Category Archives: History of Astronomy

Science contra Copernicus

One of the most persistent and pernicious myths in the history of astronomy is that Galileo, with his telescopic observations, proved the validity of the Copernican heliocentric hypothesis and thus all opposition to it from that point on was purely based on ignorance and blind religious prejudice. Strangely, this version of the story is particularly popular amongst gnu atheists. I say strangely because these are just the people who pride themselves on only believing the facts and basing all their judgements on the evidence. Even Galileo knew that the evidence produced by his telescopic observations only disproved some aspects of Aristotelian cosmology and full scale Ptolemaic astronomy but other Tychonic and semi-Tychonic geocentric models still fit the available facts. A well as this the evidence was still a long way from proving the existence of a heliocentric model and many physical aspects spoke strongly against a moving earth. Put another way, the scientific debate on geocentrism versus heliocentrism was still wide open with geocentrism still in the most favourable position.

Apart from the inconclusiveness of the telescopic observations and the problems of the physics of a moving earth there were other astronomical arguments against heliocentricity at the time that remain largely unknown today. Christopher M. Graney[1] has done the history of astronomy community a big service in uncovering those arguments and presenting them in his new book Setting Aside All Authority: Giovanni Battista Riccioli and the Science against Copernicus in the Age of Galileo[2].


We’ll start with the general summary, as I’ve already stated in an earlier post this is an excellent five star plus book and if you have any interest in this critical period of transition in the history of astronomy then it is quite simply an obligatory text that you must read. So if you follow my advice, what are you getting for your money?

In 1651 the Jesuit astronomer Giovanni Battista Riccioli published his Almagestum Novum or New Almagest , which contains a list of 126 arguments concerning the motion of the earth, i.e. the heliocentric hypothesis, 49 for and 77 against and it is this list that provides the intellectual scaffolding for Graney’s book. Interestingly in discussion on seventeenth-century astronomy Riccioli’s book, and its list, has largely been dismissed or ignored in the past. The prevailing attitudes in the past seem to have been either it’s a book by a Jesuit so it must be religious and thus uninteresting or, as was taught to me, it’s a historical account of pre-Galilean astronomy and thus uninteresting. In fact before Graney and his wife undertook the work this list had never even been translated into English. As to the first objections only a few of Riccioli’s arguments are based on religion and as Graney points out Riccioli does not consider them to be very important compared with the scientific arguments. As to the second argument Riccioli’s account is anything but historical but reflects the real debate over heliocentrism that was taking place in the middle of the seventeenth century.

The strongest scientific argument contra Copernicus, which occupies pride of place in Graney’s book, is the so-called star size argument, which in fact predates both Galileo and the telescope and was first posited by Tycho Brahe. Based on his determination of the visible diameter of a star, Tycho calculated that for the stars to be far enough away so as to display no visible parallax, as required by a Copernican model with a moving earth, then they must be in reality unimaginably gigantic. A single star would have the same diameter as Saturn’s orbit around the sun. These dimensions for the stars didn’t just appear to Tycho to be completely irrational and so unacceptable. In a Tychonic cosmos, however, with its much smaller dimensions the stars would have a much more rational size. Should anyone think that this argument was not taken seriously, much later in the seventeenth century Christiaan Huygens considered the star size problem to be Tycho’s principle argument against Copernicus.

Many, more modern, historians dismissed the star size problem through the mistaken belief that the telescope had solved the problem by showing that stars are mere points of light and Tycho’s determined star diameters were merely an illusion caused by atmospheric refractions. In fact the opposite was true, early telescopes as used by Galileo and Simon Marius, amongst others, showed the stars to have solid disc shaped bodies like the planets and thus confirming Tycho’s calculations. Marius used this fact to argue scientifically for a Tychonic cosmos whilst Galileo tried to dodge the issue. We now know that what those early telescopic astronomers saw was not the bodies of stars but Airy discs an optical artefact caused by diffraction and the narrow aperture of the telescope and so the whole star size argument is in fact bogus. However it was first Edmond Halley at the beginning of the eighteenth century who surmised that these observed discs were in fact not real.

Graney details the whole history of the star size argument from Tycho down to Huygens revealing some interesting aspect along the way. For example the early Copernicans answered Tycho’s objections not with scientific arguments but with religious ones, along the lines of that’s the way God planned it!

Although the star size argument was the strongest scientific argument contra Copernicus it was by no means the only one and Graney gives detailed coverage of the whole range offering arguments and counter arguments, as presented by the participants in the seventeenth-century debate. Of interest particular here is Riccioli’s anticipation of the so-called Coriolis effect, which he failed to detect experimental thus rejecting a moving earth. Far from being a decided issue since 1610 when Galileo published his Sidereus Nuncius heliocentricity remained a scientifically disputed hypothesis for most of the seventeenth century.

Graney’s book is excellently written and clear and easy to understand even for the non-physicists and astronomers. He explains clearly and simply the, sometimes complex, physical and mathematical arguments and it is clear from his writing style that he must be a very good college teacher. The book is well illustrated, has an extensive bibliography and a useful index.

As a bonus the book contains two appendixes. The first is a translation (together with the original Latin text) and technical discussion of Francesco Ingoli’s 1616 Essay to Galileo, a never published but highly important document in the on going discussion on heliocentricity; Ingoli a Catholic cleric argued in favour of the Tychonic system. The second appendix is a translation (together with the original Latin text) and technical discussion of Riccioli’s Reports Regarding His Experiments with Falling Bodies. These experiments are of historical interest as they demonstrate Riccioli’s abilities, as a physicist, as he delivered the first empirical confirmation of Galileo’s laws of fall.

Graney’s book is a first class addition to the literature on the history of astronomy in the seventeenth century and an absolute must read for anyone claiming serious interest in the topic. If you don’t believe me read what Peter Barker, Dennis Danielson and Owen Gingerich, all first class historians of Early Modern astronomy, have to say on the back cover of the book.


[1] Disclosure; Chris Graney is not only a colleague, but he and his wife, Christina, are also personal friends of mine. Beyond that, Chris has written, at my request, several guest blogs here at the Renaissance Mathematicus, all of which were based on his research for the book. Even more relevant I was, purely by accident I hasten to add, one of those responsible for sending Chris off on the historical trail that led to him writing this book; a fact that is acknowledged on page xiv of the introduction. All of this, of course, disqualifies me as an impartial reviewer of this book but I’m going to review it anyway. Anybody who knows me, knows that I don’t pull punches and when the subject is history of science I don’t do favours for friends. If I thought Chris’ book was not up to par I might refrain from reviewing it and explain to him privately why. If I thought the book was truly bad I would warn him privately and still write a negative review to keep people from wasting their time with it. However, thankfully, none of this is the case, so I could with a clear conscience write the positive review you are reading. If you don’t trust my impartiality, fair enough, read somebody else’s review.

[2] Christopher M. Graney, Setting Aside All Authority: Giovanni Battista Riccioli and the Science against Copernicus in the Age of Galileo, University of Notre Dame Press; Notre Dame Indiana, 2015


Filed under Book Reviews, History of Astronomy, Myths of Science

Reaching for the stars

I spent Friday evening and all day Saturday at a conference in the Albrecht Dürer House in Nürnberg. You might ask if I suddenly moved over to the art historians but this was a history of astronomy conference. Dürer wrote an important maths book, which was published in 1525 and which I’ve blogged about in the past. However this wasn’t his first excursion into the mathematical sciences, in 1515 he was involved in the production and publication of the first ever (in Europe, there are earlier Chinese woodblock star chart prints) printed star maps. The conference that I intended was to celebrate the five hundredth anniversary of this historical event.

Albrecht Dürer House Nürnberg Source: Wikimedia Commons

Albrecht Dürer House Nürnberg
Source: Wikimedia Commons

These star maps or charts are often erroneously referred to as Dürer’s star maps, although in fact Dürer was only one of three people responsible for their creation and was viewed as the junior partner. If you look at the bottom left hand corner of the southern hemisphere map there are three coats of arms.

Direr Southern Hemisphere Star Map Source: Wikimedia Commons

Dürer Southern Hemisphere Star Map
Source: Wikimedia Commons

Going from right to left, the first one consisting of a pair of open doors is Dürer’s; the family name being originally Türer, meaning porter, which comes from Türe the German for door. The second a sword flanked by two stars is Conrad Heinfogel’s a priest and astronomer and the third the imperial eagle surmounted by the poet’s laurel wreath is the coat of arms of Johannes Stabius mathematicus and Imperial Historian. The Latin text immediately above the three coats of arms states that Johannes Stabius commissioned the piece, Conrad Heinfogel positioned the stars and Albrecht Dürer circumscribed the images.

Johannes Stabius portrait by Albrecht Dürer

Johannes Stabius portrait by Albrecht Dürer

Johannes Stabius (real name Stöberer; before 1468–1522) was a graduate of Ingolstadt where he became professor of mathematics. He moved with Conrad Celtis to Vienna where he became part of the so-called 2nd Viennese School of Mathematics as well as being appointed Imperial Historian. He is most well known today for the Werner-Stabius cordiform map projection.

Oronce Finé's World Map using a cordiform projection Source: Wikimedia Commons

Oronce Finé’s World Map using a cordiform projection
Source: Wikimedia Commons

He had strong connections to Nürnberg and had previously worked with Dürer on the Triumphal Arch for Maximilian I, one of the largest ever woodblock print.

Maximilian's Triumphal Arch Source: Wikimedia Commons

Maximilian’s Triumphal Arch
Source: Wikimedia Commons

Also in 1515 Stabius and Dürer had produced a world map.

Dürer-Stabius World Map 1515 Source: Astronomie in Nürnberg

Dürer-Stabius World Map 1515
Source: Astronomie in Nürnberg

Conrad Heinfogel (?–1517) (from whom there are no known portraits) had been a pupil of Bernhard Walther (c.1430–1504), who was Regiomontanus’ partner in his astronomical activities in Nürnberg and who continued his work after Regiomontanus died; some of his observations of Mercury would be used by Copernicus in De revolutionibus. Walther had owned the Dürer House before Dürer and this was one of the reasons that Dürer bought it. Amongst his other astronomical activities Heinfogel was employed to position the stars on a set of manuscript star maps produced in Nürnberg in 1503. This earlier set of maps almost certainly served as one of the templates for the 1515 Dürer maps. A probable second source for the maps was a 1435 set of manuscript star maps of unknown provenance now found in Vienna. However the means of transmission of the information from Vienna to Nürnberg is not known.

In the top left hand corner of the southern hemisphere map is the coat of arms of the Archbishop of Salzburg, Cardinal Matthäus Lang and in the top right hand corner a dedication to him. Lang was a fervent supporter of the sciences and it was he, for example, who commissioned the first account of Magellan’s circumnavigation of the earth on which Johannes Schöner based his 1523 globe displaying the route taken. The bottom right hand corner is an acknowledgement of Maximilian I, patron to both Stabius and Dürer.

Dürer Northern Hemisphere Star Map Source: Wikimedia Commons

Dürer Northern Hemisphere Star Map
Source: Wikimedia Commons

The four corners of the northern hemisphere map contain portraits of astronomer/astrologers: Top left Aratus 4th century BCE author of the Pænomena an astronomical poem. Top right is Ptolemaeus. Bottom left is Manilius a 1st century CE Roman astrologer, whose astrological poem Astronomica Regiomontanus had published in Nürnberg in 1473. Bottom right is the 10th century CE Persian astronomer al-Sufi, author of a famous star catalogue.

The two star maps are bounded by the ecliptic and contain all of the 1022 stars from the Ptolemaic star catalogue with the Ptolemaic numbering. Dürer produced the images for the forty-eight Ptolemaic constellations. The maps set new standards for star maps in the Renaissance and, because printed and widely distributed, influenced many star maps and celestial globes in the following century. Hans Gaab has identified about sixty such objects most notably Peter Apian’s star map from 1535, a rather unsuccessful attempt to include both hemispheres onto one chart.

Peter Apian Star Map 1535 Source: Wikimedia Commons

Peter Apian Star Map 1535
Source: Wikimedia Commons

Following the publication of Tycho Brahe’s new and much more accurate star catalogue at the end of the century the Dürer maps ceased to be influential.

Happy conference goers returning from lunch break 19 September 2015

Happy conference goers returning from lunch break 19 September 2015

The conference on Saturday covered all the above in much greater detail and the Dürer house now has a semi-permanent exhibition detailing the history and pre-history of the star maps, including at the moment originals, which however will be replaced by facsimiles in the future. Well worth a visit if you are in Nürnberg. (Get in touch and I’ll do my history of astronomy tour of Nürnberg for you, which ends with the Dürer House!)

If you can read German and wish to know more Hans Gaab, who is a fount of wisdom on all things astronomical historical in Nürnberg, has written a book on the Dürer Star Maps, Die Sterne über Nürnberg: Albrecht Dürer und seine Himmelskarten von 1515 (Schriftenreihe der Nürnberger Astronomischen Gesellschaft) that was officially presented on Friday as part of the celebrations, highly recommended.

The Dürer Star Maps again in a hand coloured edition

Source: Ian Ridpath's Star Tales

Source: Ian Ridpath’s Star Tales

Source: Ian Ridpath's Star Tales

Source: Ian Ridpath’s Star Tales


Filed under History of Astronomy

Misusing Galileo to criticise the Galileo gambit

Yesterday The Guardian website had an article on climate change denialists entitled, Here’s what happens when you try to replicate climate contrarian papers[1].

The article is headed with this portrait of Galileo

Galileo demonstrating his astronomical theories. Climate contrarians have virtually nothing in common with Galileo. Photograph: Tarker/Tarker/Corbis

Galileo demonstrating his astronomical theories. Climate contrarians have virtually nothing in common with Galileo. Photograph: Tarker/Tarker/Corbis

And it opens with the following paragraph:

Those who reject the 97% expert consensus on human-caused global warming often evoke Galileo as an example of when the scientific minority overturned the majority view. In reality, climate contrarians have almost nothing in common with Galileo, whose conclusions were based on empirical scientific evidence, supported by many scientific contemporaries, and persecuted by the religious-political establishment. Nevertheless, there’s a slim chance that the 2–3% minority is correct and the 97% climate consensus is wrong.

Now it is true that climate change denialists, like denialists in many other areas of scientific consensus, commonly use what is now known as the Galileo Gambit. This involves claiming in some way that Galileo was persecuted for his theories, although he was proved right in the long run. Implying that the denialist will also be proved right in the long run and hailed as another Galileo. Bob Dylan provided the perfect answer to the Galileo Gambit in his song Bob Dylan’s 115th Dream way back in 1965.

I said, “You know they refused Jesus, too”

He said, “You’re not Him

I would not object to the author’s comments on the contrarians misuse of the name of Galileo if her his comment had stopped at, climate contrarians have almost nothing in common with Galileo, however she he goes on to spoil it with what follows.

Although Galileo’s views on heliocentrism, and that is what stands to discussion here, had their origins in empirical observations made with the telescope he unfortunately did not stop there and they were not supported by a consensus of his contemporaries by any means. In fact at the time of Galileo’s trial by the Catholic Church the majority of astronomers qualified to pass judgement on the subject almost certainly rejected heliocentricity, most of them on good scientific grounds.

In his Dialogo, the book that caused his downfall, Galileo knew very well that he did not have the necessary empirical facts to back up the heliocentric hypothesis and so he resorted to polemic and rhetoric and brought as his pièce de résistance, his theory of the tides, which was fatally flawed and contradicted by the empirical evidence even before it hit the printed page.

Although it became largely accepted by the experts by around 1670, the necessary empirical evidence to substantiate heliocentricity didn’t emerge until the eighteenth and in the case of stellar parallax the nineteenth centuries.

I have written about this historical misrepresentation of Galileo’s position on various occasions and I don’t intend to repeat myself in this post. However anybody who is interested can read some of my thoughts in the post collected under the heading, The Transition to Heliocentricity: The Rough Guides. I also strongly recommend Christopher M. Graney’s recently published Setting Aside All Authority: Giovanni Battista Riccioli and the Science against Copernicus in the Age of Galileo, my review of which should, hopefully, appear here in the not to distant future.

Addendum: Seb Falk has pointed out that Dana Nuccitelli is a he not a she and I have made the necessary corrections to the text. I apologise unreservedly to Mr Nuccitelli for this error.

[1] h/t to Seb Falk (@Seb_Falk) for drawing my attention to this latest misstatement of Galileo’s scientific situation.


Filed under History of Astronomy, Myths of Science

Made in Nürnberg

In the period from roughly 1550 and 1650 Nürnberg was the leading centre in Europe, and thus probably the world, for the manufacture of scientific instruments. It is historically interesting to look at how this town in the middle of Europe came to acquire this status and also to take a brief look at some of the more famous of the Nürnberger instrument makers from this ‘golden’ period.

Like many European towns and cities, Nürnberg, as an entity, began to emerge at the beginning of the High Middle Ages, probably around the year 1000 CE. Like many such settlements it was initially not much more than a fortified hill top at a crossroads. The first record of the name is 1050 CE as nuorenberc, which later evolved into Nuremberg, the name by which it is still known in English. This name is the subject of a rare German bad pun; the Germans don’t really go in for puns. According to folk etymology the name was originally ‘Nur einem Berg’, which translates as ‘just a hill’. The geographical position of Nürnberg played an important role in its development. If you take an outline map of Europe and draw a straight line from Kiel, in Northern Germany, to Northern Italy and a second one from Paris to Prague, the point where they cross is Nürnberg. This led to Nürnberg becoming a major European trading hub in the medieval period; importing wares from the Northern Italian trading cities and then distributing them throughout Europe.

Germany didn’t exist as a country in the Middle Ages but was a loose conglomerate of large and small states interconnected through a network of feudal obligations and vaguely held together in the so-called Holy Roman Empire, which as somebody once quipped was neither holy nor Roman nor an empire. Within this patchwork of large and small Germanic states Nürnberg was one of the so-called Free Imperial Cities, small independent city-states, which only owed feudal allegiance to the Holy Roman Emperor. From 1105 CE Nürnberg was ruled by a hereditary Burggraf, a title that translates as Lord of the castle. From 1192 till 1427 the Burggrafen of Nürnberg came from the Hohenzollern family, who would go on to play a significant role in German history. In 1427 the rich traders of Nürnberg, of whom more shortly, bought the Burggraf rights from the Hohenzollern and from then on until 1806, when Nürnberg became part of Bavaria, the city was ruled by the town council. Although dominated by the rich trader families the town council was surprisingly democratic with three groups of councillors being appointed/elected from the three tiers of citizenry at regular intervals. During the Renaissance Nürnberg, like one of its major trading partners Venice, called itself a republic.

The Holy Roman Emperor granted the city of Nürnberg special tax privileges, which combined with its favourable geographical position and the large Europe wide demand for the spices that came into Europe through the Northern Italian trading cities meant that the Nürnberg traders became very, very wealthy. This led to them looking for new opportunities to invest their surplus profits. The High Middle Ages saw a steeply rising demand for metals (gold, silver, copper, lead, iron) and with it an expansion of the metal ore mining industry. The major ore deposits, and thus the mines, were situated in the eastern part of Middle Europe, Eastern Germany, Hungary, Rumania, Austria etc. Realising that it was an expanding business with a future the Nürnberg traders began investing in the metal ore mines and soon controlled a large part of this industry. At first content just to sell the ore they soon realised that they could make more profit if they smelted the ore themselves and so built their own smelters and began selling refined metal. It did not take long before the artisans of Nürnberg began to work the metal themselves producing finished metal objects for sale. By the fifteenth century Nürnberg had become one of the major metal working centres of Europe producing quite literally everything that could be made from metal from pins and needles to suits of armour. A sign of this development is that the first mechanical wire drawing machine was developed in Nürnberg. The Nürnberg guilds were incredibly well organised with single families responsible for the production of one object or group of objects. When Karl V (Holly Roman Emperor 1519–1556) ordered 5000 suits of armour from Nürnberg, one group of families was responsible for the leg plates, another for the breast plates and so on. Highly organised piecework.

Nürnberg as depicted in the Nuremberg Chronicles 1493

Nürnberg as depicted in the Nuremberg Chronicles 1493

Of course many scientific instruments are made of metal, mostly brass, and so Nürnberg in its all inclusiveness became a major centre for the manufacture of all types of scientific instruments. In fact it became the leading European centre for this work and thus, most probably, the leading world centre in the fifteenth and sixteenth centuries. We have two important historical attestations of Nürnberg’s supremacy in this area. The philosopher Nicholas of Cusa (Cusanus) (1401–1464) was very interested in astronomy and he purchased a celestial globe and other astronomical instruments from Nürnberg and this can still be viewed in the Cusanus Museum in his birthplace Kues. In 1470 when Johannes Regiomontanus set out to reform and modernise astronomy he moved from Budapest to Nürnberg because, as he tells us in a letter, Nürnberg had a good communications network through which he could communicate with other astronomers and because the best astronomical instruments were manufactured in Nürnberg. The communications network was an essential element of any Renaissance trading city and Nürnberg’s was second only to that of Venice.

By 1500 Nürnberg was the second biggest German city with a population of around 40 000, half of which lived inside the city walls and the other half in the surrounding villages, which belonged to the city. It was one of the richest cities in the whole of Europe and enjoyed a high level of culture, investing both in representative architecture and the arts, with many of the leading German Renaissance artists fulfilling commissions for the rich Nürnberg traders, known locally as the Patrizier; most famously Albrecht Dürer. Interesting in our context, Dürer’s maths book contained the first printed instructions in German of how to design and construct sundials. The first half of the sixteenth century was the golden age of scientific instrument production in Nürnberg with many of the leading instrument makers selling their wares throughout Europe, where they can still be found in museums in many different countries. In what follows I shall give brief sketches of a couple of the more well known of these craftsmen.

Nürnberg was famous for it’s portable sundials with family dynasties producing high quality products over three, four or even five generations. At the beginning of the sixteenth century the most significant sundial maker was Erhard Etzlaub (ca. 1460–1532) who like many other Nürnberger instrument makers was as much as a scholar as an artisan. As a cartographer he produced the first map of the Nürnberg region. He followed this with the so-called Rome pilgrimage map displaying the routes to Rome for the Holy Year of 1500, which famously Copernicus also attended. This map plays an important role in the history of modern cartography because it’s the first map with a scale, enabling the pilgrim to plan his daily journeys.

Etzlaub's Rome Pilgrim Map Source: Wikimedia Commons

Etzlaub’s Rome Pilgrim Map
Source: Wikimedia Commons

Etzlaub also constructed a map on the cover of one of his compasses in 1511 that is drawn in a projection that comes close to the Mercator projection. Etzlaub was a member of the so-called Pirckheimer Circle. A group of like minded proponents of the mathematical sciences centred around Willbald Pirckheimer, soldier, politician humanist scholar and translator from Greek into Latin of Ptolemaeus’ Geographia; a translation that became a standard work.

Willibald Pirckheimer, porträtiert von Albrecht Dürer (1503) Source: Wikimedia Commons

Willibald Pirckheimer, porträtiert von Albrecht Dürer (1503)
Source: Wikimedia Commons

This group of mathematical scholars demonstrated their interest in the mathematical sciences and in the construction of complex instruments in the highly complex sundial that they painted on the side of the Lorenzkirche in 1502, which also displays the time according to the Great Nürnberger Clock:

Lorenzkirche Sundial Source: Astronomie in Nürnberg

Lorenzkirche Sundial
Source: Astronomie in Nürnberg

And the clock on the Frauenkirche constructed in 1506:

Frauenkirche Clock

Frauenkirche Clock

The gold and blue ball above the clock dial displays the phases of the moon and is still accurate today.

Another member of the Pirckheimer Circle was Johannes Schöner(1477–1547), addressee of Rheticus’ Naratio Prima, the first published account of Copernicus’ heliocentrism.

Johannes Schöner Source: Wikimedia Commons

Johannes Schöner
Source: Wikimedia Commons

Schöner was the first producer of serial production printed globes both terrestrial and celestial. He also wrote, printed and published pamphlets on the design and manufacture of various scientific instruments. Schöner was Europe’s leading globe maker whose globes set standards for globe making, which influenced the manufacture of globes down to the nineteenth century.

Schöner Celestial Globe 1535 Source: Science Museum London

Schöner Celestial Globe 1535
Source: Science Museum London

Also a member of the Pirckheimer Circle and a close friend of Schöner’s was Georg Hartman (1489–1564).

Georg Hartmann Source: Astronomie in Nürnberg

Georg Hartmann
Source: Astronomie in Nürnberg

Hartmann like Schöner was a globe maker although none of his globes have survived. He was also one of the leading sundial makers of his generation and his complex and beautiful dials can still be found in many museums.

Hartmann Bowl Sundial Source: Wikimedia Commons

Hartmann Bowl Sundial
Source: Wikimedia Commons

In the early sixteenth century Nürnberg was the main European centre for the production of astrolabes and here Hartmann played a leading role. As far as can be ascertained Hartmann was the first person to produce astrolabes in series.

Hartmann Astrolabe Yale Source: Wikimedia Commons

Hartmann Astrolabe Yale
Source: Wikimedia Commons

Previously all astrolabes were produced as single pieces, Hartmann, however, produced series of identical astrolabes, probably employing other craftsmen to produce the individual parts according to a pre-described plan and them assembling them in his workshop. As a young man Hartmann had spent several years living in Italy where he was friends with Copernicus’ brother Andreas. As a scholar Hartmann was the first to investigate magnetic inclination or dip. However his studies were never published and so the credit for this discovery went to the English mariner Robert Norman.

Handmade metal instruments were, of course, very expensive and could in reality only be purchased by the wealthy, who often bought them as ornaments of status symbols rather than to be used. To make scientific instruments available to those with less money both Schöner and Hartmann produced paper instruments. These consisted of the scales and tables, normally found engraved on the metal instruments, printed accurately on paper, which the user could then paste onto a wooden background and so construct a cheap but functioning instrument.

Paper and Wood Astrolabe Hartmann Source: MHS Oxford

Paper and Wood Astrolabe Hartmann
Source: MHS Oxford

A later instrument maker was Christian Heiden (1526–1576) who like Schöner was professor for mathematics on the Egidiengymnasium in Nürnberg, Germany’s first gymnasium (similar to a grammar school). He made a wide range of instruments but was especially well known for his elaborate and elegant sundials, as much works of art as scientific instruments these were much prized amongst the rich and powerful and could be found on many a German court.

Column Sundial by Christian Heyden Source: Museumslandschaft Hessen-Kassel

Column Sundial by Christian Heyden
Source: Museumslandschaft Hessen-Kassel

This is of course only a very, very small sample of the Nürnberger instrument makers, the history pages of the Astronomie in Nürnberg website, created and maintained by Dr Hans Gaab, lists 44 globe makers, 38 astronomical instrument makers and more than 100 sundial makers between the fifteenth and nineteenth centuries; with the greatest concentration in the sixteenth century. Nürnberg was known throughout Europe for the quality and the accuracy of its scientific instruments and examples of the Nürnberger handwork can be found in museums in many countries, even outside of Europe.


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

Sorry Caroline but Maria got there first!

Astronomer Caroline Herschel observed her first comet on 1 August 1786 an anniversary that was celebrated by various people on Twitter yesterday. Unfortunately many of them, including for example NASA History Office (@NASAhistory), claimed that on this date she became the 1st woman to discover a comet. This is quite simply not true.

Maria Margarethe Kirch (née Winkelmann), the wife of Gottfried Kirch the Astronomer Royal of Berlin, discovered the comet of 1702 (C/1702 H1) on 21 March 1702 that is forty-eight years before Caroline Herschel was born. Unfortunately the discovery was published by her husband and it was he who was incorrectly acknowledged as the discoverer. In 1710 Gottfried admitted the error and publically acknowledged Maria as the discoverer but she was never official credited with the discovery.

Both Maria Kirch and Caroline Herschel were excellent astronomers with much important work to their credit. However credit where credit is due, Caroline was not the first woman to discover a comet, Maria was.


Filed under History of Astronomy, Myths of Science

σῴζειν τὰ φαινόμενα, sozein ta phainomena

For all those, who like myself, can’t actually speak or read ancient Greek the title of this post is a phrase well known in the history of astronomy ‘saving the phenomena’, also sometimes rendered as ‘saving the appearances’. This post is in response to a request that I received from a reader asking me to explain what exactly this expressions means.

The phrase saving the phenomena was first introduced into the history of astronomy discourse by the late nineteenth-century and early twentieth-century French physicist and historian of science, Pierre Duhem. Duhem used the expression in the title of his work on physical theory Sauver les Phénomènes. Essai sur la Notion de Théorie Physique de Platon à Galilée, (1908), which was translated into English in 1969, as To Save the Phenomena, an Essay on the Idea of Physical Theory from Plato to Galileo. In this work Duhem argued that all mathematical astronomy from Plato up to Copernicus consisted of mathematical models designed to save the phenomena and were not considered to represent reality. The phenomena that needed to be saved were the so-called Platonic axioms, i.e. that the seven planets (Mercury, Venus, Moon, Sun, Mars, Jupiter and Saturn) move in circles at a constant speed. It is fairly obvious that the planets do not move in circles or at a constant speed thus posing a difficult problem for the mathematical astronomers, in order to save the phenomena they have to present a mathematical model, which can account for the apparent irregularity of planetary motions in the form of a more fundamental real regularity.

Duhem’s thesis suffers from several historical problems. He bases his argument on a quote from Simplicius’ On Aristotle, On the Heavens, which dates from the sixth century CE. According to Simplicius Plato challenged the astronomers to solve the following problem:

“…by hypothesizing what uniform and ordered motions is it possible to save the phenomena relating to planetary motions.”[1]

Simplicius goes on to say:

“In the true account the planets do not stop or retrogress nor is there any increase or decrease in their speeds, even if they appear to move in such ways … the heavenly motions are shown to be simple and circular and uniform and ordered from the evidence of their own substance.”

Simplicius attribution of the concept of saving the phenomena to Plato is made more than nine hundred years after Plato lived. In fact there is no mention in the work of Plato of the principle of uniform circular motion, the earliest known example being in Aristotle. The earliest example of the phrase ‘saving the phenomena’ occurs in Plutarch’s On the Face in the Orb of the Moon, from the first century CE and does not refer to planetary motions but to Aristarchus’ attempt to explain the revolution of the sphere of the fixed stars and the movement of the Sun through heliocentricity.

We find some support for the view of Simplicius in the introduction to astronomy of Geminus of Rhodes in the first century BCE, although he doesn’t use the explicit phrase to save or saving the phenomena, he writes:

“For the hypothesis, which underlies (hupokeitai) the whole of astronomy, is that the Sun, the Moon, and the five planets move circularly and at constant speed (isotachôs) in the direction opposite to that of the cosmos. The Pythagoreans, who first approached such investigations, hypothesized that the movements of the Sun, Moon, and the five wandering stars are circular and uniform … For this reason, they put forward the question: how would the phenomena be accounted for (apodotheiê) by means of uniform (homalôn) and circular motions.”

As we can see Geminus attributes the concept of uniform circular motion to the Pythagoreans and not Plato. It should be pointed out that neither Simplicius nor Geminus was a mathematical astronomer.

Duhem also claimed that the most significant of all Greek astronomers, Ptolemaeus, adhered to the principle of saving the phenomena in his Syntaxis Mathematiké, the only substantial work of Greek mathematical astronomy to survive. However a careful reading of Ptolemaeus clearly shows that he regarded his models as representing reality and not just as saving the phenomena.

The most famous case of saving the phenomena can be found in Andreas Osiander’s Ad lectorum (to the reader) appended to the front of Copernicus’ De revolutionibus. In this infamous piece Osiander, who had seen the book through the press writes:

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 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. The present author has preformed both these duties excellently. For these hypotheses need not to be true nor even probable. On the contrary, if they provide a calculus consistent with the observations that is enough. [2]

As can be clearly seen here Osiander is suggesting to the reader that Copernicus’ work is just a mathematical hypothesis and thus need not be regarded as mirroring reality. It is clear from the rest of his text that Osiander is trying to defuse any objections, religious or otherwise, that Copernicus’ heliocentricity might provoke. Of course his claims stand in contradiction to Copernicus’ text where it is obvious that Copernicus believes his system to reflect reality. Because Osiander’s Ad lectorum was published anonymously, it was assumed by many people that it was written by Copernicus himself a confusion that was only cleared up at the beginning of the seventeenth century.

It is not clear whether Osiander was appealing to a two thousand year old tradition of saving the phenomena, as Duhem would have us believe, or whether he, and possibly Petreius the publisher, had devised a strategy to avoid censure of the book and Copernicus’ radical idea.

Although many people continue to quote it as a historical fact it is highly doubtful that Duhem’s thesis of the saving of the phenomena ruling mathematical astronomy for the two thousand years from Plato to Galileo is true and it is fairly certain that most if not all mathematical astronomers, like Ptolemaeus, believed the models that they devised to be true representations of reality.


[1] This and all other quote from the Greek are taken from Mark Schiefsky, “To save the phenomena” and curve fitting” (pdf)

[2] On The Revolutions, translation and commentary by Edward Rosen, The Johns Hopkins University Press, Baltimore and London, pb., 1992, p. XX


Filed under History of Astronomy

For those who haven’t been paying attention

Galileo Galilei was found guilty and sentenced by the Inquisition on 22 June 1633; as usual this anniversary has produced a flurry of activity on the Internet much of it unfortunately ill informed. This is just a very brief note for all those who haven’t being paying attention.

The crime of which Galileo was found guilty was “vehement suspicion of heresy” and not heresy. This might appear to some to be splitting hairs but within the theological jurisdiction of the Catholic Church the difference is a highly significant one. Had the Inquisition found him guilty of heresy then a death sentence would have followed almost automatically. As they only found him guilty of the lesser charge “vehement suspicion of heresy” it was possible for him to be sentenced to life in prison commuted the next day to house arrest.

And please Richard Coles, and anybody else stupid enough to quote it, the claim that he said Eppur si muove (and yet it moves) upon being sentenced is almost certainty a myth.


Filed under History of Astronomy, Myths of Science