MEETING VENUS C. Sterken, P. P. Aspaas (Eds.) The Journal of Astronomical Data 19, 1, 2013 A Synoptic Overview of Selected Key People and Key Places Involved in Historical Transits of Venus Christiaan Sterken Vrije Universiteit Brussel, Brussels, Belgium Per Pippin Aspaas University of Tromsø, Norway Abstract. This paper presents an overview of the dramatis personae et situs, or significant characters and places dealt with in this book. Several geographical and political maps, and timelines are provided as an aid to the reader. 1. Introduction The transits of Venus are landmarks in the history of science, principally because of their use in historical attempts to measure the scale of our solar system. Eight transits of Venus have occurred since the prediction of the first such event by Jo- hannes Kepler in 1629. These transits appeared in four pairs spaced by 8 years, with each pair separated by a time interval of more than one century.1 The transit pairs alternatively happen in early June and in early December. Figure 1 shows the timeline of occurrence of the events, together with the publication date of four historical works that played a crucial role in the transit of Venus science, viz., 1. In 1629, Johannes Kepler published in his De raris mirisq[ue] Anni 1631. Phaenomenis, Veneris put`a& Mercurii in Solem incursu,2 the very first pre- dictions that a transit of Mercury will occur in November 1631, followed by a transit of Venus one month later. Kepler died a year before the events. 2. Isaac Newton’s Philosophiae naturalis principia mathematica, that layed down the theoretical basis for Kepler’s laws, was published in London in 1687. 3. Edmond Halley’s 1716 proposal Methodus singularis quˆaSolis Parallaxis sive distantia `aTerra, ope Veneris intra Solem conspiciendæ, tuto determinari poterit3 of determining the parallax of the Sun via the multi-site timing of transit ingress and egress times (Halley 1716). 4. Joseph-Nicolas Delisle’s method of measuring the solar parallax on the basis of either the ingress or the egress timing of a transit, communicated in various 1In fact, about 105.5 or 121.5 years. 2On the rare and admirable phenomena of the year 1631, namely the incursions of Mercury and Venus on the Sun. For details, see the paper by Thorvaldsen in these Proceedings. 3A special method through which the parallax of the Sun, or its distance from the Earth, by means of observations of Venus inside the Sun can be accurately determined. 3 4 Sterken & Aspaas letters and pamphlets distributed across Europe and finally in an elaborate memoir read before the Acad´emie Royale des Sciences in Paris, 30 April 1760.4 The subsequent Sections of this paper present an overview of the dramatis per- sonae et situs (scientific as well as political characters and places) together with key maps and timelines for all actors involved in the historical transits of Venus dealt with in these Proceedings. Two types of maps are provided: political maps and geographical maps. The former show national borders at a specific epoch, and are mainly meant for scholars whose field of study is remote from early modern political history. The latter serve to illustrate the geographical extent of the many expeditions that are discussed in this volume. Several of these maps will serve vari- ous papers, and complement diagrams and more detailed maps presented in the individual papers in this book. Note that most maps in this paper were made for illustration only, and that positions of the indicated locations are approximate (this is why scales have been omitted). § ¨© ¡¢¢ ¢¢ ¤¢¢ ¥¢¢ ¦¢¢¢ £ Figure 1. Chronology of all transits of Venus since the prediction of the first such event in 1629. The N symbols represent the publication date of four works that played crucial roles in the celestial mechanics science related to the transits (see text). 2. The 1631–1639 transits The 1631 transit was predicted by Johannes Kepler, but was not observable for those who knew about the forthcoming event. The 1639 transit was predicted by Jeremiah Horrocks and observed by himself and his friend William Crabtree. Their sites of observation were Much Hoole (Preston) and Broughton (Manchester), respectively. Figure 2 shows the lifespans of Johannes Kepler and the two sole Venus transit observers of the seventeenth century, and Fig. 3 shows a partial map of Britain with the observing locations marked. 4Delisle’s memoir, Description et usage de la Mappemonde dress´ee pour le passage de Venus sur le disque du Soleil qui est attendu le 6 Juin 1761 (Description and use of the mappe-monde of the transit of Venus across the disc of the Sun that is expected on 6 June, 1761) is summarized in the article Du passage de V´enus sur le Soleil annonc´epour l’ann´ee 1761 in the Histoire de l’Acad´emie Royale des Sciences, Ann´ee 1757 (published 1761), pp. 77–99. For details, see Woolf (1959), pp. 33–35 and the paper by Dumont & Gros in these Proceedings. A Synoptic Overview of Key People and Key Places 5 / 1 .0.& * , - &+ &.. $ ( %&&%' ) ! " # Figure 2. One-century timeline for the 1631–1639 transits. The horizontal bars represent the lifespan of each character. The vertical arrows indicate the times of the transits of Venus. Figure 3. Observing locations () for the 1639 transit in the UK. Map based on GoogleEarth. 3. The 1761–1769 transits 3.1. The place of birth of Maximilian Hell Among the many eminent scholars who devoted themselves to the study of the transits of the 1760s, the Jesuit Father Maximilian Hell is of particular relevance for this book. Figure 4 shows a political map of Europe at the moment of Maximilian Hell’s birth in 1720. His place of birth, a village just outside Bansk´a Stiavnicaˇ (or Schemnicium, Schemnitz, Selmecb´anya) in present-day Slovakia is indicated with an encircled symbol H. For a discussion on the national and ethnic identity of Maximilian Hell, see the papers by Kontler and by Sterken et al. in these Proceedings. 6 Sterken & Aspaas Figure 4. Political map of Europe for 1720 at the time when Maximilian Hell was born. His place of birth, Windschacht (Stiavnick´eBane)ˇ just outside Schemnicium (Schemnitz, Selmecb´anya, Bansk´a Stiavnica),ˇ is indicated by the encircled symbol H. Map based on Centennia mapping software. 3.2. Observatories in the Provincia Austriae of the Society of Jesus In early modern Central Europe, science was hugely influenced by the Society of Jesus. The role of the Jesuits in the formation of astronomical observatories is illustrated in Figure 5, which shows the location of the five Jesuit Observatories that flourished in the Provincia Austriae of the Society of Jesus during the eighteenth century. For details, see the paper by Posch et al. in these Proceedings. 3.3. Political map of Scandinavia, 1769 In astronomical terms, the far-northern parts of Europe formed a region with very similar advantages as far as the transits of Venus were concerned. Figure 6 shows a political map of northernmost Europe at the time when the eighteenth-century tran- sits took place. The map clearly illustrates the extent of the Kingdom of Denmark– Norway (in green), and the two other far-northern European powers Sweden and Russia (in pink and brown, respectively). A Synoptic Overview of Key People and Key Places 7 Figure 5. Jesuit Observatories in the Provincia Austriae of the Society of Jesus: Vienna = Vindobona, Wien, Viedeˇn, B´ecs (1,2); Graz = Graecium (3); Trnava = Tyrnavia, Tyrnau, Nagyszombat (4); and Cluj-Napoca = Clau- diopolis, Klausenburg, Kolozsv´ar (5). Hell’s birthplace is again pointed out with the letter H. Figure 6. Political map of northern Europe for 1769. Map based on Centennia mapping software. 8 Sterken & Aspaas 3.4. Geographical map of Russia Similar to Scandinavia, the geograpical location and extension of the Russian Empire gave it strategic advantages in the efforts to measure the solar parallax on the basis of the eighteenth-century transits of Venus. Figure 7 is a geographical map of Russia, with the principal places of observation of the 1761 and 1769 transits (see the papers by Bucher and by St´en & Aspaas in these Proceedings). Figure 7. Geographical map of Russia, with the principal places of obser- vation of the 1761 and 1769 transits. The numbers refer to the places listed in Table 3. 3.5. Geographical map of Scandinavia Figure 8 shows all Scandinavian observing sites listed in Tables 1 and 2. See the papers by Widmalm, Aspaas, Pekonen and Voje Johansen in these Proceedings. 3.6. Historical geographical map of Vardø 1772 Figure 9 shows the historical map of Wardoehuus (Vardø) made by Maximilian Hell, who observed the 1769 transit from this island. The latitude of the observatory is indicated: 70◦2203600 N; the longitude “ab Insula Ferri” is 48◦4004500 (3h14m43s East of Ferro).5 5Isla de El Hierro, the smallest of the seven Canarian Islands, and also the prime meridian in common use in those days. A Synoptic Overview of Key People and Key Places 9 Figure 8. Scandinavian observing sites listed in Tables 1 and 2. Map based on GoogleEarth. 10 Sterken & Aspaas Figure 9. Insula Wardoehuus cum Adjacentibus Insulis et Littore Finn marchico a Maximiliano Hell (1772). The scale bar is expressed in Viennese foot, and its total length is about 1194.5m. Source: Ephemerides Astronom- icae ad Meridianum Vindobonensem Anni 1791 (Vienna, 1790). A Synoptic Overview of Key People and Key Places 11 3.7. The 1761–69 transits observed from Scandinavian territories Tables 1 and 2 give an overview of observers and places for the 1761 and 1769 transits from Scandinavian territories.