Category Archives: Renaissance Science

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

In 1542 the manuscript of De revolutionibusarrived 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?


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.


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).


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.


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.


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).


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.


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.


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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Filed under Early Scientific Publishing, History of Astrology, History of Astronomy, Renaissance Science

Renaissance Heavy Metal

One of the most fascinating and spectacularly illustrated Renaissance books on science and technology is De re metallica by Georgius Agricola (1494–1555). Translated into English the author’s name sounds like a figure from a game of happy families, George the farmer. In fact, this is his name in German, Georg Pawer, in modern German Bauer, which means farmer or peasant or the pawn in chess. Agricola was, however, anything but a peasant; he was an extraordinary Renaissance polymath, who is regarded as one of the founders of modern mineralogy and geology.


Georg Bauer was born in Glauchau on 24 March 1494, the second of seven children, to Gregor Bauer (born between 1518 and 1532) a wealthy cloth merchant and dyer. He was initially educated at the Latin school in Zwickau and attended the University of Leipzig, where he studied theology, philosophy and philology from 1514 to 1517. From 1518 to 1522 he worked as deputy director and then as director of schools in Zwickau. In 1520 he published his first book, a Latin grammar. The academic year 1522-23 he worked as a lecturer at the University of Leipzig. From 1523 to 1526 he studied medicine, philosophy and the sciences at various Northern Italian university graduating with a doctorate in medicine. In Venice he worked for a time for the Manutius publishing house on their edition of the works of Galen.

From 1527 to 1533 Agricola worked as town physician in St. Joachimsthal*, today Jáchymov in the Czech Republic. In those days Joachimsthal was a major silver mining area and it is here that Agricola’s interest in mining was ignited.


Silver mining in Joachimsthal (1548) Source: Wikimedia Commons

In 1530 he issued his first book on mining, Bermannus sive de re metallica, published by the Froben publishing house in Basel. It covered the search for metal ores, the mining methods, the legal framework for mining claims, the transport and processing of the ores. Bermannus refers to Lorenz Bermann, an educated miner, who was the principle source of his information. The book contains an introductory letter from Erasmus, who worked as a copyeditor for Froben during his years in Basel.

In 1533 he published a book on Greek and Roman weights and measures, De mensuris et ponderibus libri V, also published Froben in Basel.


From 1533 to his death in 1555 he was town physician in Chemnitz. He was also district historian for the Saxon aristocratic dynasty. From 1546 onwards he was a member of the town council and served as mayor in 1546, 1547, 1551 and 1553. In Chemnitz he also wrote a book on the plague, De peste libri tres, his only medical book,  as ever published by Froben in 1554.


Source: Internet Archive

Having established himself as an expert on mining with the Bermannus, Agricola devoted more than twenty years to studying and writing about all aspects of mining and the production of metals. He wrote and published a series of six books on the subject between 1546 and 1550, all of them published by Froben.

De ortu et causis subterraneorum libri V, Basel 1546

The origin of material within the earth

De natura eorum, quae effluunt ex terra, Basel 1546

The nature of the material extruded out of the earth

De veteribus et novis metallis libri II, Basel 1546

Ore mining in antiquity and in modern times

De natura fossilium libri X, Basel 1546

The nature of fossils whereby fossils means anything found in the earth and is as much a textbook of mineralogy

De animantibus subterraneis liber, Basel 1549

The living underground

De precio metallorum et monetis liber III, 1550

On precious metals and coins

At the same time he devoted twenty years to composing and writing his magnum opus De re metallica, which was published posthumously in 1556 by Froben in Basel, who took six years to print the book due to the large number of very detailed woodcut prints with which the book is illustrated. These illustrations form an incredible visual record of Renaissance industrial activity. They are also an impressive record of late medieval technology. Agricola’s pictures say much more than a thousand words.

De re metallicahas twelve books or as we would say chapters. What distinguishes Agricola’s work from all previous writings on mineralogy and geology is the extent to which they are based on empirical observation rather than philosophical speculation. Naturally this cannot go very far as it would be several hundred years before the chemistry was developed necessary to really analyse mineralogical and geological specimens but Agricola’s work was a major leap forward towards a modern scientific analysis of metal production.


Book I: Discusses the industry of mining and ore smelting

Book II: Discusses ancient mines, finding minerals and metals and the divining rod

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Book III: Discusses mineral veins and seams and plotting with the compass

Book IV: Discusses the determination of mine boundaries and mine organisation

Book V: Discusses the principles of mining, the metals, ancient mining and mine surveying

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Book VI: Discusses mining tools and equipment, hoists and pumps, ventilation and miners’ diseases

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Book VII: Discusses assaying ores and metals and the touchstone

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Book VIII: Discusses preparing ores for roasting, crushing and washing and recovering gold by mercury

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Book IX: Discusses ores and furnaces for smelting copper, iron and mercury and the use of bellows

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Book X: Discusses the recovery of precious metals from base metals as well as separating gold and silver by acid

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Book XI: Discusses the recovery of silver from copper by liquidation as well as refining copper

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Book XII: Discusses salts, solvents, precipitates, bitumen and glass

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Agricola’s wonderfully illustrated volume became the standard reference work on metal mining and production for about the next two hundred years. The original Latin edition appeared in Basel in 1556 and was followed by a German translation in 1557, which was in many aspects defective but remained unchanged in two further editions. There were further Latin editions published in 1561, 1621, and 1657 and German ones in 1580, and 1621, with an improved German translation in 1928 and 1953. There was an Italian translation published in 1563.

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Of peculiar interest is the English translation. This was first published in 1912 in London, the work of American mining engineer Herbert Hoover (1874–1964) and his wife the geologist Lou Henry (1874–1944). A second edition was published in 1950. Hoover is, of course, better know as the 31stPresident of the USA, who was elected in 1928 and served from 1929–1933.


Herbert Hoover in his 30s while a mining engineer Source: Wikimedia Commons


Lou Henry, circa 1930 Source: Wikimedia Commons

Agricola’s tome also represents an important development in the history of trades and professions. Before De re metallicaknowledge of trades and crafts was past from master to apprentice verbally and kept secret from those outside of guild, often on pain of punishment. Agricola’s book is one of the first to present the methods and secrets of a profession in codified written form for everyone to read, a major change in the tradition of knowledge transfer.

*A trivial but interesting link exists between St. Joachimsthal and the green back. A silver coin was produced in St. Joachimsthal, which was known as the Joachimsthaler. This got shortened in German to thaler, which mutated in Dutch to daalder or daler and from there in English to dollar.

All illustrations from De re metallica are taken from Bern Dibner, Agricola on Metals, Burndy Library, 1958






Filed under Early Scientific Publishing, History of Technology, Mediaeval Science, Renaissance Science

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.


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.


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,


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.


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.


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).


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].


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),


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.


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.


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)




Filed under Early Scientific Publishing, History of Astrology, History of Astronomy, Renaissance Science

History of science on the Internet – the gift that keeps giving

Dear readers it is time once again for the Hist–Sci Hulk to flex his muscles and give a couple of Internet authors a good kicking for the crime of spreading history of science nonsense. First up we have a website called StarTeach Astronomy Education, who describe themselves as follows:


StarTeach Astronomy Education is a multimedia web-based astronomy education program designed especially for K-12 students and their teachers. The primary goal of the program is to aid in the classroom instruction of astronomy by providing a multimedia supplement that is available to schools with internet capability. In addition, it can also be used as research material for individual students.

The StarTeach Astronomy Education Program was created by Leslie Welser when she was a graduate student in the University of Nevada, Reno Physics Department. StarTeach has been recently updated to include topics for more advanced readers.

The section to which my attention was inadvertently directed was under the drop down menu Ancient Cultures with the title Arab and Islamic Astronomy.

Alone this title causes problem. Only yesterday I had an Internet exchange with Peter Adamson, the excellent creator of the History of Philosophy Without Any Gaps podcast and author of many books and articles based on that podcast, how exactly to describe the philosophy and science produced in the Middle Ages by the inhabitants of those areas of the world dominated by Islamic culture. The answer is certainly not Arab and Islamic, which would seem to suggest two separate areas of production or if only one that the astronomy was only produced by Islamic Arabs. The latter is definitively not the case as we have Arabs, Jews, Persians, Syriac Christians and various others. The subject is complex enough to warrant its own blog post, which I might or might not write sometime in the future.

The article opens with the following:

During the period when Western civilization was experiencing the dark ages [my emphasis], between 700-1200 A.D., an Islamic empire stretched from Central Asia to southern Europe.

The sound you can hear echoing around the world, is the sound of thousands of medievalist weeping and rending their clothes at the use of the term ‘the dark ages’. The preferred term is Early Middle ages. I should point out that the Arabic-Islamic dominance of a substantial part of the Eurasian landmass extended several centuries past 1200 CE and one of the things that Peter Adamson and I discussed is the fact that this empire actually split up fairly early into competing caliphates. Leaving out some minor quibbles we now come to this:

Another important religious use for astronomy was for the determination of latitude and longitude. Using the stars, particularly the pole star, as guides, several tables were compiled which calculated the latitude and longitude of important cities in the Islamic world.

Whereas you can determine latitude using altitude of the sun or the pole star and a bit of relatively simple trigonometry, you cannot determine longitude in this way. In fact the only way available in the Middle Ages to determine longitude astronomically is by simultaneous observation of eclipses, lunar or solar, and then comparing the timings. Next up with have:

Aside from religious uses, astronomy was used as a tool for navigation. The astrolabe, an instrument which calculated the positions of certain stars in order to determine direction, was invented by the Greeks and adopted and perfected by the Arabs (see picture below).

To quote David King, one of the world’s leading authorities on both the astrolabe and Islamic astronomy, the astrolabe was never used for navigation! It was actually the next sentences that finally provoked me into writing this blog post:

The sextant was developed by the Arabs to be a more sophisticated version of the astrolabe. This piece of technology ultimately became the cornerstone of navigation for European exploration.

When I first read this wonderful bullshit-double-whammy, I seriously started banging my head on my desk and praying for quick release from my pain. We are here confronted by a common problem in the history of science, the use of the same name for two or more completely different instruments. Our, by the way anonymous, I wouldn’t want to attach my name to this crap either, author apparently has no idea that the astronomical sextant and the navigational sextant are two completely different beast that apart from a scale representing one sixth of a circle, hence the name, have very little in common.

The astronomical sextant, to which the author intended to refer here, is anything but more sophisticated than the astrolabe and is in fact much, much simpler. It is a simple scale engraved on a segment, one sixth of a circle, with sights mounted on it used to determine the position of stars. I refer the reader to the Wikipedia article for more details. The navigational sextant, also not derived from the astrolabe, is a much more complex beast invented in the seventeenth century, the story of which you can read here. A change of topic:

Science was considered the ultimate scholarly pursuit in the Islamic world, and it was strongly supported by the nobility. Most scientists worked in the courts of regional leaders, and were financially rewarded for their achievements. In 830, the Khalifah, al-Ma’muun, founded Bayt-al-Hikman, the ‘House of Wisdom’, as a central gathering place for scholars to translate texts from Greek and Persian into Arabic. These texts formed the basis of Islamic scientific knowledge.

I think Qur’anic scholars might well dispute the claim that “Science was considered the ultimate scholarly pursuit in the Islamic world.” Another topic to which I might one day devote a whole blog post is the fact that the House of Wisdom, as it is usually presented, such as here, is a myth. For details see Dimitri Gutas, Greek Thought, Arabic Culture: The Graeco-Arabic Translation Movement in Baghdad and Early ‘Abbāsid Society (2nd–4th/8th–10thcenturies).

I could go on and on but I will just consider one last gem:

One of the greatest Islamic astronomers was al-Khwarizmi (Abu Ja’far Muhammad ibn Musa Al-Khwarizmi), who lived in the 9th century and was the inventor of algebra[my emphasis].

The ancient Babylonians and the Indians would be amazed to discover that al-Khwarizmi invented algebra. His book, Al-kitāb al-mukhtaṣar fī ḥisāb al-ğabr wa’l-muqābala, introduced algebra into medieval Europe and part of its title gave the discipline its modern name but algebra was being practice literally millennia before al-Khwarizmi was born.

Interestingly this dog’s dinner of an article, that is intended to educate school kids, isn’t based on academic literature on the subject but offers as its sources links to five other Internet articles, three of which no longer exist and one of which is about the navigational sextant and as such irrelevant.

My second candidate for a Hist_Sci Hulk kicking is from Quillette a self styled platform for free thought and is a review by Jared Marcel Pollen (whoever he is) of Ben Shapiro’s The Right Side of History. An extremely tedious review of an extremely tedious book by an extremely tedious person that wouldn’t normally occupy my thought stream for longer than thirty seconds were it not for the following totally fucked up piece of history of astronomy.

This also allows Shapiro to skirt the obvious hostility the church showed toward intellectual inquiry for centuries. Shapiro writes as if the church had never banned a book or burned a heretic:

Contrary to popular opinion, new discoveries weren’t invariably seen as heretical or dangerous to the dominion of the Church; in fact, the Church often supported scientific investigation.

The Church was indeed the only place where any kind of inquiry could be conducted at the time. It was the only place where people were literate and enjoyed steady funding and access to instruments. But the Church only encouraged inquiry to the extent that it could reinforce and expand its own doctrine, which is a bit like the state telling you that you are free to make whatever art you like, just as long as you don’t criticize the regime.

What we have here is the standard popular presentation of the medieval Catholic Church as some sort of all-powerful totalitarian state. The reality was actually somewhat different. The Church was not able to exercise the sort of total intellectual control that Pollen is here claiming and surprisingly diverse positions were possible and existed in reality .

Also Pollens claim that, “The Church was indeed the only place where any kind of inquiry could be conducted at the time. It was the only place where people were literate and enjoyed steady funding and access to instruments” is of course total rubbish. Just to take the example of the three leading writers on astronomy in the reception phase of Copernican heliocentricity–Tycho Brahe, Johannes Kepler and Galileo Galilei–all three of them were court mathematicians outside of the various churches. There are plenty of other examples of important and influential scholars from this period, who found employment outside of the churches.

The first major scientific challenge to the Church was heliocentrism. But Shapiro claims this was hardly an issue: “Nicolas Copernicus studied in parochial school and served the Church of Warmia as medical advisor; his publication of De revolutionibus… in March 1542, included a letter to Pope Paul III.”

Copernicus was in fact a canon of Frombork cathedral and as such part of the government of the prince-bishopric of Warmia. His role was much wider than that of cathedral physician. De revolutionibus was published in 1543 not 1542 but did in fact contain a dedicatory letter to Pope Paul II.

In fact, Copernicus had finished his treatise years earlier (there are records indicating that the manuscript had been completed as early as the 1530s), but he withheld it, aware that its publication could be life-threatening, and circulated only a few anonymous copies to his close friends.

The bulk of De revolutionibus was, as far as we can tell, finished by about 1530, however the reasons for Copernicus not publishing at that time are complex and contrary to popular opinion had very little to do with any fear of persecution by the Church and its publication would certainly not have been life-threatening; that claim is complete rubbish based on hindsight and fail interpretations of the cases of Giordano Bruno and Galileo Galilei. Despite censoring Copernicus for his relationship with his housekeeper, Danticus, the Prince-Bishop of Warmia, supported Copernicus work and even invited Gemma Frisius, who Danticus supported, to come to Frombork to work with Copernicus. Tiedmann Giese, Bishop of Kulm, an influential cleric and Copernicus’ best friend, had been urging him to publish for years. Lastly Nicholas Schönberg, Cardinal of Capua, wrote a letter to Copernicus urging him to make his work public. This letter was included in the front material of De revolutionibus. As can be seen Copernicus had solid support for his work within the Church hierarchy. After its publication there was no initial opposition to De revolutionibus from the side of the Church. Copernicus is considered to have held back with publication because he couldn’t provide the proof of the heliocentric hypothesis that he wished to. There were no anonymous copies of De revolutionibus circulated to close friends! I assume our author is confusing De revolutionibus with the Commentariolus, Copernicus unpublished manuscript, which first propagated his heliocentric hypothesis from around 1510.

The book was only published in its entirety on the eve of Copernicus’s death, and the letter to the pope, which was also anonymous, was not written by Copernicus, but by Andreas Osiander, a Lutheran preacher who had been given the job of overseeing the book’s publication. It was an attempt to soften the blow, and states, inter alia, that the author’s findings are only meant to aid the computation of the heavens, and do not even need to be considered true in order for the calculations to be useful.

The implication that Copernicus only gave De revolutionibus free for publication when he was dying is once again total rubbish. Rheticus took the finished manuscript away from Frombork in September 1541 more than eighteen months before Copernicus’ demise. The next sentence is mindboggling for anybody who knows anything about De revolutionibus and its publication history. Copernicus dedicated De revolutionibus to His Holiness Pope Paul III. The anonymous text added by Andreas Osiander during publication was the infamous ad lectorem a totally different text altogether.

The Church would continue to uphold the geocentric model for at least another 150 years, and wouldn’t get around to officially pardoning Galileo until 1992. However, Shapiro claims the persecution of Galileo was merely a PR move by the Church; an attempt to crack down on dissent in response to Protestant accusations of leniency and hypocrisy. The trial of Galileo also saw dozens of astronomical works, including De Revolutionibus, placed on the Church’s “List of Prohibited Books”

Not the geocentric but the geo-heliocentric model of Tycho Brahe, was upheld not only by the Church but also by a very large number astronomers for many decades because the heliocentric model proved extremely difficult to prove. I can’t really comment on Shapiro’s claim, not having read his book and not intending to do so, but whatever the Church’s reasons for the persecution Galileo, and they are very complex, they have absolutely nothing to do with Protestant accusations of leniency and hypocrisy. Galileo is said to have obtained permission from Urban to write his Dialogo, because he claimed that the Protestants were mocking the Catholic Church because of its ignorant stance in the astronomy/cosmology debate. It would appear that Shapiro got his fact confused to put it diplomatically.

“Dozens of astronomical works” is a crass exaggeration and those books that were placed on the Index were placed there in 1616, following Galileo’s first run in with the Church and not in 1633 following his trial. Interestingly, and I get weary of repeating this, De revolutionibus was only placed on the Index until corrected, which surprisingly was completed by 1620; the corrected version with only those parts corrected which claimed heliocentricity to be a fact rather than a hypothesis, was then given free by the Church.

What we have here in total is a collection of half remember facts and myths stirred up together with an added sauce of nonsense and then spewed onto the page without any consideration for truth, facts or accuracy. Kind of sums up Quillette in my opinion.






Filed under History of Astronomy, History of Mathematics, Renaissance Science

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.


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.


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.


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.


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


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.


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.


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.


Filed under History of Astrology, History of Astronomy, Renaissance Science

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

Copernicus first put his concept for a heliocentric cosmos in writing in a manuscript that today bears the title Nicolai Copernici de hypothesibus motuum coelestium a se constitutis commentariolus (roughly translated: Nicolas Copernicus’ short commentary on his hypothesis about the movement of the celestial bodies) of which three manuscripts are known to exist today. None of them, however, in Copernicus’ own handwriting. There is almost no direct evidence for the existence of this document in the sixteenth century and almost everything that we can say about its origin, its distribution and its impact is based on reasonable, speculative interpretation of indirect evidence.

It is disputed whether the title Commentariolus, for short, was written by Copernicus or was added at a later date; it has been speculated that it was added by Tycho Brahe, who possessed a copy, which is one of the three surviving copies and is now housed in the Viennese Court Library. In his Astronomiae Instauratae Progymnasmata (1602) Tycho wrote that his copy was given to him by Thaddaeus Hagecius (1525–1600). He also said that he had made several copies and distributed them to friends.


Title page of the Viennese Commentariolus manuscript Source: Wikimedia Commons

The Viennese manuscript was first found in 1877 but it is incomplete, missing a substantial part of Copernicus’ lunar theory. In 1881 a complete manuscript was found in the library of the Stockholm Observatory bound into a second edition of De Revolutionibus, which had been the property of Hevelius. The third manuscript was also found bound into a second edition of De revolutionibus that had belonged to Duncan Liddel (1561–1613) in the library of Saint Andrews University in Scotland. Liddel studied at various North German universities and was later a professor for mathematics at Helmstedt University before going on to qualify as a physician and becoming a professor for medicine. A fairly normal career path in the sixteenth century. He knew Tycho Brahe and visited him at least twice on the island of Hven. It should be noted that all three surviving copies of the Commentariolus were owned by people who lived after the publication of De revolutionibus and the death of its author.

The first probably mention of the Commentariolus occurred in 1514. The Cracovian physician, geographer and historian, Matthias of Miechow (1457–1523) noted in a library catalogue in the Jagiellonian Library dated 1 May 1514 the following:

Item sexternus theorice asserentis terram moveri, Solem vero quiescere

A quire of six leaves (sexternus) of a theory asserting that the Earth moves whereas the Sun is at rest.

It is assumed that this is a reference to the Commentariolus, probably a copy originally given by Copernicus to his Cracovian friend Canon Bernard Wapowski (1450–1535) a cartographer and historian.


Excerpt from the library catalogue of Matthias von Miechow (1457–1523) 1. Mai 1514 with the Commentariolus hint: „Item sexternus theorice asserentis terram moveri, Solem vero quiescere“. Source: Wikimedia Commons

There are no direct references to the Commentariolus before the publication of De Revolutionibus in 1543. However, there are various episodes in Copernicus’ life that can probably be attributed to knowledge of the Commentariolus.

Paul of Middelburg (1446–1534) sent out a general call to astronomers and rulers asking for suggestions and contributions towards a proposed calendar reform at the Lateran Council (1512–1517). Paul noted in 1516 that one of those who answered that call was Copernicus in a letter that no longer exists. Perhaps Copernicus was on Paul’s list because of the Commentariolus, he had at this point published no other astronomical works that might have motivate Paul to consult him.

In 1533 Johann Albrecht Widmannstetter (1506–1557), who was a papal secretary held a series of lectures to an audience of Pope Clement VII and some cardinals outlining Copernicus’ heliocentric theories for which he was richly rewarded by the Pope with a rare manuscript. It can be assumed that his source of knowledge of those theories was the Commentariolus.  Following the death of Pope Clement in 1534 Widmannstetter became secretary to Cardinal Nikolaus von Schönberg (1472–1537), who wrote a letter to Copernicus in 1536 concerning his theories and offering to have the manuscript of his theories (De revolutionibus) copied at his expense. This letter would be included in the published version of De revolutionibus.

In 1539 Martin Luther (1483–1546), in his cups, reputedly launched an attack on Copernicus’ heliocentric hypothesis, as recorded by Anton Lauterbach in the Tischreden (Table Talk) first published in 1566. (More details here)

There was mention of a certain astrologer who wanted to prove that the earth moves and not the sky, the sun, and the moon. This would be as if somebody were riding on a cart or in a ship and imagined that he was standing still while the earth and the trees were moving. [Luther remarked] “So it goes now. Whoever wants to be clever must agree with nothing that others esteem. He must do something of his own. This is what that fellow does who wishes to turn the whole of astronomy upside down. Even in these things that are thrown into disorder I believe the Holy Scriptures, for Joshua commanded the sun to stand still and not the earth [Jos. 10:12].”

Copernicus was not mentioned by name in Luther’s tirade and also no great details of the hypothesis. It can be assumed that indirect knowledge of the Commentariolus had come to Luther’s ears.

Our last possible indirect knowledge of the Commentariolus can be attributed to Georg Joachim Rheticus (1514–1574), who famously persuaded Copernicus to publish De revolutionibus. Rheticus set off for Frombork in 1539 already aware of the fact that Copernicus was propagating a heliocentric hypothesis. Did this knowledge come directly or indirectly from the Commentariolus?

So what does the Commentariolus consist of? In a very brief introduction Copernicus writes:

           Our Ancestors assumed, I observe, a large number of celestial spheres for this reason especially, to explain the apparent motion of the planets by the principle of regularity. For they thought it altogether absurd that a heavenly body, which is a perfect sphere, should not always move uniformly. They saw that by connecting and combining regular motions in various ways they could make any body appear to move to any position.

Callippus and Eudoxus, who endeavoured to solve the problem by use of concentric spheres, were unable to account for all planetary movements; they had to explain not merely the apparent revolutions of the planets but also the fact that these bodies appear to us sometimes to mount higher in the heavens, sometimes to descend; and this fact is incompatible with the principle of concentricity. Therefore it seemed better to employ eccentrics and epicycles, a system which most scholars finally accepted.

Yet the planetary theories of Ptolemy and most other astronomers, although consistent with the numerical data, seemed likewise to present no small difficulty. For these theories were not adequate unless certain equants were also conceived; it then appeared that a planet moved with uniform velocity neither on its deferent nor about the center of its epicycle. Hence a system of this sort seemed neither sufficiently absolute nor sufficiently pleasing to the mind.

Having become aware of these defects, I often considered whether there could perhaps be found a more reasonable arrangement of circles, from which every apparent inequality would be derived and in which everything would move uniformly about its proper center, as the rule of absolute motion require. After I had addressed myself to this very difficult and almost insoluble problem, the suggestion at length came to me how it could be solved with fewer and much simpler constructions than were formally used, if some assumptions (which are axioms) were granted me. They follow in this order[1].

In this brief introduction, which I have given here in full, Copernicus makes very clear why he thinks that astronomy needs reforming. He is in principle quite happy with an epicycle-deferent model but not with the use of equants, which he sees as violating the fundamental principle of uniform circular motion, a philosophically founded astronomical axiom that he wholeheartedly accepts. The equant point is an abstract off-centre point inside the orbit of a planet, which when used as the viewing point gives the planet on its epicycle-deferent uniform motion.


equant: A sphere that is centered at the center of the universe, but whose motion varies irregularly as if it were centered at another spot, called the equant point. This geometrical tool allowed Ptolemaic astronomers to construct orbits with the observed variations of speed without resorting to the ugliness of a sphere that was actually off center (an eccentric). The Planet is actually on the outer circle below, centered at E, the center of the universe. The sphere, however, moves as if it were centered at the point marked equant below, so that it takes equal times for the planet to move from 1 to 2, from 2 to 3, from 3 to 4 and from 4 back to 1, even though the distances vary. This produces a variation in the observed speed of the planet. Source

What is interesting is that he gives no indication of the bombshell that he is about to lob into the astronomy-cosmology debate with the assumptions that he wishes to be granted by his readers. They follow immediately on the introduction. He merely wishes to substitute a heliocentric system for the universally accepted geocentric system. Even more interesting, and totally frustrating for historians of astronomy, he gives absolutely no indication whatsoever how or why he came to adopt this radical step in order to rescue the uniform circular motion axiom. Copernicus’ assumptions (axioms) read as follows[2]:

1: There is no one center of all the celestial circles or spheres.

That there is, is one of the fundamental axioms of Aristotelian cosmology

2: The center of the earth is not the center of the universe, but only of gravity and the lunar sphere

That the earth is the centre of the universe is another of the Aristotelian axioms

3: All the spheres revolve about the sun as their mid-point, and therefore the sun is the center of the universe.

Bombshell lobed without comment!

4: The ratio of the earth’s distance from the sun to the height of the firmament is so much smaller than the ratio of the earth’s radius to its distance from the sun that the distance from the earth to the sun is imperceptible in comparison with the height of the firmament.

Copernicus needs this assumption to explain the lack of observable stellar parallax. Much is made of Copernicus’ vast increase in the size of the cosmos in comparison to Ptolemaeus. However in the Almagest Ptolemaeus states, “Moreover, the earth has, to the senses, the ratio of a point to the distance of the sphere of the so-called fixed stars[3].” Even Ptolemaeus’ cosmos is in principle unimaginably large.

5: Whatever motion appears in the firmament arises not from any motion of the firmament, but from the earth’s motion. The earth together with its circumjacent elements performs a complete rotation on its fixed poles in a daily motion, while the firmament and highest heaven abide unchanged.

The concept of diurnal rotation, the earth’s daily rotation about its own axis, had been hypothesised on many occasions throughout the history of astronomy as I explained in an earlier blog post. Copernicus would call upon some of those earlier examples as support for his own views in De revolutionibus. More interesting is the phrase “together with its circumjacent elements”, where Copernicus is basically saying that the earth carries its atmosphere with it when it rotates. This counters some of the arguments already listed by Ptolemaeus against diurnal rotation. The problem for Early Modern supporters of heliocentricity or simply diurnal rotation is they lacked the physics to explain how the earth could carry its atmosphere with in on its daily spin. We will return to this topic in a later episode.

6: What appear to us as motions of the sun arise not from its motion but from the motion of the earth and our sphere, with which we revolve around the sun like any other planet. The earth has, then, more than one motion.

The first sentence merely confirms the consequences of a heliocentric model. The second states another break with the Aristotelian axioms. According to Aristotle celestial bodies have just one type of natural motion, uniform circular motion and the earth also has just one type of natural motion upward or downward perpendicular to the earth’s surface.

7: The apparent retrograde and direct motion of the planets arises not from their motion but from the earth’s. The motion of the earth alone, therefore, suffices to explain so many apparent inequalities in the heavens.

This last assumption is, of course, the biggest selling point for the adoption of a heliocentric system but in the debates following the publication of De revolutionibus, the other arguments against heliocentricity weighed so heavily that this explanation for retrograde planetary motion got largely ignored.


Second page of the Stockholm manuscript with the assumptions Source: Wikimedia Commons

Copernicus now begins to fill in the details:

            Having set forth these assumptions, I shall endeavor briefly to show how uniformity of the motions can be saved in a systematic way. However I have thought it well, for the sake of brevity, to omit from this sketch mathematical demonstrations…[4]

Once again we have a confirmation that Copernicus’ main interest, as he sees it, is to restore the uniform circular motion axiom. I shall not into detail about the rest but the section headings are:

The Order of the Spheres

The Apparent Motion of the Sun

Equal Motion Should Be Measured Not by the Equinoxes but by the Fixed Stars

The Moon

The Three Superior Planets Saturn–Jupiter–Mars



Of interest here is that some of the epicycle-deferent models he outlines here differ from those that he would later develop for De revolutionibus indicating that this is an initial concept that would undergo development in the following thirty plus years, although he announces his intention to produce a larger more detailed work in the sentence I broke off above:

However I have thought it well, for the sake of brevity, to omit from this sketch mathematical demonstration, reserving these for my larger work[6].

We have no idea how many copies of the Commentariolus Copernicus made and distributed or how many further copies were made by others. As I have indicated above there is circumstantial evidence that it was read but the lack of any direct mentions before the publication of De revolutionibus, plus the fact that there seems to have been no heliocentricity debate triggered by it, as opposed to the debate triggered by Fracastoro’s Homocentrica (1538),and a couple of other contemporary published texts on the homocentric spheres model, indicate that the Commentariolus had very little impact on the sixteenth-century astronomical community.

















[1]3 Copernican Treatises: The Commentariolus of Copernicus, The Letter Against Werner, The Narratio Prima of Rheticus, Translated with Introduction, Notes and Bibliography by Edward Rosen, Dover Publications, Inc., New York, 1959 pp. 57-58

[2]Copernicus/Rosen pp. 58-59

[3]Ptolemy’s AlmagestTranslated and Annotated by G. J. Toomer, Princeton University Press, Princeton New Jersey, ppb. 1998 p. 43

[4]Copernicus/Rosen p. 59

[5]Copernicus/Rosen pp. 59-90

[6]Copernicus/Rosen p. 59


Filed under Early Scientific Publishing, History of Astronomy, Renaissance Science, Uncategorized

Nit-picking – Authors who should know better

In my most recent reading I have come across three separate examples of professional historians making a mess of things when they turn the hand to the history of science.

First up we have Jerry Brotton’s The Renaissance: A Very Short Introduction[1]. I’m a fan of Oxford University Press’ Very Short Introduction series and also of Brotton’s A History of the World in Twelve Maps[2], so I was expecting to enjoy his Very Short Introduction to the Renaissance and in general I wasn’t disappointed.

Nit Picking001

He chooses to lay the emphasis in his book on the fact that the Renaissance wasn’t a purely European phenomenon but a global one and writing from this perspective he opens up a novel vista on this period of history. However when he turns to the history of Renaissance science he, in my opinion, drops a major clangour.

He introduces his chapter on the topic with Christopher Marlowe’s Doctor Faustus, telling us that:

Once Faustus has sold his soul, he asks Mephistopheles for a book ‘where I might see all characters and planets of the heavens’. The most controversial book that Faustus could have consulted was On the Revolutions of the Celestial Spheres by the Polish canon and astronomer Nicolaus Copernicus.[3]

We’ll ignore the Polish on this occasion and turn instead to what Brotton says about the book:

Copernicus’s revolutionary book overturned the medieval belief that the earth lay at the centre[my emphasis] of the universe. Copernicus’s vision of the heavens showed, along with all the other known planets, rotated around the sun. Copernicus subtly revised the work of classical Greek and Arabic astronomy scholars. He argued that ‘they did not achieve their aim, which we hope to reach by accepting the fact that the earth moves’.

Copernicus tried to limit the revolutionary significance of his ideas by accommodating them within a classical scientific tradition. But the Catholic Church was horrified and condemned the book. Copernicus’s argument overturned the biblical belief that the earth – and humanity with it – stood at the centre of the universe[4][my emphasis].


It was neither the biblical nor the medieval belief that the earth stood at the centre of the universe and removing the earth from this centre was not Copernicus’ offence. It was setting the earth in motion and stopping the motion of the sun that the Church found intolerable, as it contradicted several biblical passages. The myth about Copernicus displacing humanity from the centre of the universe is as far as I know and eighteenth or even nineteenth century invention and actually contradicts the medieval view of the position of the earth. The earth was not at the centre but at the bottom of the universe in the dregs. I once wrote a short blog post quoting Otto von Guericke on this subject, for those to lazy to click through:


Since, however, almost everyone has been of the conviction that the earth is immobile since it is a heavy body, the dregs, as it were, of the universe and for this reason situated in the middle or the lowest region of the heaven

Otto von Guericke; The New (So-Called) Magdeburg Experiments of Otto von Guericke, trans. with pref. by Margaret Glover Foley Ames. Kluwer Academic Publishers, Dordrecht/Boston/London, 1994, pp. 15 – 16. (my emphasis)

Need I really point out that the Church didn’t condemn De revolutionibus but in 1616 merely placed it on the Index until corrected, a procedure that was carried out with surprising rapidity. A small number of statements claiming that heliocentricity was a fact rather than a hypothesis were removed and the book approved for use by 1620.

Our next offender is another respected Renaissance historian, Andrew Pettegree, in his The Book in the Renaissance[5].

Nit Picking002

Once again this is a book that in general I find excellent and highly stimulating but like Brotton he disappoints when dealing with the history of science. Like Brotton he starts with Copernicus and De revolutionibus, he tells us:

In 1539 a young mathematician, Georg Joachim Rheticus, embarked on a journey of momentous consequence for the history of science. Rheticus is not a name well known even to scholars. At this point in his life he had little to distinguish him from other graduates at Wittenberg University apart from a family scandal: his father, a medical doctor, had been convicted of embezzlement and beheaded. In 1538 Rheticus left Wittenberg and settled in Nuremberg. Here he fell in with Johann Schoener, the city’s most distinguished astronomer: the following year he set off alone for Frauenberg, a small cathedral city on the Baltic coast beyond Danzig.

The purpose of this journey was to visit the renowned astronomer, Nicolas Copernicus. Although Copernicus had travelled in Europe earlier in his life, from 1510 he was permanently settled in his Polish-Prussian homeland, relatively remote from the major centres of European Scholarship. To ingratiate himself with the older man Rheticus had been provided with three valuable scientific volumes for Copernicus’s library. This was a gift with a purpose. The texts were the work of a Nuremberg printer, Johannes Petreius, who wanted Rheticus to persuade Copernicus to let him publish the master-work it was widely believed he would soon have ready for the press. The gift of the three texts was to demonstrate that only Germany’s greatest centre of scientific publishing could do justice to Copernicus’s work: and to help Rheticus prise the precious manuscript from the old man’s hands.

Copernicus kept Rheticus guessing. He seems to have enjoyed the younger man’s company, and it was 1541 before Rheticus could set off back to Wittenberg, clutching the manuscript of what would be Copernicus’s major text. De revolutionibus (Of the Revolution of the Heavenly Spheres). The following year he journeyed on to Nuremberg, where Petreius was waiting to set it on his press: it took until 1543 before the text, complete with its famous woodcut diagrams of Copernicus’s heliocentric system was ready for sale[6].

The story that Pettegree tells here is a very well-known one in the history of science that has been repeated, in one form or another, in numerous publications, but he still manages to get a whole series of fundamental facts wrong. Firstly, I would claim that whilst maybe not known to the general public, the name Rheticus is well-known to scholars. I think being appointed professor for the lower mathematics (i.e. arithmetic and geometry) at the University of Wittenberg in 1536 did distinguish him from other graduates of that university. He didn’t leave Wittenberg in 1538 and settle in Nuremberg but went on an official sabbatical armed with a letter of introduction written by the Rector of the university Philipp Melanchthon. One of the scholars he went to visit on that sabbatical, mentioned in that letter of introduction, was Johannes Schöner, the professor of mathematics at the Egidien Oberschule in Nürnberg a position to which he had been appointed on Melanchthon’s recommendation. Rheticus visited Schöner almost certainly to study astrology, a subject dear to Melanchthon’s heart.

Copernicus lived in Warmia (Ermland in German) an autonomous self governing Prince Bishopric. Rheticus took not three but six books as a gift to Copernicus of which four had been printed and published by Petreius in Nürnberg. When Rheticus visited Copernicus he was largely unknown and to describe him as renowned is more than a bit of a stretch. His renown came posthumously following the publication of De revolutionibus. There were rumours of a hypothesis and possibly a book, rumours created by the circulating manuscript of the Commentariolus but to state that Petreius or anybody else for that matter outside of Warmia knew of a master-work that would soon be ready for the press is once again an exaggeration. Rheticus’ mission could better be described as look see if Copernicus has anything substantial that could be of interest to a printer publisher specialised in astrological/astronomical and mathematical texts.

Copernicus did not keep Rheticus guessing. Firstly Rheticus suffered a period of illness and then travelled to Königsberg, where he wrote a chorography of Prussia for Duke Albrecht in 1541. Copernicus was reluctant to present his hypothesis to the world because he knew that he could not fulfil the promise that he had given in the Commentariolus that he would prove his hypothesis. To calm his fears Rheticus wrote and published his Narratio Prima in 1540 in Danzig, with a second edition appearing in Basel in 1541. This presented a brief first account of the heliocentric system and its positive reception convinced Copernicus to entrust Rheticus with his manuscript.

All in all a more than somewhat different story to that present to us by Pettegree

Next up we have my current bedtime reading Michael Bravo’s North Pole: Nature and Culture[7], which I’m enjoying immensely.

Nit Picking003

Although the emphasis of the book is on the polar voyages and expeditions beginning in the modern period the book starts much earlier. The first chapter contrasts the views of the North Pole of the ancient Greek astronomers, who saw it as the downwards extension of the North celestial pole and the Inuit who live/lived in the Arctic. The second chapter deals with the representations of the North Pole made by the cartographers and globe makers of the Early Modern Period, a topic of great interest to me, as regular readers will know. It is here that Bravo displays a surprising lack of accurate research. He tells us:

Apian was fortunate to have studied in nearby Vienna, introducing him to the work of a circle of highly talented mathematicians in Nuremberg, Ingolstadt and Vienna who were working under the patronage of Maximilian I, Holy Roman Emperor (1459–1519)…[8]

This is indeed correct and is something that I have written about in several posts and about which Darin Hayton has written a whole book, his The Crown and the Cosmos: Astrology and the Politics of Maximilian I, which I reviewed here. Bravo then goes on to discuss the Werner-Stabius cordiform map projection, which is of course a polar projection centred on the North Pole. All well and good up till now. After an extensive discussion of the cordiform projection, its use and its impact Bravo goes on to say:

Introducing the perspective of viewing the Earth from above brought cosmography into line with the new developments in drawing, projection and perspective pioneered in Renaissance Europe. Albrecht Dürer (1471-1528), one of the most remarkable German artists, was the son of a prominent goldsmith in Nuremberg. Dürer’s precocious talent for drawing broadened into printmaking, writing and an extraordinary rich span of philosophical interests. His studies of perspective spanned much of his life and he brought back to northern Europe the principles of linear perspective he encountered while studying in Bologna. He later moved to Vienna to work with Stabius and Werner under the patronage of Maximilian I[my emphasis] Dürer and Stabius published the first polar star chart in 1515[9].


As a Dürer fan, it’s nice to see him getting a nod for more than his Rhinoceros and yes Maximilian was one of his patrons, but the sentence I have placed in italics manages to include two major errors in just sixteen words. Firstly if Dürer had moved to Vienna, he would have only met Stabius and not Werner. The two knew each other from their mutual time at the University of Ingolstadt in the early 1480s but whereas Werner moved first to Rome and then to Nürnberg on the completion of his studies, Stabius stayed in Ingolstadt eventually becoming professor of mathematics before moving to Vienna as court historian and mathematician on Conrad Celtis’ Collegium poetarum et mathematicorum. The two of them continued to work together not by being in the same city but through correspondence. Needless to say Dürer never left Nürnberg and never moved to Vienna, his various shared projects with Stabius were either conducted by letter or by Stabius journeying to Nürnberg. I should point out the Dürer-Stabius-Heinfogel star maps were not the first polar star charts but the first European printed polar star charts, there are earlier manuscript ones and also earlier printed Chinese ones.

All of the things that I have criticised above are facts that are comparatively easy to find and verify with a relatively small amount of research work, so there really is no excuse for getting them wrong. It would be bad enough if the authors were beginners, amateurs or wanna be historians. But in each case we have to do with a justifiably renowned historian and author, so there is really no excuse for this level of sloppiness.

[1] Jerry Brotton, The Renaissance: A Very Short Introduction, OUP, Oxford, 2006

[2]Jerry Brotten, A History of the World in Twelve Maps, Allen Lane, London, 2012

[3] Brotton p. 99

[4] Brotton p. 99

[5] Andrew Pettegree, The Book in the Renaissance, Yale University Press, New Haven & London, 2011

[6] Pettegree pp. 273–274

[7]Michael Bravo, North Pole: Nature and Culture, Reaktion Books, London, 2019

[8] Bravo p. 56

[9] Bravo p. 60


Filed under History of Astronomy, History of Cartography, History of science, Renaissance Science