Christmas Trilogy 2017: Bonus!

Yesterday was Johannes Kepler’s nominal birthday (as he was born before the calendar reform in a Protestant state his birthday on the Gregorian calendar would be 6 January!) and as in my wont, I posted a birthday post for the good Johannes. Of course I was far from being the only person to acknowledge his birthday and amongst many others somebody linked to the 2016 article on the website of the popular science magazine, Physics Today. Upon reading this brief tribute to my favourite seventeenth century polymath I cringed inwardly and didn’t know whether to let out a prolonged #histsigh or to turn loose the HistSci_Hulk; I have decided on the latter. Below the complete text of the offending document:

Born on 27 December 1571 in Weil der Stadt in the Holy Roman Empire, Johannes Kepler was an astronomer whose careful measurements led him to develop his three laws of planetary motion. He received a Lutheran education at the University of Tübingen and originally planned to be a theologian. Then one of his teachers gave him a copy of a book by Nicolaus Copernicus, sparking Kepler’s interest in astronomy. In 1600 Danish astronomer Tycho Brahe invited Kepler to Prague to help amass a precise set of astronomical measurements. Brahe died the following year, and Kepler inherited his mentor’s data and position as imperial mathematician to the Holy Roman emperor. In 1609 Kepler published Astronomia Nova, which included his first two laws of planetary motion; his third law was published in 1619. Kepler observed a supernova (though he called it a “new star”) and completed the detailed astronomical tables Brahe had been so determined to produce. Kepler also contributed research in optics and vision. Later in the century Isaac Newton would prove his law of universal gravitation by showing that it could produce Kepler’s orbits.

Born … in Weil der Stadt in the Holy Roman Empire… This contains something about which I have had bitter disputes on Wikipedia. There is a famous quip that the Holy Roman Empire was neither holy nor Roman nor an empire, it was also neither a country nor a state. The Holy Roman Empire was a loose feudal conglomeration of autonomous and semi-autonomous states. Weil der Stadt, Kepler’s birthplace was at the time of his birth in the autonomous Duchy of Württemberg.


Map of the Duchy of Württemberg 1619 by Pieter van den Keere. You can see Weyl (Weil der Stadt) roughly in the middle. Source: Wikimedia Commons

…Johannes Kepler was an astronomer whose careful measurements led him to develop his three laws of planetary motion. Kepler was a theorist, who didn’t on the whole take measurements careful or otherwise. The measurements that he used to derive his three laws were, of course, made very carefully by Tycho Brahe.

Kepler did not originally plan to be a theologian. He was on an educational tack designed to produce Lutheran Protestant pastors and schoolteachers. He would have become a pastor but was appointed to a position as a maths teacher instead.


Then one of his teachers gave him a copy of a book by Nicolaus Copernicus, sparking Kepler’s interest in astronomy. One of Kepler’s professors in Tübingen was Michael Maestlin, who in his courses taught Copernican heliocentric astronomy alongside the then dominant geocentric astronomy. Kepler took this course and developed an interest in heliocentrism. It was Maestlin who recognised Kepler’s aptitude for mathematics and recommended that he be appointed to a teaching post rather than a village church.

In 1600 Danish astronomer Tycho Brahe invited Kepler to Prague to help amass a precise set of astronomical measurements. Tycho Brahe invited Kepler to Prague not to help amass a precise set of astronomical measurements but to use his mathematical skills to turn the already amassed measurements into calculated orbits, ephemerides etc.

Brahe died the following year, and Kepler inherited his mentor’s data and position as imperial mathematician to the Holy Roman emperor. Kepler didn’t inherit his mentor’s data, Tycho’s daughter Elizabeth and her husband Frans Gansned Genaamd Tengnagel van de Camp did. This caused Kepler no end of problems, as he needed that data to realise his vision of a heliocentric astronomy. After tough negotiations, Tengnagel allowed Kepler to use the data but only if his name was included as co-author on any books that Kepler published based on it; a condition that Kepler duly fulfilled. Given my own inabilities to spell or write grammatically I’m not usually a grammar fetishist but, as I’m putting the boot in, Imperial Mathematician is a title and should be written with capital letters as in the emperor in Holy Roman Emperor.

Kepler observed a supernova (though he called it a “new star”). Well yes, as the term supernova was only coined in 1931 Kepler could hardly have used it. However, the nova part of the name, which simple means new, comes from Kepler’s term Stellar Nova, his being the most recent supernova observed with the naked eye.

…and completed the detailed astronomical tables Brahe had been so determined to produce. Kepler didn’t just complete them he produced them single-handedly, calculating, writing, typesetting, printing, publishing and selling them. This was the task assigned to him by Tycho and to which he was official appointed by the Emperor Rudolph II.

Physics Today is a fairly major popular science magazine but it would appear that they don’t really care enough about the history of science to indulge in a modicum of fact checking.






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

Christmas Trilogy 2017 Part 3: Kepler’s big book

Johannes Kepler was incredibly prolific, he published over eighty books and booklets over a very wide range of scientific and mathematical topics during his life. As far as he was concerned his magnum opus was his Ioannis Keppleri Harmonices mundi libri V (The Five Books of Johannes Kepler’s The Harmony of the World) published in 1619 some twenty years after he first conceived it. Today in popular #histsci it is almost always only mentioned for the fact that it contains the third of his laws of planetary motion, the harmonic law. However it contains much, much more of interest and in what follows I will attempt to give a brief sketch of what is in fact an extraordinary book.


A brief glace at the description of the ‘five books’ thoughtfully provided by the author on the title page (1) would seem to present a mixed bag of topics apparently in some way connected by the word or concept harmonic. In order to understand what we are being presented with we have to go back to 1596 and Kepler’s first book Mysterium Cosmographicum (The Cosmographic Mystery). In this slim volume Kepler presents his answer to the question, why are there only six planets? His, to our eyes, surprising answer is that the spaces between the planets are defined by the regular so-called Platonic solids and as the are, and can only be, five of these there can only be six planets.

Using the data from the greatest and least distances between the planets in the Copernican system, Kepler’s theory produces an unexpectedly accurate fit. However the fit is not actually accurate enough and in 1598 Kepler began working on a subsidiary hypothesis to explain the inaccuracies. Unfortunately, the book that he had planned to bring out in 1599 got somewhat delayed by his other activities and obligations and didn’t appear until 1619 in the form of the Harmonice mundi.

The hypothesis that Kepler presents us with is a complex mix of ideas taken from Pythagoras, Plato, Euclid, Proclus and Ptolemaeus centred round the Pythagorean concept of the harmony of the spheres. Put very simply the theory developed by the Pythagoreans was that the seven planets (we are talking geocentric cosmology here) in their orbits form a musical scale than can, in some versions of the theory, only be heard by the enlightened members of the Pythagorean cult. This theory was developed out of the discovery that consonances (harmonious sounds) in music can be expressed in the ratio of simple whole numbers to each other (the octave for example is 1:2) and the Pythagorean belief that the integers are the building block of the cosmos.

This Pythagorean concept winds its way through European intellectual history, Ptolemaeus wrote a book on the subject, his Harmonice and it is the reason why music was one of the four disciplines of the mathematical quadrivium along with arithmetic, geometry and astronomy. Tycho Brahe designed his Uraniburg so that all the architectonic dimensions from the main walls to the window frames were in Pythagorean harmonic proportion to one another.


Tycho Brahe’s Uraniborg Blaeus Atlas Maior 1663 Source: Wikimedia Commons

It is also the reason why Isaac Newton decided that there should be seven colours in the rainbow, to match the seven notes of the musical scale. David Gregory tells us that Newton thought that gravity was the strings upon which the harmony of the spheres was played.

In his Harmony Kepler develops a whole new theory of harmony in order to rescue his geometrical vision of the cosmos. Unlike the Pythagoreans and Ptolemaeus who saw consonance as expressed by arithmetical ratios Kepler opted for a geometrical theory of consonance. He argued that consonances could only be constructed by ratios between the number of sides of regular polygons that can be constructed with a ruler and compass. The explication of this takes up the whole of the first book. I’m not going to go into details but interestingly, as part of his rejection of the number seven in his harmonic scheme Kepler goes to great lengths to show that the heptagon construction given by Dürer in his Underweysung der Messung mit dem Zirckel und Richtscheyt is only an approximation and not an exact construction. This shows that Dürer’s book was still being read nearly a hundred years after it was originally published.


In book two Kepler takes up Proclus’ theory that Euclid’s Elements builds systematically towards the construction of the five regular or Platonic solids, which are, in Plato’s philosophy, the elemental building blocks of the cosmos. Along the way in his investigation of the regular and semi-regular polyhedra Kepler delivers the first systematic study of the thirteen semi-regular Archimedean solids as well as discovering the first two star polyhedra. These important mathematical advances don’t seem to have interested Kepler, who is too involved in his revolutionary harmonic theory to notice. In the first two books Kepler displays an encyclopaedic knowledge of the mathematical literature.


The third book is devoted to music theory proper and is Kepler’s contribution to a debate that was raging under music theorist, including Galileo’s father Vincenzo Galilei, about the intervals on the musical scale at the beginning of the seventeenth century. Galilei supported the so-called traditional Pythagorean intonation, whereas Kepler sided with Gioseffo Zarlino who favoured the ‘modern’ just intonation. Although of course Kepler justification for his stance where based on his geometrical arguments. Another later participant in this debate was Marin Mersenne.


In the fourth book Kepler extends his new theory of harmony to, amongst other things, his astrology and his theory of the astrological aspects. Astrological aspects are when two or more planets are positioned on the zodiac or ecliptic at a significant angle to each other, for example 60° or 90°. In his Harmonice, Ptolemaeus, who in the Renaissance was regarded as the prime astrological authority, had already drawn a connection between musical theory and the astrological aspects; here Kepler replaces Ptolemaeus’ theory with his own, which sees the aspects are being derived directly from geometrical constructions. Interestingly Kepler, who had written and published quite extensively on astrology, rejected nearly the whole of traditional Greek astrology as humbug keeping only his theory of the astrological aspects as the only valid form of astrology. Kepler’s theory extended the number of influential aspects from the traditional five to twelve.

The fifth book brings all of the preceding material together in Kepler’s astronomical/cosmological harmonic theory. Kepler examines all of the mathematical aspects of the planetary orbits looking for ratios that fit with his definitions of the musical intervals. He finally has success with the angular velocities of the planets in their orbits at perihelion and aphelion. He then examines the relationships between the tones thus generated by the different planets, constructing musical scales in the process. What he in missing in all of this is a grand unifying concept and this lacuna if filled by his harmonic law, his third law of planetary motion, P12/P22=R13/R23.


There is an appendix, which contains Kepler’s criticisms of part of Ptolemaeus’ Harmonice and Robert Fludd’s harmony theories. I blogged about the latter and the dispute that it triggered in an earlier post

With his book Kepler, who was a devoted Christian, was convinced that he had revealed the construction plan of his geometrical God’s cosmos. His grandiose theory became obsolete within less than fifty years of its publication, ironically pushed into obscurity by intellectual forces largely set into motion by Kepler in his Astronomia nova, his Epitome astronomiae Copernicanae and the Rudolphine Tables. All that has survived of his great project are his mathematical innovations in the first two books and the famous harmonic law. However if readers are prepared to put aside their modern perceptions and prejudices they can follow one of the great Renaissance minds on a fascinating intellectual journey into his vision of the cosmos.

(1) All of the illustration from the Harmonice mundi in this post are taken from the English translation The Harmy of the World by Johannes Kepler, Translated into English with an Introduction and Notes by E.J. Aston, A.M. Duncan and J.V. Field, American Philosophical Society, 1997


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

Christmas Trilogy 2017 Part 2: Charles takes a trip to Turin

Charles Babbage wrote a sort of autobiography, Passages From The Life of a Philosopher.

One of its meandering chapters is devoted to his ideas about and work on his Analytical Engine. In one section he describes explaining to his friend the Irish physicist and mathematician James MacCullagh (1809–1847), who did important work in optics and was awarded the Royal Society’s Copley Medal in 1842,

James MacCullagh artist unknown
Source: Wikimedia Commons

how the Analytical Engine could be fed subroutines to evaluate trigonometrical or logarithmic functions, whilst working on algebraic operations. He goes on to explain that three or four days later Carl Gustav Jacob Jacobi (1804–1851) and Friedrich Wilhelm Bessel (1784–1846), two of Germany’s most important 19th century mathematicians, were visiting and discussing the Analytical Engine when MacCullagh returned and he completed his programming explanation. Which historian of 19th century mathematician wouldn’t give their eyeteeth to listen in on that conversation?

Having dealt with the problem of subroutines for the Analytical Engine Babbage moves on to another of his mathematical acquaintances, he tells us:

In 1840 I received from my friend M. Plana a letter pressing me strongly to visit Turin at the then approaching meeting of Italian Philosophers. In that letter M. Plana stated that he had inquired anxiously of many of my countrymen about the power and mechanism of the Analytical Engine.

Plana was Giovanni Antonio Amedeo Plana (1781–1864) mathematician and astronomer, a pupil of the great Joseph-Louis Lagrange (1736–1813), who was appointed to the chair of astronomy in Turin in 1811.

Giovanni Antonio Amedeo Plana
Source: Wikimedia Commons

Plana worked in many fields but was most famous for his work on the motions of the moon for which he was awarded the Copley Medal in 1834 and the Gold Medal of the Royal Astronomical Society in 1840. The meeting to which he had invited Babbage took place in the Turin Accademia delle Scienze. This august society was founded in 1757 by Count Angelo Saluzzo di Monesiglio, the physician Gianfrancesco Cigna and Joseph-Louis Lagrange as a private society. In 1759 it founded its own journal the Miscellanea philosophico mathematica Societatis privatae Taurinensis still in print today as the Memorie della Accademia delle Scienze. In 1783 having acquired an excellent international reputation it became the Reale Accademia delle Scienze, first as the Academy of Science of the Kingdom of Sardinia and later of the Kingdom of Italy. In 1874 it lost this status to the newly reconstituted Accademia dei Lincei in Rome. It still exists as a private academy today.

Rooms of the Turin Accademia delle Scienze

The meeting to which Babbage had been invited to explain his Analytical Engine was the second congress of Italian scientists. Babbage’s invitation in 1840 was thus recognition of his work at the highest international levels within the scientific community.

Babbage did not need to be asked twice, packed up his plans, drawings and descriptions of the Analytical Engine and accompanied by MacCullagh set of for Turin.

This was not just your usual conference sixty-minute lecture with time for questions. Babbage spent several days ensconced in his apartments in Turin with the elite of the Turin scientific and engineering community. Babbage writes, “M. Plana had at first planned to make notes, in order to write an outline of the principles of the engine. But his own laborious pursuits induced him to give up this plan, and to transfer this task to a younger friend of his, M. Menabrea, who had already established his reputation as a profound analyst.”

Luigi Federico Menabrea (1809–1896) studied at the University of Turin and was an engineer and mathematician. A professional soldier he was professor at both the military academy and at the university in Turin. Later in life he entered politics first as a diplomat and then later as a politician serving as a government minister. He served as prime minister of Italy from 1867 to 1869.

Luigi Federico Menabrea
Source: Wikimedia Commons

After another lengthy explanation of the programming of the Analytical Engine, Babbage writes:

It was during these meetings that my highly valued friend, M. Menabrea, [in reality Babbage had almost certainly never heard of Menabrea before he met him in Turin] collected the materials for that lucid and admirable description which he subsequently published in the Bibli. Uni. de Genève, t. xli. Oct. 1842.

 This is of course the famous document that Ada Lovelace would translate from the original French into English and annotate. Babbage writes of the two documents:

These two memoires taken together furnish, for those who are capable of understanding the reasoning, a complete demonstration—That the whole of the developments and operations of analysis are now capable of being executed by machinery. [emphasis in original]

That he was never able to realise his dreams of the Analytical Engine must have been very bitter for Babbage and now that we can execute the whole of the developments and operations of analysis with machinery, which even a Charles Babbage could not have envisaged in the 19th century, we should take a moment to consider just how extraordinary his vision of an Analytical Engine was.

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Filed under History of Computing, History of Logic, History of Technology

The Trilogies of Christmas Past

For those who started following this blog within the last twelve months and there are quite a lot of you, I write three posts every year as my Christmas Trilogy, although they didn’t acquire this name until 2012. The First on the Christmas Day is for Isaac Newton who was born 25 December 1642 (os). The second on St. Stephen’s or Boxing Day is for Charles Babbage who was born on 26 December 1791. The Trilogy is rounded out by Johannes Kepler who was born on 27 December 1571. If you want to read the earlier posts you can find them here:

Christmas Trilogy 2009 Post 1

Christmas Trilogy 2009 Post 2

Christmas Trilogy 2009 Post 3

Christmas Trilogy 2010 Post 1

Christmas Trilogy 2010 Post 2

Christmas Trilogy 2010 Post 3

Christmas Trilogy 2011 Post 1

Christmas Trilogy 2011 Post 2

Christmas Trilogy 2011 Post 3

Christmas Trilogy 2012 Post 1

Christmas Trilogy 2012 Post 2

Christmas Trilogy 2012 Post 3

Christmas Trilogy 2013 Post 1

Christmas Trilogy 2013 Post 2

Christmas Trilogy 2013 Post 3

Christmas Trilogy 2014 Post 1

Christmas Trilogy 2014 Post 2

Christmas Trilogy 2014 Post 3

Christmas Trilogy 2015 Post 1

Christmas Trilogy 2015 Post 2

Christmas Trilogy 2015 Post 3

Christmas Trilogy 2016 Post 1

Christmas Trilogy 2016 Post 2

Christmas Trilogy 2016 Post 3

Reading that lot should keep you occupied for a couple of hours.

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Christmas Trilogy 2017 Part 1: Isaac the Imperator

Isaac Newton came from a fairly humble although not poor background. His father was a yeoman farmer in Lincolnshire, who unfortunately died before he was born. A yeoman farmer owned his own land and in fact the Newton’s were the occupants of the manor house of Woolsthorpe-by-Colsterworth.

Woolsthorpe Manor, Woolsthorpe-by-Colsterworth, Lincolnshire, England. This house was the birthplace and the family home of Isaac Newton.
Source: Wikimedia Commons

Destined to become a farmer until he displayed little aptitude for life on the land, his mother was persuaded by the local grammar school master to let him complete his education and he was duly dispatched off to Cambridge University in 1661. Although anything but poor, when Newton inherited the family estates they generated an income of £600 per annum, at a time when the Astronomer Royal received an income of £100 per annum, his mother enrolled him at Cambridge as a subsizar, that is a student who earned his tuition by working as a servant. I personally think this reflects the family’s puritan background rather than any meanness on the mother’s part.

In 1664 Newton received a scholarship at Trinity and in 1667 he became a fellow of the college. In 1669 he was appointed Lucasian professor of mathematics. Cambridge was in those days a small market town and a bit of a backwater. The university did not enjoy a good reputation and the Lucasian professorship even less of one. Newton lived in chambers in Trinity College and it was certainly anything but a life of luxury.

Trinity College Great Court
Source: Wikimedia Commons

There is an amusing anecdote about David Hilbert writing to the authorities of Trinity at the beginning of the twentieth century to complain about the fact that Godfrey Hardy, whom he regarded as one of the greatest living mathematicians, was living in what he regarded as a squalid room without running water or adequate heating. What Hilbert didn’t realise was that Hardy would never give up this room because it was the one that Newton had inhabited.

Newton remained an obscure and withdrawn Cambridge don until he presented the Royal Society with his reflecting telescope and published his first paper on optics in 1672. Although it established his reputation, Newton was anything but happy about the negative reactions to his work and withdrew even further into his shell. He only re-emerged in 1687 and then with a real bombshell his Philosophiæ Naturalis Principia Mathematica, which effectively established him overnight as Europe’s leading natural philosopher, even if several of his major competitors rejected his gravitational hypothesis of action at a distance.

Having gained fame as a natural philosopher Newton, seemingly having tired of the provinces, began to crave more worldly recognition and started to petition his friends to help him find some sort of appropriate position in London. His lobbying efforts were rewarded in 1696 when his friend and ex-student, Charles Montagu, 1st Earl of Halifax, had him appointed to the political sinecure, Warden of the Mint.

Newton was no longer a mere university professor but occupant of one of the most important political sinecures in London. He was also a close friend of Charles Montagu one of the most influential political figures in England. By the time Montagu fell from grace Newton was so well established that it had little effect on his own standing. Although Montagu’s political opponents tried to bribe him to give up his, now, Mastership of the Mint he remained steadfast and his fame was such that there was nothing they could do to remove him from office. They wanted to give the post to one of their own. Newton ruled the Mint with an iron hand like a despot and it was not only here that the humble Lincolnshire farm lad had given way to man of a completely different nature.

As a scholar, Newton held court in the fashionable London coffee houses, surrounded by his acolytes, for whom the term Newtonians was originally minted, handing out unpublished manuscripts to the favoured few for their perusal and edification. Here he was king of the roost and all of London’s intellectual society knew it.

He became President of the Royal Society in 1703 and here with time his new personality came to the fore. When he became president the society had for many years been served by absentee presidents, office holders in name only, and the power in the society lay not with the president but with the secretary. When Newton was elected president, Hans Sloane was secretary and had already been so for ten years and he was not about to give up his power to Newton. There then followed a power struggle, mostly behind closed doors, until Newton succeeded in gaining power in about 1610 1710, Sloane, defeated resigned from office in 1613 1713 but got his revenge by being elected president on Newton’s death. Now Newton let himself be almost literally enthroned as ruler of the Royal Society.

Isaac Newton’s portrait as Royal Society President Charles Jervas 1717
Source: Royal Society

The president of the society sat at table on a raised platform and on 20 January 1711 the following Order of the Council was made and read to the members at the next meeting.

That no Body Sit at the Table but the President at the head and the two Secretaries towards the lower end one on the one Side and the other Except Some very Honoured Stranger, at the discretion of the President.

When the society was first given its royal charter in 1660, although Charles II gave them no money he did give them an old royal mace as a symbol of their royal status. Newton established the custom that the mace was only displayed on the table when the president was in the chair. When Sloane became president his first act was to decree that the mace was to be displayed at all meetings, whether the president was present or not. Newton ruled over the meetings with the same iron hand with which he ruled over the Mint. Meeting were conducted solemnly with no chit chat or other disturbances as William Stukeley put it:

Indeed his presence created a natural awe in the assembly; they appear’d truly as a venerable consessus Naturae Consliariorum without any levity or indecorum.

Perhaps Newton’s view of himself in his London years in best reflected in his private habitat. Having lived the life of a bachelor scholar in college chambers for twenty odd years he now obtained a town house in London. He installed his niece Catherine Barton, who became a famous society beauty, as his housekeeper and lived the life of a London gentleman, albeit a fairly quiet one. However his personal furnishings seem to me to speak volumes about how he now viewed himself. When he died an inventory of his personal possessions was made for the purpose of valuation, as part of his testament. On the whole his household goods were ordinary enough with one notable exception. He possessed crimson draperies, a crimson mohair bed with crimson curtains, crimson hangings, a crimson settee. Crimson was the only colour mentioned in the inventory. He lived in an atmosphere of crimson. Crimson is of course the colour of emperors, of kings, of potentates and of cardinals. Did the good Isaac see himself as an imperator in his later life?


All the quotes in this post are taken from Richard S, Westfall’s excellent Newton biography Never at Rest.




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

Happy New Orbit!

Two years ago I wrote a blog post in which I explained why celebrating the end of one and the start of another earth orbit around the sun on the 31 December/1 January was actually totally arbitrary and had no real basis in calendrics or astronomy. I also explained that to merely justify it as traditional is inadequate because the arbitrary day chosen to celebrate has changed several times over the last two millennia. Two millennia is of course a mere fleabite in time compared to the roughly four and a half billion years that the solar system has existed (approx. 0.5×10-6 %). I also pointed out that this New Year’s celebration is only on the Gregorian calendar, and the many other calendars in use in the world celebrate this calendrical renewal on other diverse dates.

I suggested that for those of us in the Northern hemisphere the Winter Solstice would make for a much more rational date to celebrate New Year’s, as it marks the end of our solar journey into the dark, long nights and short days, and the beginning of our solar journey back into the light, long days and short nights. Therefore, as today is Winter Solstice I wish all of my readers Happy New Orbit and thank all of you for having accompanied my throughout the one that ends today.

Stonehenge Winter

The last 365 days were for those of us who live in the so-called western world, to say the least, a fairly bizarre one with the first year of the reign of the Shitgibbon in the White House and the decision on racist and xenophobic grounds by a substantial minority of the population of the UK to commit economic, social and political suicide by leaving the EU. One can only hope that the next cycle of our solar journal proves to be an improvement; I personally have serious doubts.

Those new to this apology for an informative blog might be slightly puzzled by next weeks Christmas Trilogy. Three of my favourite historical figures have their birthdays respectively on 25, 26 and 27 December: Isaac Newton 25 December 1642, Charles Babbage 26 December 1791 and Johannes Kepler 1571. This is of course not strictly accurate as Newton and Kepler are both Julian calendar or old style dates and Babbage is Gregorian calendar or new style. However, in this case, here at Renaissance Mathematicus command centre we ignore such quibbles and honour each gentleman with a blog post on his nominal birthday creating the Renaissance Mathematicus Christmas Trilogy.

So if you need a quiet #histSTM reflective moment over the holidays then you are more than welcome to come here and read your fill.


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Not a student god dammit!

14th December was the anniversary of Tycho Brahe’s birthday and as is now usual on such occasions various people, including me, posted their Tycho scribblings on Twitter, Facebook et. al.

Source: Wikimedia Commons

As is also, unfortunately, usual several of them referred to Johannes Kepler either as Tycho’s pupil or student.

Kepler Memorial at his birthplace Weil der Stadt
Source: Wikimedia Commons

Now, both on Hven and later in Prague, Tycho ran what has been called a large scale research centre employing, over the almost thirty years he collected astronomical data in a systematic programme, a fairly large number of observational assistants. Some of these came to work with the noble Dane as experienced astronomical observers; others came to learn from him. Some of those who came to learn only stayed for a short period and having learnt returned home, some having learnt stayed and worked for a time as assistants. These can justifiably called pupils or students. For example,  Simon Marius, whom I have blogged about on several occasions came to Prague as a student for a few months in 1601, shortly before Tycho’s death, and returned home relatively quickly.

Simon Marius
Source: Wikimedia Commons

The great Dutch cartographer Willem Janszoon Blaeu visited Tycho on Hven for six months in 1595-6 both learning and contributing. He took Tycho’s star catalogue, in the form from a simple celestial globe with him when he left to start his own celestial globe production.

Willem Janszoon Blaeu
Source: Wikimedia Commons

Kepler’s presence in Prague was of a completely different nature. A graduate of the University of Tübingen, he had already worked as a maths teacher and district mathematicus in Graz for six years before he moved to Prague to work with Tycho. He had in 1596 already published his first volume of astronomical speculations, Mysterium Cosmographicum, and it was this that attracted Tycho’s attention in the job seeking German scholar. Kepler’s bizarre cosmological speculations were of less interest to Tycho than Kepler’s very obvious mathematical abilities.

Tycho didn’t take on Kepler as a pupil or student to learn the trade of astronomical observer, for which he would have been fairly useless having suffered from a visual defect since a childhood illness, but as a mathematician to reduce Tycho’s observational data to ephemerides, the practical tables of planetary positions used by cartographers, navigators and astrologers. The production of ephemerides was the principle function of astronomy from antiquity down to the seventeenth century. Tycho didn’t even employ Kepler himself but secured him a position at the court of Rudolph II, employed specifically to produce those ephemerides. Kepler was not Tycho’s pupil or student but his astronomical colleague at court, which is the principle reason why he succeeded him as Imperial Mathematicus. By the way, it took him tweet-six to produce those ephemerides, The Rudolphine Tables, complaining often over the years how tedious the task was. They were, because of their level of accuracies, however the principle reason why people began to accept the heliocentric system over the geocentric and helio-geocentric ones, so it was a well spent twenty-six years.

Monument of Tycho Brahe and Johannes Kepler in Prague
Source: Wikimedia Commons






Filed under History of Astronomy, Myths of Science