Category Archives: Renaissance Science

He fought for his mother

There are not many books about the Renaissance mathematician and astronomer Johannes Kepler in which he only plays a supporting role but this is the case in Ulinka Rublack’s The Astronomer and the Witch: Johannes Kepler’s Fight for His Mother[1]. In fact in Rublack’s excellent book even Kepler’s mother, Katherina, the nominal subject of the book only really takes a supporting role; the lead role being taken by the context within which the whole tragic story unfolds and it is exactly this that makes this book so excellent.


Regular readers of this blog will know that I champion the claims of Johannes Kepler to being the most significant natural philosopher of the Early Modern Period against the rival claims of Copernicus, Galileo, Descartes, Newton et al. So I am naturally interested in any new books that appear with Kepler as their subject. Having looked closely at one of the strangest events in Kepler’s unbelievably bizarre life, the arrest and trial of his mother, Katherina, on a charge of witchcraft – and having blogged about it twice – my interest was particularly piqued by an announcement of a new book on this topic. A decent, well-researched book in English devoted exclusively to the subject would be a very positive addition to the Kepler literature. Rublack’s book is just the bill.

Nearly all accounts of Katherina Kepler’s ordeal are merely chapters or sections in more general books about Kepler’s life and work and mostly deal chronologically with the original accusations of witchcraft, counter accusations, the attempted violent intimidation of Katherina, the frustrated strivings to bring charges against her tormentors, her arrest and finally the trial with its famous defence by Johannes. Except for thumbnail sketches of those involved very little attempt is ever made to place the occurrences into a wider or more general context and this is, as already said above, exactly the strength of Rublack’s book.

Rublack in having devoted an entire book to the whole affair draws back from the accusations, charges, counter charges and the trial itself to flesh out the story with the social, cultural, political and economic circumstances in which the whole sorry story took place. In doing so Rublack has created minor masterpiece of social history. Her research has obviously been deep and thorough and she displays a fine eye for detail, whilst maintaining a stirring narrative style that pulls the reader along at a steady pace.

One point in particular intrigued me having read all the prepublication advertising for the book, including several illuminating interviews on the subject with the author, as well as short essays by her. Rublack takes what might be seen as a strong feminist stand against the previous, exclusively male, characterisations of Katherina Kepler, all of which painted her as a mean spirited, crabby, old hag, who was, so to speak, largely to blame for the situation in which she found herself. Having over the years read almost all of these accounts I was curious how Rublack would justify her rejection of these portrayals of Katherina, which I knew were based on Kepler’s own accounts of his mother. Rublack does not disappoint. She points out quite correctly that Kepler’s description of his mother was written when he was still very young and is part of an almost psychopathic put down of himself and all those related or connected to him and calls rather his own mental state into question. Interestingly we have virtually no other accounts of Katherina from Johannes’ pen and to judge her purely on this one piece of strange juvenilia is probably, as Rublack makes very clear, a bridge too far. Piecing together all of the, admittedly scant, evidence Rublack paints a much more sympathetic picture of Katherina, a hard working, illiterate, sixteenth/seventeenth-century peasant woman, who had never had it easy in life but still managed to raise her children well and give them chances that she never had.

This book is not perfect, as Rublack relies in her accounts of Johannes on older standard biographies, whilst apparently not consulting some of the more recent scholarly studies of his life and work, and thus repeats several false claims concerning him. However I’m prepared to cut her some slack on this as none of the errors that she (unknowingly?) repeats have any direct bearing on the story of Katherina that she tells so skilfully.

The book is beautifully presented by the OUP. Printed in a pleasant, easy on the eyes typeface and charmingly illustrated with a large number of black and white pictures. The text is excellently annotated, but as always I would have preferred footnotes to endnotes, and there is an adequate index. I personally would have liked a separate bibliography but this might have been sacrificed on cost grounds, the hardback being available at a very civilised price for a serious academic volume. Although having called it that I should point out that the book is very accessible and readable for the non-expert or general reader.

I heartily recommend this book to anybody interested in seventeenth-century history, Johannes Kepler, the history of witchcraft or who just likes reading good informative, entertaining books, if one is allowed to call a book about the sufferings of an innocent woman entertaining. Put simply, it’s an excellent read that deserves to, and probably will, become the standard English text on the subject.

[1] Ulinka Rublack, The Astronomer and the Witch: Johannes Kepler’s Fight for His Mother. OUP, 2015





Filed under Book Reviews, History of Astronomy, Renaissance Science

Christmas Trilogy 2016 Part 3: The English Keplerians

For any scientific theory to succeed, no matter how good or true it is; it needs people who support and propagate it. Disciples, so to speak, who are prepared to spread the gospel. Kepler’s astronomical theories, his three laws of planetary motion and everything that went with them, were no different from every other theory in this aspect; they needed a fan club. On the continent of Europe the reception of Kepler’s theories was initially lukewarm to say the least and it was not only Galileo, who did his best to ignore them. Therefore it is somewhat surprising that they found a group of enthusiastic supporters right from the beginning in England. Surprising because in general in the first half of the seventeenth century England lagged well behind the continent in astronomy, as in all things mathematical.

The first Englishmen to pick up on Kepler’s theories was the small group around Thomas Harriot, who did so immediately after the publication of the Astronomia nova in 1609.

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

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

The group included not only Harriot but also his lens grinder Christopher Tooke, the Cornish MP Sir William Lower (c.1570–1615) and his Welsh neighbour John Prydderch (or Protheroe). Lower had long been an astronomical pupil of Harriot’s and had in turn introduced his neighbour Prydderch to the science.

The cartoon of Lower and Prydderch on page 265 of Seryddiaeth a Seryddwyr By J.S. Evans. Lower looks through a telescope while Prydderch holds a cross-staff. The cartoon had been used earlier by Arthur Mee in his book The Story of the Telescope in 1909. The artist was J. M. Staniforth, the artist-in-chief of the Western Mail newspaper.

The cartoon of Lower and Prydderch on page 265 of Seryddiaeth a Seryddwyr By J.S. Evans. Lower looks through a telescope while Prydderch holds a cross-staff. The cartoon had been used earlier by Arthur Mee in his book The Story of the Telescope in 1909. The artist was J. M. Staniforth, the artist-in-chief of the Western Mail newspaper.

This group was one of the very earliest astronomical telescopic observing teams, exchanging information and comparing observations already in 1609/10. In 1610 they were enthusiastically reading Astronomia nova and discussing the new elliptical astronomy. It was Lower, who had carefully observed Halley’s comet in 1607 (pre-telescope) together with Harriot, who first suggested that the orbits of comets would also be ellipses. Kepler still thought that comets move in straight lines. The Harriot group did not publish their active support of the Keplerian elliptical astronomy but Harriot was well networked within the mathematical communities of both England and the Continent. He had even earlier had a fairly substantial correspondence with Kepler on the topic of atmospheric refraction. It is a fairly safe assumption that Harriot’s and Lower’s support of Kepler’s theories was known to other contemporary English mathematical practitioners.

Our next group of English Keplerians is that initiated by the astronomical prodigy Jeremiah Horrocks (1618–1641). Horrocks was a self-taught astronomer who stumbled across Kepler’s theories, whilst on the search for reliable astronomical tables. He quickly established that Kepler’s Rudolphine Tables were superior to other available tables and soon became a disciple of Kepler’s elliptical astronomy. Horrocks passed on his enthusiasm for Kepler’s theories to his astronomical helpmate William Crabtree (1610–1644). In turn Crabtree seems to have been responsible for converting another young autodidactic astronomer William Gascoigne (1612–1644) to the Keplerian astronomical gospel. Crabtree referred to this little group as Nos Keplari. Horrocks contributed to the development of Keplerian astronomy with an elliptical model of the Moon’s orbit, something that Kepler had not achieved. This model was the one that would eventually make its way into Newton’s Principia. He also corrected and extended the Rudolphine Tables enabling Horrocks and Crabtree to become, famously, the first people ever to observe a transit of Venus.


Like Harriot’s group, Nos Keplari published little but they were collectively even better networked than Harriot. Horrocks had been at Oxford Emmanual College Cambridge with John Wallis and it was Wallis, a convinced nationalist, who propagated Horrocks’ posthumous astronomical reputation against foreign rivals, as he also did in the question of algebra for Harriot. Both Gascoigne and Crabtree had connections to the Towneley family, landed gentry who took a strong interest in the emerging modern science of the period. Later the Towneley’s who had connections to the Royal Society ensured that the work of Nos Keplari was not lost and forgotten, bringing it, amongst other things, to the attention of a young John Flamsteed, who would later become the first Astronomer Royal. . Gascoigne had connections to William Cavendish, the later Duke of Newcastle, under whose command he served at the battle of Marston Moor, where he died. William, his brother Charles and his wife Margaret were all enthusiastic supporters of the new sciences and important members of the English scientific and philosophical community. Gascoigne also corresponded with William Oughtred who served as private mathematics tutor to many leading members of the burgeoning English mathematical community. It is to two of Oughtred’s students that we now turn

William Oughtred by Wenceslas Hollar 1646

William Oughtred
by Wenceslas Hollar 1646

Seth Ward (1617–1689) studied at Oxford Cambridge University from 1636 to 1640 when he became a fellow of Sidney Sussex College.

Greenhill, John; Seth Ward (1617-1689), Savilian Professor of Astronomy, Oxford (1649-1660) Source: Wikimedia Commons

Greenhill, John; Seth Ward (1617-1689), Savilian Professor of Astronomy, Oxford (1649-1660)
Source: Wikimedia Commons

In the same year he took instruction in mathematics from William Oughtred. In 1649 he became Savilian Professor of Astronomy at Oxford University the same year that John Wallis was appointed Savilian Professor of Mathematics. Whilst serving as Savilian Professor, Ward became embroiled in a dispute about Keplerian astronomy with the French astronomer and mathematician Ismaël Boulliau.

Ismaël Boulliau  Source: Wikimedia Commons

Ismaël Boulliau
Source: Wikimedia Commons

Boulliau was an early and strong defender of Keplerian elliptical astronomy, who however rejected Kepler’s attempts to create a physical explanation of planetary orbits. Boulliau published his Keplerian theories in his Astronomia philoaïca in 1645. Ward attacked Boulliau’s model in his In Ismaelis Bullialdi astro-nomiae philolaicae fundamenta inquisitio brevis from 1653, presenting his own model for Kepler’s planetary laws. Boulliau responded to Ward’s attack in his De lineis spiralibus from 1657. Ward had amplified his own views in his Astronomia geometrica from 1656. This public exchange between two heavyweight champions of the elliptical astronomy did much to raise the general awareness of Kepler’s work in England. It has been suggested that the dispute was instrumental in bringing Newton’s attention to Kepler’s ideas, a claim that is however disputed by historians.

Ward went on to make a successful career in the Church of England, eventually becoming Bishop of Salisbury his successor, as Savilian Professor of Astronomy was another one of Oughtred’s student, Christopher Wren (1632–1723).

Christopher Wren by Godfrey Keller 1711  Source: Wikimedia Commons

Christopher Wren by Godfrey Keller 1711
Source: Wikimedia Commons

Wren is of course much better known as the foremost English architect of the seventeenth-century but started out as mathematician and astronomer. Wren studied at Wadham College Oxford from 1650 to 1653, where he was part of the circle of scientifically interested scholars centred on John Wilkins (1614–1672), the highly influential early supporter of heliocentric astronomy. The Wilkins group included at various times Seth Ward, John Wallis, Robert Boyle, William Petty and Robert Hooke amongst others and would go on to become one of the groups that founded the Royal Society. Wren was a protégé of Sir Charles Scarborough, a student of William Harvey who later became a famous physician in his own right; Scarborough had been a fellow student of Ward’s and was another student of Oughtred’s. Wren was appointed Gresham Professor of Astronomy and it was following his lectures at Gresham College that the meetings took place that would develop into the Royal Society. As already noted Wren then went on to succeed Ward as Savilian Professor for astronomy in 1661, a post that he resigned in 1673 when his work as Surveyor of the King’s Works (a post he took on in 1669), rebuilding London following the Great Fire of 1666, became too demanding. Wren enjoyed a good reputation as a mathematician and astronomer and like Ward was a convinced Keplerian.

Our final English Keplerian is Nicolaus Mercator (1620–1687), who was not English at all but German, but who lived in London from 1658 to 1682 teaching mathematics.

Nicolaus Mercator © 1996-2007 Eric W. Weisstein

Nicolaus Mercator
© 1996-2007 Eric W. Weisstein

In his first years in England Mercator corresponded with Boulliau on the subject of Horrock’s Transit of Venus observations. Mercator stood in contact with the leading English mathematicians, including Oughtred, John Pell and John Collins and in 1664 he published a defence of Keplerian astronomy Hypothesis astronomica nova. Mercator’s work contained an acceptable mathematical proof of Kepler’s second law, the area law, which had been a bone of contention ever since Kepler published it in 1609; Kepler’s own proof being highly debateable, to put it mildly. Mercator continued his defence of Kepler in his Institutiones astronomicae in 1676. It was probably through Mercator’s works, rather than Ward’s, that Newton became acquainted with Kepler’s astronomy. We still have Newton’s annotated copy of the latter work. Newton and Mercator were acquainted and corresponded with each other.

As I hope to have shown there was a strong continuing interest in England in Keplerian astronomy from its very beginnings in 1609 through to the 1660s when it had become de facto the astronomical model of choice in English scientific circles. As I stated at the outset, to become accepted a new scientific theory has to find supporters who are prepared to champion it against its critics. Kepler’s elliptical astronomy certainly found those supporters in England’s green and pleasant lands.





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

Another public service announcement

Marius Book Launch

In September 2014 a conference was held in Nürnberg, as the climax of a year dedicated to celebrating the life and work of the Franconian astronomer, astrologer and mathematician Simon Marius, whose magnum opus Mundus Iovialis was published four hundred years earlier in 1614.

The papers held at that conference together with some other contributions from people who could not attend in person have now been collected together in the book Simon Marius und Seine Forschung, eds. Hans Gaab and Pierre Leich (= Acta Historica Astronomiae, Band 57) which will be official launched in the Thalia bookshop in Nürnberg on this coming Thursday, 13 October at 18:30 MET.

This volume contains papers by a wide range of scholars and could/should be of interest to anybody studying the histories of astronomy, astrology and/or mathematics in the Early Modern Period. It can be purchased online, after Thursday, directly from the publishers, Leipziger Universitätsverlag


For those who would like to know more about the book including a table of contents (Inhaltsverzeichnis) they can inform themselves on the Marius Portal here.

For those who cannot read German, an English edition of the book is in planning for next year, for which further contributions on the life and work of Simon Marius would also be welcome. If anybody has any questions regarding this volume I would be happy to answer them.


P.S. For those waiting for blogging to resume here at the Renaissance Mathematicus I can report that there is light at the end of the tunnel!





1 Comment

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

Not an expert

BBC Radio 4 has a series called Great Lives, which is presented by former Conservative MP and now journalist, writer and broadcaster Matthew Parris. On the programme a ‘lay person’ talks about a figure, usually from history, who is their hero or role model, their comments being filled out by an ‘expert’ on the life of the figure in question. The format is in the form of a light-hearted three-way chat. Three years ago the BBC DJ Bobby Friction chose Galileo Galilei as his Great Life. At the time I listened and not surprisingly found the programme cringe worthy, dismissed it and forgot about it. However over the weekend people, who should know better, were promoting the programme on social media. Against my better judgement I listened to the whole thing again and decided to write this brief post on just one aspect, the greatest historical blunder, of the programme.

Before turning to the main topic of this post there is an aspect of the programme that needs to be addressed first. As explained above the discussion always includes an ‘expert’ to fill out with facts the account given of the subject of the programme. A programme about Galileo, so we can expect a historian of science as expert, yes? No! Instead of a historian of science what we get is Dr David Berman a reader in theoretical physic from Queen Mary College London. This is unfortunately a very common habit amongst journalists and broadcasters. They want someone to comment on, or explicate some aspect of, or episode out of the history of science, they ask a scientist and not a historian of science. Whilst I’m quite happy to acknowledge that there are some scientists who are also competent historians of science, they are unfortunately a small minority. The majority of scientists when asked to talk about the history of their subject usually deliver something highly inaccurate, factually false and toe curlingly cringe worthy. David Berman is no exception. As I wrote above, I’m not going to waste my time, and yours, doing a blow by blow analysis of this sorry mess but just address the one truly glaring clangour that our so-called expert drops towards the end of the discussion.

In an exchange beginning at about 22.20mins we hear the following:

MP: But he was friends with the Pope, why didn’t the Pope stick up for him?

DB: Oh, so he was friends with Urban VII who was the Pope, who was around the time when he started the book and the original censor but by then he died and we had Urban VIII…

He we have the classic example of a so-called expert who has literally no idea what he’s talking about and just makes something up that he thinks sounds plausible. For those that don’t know their papal history and/or the story of Galileo’s interaction with the papacy I will explain.

Paul V (1552–1621) was the Pope (1605–1621) who set up the commission of theologians in 1616 to consider the status of heliocentricity, which ruled it “foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture”. He then instructed Cardinal Bellarmine to meet with Galileo and to inform him that he was no longer allowed to teach the truth of heliocentricity.

Pope Paul V by Caravaggio. Source: Wikimedia Commons

Pope Paul V by Caravaggio.
Source: Wikimedia Commons

Both Bellarmine and Paul, however, assured Galileo that he was, at this time, in no personal danger. Paul died in 1621 and was succeeded by Gregory XV (1554–1623) who as Pope (1621–1623) played no significant role in the life of Galileo.

Pope Gregory XV Source: Wikimedia Commons

Pope Gregory XV
Source: Wikimedia Commons

Gregory was succeeded in 1623 by Cardinal Maffeo Barberini (1568–1644) who became Urban VIII.

Circa 1598 painting of Maffeo Barberini at age 30 by Caravaggio. Source: Wikimedia Commons

Circa 1598 painting of Maffeo Barberini at age 30 by Caravaggio.
Source: Wikimedia Commons

Those of you wondering where Urban VII fits into this, he doesn’t. Giovanni Battista Castagna (1521–1590) ruled as Pope Urban VII for just twelve days between 15 and 27 September 1590, when Galileo was just beginning his career as professor for mathematics in Pisa. Urban VII’s twelve-day papacy was the shortest in history.

Pope Urban VII – Pope for Twelve Days Source: Wikimedia Commons

Pope Urban VII – Pope for Twelve Days
Source: Wikimedia Commons

As an additional comment no Pope was ever the censor, as claimed by Berman, but naturally employed others to do this work for the Church.

As Matthew Parris rightly claims Cardinal Maffeo Barberini had been a friend and supporter of Galileo’s since the publication of the Sidereus nuncius in 1610 as well as being a patron of the Accademia dei Lincei, the small elite scientific society that had elected Galileo a member in 1611 on the strength of his telescopic discoveries. It was also the Lincei who gave the telescope its name. When Barberini was elected Pope in 1623 the Lincei published a broadsheet celebrating his election, which contained the first every illustrations made with a microscope.

Accademia dei Lincei Flyer celebrating the elevation of Maffeo Barberini to Pope 1623 Stelutii Melissographia

Accademia dei Lincei Flyer celebrating the elevation of Maffeo Barberini to Pope 1623
Stelutii Melissographia

The Lincei also published Galileo’s Il Saggiatore (The Assayer), which was dedicated to the new Pope in 1623.

Title page Il Saggiatore !623 Source: Wikimedia Commons

Title page Il Saggiatore !623
Source: Wikimedia Commons

Barberini much enjoyed Il Saggiatore and showed Galileo much favour. Galileo grasped the opportunity and persuaded the Pope to let him write a book describing the geocentric and heliocentric systems to prove that the Catholics did not favour the former out of ignorance of the latter, as he claimed the Protestants were alleging. Urban agreed to his request but under the condition that the two systems were presented equally without bias and without favouring either.

A portrait of Pope Urban VIII by Pietro da Cortona (1627) Source: Wikimedia Commons

A portrait of Pope Urban VIII
by Pietro da Cortona (1627)
Source: Wikimedia Commons

The book that Galileo wrote, his Dialogo, a polemic masterpiece, was of course anything but unbiased, tilting the arguments so far that any reader would be led to the conclusion that the heliocentric system was vastly superior to the geocentric one; a claim for which he had no empirical proof. He topped the whole thing off by putting the Pope’s own thoughts on the subject, a direct quote, into the mouth of a figure who was close to being a simpleton at the climax of the book.

Frontispiece and title page of the Dialogo, 1632 Source: Wikimedia Commons

Frontispiece and title page of the Dialogo, 1632
Source: Wikimedia Commons

That Urban was pissed off by the results should not have come as a surprise to Galileo and things took their inevitable course. The motto of the story is don’t play your friend for a fool when he happens to be an all powerful absolutist ruler.


Filed under History of Astronomy, Renaissance Science

Galileo Super Star – Galileo Galilei to get Hollywood biopic

My attention was drawn recently to a Hollywood gossip website that announced that a movie is to be made of a play by Richard Goodwin about Galileo, The Hinge of the World. I must admit that my curiosity was piqued, not least because I had never heard of either Mr Goodwin or his play and I naturally wondered what his line on the Tuscan mathematicus would be. It turns out that Richard Goodwin is a former high power Washington political advisor and speechwriter who served Presidents Kennedy and Johnson as well as JFK’s brother Robert, not exactly the best qualifications for the author of a play about the history of science. My doubts about this particular production were only heightened upon reading the full original title of the play, The Hinge of the World: In Which Professor Galileo Galilei, Chief Mathematician and Philosopher to His Serene Highness the Grand Duke of Tuscany, and His Holiness Urban VIII, Bishop of Rome, Battle for the Soul of the World. This title does not bode well for a historically accurate account of Galileo’s clash with the Catholic Church. However I will reserve judgement, because as I say, I do not know the play. I have however ordered a second hand copy that is at this very moment wending its way from some distant land to my humble abode and when it arrives and I have perused it with due diligence, I will report back with a critical assessment.

A scene from the stage production of The Hinge of the World

A scene from the stage production of The Hinge of the World

The website report does however offer a précis of the contents of the soon to be film and this is possibly the most confused and inaccurate presentation of the affair and the events leading up to it that I have read in a very long time:

The film will stay true to the spirit of the play in that it will revolve around the one-time friends whose vehement disagreements led to the Church calling Galileo out for heresy when science started to challenge long-held beliefs.

Science had been challenging long held beliefs long before Galileo came along. Apart from anything else Galileo was tried for defending the truth of Copernicus’ heliocentric hypothesis and Copernicus had died twenty-one years before Galileo was born. Just for the record Copernicus was also by no means the first person to present science that challenged the Church’s long-held beliefs.

Just to be a little bit pedantic, the one-time friends, Galileo and Maffeo Barberini (Pope Urban VIII) only had one vehement disagreement.

During that time, around 1610, the Church was never questioned,…

Somebody really ought to have consulted a historian of the Catholic Church. People both inside and outside of the Church questioned it continuous, some with impunity, for example Galileo’s friend Paolo Sarpi, and some with dire consequences, such as Giordano Bruno.

…yet Galileo who had a passion, curiosity and a telescope started to question everything after logging what he was learning through his scientific research. He published much of his findings in a book that were disavowed by Pope Urban VIII and the Catholic Church. Despite delving into dangerous territory, Galileo continued his research into comets, tide movements until he was ultimately ordered by the Church to stop teaching his ideas.

 The above is just a historical train wreck. The book of Galileo’s disavowed by Urban VII and the Church was the Dialogue Concerning the Two Chief World Systems, published in 1632, which led directly to his trail and imprisonment in 1633. However, he was told to stop teaching the truth of the heliocentric hypothesis and only that, the rest of his ideas were not the subject of Church condemnation, in 1616 following the semi-public distribution of the so-called Letter to Castelli, much later published in expanded form, as the Letter to the Grand Duchess Christina. Also in 1616 Paul V was Pope and Maffeo Barberini was a mere Cardinal and still a good friend of Galileo’s.

 The brilliant scientist, engineer, physicist and mathematician who helped discover the law of the pendulum (which became the basis for modern-day clocks), who pushed scientists to conduct experiments to prove theorems, who continued the work of Nicolaus Copernicus to help understand our own universe and laid the groundwork for modern astronomy eventually lost his battle with the powerful Roman Catholic Church.

Again being somewhat pedantic, Galileo got the law of the pendulum wrong and modern day clocks stopped being pendulum driven some time ago. Also, and this is not so pedantic, it was Kepler, and not Galileo, who laid the groundwork for modern astronomy.

 He was tried for heresy and sentenced to imprisonment at the age of 68 where he would remain until his death nine years later at age 77.

A final point, that people love to forget because it rather spoils the image of Galileo the martyr, his sentence of imprisonment imposed for vehement suspicion of heresy, not heresy, was instantly commuted to house arrest, which whilst somewhat restrictive was by no means harsh.


All of this ties in rather nicely with an exchange that I took part in yesterday evening on twitter. Tim Skellet (@Gurdur) asked me and others, “what’s the very best, most comprehensive bio of Galileo, please?” My answer was, “I don’t think it exists. Read several: Wootton, Heilbron, Biagioli, Shea/Artigas.” I was not trying to be clever or awkward. I genuinely believe that if you wish to study any major figure out of the history of science then you should consult multiple sources, as all sources have their advantages and disadvantages. History is, to a large extent, a game of interpretation. There are facts but they only give a partial picture and it is the role or responsibility of the historian to complete that picture to the best of their ability. All historians have agendas and biases and to obtain a rounded picture it is always advisable to view the facts through the eyes of more than one historian.

Turning to the special case of Galileo, the two most recent complete biographies are J. L. Heilbron’s Galileo (OUP, 2010) and David Wootton’s Galileo: Watcher of the Skies (Yale University Press, 2010). Both are very good but differ in their interpretations and emphases. I wouldn’t recommend one over the other, so if you only want to read one then toss a coin or something. If you really want to get to grips with Galileo then read both. One important aspect of Wootton’s book is that he systematically dismantles the myth that Galileo was a good devout Catholic. This myth is trotted out regularly to make the Church look even worse for having persecuted him. Wootton demonstrates, I think convincingly, that Galileo was at best an indifferent Catholic and in no way the devout son of the Church that historical myth has made him out to be.

Although not a complete biography in the traditional sense I would also strongly recommend Mario Biagioli’s Galileo Courtier: The Practice of Science in the Culture of Absolutism (University of Chicago Press, 1993) Biagioli examines Galileo the social climber who uses his scientific discoveries to further his social status rather than for any idealistic belief in truth. Biagioli’s work is a useful complement to the more conventional scientific style of biography; what did Galileo discover and when. In what is effectively a second volume to his first book, Galileo’s Instruments of Credit: Telescopes, Images, Secrecy (University of Chicago Press, 2006), Biagioli explains how Galileo used the telescopes that he manufactured and the images that he produced to broker social advantages.

William R. Shea’s and Mariano Artigas’ Galileo in Rome: The Rise and Fall of a Troublesome Genius (OUP; 2003) just deals with the six extended visits that Galileo made to Rome, the home-base of the Church and the centre of political and social power in the period, during his lifetime. These include, his triumphal visit in 1611, as the author of his sensational Sidereus Nuncius, his visit in 1615-1616 and his failed attempt to prevent the Church condemning heliocentricity and finally his summons to his trial in 1633. By concentrating only on Galileo’s interactions with the Roman culture of the period the authors succeed in shedding light from a different angle on Galileo’s fateful path to his condemnation and fall.

At some point David Wootton joined the Twitter discussion and he recommended Pietro Redondi’s Galileo Heretic (Princeton University Press, 1992), a recommendation that I would one hundred pro cent endorse. Although Redondi’s central thesis, that Galileo was actually attacked by the Church for his atomism has, in the meantime, been largely refuted this is a superb book and still very much worth reading by anyone who wishes to learn about Galileo and the culture in which he lived and worked.

If you read all of the books that I have recommended above you should, by the time you have finished, have a fairly good all round picture of the life and work of Galileo Galilei and the footnotes and bibliographies will have given you lots of information for further reading. I will however close with a warning, do not read Michael White’s Galileo Antichrist: a Biography (Weidenfeld & Nicolson, 2007). I can deliver a comprehensive and profound review of White’s book in three words, “It is crap!”



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

Tracking the Messenger of the Gods

On 9 May the astronomers of Europe, and other regions, having screwed their sun filters onto their telescopes, will settle down to observe a transit of Mercury. For any not familiar with astronomical jargon that is when the planet Mercury crosses the face of the sun.

Astronomy Picture of the Day: A Mercury Transit Sequence: Image Credit & Copyright Dominique Dierick

Astronomy Picture of the Day: A Mercury Transit Sequence: Image Credit & Copyright Dominique Dierick

Neither as rare nor as spectacular as the similar transits of Venus, it will still be regarded as a major event in the astronomical calendar. Transits of Venus occur in pairs separated by eight years approximately once every one hundred and twenty years. The last pair was in 2004 and 2012. The cycle of occurrences of transits of Mercury is much more complex but there will be a total of fourteen in the twenty-first century with next Monday’s being the third. Because Mercury is much smaller than Venus and much further from the Earth, unlike a transit of Venus which can be observed with the naked-eye (taking the necessary precautions against the sunlight of course), a transit of Mercury can only be observed with a telescope. The French astronomer, Pierre Gassendi, was the first person to observe a transit of Mercury in 1631 but this historic event was preceded by a couple of thousand years of speculation about the orbital path of the Messenger of the Gods.

Pierre Gassendi after Louis-Édouard Rioult. Source: Wikimedia Common

Pierre Gassendi
after Louis-Édouard Rioult.
Source: Wikimedia Common

Both Mercury and Venus when viewed from the Earth never appear to move very far away from the sun leading some astronomers in antiquity to suggest the so-called Heracleidian of Egyptian system in which the two planets orbited the sun whilst the sun orbited the earth in a geocentric system. Thanks to the De nuptiis of Martianus Cappella (fl. 410-420 CE) this partial helio-geocentric model was well known and moderately popular in the Middle Ages, so the idea that Mercury and Venus orbit the sun was not new when Tycho Brahe suggested it in his full helio-geocentric system, in which all the planets, except the moon, orbit the sun which in turn orbits the earth.

Naboth's representation of Martianus Capella's geo-heliocentric astronomical model (1573) Source: Wikimedia Commons

Naboth’s representation of Martianus Capella’s geo-heliocentric astronomical model (1573)
Source: Wikimedia Commons

In 1608 Hans Lipperhey invented the telescope and within a very short time various astronomers began to use it to observe the heavens. In November 1610 Benedetto Castelli (1578–1643) wrote to Galileo reminding him that Copernicus had predicted that Venus would have phases like the moon in a heliocentric system[1].

Benedetto Castelli

Benedetto Castelli Source: Wikimedia Commons

On 11 December Galileo wrote to Kepler informing him that he had discovered those phases, famously putting the information into an anagram, which Kepler failed to decode properly. Galileo was not alone in making these observations, Thomas Harriot in England, Simon Marius in Germany and Giovanni Paolo Lembo in Rome all independently discovered the phases proving that Venus did indeed orbit the sun and by analogy Mercury probably did as well. The telescopes in the early seventeenth century were not powerful enough to resolve the phases of Mercury.

That Venus and Mercury had been shown to orbit the sun was not a proof of heliocentricity, as this was also the case in the Heracleidian as well as various Tychonic and semi-Tychonic systems but it did mean that theoretically it should be possible to observe a transit of one or the other of them. Due to the fact that the orbits of the earth, Venus and Mercury do not all lie in the same plane but are all slightly tilted with respect to each other a visible transit does not occur by every orbit but as mentioned above at semi regular irregular intervals and in order to observe such a transit someone first had to calculate when they would take place. This task was carried out by Johannes Kepler in his Rudolphine Tables based on Tycho Brahe’s observations and published in 1627.

Frontispiece Rudolphine Table 1627 Source: Wikimedia Commons

Frontispiece Rudolphine Table 1627
Source: Wikimedia Commons

Using the information supplied by Kepler’s tables Gassendi tried to observe a transit of Venus in 1631 unaware that it would take place at nighttime for an observer in Europe. Kepler’s table lacked this level of accuracy. However earlier in the same year, on 7 November, Gassendi had become the first person to observe a transit of Mercury. The first observation of a transit of Venus was made by Jeremiah Horrocks in 1639. Gassendi was very initially cautious in going public with his discovery because his measurements of the size of the planet showed it to be much smaller than previous estimates. However three further transit observations in the seventeenth century, Jeremy Shakerly 1651, Christiaan Huygens 1661 and Edmund Halley 1677, confirmed Gassendi’s first observations and measurements.

Observation of transits of Mercury have long since become routine but that won’t stop the amateur and professional astronomers on next Monday putting up their telescopes to follow the tracks of the Messenger of the Gods as he plods his way across the sun.

[1] For a fuller description of the discovery of the phases of Venus and its significance for the history of heliocentricity see my post The Phases of Venus and Heliocentricity: A Rough Guide.




Filed under History of Astronomy, Renaissance 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.


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.






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