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- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
The spectacular reappearance of the aurora borealis at the beginning of the 18th century, often observed simultaneously from different observatories in Europe, mobilized and federated a large community of astronomers on a European scale. It encouraged them to communicate the results of their observations and, in compiling exhaustive catalogs of information, has helped to establish a system of the aurora borealis that can be further studied in the future, according to the experimental method inherited from the previous century. This book is dedicated to some of the main aurora observers in Europe and to the human, institutional and philosophical context in which they evolved in the first half of the 18th century. Its reading should be seen as a retrospective journey through the scholarly world of the Enlightenment, during which the same scholars are frequently encountered and reencountered, yet each time in different contexts, or from different angles, with the aim of compiling an account of the swarming of ideas and encounters that constituted the development of experimental science in this pivotal period.
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Table of Contents
Cover
Title Page
Copyright Page
Introduction
1 The Aurora Borealis Issue of the Affirmation of the Cartesian Mechanism and the Dispute Between Paris and Montpellier: The French Choice
1.1. Introduction
1.2. The two main systems of the aurora borealis
1.3. History of the aurora borealis in the volumes of the Académie Royale des Sciences between 1716 and 1733
1.4. The Montpellier actors: François de Plantade and the Société Royale des Sciences
1.5. The Parisian actors: Bernard le Bovier de Fontenelle and Jean-Jacques Dortous de Mairan, the Académie Royale des Sciences
1.6. The London actors: Hans Sloane and Edmond Halley, the Royal Society
1.7. Discussion of the reasons for rejecting Plantade’s submission
2 Joseph-Nicolas Delisle: Grandeur and Vicissitudes of a Newtonian Scientist with Thwarted Ambitions
2.1. Introduction
2.2. Delisle in the period before his departure for Russia (1710–1725)
2.3. The invitation to St. Petersburg and Delisle’s Russian period (1726–1747)
2.4. Brief synthesis of Delisle’s scientific trajectory
2.5. Conclusion
3 The Creation Ex-nihilo and the Beginnings of the Imperial Russian Academy of Sciences: The Influence of Christian Wolff
3.1. Introduction
3.2. The foundation of the Imperial Academy of Sciences in St. Petersburg
3.3. Christian Wolff, the aurora borealis and their first observers at the Academy of Sciences in St. Petersburg
3.4. The Imperial Academy of Sciences of St. Petersburg
3.5. Conclusion
4 Anders Celsius and the European Observation Networks, Setting Up a Science Society and an Astronomical Observatory in Uppsala
4.1. Introduction
4.2. The life of Celsius
4.3. Three European networks for the observation of natural phenomena
4.4. The Royal Society of Uppsala and Celsius’ legacy
4.5. Conclusion
5 Genesis of the Academies of Bologna and Berlin, the Involvement of Women in Astronomy and the Gender Issue
5.1. Introduction
5.2. Three examples of “astronomical households”
5.3. Two examples of astronomical institutions: the academies of Bologna and Berlin and their observatories
5.4. Astronomical households, institutions and gender in Bologna and Berlin
5.5. Conclusion
Conclusion
Appendix: About the Polar Lights, by Friedrich Christoph Mayer
References
Index
End User License Agreement
List of Illustrations
Chapter 1
Figure 1.1 Drawing of an aurora borealis published in Philosophical Transactio...
Figure 1.2 Extract from the minutes of the Académie Royale des Sciences for th...
Figure 1.3 Auroral arcs (without light jets) during the aurora borealis seen i...
Figure 1.4 Engraving representing the aurora borealis of December 16, 1737 obs...
Figure 1.5 Excerpt from the list of memoirs sent by the Société Royale des Sci...
Figure 1.6 Cover page of the book containing the speech given by François de P...
Figure 1.7 Cover page of the first volume of the Histoire de l’Académie Royale...
Figure 1.8 Cover page of the first volume of Philosophical Transactions (1665)
Chapter 2
Figure 2.1 Extract from the minutes of the Académie Royale des Sciences for th...
Figure 2.2 Sketch representing the tower of La Ferté Alais mentioned by Delisl...
Figure 2.3 Excerpt from Delisle’s letter of November 1, 1723 to Wurzelbau...
Figure 2.4 View of Berezov from the south (Koenigsfeld 1768, p. 113)
Figure 2.5 Territory between the cities of Arcangel, St. Petersburg and Wologd...
Chapter 3
Figure 3.1 Engraving extracted from Delisle’s manuscripts preserved at the Lib...
Figure 3.2 Cover page of Wolff’s treatise on the aurora borealis of March 17, ...
Figure 3.3 Cover page of the first volume of the Commentarii Academiae scienti...
Figure 3.4 First page of Mayer’s 1726 treatise on the aurora borealis (Mayer 1...
Figure 3.5 Simplified version of the trigonometric formula established by Maye...
Figure 3.6 Table giving the height of different aurora borealis in leagues (1 ...
Figure 3.7 Schematic views of the aurora borealis systems proposed by Mayer, M...
Chapter 4
Figure 4.1 Plates illustrating the aurora borealis of December 16, 1737 observ...
Figure 4.2 Meteorological (sky condition, temperature, wind, precipitation, ev...
Figure 4.3 Contemporary copy of the magnetic needle (compass) commissioned by ...
Figure 4.4 Meteorological records published by Giovanni Poleni showing at diff...
Figure 4.5 Left panel: temperatures corresponding to the greatest cold observe...
Figure 4.6 Cover page of the first volume of Acta literaria sveciæ for the yea...
Chapter 5
Figure 5.1 Some examples of Ramus’ drawings of the aurora borealis of March 17...
Figure 5.2 Extract from the letter of July 24, 1744, from Christine Kirch to D...
Figure 5.3 Cover page of the Ephemerides published by Eustachio Manfredi in 17...
Figure 5.4 Excerpt from the Harangue de Hercules Corazzi read on March 13, 171...
Figure 5.5 Cover page of the first volume of the Commentaries of the Academy o...
Figure 5.6 Cover pages of the first volume of the Memoirs of the Académie Roya...
Figure 5.7 Coat of arms of the Accademia dei Ricovrati representing the image ...
Guide
Cover Page
Title Page
Copyright Page
Introduction
Table of Contents
Begin Reading
Conclusion
Appendix: About the Polar Lights, by Friedrich Christoph Mayer
References
Index
WILEY END USER LICENSE AGREEMENT
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Series EditorDenis-Didier Rousseau
Observers of the Aurora Borealis in Europe
Journey into the Learned World of the Enlightenment
Eric Chassefière
First published 2023 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
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John Wiley & Sons, Inc.
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© ISTE Ltd 2023The rights of Eric Chassefière to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s), contributor(s) or editor(s) and do not necessarily reflect the views of ISTE Group.
Library of Congress Control Number: 2022947541
British Library Cataloguing-in-Publication DataA CIP record for this book is available from the British LibraryISBN 978-1-78630-792-7
Introduction
The subject of this book is not the observation and the scientific interpretation of the aurora borealis, which we have dealt with in a previous book (Chassefière 2021a), but the human, institutional and philosophical context in which the principal scientists involved in the observation of the phenomenon evolved in the first half of the 18th century. The aurora borealis by itself, as a physical phenomenon, was only approached when the understanding of the scientific fact enabled clarifying the human or philosophical context in which it is inscribed. This book is dedicated to the observers of the Northern Lights, for the most part astronomers whose main interests were found in astronomy and its applications to cartography, and to their individual and collective trajectories, in an institutional and philosophical space undergoing profound change. The choice of the aurora borealis as the main theme of the narrative is due to the unifying character of the phenomenon, which, because of its very high altitude, can only be correctly characterized by measurements made simultaneously in places thousands of kilometers away, a scale that is that of Europe, and not of each of its states. But before starting our European journey in the academic world of the Enlightenment, it is useful to review the human and scientific landscape that constitutes its framework.
The aurora borealis was a phenomenon still relatively unknown at the beginning of the 18th century. The abbot Pierre-Nicolas Bertholon provides a very long historical and scientific analysis of the phenomenon in the article “Aurore Boréale” of the Dictionnaire de Physique1 (1793). He quotes Aristotle, witness of an aurora in Macedonia, who compared the appearance of the aurora borealis, when it was extended, to “the blaze of a campaign whose bale is burned”. Aristotle gave pictorial names to the jets of light observed on this occasion: “lighted firebrands, torches, lamps, burning beams”. According to him, the most common colors of the aurora borealis were “purple, bright red and the color of blood”. Bertholon reports numerous testimonies from the past, from Antiquity to the very beginning of the 18th century, mentioning scenes of panic among the populations, and frequent associations of the aurora borealis with a fatal omen, announcing wars and desolation. In particular, the fear of the Apocalypse, which seized Europe at the end of the 15th century, and lasted until the middle of the 17th century, conferred to the aurora borealis and to other unexplained phenomena, such as rainbows, solar or lunar halos, or flying fires (meteoroids entering the atmosphere) a particularly disturbing character (Schröder 2005). Superstitions in this area were still alive at the turn of the 18th century. The astronomer Maria Winkelmann-Kirch, who observed the aurora borealis from Berlin in March 1707, wondered in a letter to Gottfried Wilhelm Leibniz in November of the same year: “I am not sure what nature was trying to tell us” (Schiebinger 1987, p. 183). The sustained resumption of the aurora borealis in 1716, after a long period of interruption (attributable to low solar activity, identifiable by the smaller number of spots visible on the disk: the so-called “Maunder Minimum”, which lasted from 1645 to 1715), with the exception of the timid resumption of 1686 and 1707, marked an important turning point in the popular understanding of unexplained atmospheric phenomena. In Halle, Germany, the philosopher and physicist Christian Wolff, one week after the event, gave a conference on the subject at the request of the citizens of his city, to provide his interpretation of the aurora borealis, a natural phenomenon according to him, completely explicable without calling upon any divine intervention (Schröder 2005).
The irruption of the aurora borealis phenomenon aroused a considerable craze among the scientists of the time, and this all the more so as it was still poorly documented, and the only rational explanations of the phenomenon were still strongly inspired by Aristotelian meteorology. This one attributed the origin of the aurora borealis and other atmospheric luminous phenomena to dry vapors raised in the atmosphere by the heat of the sun. As opposed to wet vapor, remaining close to the Earth’s surface and giving rise to rain, dry vapor rises and extends to the boundary between the Earth’s sphere and the rotating celestial sphere, contact with the moving ether in movement provoking its ignition: “We must think of what we just called fire as being spread round the terrestrial sphere on the outside like a kind of fuel, so that a little motion often makes it burst into flame just as smoke does: for flame is the ebullition of a dry exhalation” (Aristotle 2009, Book I, Part 4). Galileo, who probably coined the term aurora borealis to designate the phenomenon, wrote in a 1619 text signed by his pupil Mario Guiducci that the phenomenon “has no other origin than that a part of the vapor-laden air surrounding the Earth is for some reason unusually rarefied, and being extraordinarily sublimated has risen above the cone of the Earth’s shadow so that its upper parts are struck by the sun and made able to reflect its splendor to us, thus forming for us (this northern dawn – questa boreale aurora)” (Siscoe (1986), quote taken from Drake and O’Malley (1960, p. 53)). Thus, while he considered, like Aristotle, that the material cause was due to vapors emanating from the Earth, he attributed the light of the aurora borealis, not to an inflammation, but to the reflection by these vapors of the sunlight. A similar explanation was provided by Pierre Gassendi, witness of the aurora borealis in 1621, last insisting on the planetary character of the phenomenon, related, according to him, to a particular interior arrangement of the terrestrial globe expelling vapors through a significant part of its surface (Bernier 1684, p. 266). René Descartes in his essay Les Météores published in 1637 advanced three possible explanations of the aurora borealis:
The first is that there are many clouds in the air, sufficiently small to be taken for so many soldiers; and falling onto one another, these enclose enough exhalations to cause a quantity of small flashes, and to throw small fires, and perhaps to cause small noises to be heard, by which means these soldiers seem to do battle. The second cause is also that there are such clouds in the air; but instead of falling on one another, they receive their light from the fires and lightning flashes of some large storm, which occurs so far away that it cannot be perceived at that location. And the third cause is that these clouds, or some other more southern ones, from which they receive their light, are so high that the rays of the sun reach right to them (Descartes 1965, p. 331).
The first explanation, which assimilates the aurora borealis to a small storm, is closely inspired by the Aristotelian vision, although differing on the mechanism of the inflammation, associated in Descartes’ work to a movement occurring within the atmosphere. The third explanation is directly inspired by the idea of Galileo and Gassendi, the second being an intermediate hypothesis, the vapors transmitting a light which is not that of the sun, but comes from a distant storm.
Bertholon detailed no less than 12 possible explanations for the aurora borealis, proposed during the 18th century. Edmond Halley, the first to take a scientific stand after the marked resumption of the aurora in 1716, published in 1717 an explanation based on the idea that the aurora borealis was the result of magnetic matter circulating in the great Earth magnet, inspired by Descartes’ magnet theory (Halley 1717). After having exposed, in the same article, the theory of Aristotelian inspiration of exhalations igniting in the atmosphere, which he thought could not explain the considerable geographical extension of the aurora, he advanced his own explanation according to which it was the magnetic subtle matter, which he supposed to leave by the boreal pole of the Earth and circulate in the ether towards its southern pole, which generates the luminous phenomena of the aurora at high latitude. Jean-Jacques Dortous de Mairan, a few years later, conceived a system of the aurora based on the idea that the subtle matter at the origin of the Northern Light came from the sun, whose atmosphere, to which he attributed with Jean-Dominique Cassini the origin of the zodiacal light and which could extend beyond the orbit of the Earth, precipitated in the subtle air constituting the upper atmosphere of the Earth. By mixing with the atmosphere, the solar matter stratified, and produced the luminous structures of the aurora. Mairan’s treatise on the aurora borealis, completed in 1731, was published two years later (de Mairan 1733). It is around these two great systems, as well as that of the ignition of the dry exhalations inherited from the meteorology of Aristotle which remained defended by many scientists until the middle of the century, that the scientific thought of the time developed as regards sciences of the atmosphere and meteorology. A fourth system was proposed by Leonhard Euler about 15 years later (Euler 1746), using an effect of the thrust of the sun’s rays on the particles of the upper atmosphere, these rays being supposed to expel particles towards space in the same way that they push back, according to Euler, the envelopes of the comets to form their tails. Bertholon mentioned other theories developed at the same time, inspired by the ideas of Galileo or Gassendi who saw in the sun the source of auroral radiation. Thus, Abbot Hell of the Observatory of Vienna supposed an effect of the particles of ice in suspension in the atmosphere reflecting and refracting the rays of the sun or of the moon as it occurred in the parhelias. Others appealed to the snow and ice cover of the polar regions, which would reflect towards the upper layers of the atmosphere the low-angled light of the sun (placed just below the horizon), these layers reflecting in their turn this light towards the observer located at the surface of the Earth. But, in the second half of the 18th century, all these systems were supplanted by the hypothesis of an electrical origin for the auroras, this on the basis of the similarities of texture and color of the auroras with the lights generated within previously electrified enclosures. John Canton, in 1753, published the first electrical model of the aurora borealis, defending the idea that the aurora was produced by a discharge between positively and negatively electrified clouds passing through the upper atmosphere, whose electrical resistance was lower (Canton 1753). Bertholon also cited the work of Benjamin Franklin and his own, on the hypothesis of an effect of electricity. It was not until the end of the 19th century, with the discovery of the precipitation of solar particles, that the true mechanism, involving the solar wind particles, the Earth’s magnetic field and the circulation of solar particles along the field lines, came to synthesize the explanations proposed by Halley, Mairan and Canton.
In his treatise of 1733, Mairan argued that, if his system was correct, namely if the aurora borealis were the result of the precipitation of matter from the solar atmosphere in the terrestrial atmosphere, the aurora must be more frequent when the Earth is closer to the sun, that is, in the vicinity of its perihelion on its orbit around the sun, around the winter solstice, and when the northern hemisphere of the Earth points in the direction of the movement of the Earth on its orbit, in the period between the summer solstice and the winter solstice, catching the solar matter head on. He believed that future observations of the aurora borealis would test the validity of his hypothesis. In the second edition of the treatise, published in 1754, applying the method traced 20 years earlier, he reviewed the existing observations of aurora borealis, in particular those which intervened since the publication of his first treaty. His goal was to statistically analyze the frequencies of appearance of auroras in the vicinity of the perihelion (December–January) and aphelion (June–July) of the Earth on its orbit around the sun within the framework of his system, a system from which, according to him, “results the constant connection of the Aurora Borealis & of its appearances, with this luminous fluid or illuminated by the Sun, which extending sometimes until the Earth & beyond, must by the laws of the gravitation, fall in the terrestrial Atmosphere, & produce there this Phenomenon”. He began by analyzing the auroras listed by a professor of philosophy in Helmstadt, Germany, Jean-Nicolas Frobès, who published in 1739 a catalog of 796 auroras observed between 500 and 1739, of which three quarters were later than 1716, thus describing the advantage of the statistical approach which, by the multiplication of observations, as well as their results as their interpretations, smoothed and finally canceled the biases related to the measurements and individual appreciations:
It is that the principle of frequency which we are talking about being true, all these differences disappear on the great masses of time and numbers; everything finally compensates itself according to the Doctrine of Chance, and the sought-after relationship manifests itself. If the way of seeing or judging, of an Observer, of a Historian, his attentions, his prejudices, his superstition even, making him multiply or omit certain Phenomena, contrary dispositions in another will make him reject what this one has admitted, & retain what he had rejected […] If the long twilights of Summer, & longer in one climate than in the other, cause us to lose some small Aurora Borealis, the dark nights of Winter, & whose length is relative to these climates in inverse proportion to the days & twilights, rob us of others of the same kind. […]
It is thus from this very diversity, of times, of countries & of writers, & from these great masses of years, of observations & of numbers, that our inductions on the correspondence of which it is a question, will draw their greatest forces (de Mairan 1754, pp. 486–487).
He thus analyzed the series of observations which were delivered to him by several observers of aurora borealis from various European countries, whose references he provides. Two hundred and thirty-three observations came from Joseph-Nicolas Delisle, director of the Imperial Observatory of St. Petersburg, that in the following we will call for simplicity St. Petersburg Observatory, where they were realized by himself and his colleagues in the Observatory, Friedrich Christoph Mayer and Georg Wolfgang Krafft. The 57 aurora borealis observed by the younger brother of Delisle, Louis de La Croyère, also posted in St. Petersburg, during his trip to Siberia in 1727–1730, were not used by Mairan in his analysis because they were taken, according to him, at too high a latitude, in extreme conditions of the diurnal cycle of sunshine likely to bias the statistics of the observed auroras. Two hundred and twenty-four observations of auroras were provided by Anders Celsius, director of the Astronomical Observatory of Uppsala, some observed by him, others by his Swedish colleagues. One hundred and six were made by Christfried Kirch, director of the Royal Observatory of Berlin and 91 by Johann Friedrich Weidler from Wittenberg, a city located about 100 km southwest of Berlin. Eighty-eight observations were made by Eustachio Zanotti, successor of Eustachio Manfredi, another aurora observer, at the direction of the Astronomical Observatory of Bologna and Jacopo Bartolomeo Beccari of the same city. Other observations were published in London in 1749 by Thomas Short, listing 148 aurora borealis. Among all these observations, Mairan eliminated those which corresponded to the same aurora seen by various observers, which occurred frequently taking into account the very great height of the phenomenon, on average 175 leagues, that is, 700 km, which meant that it could be seen from very far, the aurorae taking place most often between 400 km and 1,200 km of altitude (de Mairan 1754, pp. 433–434). Examining thus the cases of more than 2,000 aurorae, in great majority posterior to 1716, Mairan deduced that the aurorae were more frequent during the winter months, when the Earth is closer to the sun, while noting the bias which could come from the fact that summer is also the period during which the nights are the shortest, the phenomenon being then likely to be masked by the greater ambient luminosity.
The question of the capacity of a system to be tested by the collection of observations over time, an essential asset of Mairan’s aurora borealis theory, was important, and was part of a debate that shook the entire first half of the 18th century around the question of the spirit of the system, in this period of reversal of the deductive mechanistic approach inherited from Descartes to the benefit of the inductive approach based on the results of observation and experience alone, as advocated by the proponents of English empiricism led by Isaac Newton. As soon as he took office as Permanent Secretary of the Académie Royale des Sciences in 1699, Bernard le Bovier de Fontenelle in his foreword to the Histoire de l’AcadémieRoyale des Sciences2 (Fontenelle 1699), which we will refer to in the following as simply the Histoire, advocated the patient accumulation of observations as a prerequisite to the elaboration of any system, “because systematic physics must wait to build buildings until experimental physics is in a position to provide it with the necessary materials”. For Fontenelle, as for Mairan, who expresses it perfectly in his foreword to the dissertation on ice, Dissertation sur la Glace (de Mairan 1749), the system is indeed the accomplished form of knowledge (Mazauric 2007), but it can in no way be posited a priori, since it must on the contrary result from the observation of phenomena. To the “spirit of system” inherited from Descartes, which he challenged, Jean le Rond D’Alembert opposes in his preliminary speech of the Encyclopédie of 1751 a “systematic spirit” consisting of “reducing, as far as possible, a large number of phenomena to a single one that can be considered as the principle” (D’Alembert 1893, p. 23), in which the system is not situated upstream of the phenomena that we seek to explain, but at the articulation between these phenomena, which we must compare and study in a reflective manner. This question of systems forms an important background of the scientific life of the time, as we relate it in this work.
Almost all of the aurora observers quoted by Mairan in his memoir of 1754, for the most part also involved in daily measurements of meteorological parameters (temperature, pressure, wind speed), were in regular contact with each other, as we will describe in the pages of this book. Thus, Joseph-Nicolas Delisle maintained a close correspondence with Kirch and Celsius, and also exchanged regularly with Zanotti and Weidler, during the long years that he spent in St. Petersburg. Celsius, during his European journey of 1732–1737, which he concluded by his participation in the expedition led by Pierre Louis Moreau de Maupertuis in Lapland to measure the shape of the Earth, made observations with Kirch in Berlin, then with Manfredi in Bologna, went to Wittenberg to meet Weidler, then spent time in Paris, where he met Delisle’s sister (the latter was then in St. Petersburg), who occasionally interacted with the Académie Royale des Sciences and the Collège Royal of which her brother remained a member despite his absence. In Padua, Celsius met Giovanni Poleni and transmitted to him his observations of aurora borealis. Poleni, a partisan of Mairan’s system, aware of the latter’s expectations, tabled the observations of his Swedish colleague and transmitted them to Mairan, who then met directly with Celsius during his time in Paris. Delisle realized thermometers that he sent throughout Europe, in order to allow temperature measurements that could be compared from one country to another. In the early 1740s, Celsius, with his associate Olof Hiorter, observed magnetic needle agitation during certain aurora borealis, and the needle’s declination measurements, hitherto mostly dedicated to mapping declination in sight to improve navigation, also taking an interest in the interpretation of the aurora borealis.
These observers, on the whole, did not take explicit sides on the system of the aurora which they favored, and even, for some, like Celsius, refrained from doing it, limiting themselves to the systematic and patient recording of the data with a view to future scientific work, work of which the statistical analysis carried out by Mairan in 1754 is the perfect illustration. We know that Weidler, as well as François de Plantade, who observed auroras in Montpellier, were supporters of Halley’s system. Mayer, in St. Petersburg, favored the hypothesis of the inflammation of sulfurous materials. Poleni, who observed some auroras from Padua, and many other scientists in Europe were seduced by Mairan’s cosmo-atmospheric system. They were all astronomers and, as such, dedicated most of their time to the observation of planets and stars, especially their conjunctions (eclipses of the moon and the sun, occultations of stars by the moon or of its satellites by Jupiter, transits of Mercury…), as well as comets in a period where the verification of the conformity of the trajectories of comets to the laws of Newton was a major subject for Newtonians as Delisle or Celsius. These astronomers, in their observatories, were also in charge of meteorological observation. This included the aurora borealis, which until then had been considered a meteorological phenomenon in the Aristotelian tradition. Because of the long nights spent observing, they were led to witness the aurora borealis, which were particularly frequent at the latitudes of Uppsala or St. Petersburg. Their observation instruments allowed them to angularly characterize the structures of the aurora borealis (arcs, jets, etc.) relative to the surface of the Earth and to the direction of the geographical north, leading in particular to estimates of the height of the phenomenon, thanks to parallax measurements made from distant observations of the same structure, or to idealized models, such as Mayer’s, allowing the height of the aurora to be estimated from a measurement in a single point. The estimated heights were considerable (several hundreds, even more than a thousand kilometers), suggesting an atmosphere much higher than it was believed in the previous century (typically less than 100 kilometers; see Chassefière 2021a, Chapter 7), and leading some scholars like Euler to attribute to it a purely cosmic origin.
These aurora observers all had important responsibilities in the then emerging institutional system of scientific academies and observatories in European countries and in Russia. Celsius was the one who, after his European trip, took over the Royal Society of Sciences of Uppsala and its Observatory project. Manfredi was the founder, at the end of the previous century, of the Accademia degli Inquieti on which the Academy of Sciences of the Institute of Bologna was built and its Observatory, whose directors were Manfredi and later Zanotti. The Kirch family, Gottfried Kirch and his wife Maria Winkelmann as well as their son Christfried Kirch and his sisters, played an important role in the scientific production of the Royal Observatory of Berlin, the centerpiece of the Academy founded by Gottfried Wilhelm Leibniz in the same city at the turn of the century, of which Gottfried Kirch and later Christfried were directors. As for Joseph-Nicolas Delisle, he was the major architect of the creation ex nihilo of an astronomical observatory in St. Petersburg, within the framework of the Imperial Academy of Sciences wanted by Peter the Great, and set up with the help of Christian Wolff, a follower of Leibniz, on a scheme identical to that of the Royal Academy of Sciences of Prussia that we will often call for simplicity the Academy of Berlin. To these actors of the observation, it was necessary to join Halley and Mairan, the creators of the two great systems in dispute with the Cartesian vision of the Meteors, the first having played an essential role in the conduct of the Royal Society of London and its Observatory (as secretary of the society from 1713, then, from 1720, as director of the Royal Observatory of Greenwich), the second having taken in 1741, for three years, the succession of Fontenelle to the perpetual secretariat of the Académie Royale des Sciences de Paris. This group of scholars alone covered the main academies of the time (London, Paris, Uppsala, Berlin, Bologna, St. Petersburg), and many of its members played prominent roles in the creation, or the direction, of these academies and their observatories. These observatories constituted, until the middle of the 18th century, the essential of the establishments of importance in astronomy of Europe.
The institutionalization of astronomy on the European continent was initiated in the second half of the 17th century through the creation of two great observatories: the Observatoire Royal de Paris in 1667 within the framework of the new Académie Royale des Sciences de Paris (Maury 1864) founded the year before; and the Royal Observatory of Greenwich in 1675 within the framework of the Royal Society of London (Mailly 1867) founded in 1660. In the following century, many other academies were founded: the Royal Academy of Sciences of Prussia in Berlin in 1700, the Royal Society of Sciences of Uppsala in 1710, the Academy of Sciences of the Bologna Institute in 1714, the Imperial Academy of Sciences of St. Petersburg in 1725, and about 15 others in the course of the 18th century (Sigrist 2013). The Academies of Paris, London, Berlin, Uppsala, Bologna and St. Petersburg, which we will study in particular in this work, all of which had astronomical observatories as an integral part of their structure, gathered between 30 and 40% of the European astronomers of the time, whose number approached half a thousand in the second half of the 18th century (ibid.). These astronomers did not observe only in the observatories attached to these academies, far from it. In Paris alone, about 10 private observatories were used by astronomical academicians (Passeron 2013). At the European level, more than 60 mobile quadrants were delivered in the 17th and 18th centuries in about 50 different observatories (Turner 2002), translating the existence of several tens of valuable observatories at that time. The observation of the meteorological parameters, as well as the aurora borealis, constituted in the public observatories attached to the academies activities of service, recognized and to which were devoted means in terms of men and material.
The aurora borealis was an emblematic example of an object, by nature observable simultaneously by observers from different countries, the observation of which by witnesses several hundreds or thousands of kilometers away was necessary to precisely characterize its morphology and dimensions, and as such calls for the establishment of coordinated observation networks. Contrary to the astronomical phenomena, whose observation required coordinated campaigns on a global scale, for example, to measure the parallaxes of the moon, the planets or the sun providing their distances, the aurora borealis are unpredictable events and thus required constant monitoring, and the accumulation of observations in large numbers, especially for statistical purposes as we have seen. The cooperative aspect of the observation of the aurora borealis constitutes an important dimension, even if it represented only a relatively secondary aspect of the activity of the astronomers of the time, whose principal field of expertise was that of astronomy and of the prediction of the trajectories of celestial bodies, in particular in this period of penetration of Newtonian mechanics, of which some, like Delisle or Celsius, set themselves the goal of providing observational validation. The aurora borealis was (almost) never mentioned in Delisle’s correspondence with his European interlocutors, the reason being that their observation could not give rise to any calculation intended to predict their course in an unequivocal manner, as is the case with the trajectories of celestial bodies. The system proposed by Mairan, using the sun and the Earth’s orbit as partial determinants, nevertheless contrasted with this state of affairs by giving the aurora borealis an astronomical dimension, providing relatively clear validation criteria. The present work, based on the circle of about 15 astronomers providing aurora observations previously described, is not mainly concerned, as we have said, with the science of the aurora borealis, which has already been the subject of lengthy developments in a previous book (Chassefière 2021a), but rather with the human, institutional and philosophical context in which these aurora observing astronomers evolved.
A particularity of the aurora borealis phenomenon, in this first half of the 18th century which saw the penetration of Newtonianism on the continent, was that the systems proposed to describe it did not fit into a clear duality between Cartesian and Newtonian influences. The system proposed by Halley, a close associate of Newton, took up Descartes’ magnet theory, while that of Mairan, defender of Cartesian vortices, claimed the inclusion of the mathematical law of gravitation proposed by Newton to define the size of the accretion zone of solar matter by the Earth on its orbit, even if this particularity did not constitute a central aspect. Pieter van Musschenbroek, a Dutch physicist professing the ideas of Newton, defended the Cartesian system of inflammation of exhalations. Many aurora observers, as mentioned, did not take sides in favor of a particular system. The aurora borealis is not by itself, if we stick to the question of its observation, an object cleaving in terms of belonging to such or such philosophical school, the cooperation required to observe and characterize it largely prevailing, and welding communities of various obediences. The development of the Mairan system, in the second half of the 1720s, was nevertheless part of a particular period of marked opposition between Cartesians and Newtonians. Several authors, such as Pierre Brunet (1970) and later John Bennett Shank (2008), described the period that began in 1727 and lasted until the end of the 1730s as a time of strong Cartesian reaction to the increasing penetration of Newtonianism. For the former, the Cartesian reaction began at the beginning of the 18th century, with opposition becoming increasingly intense from 1727 onwards, whereas for the latter, the process did not really begin until 1715 due to a publicly displayed rejection of Descartes by the Newtonians, Fontenelle’s praise of Newton in 1727 amplifying the awareness of the Newtonian threat by the Cartesians of the French Academy (a synthesis of the periodizations proposed in the literature can be found in Crépel and Schmit (2017, pp. 21–40)). In this particular context, Mairan’s system, which appealed to subtle matters, was, as we shall clearly see, established by Fontenelle, secretary of the French Academy and uncompromising defender of the theory of vortices, as a monument of Cartesian thought against the growing influence of Newton’s ideas.
In Chapter 1, we question the silence maintained over several decades in the volumes of the Académie Royale des Sciences on Halley’s aurora borealis system. This silence was reinforced at the end of the 1720s by the rejection by the Academy of a memoir of the Société Royale des Sciences de Montpellier, written after the great aurora borealis of 1726 by François de Plantade, proposing a system similar to that of Halley’s. The arguments put forward against Plantade to justify the rejection of his memoir by various Parisian interlocutors did not seem to be able to explain the decision taken, firstly because Plantade, a recognized scientist and founder of the Société Royale des Sciences de Montpellier, explained that his system differed sufficiently in detail from that of Halley’s to deserve to be exposed in the volumes of the Parisian memoirs. Secondly, the crisis triggered by the rejection of the memoir threatened the organic link established in 1706 between the two institutions, a consequence far more serious than the publication of a memoir whose descriptive part at least had been judged of good quality. Based on an analysis of the facts, and of the positions of the main actors involved, namely the perpetual secretary Fontenelle, and Mairan himself, who was very close to Fontenelle, and by placing the episode in the context of the intensification of scientific relations between the Académie Royale des Sciences and the Royal Society of London, we suggest that the arguments communicated to Plantade by various Parisian interlocutors to justify the rejection of his memoir masked a “political” motivation, in the sense of the defense of the Cartesian sphere of influence, in a period of hardening conflict between Cartesians and Newtonians, the affirmation of Mairan’s aurora borealis system constituting a piece of the Cartesian counter-offensive.
Chapter 2 presents the life and study trajectory of Joseph-Nicolas Delisle, an astronomer and academician invited to St. Petersburg, the new capital of Russia, by Peter the Great to take the direction of an Astronomical Observatory within the framework of the new Imperial Academy of Sciences. He observed more than 200 aurora borealis in the decade following his arrival in 1726. The context of the publication of these observations in 1738 within the framework of the Russian Academy of Sciences is surprising in more than one way. The isolated character of this publication, in which were announced others which needed to succeed it in order to carry out a Celestial History of all the European astronomical observations, and which, however, never appeared, the late character of the publication of the experiments of diffraction of light carried out 20 years earlier in Paris by Delisle, published in the same work, in a collection where they were not meant to appear, the questioning of the reasons which pushed Delisle to accept the tsar’s offer to come and settle in Russia, are so many questions which deserve to be examined. The first interests of Delisle, an essential actor of the diffusion of the Newtonian theses on the old continent in the first half of the 18th century, were in celestial mechanics and the astronomical surveys, essentially of eclipses, intended to measure the position of geographical locations for cartographic purposes. This is the main reason why, even before the mission of setting up an observatory, he was invited to Russia. We show to what extent, in the years 1715–1725, Delisle’s scientific projects in France were thwarted because of his Newtonian convictions, probably influencing his decision to leave France. This chapter, although moving away from the theme of the aurora borealis, announces the following one devoted to the Imperial Academy of St. Petersburg, which brings us back to it in part.
Chapter 3 focuses on the creation of the Imperial Academy of Sciences in St. Petersburg and the difficulties it encountered in its early days. We start in this study using a particular fact, which is the conference given by Christian Wolff in his city of Halle one week after the great aurora borealis of March 1716, addressing the citizens of his city in order to give them a rational explanation of the phenomenon. Many of the scientists invited to join the St. Petersburg Academy were recommended by Wolff, and we illustrate Wolff’s influence on the work achieved at the Academy by taking the example of his follower Friedrich Christoph Mayer, an observer of the aurora borealis, partner of Joseph-Nicolas Delisle at the Observatory, who gave up the observation of the aurora borealis because he did not believe in his observations, which indicated an altitude of the auroral matter that was one hundred times higher than the one predicted by the system he defended, inspired by that of Wolff, and which attributed a stormy origin to the phenomenon. We show how Leonhard Euler, in contrast to Mayer, whom he worked with for several years at the St. Petersburg Observatory, solved the paradox by proposing 20 years later a new system of the aurora borealis, placing it very above the atmosphere. We discuss the scientific attitudes of the two men with regard to their respective schools of thought. We then examine, on a broader level, the evolution of the young academy under the sometimes contradictory effects of Wolffianism and Newtonianism and the obstacles encountered, in particular religious censorship, as well as the serious dysfunctions in the administrative management of the Academy, which, combined with the general political instability which reigned then in Russia, provoked the premature departure of several scientists of great stature, like Daniel Bernoulli, Euler and finally Delisle. We conclude by explaining the dynamics of the evolution of the Imperial Academy of St. Petersburg throughout the 18th century which, in spite of the numerous difficulties encountered, finally led to a Russian scientific community, notably astronomical, emerging towards the end of the century.
More than 200 observations of auroras among those analyzed by Mairan in 1754 were made by Anders Celsius, who published a compilation of them during his European trip, while he was in Germany, and it is to Celsius, and to his asserted international dimension, that Chapter 4 is devoted. In addition to his observations of auroras, Celsius discovered the relation between aurora borealis and magnetism by highlighting the irregular variation of the magnetized needle during the aurora, documented very precisely by his assistant Olof Hiorter in a series of thousands of measurements carried out at the beginning of the 1740s, some of which corresponded to those of the clockmaker George Graham in London. Celsius traveled for five years in Europe in the mid-1730s and established a network of correspondents among the best astronomers of the time. In addition to the astronomical observation itself, notably on the problem determining longitudes, or around the observation of comets and the calculation of their orbits according to the laws of Newtonian mechanics, then defended by a few scientists, including Joseph-Nicolas Delisle, networks of scientists were formed around the observation of the aurora borealis, variations in the declination of the magnetic needle or meteorological parameters. Celsius, like Delisle, was a very active member of these different networks, which were strongly interconnected. In this chapter, we are interested in the life of Celsius and the observational campaigns in which he was involved in different capacities, as well as in the genesis of the Royal Society of Uppsala and its Observatory, as well as their counterparts in Stockholm, of which Celsius was the main architect, in the context of a chronic lack of means in terms of infrastructure and equipment. It was only in the middle of the 18th century, only two years before the death of Celsius, that the Astronomical Observatory of Uppsala was officially established, following three decades of persistent efforts by Swedish astronomers to observe, at all costs, and to try to obtain from the political authorities, with more or less success, means commensurate with their ambitions.
During his European trip, Anders Celsius noticed the astronomical competence of the sisters of the astronomers he visited: Christfried Kirch first in Berlin, then Eustachio Manfredi in Bologna. In Paris, he stayed with the sister and mother of Joseph-Nicolas Delisle, then in St. Petersburg. Thus, a large number of the astronomers of the 18th century involved in the observation of the aurora borealis, and more generally in astronomical observation, were members of astronomical households, informal units in which men and women shared on an equal footing, at least within the household, the work of observation, the men being the only ones entitled to publicly exercise the profession of astronomer because of the gender conventions of the time. Chapter 5 is devoted to the description of these households. This was a period of establishment of academies of great fame, as in Berlin or Bologna, and the private circles constituted by the astronomical households, and even the still relatively informal embryos of future academies at work in the Italian salons, coexisted for some time with the new institutions, in ways that varied from one country to another. In this chapter, we analyze the constitution and the modalities of operation of the Kirch, Manfredi and Delisle households, for the first two were in close connection with the academies and astronomical observatories born in Berlin and Bologna from the Enlightenment approach, aiming at developing experimental science, whose birth and rise to power phase we describe. We analyze the similarities and differences between these different households, and the different institutions to which they were linked. We extend, in the case of Italy, the question of gender to other women scientists than the Manfredis, women whose careers were emblematic of the Italian specificity in this field.
The aurora borealis in itself is not the main subject of the book, which uses it rather as a device for the narrative, a particular thread linking the different actors, this one being able to take more density in certain passages, as in Chapter 1, about the quarrel which opposed Paris to Montpellier about the refused memory of Plantade, or in Chapter 3, involving the renunciation of Mayer to the observation of the aurora borealis. But it is to the personalities or to the life paths of some of the outstanding scientists who observed and studied the phenomenon, and to the institutions (academies, observatories) within which these scientists evolved, that the book is above all devoted. These scholars, for the most part, were primarily interested in astronomical observation, and even in meteorology activities that also required the networking of instruments and methods, the observation of the aurora borealis, and even the elaboration of systems supposed to explain them, constituting only a limited part of their activity. Speaking of men, of the ideas they defended, of the institutions they modeled, it is thus not possible, nor even desirable, to restrict the scientific field of our narration to the sole question of the aurora borealis. The question, for example, of the role of women in the production of knowledge, is much wider, concerning all the sectors of astronomy and beyond science in general. The reading of the present work must be undertaken as a retrospective journey through the Europe of the first aurora observers, during which we will often cross paths with the same scientists, but each time in different contexts, or following different angles, thus trying to account for the swarming of ideas and encounters that constituted the development of experimental science in the pivotal era of the Enlightenment.
Notes
1
The
Dictionnaire de Physique
, published in 1793, is the first volume of a set of four encyclopedias of which the second, third and fourth volumes are called
Encyclopédie méthodique
, published, respectively, in 1816, 1819 and 1822.
2
Each volume, usually one per year, of the proceedings of the Académie Royale des Sciences (French Royal Academy of Sciences), consists of a series of memoirs (the
Mémoires de Mathématiques
and the
Mémoires de Physique
of the Académie Royale des Sciences de Paris (Royal Academy of Sciences of Paris) preceded by a section composed of articles by Fontenelle introducing and popularizing the science presented in the memoirs, which will be called the
Histoire
without further precision in the rest of this book), and followed by a section devoted to the Eulogies of the deceased academicians.
1The Aurora Borealis Issue of the Affirmation of the Cartesian Mechanism and the Dispute Between Paris and Montpellier: The French Choice
1.1. Introduction
We previously evoked the two great systems of the aurora borealis seen at the beginning of the 18th century, in dispute with the Aristotelian vision of the inflammation of dry vapors taken over by René Descartes; one by Edmond Halley published in 1717, invoking an effect of the magnetic matter circulating in the great Earth magnet, the other by Jean-Jacques Dortous de Mairan, published in 1733, appealing to the matter of the solar atmosphere precipitating in the high layers of terrestrial subtle air. However, between publication dates of the two systems, in a period where the aurora borealis occurred regularly giving place, almost annually, to articles in the Mémoires de l’Académie Royale des Sciences that we will call hereafter simply the Mémoires, systematically taken up and commented by its permanent secretary Bernard le Bovier de Fontenelle in the columns of the Histoire de l’Académie Royale des Sciences, Halley’s system is never quoted, except, in passing, in Mairan’s treatise of 1733, for a brief criticism in half-tone. The fact that Halley’s system is not mentioned in the French Academy’s volumes, notably in the Histoire, whose role was to contextualize and synthesize the science presented in the Mémoires, was not only by omission. In 1727, a memorandum of François de Plantade communicated by the Société Royale des Sciences de Montpellier to the Parisian Académie des Sciences for publication in its Mémoires, in accordance with the agreements which bound the two institutions, in which Plantade related the aurora of 1726 and proposed a system close to that of Halley’s, was refused by the Academy, causing a crisis between the two institutions. In a first step, we will briefly describe the two major systems in question of the aurora borealis. In a second step, we trace the history of the aurora borealis in the volumes of the Histoire and Mémoires between 1717 and 1733. Then, we devote three specific sections to the actors of the considered facts: the first to the Montpellier inhabitants (Plantade at the Société Royale des Sciences de Montpellier), the second to the Parisians (Fontenelle and Mairan at the Académie Royale des Sciences), the third to the Londoners (Hans Sloane and Halley at the Royal Society). Finally, we examine the question of the silence of Halley’s hypothesis in the French community, and the rejection of Plantade’s memoir for publication in the French Academy’s memoirs, which we propose constitute elements of an affirmation strategy of Cartesian thought in a period of tension generated by the progressive penetration of Newtonianism on the continent.
1.2. The two main systems of the aurora borealis
The first synthetic description of these two systems, completed by that of the system proposed some 20 years later by Leonhard Euler, was published by Morton Briggs (1967). More recently, Stéphane Le Gars has focused on Mairan’s theory, discussed in relation to Halley’s (Le Gars 2015), and these systems, as well as others developed in the 18th century, have been described in a previous book (Chassefière 2021a). A common feature of the memoirs of the period reporting on the aurora borealis was the detailed description, judged “Baconian” by Briggs, of the forms and colors of the aurora, as well as their evolutionary dynamics in the course of the same aurora. This luxury of detail, present in Halley and Mairan’s work, and found in many others, was considered necessary in order not to miss a possible new fact, which would help provide an explanation of the phenomenon. Briggs quotes a Harvard professor, Isaac Greenwood, who in 1731 gave a detailed description of the smallest details of the aurora observed at a temporal resolution of 5–10 minutes over a period of several hours. The systems proposed by Halley and Mairan both break with previous theories attributing the cause of the aurora to exhalations igniting in the atmosphere.
1.2.1. Halley’s system
Halley, who witnessed the great aurora of March 1716, proposes in Philosophical Transactions
