Category Archives: History of Optics

An important 13th-century book on optics

The thirteenth-century Silesian friar and mathematician Witelo is one of those shadowy figures in the history of science, whose influence was great but about whom we know very little.


Page from a manuscript of Perspectiva with a miniature of the author Source: Wikimedia Commons

His biography can only be pieced together from scattered comments and references. In his Perspectiva he refers to “our homeland, namely Poland” and mentions Vratizlavia (Wroclaw) and nearby Borek and Liegnitz suggesting that he was born in the area. He also refers to himself as “the son of Thuringians and Poles,” which suggests his father was descended for the Germans of Thuringia who colonized Silesia in the twelfth and thirteenth centuries and his mother was of Polish descent.

A reference to a period spent in Paris and a nighttime brawl that took place in 1253 suggests that he received his undergraduate education there and was probably born in the early 1230s. Another reference indicates that he was a student of canon law in Padua in the 1260s. His Tractatus de primaria causa penitentie et de natura demonum, written in Padua refers to him as “Witelo student of canon law.” In late 1268 or early 1269 he appears in Viterbo, the site of the papal palace. Here he met William of Moerbeke  (c. 1220–c. 1286), papal confessor and translator of philosophical and scientific works from Greek into Latin. Witelo dedicated his Perspectiva to William, which suggest a close relationship. This amounts to the sum total of knowledge about Witelo’s biography.

In the printed editions of the Perspectiva he is referred to as Vitellio or Vitello but on the manuscript copies as Witelo, which is a diminutive form of Wito or Wido a common name in thirteenth century Thuringia, so this is probably his correct name. Family names were uncommon in thirteenth-century Poland, and there is no evidence to suggest that Witelo had one.[1]

Witelo’s principle work, his Perspectiva, was not started before 1270, as he uses William of Moerbeke’ translation of Hero of Alexandria’s Catoptrica, which was only completed on 31stDecember 1269. Witelo is one of three twelfth century authors, along with Roger Bacon (c. 1219–c. 1292) and John Peckham (c. 1230–1292), who popularised and disseminated the optical theories of  Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham, known in Latin as Alhazen or Alhacen. Al-Haytham’s Kitāb al-Manāzir (Book of Optics) was the most important Islamic texts on optics and one of the most important in the whole history of optics. It was translated into Latin by an unknown translator in the late twelfth or early thirteenth century with the title De aspectibus. Bacon was the first European author to include De aspectibus in his various writings on optics and Witelo and Peckham followed his lead. Although it is clear that Witelo used Ptolemy’s Optica, Hero’s Catoptrica and the anonymous De speculis comburentibus in composing his Perspectiva, and that he was aware of Euclid’s Optica, the Pseudo-Euclid Catoptrica and other prominent works on optics, it is very obvious that his major debt is to al-Haytham’s De aspectibus, although he never mentions him by name.

The Perspectiva is a monumental work that runs to nearly five hundred pages in the printed editions. It is divided into ten books:

Book I: Provides the geometric tools necessary to carry out geometrical optics and was actually used as a geometry textbook in the medieval universities.

Book II: Covers the nature of radiation, the propagation of light and colour, and the problem of pinhole images.

Book III: Covers the physiology, psychology, and geometry of monocular and binocular vision by means of rectilinear radiation.

Book IV: Deals with twenty visible intentions other than light and colour, including size, shape, remoteness, corporeity, roughness darkness and beauty. It also deals with errors of perception.

Book V: Considers vision by reflected rays: in plane mirrors

Book VI: in convex spherical mirrors

Book VII: in convex cylindrical and conical mirrors

Book VIII: in concave spherical mirrors

Book IX: in concave cylindrical, conical, and paraboloidal mirrors

Book X: Covers vision by rays refracted at plane or spherical surfaces; it also includes a discussion of the rainbow and other meteorological phenomena.

Witelo’s Perspectiva became a standard textbook for the study of optics and, as already mentioned above, geometry in the European medieval universities; it was used and quoted extensively in university regulations right down to the seventeenth century. The first printed edition of this important optics textbook was edited by Georg Tannstetter (1482–1535) and Peter Apian (1495–1552) and printed and published by Johannes Petreius (c. 1497–1550) in Nürnberg in 1535 under the title Vitellionis Mathematici doctissimi Peri optikēs, id est de natura, ratione & proiectione radiorum visus, luminum, colorum atque formarum, quam vulgo perspectivam vocant.


Georg Tannstetter Portrait ca. 1515, by Bernhard Strigel (1460 – 1528) Source: Wikimedia Commons

Georg Tannstetter born in Rain am Lech in Bavaria had studied at the University of Ingolstadt under Andreas Stiborius (c. 1464–1515) and when Stiborius followed Conrad Celtis (1459–1508) to Vienna in 1497 to become professor for mathematics on the newly established Collegium poetarum et mathematicorum Tannstetter accompanied him. In 1502 he in turn began to lecture on mathematics in Vienna, the start of an illustrious career.


Conrad Celtis: Gedächtnisbild von Hans Burgkmair dem Älteren, 1507 Source: Wikimedia Commons

Peter Apian, possibly his most famous pupil, was born, Peter Bienewitz, in Leisnig. He entered the University of Vienna in 1519 graduating B.A. in 1521. He then moved first to Regensburg and then to Landshut where he began his publishing career with his Cosmographicus liber in 1524.


Apianus on a 16th-century engraving by Theodor de Bry Source: Wikimedia Commons

Following several failed attempts to acquire the position, Apian was appointed printer to the University in Ingolstadt in 1527, as well as lecturer for mathematics, positions he would hold until his death in 1552, when he was succeeded by his son Philipp (1531–1589), who had begun to take over his teaching duties before his death.

Apian’s Ingolstadt printing office continued to produce a steady stream of academic publications, so it comes as somewhat of a surprise that he chose to farm out the printing and publication of his own Instrumentum primi mobilis (1534) and the Tannstetter/Apian edited Witelo Perspectiva (1535) to Johannes Petreius in Nürnberg. Although both books were large and complex it should have been well within Apian’s technical capabilities to print and publish them in his own printing office; in 1540 he printed and published what is almost certainly the most complex science book issued in the sixteenth century, his Astronomicon Caesareum. The problem may have been a financial one, as he consistently had problems getting the university to supply funds to cover the advance cost of printing the books that he published.


Source: Wikimedia Commons

Johannes Petreius, actually Hans Peter, was born in the Lower Franconian village of Langendorf near Hammelburg. He studied at the university in Basel graduating MA in 1517. Here he also learnt the printing trade in the printing office of his uncle Adam Petri (1445–1527). In 1523 he moved to Nürnberg where he set up his own printing business. By the early 1530s, when Apian approached him, he was one of the leading German printer publishers with a good reputation for publishing mathematical works, although his most famous publication Copernicus’ De revolutionibus orbium coelestium still lay in the future. In fact his publishing catalogue viewed as a whole makes him certainly the most important printer publisher of mathematical books in Germany and probably in the whole of Europe in the first half of the sixteenth century. As was his style he produced handsome volumes of both Apian’s Instrumentum and Witelo’s Perspectiva.


Apian’s Instrumentum Title Page Source: Sothebys

Although he died in 1550 the Petreius printing office would issue an unchanged second edition of the Witelo in 1551, which was obviously in preparation before his death. After his death his business ceased as he had no successor and his catalogue passed to his cousin Heinric Petri (1508–1579) in Basel.


Vitellionis Mathematici doctissimi Peri optikēs… title page Source: Christie’s

The Witelo volume would come to play a role in the eventual publication of Copernicus’ magnum opus by Petreius. When Georg Joachim Rheticus (1514-1574) set out in 1539 to seek out Copernicus in Frombork he took with him the Witelo tome as one of six specially-bound-as-a-set books, four of which had been printed and published by Petreius, as a gift for the Ermländer astronomer. The Petreius books were almost certainly meant to demonstrate to Copernicus what Petreius would do with his book if he allowed him to print it. The mission was a success and in 1542 Rheticus returned to Nürnberg with Copernicus’ precious manuscript for Petreius to print and publish in 1543.


Copernicus De revolutionibus title page Source: Wikimedia Commons

There was a third printed edition of Witelo’s Perspectiva printed and published from a different manuscript by Friedrich Risner (1533–1580) together with al-Haytham’s De aspectibus in a single volume in Basel in 1527 under the title, Opticae thesaurus: Alhazeni Arabis libri septem, nuncprimum editi; Eiusdem liber De Crepusculis et nubium ascensionibus, Item Vitellonis Thuringopoloni libri X.


Friedrich Risner edition Opticae Thesaurus (Basel, 1572) Title Page Source

This is the edition that Johannes Kepler (1571–1630) referenced in his Astronomiae pars optica. Ad Vitellionem Paralipomena (The Optical Part of Astronomy: Additions to Witelo) published in Prague in 1604, the most important book on optics since al-Haytham’s.


Astronomiae pars optica. Ad Vitellionem Paralipomena  Source: University of Reading

Witelo remains an obscure thirteenth century scholar but his optics magnum opus cast a shadow down more than four hundred years of European history of optics. [2]

[1]All of the biographical information, and mush else in this article, is taken from David C. Lindberg, Witelo in Complete Dictionary of Scientific Biography, Charles Scribner’s Sons, 2008. Online at

[2]For more on Witelo’s influence on the history of optics see David C. Lindberg, Theories of Vision from al-Kindi to Kepler, University of Chicago Press, Chicago and London, 1976, ppb. 1981.

On Peter Apian as a printer Peter Apian: Astronomie, Kosmographie and Mathematik am Beginn der Neuzeit mit Ausstellungskatalog, ed. Karl Röttel, Polygon-Verlag, Buxheim, Eichstätt, 1995 and Karl Schottenloher, Die Landshunter Buchdrucker des 16. Jahrhundert. Mit einem Anhang: Die Apianusdruckerei in Ingolstadt, Veröffentlichungen der Gutenberg-Gesellschaft XXXI, Mainz, 1930



Filed under Early Scientific Publishing, History of Astronomy, History of Mathematics, History of Optics

Galileo’s the 12th most influential person in Western History – Really?

Somebody, who will remain nameless, drew my attention to a post on the Presidential Politics for America blog shortly before Christmas in order to provoke me. Anybody who knows me and my blogging will instantly recognise why I should feel provoked if they just read the opening paragraph.

Despite the paradigm-shifting idea of our #28 Nicolaus Copernicus, for nearly a century afterward his heliocentric theory twisted in the solar wind. It took another man to confirm Copernicus’s daring theory. That alone would make this other man an all-time great contributor to Western science, but he gifted us so much more than merely confirming someone else’s idea. He had a series of inventions, discoveries, and theories that helped modernize science. His accomplishments in mechanics were without precedent. His telescope observed what was once unobservable. Perhaps most importantly, he embodied, furthered, and inspired a growing sentiment that truth is a slave to science and facts, not authority and dogma.

This man was Galileo Galilei, and he’s the 12thmost influential person in Western History.

Before I start on my usually HistSci_Hulk demolition job to welcome the New Year I should point out that this crap was written by somebody claiming to be a history teacher; I feel for his student.

This post is part of a long-term series on The Top 30 Most Influential Western European Figures in History; I kid you not! Sorry, but I’m not a fan of rankings in general and to attempt to rank the historical influence of Western Europeans is in my opinion foolhardy at best and totally bonkers at worst.

We turn our attention to his #11 Galileo Galilei. We start with the very obvious false claim, the very first one in fact, Galileo did not ‘confirm Copernicus’s daring theory.’ Next up we have the statement: ‘He had a series of inventions, discoveries, and theories that helped modernize science.’

Only in his teens, he identified the tautochronic curve that explains why the pendulum behaves as it does. This discovery laid the groundwork for Christian [sic] Huygens to create the world’s first pendulum clock, which became the most accurate method of keeping time into the twentieth century. 

It is Christiaan not Christian Huygens. Galileo discovered the isochronal principle of the pendulum but the earliest record of his researches on the pendulum is in a letter to his patron Guidobaldo del Monte dated 2 November 1602, when he was 38 years old. The story that he discovered the principle, as a teenager was first propagated posthumously by his first biographer Viviani and to be taken with a pinch of salt. He didn’t discover that the free circular pendulum swing is not isochronal but only the tautochrone curve is; this discovery was actually made by Huygens. There is no evidence that Galileo’s design of a never realised pendulum clock had any connections with or influence on Huygens’ eventually successfully constructed pendulum clock. That pendulum clocks remained the most accurate method of keeping time into the twentieth century is simply wrong.

The precocious Galileo also invented thethermoscope…

 It is not certain that Galileo invented the thermoscope; it is thought that his friend Santorio Santorio actually invented it; he was certainly the first during the Renaissance to publish a description of it. The invention was attributed to Galileo, Santorio, Robert Fludd and Cornelius Drebble. However, the principle on which it was based was used in the Hellenic period and described even earlier by Empedocles in book On Nature in 460 BCE. This is part of a general pattern in the Galileo hagiography, inventions and discoveries that were made by several researchers during his lifetime are attributed solely to Galileo even when he was not even the first to have made them.

At just 22, he published a book onhydrostatic balance, giving him his first bit of fame.

 This ‘book’, La Bilancetta or The Little Balance was actually a booklet or pamphlet and only exists in a few manuscripts so during his lifetime never printed. He used it together with another pamphlet on determining centres of gravity to impress and win patrons within the mathematical community such as Guidobaldo del Monte and Christoph Clavius; in this he was successful.

He attended medical school but, for financial reasons, he had to drop out and work as a tutor. Nevertheless, he eventually became chair of the mathematics department at theUniversity of Pisa.

He studied medicine at the University of Pisa because that was the career that his father had determined for him. He dropped out, not for financial reasons but because he wanted to become a mathematician and not a physician. He studied mathematics privately in Florence and having established his abilities with the pamphlets mentioned above was, with the assistance of his patrons, appointed to teach mathematics in Pisa. However, due to his innate ability to piss people off his contract was terminated after only three years. His patrons now helped him to move to the University of Padua.

He taught at Padua for nearly 20 years, and it’s there where he turned from reasonably well-known Galileo Galilei to Galileo[emphasis in original]. Like the great Italian artists of his age, he became so talented and renowned that soon just his first name sufficed.

This is simply rubbish. He remained virtually unknown outside of Padua until he made his telescopic discoveries in 1610. He turned those discoveries into his exit ticket and left Padua as soon as possible. As for his name, he is, for example, known in English as Galileo but in German as Galilei.

We now turn to mechanics the one field in which Galileo can really claim more than a modicum of originality. However, even here our author drops a major clangour.

Through experimentation, he determined that a feather falls slower than a rock not because of the contrasting weight but because of the extra friction caused by the displacement of Earth’s atmosphere on the flatter object. 

Through experimentation! Where and when did Galileo build his vacuum chamber? Our author missed an opportunity here. This was, of course, Galileo’s most famous thought experiment in which he argues rationally that without air resistance all objects would fall at the same rate. In fact Galileo’s famous use of thought experiments doesn’t make an appearance in this account at all.

Galileo built on this foundation a mathematical formula that showed the rate of acceleration for falling objects on Earth. Tying math to physics, he essentially laid the groundwork for later studies of inertia. These mechanical discoveries provided a firm launching point for Isaac Newton’s further modernization of the field.

It is time for the obligatory statement that the mean speed formula the basis of the mathematics of free fall was known to the Oxford Calculatores and the Paris Physicists in the fourteenth century and also the laws of free fall were already known to Giambattista Benedetti in the sixteenth century. As to inertia, Galileo famously got it wrong and Newton took the law of inertia from Descartes, who in turn had it from Isaac Beeckman and not Galileo. In the late sixteenth and early seventeenth centuries several researchers tied mathematics to physics, many of them before Galileo. See comment above about attributing the work of many solely to Galileo. We now turn to astronomy!

In the early 1600s, despite Copernicus’s elegant heliocentric model of the solar system having debuted more than a half-century earlier, skeptics remained. Indeed, there was an ongoing divide among astronomers; some favored the Copernican model while others clung to the traditional Ptolemaic premise adopted by the Catholic Church, which put the earth at the universe’s center. Even Tycho Brahe, a leading post-Copernican astronomer, favored geocentrism, though his Tychonic system did make some allowances for Copernicus’s less controversial ideas. Brahe’s position helped him avoid the fate of heliocentrist Giordano Bruno who was burned at the stake by the Catholic Inquisition in 1600. This heated astronomical climate awaited Galileo Galilei.

There is nothing particularly elegant about Copernicus’ heliocentric model of the solar system. In fact it’s rather clunky due to his insistence, after removing the equant point, of retaining the so-called Platonic axiom of uniform circular motion. His model was in fact more cluttered and less elegant than the prevailing geocentric model from Peuerbach. Sceptics didn’t remain, as our author puts it, implying in this and the following sentences that there was no reason other than (religious) prejudice for retaining a geocentric model. Unfortunately, as I never tire of repeating, Copernicus’ model suffered from a small blemish, a lack of proof. In fact the vast majority of available empirical evidence supported a geocentric system. You know proof is a fundamental element of all science, including astronomy. If I were playing mythology of science bingo I would now shout full house with the introduction of Giordano Bruno into the mix. No, Giordano was not immolated because he was a supporter of heliocentricity.

Like Bruno, Galileo knew Copernicus was right, and he set out to prove it. Early in the seventeenth century, he received word about a new invention created by the German-Dutch spectacle-makerHans Lippershey In 1608, Lippershey used his knowledge of lenses to make a refracting telescope, which used lenses, an eye piece, and angular strategies to bend light, allowing in more of it. More light could clarify and magnify a desired object, and Lippershey’s rudimentary design could make something appear about three times bigger. Galileo, though he never saw a telescope in person nor even designs of one, heard a basic description of it, checked the information against his brain’s enormous database, realized it could work, and built one of his own. A better one.

Comparing Bruno with Galileo is really something one should avoid doing. Our author’s description of how a refracting telescope works is, I admit, beyond my comprehension, as the function of a refracting telescope is apparently beyond his. The claim that Galileo never saw a telescope, which he made himself, has been undermined by the researches of Mario Biagioli, who argues convincingly that he probably had seen one. I love the expression “checked the information against his brain’s enormous database.” I would describe it not so much as hyperbole as hyperbollocks!

With his improved telescope he could magnify objects thirty times, and he immediately pointed it to the once unknowable heavens and transformed astronomy in numerous ways:

I will start with the general observation that Galileo was by no means the only person pointing a telescope at the heavens in the period between 1609 and 1613, which covers the discoveries described below. He wasn’t even the first that honour goes to Thomas Harriot. Also, all of the discoveries were made independently either at roughly the same time or even earlier than Galileo. If Galileo had never heard of the telescope it would have made virtually no difference to the history of astronomy. He had two things in his favour; he was in general a more accurate observer that his competitors and he published first. Although it should be noted that his principle publication, the Sidereus Nuncius, is more a press release that a scientific report. The first telescope Galileo presented to the world was a 9X magnification and although Galileo did build a 30X magnification telescope most of his discoveries were made with a 20X magnification model. The competitors were using very similar telescopes. “…the once unknowable heavens” we actually already knew quite a lot about the heavens through naked-eye observations.

  • It was assumed that the moon, like all the heavenly spheres, was perfectly smooth. Galileo observed craters and mountains. He inferred, accurately, that all celestial objects had blemishes of their own.

This was actually one of Galileo’s greatest coups. Thomas Harriot, who drew telescopic images of the moon well before Galileo did not realise what he was seeing. After seeing Galileo’s drawings of the moon in the Sidereus Nuncius, he immediately realised that Galileo was right and changed his own drawing immediately. One should, however, be aware of the fact that throughout history there were those who hypothesised that the shadows on the moon were signs of an uneven surface.

  • Though Jupiter had been observed since the ancient world, what Galileo was the first to discover was satellites orbiting around it — the Jovian System. In other words, a planet other than the Earth had stuff orbiting it. It was another brick in Copernicus’s “we’re not that important” wall.

And as I never tire of emphasising, Simon Marius made the same discovery one day later. I have no idea what Copernicus’s “we’re not that important” wall is supposed to be but the discovery of the moons of Jupiter is an invalidation of the principle in Aristotelian cosmology that states that all celestial bodies have a common centre of rotation; a principle that was already violated by the Ptolemaic epicycle-deferent model. It says nothing about the truth or lack of it of either a geocentric or heliocentric model of the cosmos.

  • Pointing his telescope at the sun, Galileo observed sunspots. Though the Chinese first discovered them in 800 BC, as Westerners did five hundred years later, no one had seen or sketched them as clearly as Galileo had. It was another argument against the perfect spheres in our sky.

Telescopic observations of sunspots were first made by Thomas Harriot. The first publication on the discovery was made by Johannes Fabricius. Galileo became embroiled in a meaningless pissing contest with the Jesuit astronomer, Christoph Scheiner, as to who first discovered them. The best sketches of the sunspots were made by Scheiner in his Rosa Ursina sive Sol (Bracciano, 1626–1630).

  • Galileo also discovered that Venus, like the moon, has phases (crescent/quarter/half, waxing/waning, etc.). This was a monumental step in confirming Copernicus’s theory, as Venusian phases require certain angles of sunlight that a geocentric model does not allow.

The phases of Venus were discovered independently by at least four observers, Thomas Harriot, Simon Marius, Galileo and the Jesuit astronomer Paolo Lembo. The astronomers of the Collegio Romano claimed that Lembo had discovered them before Galileo but dating the discoveries is almost impossible. In a geocentric model Venus would also have phases but they would be different to the ones observed, which confirmed that Venus, and by analogy Mercury, whose phases were only observed much later, orbits the Sun. Although this discovery refutes a pure geocentric system it is still compatible with a Capellan system, in which Venus and Mercury orbit the Sun in a geocentric model, which was very popular in the Middle ages and also with any of the Tychonic and semi-Tychonic models in circulation at the time so it doesn’t really confirm a heliocentric model

  • The observable hub of the Milky Way galaxy was assumed to be, just as it looks to us, a big, milky cloud. Galileo discovered it was not a cloud, but a huge cluster of stars. (We now know it numbers in the billions.)

Once again a multiple discovery made by everybody who pointed a telescope at the heavens beginning with Lipperhey.

Galileo not only confirmed Copernicus’s heliocentric theory, but he allowed the likes of Johannes Kepler to more accurately plot out the planets’ orbits, Isaac Newton to explain how it was happening, and Albert Einstein to explain why. It was such a colossal step forward for the observable universe that some people didn’t even believe what they were seeing in the telescope, electing to instead remain skeptical of Galileo’s “sorcery.”

Galileo did not in any way confirm Copernicus’ heliocentric theory. In fact heliocentricity wasn’t confirmed until the eighteenth century. First with Bradley’s discovery of stellar aberration in 1725 proving the annual orbit around the sun and then the determination of the earth’s shape in the middle of the century indirectly confirming diurnal rotation. The telescopic observations made by Galileo et al had absolutely nothing to do with Kepler’s determination of the planetary orbits. Newton’s work was based principally on Kepler’s elliptical system regarded as a competitor to Copernicus’ system, which Galileo rejected/ignored, and neither Galileo nor Copernicus played a significant role in it. How Albert got in here I have absolutely no idea. Given the very poor quality of the lenses used at the beginning of the seventeenth century and the number of optical artifacts that the early telescopes produced, people were more than justified in remaining skeptical about the things apparently seen in telescopes.

Ever the watchdog on sorcery, it was time for the Catholic Church to guard its territory. Protective of geocentrism and its right to teach us about the heavens, the Church had some suggestions about exactly where the astronomer could stick his telescope. In 1616, under the leadership of Pope Paul V, heliocentrism was deemed officially heretical, and Galileo was instructed “henceforth not to hold, teach, or defend it in any way.”

The wording of this paragraph clearly states the author’s prejudices without consideration of historical accuracy. Galileo got into trouble in 1615/16 for telling the Catholic Church how to interpret the Bible, a definitive mistake in the middle of the Counter Reformation. Heliocentrism was never deemed officially heretical. The injunction against Galileo referred only to heliocentrism as a doctrine i.e. a true theory. He and everybody else were free to discuss it as a hypothesis, which many astronomers preceded proceeded to do.

A few years later, a confusing stretch of papal leadership got Galileo into some trouble. In 1623,Pope Urban VIII took a shine to Galileo and encouraged his studies by lifting Pope Paul’s ban. A grateful Galileo resumed his observations and collected them into his largest work, 1632’s “Dialogue Concerning the Two Chief World Systems” In it, he sums up much of his observations and shows the superiority of the newer heliocentric model. The following year, almost as if a trap were set, the Catholic Inquisition responded with a formal condemnation and trial, charging him with violating the initial 1616 decree. Dialogue was placed on the Church’s Index of Prohibited Books.

Maffeo Barberini, Pope Urban VIII, had been a good friend of Galileo’s since he first emerged into the limelight in 1611 and after he was elected Pope did indeed show great favour to Galileo. He didn’t, however, lift Paul V’s ban. It appears that he gave Galileo permission to write a book presenting the geocentric and heliocentric systems, as long as he gave them equal weight. This he very obviously did not do; Galileo the master of polemic skewed his work very, very heavily in favour of the heliocentric system. He had badly overstepped the mark and got hammered for it.  He, by the way, didn’t resume his observations; the Dialogo is based entirely on earlier work. One is, by the way, condemn after being found guilty in a trial not before the trial takes place when one is charged or accused.

Galileo’s popularity, combined with a sheepish Pope Urban, limited his punishment to a public retraction and house arrest for his remaining days. At nearly 70, he didn’t have the strength to resist. Old, tired, and losing his vision after years of repeatedly pointing a telescope at the brightest object in the solar system, he accepted his sentence. Blind and condemned, his final years were mostly spent dictating “Two New Sciences,” which summarized his 30 years of studying physics.

Galileo’s popularity would not have helped him, exactly the opposite. People who were highly popular and angered the Church tended to get stamped on extra hard, as an example to the masses. Also, Urban was anything but sheepish. The public retraction was standard procedure for anyone found guilty by the Inquisition and the transmission of his sentence from life imprisonment to house arrest was an act of mercy to an old man by an old friend. Whether Galileo’s telescopic observations contributed to his blindness is disputed and he hadn’t really made many observations since about 1613. The work summarised in the Discorsi was mostly carried out in the middle period of his life between 1589 and 1616.

The author now veers off into a discussion, as to who is the father or founder of this or that and why one or other title belongs to Copernicus, Newton, Aristotle, Bacon etc. rather than Galileo. Given his belief that one can rank The Top 30 Most Influential Western European Figures in History, it doesn’t surprise me that he is a fan of founder and father of titles. They are, as regular readers will already know, in my opinion a load of old cobblers. Disciplines or sub-disciplines are founded or fathered over several generations by groups of researchers not individuals.

His article closes with a piece of hagiographical pathos:

Moreover, Galileo’s successes were symbolic of a cornerstone in modern science. His struggle against the Church embodied the argument that truth comes from experience, experiments, and the facts — not dogma. He showed us authority and knowledge are not interchangeable. Though the Inquisitors silenced him in 1633, his discoveries, works, and ideas outlived them. For centuries, he has stood as an inspiration for free thinkers wrestling against ignorant authority.

This is typical exaggerated presentation of the shabby little episode that is Galileo’s conflict with the Catholic Church. It wasn’t really like that you know. Here we have the heroic struggle of scientific truth versus religious dogma, a wonderful vision but basically pure bullshit. What actually took place was that a researcher with an oversized ego, Galileo, thought he could take the piss out of the Pope and the Catholic Church. As it turned out he was mistaken.

Being a history teacher I’m sure our author would want me to grade his endeavours. He has obviously put a lot of work into his piece so I will give him an E for effort. However, it is so strewn with errors and falsities that I can only give him a F for the content.

























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

Christmas Trilogy 2018 Part 1: The Harmonic Isaac

Isaac Newton is often referred to, as the ‘father’ of modern science but then again so is Galileo Galilei. In reality modern science has many fathers and some mothers as well. Those who use this accolade tend to want to sweep his theological studies and his alchemy under the carpet and pretend it doesn’t really count. Another weird aspect of Newton’s intellectual universe was his belief in prisca theology. This was the belief that in the period following the creation humankind had perfect knowledge of the natural world that got somehow lost over the centuries. This meant for Isaac that in his own scientific work he wasn’t making discoveries but rediscovering once lost knowledge. Amongst, what we would now regard as his occult beliefs, Isaac also subscribed to the Pythagorean belief in Harmonia (harmony), as a unifying concept in the cosmos.


Robert Fludd’s Pythagorean Monocord

Although he was anything but a fan of music, he was a dedicated student of Harmonia, the mathematical theory of proportions that was part of the quadrivium. According to the legend Pythagoras was the first to discover that musical interval can be expressed as simple ratios of whole numbers related to a taut string: 1:1 (unison), 2:1 (octave), 3:2 (perfect fifth), 4:3 (perfect fourth), 5:4 (major third), 6:5 (minor third). Unfortunately, anybody who has studied the theory of music knows these ratios don’t quite work. If you start on a given tone and move up in steps of a perfect fifth you don’t actually arrive back at the original tone seven octaves higher after twelve fifths but slightly off. This difference is known as the Pythagorean comma. This disharmony was well known and in the sixteenth and seventeenth centuries a major debate developed on how to ‘correctly’ divide up musical scale to avoid this problem. The original adversaries were Gioseffo Zarlino (1570–1590) and Vincenzo Galilei (1520–1591) (Galileo’s father) and Kepler made a contribution in his Harmonice Mundi; perhaps the most important contribution being made by Marin Mersenne (1588–1648) in his Harmonie universelle, contenant la théorie et la pratique de la musique.


Harmonie Universelle title page

Here he elucidated Mersenne’s Laws:

Frequency is:

  1. Inversely proportional to the length of the string (this was known to the ancients; it is usually credited toPythagoras)
  2. Proportional to the square root of the stretching force, and
  3. Inversely proportional to the square root of the mass per unit length.

Source: Gouk p. 115

As a student Newton took up the challenge in one of his notebooks and we don’t need to go into his contribution to that debate here, however it is the first indication of his interest in this mathematics, which he would go on to apply to his two major scientific works, his optics and his theory of gravity.

After he graduated at Cambridge Newton’s first serious original research was into various aspects of optics. This led to his first published paper:

A Letter of Mr. Isaac Newton, Professor of the Mathematicks in the University of Cambridge; Containing His New Theory about Light and Colors: Sent by the Author to the Publishee from Cambridge, Febr. 6. 1671/72; In Order to be Communicated to the R. Society

In which he described his experiments with a prism that showed that white light consists of blended coloured light and that the spectrum that one produces with a prism is the splitting up of the white light into its coloured components. Previous theories had claimed that the spectrum was produced by the dimming or dirtying of the white light by the prism. Newton wrote an extensive paper expanding on his optical research, An hypothesis explaining the properties of light, but due to the harsh criticism his first paper received he withheld it from publication. This expanded work only appeared in 1704 in his book, Opticks: A Treatise of the Reflections, Refractions, Inflections & Colours of Light. Here we can read:

In the Experiments of the fourth Proposition of the first Part of this first Book, when I had separated the heterogeneous Rays from one another, the Spectrum ptformed by the separated Rays, did in the Progress from its End p, on which the most refrangible Rays fell, unto its other End t, on which the most refrangible Rays fell, appear tinged with this Series of Colours, violet, indigo, blue, green, yellow, orange, red, together with all their intermediate Degrees in a continual Succession perpetually varying . So that there appeared as many Degrees of Colours, as there were sorts of Rays differing in Refrangibility.

This is of course the list of seven colours that we associate with the rainbow today. Before Newton researchers writing about the spectrum listed only three, four or at most five colours, so why did he raise the number to seven by dividing the blue end of the spectrum into violet, indigo and blue? He did so in order to align the number of colours of the spectrum with the notes on the musical scales. In the Queries that were added at the end of the Opticks over the years and the different editions we find the following:

Qu. 13. Do not several sorts of Rays make Vibrations of several bigness, which according to their bignesses excite Sensations of several Colours, much after the manner that the Vibrations of the Air, according to their several bignesses excite Sensations of several Sounds? And particularly do not Vibrations for making a Sensation of deep violet, the least refrangible the largest for making a Sensation of deep red, and several intermediate sorts of Rays, Vibrations of several intermediate bignesses to make Sensations of the several intermediate Colours?

Qu. 14. May not the harmony and discord of Colours arise from the proportions of the Vibrations propagated through the Fibres of the optick Nerves into the Brain, as the harmony and discord of Sounds arise from the proportions of the Vibrations of the Air? And some Colours, if they be view’d together, are agreeable to one another, as those of Gold and Indigo and other disagree.

In the An Hypothesis, Newton published a diagram illustrated the connection he believed to exist between the colours of the spectrum and the notes of the scale.


Source: Gouk p. 118

Interestingly Voltaire presented Newton’s theory in his Elemens de la philosophie de Newton (1738), again as a diagram.


Source: Gouk p. 119

Turning now to Newton’s magnum opus we find the even more extraordinary association between his theory of gravity and the Pythagorean theory of harmony. Newton’s Law of Gravity is probably the last place one would expect to meet with Pythagorean harmony but against all expectations one does. In unpublished scholia on Proposition VIII of Book III of the Principia(the law of gravity) Newton claimed that Pythagoras had known the inverse square law. He argued that Pythagoras had discovered the inverse-square relationship in the vibration of strings (see Mersenne above) and had applied the same principle to the heavens.

…consequently by comparing those weights with the weights of the planets , and the lengths of the strings with the distances of the planets, he understood by means of the harmony of the heavens that the weights of the planets towards the Sun were reciprocally as the squares of their distances from the Sun.[1]

Although Newton never published this theory David Gregory (1661–1708) did. David Gregory was a nephew of the physicist James Gregory who in 1684 became professor of mathematics at the University of Edinburgh, where he became “the first to openly teach the doctrines of the Principia, in a public seminary…in those days this was a daring innovation.”[2]


Davis Gregory bust Source: Wikimedia Commons

In 1691, with Newton’s assistance, he was appointed Savilian Professor of Astronomy at Oxford going on to become an important mathematician, physicist and astronomer. He worked together with Newton on the planned second edition of the Principia, although he did not edit it, dying in 1708; the second edition appearing first in 1713 edited by Richard Bentley. In his Astronomiae physicae et geometricae elementa, a semi-popular presentation of Newton’s theories first published in Latin in 1702


Gregory wrote the following:

The Elements of Astronomy, Physical and Geometrical By David Gregory M.D. SavilianProfessor of Astronomy at Oxfordand Fellow of the Royal Society (1615)

The Author’sPreface

As it is manifest that the Ancients were apprized of, and had discover’d the Gravity of all Bodies towards one another, so also they were not unacquainted with the Law and Proportion which the action of Gravity observ’d according to the different Masses and Distances. For that Gravity is proportional to the Quantity of Matter in the heavy Body, Lucretiusdoes sufficiently declare, as also that what we call light Bodies, don’t ascend of their own accord, but by action of a force underneath them, impelling them upwards, just as a piece of Wood is in Water; and further, that all Bodies, as well the heavy as the light, do descend in vacuo, with an equal celerity. It will be plain likewise, from what I shall presently observe, that the famous Theorem about the proportion whereby Gravity decreases in receding from the Sun, was not unknown at least to Pythagoras. This indeed seems to be that which he and his followers would signify to us by the Harmony of the Spheres: That is, they feign’d Apolloplaying on a Harp of seven Strings, by which Symbol, as it is abundantly evident from Pliny, Macrobiusand Censorinus, they meant the Sun in Conjunction with the seven planets, for they made him the leader of that Septenary Chorus, and Moderator of Nature; and thought that by his Attractive force he acted upon the Planets (and called it Jupiter’s Prison, because it is by this Force that he retains and keeps them in their Orbits, from flying off in Right Lines) in the Harmonical ration of their Distances. For the forces, whereby equal Tensions act upon Strings of different lengths (being equal in other respects) are reciprocally as the Squares of the lengths of the Strings.

I first came across this theory, as elucidated by Gregory, years ago in a book, which book I have in the meantime forgotten, where it was summarised as follows:

Gravity is the strings upon which the celestial harmony is played.









[1]Quoted from Penelope Gouk, The harmonic roots of Newtonian science, in John Fauvel, Raymond Flood, Michael Shortland & Robin Wilson eds., Let Newton Be: A new perspective on his life and works, OUP, Oxford, New York, Tokyo, ppb. 1989 The inspiration and principle source for this blog post.

[2]Quoted from Significant Scots: David Gregory



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

The Jesuit Mirror Man

Although the theory that a curved mirror can focus an image was already known to Hero of Alexandria in antiquity and also discussed by Leonardo in his unpublished writings; as far as we know, the first person to attempt to construct a reflecting telescope was the Italian Jesuit Niccolò Zucchi.


Niccolò Zucchi Source: Wikimedia Commons

Niccolò Zucchi, born in Parma 6 December 1586, was the fourth of eight children of the aristocrat Pierre Zucchi and his wife Francoise Giande Marie. He studied rhetoric in Piacenza and philosophy and theology in Parma, probably in Jesuit colleges. He entered the Jesuit order as a novice 28 October 1602, aged 16. Zucchi taught mathematics, rhetoric and theology at the Collegio Romano and was then appointed rector of the new Jesuit College in Ravenna by Cardinal Alessandro Orsini, who was also a patron of Galileo.

In 1623 he accompanied Orsini, the Papal legate, on a visit to the court of the Holy Roman Emperor Ferdinand II in Vienna. Here he met and got to know Johannes Kepler the Imperial Mathematicus. Kepler encouraged Zucchi’s interest in astronomy and the two corresponded after Zucchi’s return to Italy. Later when Kepler complained about his financial situation, Zucchi sent him a refracting telescope at the suggestion of Paul Guldin (1577–1643) a Swiss Jesuit mathematician, who also corresponded regularly with Kepler. Kepler mentions this gift in his Somnium. These correspondences between Kepler and leading Jesuit mathematicians illustrate very clearly how the scientific scholars in the early seventeenth century cooperated with each other across the religious divide, even at the height of the Counter Reformation.

Zucchi’s scientific interests extended beyond astronomy; he wrote and published two books on the philosophy of machines in 1646 and 1649. His unpublished Optica statica has not survived. He also wrote about magnetism, barometers, where he a good Thomist rejected the existence of a vacuum, and was the first to demonstrate that phosphors generate rather than store light.

Today, however Zucchi is best remember for his astronomy. He is credited with being the first, together with the Jesuit Daniello Bartoli (1608–1685), to observe the belts of Jupiter on 17 May 1630.  He reported observing spots on Mars in 1640. These observations were made with a regular Galilean refractor but it is his attempt to construct a reflecting telescope that is most fascinating.

In his Optica philosophia experimentis et ratione a fundamentis constituta published in 1652 he describes his attempt to create a reflecting telescope.


Optica philosophia title page Source: Linder Hall Library

As I said at the beginning, and have described in greater detail here, the principle that one could create an image with a curved mirror had been known since antiquity. Zucchi tells us that he replaced the convex objective lens in a Galilean telescope with bronze curved mirror. He tried viewing the image with the eyepiece, a concave lens looking down the tube into the mirror. He had to tilt the tube so as not to obstruct the light with his head. He was very disappointed with the result as the image was just a blur, although as he said the mirror was, “ab experto et accuratissimo artifice eleboratum nactus.” Or in simple words, the mirror was very well made by an expert.


Optica philosophia frontispiece

Zucchi had stumbled on a problem that was to bedevil all the early attempts to construct a reflecting telescope. Mirror that don’t distort the image are much harder to grind and polish than lenses. (The bending of light in a lens diminishes the effect of imperfections, whereas a mirror amplifies them). The first to solve this problem was Isaac Newton, proving that he was as skilled a craftsman as he was a great thinker. However, it would be more that fifty years before John Hadley could consistently repeat Newton’s initial success.

All the later reflecting telescope models had, as well as their primary mirrors, a secondary mirror at the focal point that reflected the image either to the side (a Newtonian), or back through the primary mirror (a Gregorian or a Cassegrain) to the eyepiece; the Zucchi remained the only single mirror telescope in the seventeenth century.

In the eighteenth century William Herschel initially built and used Newtonians but later he constructed two massive reflecting telescopes, first a twenty-foot and then a second forty-foot instrument.


Herschel’s Grand Forty feet Reflecting Telescopes A hand-coloured illustration of William Herschel’s massive reflecting telescope with a focal length of forty feet, which was erected at his home in Slough. Completed in 1789, the telescope became a local tourist attraction and was even featured on Ordnance Survey maps. By 1840, however, it was no longer used and was dismantled, although part of it is now on display at the Royal Observatory, Greenwich. This image of the telescope was engraved for the Encyclopedia Londinensis in 1819 as part of its treatment of optics. Herschel’s Grand Forty feet Reflecting Telescopes Source: Wikimedia Commons

These like Zucchi’s instrument only had a primary mirror with Herschel viewing the image with a hand held eyepiece from the front of the tube. As we name telescopes after their initial inventors Herschel giant telescopes are Zucchis, although I very much doubt if he even knew of the existence of his Jesuit predecessor, who had died at the grand old age of eighty-three in 1670.



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

The telescope – claims and counterclaims

Sometime between the 25thand 29thof September 410 years ago Hans Lipperhey, a spectacle maker from Middelburg in Zeeland, gave the earliest known public demonstration of the telescope to Maurits of Nausau and assembled company at a peace conference in Den Hague.


Source: Wikimedia Commons

His demonstration was recorded in a 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 demonstration.

A few days before the departure of Spinola from The Hague a spectacle-maker from Middelburg, a humble man, very religious & pious, offered His Excellency certain glasses as a present, by which one is able to trace & observe clearly objects at a distance of three or four miles, as if there is a distance as little as one hundred footsteps. From the tower of The Hague with the said glasses one can observe clearly the clock on the tower of Delft, & the windows of the Church of Leiden, despite the fact that one of the said towns is at a distance of one & a half hours and the other one at three and a half hours walking distance. The States-General were already well informed about this and sent them to His Excellency to show, adding that with these glasses one could observe the impostures of the enemy. Spinola also saw them with great astonishment & told Prince Hendrik; from this moment on I will not be safe anymore, because you can observe me from afar. Whereupon the said Prince answered: we will prohibit our people to shoot at you. The craftsman who has manufactured the said glasses has received three hundred écu & he will receive more on condition that he will tell nobody about the said proficiency, which he promised with most pleasure as he doesn’t want the enemy will be able to use this, The said glasses are very useful at sieges & in similar affairs, because one can distinguish from a mile’s distance & beyond several objects very well, as if they are very near & 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.[1]

This was not however the first written account of Lipperhey’s new invention. The Councillors of Zeeland had given him a letter of introduction, dated 25 September, to the States-General in Den Hague, it begins:

The bearer of this, who claims to have a certain device, by means of which all things at a great distance can be seen as if they were nearby, by looking through glasses which he claims to be a new invention, would like to communicate the same to His Excellency [Prince Maurits]. Your Honour will please recommend him to His Excellency, and, as the occasion arises, be helpful to him according to what you think of the device…[2]

On 2 October 1608, Lipperhey submitted an application for a patent for his device to the States-General, from here on things, which had looked so promising for our humble spectacle-maker from Middelburg started to turn decidedly pear shaped.


Hans Lipperhey’s unsuccessfully patent request Source: Wikimedia Commons

On 14 October 1608, an, until now, unidentified young man offered to sell a telescope to the Councillors of Zeeland, who dutifully informed the States-General of this new development. On 15 October the States-General received a letter from Jacob Adriaenszoon (after 1571–1628) called Metius, a spectacle-maker from Alkmaar also requesting a patent for his instrument on which he had been working for two years and which, so he claimed, was a least as good as the instrument from Middelburg. Given these developments, telescopes were apparently available on every street corner, the States-General denied Lipperhey his desired patent but they did commission him to make six pairs of binoculars for a total of 900 guilders, a very large sum. Interestingly they demanded that the lenses be made of rock crystal rather than glass, because of the poor quality of the glass lenses, something that would remain a problem for telescope makers throughout the seventeenth century.

The problem with who actually invented the telescope does not end there. In his Mundus Jovialis, published in 1614, Simon Marius, one of the earliest telescopic astronomers, recounts how his patron Johan Philip Fuchs von Bimbach was offered a telescope at the Autumn Frankfurt Fair in 1608.


Engraved image of Simon Marius (1573-1624), from his book Mundus Iovialis, 1614 Source: Houghton Library via Wikimedia Commons

He didn’t purchase the proffered instrument because one of the lenses was cracked and the asking price was apparently too high. In many accounts of the invention of the telescope, this story is used as an illustration of how fast the new invention spread after Lipperhey’s unveiling in Den Hague. However, there is a major problem here; the Autumn Fair in Frankfurt in 1608 took place before Lipperhey’s demonstration. We have yet another unclear source for the ‘first telescope’.


Hans Philipp Fuchs von Bimbach Source: Wikimedia Commons

Up till 2008 it had become common practice to claim that the seller in Frankfurt and the unknown young man in Middelburg were one and the same and identified as Zacharias Janssen (1585-pre. 1632) and that he and not Lipperhey was the true inventor of the telescope and for good measure also the microscope.  How this all came about is almost Byzantine.


Zacharias Janssen Source: Wikimedia Commons

In 1655, the French scholar Pierre Borel (c. 1620–1671) published the first full history of the invention of the telescope, De vero telescopii inventore.


De vero telescopii inventore 1665 Title page Source

In his book he followed the account of the Dutch Ambassador to France, Willem Boreel (1591–1668). Born in Middelburg, Boreel had memories of having met the inventor of the telescope in 1610. Not sure of his memory forty-five years later he wrote to a local magistrate in Middelburg to investigate the matter. The magistrate interviewed a then unknown spectacle-maker Johannes Zachariassen, the son of Zacharias Janssen. Johannes claimed that his father and his grandfather had invented the microscope and telescope in 1590. Johannes would also tell a similar story to Isaac Beeckman, when he was teaching him lens grinding, also claiming that he and his father had also invented the long, i.e. astronomical, telescope in 1618. Boreel confirmed Johannes account as agreeing with his memories and Borel’s account that Zacharias Janssen and not Hans Lipperhey was the true inventor of the telescope.


Portrait of Pierre Borel by Jacques Pauthe Source: Wikimedia Commons

The last of Johannes’ claims is easily disposed of because it was Johannes Kepler, who first described the astronomical telescope in his Dioptrice in 1611. As to the other claim in 1590 Johannes’ grandfather was already dead and his father Zacharias was a mere four or five years old. These objections were simply swept aside over the years and Janssen’s invention simply moved forward to 1604 another date claimed by Johannes. However modern research by Huib Zuidervaart into the life of Zacharias Janssen have shown the first contact that he had with lens grinding or spectacle-making was when he became guardian the children of another spectacle-maker ‘Lowys Lowyssen, geseyt Henricxen brilmakers’. There is no other evidence that Zacharias was ever a spectacle-maker.[3]

The unknown youth in Middelburg and the telescope seller in Frankfurt remain unknown and probably forever unknowable.

News of the wonderful new invention spread really fast throughout Europe with telescopes on sale as novelties in Paris by the early summer 1609. The enthusiasm with which the new invention was greeted and the speed with which it spread throughout Europe rather puts the lie to all the competing theories that the telescope was already invented by (insert your favourite candidate) at some date before Lipperhey’s first demonstration. If it had been, we would certainly have heard about it. As far as we know, the first astronomer to make observations with the new instrument was Thomas Harriot, who drew a sketch of the moon observed with a six-power telescope dated 26 July 1609 os (5 August ns).


Harriot’s sketch of the moon 1609

Following on to his encounter with a telescope at the Frankfurt Fair, Fuchs von Bimbach together with Simon Marius obtained, with some difficulty, suitable lenses and the two of them constructed their own telescope. Simon Marius began his own astronomical observations sometime also in 1609. Galileo Galilei heard of the telescope through his friend Paolo Sarpi and it is now thought that his claim that he devised the construction of his telescope purely on the basis of having heard of it is not true and that he had in fact seen and handled a telescope before he began his own efforts at construction.


Galileo Galilei. Portrait by Ottavio Leoni Marucelliana Source: Wikimedia Commons

Galilei/ Fernrohre / Aufnahme

Galileo’s telescopes Source: Wikimedia Commons

Galileo, ever on the look out to make a quick buck and further his career, first marketed ‘his invention’ to the civil authorities, demonstrating a six-power telescope to the aristocrats of Venice 21 August 1609. On the 24thof the month he presented said telescope formally to the Doge and Senate of Venice. The following day the authorities granted him a lifetime contract as professor of mathematics at the university with the extraordinary salary of 1,000 florins p.a. with however the condition that he would never receive another pay rise. The Senate was apparently more than somewhat miffed when they discovered that the telescope was not the invention of their talented mathematics professor but was readily available on every street corner in Europe to knockdown prices. Galileo repaid their generosity by beginning plans to leave Venice and return to Florence.

We don’t know for certain when Galileo began his astronomical observations but we do know that he was an exceptionally talented observer and was soon viewing the skies on clear nights with a twenty-power instrument of his own construction. On 7 January 1610 he knew he had hit the jackpot when he first observed three of the moons of Jupiter. Simon Marius made the same discovery one day later on 8 January. More accurately he realised he had hit the jackpot only a couple of days later when it became clear that what he had discovered were satellites and not fixed stars. Marius waited four years before he published his discovery, Galileo didn’t! He immediately changed from Italian to Latin in his observing blog log and began making plans to publish his telescopic observation before he could be beaten to the gun by some unknown rival.

He decided to dedicate his planned publication to Cosimo II De’ Medici Fourth Grand Duke of Tuscany and started negotiations with the Tuscan Court over which names/names they would prefer for the newly discovered moons. In the end the term Medicean Stars was decided upon and Galileo’s Sidereus Nuncius was published with a preface dated forth day before the Ides of March 1610, that’s 12 March in modern money.


Title page of Sidereus nuncius, 1610, by Galileo Galilei (1564-1642). *IC6.G1333.610s, Houghton Library, Harvard University Source: Wikimedia Commons

Seldom has a book hit the streets with such an impact. It truly marks the beginning of a new epoch in the history of astronomy and a new phase in the life of its author. Galileo got what he was angling for, he was appointed court mathematicus and philosophicus to the court in Florence and given a professorship at the university without teaching obligations but with a salary of 1,000 florins p.a.

The very poor quality of the glass available to make lenses and the errors in grinding and polishing made it very difficult for observers to see anything at all through the early telescopes, a problem that would continue to plague telescope users throughout the seventeenth century. There were as many claims made for discoveries that didn’t exist as for real ones.  All of this made it difficult for others to confirm Galileo’s spectacular claims. In the end the Jesuit astronomers of the Collegio Romano in Rome were able with much effort and many setbacks to confirm all of his discoveries. In 1611 he made a triumphant tour of Rome, which included a celebration banquet put on by the Jesuits at the Collegio. At a second banquet put on by Prince Frederico Cesi, founder and President of the Accademia dei Lincae of which Galileo would become a member, the telescope first received its name, in Greek teleskopos.

Another central problem in the first months of telescopic astronomical observation was that there existed no scientific explanation of how or why the telescope functions. This allowed critics to reject the discoveries as imaginary artefacts produced by the instrument itself. The man who came to the rescue was Johannes Kepler. 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.


Source: Wikimedia Common


In 1611 Kepler published his very quickly written Diotrice, 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

One small footnote to the whole who–invented–what story is that Kepler attributed the invention of the telescope to Giambattista della Porta (1535?–1615).


Giambattista della Porta Source: Wikimedia Commons

Della Porta did indeed describe the magnifying effect of the lens combination of the Dutch telescope in his Magiae Naturalis(various editions 1558 to 1589).

With a concave you shall see small things afar off, very clearly; with a convex, things neerer to be greater, but more obscurely: if you know how to fit them both together, you shall see both things afar off, and things neer hand, both greater and clearly.

He provided a primitive sketch in a letter to Prince Cesi in 1609.

Della Porta Telescope Sketch

Kepler assumed that the Dutch spectacle-maker, he didn’t know Lipperhey’s name, had somehow learnt of della Porta’s idea and put it into practice. It is more probable that della Porta was actually describing some sort of compound magnifying glass rather than a telescope and that Lipperhey had no idea of della Porta’s work.

Despite the confusion that surrounds the origins of the telescope, today most historians attribute the honours to Hans Lipperhey, whose demonstration set the ball rolling. We have come a long way since Lipperhey demonstrated his simple invention to Prince Maurits in Den Hague. I don’t suppose the humble spectacle–maker from Middelburg could have conceived the revolution in astronomy he set in motion on that day four hundred and ten years ago.

[1]Embassies of the King of Siam Sent to His Excellency Prince Maurits Arrived in The Hague on 10 September 1608,Transcribed from the French original, translated intoEnglish and Dutch, introduced by Henk Zoomers and edited by Huib Zuidervaart after a copy in the Louwman Collection of Historic Telescopes, Wassenaar, 2008 pp. 48-49 (original pagination: 9-11)

[2]Taken from Fred Watson, Stargazer: the life and times of the Telescope, Da Capo Press, Cambridge MA, 2005

[3]For more details of the Dutch story of the invention of the telescope see Huib J. Zuidervaart, The ‘true inventor’ of the telescope. A survey of 400 years of debate, in The origins of the telescope, ed. Albert van Helden, Sven Dupré, Rob van Gent, Huib Zuidervaart, KNAW Press, Amsterdam, 2010


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

Today in something is wrong on the Internet

When I was growing up one of the most widespread #histSTM myths, along with the claim that people in the Middle Ages believed the world was flat and Stone Age people lived in holes in the ground, was that Galileo Galilei invented the telescope. This myth actually has an interesting history that goes all the way back to the publication of the Sidereus Nuncius. Some of Galileo’s critics misinterpreting what he had written asserted that he was claiming to have invented the telescope, an assertion that Galileo strongly denied in a latter publication. Whatever, as I said when I was growing up it was common knowledge that Galileo had invented the telescope. During the 1960s and 1970s as history of science slowly crept out of its niche and became more public and more popular this myth was at some point put out of its misery and buried discretely, where, I thought, nobody would find it again. I was wrong.

When I wrote my essay on the origins of the reflecting telescope for the online journal AEON, my editor, Corey Powell, who is himself a first class science writer and an excellent editor, asked me to provide a list of reference books to help speed up the process of fact checking my essay. I was more than happy to oblige, as even more embarrassing than a fact checker finding a factual error in what I had written, and yes even I make mistakes, would be a reader finding a real clangour after my essay had been published. As it turned out I hadn’t made any mistakes or if I did nobody has noticed yet. Imagine my surprise when I read an essay published two days ago on AEON that stated Galileo had invented the telescope. Hadn’t it been fact checked? Or if so, didn’t the fact checker know that this was a myth?

The essay in question is titled Forging Islamic Science and was written by Nir Shafir and edited by Sally Davies. The offending claim was at the beginning of the second paragraph:

Besides the colours being a bit too vivid, and the brushstrokes a little too clean, what perturbed me were the telescopes. The telescope was known in the Middle East after Galileo invented it in the 17th century, but almost no illustrations or miniatures ever depicted such an object.

I tweeted the following to both the author’s and AEON’s Twitter accounts:

If the author is complaining about forgers getting historical details wrong he really shouldn’t write, “The telescope was known in the Middle East after Galileo invented it in the 17th century…”

The author obviously didn’t understand my criticism and tweeted back:

There are references to the use of telescopes for terrestrial observations, mainly military, in the Ottoman Empire, such as in evliya çelebi.

I replied:

Galileo did not invent the telescope! He wasn’t even the first astronomer to use one for astronomical observations!

Whereupon Sally Davies chimed in with the following:

Thank you for drawing this to our attention! A bit of ambiguity here; we have tweaked the wording to say he ‘developed’ the telescope.

Sorry but no ambiguity whatsoever, Galileo did not in anyway invent the telescope and as I will explain shortly ‘developed’ is just as bad.

Today the author re-entered the fray with the following:

Thank you for bringing this up. It’s always good to get the minor details right.

The invention of the telescope is one of the most significant moments in the whole history of science and technology, so attributing its invention to the completely false person is hardly a minor detail!

About that ‘developed’. A more recent myth, which has grown up around Galileo and his use of the telescope, is that he did something special in some sort of way to turn this relatively new invention into a scientific instrument usable for astronomical observations. He didn’t. The telescope that Galileo used to discover the Moons of Jupiter differed in no way either scientifically or technologically from the one that Hans Lipperhey demonstrated to the assembled prominence at the peace conference in Den Hague sometime between the 25thand 29thof September 1608. Lipperhey’s invention was even pointed at the night sky, “and 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.”[1]

Both instruments consisted of a tube with a biconvex or plano-convex objective lens at one end and a bi-concave or plano-concave eyepiece lens at the other end. The eyepiece lens also had a mask or stop to cut down the distortion caused around the edges of the lens. The only difference was in the focal lengths of the lenses used producing different magnitudes of magnification. Galileo’s use of other lenses to increase magnification was nothing special; it had been done earlier than Galileo by Thomas Harriot and at least contemporaneous if not earlier by Simon Marius. It was also done by numerous others, who constructed telescopes independently in those first few years of telescopic astronomical observation. The claims that Galileo had developed, improved, specialised, etc., etc., the telescope are merely mythological elements of the more general Galileo hagiography. Modern research has even revealed that contrary to his own claims Galileo probably did not (re)-construct the telescope purely from having heard reports about it but had almost certainly seen and handled one before he attempted to construct one himself.

Going back to the offending AEON essay, Sally Davies could have saved herself and Nir Sharfir if she had simply changed the sentence to:

The telescope was known in the Middle East after it was invented  in the late 16th early 17th century…(even I make mistakes)

What I intended to write before my brain threw a wobbly was:

The telescope was known in the Middle East after it was invented in late 1608…

 She doesn’t even need to mention Lipperhey’s name if she wants to avoid the on going debates about who really did invent the telescope.








[1]Embassies of the King of Siam Sent to His Excellency Prince Maurits, Arrived in The Hague on 10 September 1608


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

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