Kepler and 'the irreducible and obstinate facts'
| dc.contributor.author | Valente, Mariana | |
| dc.date.accessioned | 2014-02-06T18:18:30Z | |
| dc.date.available | 2014-02-06T18:18:30Z | |
| dc.date.issued | 2013 | |
| dc.description.abstract | This issue coincides with a turning point for CAAUL and for Portuguese astronomers and astrophysicists in general. In July, CAAUL organised the 23rd national meeting for astronomy and astrophysics (XXIII ENAA), the showcase for the exciting research carried out in the various universities and institutes throughout Portugal and beyond, research that is proving more and more difficult to pursue given the straightened times we live in. Results were presented in a diverse range of areas including planetary systems, stellar properties, stellar evolution, the Milky Way galaxy, extra-galactic astrophysics, cosmology, astroparticle physics – see below a brief report by Ismael Tereno and Elvira Leonardo. | por |
| dc.identifier.authoremail | mjv@uevora.pt | |
| dc.identifier.scientificarea | 734 | por |
| dc.identifier.uri | http://caaul.oal.ul.pt/ficheiros/pdf/CAAULGazette_v2n2_Summer2013%20.pdf | |
| dc.identifier.uri | http://hdl.handle.net/10174/10604 | |
| dc.language.iso | eng | por |
| dc.publisher | David Berry | por |
| dc.rights | openAccess | por |
| dc.subject | Kepler; | por |
| dc.subject | koestler; | por |
| dc.subject | Whitehead | por |
| dc.title | Kepler and 'the irreducible and obstinate facts' | por |
| dc.type | other | por |
| degois.publication.firstPage | I would like to invite you to read the provocative and beautiful book The Sleepwalkers, by Arthur Koestler1. I shall not discuss Koestler's metaphor of scientists as sleepwalkers. Instead I will highlight Koestler's narrative on Kepler's personality, which puts us into contact with some decisive moments in Kepler's life, in a time much troubled by religious wars; a life that embodies the passage of the medieval to the modern world. Medieval and modern worldviews and ways of thinking are contained in Kepler's two books - Mysterium Cosmographicum (1596) and Astronomia Nova (1609). In the first, abstract generalization dominates a geometrical world without the balance of particular facts. In the second, written after intensive work on the orbit of Mars, developed alongside Tycho Brahe, a theory, built on years of labour and torment, was instantly thrown away because of the discord of a miserable eight minutes arc, as Koestler dramatizes it. To appreciate the difference in thinking in these two books, let us consider some fragments of Koestler's narrative - ''while still a student in Tuebingen, he had heard from his teacher, Maeslin, about Copernicus, and agreed that the sun must be in the centre of the universe 'for physical or if you prefer, for metaphysical reasons'. He then began to wonder why there existed just six planets 'instead of twenty or a hundred' and why the distances and velocities of the planets were what they were'". The answers to these questions emerge in a moment of great inspiration when Kepler draws a geometric figure on the blackboard, showing a triangle fitted by two circles. "As he looked at two circles, it suddenly struck him that their ratios were the same as those of the orbits of Saturn and Jupiter. The rest came in a flash. Saturn and Jupiter are the first (the two outermost) planets, and the 'triangle is the first figure in geometry | por |
| degois.publication.lastPage | Page 4 The CAAUL Gazette: Summer 2013, Vol.2, No.2 would have patched up my hypothesis accordingly. But since it was not permissible to ignore them, those eight minutes point the road to a complete reformation of astronomy: they have become the building material for a large part of this work'. We can follow the final capitulation of an adventurous mind before 'the irreducible and obstinate facts' 1 . New adventurous ideas are emerging. As Whitehead writes- "it is this union of passionate interest in the detailed facts with equal devotion to abstract generalization which forms the novelty in our present society". What provokes these changes in Kepler's thought? One reason is all his work and experience, living and thinking in proximity of Tycho Brahe. Koestler associates it with the idea of causality that was growing in Kepler's mind - "it was his introduction of physical causality into the formal geometry of the skies which made it impossible for him to ignore the eight minutes arc (...)". Koestler's narrative is a masterpiece for all, scientists, science educators, cultural historians. In it we can feel all the emotions, thought and suffering of a man who, by changing himself, has changed the vision of the universe. 1 Koestler, A. (1989). The Sleepwalkers - a history of man's changing vision of the universe. RedShift London: Arkana. 2 “The task before Kepler was to define the orbit of Mars (...). He chose out of Tycho's treasure four observed positions of Mars at the convenient dates”. Kepler worked very hard “to determine, out of these four positions, the radius of the orbit, the direction of the axis, and the position of the three central points on it [position of the sun, orbital centre, and punctum equans]As a result of his seventy-odd trials, he arrived at values for the radius of the orbit and for the three central points, with a permissible error less than 2 ́, the correct positions of Mars for all the ten oppositions recorded by Tycho”. Kepler proclaimed his victory saying that the hyphothesis based on his method ‘not only satisfies the four positions on which it was based, but also correctly represents, within two minutes, all the other observations’. The next chapter of Astronomia Nova begins with these words: ‘Who would have thought it possible? This hypothesis, which so closely agrees with the observed oppositions, is nevertheless false...’ When he tried to adjust his model to much more observations, to “rare pieces from Tycho’s treasure of observations”, he arrived at a difference between the positions calculated from his theory and the positions of Mars observed by Tycho. A difference of eight arc minutes. 3 This is a Whitehead's expression. See Whitehead, A. (1997 - 1stedition 1926). Science and the Modern World. Free Press. Mariana Valente Departamento de Física da Universidade de Évora & Centro de Estudos de História e Filosofia da Ciência | por |
| degois.publication.location | Lisbon | por |
| degois.publication.title | THE CAAUL GAZETTE | por |
| degois.publication.volume | 2 | por |