Category Archives: History of science

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

When contemplating the advent of the heliocentric hypothesis in the Early Modern Period, one of the first things that occurs to many people is the conflict between the emerging new astronomy and Christianity, in particular the Holy Roman Catholic Church. What took place in those early years was actually very different to what most people think occurred and to a large extent has over the years been blown up out of all proportions.

To a certain extent some sort of conflict was pre-programmed, as the Bible, which the majority in this period believed to be basically true , clearly presented a geocentric world, even to a small extent a flat earth given the Old Testament’s fundamentally Babylonian origins and the new astronomy was attempting to establish a heliocentric one. This situation called for a lot of diplomatic skill on the part of those proposing the new heliocentric cosmological system, a skill that some of those proponents, most notably Galileo Galilei failed to display.

Between the publication of Copernicus’ De revolutionibus, which was actively supported by several leading figures within the Catholic Church, and the sensational telescopic discoveries of 1610-1613 there was surprising little backlash against heliocentrism from any of the European Christian communities. I have dealt with this in detail in an earlier post and don’t intend to repeat myself here. The real problems first began in around 1615 and were provoked by Galileo Galilei and the Carmelite theologian Paolo Antonio Foscarini (c. 1565–1616).


Source: Wikimedia Commons

Again I have already dealt with this in great detail in two earlier posts, here and here, so I will only outline the real bone of contention now, which surprisingly has little to do with the science and a lot to do with who gets to interpret the Holy Word of God e.g. The Bible.

From its foundation the Catholic Church had claimed the exclusive right to interpret the Bible for its followers, i.e. all true Christians. With time that interpretation was anchored in the writings of the early church fathers, what they had written was holy gospel and to openly contradict it was considered to be heresy. The Church was not only a powerful religious institution but also a powerful political one and over the centuries the adage that power corrupts and absolute power corrupts absolutely certainly proved true within the Catholic Church. This led to several attempts to reform the Church and bring it back to the ‘true path’ as outlined in the gospels.

Before what we now know as The Reformation, notable attempts on varying levels were made by, amongst other, John Wycliffe (c. 1320s–1384) in England, Jan Hus (c. 1372–1415) in Bohemia and Desiderus Erasmus (1466–1536), although Erasmus’ reform efforts were very moderate when compared to the other two and those that came after. In the sixteenth century that which we call the Protestant Reformation broke out in several parts of Europe instigated by Martin Luther (1483–1546), Philipp Melanchthon (1497–1560), Thomas Müntzer (1489–1525), Huldrych Zwingli (1484–1531), Jean Calvin (1509–1564) and a host of other minor figure, such as Andreas Osiander (1496 or 1498–1552), who wrote the infamous Ad lectorum in De revolutionibus. The major characteristic of the Reformation was that those calling for reform demanded the right for each individual to be allowed to interpret The Bible for themselves, thus removing the Church’s monopoly on biblical interpretations. This was of course unacceptable for the Catholic Church, which in turn launched its Counter Reformation, with the Council of Trent (1545–1563), to try and stem the tide of dissent. This was the situation in 1615 just three years before the outbreak of the Thirty Years War, one of the bloodiest conflicts in the history of Europe triggered by just this religious dispute, when Galileo made the move that turned the Catholic Church against heliocentrism and began Galileo’s own downfall.

Before we examen what Galileo actually did to so annoy the Catholic Church, it pays to look at the historical context in which this all took place. Too often people try to judge what happened from a presentist point of view, thereby distorting the historical facts. As usual when I write on this subject I am not trying to apologise for the Catholic Church’s actions or to excuse them, merely to present them within the practices and beliefs at the beginning of the seventeenth century. Firstly, this was a historical period in which all social, cultural and political institutions were hierarchical and fairly rigidly structured. It was an age of absolutism in which most rulers, including or above all the Pope, had and exercised absolute power. Secondly, there was no such thing as freedom of speech or freedom of thought in either religious or secular society. Those at the top largely prescribed what could or could not be said or thought out loud. Anybody who pushed against those prescriptions could expect to be punished for having done so.


Galileo Portrait by Ottavio Leoni Source: Wikimedia Commons

In 1615 both Foscarini and Galileo tried to tell the Church how to reinterpret those passages in the Bible that presupposed a geocentric cosmos in order to make a heliocentric cosmos theologically acceptable. This was simply not on. In my comments I will restrict myself to the case of Galileo. Modern commentators think that what Galileo said in his Letter to Castelli and in the extended version, his Letter to Christina, is eminently sensible and applaud him for his theological analysis but in doing so they miss several important points. In the Renaissance intellectual hierarchy theologians were at the top and mathematici, and Galileo was a mere mathematicus, were very much at the bottom. In fact the social status of the mathematicus was so low that Galileo telling the theologians how to do their job was roughly equivalent to the weekly cleaning lady telling the owner of a luxury villa how to run his household. This was definitely a massive failure on Galileo’s part, one that he should have been well aware of. The very low social and intellectual status of mathematici was the reason why he insisted on being appointed court philosophicus and not just mathematicus to the Medicean court. Philosophers ranked just below theologians in the hierarchy. Also given the fact that the Reformation/Counter Reformation conflict was rapidly approaching its high point in the Thirty Years War, this was not the time to tell the Catholic Church how to interpret the Bible.

As formal complaints began to be made about his Letter to Castelli, Galileo realised that he had gone too far and claimed that the copies in circulation had been changed by his enemies to make him look bad and presented the Church with a modified version to show what “he had actually written.” I fact we now know that the unmodified version was his original letter.

The writings of Foscarini and Galileo on the subject now led the Church to formally examine the relationship between Catholic doctrine and the heliocentric hypothesis, for the first time, and the result was not good for Galileo and the heliocentric hypothesis. A commission of eleven theologians, known as Qualifiers, undertook this examination and came to the conclusion that the idea that the Sun is stationary is “foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture…”; while the Earth’s movement “receives the same judgement in philosophy and … in regard to theological truth it is at least erroneous in faith.” The first part is obvious the Bible states clearly that it is the Sun that moves and not the Earth and as the heliocentric hypothesis directly contradicts Holy Scripture it is formally heretical. The second part is more interesting because it that the hypothesis is philosophically, read scientifically, absurd and foolish. Although the language used here in the judgement is rather extreme it was a fact in 1615 that there existed no empirical proof for the heliocentric hypothesis, actually most of the then available empirical evidence supported a geocentric cosmos. If there had been empirical support for heliocentrism then the Church’s judgement might well have been different, as Roberto Bellarmino (1542–1621) wrote in his infamous letter to Foscarini:

Third, I say that, if there were a real proof that the Sun is in the centre of the universe, that the Earth is in the third sphere, and that the Sun does not go round the Earth but the Earth round the Sun, then we should have to proceed with great circumspection in explaining passages of Scripture which appear to teach the contrary, and we should rather have to say that we did not understand them than declare an opinion to be false which is proved to be true.


Roberto Bellarmino Source: Wikimedia Commons

In other words, if you provide proof of your hypothesis, then we will be prepared to reinterpret the Bible.

This was the point where Galileo, realising that he was potentially in serious trouble, first rushed to Rome to peddle his theory of the tides, which he appeared to believe delivered the necessary empirical proof for the heliocentric hypothesis.


Source: Wikimedia Commons

This theory had been developed together with Paolo Sarpi (1552–1623) in the 1590’s and basically claimed that the tides were caused by the movements of the Earth, in the same way that water sloshes around in a moving bowl. The theory has however a fatal empirical flaw; it only allows for one high tide in twenty-four hours whereas there are actually two. Galileo tried to deal with this discrepancy with a lot of hand waving but couldn’t really provide a suitable explanation. This was, however, irrelevant in 1615, as Galileo having through his actions poked the proverbial bear with a sharp stick, nobody was prepared to listen to his latest offerings and his efforts fell on deaf ears.

The inevitable happened, the Church formally banned heliocentricity in 1616, although it was never actually declared heretical, something that only the Pope could do and no Pope ever did, and books explicating the heliocentric hypothesis were placed on the Index of forbidden books. Interestingly Copernicus’ De revolutionibus was only placed on the Index until corrected and rather surprisingly this was carried out fairly quickly, the corrected version becoming available to Catholic scholars already by 1621. The Church had realised that this was an important book that should not be banned completely. The corrections consisted or removing or correcting the surprisingly few places in the text where the heliocentric hypothesis was stated as being scientifically true. This meant that Catholics were permitted to write about and discuss heliocentricity as a hypothesis but not to claim that it was empirically true.

Galileo who together with Foscarini had provoked this whole mess got off relatively lightly. At the Pope’s request he was personally informed by Cardinal Roberto Bellarmino that he could no longer hold or teach the heliocentric theory and given a document confirming this in writing. He was not punished in anyway and continued to be popular amongst leading figures in the Church including Maffeo Barberini, the future Pope Urban VIII.

Many modern commentators say why couldn’t the Church accept the eminently sensible suggestion made by Galileo and Foscarini and thus avoid the whole sorry mess. The answer is quite simple. If they had done so they would have surrendered their absolute right to interpret Holy Scripture, which, as pointed out above, lay at the centre of the Reformation/Counter Reformation conflict; a right that the Catholic Church has not surrendered up to the present day.





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

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

The first period of telescopic, astronomical discoveries came to an end in 1613, which was seventy years after the publication of Copernicus’ De revolutionibus. This makes it a good point to stop and take stock of the developments that had taken place since the appearance of that epoch defining magnum opus. First we need to remind ourselves of the situation that had existed before Copernicus heliocentric hypothesis entered the world and triggered a whole new cosmology and astronomy debate. The mainstream standpoint was an uneasy combination of Aristotelian cosmology and Ptolemaic astronomy. Uneasy because, as some saw it, the Ptolemaic deferent and epicycle model of planetary motion contradicted Aristotle’s homocentric principle, which led to a revival of homocentric astronomy. Others saw the principle of uniform circular motion contradicted by Ptolemaeus’ use of the equant point. In fact, we know that the removal of the equant point, for exactly this reason, was the starting point of Copernicus’ own reform efforts. Another minority view that was extensively discussed was a geocentric system with diurnal rotation, as originated in antiquity by Heraclides of Pontus, regarded by some as more rational or acceptable than that the sphere of the fixed stars rotated once in twenty-four hours. Also still up for debate was the Capellan system with Mercury and Venus orbiting the Sun in a geocentric system. Then came Copernicus and added a new radical alternative to the debate.

By 1613 most of the Aristotelian cosmology had been disposed of bit for bit. Aristotle’s sublunar meteorological comets had definitely become supralunar astronomical objects, although what exactly they were was still largely a mystery. As we shall see Galileo later embarrassed himself by maintaining a position on comets very close to that of Aristotle. The comets becoming supralunar had also disposed of Aristotle’s crystalline spheres, although Copernicus seems to have still believed in them. The telescopic discovery of the geographical features on the Moon and the spots on the Sun had put an end to Aristotle’s perfection of the celestial spheres. They together with the comets and the supernovas of 1573 and 1604, both of which had clearly been shown to be supralunar, also contradicted his immutability of the heavens. The discovery of the four largest moons of Jupiter ended the homocentric concept and the discovery of the phases of Venus, originating in a solar orbit, ruled a pure geocentric system but not a geo-heliocentric one. As a result of all these changes cosmology was up for grabs.

In astronomy the biggest single change was that nearly all astronomers, following Copernicus, now believed in the reality of their models and no longer viewed them as purely mathematical constructions designed to save the phenomena. This was a major shift as previously the discussion of the reality of the heavens was regarded as a discussion for philosophers and definitely not astronomers. So which models were up for discussion? Had in the intervening seventy years the debate simplified, reduced to a choice between two competing models, Ptolemaic geocentrism and Copernican heliocentrism, as Galileo would have us believe twenty years later? Actually no, if anything the situation had got considerably more confused with a whole raft full of astronomical models jostling for a place at the table. What were these competing models?

Given the telescopic observations of the phases of Venus and the assumption of similar phases for Mercury, a pure Ptolemaic geocentric model should have been abandoned but there was still a hard core that refused to simply give up this ancient model. Christoph Clavius (1538–1612) in the last edition of his Sphaera, the standard Jesuit textbook on astronomy, acknowledged problems with the geocentric model but urged his readers to find solutions to the problems within the model. As late as 1651 Giovanni Battista Riccioli (1598–1671), in the famous frontispiece to his Almagestum novum, shows Ptolemaeus lying defeated on the ground, whilst the heliocentric and geo-heliocentric systems are weighed against each other, but he is saying, I will rise again.


Frontispiece of Riccioli’s 1651 New Almagest. Source: Wikimedia Commons

Due to William Gilbert’s revival of the Heraclidian diurnal rotation, we now have two geocentric models, with and without diurnal rotation. The Copernican heliocentric system is, of course, still very much in the running but with much less support than one might expect after all the developments of the intervening seventy years.

Despite the phases of Venus all the various geo-heliocentric models are still in contention and because of the lack of empirical evidence for movement of the Earth these are actually more popular at this point in time than heliocentric ones. However, despite the lack of empirical evidence diurnal rotation enjoys a surprising level of popularity. We have a Capellan system, Venus and Mercury orbit the Sun, which orbits the Earth, both with and without diurnal rotation. Very much in consideration is the full Tychonic system; the five planets orbit the Sun, which together with the Moon orbits the Earth. Once again both with and without diurnal rotation. Riccioli favoured another variation with Venus, Mercury and Mars orbiting the Sun but with Jupiter and Saturn orbiting the Earth along with the Sun and Moon.

Perhaps the most interesting development was Kepler’s heliocentric system. Whilst Kepler regarded his system as Copernican, others regarded his elliptical system as a rival to not only to the geocentric and geo-heliocentric system but also to the Copernican heliocentric system with its deferent and epicycle orbital models. The most prominent example of this being Galileo, who promoted the Copernican system, whilst deliberately ignoring Kepler’s more advanced developments.

We can find solid evidence for this multiplicity of systems in various sources. The earliest in a card game devised by Johann Praetorius (1573–1616), professor for astronomy at the University of Altdorf near Nürnberg, which only exists in manuscript.


Source: Wikimedia Commons











Source: All playing card images Wikimedia Commons

Another much read source is the extraordinary Anatomy of Melancholy by the Oxford scholar Robert Burton (1577–1640). First published in 1621, it was republished five times over the next seventeen years, each edition being massively modified and expanded.


The Anatomy of Melancholy frontispiece 1638 ed. Source: Wikimedia Commons

In a section entitled Melancholy of the Air Burton discusses the various astronomical models, favouring the system of David Origanus (1558–1629), professor for Geek Greek and mathematics at the University of Frankfurt an der Oder, a Tychonic system with diurnal rotation.


Source: Wikimedia Commons

Burton, as well as being one of the most erudite scholars of the seventeenth century, was also a practicing astrologer, who is said to have hung himself in his Oxford chambers to fulfil his own prediction of his death.

Already mentioned above is Giovanni Battista Riccioli, whose Almagestum novum (1551) contains descriptions of a wide range of different systems.


Riccioli as portrayed in the 1742 Atlas Coelestis (plate 3) of Johann Gabriel Doppelmayer. Source: Wikimedia Commons

The book also contains a list of 126 arguments pro and contra heliocentricity, 49 for and 77 against, in which religios arguments play only a very minor role.

Another Jesuit was Athanasius Kircher (1602–1680), who sat at the centre of a world spanning astronomy correspondence network, receiving astronomical data from Jesuits all of the world, collating it and re-distributing it to astronomers throughout Europe.


Source: Wikimedia Commons

He described six different systems as late as 1656 in his Itinerarium extaticum, with a revised edition from 1671.


Diagrams of the different world systems, Ptolemaic, Platonic, Egyptian, Copernican, Tychonic and semi-Tychonic from Iter Exstaticum (1671 ed.) p. 37 Source:

Contrary to a widespread view the question of the correct astronomical system was still very much an open question throughout most of the seventeenth century, largely because there existed no conclusive empirical evidence available to settle the question.





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

The Royal Society really needs to work on its history of the telescope

One would think that the Royal Society being one of the eldest, but not the eldest as they like to claim, scientific societies in Europe when presenting themselves as purveyors of the history of science, would take the trouble to get their facts right. If, however, one thought this, one would be wrong. Last week on the Internet the Royal Society was pushing a slide show, under their own name, on Google Arts and Culture on the history of the telescope in astronomy that in terms of historical accuracy is less than one, as a historian of science, nay of the telescope, might hope or indeed wish for.

The slide show in question is titled, Silent Harmony: astronomy at the Royal Society: Discover how innovation in telescopes and other optical instruments changed the way we see the universe. Following the title slide we have another general blurb slide but things then get serious on the history level, we get told under the heading, The new astronomy:


Galileo Portrait by Ottavio Leoni Source: Wikimedia Commons

Galileo Galilei (1564-1642) was the first to explore the solar system using a telescope. His work directly built on famous predecessors such as Nicolaus Copernicus (1473-1543) and Johannes Kepler (1571-1630), who set out to model a heliocentric universe – one in which the sun is at the centre of the universe – and theorise the motion of planets. 

Sometimes I tire slightly of repeating myself but once more into the breach dear friends, once more. Galileo was not the first to explore the solar system using a telescope. That honour goes to a man in London, you know London home of the Royal Society, Thomas Harriot (1560–1621).


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

Also at the same time as Galileo was aiming his telescope at the heavens in Padua, Simon Marius (1573–1625) was doing the same in Ansbach in Franconia


Simon Marius Source: Wikimedia Commons

and Giovanni Paolo Lembo (1570–1618) and Odo van Maelcote (1572–1615) in Rome. Whilst Galileo was more than prepared to call himself a Copernican, he very strongly rejected or ignored the work of Johannes Kepler, so saying that his work directly built on that of Kepler is more than a simple distortion of history. To say that these three theorised the motion of planets is to say the least bizarre, all astronomical models whether heliocentric, geocentric or geo-heliocentric theorise the motion of planets that is a large part of what astronomy is. We are not finished with Signor Galileo:

Galileo’s Starry Messenger was the first published work to incorporate scientific observations made using a telescope.

The treatise contains descriptions of lunar landscapes, new stars in well-known constellations and the major satellites of Jupiter.

This is all correct, however because he was the first to publish people make the mistake of thinking he was the first or even the only one to make telescopic observations in 1609. Moving on, the next slide caption isn’t correct:

Galileo designed and built the most powerful telescope of his generation.

His own instrument, a thirty-power magnifier preserved at the Museo Galileo in Florence, served as model to other instrument-makers for many years.

I’m beginning to think that the Royal Society has got something against Thomas Harriot. Whilst Galileo did indeed build a thirty-power telescope it was not the most powerful telescope of his generation, Harriot built a fifty-power one. However, as in a Dutch telescope (convex objective/concave eyepiece) the field of vision diminishes with magnification the fifty-power telescope proved next to useless. Galileo’s own instrument did not serve as a model to other instrument-makers for many years that, is to put it mildly, total bullshit. Lots of people knew how to construct a simple Dutch telescope and did so without any reference to Galileo.

We skip a few slides and arrive at the most famous President of the Royal Society, Isaac Newton;


Portrait of Newton by Godfrey Kneller, 1689 Source: Wikimedia Commons

we get a picture of Newton’s reflecting telescope with the following caption:


Replica of Newton’s second reflecting telescope, which he presented to the Royal Society in 1672 Source: Wikimedia Commons

The Royal Society also owns a reflecting telescope made by Newton as a direct application of his theories on light and colour.

This statement is a best misleading and at worst simply wrong depending on how you interpret it. Newton’s theories on light and colour led him to the awareness that the coloured fringes visible on the images of the then normal refracting telescope were the result of chromatic aberration, i.e. the visible light being split up into the colour spectrum when passing through a spherical lenses. This discovery led him to developing a reflecting telescope because he believed falsely that creating an achromatic lens was impossible. It would be more than half a century before Chester Moore Hall invented the first achromatic lens. The principle of the reflecting telescope, which with a suitable mirror, does not suffer from chromatic aberration, had been known since antiquity and Newton was by no means the first to try and construct one. He was, however, the first to succeed in producing a functioning reflecting telescope. You can read an outline of the full history of the reflecting telescope here. Interestingly nobody succeeded in copying Newton’s achievements for the best part of fifty years, when John Hadley (1682–1784), another fellow of the Royal Society, who gets no mention in this slide show, finally succeeded in producing large scale functioning reflecting telescopes; Newton’s instrument was little more than a toy.

The instrument allowed him to make various observations conclusive with his theories on gravity.

This caption is just high-grade rubbish. Newton did not make any observations with this instrument that were in anyway connected with his theory of gravity, let alone conclusive with it.

There are, in the mean time, quite a few good books on the history of the telescope, I have most of them sitting on my book shelf and I’m sure some of them are in the Royal Society’s library, so why didn’t who ever put this slide show together consult them or simply ask an expert?









Filed under History of Astronomy, History of Optics, History of science, Myths of Science

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

The publication of Galileo’s Sidereus Nuncius was by no means the end of the spectacular and game changing telescopic astronomical discoveries during that first hot phase, which spanned 1610 to 1613. There were to be three further major discoveries, one of which led to a bitter priority dispute that would in the end play a role in Galileo’s downfall and another of which would sink Ptolemaeus’ geocentric model of the cosmos for ever.

The first new discovery post Sidereus Nuncius was the rather strange fact that Saturn appeared to have ears or as Galileo put it, it was three bodies “accompanied by two attendants who never leave his side.”


Galileo’s drawings of Saturn

What Galileo had in fact observed were the rings of Saturn, which however because of the relative positions of Saturn and the Earth were not discernable as rings but as strange semi-circular projections on either side of the planet. What exactly the strange protrusions visible on Saturn were would remain a mystery until Christiaan Huygens solved the problem much later in the century. The astronomers of the Collegio Romano claimed priority on the Saturn discovery. Whether they or Galileo saw the phenomenon first cannot really be determined but it demonstrates once again that Galileo was by no means the only one making these new telescopic discoveries. Saturn’s two “attendants” didn’t really play a role in the ongoing astronomy/cosmology debate but the next discovery did in a very major way.

Probably stimulated by a letter from his one time student Benedetto Castelli (1578–1643) Galileo turned his attention to Venus and its potential phases.


Benedetto Castelli Source: Wikimedia Commons

If Venus was indeed lit by the sun then in both Ptolemaeus’ geocentric system and in a heliocentric system it would, like the moon, display phases but these phases would differ according to whether Venus orbited the Earth in a geocentric system or the sun in either a heliocentric or a geo-heliocentric one. Galileo’s observations clearly showed that the phases of Venus were consistent with a solar orbit and not a terrestrial one.


The Phases of Venus in both systems

The pure Ptolemaic geocentric system was irredeemably sunk but not, and that must be strongly emphasised, a number of geo-heliocentric systems. As already mentioned earlier, because they never strayed far from the sun’s vicinity and in a geocentric system even shared the sun orbital period, Mercury and Venus had since antiquity been assumed, by some, to orbit the sun whereas the sun orbited the earth in what is known as the Capellan system; a system that was very popular in the Middle Ages and had been praised as such by Copernicus in his De revolutionibus. Phases of Venus indicating a solar orbit were, of course, also consistent with a full Tychonic system in which the planets, apart from the moon, orbited the sun, which in turn together with the moon orbited the earth, as well as several variant semi-Tychonic systems. It was assumed that Mercury also orbited the sun, although its phases were first observed by  Pierre Gassendi (1592–1655) in 1631. The heliocentric phases of Venus were also discovered independently by Thomas Harriot, who, as always, didn’t publish, by Simon Marius, whose discovery was published by Kepler, and by the Collegio Romano astronomers, who also didn’t published but announced their discovery in their correspondence.

The other major telescopic discovery was the presence of blemishes or spots on the surfaces of the sun, again something that contradicted Aristotle’s assumption of the perfection of the celestial bodies. This discovery led to one of Galileo’s biggest priority disputes. This whole sorry episode began with a communication from the Augsburger banker and science fan, Marcus Welser(1558–1614), who was also a close friend of the Jesuits.


Marcus Welser Source: Wikimedia Commons

This communication contained three letters on sunspots written by the Ingolstädter Jesuit Christoph Scheiner (1573 or 75–1650) under the pseudonym, Appeles.


Christoph Scheiner (artist unknown)

Welser wanted to hear Galileo’s opinion on Scheiner’s discovery. Galileo was deeply offended, the heavens were his territory and only he was allowed to make discoveries there! The dispute was carried on two levels, the first was the question of priority and the second was the question of how to interpret what had been observed. Although, during the whole dispute Galileo kept changing the date when he first observed sunspots, in order to establish his priority and to claim the discovery as his, viewed with hindsight the priority dispute was a bit of a joke. We now know that Thomas Harriot  had recorded observations of sunspot before either Galileo or Scheiner but because he never published his observations, they were blissfully unaware of his priority. Even stranger, Johannes Fabricius (1587–1616), the son of Kepler’s intellectual sparing partner David Fabricius, had brought home a telescope from university in Leiden, where Rudolph Snell (1546–1613) was already holding lectures on the telescope in 1610, and together with his father had not only been observing sunspots but had already published a pamphlet on his observation in Wittenberg in 1611, where he was now studying.


The second part of the dispute was by far and away the more important. Scheiner had initially interpreted the sunspots as shadows cast upon the surface of the sun by small satellites orbiting it. It is was possible that through this interpretation he wished to preserve the Aristotelian perfection of this celestial body. Galileo opposed this interpretation and was convinced, correctly as it turned out, that the sunspots were actually some sort of blemishes on the surface of the sun.

Galileo answered Scheiner’s letters with three of his own, in the process stepping up his observation of the sunspots, as well as gathering observational reports from other astronomers. He was able to show through the quality of his observations and through mathematical analysis that the sunspots must be on the surface of the sun and that the sun must be revolving about its axis. With time Scheiner came to accept Galileo’s conclusions. Scheiner published three more sunspot letters under the title Accuratior Disquisitio in 1612.


The Accademia dei Lincei, which had elected Galileo a member when he came to Rome to celebrate the Jesuit’s confirmation of his telescopic discoveries, published Scheiner’s original three letters together with Galileo’s three answering letters in a book titled, Istoria e Dimontrazioni, in 1613.


Having in his opinion won the priority dispute and proved that the sunspots were on the surface of the sun, Galileo basically gave up on his solar observations; Scheiner did not. Having built what was effectively the first Keplerian or astronomical telescope with two convex lenses, instead of one convex and one concave, as in the Dutch or Galilean telescope, giving a much wider field of vision and a much clearer and stronger image, Scheiner set out on a programme of solar astronomy.


Scheiner Observing the Sun

The astronomical telescope provided an inverted image but this was irrelevant as Scheiner was projecting the image onto paper in order to simplify the drawing on the sunspots and also to protect his eyes. A method also used by Fabricius and Galileo. He mounted his telescope on a special holder that allowed him to follow the sun in its journey across the heavens.


Scheiner’s Helioscope

The end of this programme was his Rosa Ursina sive Sol, published in 1626-30, which remained the most important book on solar astronomy until the nineteenth century.


Scheiner’s Sunspot Observations

Galileo’s and Scheiner’s priority dispute entails a strong sense of historical irony. Not only did Harriot begin observing sunspots earlier than both of them and Johannes Fabricius publish on the subject before either of them but Chinese and Korean astronomers had been recording naked-eye observations of sunspots since the first millennium BCE. There are also scattered observations of sunspots beginning with the ancient Greeks and down through the Middle Ages in Europe.


A drawing of a sunspot in the Chronicles of John of Worcester 1129 Source: Wikimedia Commons

Famously Kepler recorded observations of a large sunspot that he made in 1607 mistakenly believing that he was observing a transit of Mercury.

1613 marks the end of the first phase of astronomical telescopic discoveries, partially because the observers continued to use Dutch or Galilean telescopes instead of changing to the vastly superior Keplerian or astronomical telescopes, largely influenced by Galileo’s authority, he publicly rubbished astronomical telescopes, basically because he hadn’t started using them first; the transition to the better instruments would take a couple of decades to be completed.









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

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

It is not an exaggeration to say that the invention of telescope was a very major turning point in the general history of science and in particular the history of astronomy. Basic science is fundamentally empirical; people investigating the world make observations with their senses–taste, sight, touch, smell, hearing–then try to develop theories to describe and explain what has been observed and recorded. The telescope was the first ever instrument that was capable of expanding or strengthening one of those senses that of sight. The telescope made it possible to see things that had never been seen before.

The road to the telescope was a long one and one of the questions is why it wasn’t invented earlier. There are various legends or myths about devices to enable people to see things at a distance throughout antiquity and various lens shaped objects also from the distant past that might or might not have been lenses. Lenses in scientific literature in antiquity and the early middle ages were burning lenses used to focus sunlight to ignite fires. The first definite use of lenses to improve eyesight were the so-called reading stones, which emerged around 1000 CE, approximately hemispherical lenses, placed on documents to help those suffering from presbyopia, weakening of the ability of the eye to focus due to aging.


Source: Zeiss

Reading glasses utilising plano-convex lenses first appeared around 1290.


The earliest pictorial evidence for the use of eyeglasses is Tommaso da Modena’s 1352 portrait of the cardinal Hugh de Provence reading in a scriptorium Source: Wikimedia Commons

The current accepted theory of the discovery of simple lenses is that in the Middle Ages monks cutting gems to decorate reliquary discovered the simple magnifying properties of the gemstones they were grinding and polishing.


Reliquary Cross, French, c. 1180 Source: Wikimedia Commons

By the middle of the fifteenth century eye glasses utilising both convex and concave lenses were being manufactured and traded, so why did it take until 1608 before somebody successfully combined a concave lens and convex lens to create a simple so-called Dutch telescope?

There are in fact earlier in the sixteenth century in the writings of Girolamo Fracastoro (ca. 1476–1553) and Giambattista della Porta (1532–1615) descriptions of the magnifying properties of such lens combinations but these are now thought to refer to special eyeglasses rather than telescopes.

Della Porta Telescope Sketch

The early lenses were spherical lenses, which were hand ground and polished and as a result were fairly inaccurate in their form tending to deviate from their ideal spherical form the further out one goes from the centre.  These deformations caused distortions in the images formed and combining lenses increased the level of distortion making such combinations next to useless. It is now thought that the breakthrough came through the use of a mask to stop down the diameter of the eyepiece lens cutting out the light rays from the periphery, restricting the image to the centre of the lens and thus massively reducing the distortion. So who made this discovery? Who first successfully developed a working telescope?

This question has been hotly discussed and various claims just as hotly disputed since at least the middle of the seventeenth century. However, there now exists a general consensus amongst historian of optics.

[To see the current stand on the subject read the bog post that I wrote at this time last year, which I don’t intend to repeat here]

Popular accounts of the early use of the telescope in astronomy almost always credit Galileo Galilei, at the time a relatively unknown professor for mathematics in Padua, with first recognising the potential of the telescope for astronomy; this is a myth.

As can be seen from the quote from the French newsletter AMBASSADES DV ROY DE SIAM ENVOYE’ A L’ECELence du Prince Maurice, arriué à la Haye le 10. Septemb.1608., recording the visit of the ambassador of the King of Siam (Thailand), who was also present at the first demonstration of the telescope the potential of this new instrument, as a tool for astronomy was recognised from the very beginning:

even the stars which normally are not visible for us, because of the scanty proportion and feeble sight of our eyes, can be seen with this instrument.

In fact the English polymath Thomas Harriot (1560–1621) made the earliest known telescopic, astronomical observations but, as with everything else he did, he didn’t publish, so outside of a small group of friends and acquaintances his work remained largely unknown. Also definitely contemporaneous with, if not earlier than, Galileo the Franconian court mathematicus, Simon Marius (1573–1625), began making telescopic observations in late 1609. However, unlike Galileo, who as we will see published his observations and discoveries as soon as possible, Marius didn’t publish until 1614, which would eventually bring the accusation of having plagiarised Galileo.  At the Collegio Romano, the Jesuit University in Rome, Odo van Maelcote (1572–1615) and Giovanni Paolo Lembo (1570–1618) were also making telescopic observations within the same time frame. There were almost certainly others, who didn’t make their observations public.

Before we turn to the observations and discoveries that these early telescopic observers made, we need to look at a serious technical problem that tends to get ignored by popular accounts of those discovery, how does a telescope work? In 1608 when the telescope first saw the light of day there existed absolutely no scientific explanation of how it worked. The group of early inventors almost certainly discovered its magnifying effect by accident and the first people to improve it and turn it into a viable scientific instrument, again almost certainly, did so by trial and error. At this point the problem is not to find the optical theory needed to develop better telescopes systematically but to find the optical theory necessary to justify the result the telescope produced. Using any sort of instrument in science requires a scientific explanation of how those results are achieved and as already stated at the beginning no such theory existed. The man, who came to the rescue, was Johannes Kepler in the second of his major contributions to the story of heliocentric astronomy.

Already in 1604 in his Ad Vitellionem Paralipomena Astronomiae pars optica, Kepler had published the first explanation of how lenses focus light rays and how eyeglasses work to compensate for short and long sightedness so he already had a head start on explaining how the telescope functions.



Francesco Maurolico (1494–1575) had covered much of the same ground in his Theoremata de lumine et umbra earlier than Kepler but this work was only published posthumously in 1611, so the priority goes to Kepler.


In 1611 Kepler published his very quickly written Dioptrice, in which he covered the path of light rays through single lenses and then through lens combinations. In this extraordinary work he covers the Dutch or Galilean telescope, convex objective–concave eyepiece, the astronomical or Keplerian telescope, convex objective–convex eyepiece, the terrestrial telescope, convex objective–convex eyepiece–convex–field–lens to invert image, and finally for good measure the telephoto lens! Galileo’s response to this masterpiece in the history of geometrical optics was that it was unreadable!


Source: Wikimedia Commons

In the next section we will turn to the discoveries that the various early telescopic astronomical observers made and the roles that those various discoveries played in the debates on, which was the correct astronomical model of the cosmos. A much more complicated affair than it is often presented.







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

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

Tycho and Kepler was one of the most important partnerships in the history of Early Modern science and a good counter example to those who mistakenly believe in the lone genius myth. Tycho the observational astronomer with an obsession for accuracy, who produced an unequalled volume of raw data


Tycho Brahe Source: Wikimedia Commons

and Kepler the theoretical astronomer with an equal obsession for accuracy, who would come to turn that data into a completely new heliocentric model of the cosmos.


Johannes Kepler Source: Wikimedia Commons

Superficially a marriage made in heaven but when the two men first met in Prague their future cooperation almost ended before it even started. Arriving in February 1600 at Tycho’s new home in Benátky Castle Kepler was initially welcomed as a guest and observer.


Benátky Castle Source: Wikimedia Commons

He was impressed by Tycho’s setup and his data collection to which he hoped to gain access to fine tune his Platonic solids model of the cosmos. Tycho was impressed by the young theoretician but, suspicious of possible plagiarism, was not prepared to make his data freely available. Kepler was of course desperate for paid employment and after two months entered negotiations with Tycho over some sort of fixed employment. The young, working class, German mathematician took umbrage at the arrogant attitude of the Danish aristocrat and in a strop broke off the talks, departing for Prague. Interestingly Tycho, needing fresh workers, proved himself surprisingly conciliatory and through the diplomatic efforts of the Bohemian physician Jan Jesenius (1566–1621) Kepler was persuaded to return to Benátky, where conditions of employment for him were eventually arranged.


Jan Jesenius

Kepler, who had left his family in Graz, now returned there and after a failed attempt to obtain employment from Archduke Ferdinand in August 1600 he finally set off for Prague with household and family. Initially he was employed directly by Tycho his first task being to write an account of the plagiarism dispute between Tycho and Ursus, probably as a punishment for having supplied Ursus with munitions in that dispute, and naturally he was expected to find in Tycho’s favour. This work, which turned out to be very impressive, was never published in Tycho’s or Kepler’s lifetimes and much more significant was the first real astronomical work that Tycho assigned to him.

When Kepler had first arrived in Benátky, Christen Longomontanus (1562–1647), who had returned to the fold having initially left Tycho’s circus when he quit Denmark, was working on the raw data for the orbit of Mars.


Christen Longomontanus

Tycho now removed him from this work, assigning him instead to the Moon’s orbit, and gave the task instead to Kepler under Longomontanus’ supervision. This turned out to be one of the most fateful decisions in the entire history of astronomy. Kepler initially thought that he could knock off this task in a couple of weeks but in fact it took him six years to complete but as well as the mathematical difficulties involved there were extenuating circumstances. Before turning to the results of what Kepler called his war with Mars, a play upon the fact that Mars was the Roman god of war, we need to take a look at some of those circumstances.

Tycho’s financial resources were stretched so he negotiated with Rudolf, the Emperor, for Kepler to be appointed directly to the court in order to produce a new set of planetary tables, using Tycho’s data, to replace the existing Prutenic Tables of Erasmus Reinhold and to be named, of course, after the Emperor. What seemed like a step up for Kepler proved to be very problematic, as Rudolf, always strapped for cash, was very bad at paying his staff.


Rudolf II Portrait by Martino Rota Source: Wikimedia Commons

The next major event was the death of Tycho on 24 October1601 barely a year after Kepler had started working with him. For Kepler this was both good and bad. Already appointed to produce planetary tables for Rudolph, he now inherited Tycho’s title as Imperial Mathematicus, as the obvious candidate Longomontanus had left Benátky and Tycho’s service the previous year. This was truly a major step up but with the same caveat that Rudolf was extremely bad at paying salaries. Kepler was, of course, now in physical possession of all of Tycho’s data but unfortunately not in legal possession. Although he had been Imperial Mathematicus, Tycho’s data did not belong to Rudolf but was his own private property and was on his death inherited by his family. Kepler was faced with the problem of negotiating with Tycho’s son in law Frans Gansneb genaamd Tengnagel van de Camp over the use of the data. Frans Tengnagel initially claimed that he would work with the data but he was a diplomat and not an astronomer or mathematician and in the end a compromise was reached in that Kepler could use the data but that Fans Tengnagel would be named as co-author in any resulting publications. In fact, in the end Frans Tengnagel’s only contribution was a preface to the Astronomia nova.


Frans Gansneb genaamd Tengnagel van de Camp

Even though he now possessed the desired data Kepler did not sit down solely to finish calculating the orbit of Mars. In 1604 he published his Astronomia Pars Optica, the most important work in optics since the Middle Ages, which laid the foundations of the modern science of optics.


Astronomiae Pars Optica

It included the first explanations of how lenses work to correct short and long sight and above all the first-ever correct explanation of how the image is formed in the eye. This work would, as will see, proved extremely important following the invention of the telescope at the end of the decade. Also in 1604 a supernova appeared in the skies and Kepler systematically observed it, confirmed it was definitively supralunar (i.e. above the moon’s orbit) and wrote up and published his findings, De Stella nova in pede Serpentarii, in Prague in 1606. This of course confirmed what had already been demonstrated in the 1570s that the heavens were not incorruptible, driving another nail into the coffin of Aristotelian cosmology.


Stella nova in pede Serpentarii title page

During this period Kepler also finished his determination of the orbit of Mars, in the course of which he changed the course of astronomy forever. Published in 1609 the Astronomia Nova ΑΙΤΙΟΛΟΓΗΤΟΣ seu physica coelestis, tradita commentariis de motibus stellae Martis ex observationibus G.V. Tychonis Brahe, to give it its full title, is without any doubt whatsoever one of the most important books in the whole history of astronomy, although it was not recognised as such until long after it appeared.


Astronomia Nova title page Source: Wikimedia Commons

Unique amongst major scientific publications the book appears to outline in great detail the path that the author took in his determination of the Planet’s orbit, including all the false paths he followed, the errors that he made and even his calculating mistakes. Normally scientists leave all of this out of their published work presenting only the successful conclusions of their battles with the evidence and data. So why did Kepler include all of his six years of strife in his finished product. The answer lies in the statement above, appears to outline. In fact the account presented is to some extent, to use an actual term, fake news. Kepler is deliberately misleading his readers but why?

Kepler was a convinced Copernicaner in a period where the majority of astronomers were either against heliocentricity, mostly with good scientific reasons, or at best sitting on the fence. Kepler was truly revolutionary in another sense, he believed firmly in a physical cause for the structure of the cosmos and the movement of the planets. This was something that he had already propagated in his Mysterium Cosmographicum and for which he had been strongly criticised by his teacher Mästlin. The vast majority of astronomers still believed they were creating mathematical models to save the phenomena, irrespective of the actually physical truth of those models. The true nature of the cosmos was a question to be answered by philosophers and not astronomers. Kepler structured the rhetoric of the Astronomia Nova to make it appear that his conclusions were inevitable; he had apparently no other choice, the evidence led him inescapably to a heliocentric system with a real physical cause. Of course, he couldn’t really prove this but he did his best to con his readers into thinking he could.

Kepler tested and refined his arguments in one of the most fascinating correspondences in the history of astronomy, which took place with the Frisian amateur astronomer David Fabricius (1564–1617) over a total of eight years; a correspondence that also makes a mockery of the lone genius myth. Fabricius was a Protestant pastor and a passionate amateur astronomer. He first emerged on the European astronomical scene when he took up contact with Jost Bürgi (1552–1632) in Kassel in 1592 to request his advice on constructing astronomical instruments. In 1596 having, as the first astronomer to do so, observed the variable star Mira he wrote a letter to Tycho Brahe in Hven describing his discovery. This was the start of an extensive correspondence between the two that lasted until Tycho’s death in 1601. In that year he visited Tycho in Prague, where he met Simon Marius (1573–1625) with whom he would also correspond but not Kepler who was in Austria on family business. The letters that Kepler and Fabricius exchanged were more in the nature of academic papers often running to forty or fifty pages.


Monument to David Fabricius & his son Johannes in the church yard in Osteel his parish Source: Wikimedia Commons

Fabricius was neither a geocentrist nor a heliocenrist but a solid supporter of Tycho’s geo-heliocentric compromise and so was an ideal sparing partner for Kepler. Kepler would outline his latest heliocentric theories and Fabricius would do his best to demolish them and his best was very good indeed. This meant that over the years of their correspondence Kepler could really develop and refine the complex arguments that he would then finally present in the Astronomia nova. Probably frustrated by his failure to convert Fabricius to his way of thinking, Kepler rather abruptly broke off the correspondence in 1609. Fabricius, who Kepler acknowledge as the best observational astronomer in Europe following Tycho’s demise, died tragically in 1617, beaten to death with a spade by a local farmer, who thought Fabricius had accused him of being a thief in a sermon.

Despite Kepler’s best efforts the Astronomia nova was largely a flop when first published. Those who read it largely rejected his argument for heliocentricity. The book however contains two of the most important discoveries in the history of astronomy, Kepler’s first two laws of planetary motion:

1) That planets orbit the Sun on elliptical paths with the Sun situated at one focus of the ellipse

2) That a line connecting the planet to the Sun sweeps out equal areas in equal periods of time.

Kepler actually developed the second law first using it as his primary tool to determine the actually orbit of Mars. The formulation of this law went through an evolution, which he elucidates in the book, before it reached its final form. The first law was in fact the capstone of his entire endeavour. He had known for sometime that the orbit was oval and had even at one point considered an elliptical form but then rejected it. When he finally proved that the orbit was actually an ellipse he knew that his battle was over and he had won.

Although, at the time, Kepler had temporarily lost the public battle in the larger war for the recognition that the cosmos, as it was then known, was indeed heliocentric the publication of the Astronomia nova represents one of the most important steps towards the final victory in that war. This would not remain Kepler’s only contribution to that war but before we look at his further efforts we need to turn to what was possibly the most important event in the history of Early Modern astronomy, the invention of the telescope.

[Attentive readers of this blog might have noticed that I have ‘plagiarised’ my own post on the Astronomia nova from December last year. I simply couldn’t be bothered to find new ways of expressing things that I had already expressed to my own satisfaction.]
















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

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

Along with Copernicus, Galileo and Newton, Kepler is one of the historical icons of the heliocentricity story. I personally think he is the most important figure of them all but in the public perception he is the least well known of the major figures and the least acknowledged. It is often said that we live in a Copernican cosmos or universe but in fact it would be much more accurate to state that we live in a Keplerian cosmos. So who was this man and what did he contribute to the evolution of the heliocentric hypothesis and its acceptance?

Johannes Kepler (1571–1633) was born in the small town of Weil der Stadt, a Free Imperial City within the Duchy of Württemberg, the son of Heinrich Kepler, an innkeeper and sometime mercenary, and his wife Katharina Guldenmann, the daughter of an innkeeper.


Weil der Stadt 1682, Forstlagerbuch by Andreas Kieser Source: Wikimedia Commons

Kepler’s father disappeared when he was just five years old, not the most auspicious start in life. The young Kepler grew up in his grandfather’s inn. According to Kepler in one of his autobiographical sketches it was his mother, who first awakened his interest in astronomy. She took him outside in the night to view the Great Comet of 1577 and again in 1580 to view a lunar eclipse.


The Great comet of 1577, seen over Prague on November 12. Engraving made by Jiri Daschitzky. Source: W§Wikimedia Commons

Kepler must have been an intelligent child because he received a grant from the Duchy of Württemberg to study first at the convent-school, Adelberg, in 1584 then at the seminary at Maulbronn in 1586 he graduated BA at the University of Tübingen in 1588 but returned to Maulbronn for another year. In 1589 he entered the Tübinger Stift, the hall of residence of the Lutheran Protestant Church at the University of Tübingen. Kepler’s grant was part of scheme to train Lutheran pastors and schoolteachers to replace the Catholic ones lost through Württemberg becoming Protestant. He graduated MA in 1591.


Tübinger Still (left) and University (right) Source: Kepler-Gesellschaft e.V.

It is a widespread myth that Kepler now studied theology but in fact he remained at the university receiving instruction in the various practical aspects of his potential future career, teaching practice, basic theology for sermons and so forth until a suitable vacancy became available. Kepler, who was deeply religious, desired to become a pastor, however, when a vacancy for a maths teacher in Graz became available he was recommended for the post and after some hesitation he accepted reluctantly his new position, which included the post of district mathematicus and beginning in 1594.


Johannes Kepler (artist unknown) Source: Wikimedia Commons

During his studies in Tübingen he came under the influence of Michael Mästlin and was one of those, who received an introduction to Copernicus’ heliocentric hypothesis, which he immediately adopted with enthusiasm. He succeeded in acquiring a second hand copy of the first edition De revolutionibus in 1598–the book was by now 55 years old–which is still extant.

Kepler was still very miffed about the fact that he was teaching teenagers mathematics rather than serving his God as a pastor when he had what could be best described as an epiphany whilst teaching astronomy to a class on 19 July 1595. At the time Kepler was trying to find a conclusive argument as to why there are only six planets thus supporting a heliocentric model against a geocentric one that has seven planets. During his teaching he drew a diagram illustrating the cyclical pattern of the occurrences of the so-called Great Conjunctions of Saturn and Jupiter, something considered very important in astrology.

0 N UMAX     Mirage IIse      V1.0 [4]

Kepler’s diagram of the Great Conjuctions of Saturn and Jupiter

Viewing his own diagram he had a revelation and thought, the orbits of the planets are separated by geometrical figures! Initially he tried various regular polygons but couldn’t get a good fit between his figures and the known distances between the planetary orbits. His next thought was that space in naturally three-dimensional and the polygons are only two-dimensional, also there are infinitely many regular polygons so not a good potential argument for a specific limited number of planets. He now turned to polyhedra; then he had his second aha moment. There are only five regular Euclidian polyhedra, so the each of the five paths between the six planets was defined by one of these:

If, for the sizes for the relations of the six heavenly paths assumed by Copernicus, five figures possessing certain distinguishing characteristics could be discovered among the remaining infinitely many, then everything would go as desired.

The Earth is the measure of all other orbits. Circumscribe a twelve-sided regular solid about it; the sphere stretched around this around this will be that of Mars. Let the orbit around Mars be circumscribed by a four-sided solid. The sphere which is described around this will be that of Jupiter. Let Jupiter’s orbit be circumscribed by a cube. The sphere described about this will be that of Saturn. Now, place a twenty-sided figure in the orbit of the Earth. The sphere inscribed in this will be that of Venus. In Venus’ orbit place an octahedron. The sphere inscribed in this will be that of Mercury. There you have the basis for the number of planets.


Kepler’s Platonic solid model of the solar system, from Mysterium Cosmographicum (1596) Source: Wikimedia Commons

This astronomical epiphany led Kepler to the realisation that his God was a geometer and his call was to worship his God by revealing the geometrical structure of creation. His desire to become a pastor died and Johannes Kepler the astronomer was born.

He quickly turned his revelation into what became the first of his many books his Prodromus dissertationum cosmographicarum, continens mysterium cosmographicum, de admirabili proportione orbium coelestium, de que causis coelorum numeri, magnitudinis, motuumque periodicorum genuinis & proprijs, demonstratum, per quinque regularia corpora geometrica (Forerunner of the Cosmological Essays, Which Contains the Secret of the Universe; on the Marvelous Proportion of the Celestial Spheres, and on the True and Particular Causes of the Number, Magnitude, and Periodic Motions of the Heavens; Established by Means of the Five Regular Geometric Solids), usually known simply as the Mysterium Cosmographicum (the Cosmographic Mystery).


The fit between the Euclidian regular solids and the planetary orbits turned out to be fairly good with less that 10% error. Kepler would dedicate much of his later life to trying to eliminate that error through various strategies.

Supported by Mästlin, Kepler obtained permission from the University of Tübingen to publish this book, although the university insisted on removing some theological passages from the manuscript. Any doubts about Mästlin’s commitment to heliocentricity were removed by the publication of this book in 1596, which contains an introduction on the Copernican system written by Mästlin and his addition of Rheticus’ Narratio Prima to the book, as an appendix.

At this point in his life Kepler was a twenty-five year old schoolteacher in the Austrian provinces without any sort of reputation. To try and acquire some recognition he sent complimentary copies of his freshly printed tome to various notable European astronomers. As we shall see two of those complimentary copies played a significant roll in his future life, one of them causing him immense embarrassment the other setting him up for his future as a leading astronomer.

However, before we go down that path, there is a widespread myth that Kepler sent a copy of the Mysterium Cosmographicum to Galileo in Padua. At this point in his life Galileo was almost as unknown as Kepler and Kepler had certainly never heard of him. In fact Galileo did receive two copies of Kepler’s first book entirely by chance (you can read the full story here) and wrote a brief letter thanking the author. This letter was Galileo’s earliest known written commitment to the Copernican heliocentric hypothesis.

The two fateful copies that Kepler sent out were to Nicolaus Reimers Baer (1551–1600), known as Ursus, who was at the time Imperial Mathematicus on the court of Rudolf II in Prague and to Tycho Brahe (1546­–1601), Europe’s leading observational astronomer on his island of Hven. Kepler was unaware that the two recipients of his first efforts were at the time involved in a very public slanging match about who invented the geo-heliocentric system and whether Ursus has plagiarised it from Tycho. In fairly typical Renaissance manner Kepler had in his accompanying letter to Ursus addressed the Imperial Mathematicus in fawning heaps of praise of his abilities and achievements. Unknown to Kepler, Ursus then quoted that praise in one of his publications bitterly attacking Tycho. The result was that Kepler was in Tycho’s bad books long before he ever met him.

Graz is the capital of Styria in Austria an area that at the end of the sixteenth century was deeply Catholic with only a comparatively small Protestant minority. The Counter Reformation was in full swing and all of the Protestants were ordered to leave the province. Kepler was exempted from the ban on Protestant due to his successful astrological prognostica, part of his obligations as district mathematicus. However, as religious tensions rose the remaining Protestants were banned from the province and this time Kepler received no exemption. Now married and with children Kepler desperately needed a new position. He wrote to Mästlin in Tübingen but his one time mentor now refused to assist him in anyway. In the end he applied to Tycho, now installed in Prague as Imperial Mathematicus, for a position, any position. Due to the vagaries of the sixteenth century post system Kepler had not yet received any reply from Tycho when he set off in 1600 to Prague hoping to find a solution to his seemingly impossible situation but blissfully unaware that Tycho had a serious bone to pick with him. He also hoped to gain access to Tycho’s observational data, the most accurate available and several levels more accurate than the data Kepler had had available when he wrote his Mysterium Cosmographicum. With Tycho’s data he was convinced he would be able to remove that error in his model of the cosmos.










1 Comment

Filed under History of Astronomy, History of science