in the middle of the orb of the Earth, with the Earth shown as a dot on that circle and the circle of the Moon, with a symbol for the Moon. The label for the fixed stars, instead of being placed between the outermost and next circles, is placed outside the ninth circle. The space between the fifth and the sixth circle carries no label, and then inscriptions for the four remaining spheres are found in the same order as the original. The gap between the fifth and the sixth circle is caused by the fact that the inscription for the sphere of the fixed stars was placed outside the outermost circle. The printed figure, especially if the labels are understood as attached to the lines, could lead to a misunderstanding that Copernicus was delineating some kind of planetary orbit, but his near contemporaries understood that he was signifying orbs in the tradition of Sacrobosco's <i>Sphaera</i>, and duly correctly it. See for example Thomas Digges' <i>A Perfit Description of the Celestial Orbes</i> and Michael Maestlin's appendix to Kepler's <i>Mysterium cosmographicum</i>. In the printed figure the fixed stars are designated outside the outermost circle, unbounded. This, together with Copernicus's ambiguous description of the heavens as '<i>infinitus</i>' in magnitude (meaning 'immense', but open to interpretation as 'infinite'), could be misunderstood to imply his commitment to an infinite cosmos, and this is the way in which Digges represents it.</p>


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