Category Archives: History of science

The Astrolabe – an object of desire

Without doubt the astrolabes is one of the most fascinating of all historical astronomical instruments.

Astrolabe Renners Arsenius 1569 Source: Wikimedia Commons

Astrolabe Renners Arsenius 1569
Source: Wikimedia Commons

To begin with it is not simply one object, it is many objects in one:

 

  • An astronomical measuring device
  • A timepiece
  • An analogue computer
  • A two dimensional representation of the three dimensional celestial sphere
  • A work of art and a status symbol

 

This Medieval-Renaissance Swiss Army penknife of an astronomical instrument had according to one medieval Islamic commentator, al-Sufi writing in the tenth century, more than one thousand different functions. Even Chaucer in what is considered to be the first English language description of the astrolabe and its function, a pamphlet written for a child, describes at least forty different functions.

The astrolabe was according to legend invented by Hipparchus of Nicaea, the second century BCE Greek astronomer but there is no direct evidence that he did so. The oldest surviving description of the planisphere, that two-dimensional representation of the three-dimensional celestial sphere, comes from Ptolemaeus in the second century CE.

Modern Planisphere Star Chart c. 1900 Source: Wikimedia Commons

Modern Planisphere Star Chart c. 1900
Source: Wikimedia Commons

Theon of Alexandria wrote a thesis on the astrolabe, in the fourth century CE, which did not survive and there are dubious second-hand reports that Hypatia, his daughter invented the instrument. The oldest surviving account of the astrolabe was written in the sixth century CE by John Philoponus. However it was first the Islamic astronomers who created the instrument, as it is known today, it is said for religious purposes, to determine the direction of Mecca and the time of prayer. The earliest surviving dated instrument is dated 315 AH, which is 927/28 CE.

The Earliest  Dated Astrolabe Source: See Link

The Earliest Dated Astrolabe
Source: See Link

It is from the Islamic Empire that knowledge of the instrument found its way into medieval Europe. Chaucer’s account of it is based on that of the eight-century CE Persian Jewish astrologer, Masha’allah ibn Atharī, one of whom claim to fame is writing the horoscope to determine the most auspicious date to found the city of Baghdad.

So-called Chaucer Astrolabe dated 1326, similar to the one Chaucer describes, British Museum Source: Wikimedia Commons

So-called Chaucer Astrolabe dated 1326, similar to the one Chaucer describes, British Museum
Source: Wikimedia Commons

However this brief post is not about the astrolabe as a scientific instrument in itself but rather the last point in my brief list above the astrolabe as a work of art and a status symbol. One of the reasons for people’s interest in astrolabes is the fact that they are simply beautiful to look at. This is not a cold, functional scientific instrument but an object to admire, to cherish and desire. A not uncommon reaction of people being introduced to astrolabes for the first time is, oh that is beautiful; I would love to own one of those. And so you can there are people who make replica astrolabes but buying one will set you back a very pretty penny.

That astrolabes are expensive is not, however, a modern phenomenon. Hand crafted brass, aesthetically beautiful, precision instruments, they were always very expensive and the principal market would always have been the rich, often the patrons of the instrument makers. The costs of astrolabes were probably even beyond the means of most of the astronomers who would have used them professionally and it is significant that most of the well know astrolabe makers were themselves significant practicing astronomers; according to the principle, if you need it and can’t afford it then make it yourself. Other astronomers would probably have relied on their employers/patrons to supply the readies. With these thoughts in mind it is worth considering the claim made by David King, one of the world’s greatest experts on the astrolabe, that the vast majority of the surviving astrolabes, made between the tenth nineteenth centuries – about nine hundred – were almost certainly never actually used as scientific instruments but were merely owned as status symbols. This claim is based on, amongst other things, the fact that they display none of the signs of the wear and tear, which one would expect from regular usage.

Does this mean that the procession of astrolabes was restricted to a rich elite and their employees? Yes and no. When European sailors began to slowly extend their journeys away from coastal waters into the deep sea, in the High Middle Ages they also began to determine latitude as an element of their navigation. For this purpose they needed an instrument like the astrolabe to measure the elevation of the sun or of chosen stars. The astrolabe was too complex and too expensive for this task and so the so-called mariners astrolabe was developed, a stripped down, simplified, cheaper and more robust version of the astrolabe. When and where the first mariner’s astrolabe was used in not known but probably not earlier than the thirteenth century CE. Although certainly not cheap, the mariner’s astrolabe was without doubt to be had for considerably less money than its nobler cousin.

36904l

Mariner’s Astrolabe Francisco de Goes 1608 Source: Istituto e Museo di Storia della Scienza, Firenze

Another development came with the advent of printing in the fifteenth century, the paper astrolabe. At first glance this statement might seem absurd, how could one possibly make a high precision scientific measuring instrument out of something, as flexible, unstable and weak as paper? The various parts of the astrolabe, the planisphere, the scales, the rete star-map, etc. are printed onto sheets of paper. These are then sold to the customer who cuts them out and pastes them onto wooden forms out of which he then constructs his astrolabe, a cheap but serviceable instrument. One well-known instrument maker who made and sold printed-paper astrolabes and other paper instruments was the Nürnberger mathematician and astronomer Georg Hartmann. The survival rate of such cheap instruments is naturally very low but we do actually have one of Hartmann’s wood and paper astrolabes.

Hartmann Paper Astrolabe Source: Oxford Museum of History of Science

Hartmann Paper Astrolabe
Source: Oxford Museum of History of Science

In this context it is interesting to note that, as far as can be determined, Hartmann was the first instrument maker to develop the serial production of astrolabes. Before Hartmann each astrolabe was an unicum, i.e. a one off instrument. Hartmann standardised the parts of his brass astrolabes and produced them, or had them produced, in batches, assembling the finished product out of these standardised parts. To what extent this might have reduced the cost of the finished article is not known but Hartmann was obviously a very successful astrolabe maker as nine of those nine hundred surviving astrolabes are from his workshop, probably more than from any other single manufacturer.

Hartmann Serial Production Astrolabe Source: Museum Boerhaave

Hartmann Serial Production Astrolabe
Source: Museum Boerhaave

 

If this post has awoken your own desire to admire the beauty of the astrolabe then the biggest online collection of Medieval and Renaissance scientific instruments in general and astrolabes in particular is the Epact website, a collaboration between the Museum of the History of Science in Oxford, the British Museum, the Museum of the History of Science in Florence and the Museum Boerhaave in Leiden.

This blog post was partially inspired by science writer Philip Ball with whom I had a brief exchange on Twitter a few days ago, which he initiated, on our mutual desire to possess a brass astrolabe.

 

 

 

 

4 Comments

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

DO IT!

DO IT! is the title of a book written by 1960s Yippie activist Jerry Rubin. In the 1970s when I worked in experimental theatre groups if somebody suggested doing something in a different way then the response was almost always, “Don’t talk about it, do it!” I get increasingly pissed off by people on Twitter or Facebook moaning and complaining about fairly trivial inaccuracies on Wikipedia. My inner response when I read such comments is, “Don’t talk about it, change it!” Recently Maria Popova of brainpickings posted the following on her tumblr, Explore:

The Wikipedia bio-panels for Marie Curie and Albert Einstein reveal the subtle ways in which our culture still perpetuates gender hierarchies in science. In addition to the considerably lengthier and more detailed panel for Einstein, note that Curie’s children are listed above her accolades, whereas the opposite order appears in the Einstein entry – all the more lamentable given that Curie is the recipient of two Nobel Prizes and Einstein of one.

How ironic given Einstein’s wonderful letter of assurance to a little girl who wanted to be a scientist but feared that her gender would hold her back. 

When I read this, announced in a tweet, my response was a slightly ruder version of “Don’t talk about it, change it!” Within minutes Kele Cable (@KeleCable) had, in response to my tweet, edited the Marie Curie bio-panel so that Curie’s children were now listed in the same place as Einstein’s. A couple of days I decided to take a closer look at the two bio-panels and assess Popova’s accusations.

Marie Curie c. 1920 Source Wikimedia Commons

Marie Curie c. 1920
Source Wikimedia Commons

The first difference that I discovered was that the title of Curie’s doctoral thesis was not listed as opposed to Einstein’s, which was. Five minutes on Google and two on Wikipedia and I had corrected this omission. Now I went into a detailed examination, as to why Einstein’s bio-panel was substantially longer than Curie’s. Was it implicit sexism as Popova was implying? The simple answer is no! Both bio-panels contain the same information but in various areas of their life that information was more extensive in Einstein’s life than in Curie’s. I will elucidate.

Albert Einstein during a lecture in Vienna in 1921 Source: Wikimedia Commons

Albert Einstein during a lecture in Vienna in 1921
Source: Wikimedia Commons

Under ‘Residences’ we have two for Curie and seven for Einstein. Albert moved around a bit more than Marie. Marie only had two ‘Citizenships’, Polish and French whereas Albert notched up six. Under ‘Fields’ both have two entries. Turning to ‘Institutions’ Marie managed five whereas Albert managed a grand total of twelve. Both had two alma maters. The doctoral details for both are equal although Marie has four doctoral students listed, whilst Albert has none. Under ‘Known’ for we again have a major difference, Marie is credited with radioactivity, Polonium and Radium, whereas the list for Albert has eleven different entries. Under ‘Influenced’ for Albert there are three names but none for Marie, which I feel is something that should be corrected by somebody who knows their way around nuclear chemistry, not my field. Both of them rack up seven entries under notable awards. Finally Marie had one spouse and two children, whereas Albert had two spouses and three children. In all of this I can’t for the life of me see any sexist bias.

Frankly I find Popova’s, all the more lamentable given that Curie is the recipient of two Nobel Prizes and Einstein of one, comment bizarre. Is the number of Nobel Prizes a scientist receives truly a measure of their significance? I personally think that Lise Meitner is at least as significant as Marie Curie, as a scientist, but, as is well known, she never won a Nobel Prize. Curie did indeed win two, one in physics and one in chemistry but they were both for two different aspects of the same research programme. Einstein only won one, for establishing one of the two great pillars of twentieth-century physics, the quantum theory. He also established the other great pillar, relativity theory, but famously didn’t win a Nobel for having done so. We really shouldn’t measure the significance of scientists’ roles in the evolution of their disciplines by the vagaries of the Nobel awards.

 

6 Comments

Filed under History of Chemistry, History of Physics, History of science, Ladies of Science

The Huygens Enigma

The seventeenth century produced a large number of excellent scientific researches and mathematicians in Europe, several of whom have been elevated to the status of giants of science or even gods of science by the writers of the popular history of science. Regular readers of this blog should be aware that I don’t believe in the gods of science, but even I am well aware that not all researches are equal and the contributions of some of them are much greater and more important than those of others, although the progress of science is dependent on the contributions of all the players in the science game. Keeping to the game analogy, one could describe them as playing in different leagues. One thing that has puzzled me for a number of years is what I regard as the Huygens enigma. There is no doubt in my mind whatsoever that the Dutch polymath Christiaan Huygens, who was born on the 14 April 1629, was a top premier league player but when those pop history of science writers list their gods they never include him, why not?

Christiaan Huygens by Caspar Netscher, Museum Hofwijck, Voorburg Source: Wikimedia Commons

Christiaan Huygens by Caspar Netscher, Museum Hofwijck, Voorburg
Source: Wikimedia Commons

Christiaan was the second son of Constantijn Huygens poet, composer, civil servant and diplomat and was thus born into the highest echelons of Dutch society. Sent to university to study law by his father Christiaan received a solid mathematical education from Frans van Schooten, one of the leading mathematicians in Europe and an expert on the new analytical mathematics of Descartes and Fermat. Already as a student Christiaan had contacts to top European intellectuals, including corresponding with Marine Mersenne, who confirmed his mathematical talent to his father. Later in his student life he also studied under the English mathematician John Pell.

Already at the age of twenty-five Christiaan dedicated himself to the scientific life, the family wealth sparing him the problem of having to earn a living. Whilst still a student he established himself as a respected mathematician with an international reputation and would later serve as one of Leibniz’s mathematics teachers. In his first publication at the age of twenty-two Huygens made an important contribution to the then relatively new discipline of probability. In physics Huygens originated what would become Newton’s second law of motion and in a century that saw the development of the concept of force it was Huygens’ work on centripetal force that led Christopher Wren and Isaac Newton to the derivation of the inverse square law of gravity. In fact in Book I of Principia, where Newton develops the physics that he goes on to use for his planetary theory in Book III, he only refers to centripetal force and never to the force of gravity. Huygens contribution to the Newtonian revolution in physics and astronomy was substantial and essential.

In astronomy Christiaan with his brother Constantijn ground their own lenses and constructed their own telescopes. He developed one of the early multiple lens eyepieces that improved astronomical observation immensely and which is still known as a Huygens eyepiece. He established his own reputation as an observational astronomer by discovering Titan the largest moon of Saturn. He also demonstrated that all the peculiar observations made over the years of Saturn since Galileo’s first observations in 1610 could be explained by assuming that Saturn had a system of rings, their appearance varying depending on where Saturn and the Earth were in their respective solar orbits at the time of observations. This discovery was made by theoretical analysis and not, as is often wrongly claimed, because he had a more powerful telescope.

In optics Huygens was, along with Robert Hooke, the co-creator of a wave theory of light, which he used to explain the phenomenon of double refraction in calcite crystals. Unfortunately Newton’s corpuscular theory of light initially won out over Huygens’ wave theory until Young and others confirmed Huygens’ theory in the nineteenth century.

Many people know Huygens best for his contributions to the history of clocks. He developed the first accurate pendulum clocks and was again along with Robert Hooke, who accused him of plagiarism, the developer of the balance spring watch. There were attempts to use his pendulum clocks to determine longitude but they proved not to be reliable enough under open sea conditions.

Huygens’ last book published posthumously, Cosmotheoros, is a speculation about the possibility of alien life in the cosmos.

Huygens made important contributions to many fields of science during the second half of the seventeenth century of which the above is but a brief and inadequate sketch and is the intellectual equal of any other seventeenth century researcher with the possible exceptions of Newton and Kepler but does not enjoy the historical reputation that he so obviously deserve, so why?

I personally think it is because there exists no philosophical system or magnum opus associated with his contributions to the development of science. He work is scattered over a series of relatively low-key publications and he offers no grand philosophical concept to pull his work together. Galileo had his Dialogo and his Discorsi, Descartes his Cartesian philosophy, Newton his Principia and his Opticks. It seems to be regarded as one of the gods of science it is not enough to be a top class premier league player who makes vital contributions across a wide spectrum of disciplines, one also has to have a literary symbol or philosophical methodology attached to ones name to be elevated into the history of science Olympus.

P.S. If you like most English speakers think that his name is pronounced something like Hoi-gens then you are wrong, it being Dutch is nothing like that as you can hear in this splendid Youtube video!

9 Comments

Filed under History of Astronomy, History of Optics, History of Physics, History of science, Newton

A bit on the side

Galileo by Justus Sustermans/Wikipedia

Galileo by Justus Sustermans/Wikipedia

For those of my readers who don’t follow me on Twitter or Facebook I have indulged in my favourite pastime, slagging of Galileo Galilei, but this time in an opinion piece in the online science journal AEON. If you’ve already read my old Galileo post Extracting the stopper, this is just a shorter punchier version of the same. If not or if you want to read the updated sexy version then mosey on over to AEON and read Galileo’s reputation is more hyperbole than truth.

11 Comments

Filed under History of science, Myths of Science

The Reformation, Astrology, and Mathematics in Schools and Universities.

It is one of the ironies of the medieval universities that mathematics played almost no role in undergraduate education. It is ironical because the curriculum was nominally based on the seven liberal arts of which the mathematical sciences – arithmetic, geometry, music and astronomy – formed one half, the quadrivium. Although the quadrivium was officially a large part of the curriculum in reality the four mathematical disciplines were paid little attention and hardly taught at all. This only began to change in the fifteenth century with the rise of astro-medicine or iatromathematics, to give it its formal name. With the rise of this astrology-based medicine the humanist universities of Northern Italy and Kraków introduced chairs of mathematics to teach astrology to their students of medicine. This of course entailed first teaching mathematics and then astronomy in order to be able to do astrology and thus mathematics gained a first foothold in the European universities. Ingolstadt became the first German university to introduce a chair for mathematics, also for teaching astrology to medical students, in the 1470s. It became an important centre for seeding new chairs at other universities with its graduates. Stabius and Stiborius going from there to Vienna with Celtis, for example. However there was no systematic introduction of mathematics into the university curriculum as of yet, this would first come as a result of the Reformation and the educational reforms of Philip Melanchthon.

Melanchthon in 1526: engraving by Albrecht Dürer Translation of Latin caption: «Dürer was able to draw Philip’s face, but the learned hand could not paint his spirit». Source: Wikimedia Commons

Melanchthon in 1526: engraving by Albrecht Dürer Translation of Latin caption: «Dürer was able to draw Philip’s face, but the learned hand could not paint his spirit».
Source: Wikimedia Commons

Melanchthon was born Philip Schwartzerdt in Bretten near Karlsruhe on 16 February 1497. A great nephew of Johann Reuchlin a leading humanist scholar Philip changed his name to Melanchthon, a literal Greek translation of his German name, which means black earth, at Reuchlin’s suggestion. Melanchthon was a child prodigy who would grow up to be Germany’s greatest humanist scholar. He studied at Heidelberg University where he was denied his master degree in 1512 on account of his youth. He transferred to Tübingen where he came under the influence of Johannes Stöffler, one of those Ingolstadt graduates, a leading and highly influential mathematician/astrologer.

Johannes Stöffler Source Wikimedia Commons

Johannes Stöffler
Source Wikimedia Commons

The cosmograph Sebastian Münster was another of Stöffler’s famous pupils. Stöffler also has a great influence on several of the Nürnberger mathematician-astronomers, especial Johannes Schöner and Georg Hartmann. Under Stöffler’s influence Melanchthon became a passionate supporter of astrology.

On Reuchlin’s recommendation Melanchthon became professor of Greek at Luther’s University of Wittenberg at the age of twenty-one and thus a central figure in the Reformation. One of the major problems faced by the reformers was the fact that the education system was totally in the hands of the Catholic Church, which meant that they had to start from scratch and create their own school and university system; this task was taken on by Melanchthon, who became Luther’s Preceptor Germania, Germany’s Schoolmaster.

Because of his own personal passion for astrology Melanchthon introduced mathematics into the curriculum of all the Lutheran schools and universities. He invented a new type of school on a level between the old Church Latin schools and the universities that were devised to prepare their pupils for a university education. The very first of these was the Eigidien Oberschule in Nürnberg, which opened in 1526 with Johannes Schöner, as its first professor for mathematics.

Johannes_Schoner_Astronomer_01

These type of school created by Melanchthon would become the Gymnasium, still today the highest level secondary schools in the German education system.

In Wittenberg he appointed Johannes Volmar (1480-1536) professor for the higher mathematic, music and astronomy, and Jakob Milich (1501- 1559) professor for the lower mathematic, arithmetic and geometry, in 1525. Their most famous students were Erasmus Reinhold, who followed Volmar on the chair for higher mathematics when he died in 1536, and Georg Joachim Rheticus, who followed Milich on the chair for lower mathematics, in the same year when Milich became professor for medicine. Schöner, Reinhold and Rheticus were not the only mathematicians supported by Melanchthon, who played an important role in the dissemination of the heliocentric astronomy. Although following Melanchthon’s lead these Protestant mathematicians treated the heliocentric hypothesis in a purely instrumentalist manner, i.e. it is not true but is mathematically useful, they taught it in their university courses alongside the geocentric astronomy.

As a result of Melanchthon’s passion for astrology the Lutheran Protestant schools and universities of Europe all had departments for the study of mathematics headed by qualified professors. The Catholic schools and universities would have to wait until the end of the sixteenth century before Christoph Clavius did the same for them, although his motivation was not astrology. Sadly Anglican England lagged well behind the continent with Oxford first appointing professors for geometry and astronomy in the 1620s at the bequest of Henry Savile, who had had to go abroad to receive his own mathematical education. Cambridge only followed suit with the establishment of the Lucasian Chair in 1663, whose first occupant was Isaac Barrow followed by that other Isaac, Newton. In 1705 John Arbuthnot could still complain in an essay that there was not one single school in England that taught mathematics.

 

 

 

7 Comments

Filed under History of Astrology, History of Astronomy, History of Mathematics, History of science, Renaissance Science, University History

We’re British not European – Really?

Yesterday evening my #histsci soul sister Becky Higgitt tweeted the following:

Scientists for Britain on #bbcnews – we had Newton therefore we don’t want to be in Europe

As #histsci bloggers both Becky and I have been here before, Becky here on her H-Word blog at the Guardian and myself here on the Renaissance Mathematicus but as it’s something that can’t be said too often, I thought I would point out once again that science is collaborative and international and all attempts to claim it for some sort of lone genius, as is often the case with Newton, or to make nationalist claims on its behalf are a massive distortion of the history of science.

Becky’s tweet specifically mentions Britain’s science icon ‘numero uno’ Isaac Newton, so let’s take a look at his scientific achievements and the foundations on which they were built. As Newton, paraphrasing Bernard of Chartres, famously wrote in a letter to Robert Hooke: If I have seen further, it is by standing on the shoulders of giants. So who were these giants on whose shoulders Newton was perched? What follows is a bit shopping list I’m afraid and is by no means exhaustive, listing only the better known names of the predecessors in each area of study where Newton made a contribution.

Newton’s mathematics built on the work in algebra of Cardano and Bombelli, both Italians, and Stifel, a German, from the sixteenth century. Their work was built on the efforts of quite a large number of Islamic mathematicians who in turn owed a debt to the Indians and Babylonians. Moving on into the seventeenth century we have Viète, Fermat, Pascal and Descartes, all of them Frenchmen, as well as Oughtred, Wallis and Barrow representing the English and James Gregory the Scots. Italy is represented by Cavalieri. The Dutch are represented by Huygens and Van Schooten, whose expanded Latin edition of Descartes Géométrie was Newton’s chief source on the continental mathematics.

We see a similar pattern in Newton’s optics where the earliest influence is the 10/11th century Islamic scholar Ibn al-Haytham, although largely filtered through the work of others. In the seventeenth century we have Kepler and Schiener, both Germans, Descartes, the Frenchman, and Huygens, the Dutchman, pop up again along with Grimaldi, an Italian, Gassendi, another Frenchman, and James Gregory a Scot and last but by no means least Robert Hooke.

In astronomy we kick off in the fifteenth century with Peuerbach and Regiomontanus, an Austrian and a German, followed in the sixteenth century by Copernicus, another German. All three of course owed a large debt to numerous earlier Islamic astronomers. Building on Copernicus we have Tycho, a Dane, Kepler, a German, and of course Galileo, a Tuscan. France is once again represented by Descartes along with Ismael Boulliau. Also very significant are Cassini, an Italian turned Frenchman, and once again the ubiquitous Huygens. At last we can throw in a gaggle of Englishmen with Horrocks, Wren, Flamsteed, Halley and Hooke.

In physics we have the usual suspects with Kepler and Galileo to which we can add the two Dutchmen Stevin and Beeckman. Descartes and Pascal are back for the French and Borelli joins Galileo in representing Italy. Huygens once again plays a central role and one should not forget Hooke’s contributions on gravity.

As I said at the beginning these lists are by no means exhaustive but I think that they demonstrate very clearly that Newton’s achievements were very much a pan-European affair and thus cannot in anyway be used as an argument for an English or British science existing without massive European cooperation.

If we look at Newton’s scientific inheritance then things look rather bad for the British in the eighteenth century with the developments being made by a whole battalion of French, Swiss, German, Dutch and Italian researchers with not a Brit in sight anywhere. Things improved somewhat in the nineteenth century but even here the progress is truly international. If we take just one small example the dethroning of Newton’s corpuscular theory of light by the wave theory. Originated by Huygens and Hooke in the seventeenth century it was championed by Ampère, Fresnel, Poisson and Arago all of whom were French and by Young and Airy for the British in the nineteenth century.

I hope that yet again, with this brief example, I have made clear that science is a collaborative and cooperative enterprise that doesn’t acknowledge or respect national boundaries but wanders through the cultures where and when it pleases, changing nationalities and languages at will. Science is a universal human activity to which many different and varied cultures have made contributions and will continue to do so in the future. Science should have absolutely nothing to do with nationalism and chauvinism and politicians who try and harness it to their nationalist causes by corrupting its history are despicable.

 

11 Comments

Filed under History of science, Myths of Science, Newton

Christoph and the Calendar

The first substantive history of science post that I wrote on this blog was about the Jesuit mathematician and astronomer Christoph Clavius. I wrote this because at the time I was preparing a lecture on the life and work of Clavius to be held in his hometown Bamberg. Clavius is one of my local history of science celebrities and over the years I have become the local default Clavius expert and because of his involvement in the Gregorian calendar reform of 1572 I have also become the local default expert on that topic too.

Christoph Clavius

Christoph Clavius

All of this means that I have become very sensitive to incorrect statements about either Clavius or the Gregorian calendar reform and particularly sensitive to false statements about Clavius’ involvement in the latter. Some time back the Atlas Obscura website had a ‘time week’ featuring a series of blog post on the subject of time one of which, When The Pope Made 10 Days Disappear, was about the Gregorian calendar reform and contained the following claim:

The new lead astronomer on the project, Jesuit prodigy Christopher Clavius, considered this and other proposals for five years.

The brief statement contains three major inaccuracies, the most important of which, is that Clavius as not the lead astronomer, or lead anything else for that matter, on the project. This is a very widespread misconception and one to which I devote a far amount of time when I lecture on the subject, so I thought I would clear up the matter in a post. Before doing so I would point out that I have never come across any other reference to Clavius as a prodigy and there is absolutely nothing in his biography to suggest that he was one. That was the second major inaccuracy for those who are counting.

Before telling the correct story we need to look at the wider context as presented in the article before the quote I brought above we have the following:

A hundred years later, Pope Gregory XIII rolled up his sleeves and went for it in earnest. After a call for suggestions, he was brought a gigantic manuscript. This was the life’s work of physician Luigi Lilio, who argued for a “slow 10-day correction” to bring things back into alignment, and a new leap year system to keep them that way. This would have meant that years divisible by 100 but not by 400 (e.g. 1800, 1900, and 2100) didn’t get the extra day, thereby shrinking the difference between the solar calendar and the Earthly calendar down to a mere .00031 days, or 26 seconds.

Luigi LIlio Source: Wikimedia Commons

Luigi LIlio
Source: Wikimedia Commons

This is correct as far as it goes, although there were two Europe wide appeals for suggestions and we don’t actually know how many different suggestions were made as the relevant documents are missing from the Vatican archives. It should also be pointed out the Lilio was a physician/astronomer/astrologer and not just simply a physician. Whether or not his manuscript was gigantic is not known because it no longer exists. Having decided to consider Lilio’s proposal this was not simply passed on to Christoph Clavius, who was a largely unknown mathematicus at the time, which should be obvious to anybody who gives more than five minutes thought to the subject.

The problem with the calendar, as far as the Church was concerned, was that they were celebrating Easter the most important doctrinal festival in the Church calendar on the wrong date. This was not a problem that could be decided by a mere mathematicus, at a time when the social status of a mathematicus was about the level of a bricklayer, it was far too important for that. This problem required a high-ranking Church commission and one was duly set up. This commission did not consider the proposal for five years but for at least ten and possibly more, again we are not sure due to missing documents. It is more than likely that the membership of the commission changed over the period of its existence but because we don’t have the minutes of its meetings we can only speculate. What we do have is the signatures of the nine members of the commission who signed the final proposal that was presented to the Pope at the end of their deliberations. It is to these names that we will now turn our attention.

The names fall into three distinct groups of three of which the first consists of the high-ranking clerics who actually lead this very important enquiry into a fundamental change in Church doctrinal practice. The chairman of the committee was of course a cardinal,Guglielmo Sirleto (1514–1584) a distinguished linguist and from 1570 Vatican librarian.

Cardinal Guglielmo Sirleto Source: Wikimedia Commons

Cardinal Guglielmo Sirleto
Source: Wikimedia Commons

The vice chairman was Bishop Vincenzo Lauro (1523–1592) a Papal diplomat who was created cardinal in 1583. Next up was Ignatius Nemet Aloho Patriarch of Antioch and head of the Syriac Orthodox Church till his forced resignation in 1576. Ignatius was like his two Catholic colleagues highly knowledgeable of astronomy and was brought into the commission because of his knowledge of Arabic astronomy and also to try to make the reform acceptable to the Orthodox Churches. The last did not function as the Orthodox Churches initially rejected the reform only adopting it one after the other over the centuries with the exception of the Russian Eastern Orthodox Churches, whose church calendar is still the Julian one, which is why they celebrate Christmas on 6 7 January.

Our second triplet is a mixed bag. First up we have Leonardo Abela from Malta who functioned as Ignatius’ translator, he couldn’t speak Latin, and witnessed his signature on the commissions final report. He is followed by Seraphinus Olivarius an expert lawyer, whose role was to check that the reform did not conflict with any aspects of cannon law. The third member of this group was Pedro Chacón a Spanish mathematician and historian, whose role was to check that the reform was in line with the doctrines of the Church Fathers.

Our final triplet consists of what might be termed the scientific advisors. Heading this group is Antonio Lilio the brother of Luigi and like his brother a physician and astronomer. He was here to elucidate Luigi’s plan, as Luigi was already dead. The lead astronomer, to use the Atlas Obscura phase, was the Dominican monk Ignazio Danti (1536–1582) mathematician, astronomer, cosmographer, architect and instrument maker.

Ignazio Danti Source: Wikimedia Commons

Ignazio Danti
Source: Wikimedia Commons

In a distinguished career Danti was cosmographer to Cosimo I, Duke of Tuscany whilst professor of mathematics at the university of Pissa, professor of mathematics at the University of Bologna and finally pontifical mathematicus in Rome. For the Pope Danti painted the Gallery of Maps in the Cortile del Belvedere in the Vatican Palace and deigned and constructed the instruments in the Sundial Rome of the Gregorian Tower of Tower of Winds above the Gallery of Maps.

Map of Italy, Corsica and Sardinia - Gallery of Maps - Vatican Museums. Source: Wikimedia Commons

Map of Italy, Corsica and Sardinia – Gallery of Maps – Vatican Museums.
Source: Wikimedia Commons

After the calendar reform the Pope appointed him Bishop of Altari. Danti was one of the leading mathematical practitioners of the age, who was more than capable of supplying all the scientific expertise necessary for the reform, so what was the role of Christoph Clavius the last signer of the commission’s recommendation.

The simple answer to this question is that we don’t know; all we can do is speculate. When Clavius (1538–1612) first joined the commission he was, in comparison to Danti, a relative nobody so his appointment to this high level commission with its all-star cast is somewhat puzzling. Apart from his acknowledged mathematical skills it seems that his membership of the Jesuit Order and his status as a Rome insider are the most obvious reasons. Although relative young the Jesuit Order was already a powerful group within the Church and would have wanted one of theirs in such a an important commission. The same thought concerns Clavius’ status as a Rome insider. The Church was highly fractional and all of the other members of the commission came from power bases outside of Rome, whereas Clavius, although a German, as professor at the Collegio Romano counted as part of the Roman establishment, thus representing that establishment in the commission. It was probably a bit of all three reasons that led to Clavius’ appointment.

Having established that Clavius only had a fairly lowly status within the commission how did the very widespread myth come into being that he was somehow the calendar reform man? Quite simply after the event he did in fact become just that.

When Pope Gregory accepted the recommendations of the commission and issued the papal bull Inter gravissimas on 24 February 1582, ordering the introduction of the new calendar on 4 October of the same year,

Inter-grav

he granted Antonio Lilio an exclusive licence to write a book describing the details of the calendar reform and the modifications made to the process of calculating the date of Easter. The sales of the book, which were expected to be high, would then be the Lilio family’s reward for Luigi Lilio having created the mathematical basis of the reform. Unfortunately Antonio Lilio failed to deliver and after a few years the public demand for a written explanation of the reform had become such that the Pope commissioned Clavius, who had by now become a leading European astronomer and mathematician, to write the book instead. Clavius complied with the Pope’s wishes and wrote and published his Novi calendarii romani apologia, Rome 1588, which would become the first of a series of texts explaining and defending the calendar reform. The later was necessary because the reform was not only attacked on religious grounds by numerous Protestants, but also on mathematical and astronomical grounds by such leading mathematicians as François Viète and Michael Maestlin. Over the years Clavius wrote and published several thousand pages defending and explicating the Gregorian calendar reform and it is this work that has linked him inseparably with the calendar reform and not his activities in the commission.

9 Comments

Filed under History of Astronomy, History of Mathematics, History of science, Local Heroes, Renaissance Science