Category Archives: History of Astrology

The emergence of modern astronomy – a complex mosaic: Part XVII

As I stated earlier in this series only a comparatively small number of astronomers accepted the whole of Copernicus’ theory, both cosmology and astronomy. More interestingly almost none of them had any lasting impact during the final decades of the sixteenth century on the gradual acceptance of heliocentrism. Although he appears to have abandoned Copernicus’ astronomy later in life, Rheticus did have a strong impact with his Narratio Prima(1540), which through its various editions was the first introduction to the heliocentric hypothesis for many readers. Two others, whose impact was principally in the seventeenth century, were Kepler and Galileo, who will be dealt with later. However, one astronomer who did play an important role in the sixteenth century was Michael Mästlin.

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Michael Mästlin portrait 1619 artist unknown

Michael Mästlin (1550-1631) stood at the end of a long line of important Southern German astronomers and mathematicians. A graduate of the University of Tübingen he was a student of Philipp Apian (1531–1589),

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Philipp Apian, artist unknown Source: Wikimedia Commons

 

who was a student of his more famous father Peter Apian (1495–1552) in Ingolstadt. Peter Apian had studied under Georg Tannstetter (1482–1535) in Vienna, who had studied under Andreas Stiborius (c. 1464–1515) and Johannes Stabius (1450–1522) first in Ingolstadt then in Vienna. In 1584 Mästlin succeeded his teacher Philipp Apian as professor for astronomy and mathematics at Tübingen. An active astronomer since the beginning of the 1570s Mästlin was regarded as a leading German astronomer and consulted by the Protestant princes on matters astronomical, astrological and mathematical.

Mästlin represents the transitional nature of the times probably better than any other astronomer. His Epitome Astronomiae (1582), a university textbook, which went through a total of seven editions, was a standard Ptolemaic geocentric text that he continued to teach from until his death in 1631.

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However, at the same time he taught selected students the fundaments of Copernican heliocentric astronomy. Earlier accounts claimed that he did this in secret but all of the available evidence suggests that he did so quite openly. This quasi revolutionary act of teaching famously produced one significant result in that Mästlin introduced Copernican astronomy to the young Johannes Kepler, who would go on to become the most important propagator of heliocentric astronomy in the early seventeenth century.

One subject on, which the German Protestant princes consulted Mästlin was the proposed Gregorian calendar reform from 1582. Mästlin launched a vitriolic polemic against it largely on religious grounds with his Gründtlicher Bericht von der allgemeinen und nunmehr bei 1600 Jahren von dem ersten Kaiser Julio bis jetzt gebrauchten jarrechnung oder kalender (Rigorous report on the general and up till now for 1600 years used calculation of years or calendar from the first Caesar Julio) (1583). The Protestant princes accepted his advice and as a result didn’t adopt the new calendar until 1700.

On the other side of the religious divide the man charged by the Pope to promote and defend the new calendar was the Jesuit professor of astronomy and mathematics at the Collegio Romano, Christoph Clavius (1538–1612).

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Christoph Clavius. Engraving Francesco Villamena, 1606 Source: Wikimedia Commons

Although Clavius was a convinced defender of the Ptolemaic system until his death, he did play a central role in the developments that led to the eventual acceptance of the heliocentric system. The Catholic universities in the last quarter of the sixteenth century still didn’t really pay the mathematical disciplines much attention and their teaching of astronomy had not really progressed beyond the High Middle Ages. Clavius introduced modern mathematics and astronomy into the Jesuit educational reform programme, following the fundamental principle of that programme, if you want to win the debate with your non-Catholic opponents you need to be better educated than them. Many Jesuit and Jesuit educated mathematicians and astronomers, who came out of the pedagogical programme established by Clavius, would, as we shall see, make significant and important contributions to the developments in astronomy in the seventeenth century.

Clavius was also the author of a number of excellent up to date textbooks on a full range of mathematical topics. His astronomy textbook In Sphaeram Ioannis de Sacro Bosco commentarius, the first edition appearing in 1570 and further updated editions appearing in 1581, 1585, 1593, 1607, 1611 and posthumously in 1618, was the most widely read astronomy textbook in the last decades of the sixteenth and early decades of the seventeenth centuries. It was strictly Ptolemaic but he presented, described and commented upon Copernicus’ heliocentric hypothesis. Although he showed great respect for Copernicus as a mathematical astronomer, he of course rejected the hypothesis. However, anybody who read Clavius’ book would be informed of Copernicus work and could if interested go looking for more information. One should never underestimate the effect of informed criticism, and Clavius’ criticism was well informed, for disseminating a scientific hypothesis. Many people certainly had their first taste of the heliocentric hypothesis through reading Clavius.

Another group who had a positive impact on the propagation of the heliocentric hypothesis in the last quarter of the sixteenth century was the so-called English School of Mathematics. Whilst Robert Recorde (1510–1558) and John Dee (1527–c. 1608) were not committed supporters of Copernicus, they did much to spread knowledge of the heliocentric hypothesis. As we have already seen John Feild (c. 1520–1587) was a declared supporter of Copernicus but as his Copernican ephemerides proved no more accurate than the Ptolemaic ones his influence diminished. Not so Dee’s foster son Thomas Digges (c. 1546–1595).

His 1576 edition of his father’s A Prognostication everlastingcontained an appendix A Perfit Description of the Caelestiall Orbes according to the most aunciente doctrine of the Pythagoreans, latelye revived by Copernicus and by Geometricall Demonstrations approved, which is an annotated translation of part of the cosmological first book of De revolutionibus into English, which continued to have an impact on English readers long after Digges’ demise.

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Source: Linda Hall Library

Thomas Harriot (c. 1560–1621) was another, who was committed to the heliocentric hypothesis.

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Portrait often claimed to be Thomas Harriot (1602), which hangs in Oriel College, Oxford. Source: Wikimedia Commons

His biggest problem was that he published none of his scientific or mathematical work but he was well networked and contributed extensively to the debate through correspondence. The influence of this group would, as we will see, have an impact on the early acceptance of Kepler’s work inEngland.

Another figure in the last quarter of the sixteenth century, who, although not an astronomer, made a very important contribution to the cosmological debate, was the physician William Gilbert (1544–1603).

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William Gilbert (1544–1603) artist unknown. Source: Wellcome Library via Wikimedia Commons

Gilbert is well known in the history of science as the author of the first modern scientific investigation of magnetism in his De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth).

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Gilbert carried out many of his experiments with spherical magnets, which he called terella, from which he deduced his belief that the Earth itself is a spherical magnet. Based on his erroneous belief that a suspended terella rotates freely about its axis he came to accept and propagate diurnal rotation. Book VI of De magnete, the final book, is devoted to an analysis of the Earth as a spherical magnet based on the results of Gilbert’s experiments with his terella.

In Chapter III of Book VI, On the Daily Magnetic Revolution of the Globes, as Against the Time-Honoured Opinion of a primum mobile: A Probable Hypothesis, Gilbert gives a detailed review of the history of a geocentric system with diurnal rotation starting with Heraclides of Pontus and going through to Copernicus. Gilbert rejects the whole concept of celestial spheres, dismissing them as a human construction with no real existence. He brings the standard physical arguments that it is more logical that the comparatively small Earth rotates once in twenty-four hours rather than the vastly larger sphere of the fixed stars. In the following chapter he then argues that magnetism is the origin of this rotation. In Chapter V he discusses the arguments for and against movement of the Earth. At the end of Chapter III Gilbert writes, “I pass by the earth’s other movements, for here we treat only of the diurnal rotation…” so what he effectively promotes is a geocentric system with diurnal rotation. Later in his De Mundo Nostro Sublunari Philosophia Nova (New Philosophy about our Sublunary World), Gilbert propagated a full heliocentric system but this book was first published posthumously in 1651 and had no real influence on the astronomical discussion.

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Diagram of the cosmos De Mundo p. 202 Source: Wikimedia Commons

Gilbert’s De magnete was a widely read and highly influential book in the first half of the seventeenth century. Galileo praised it but criticised its lack of mathematics. As we shall see it had a massive influence on Kepler. Because of its status the book definitely had a major impact on the acceptance of geo-heliocentric systems with diurnal rotation rather than without later in the seventeenth century.

We will stop briefly and take stock in 1593, fifty years after the publication of De revolutionibus. We have seen that within Europe astronomers had already begun to question the inherited Ptolemaic system during the fifteenth century. In the sixteenth century a major debate developed about both the astronomical and cosmological models. The Aristotelian theories of comets, the celestial spheres and celestial immutability all came under attack and were eventually overturned. Alternative models–Aristotelian homocentricity, the Capellan system and geocentricity with diurnal rotation–were promoted.  With the publication of Copernicus’ De revolutionibus with its heliocentric hypothesis the debates went into overdrive. Only a comparatively small number of astronomers propagated the heliocentric system and an even smaller number of them actually went on to have a real impact on the discussion. A much larger number showed an initial strong interest in the mathematical models in De revolutionibus and the planetary tables and ephemerides based on them, in the hope they would generate better, more accurate data for applications such as astrology, cartography and navigation. This proved not to be the case as Copernicus’ work was based on the same inaccurate and corrupted ancient data, as Ptolemaic geocentric tables. Recognising this both Wilhelm IV in Kassel and Tycho Brahe on Hven began programmes of extensive new astronomical observations. However, this very necessary new data only became generally available well into the seventeenth century. Other astronomers partially convinced by Copernicus’ arguments turned to Capellan models with Mercury and Venus orbiting the Sun rather than the Earth and full geo-heliocentric models with the Moon and the Sun orbiting the Earth and all the other five planets orbiting the Sun. This was the situation at the beginning of the 1590s but a young Johannes Kepler (1571–1630), who would have a massive impact on the future astrological and cosmological models, was waiting in the wings.

 

 

 

 

 

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Kepler was wot, you don’t say?

 

The Guardian is making a serious bid for the year’s worst piece of #histsci reporting or as Adam Shapiro (@tryingbiology) once put it so expressively, #histsigh! The article in question has the shock, horror, sensation headline: Groundbreaking astronomer Kepler ‘may have practised alchemy’. Ignoring the fact for the moment that he probably didn’t, given the period and the milieu in which Kepler lived and worked saying that he may have been an alchemist is about as sensational as saying he may have been a human being.

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Johannes Kepler Source: Wikimedia Commons

The period in which Kepler lived was one in which the interest in alchemy was very widespread, very strong and very open. For eleven years he was Imperial Mathematicus at the court in Prague of the German Emperor Rudolph II, which was a major centre for all of the so-called occult sciences and in particular alchemy. In Prague Kepler’s original employer Tycho Brahe had been for years a practitioner of Paracelsian alchemical medicine (a very widespread form of medicine at the time), which to be fair the article sort of says. What they say is that Tycho was an alchemist, without pointing out that his alchemy was restricted to medical alchemy.

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Tycho Brahe Source: Wikimedia Commons

One of his colleagues was the Swiss clockmaker Jost Bürgi, who had come to Prague from Hesse-Kassel,

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Jost Bürge Source: Wikimedia Commons

where the Landgrave Moritz was a major supporter of alchemy, who appointed Johannes Hartmann (1568–1631) to the first ever chair for chemistry, actually Paracelsian medicine, at the university of Marburg. The real surprise is not that Kepler was an alchemist or practiced alchemy but rather that given the time and milieu in which he lived and worked that he wasn’t and didn’t.

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Johannes Hartmann Source: Wikimedia Commons

How can I be so sure that Kepler didn’t dabble in alchemy? Simply because if he had, he would have written about it. Kepler is a delight, or a nightmare, for the historian, there is almost no figure that I know of in #histSTM, who was as communicative as Kepler. He wrote and published eighty three books and pamphlets in his lifetime covering a very wide range of topics and in all his written work he was always keen to explain in great detail to his readers just what he was doing and his thoughts on what he was doing. He wrote extensively and very openly on his mathematics, his astronomy, his astrology, his family, his private affairs, his financial problems and all of his hopes and fears. If Kepler had in anyway been engaged with alchemy, he would have written about it. If anybody should chime in now with, yes but alchemists kept they activities secret, I would point out in Kepler’s time the people practicing alchemy, particularly the Paracelsians, were anything but secretive. And it was with the Paracelsians that Kepler had the closest contact.

There are a few letters exchanged between Kepler and his Paracelsian physician friends, which show quite clearly that although Kepler displayed the natural curiosity of a scientific researcher in their alchemistic activities he did not accept the basic principles of alchemy. In his notorious exchange with Robert Fludd, he is very dismissive of Fludd’s alchemical activities. Kepler was not an alchemist.

From a historical point of view particularly bad is the contrast deliberately set up in the article between good science, astronomy and mathematics, and ‘dirty’ pseudo- science’, alchemy. This starts with the title:

Groundbreaking astronomer Kepler ‘may have practised alchemy’

Continues with the whole of the first paragraph:

The pioneering astronomer Johannes Kepler may have had his eyes on the heavens, but chemical analysis of his manuscripts suggests he was “willing to get his hands dirty” and may have dabbled in alchemy.

“Kepler, who died in 1630, drew on Copernicus’s work to find laws of planetary motion that paved the way for Isaac Newton’s theory of gravity” is contrasted with “The authors speculate that Kepler could have learned the “pseudo-chemical science.” 

A ‘pioneering astronomer’ with ‘his eyes on the heavens’, serious scientific activity, but ‘dabbled in alchemy’. Whoever wrote these lines obviously knows nothing about Kepler’s astronomical writing nor about early 17thcentury alchemy.

The article through its choice of descriptive terms tries to set up a black/white dichotomy between the man who paved the way for modern astronomy, good, and the practitioners of alchemy in the early seventeenth century, bad. However if we actually look at the real history everything dissolves into shades of grey.

Kepler was not just an astronomer and mathematician but also a practicing astrologer. People might rush in here with lots of Kepler quotes condemning and ridiculing the nativity horoscope astrology of his age, all of them true. However, he famously said one shouldn’t throw the baby out with the bath water defending the basic idea of astrology and presenting his own unique system of astrology based entirely on aspects, that is the angular position of the planets relative to each other. The author of the piece has obviously never turned the pages of either Kepler’s Mysterium Cosmographicum or his Harmonice Mundi. As I commented on Twitter, during a discussion of this article, Kepler’s cosmological heuristic with which he generated all of his successful astronomy was, viewed from a modern rational standpoint, quite simply bat shit insane. Things are not looking good for our pioneering astronomer.

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Kepler’s Platonic solid model of the solar system, from Mysterium Cosmographicum (1596) Kepler’s explanation as to why there are only five planets and their order around the sun! Source: Wikimedia Commons

On the other side, as I have noted on several occasions, alchemy included much that we now label applied and industrial chemistry.  For example, alchemists were responsible for the production of pigments for painters and gunpowder for fireworks and cannons, and were often glassmakers. Alchemists were historically responsible for developing the laboratory equipment and methodology for chemical analysis. In the period under discussion many alchemists, including Tycho, were Paracelsian physicians, who are credited with the founding of the modern pharmacological industry. Historians of alchemy tend to refer to the alchemy of the seventeenth century as chymistry because it represents the historical transition from alchemy to chemistry. Not so much a pseudo-science as a proto-science.

Let us now consider the so-called evidence for the articles principle claim. Throughout the article it is stated that the evidence was found on Kepler’s manuscripts, plural. But when the evidence is actually discussed it turns out to be a single manuscript about the moon. On this manuscript the researchers found:

“…very significant amounts of metals associated with the practice including gold, silver, mercury and lead on the pages of Kepler’s manuscript about the moon, catalogued as “Hipparchus” after the classical astronomer.”

Is alchemy the only possible/plausible explanation for the traces of metals found on this manuscript? Could one suggest another possibility? All of these metals could have been and would have been used by a clock and instrument maker such as Jost Bürgi, who was Kepler’s close colleague and friend throughout his eleven years in Prague. Bürgi also had a strong interest in astronomy and might well have borrowed an astronomical manuscript. Of course such a solution doesn’t make for a sensational article, although all the available evidence very strongly suggests that Kepler was not an alchemist.

One final point that very much worries me is the provenance of this document. It is four hundred years old, who has owned it in the meantime? Where has it been stored? Who has had access to it? Until all of these questions can be accurately answered attributing its contamination to Kepler is just unfounded speculation.

 

 

 

 

 

 

 

 

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Everything you wanted to know about Simon Marius and were too afraid to ask – now in English

Regular readers of this blog should by now be well aware of the fact that I belong to the Simon Marius Society a small group of scholars mostly from the area around Nürnberg, who dedicate some of their time and energy to re-establishing the reputation of the Franconian mathematicus Simon Marius (1573–1625), who infamously discovered the four largest moons of Jupiter literally one day later than Galileo Galilei and got accused of plagiarism for his troubles. Galileo may have discovered them first but Marius won, in the long term, the battle to name them.

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Frontispiece of Mundus Iovialis Source:Wikimedia Commons

In 2014 the Simon Marius Society organised many activities to celebrate the four-hundredth anniversary of the publication of his opus magnum, Mundus Jovialis (The World of Jupiter). Amongst other things was an international conference held in Nürnberg, which covered all aspects of Marius’ life and work. The papers from this conference were published in German in 2016: Simon Marius und seine Forschung (Acta Historica Astronomiae), (AVA, Leipzig).

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Now after much effort and some delays the expanded translation, now includes the full English text of Mundus Jovialis, has become available in English: Simon Marius and his Research, Springer, New York, 2019.

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The ebook is already available and the hardback version will become available on 19 August. I apologize for the horrendous price but the problem of pricing by academic publishers is sadly well known. Having copyedited the entire volume, which means I have read the entire contents very carefully I can assure you that there is lots of good stuff to read not only about Simon Marius but also about astronomy, astrology, mathematics, court life in the seventeenth century and other topics of historical interest. If you can’t afford a copy yourself try to persuade you institutional library to buy one! If your university library buys a copy from Springer then students can order, through the library, a somewhat cheaper black and white copy of the book.

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The emergence of modern astronomy – a complex mosaic: Part XI

Despite the high level of anticipation De revolutionibus cannot be in anyway described as hitting the streets running; it was more a case of dribbling out very slowly into the public awareness. There are several reasons for this. Today there is a well-oiled machine, which goes into operations when an important new book is published. Book reviews and adverts in the relevant journals and newspapers, books delivered in advance to bookshops all over the country, radio and television interviews with the author and so on.

Absolutely none of this apparatus existed in anyway in the fifteenth century. There were no journals or newspapers, where reviews and adverts could be published. Information about a new publication was distributed over the academic grapevine by mail; the grapevine was quite efficient with scholars communicating with each other throughout Europe but the mail system wasn’t. Letters often took months and quite often never arrived at all. There were no bookstores, as we know them today and no book distribution network. Petreius had a stall on the local market place but he probably would not have sold many copies of De revolutionibus in Nürnberg itself.

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A 19th century painting of the Nürnberg market place

In this context it is interesting that the town library doesn’t own a copy of the 1st edition. For other sales, other than by mail, Petreius would have transported copies of the book packed into barrels to the annual fairs in Leipzig and Frankfurt, where, as well as private customers, other printer publishers would buy copies of the book to take back to their home towns to supplement their own production for their local customers. The Leipzig fair took place at Easter and in autumn, the Frankfurt fair only in autumn. Easter 1543 was in April so the distribution of De revolutionibus only really began in the autumn of that year.

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Frankfurt Book Fair 1500

The next factors that slowed the reception of De revolutionibus were the price and the content. As a large book with a complex mathematical content with lots of tables and diagrams, De revolutionibus was a very expensive book putting it outside of the financial range of students or anybody without a substantial income or private fortune. A first edition bought by the astrologer Valentin Engelhart (1516-1562) in 1545 cost 1 florin = 12 groschen. A students university matriculation fees at this time cost between 6 and 10 groschens. It is indicative that Kepler could only afford to acquire a second hand copy. Owen Gingerich speculates that the high cost of the book is the reason for the comparatively high survival of copies, Gingerich estimates about fifty per cent. It was very expensive so people took good care of it. The high price and the complex contents very much limited potential sales.

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De Revolutionibus woodcut of the heliocentric cosmos Source: Latin Wikisource

In terms of content this was a major, heavy duty, large-scale mathematical text and not in anyway something for the casual reader, no mater how well read. Copernicus’ Mathemata mathematicis scribuntur was meant very seriously. This suggests that the potential circle of purchasers was fairly strictly limited to the comparatively small group of mathematical astronomers, who would be capable of reading and understanding Copernicus’ masterpiece. Given his record in the field of mathematical and astronomical/astrological publishing Petreius naturally already had a group of customers to whom he could offer his latest coup in this genre, otherwise he probably would not have published De revolutionibus. However, even if he could get this very specialist book to its specialist group of readers, they would require a comparatively long time to read, work through and digest its complex contents. The earliest known published reaction to De revolutionibus was Gemma FrisiusDe radio astronomico et geometrico a booklet of a multipurpose astronomical and geometrical instrument published in 1545 two years after Copernicus’ volume.

Here at this comparatively early point Frisius, who knew of Copernicus’ hypothesis through the Narratio Prima and and had been invited by Dantiscus, Prince-Bishop of Frombork, one of his patrons, to come to Frombork and work with Copernicus, displays a very cautious attitude towards the new heliocentric astronomy although he is very critical towards Ptolemaeus’ work.

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Johannes Dantiscus Source: Wikimedia Commons

Given that the main purpose of astronomy was, at this time, still to provide astronomical data for astrology, navigation and cartography many of those potentially interested in the new astronomy were waiting for new planetary tables and ephemerides before passing judgement. The earliest planetary tables, the Tabulae prutenicae (Prutenic Tables) based on De revolutionibus, but not exclusively, were produced by the professor for the higher mathematics (music and astronomy) at Wittenberg Erasmus Reinhold (1511–1553) and first published in 1551.

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Source: Wikimedia Commons

These tables were financed by Albrecht I, Duke of Prussia hence the name Prutenic i.e. Prussia.

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Albrecht, Duke of Prussia portrait by Lucas Cranach the elder Source: Wikimedia Commons

Interestingly Reinhold was not a supporter of heliocentricity. Ephemerides based on the Prutenic Tables were produced in the Netherlands by Johannes Stadius (1527–1579) a pupil of Gemma Frisius in 1554 with an introductory letter by his old teacher.

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Johannes Stadius Source: Wikimedia Commons

A second set of ephemerides, also based on the Prutenic Tables, were produced in England by John Feild (c. 1525–1587), a pupil of John Dee (1527–1608) in 1557. Dee was another pupil of Gemma Frisius, so this might be a case of the academic grapevine in operation. These tables and ephemerides played an important roll in spreading awareness of the new heliocentric hypothesis.

Whereas with a modern publication reception will probably be judged in terms of months or even weeks for a popular book and a few years for a serious academic title; looking at De revolutionibus to judge its reception we really need to cover the sixty plus years following its publication up to the invention of the telescope, the next major game changer in astronomy.

There is a popular misconception that that reception can be quantified in terms of those for and those against the heliocentric hypothesis. This is very much not the case. As I tried to make clear at the beginning of this series the sixteenth century was very much characterised by very lively debates on various aspects of astronomy–the nature, status and significance of comet, a lively revival of the Aristotelian homocentric spheres model of the cosmos and a growing dissatisfaction with the quality of the available astronomical data. There were small smouldering fires of debate everywhere within the European astronomical community, Copernicus’ De revolutionibus turned them into a raging bush fire; the reactions to its publication were multifaceted and the suggested changes it provoked were wide-ranging and highly diverse. It would be more than a hundred years before the smoke cleared and a general consensus could be found within the astronomical community.

 

 

 

 

 

 

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The emergence of modern astronomy – a complex mosaic: Part IX

In 1542 the manuscript of De revolutionibus arrived at Petreius’ printing office in Nürnberg followed by Rheticus who intended to see it through the press. I argued in Part VII that Johannes Petreius had in fact commissioned Rheticus to see if Copernicus had written anything substantial on his astronomical theories and if so to persuade him to allow Petreius to publish it. Petreius’ printing office was certainly the right address for the publication of a major new work on astronomy, as he was certainly the leading scientific publisher–astrology, astronomy, mathematics–in the Holy Roman Empire of German States and probably the whole of Europe but who was Johannes Petreius?

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The Petreius printing office in Nürnberg Photo by the author

He was born Hans Peter, whereby Peter is the family name, into a family of wealthy farmers in the Lower Franconia village of Langendorf near Hammelburg in 1496 or 1497. He matriculated at the university of Basel in 1512, graduating BA in 1515 and MA in 1517. He next appears as a witness in a court case in Basel in 1519, where he is described, as working as a proofreader for the Basler printer publisher Adam Petri. This explains why he had chosen to study in Basel, as Adam Petri was his uncle. Petri is the Swizz German version of the name Peter. Presumably, having learnt the black art, as printing was known, from his uncle he moved to Nürnberg in 1523 and set up his own printing office. The was almost certainly an attempt by the Peter family to cash in on the gradual collapse of the Koberger printing office following the death of Aton Koberger in 1513. The Petri-Froben-Amerbach printing cooperative had been Koberger’s licensees in Basel, printing his titles on commission.

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Source: Wikimedia Commons

Hans Peter now sporting the Latinised name, Johannes Petreius, succeeded in establishing himself against the local competition and by 1535 was the leading printer publisher in Nürnberg. Like most other printer publishers Petreius’ main stock in trade was printing religious volumes but in the 1530s he began to specialise in printing scientific texts. Exactly why he chose to follow this business path is not known but it was probably the ready availability of the large number of mathematical, astrological and astronomical manuscripts brought to Nürnberg by Regiomontanus when he set up his own printing office in 1471. This hypothesis is supported by the fact that several of Petreius’ earliest scientific publications were all of manuscripts from this collection, all of which were edited for publication by Johannes Schöner, who would later be the addressee of Rheticus’ Narratio  Prima.

This series of publications started with Schöner’s edition of Regiomontanus’ own De Triangulis in 1533, a very important work in the history of trigonometry. This was also one of the volumes that Rheticus took with him to Frombork, as a present for Copernicus.

Schöner followed this with Regiomontanus’ Tabulae astronomicaein 1536. Petreius’ activities in the area were not however restricted to Schöner’s output. Earlier he published the first Greek edition of Ptolemaeus’ Tetrabiblos, under the title Astrologica, edited by Joachim Camerarius (1500–1574), which included Camerarius’ translation into Latin of Books I & II and partial translations of Books III & IV together with his notes on Books I & II and the Greek text of the Centiloquium, a collection of one hundred astrological aphorism falsely attributed to Ptolemaeus, with a Latin translation by Giovanni Pontano (1426–1503).

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Opening chapter of the first printed edition of Ptolemy’s Tetrabiblos, transcribed into Greek and Latin by Joachim Camerarius (Nuremberg, 1535). Source: Wikimedia Commons

A year earlier Petreius had published Johann Carion’s Practica new – auffs 1532 mit einer auslegung des gesehen cometen. Through these publications it is clear that the principle interest is in astrology and it is here that money was to be made. Over the next twenty plus years Petreius published more texts from Regiomontanus edited by Schöner, some of Schöner’s own works on astronomy and cartography, reckoning and algebra books from Christoph Rudolff  (c. 1500–before 1543) and Michael Stifel (1487–1567). Various scientific texts edited by Peter Apian including his and Georg Tannstetter’s edition of Witelo’s Perspectiva (1535), another of the volumes that Rheticus took with him to Frombork for Copernicus. Various Arabic astrological texts, the Tractatus astrologicae (1540) of Lucas Gauricus (1575–1558), who along with Schöner and Cardano was one of the most important astrologers of the first half of the sixteenth century. Petreius became the publisher of Gerolamo Cardano (1501–1576) north of the Alps, publishing his works on mathematics, astronomy, medicine, astrology and philosophy, all of which were highly successful.

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Source: Wikimedia Commons

He also published alchemical works from Abū Muḥammad Jābir ibn Aflaḥ better known in the West as Geber. As well as all this, Petreius commissioned and published the first German translation of Vitruvius’ De architectura, a bible for Renaissance artist-engineers.

Petreius’ scientific catalogue was very wide but also had depth, including as it did various classics by Regiomontanus, Schöner, Stifel, Cardano and Witelo. If anybody could adequately present Copernicus’ masterpiece to the world then it was Johannes Petreius.

Rheticus had originally intended seeing Copernicus’ manuscript through the press but Philipp Melanchthon had other plans for his errant protégée. In the meantime Rheticus had, at the request of Joachim Camerarius, who was now rector of the University of Leipzig and had obviously been impressed by Rheticus during their meeting in Tübingen, been offered a chair in mathematics at Leipzig.

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Joachim Camerarius, 18th-century engraving by Johann Jacob Haid. Source: Wikimedia Commons

In the autumn of 1542 Rheticus, under pressure from Melanchthon, left Nürnberg and preceded to Leipzig, where he was appointed professor of higher mathematics i.e. astronomy and music and his direct involvement in De revolutionibus came to an end. Petreius still needed an editor to see Copernicus’ weighty tome through the press and this duty was taken over, with serious consequences by Nürnberg’s Lutheran Protestant preacher, Andreas Osiander (1496 or 1498–1552).

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Andreas Osiander portrait by Georg Pencz Source: Wikimedia Commons

Osiander was born in the small town of Gunzenhausen to the south of Nürnberg, the son of Endres Osiander a smith and Anna Herzog. His father was also a local councillor who later became mayor. He matriculated at the University of Ingolstadt in 1515 where he, amongst other things, studied Hebrew under the great humanist scholar and great uncle of Melanchthon, Johannes Reuchlin. In 1520 he was ordained a priest and called to Nürnberg to teach Hebrew at the Augustinian Cloister, a hot bed of reformatory debate, where he also became a reformer. In 1522 he as appointed preacher at the St Lorenz church and became a leading voice for religious reform. Osiander achieved much influence and power in Nürnberg when the city-state became the very first Lutheran Protestant state.

Osiander first became involved with Petreius when the latter started publishing his religious polemics. Petreius also published numerous religious works by both Luther and Melanchthon. Where or how Osiander developed his interest and facility in the mathematical sciences is simply not know but they are attested to by Cardano in the preface to one of his books published by Petreius. In fact it was Osiander, who was responsible for the correspondence between Cardano and the Petreius printing office and he edited Cardano’s books there. When or how Osiander became an editor for Petreius is also not known. In his capacity as editor of De revolutionibus Osiander committed what many have as one of the greatest intellectual crimes in the history of science, he added the infamous ad lectorum, an address to the reader with which the book opens.

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Latin Wikisource

The ad lectorum is an essay that it pays to read in full but here we will just consider the salient points, Osiander writes:

There have already been widespread reports about the new novel hypothesis of this work, which declares that the earth moves whereas the sun is at rest in the centre of the universe.

Here Osiander lets us know that knowledge of Copernicus’ heliocentric hypothesis was already widespread–spread by the Commentariolus, the Narratio Prima and by rumour–indicating that there was going to be a high level of expectancy to learn the mathematical details of the system. He goes on:

Hence certain scholars, I have no doubt, are deeply offended and believe that the liberal arts, which were established long ago on a sound basis, should not be thrown in confusion.

Anticipating criticism from conservative circles Osiander goes into defensive mode:

But if these men are willing to examine the matter closely, they will find that the author has done nothing that is blameworthy. For it is the duty of an astronomer to compose the history of the celestial motions through careful and expert study. Then he must conceive and devise the causes of these motions or hypotheses about them. Since he cannot in any way attain to the true causes, he will adopt whatever suppositions enable the motions to be computed correctly from the principles of geometry for the future as well as the past.

Here we have the crux of Osiander’s defence. Astronomers are here to produce geometrical models in order to provide accurate predictions of celestial motions and not to determine the unobtainable true causes of those motions. This argument has been dubbed instrumentalist and some hail Osiander as the first instrumentalist philosopher of science. Instrumentalism is a metaphysical attitude to scientific theories that enjoyed a lot of popularity in modern physics in the twentieth century; it doesn’t matter if the models we use describe reality, all that matters in that they predict the correct numerical results. Osiander expands on this viewpoint:

For these hypotheses need not be true or even probable. On the contrary, if they provide a calculus consistent with the observations, that alone is enough.

Here we have the core of why the ad lectorum caused so much outrage over the centuries. Osiander is stating very clearly that the mathematical models of astronomers are useful for predictive purposes but not for describing reality. A view that was fairly commonplace over the centuries amongst those concerned with the subject. Copernicus, however, very clearly deviates from the norm in De revolutionibus in that he presents his heliocentric system as a real model of the cosmos. Osiander’s ad lectorum stands in clear contradiction to Copernicus’ intentions. Osiander then goes into more detail illustrating his standpoint before closing his argument as follows:

…the astronomer will take as his first choice that hypothesis which is easiest to grasp. The philosopher will perhaps rather seek the semblance of the truth. But neither of them will understand or state anything certain, unless it has been divinely revealed to him.

Here we have Osiander restating the standard scholastic division of responsibilities, astronomers provide mathematical models to deliver accurate predictions of celestial motions for use by others, philosophers attempt to provide explanatory models of those motions but truth can only be delivered by divine revelation. The modern astronomy, whose gradual emergence we are tracing had to break down this division of responsibilities in order to become accepted as we shall see in later episodes. Osiander closes with a friendly appeal to the reader to permit the new hypotheses but not to take them too seriously, and thereby make a fool of himself.

Therefore alongside the ancient hypotheses, which are no more probable, let us permit these new hypotheses also the become known, especially since they are admirable as well as simple and bring with them a huge treasure of very skilful observations. So far as hypotheses are concerned, let no one expect anything certain from astronomy, which cannot furnish it, lest he accept as the truth ideas conceived for another purpose, and depart from this study a greater fool than he entered it. Farewell.

There is a widespread belief that Osiander somehow smuggled his ad lectorum into De revolutionibus without the knowledge of either Copernicus or Petreius but the historical evidence speaks against this. There are surviving fragments of a correspondence between Osiander and Copernicus that make it clear that Osiander discussed the stratagem of presenting De revolutionibus as a hypothesis rather that fact with him; although we don’t know how or even if Copernicus reacted to this suggestion. More telling is the situation between Petreius and Osiander.

There is absolutely no way that Osiander could have added the ad lectorum without Petreius’ knowledge. This is supported by subsequent events. When the book appeared Tiedemann Giese was outraged by the presence of the ad lectorum and wrote a letter to the city council of Nürnberg demanding that it be removed and the book reissued without this blemish. The council consulted Petreius on the subject and he let them know in no uncertain terms that it was his book and what he put in it was his business and nobody else’s.

Petreius’ reaction illustrates an important point that modern commentators often overlook. Our concept of copyright didn’t exist in the sixteenth century, the rights to a publish work in general lay with the publisher and not the author. This is clearly demonstrated by the fact that when a publication provoked the ire of the authorities, civil or clerical, it was the printer publisher, who first landed before the court and then in goal rather than the author.

The ad lectorum was anonym but any reader, who was paying attention should have realised through the phrasing that Copernicus was not the author. The Nürnberger astronomer and instrument maker Johannes Pratorius (1537–1615), another Wittenberg graduate, wrote in his copy of De revolutionibus that Rheticus, when Pratorius visited him in 1569, had revealed to him that Osiander was the author of the ad lectorum.

800px-JohannesPraetorius

Source: Wikimedia Commons

Michael Maestlin’s copy contains the same information also from Rheticus via Peter Apian. Kepler’s second hand copy had this information added by its original owner Hieronymus Schreiber (birth date unknown–1547), yet another Wittenberg graduate, who had received a gift copy signed by Petreius, because he had substituted for Rheticus in Wittenberg during the latter’s time in Frombork. All of this indicates that Osiander’s authorship of the ad lectorem was circulating on the astronomers’ grapevine by 1570 at the latest. It was first put into print, and thus made general public, by Kepler in his Astronomia Nova in 1609.

As with most books in the Early Modern Period there was no publication date for De revolutionibus but it seems to have been finished by 20thApril 1543, as Rheticus signed a finished copy on this date. According to a legend, put in the world by Tiedemann Giese, Copernicus received his copy, which was placed into his hands, on his dying day the 24thMay 1543. Owen Gingerich, who is the expert on the subject, estimates that the 1stedition probably had a print run of about 400 copies, which carried the mathematical details of Copernicus’ hypothesis out into the wide world.

 

 

 

 

 

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The emergence of modern astronomy – a complex mosaic: Part VIII

We left Georg Joachim Rheticus[1](1514–1574) just setting out on his journey from Feldkirch to Frombork for what would turn out to be one of the most fateful meetings in the history of science. Our wealthy professor of mathematics travelled in style accompanied by a famulus Heinrich Zell (?–1564), a Wittenberg student, who would later have a career as cartographer, astronomer and librarian. What is rarely mentioned in detail is that Rheticus travelled from Feldkirch to Wittenberg, which is where he collected Zell, and then having acquired permission to extend his sabbatical, continued on his way to Frombork. In total this is a journey of more than 1500 kilometres, hard enough even today but a major expedition in the middle of the sixteenth century.

We have no direct account of the initial meeting between the twenty-five year old mathematics professor and the sixty-six year old cathedral canon.

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Portrait of Copernicus holding a lily of the valley, published in Nicolaus Reusner’s Icones (1587), based on a sketch by Tobias Stimmer (c. 1570), allegedly based on a self-portrait by Copernicus. Source: Wikimedia Commons

They obviously got on well, as Rheticus ended staying in the area for two and a half years. Shortly after his arrival Rheticus fell ill and Copernicus took him to Löbau, the home of his friend Tiedemann Giese (1480–1550) Bishop of Kulm, to convalesce.

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Portrait of Tiedemann Giese by Hans Schenck, Source: Wikimedia Commons

This episode illustrates an important aspect of Rheticus’ visit. Here was a Lutheran Protestant professor of mathematics from the home of Lutheran Protestantism, Wittenberg University visiting a Catholic cathedral canon in the middle of a deeply Catholic area. Despite the fact that this visit took place in the middle of the Reformation and the beginnings of the Counter Reformation Rheticus was always treated as an honoured guest by all those, who received him whether Protestant, Albrecht, Duke of Prussia,

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Albrecht, Duke of Prussia portrait by Lucas Cranach the elder Source: Wikimedia Commons

or Catholic, Copernicus, Giese and above all the Prince-Bishop of Frombork, Johannes Danticus (1485–1548), who although strongly anti-Reformation was also an admirer of Philipp Melanchthon (1497–1560), whom he had met personally.

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Johannes Dantiscus Source: Wikimedia Commons

This courtesy across the religious divide amongst scholars during this period of European religious turmoil was actually very common and contradicts a popular image of hate, rejection and bigotry on all fronts and at all levels.

We know of Rheticus’ convalescence in Löbau, because he mentions it on the first page of his Narratio Prima (The First Account) the booklet he wrote shortly after his arrival in Frombork and the first published account of Copernicus’ heliocentric system. He explains that because of his illness he has had barely ten weeks to familiarise himself with the manuscript of Copernicus’ magnum opus in order to describe and explain it in the Narratio Prima, which is an open letter to Johannes Schöner, his Nürnberger astrology teacher and one of Johannes Petreius’ expert editors.

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Johannes Schöner Source: Wikimedia Commons

The introduction also makes clear that he had promised Schöner, and probably through him Petreius, this report before leaving Nürnberg. Johannes Petreius’ dedicatory letter to Rheticus in his edition of the fourteenth-century physician Antonius de Motulmo’s De iudiciis nativitatumwas a direct response to the Narratio Prima. He goes on to give a very brief outline of the work, making no mention of the fact that Copernicus’ system is heliocentric. He says that he has mastered the first three books, of six, grasped a general idea of the forth and begun to conceive the hypotheses of the rest. He says he is going to skip the first two books for which he has a special plan; he originally intended to write a Narratio Secunda, which never materialised. He then plunges into his description.

The first four sections are technical astronomical accounts of: The Motion of the Fixed Stars, General Considerations of the Tropical Year, The Change in the Obliquity of the Ecliptic, and The Eccentricity of the Sun and the Motion of the Solar Apogee. In the fifth section, The Kingdom of the World Change with the Motion of the Eccentric, Rheticus changes tack completely and presents us with an astrological theory of cyclical historical change. I shall quote the beginning of this extraordinary section:

I shall add a prediction. We see that all kingdoms have had their beginnings when the centre of the eccentric was at a special point on the small circle. Thus, when the eccentricity of the sun was at its maximum, the Roman government became a monarchy; as the eccentricity decreased, Rome too declined, as aging, and then fell. When the eccentricity reached the boundary and quadrant of mean value, the Mohammedan faith was established; another great empire came into being and increased very rapidly, like the change in the eccentricity. A hundred years hence, when the eccentricity will be at its minimum, this empire too will complete its period.

This calculation does not differ much from the saying of Elijah, who prophesied under divine inspiration that the world would endure only 6,000 years, during which time nearly two revolutions are completed[2].

There is nothing about this to be found in Copernicus’ De revolutionibus but Copernicus certainly read the Narratio Prima before it was published and didn’t object to it or ask Rheticus to remove it. Such astrological cyclical theories of history were en vogue during the Early Modern Period. The most well known one was written by Johannes Carion (1499–1537), who together with Philipp Melanchthon was a student of Johannes Stöffler (1442–1531). Carion had also received language tuition from the slightly older Melanchthon.  Carion was court astrologer to the Elector Joachim I of Brandenburg (1484–1535).

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Johann Carion, portrait by Lucas Cranach the Elder Source: Wikimedia Commons

Carion wrote a chronicle based on Biblical prophecies, which divided world history into three 2000-year periods. The chronicle was published shortly after Carion’s death. Following Carion’s death this chronicle passed into Melanchthon’s hands, who reworked it and published it again. Rheticus a student of Melanchthon obviously joined the Carion tradition in his astrological excurse in the Narratio Prima, which goes into long technical detail on the following pages.

In the next section Rheticus returns to Copernicus’ astronomy, Special Consideration of the Length of the Tropical Year. Up till now we have no indication at all from Rheticus that the system he is describing is a heliocentric one. We are now about one third of the way through and Rheticus’ next section is General Considerations Regarding the Motions of the Moon,Together with the New Lunar Hypothesis. At the end of this section we can read:

These phenomena, besides being ascribed to the planets, can be explained, as my teacher shows, by a regular motion of the spherical earth; that is, by having the sun occupy the centre of the universe, while the earth revolves instead of the sun on the eccentric, which it has pleased him to name the great circle. Indeed, there is something divine in the circumstance that a sure understanding of celestial phenomena must depend on the regular and uniform motions of the terrestrial globe alone.

He casual drops the information that we are indeed in a heliocentric world system in passing, as if were the most natural thing in the world. Having in the previous sections demonstrated Copernicus’ abilities as a theoretical astronomer he finally lets the cat out of the bag. There now follow eight sections in which he explains how the new hypothesis functions with the whole of astronomy.

The book closes with a non-astronomical section, In Praise of Prussia. This is a general polemic about how wonderful Prussia and the Prussian are and how well Rheticus has been received and treated by his Prussian hosts. It does, however, contain a section describing Giese’s attempts to persuade Copernicus to publish De revolutionibus and that Copernicus’ response to these enticements is to suggest that he will publish his tables of astronomical data without revealing the methods used to obtain them.

The Narratio Prima is dated 23 September 1539 by Rheticus, who took the manuscript to Danzig where it was printed and published by Franz Rhode in 1540 with the help of a donation towards the printing costs from Johann von Werden (c. 1495–1554) the mayor of Danzig. The title page is interesting as it begins with an honourable address to Johannes Schöner followed by The Books of Revolutions then an equally honourable naming of Copernicus but Rheticus, the author, is simply described as a young student of mathematics[3].

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Title page of the 1st edition of the Narratio Prima Source: Wikimedia Commons

The Narratio Prima was fairly obviously conceived as a test balloon for Copernicus’ heliocentric hypothesis. It seems to have been well received and one recipient took his enthusiasm for the text much further. Rheticus had sent a copy to his mentor Achilles Pirmin Gasser (1505-1577),

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Achilles Permin Gasser Source: Wikimedia Commons

who published a second edition of the book with a new dedicatory letter and Rheticus named on the title page in Basel in 1541.

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First page of a later edition of the Narratio Prima with Rheticus named as author

The positive reception of the Narratio Prima and the lack of negative reactions seem to have finally convinced Copernicus to allow De revolutionibus to be published.

The Narratio Prima is rather long winded, strong on rhetoric and polemic but rather weak on its scientific content. There are no diagrams and Rheticus tends to rely on philosophical arguments rather than mathematical ones. He does, however, display a high degree or erudition, his text is full of classical quotes and allusions, which doesn’t actually make it easier for those who don’t have a classical eduction to plow through his, at times, rather turgid prose.

A third edition of the Narratio Prima was included in the second edition of De revolutionibus published by Heinric Petri in Basel in 1566. The forth and a fifth editions were included in the first and second editions of Johannes Kepler’s Mysterium Cosmographicum in 1597 and 1621. As such, more people probably learnt of Copernicus’ heliocentric system from the Narratio Prima than any other source.

Rheticus stayed in Frombork helping Copernicus to prepare his manuscript for publication by Petreius in Nürnberg. In October 1541 Rheticus left for Wittenberg, where he published an edited and improved version of the trigonometrical section of Derevolutionibusunder Copernicus’s name, De lateribus et angulis triangulorum (On the Sides and Angles of Triangles), which appeared in 1542.

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This very useful publication also helped to increase Copernicus’ reputation in astronomical and mathematical circles. Rheticus would dedicate much of his future life to the publication of improved trigonometrical table.

In 1542 the manuscript of De revolutionibus arrived at Petreius’ printing office in Nürnberg followed by Rheticus who intended to see it through the press.

[1]There are no known portraits of Rheticus

[2]The Elijah prophecy is from the Talmud not the Bible.

[3]AD CLARISSMUM VIRUM D. IOANNEM SCHONERUM, DE LIBRIS REVOLUTIONUM eruditissimi viri & Mathematici excellentissimi, Reverendi D. Doctoris Nicolai Copernici Torunnaei, Canonici Varmiensis, per quendam Iuvenem, Mathematicae studiosum NARRATIO PRIMA (To that Famous Man Johann Schöner Concerning the Books of Revolutions of That Most Learned Man and Excellent Mathematician, the Venerable Doctor Nicolaus Copernicus of Toruń, Canon of Warmia, by a certain young student of mathematics)

 

 

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The emergence of modern astronomy – a complex mosaic: Part VII

In his Commentariolus from around 1510 Copernicus tells us that his is planning to write a larger more technical work on his heliocentric hypothesis:

However I have thought it well, for the sake of brevity, to omit from this sketch mathematical demonstration, reserving these for my larger work

We don’t actually know when he started writing this work or when he finished it. As a canon of the cathedral of Frombork he was administrator in the prince-bishopric of Varmia, a position that he took seriously throughout his life, meaning that astronomy remained a part time occupation. It would be reasonable to assume that he started on the larger work, which would eventually become De revolutionibus, not long after completing the Commentariolus. Various experts have estimated that he finished the bulk of the book around 1530. However, he was very reluctant to publish, what would become his magnum opus. There is a standard myth that he feared religious censure and thus didn’t want to publish. There is, however, a well-founded theory that he was reluctant to publish because he couldn’t actually deliver what he had promised. In the Commentariolus he assured his readers that his heliocentric system would be simpler that the Ptolemaic geocentric one. In the end the system that he presented in De revolutionibus was more complex than the geocentric one in Peuerbach’s Theoricarum novarum planetarum, published by Regiomontanus in Nürnberg in 1473 from which Copernicus had learnt his astronomy. Also, although Copernicus’ system offered some advantages and simplifications over the geocentric system Copernicus could offer no real proof for his radical suggestion and the empirical physical evidence against a moving earth was still overwhelming. All of this raises the questions would Copernicus have ever submitted his manuscript for publication left to his own devices and what finally pushed him over the edge, so that he did publish? The answer is not what but who. Copernicus was convinced to publish by the young Wittenberger professor of mathematics, Georg Joachim Rheticus (1514–1574). (Note: there are no known portraits of Rheticus)

Rheticus was born Georg Joachim Iserin the son of Georg Iserin, a town physician, and Thomasina de Porris, a minor Italian aristocrat, in Feldkirch in what is now Austria. In 1528 Georg Iserin was found guilty of stealing from his patients, executed and the family name banned in perpetuity. Georg Joachim Rheticus became Georg Joachim de Porris. The family tragedy was alleviated somewhat for the young Georg Joachim, when Achilles Pirmin Gasser (1505–1577), another town physician, historian and astrologer, took over his upbringing and education.

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Achilles Permin Gasser Source: Wikimedia Commons

In 1528 Gasser sent him to the Fraumünster collegiate church in Zurich, where he got to know and became friends with Conrad Gesner (1516–1565), who would go on to become an important sixteenth century polymath.

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Conrad Gesner Source: Wikimedia Commons

In 1532 Gasser sent him to his own alma mater, the Lutheran University of Wittenberg. Here Rheticus, with an obvious aptitude for the mathematical sciences, attracted the attention of Philipp Melanchthon (1497–1560), the rector of the university and founder of the Lutheran Protestant education system.

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Philipp Melanchthon portrait by Lucas Cranach the elder Source: Wikimedia Commons

Melanchthon, who had studied under Johannes Stöffler (1452–1531) and become an enthusiastic fan of astrology, was on the look out for talented mathematicians with whom to equip the new Protestant schools and university to further the growth of a new generation of astronomer/astrologers. It was in Wittenberg that Georg Joachim adopted the toponym Rheticus based in the Roman name for his home district Rhaetia In 1536 Rheticus graduated MA and Melanchthon appointed him professor for the lower mathematics, that is arithmetic and geometry, in Wittenberg.

In 1538 Rheticus took leave of absence from the university to go on an extended study tour of Southern Germany. Such tours were common practice on the mediaeval university and he went with the support of and a letter of introduction from Melanchthon. This letter was addressed to Johannes Schöner in Nürnberg, Philipp Apian in Ingolstadt and Philipp Imser in Tübingen.

The first station on his journey was Nürnberg where he studied astrology with Johannes Schöner (1477–1547) the professor of mathematics at the local gymnasium and a good friend of Melanchthon.

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Johannes Schöner Source: Wikimedia Commons

Here he got to know Nürnberg’s comparatively large mathematical community. He became friends with Georg Hartmann (1489–1564) a leading Renaissance instrument maker

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Georg Hartmann Source: Astronomie in Nürnberg

and with mathematician later theologian Thomas Venatorius (1488­–1551). Rheticus also became acquainted with Johannes Petreius (1497–1550) the leading European printer/publisher of mathematical/astronomical/astrological texts.

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Johannes Petreius Source: Wikimedia Commons

It was almost certainly in Nürnberg that Rheticus became aware of Copernicus, an astronomer in the distant north, who had an interesting new astronomical hypothesis.

I think Rheticus left Nürnberg with a commission from Petreius to go and visit Copernicus and ascertain if he had a book about his heliocentric hypothesis and if so to persuade him to allow Petreius to publish it. There is no known letter of commission and it is probable that none ever existed but there is strong circumstantial evidence to support this theory. When Rheticus left Nürnberg he carried with him six especially bound printed volumes, including three of Petreius’ best mathematical volumes, as a present for Copernicus.  Of course Rheticus’ Narratio Prima, the first ever printed account of Copernicus’ hypothesis, was in the form of an open letter addressed to Schöner in Nürnberg, who had close connections with Petreius. Rheticus received an answer to his Narratio Prima in the form of a letter from Andreas Osiander  (1498–1552), Nürnberg’s Lutheran preacher, who worked as an editor for Petreius and who would go on to edit De revolutionibus.

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Andreas Osiander portrait by Georg Pencz Source: Wikimedia Commons

But if Rheticus was fulfilling a commission for Petreius, what did he get out of the deal. Consideration of the legal dispute over his mother’s will indicate that Rheticus was independently wealthy, so some sort of financial payment was probably not involved. However, in 1538 Rheticus was a young, unknown academic at the very beginning of his career and Petreius, as a leading European printer/publisher, was in a position to offer him career-advancing inducements. In 1542 Petreius published an edition of two speeches that Rheticus had held in Wittenberg, Orationes duae prima de astronomia & geographia altera de physica, habitae Vuittebergae / à Ioachimo Rhetico. Neither of these speeches is particularly significant and well below the level of academic text that Petreius usually published, certainly a step up for a novice academic. On 1 August 1540 Petreius went a step further dedicating to Rheticus his edition of the fourteenth-century physician Antonius de Motulmo’s De iudiciis nativitatum, one of the manuscripts brought to Nürnberg by Regiomontanus and edited by Schöner. In the sixteenth century book dedications were important and valuable instruments of credit, most often used to win the favour of important and wealthy patrons, to dedicate such a book to a mere mathematicus, and a novice at that, was a great honour indeed. The dedication is in the form of a fairly long letter, which praises Rheticus highly and urges him to bring Copernicus’ book to Petreius in Nürnberg for publication. Lastly in 1541 Petreius began to publish the annual prognostica of Achilles Gasser, Rheticus’ mentor. Rich rewards for Rheticus’ services.

There, of course, remains the question, would Petreius issue such a commission? The answer is a resounding yes. Having come across Girolamo Cardano’s Practica arithmetice et mensurandi singularis at the Frankfurt Book Fair he instructed Osiander to write to Cardano offering to become his Northern European publisher. Cardano quickly accepted the offer and the Cardano-Petreius partnership proved very profitable for both of them with Petreius publishing Cardano’s best selling volumes on mathematics, astrology, medicine and philosophy. Petreius also commissioned Walter Hermann Ryff (c. 1500–after 1551), a man perhaps best described as a sixteenth-century scientific hack, to produce the first German translation of Vitruvius’ De architectura, Vitruvius Teutsch: Nemlichen des aller namhafftigisten vn[d] hocherfarnesten, Römischen Architecti, und Kunstreichen Werck oder Bawmeisters, Marci Vitruuij Pollionis, Zehen Bücher von der Architectur vnd künstlichem BawendEin Schlüssel vnd einleytung aller Mathematische[n]. Lastly Petreius negotiated with Erasmus Reinhold (1511–1553), Rheticus’ fellow professor of mathematics in Wittenberg, to publish an edition of his extensive horoscope collection. Petreius had earlier published Cardano’s collection with great success. However this project together with Petreius’ planned publication of Reinhold’s Tabulae prutenticae collapsed with Petreius’ death in 1551.

It is often argued that Copernicus could not have know about the Archimedean manuscript The Sand Reckoner with its references to Aristarchus’ heliocentric hypothesis, as this was first published in Basel in 1544. However, Rheticus could have brought that knowledge with him from Nürnberg, as Venatorius was the editor of that Latin/Greek edition of the works of Archimedes published in Basel, based on a Greek manuscript brought to Nürnberg from Rome by Willibald Pirckheimer (1470-1530) and the Latin translation of Jacobus Cremonensis from the manuscript collection of Regiomontanus.

Leaving Nürnberg in 1539, Rheticus did not immediately head north to Frombork. There is no corroborative evidence that he visited Philipp Apian (1531–1589) the professor for mathematics in Ingolstadt but he did go to Tübingen. Melanchthon’s letter of introduction was addressed to Philipp Imser (1550–1570), Stöffler’s successor as professor of mathematics in Tübingen, however just at this time Imser was, following religious differences, suspended from his chair and Rheticus, instead, met up with Joachim Camerarius (1500-1574), humanist scholar, close friend of Melanchthon and his later biographer. Camerarius was another member of the Nürnberger group, who had been rector of the local gymnasium, appointed by Melanchthon, and had worked extensively as an editor for Petreius. Since 1535 he had been rector of the University of Tübingen and would later have a major influence on Rheticus’ career. From Tübingen Rheticus travelled home to Feldkirch, where he visited Achilles Gasser and whence he set out on his journey to Varmia and his fateful meeting with Copernicus.

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