Category Archives: History of Astronomy

Planetary Tables and Heliocentricity: A Rough Guide

Since it emerged sometime in the middle of the first millennium BCE the principal function of mathematical astronomy was to provide the most accurate possible predictions of the future positions of the main celestial bodies. This information was contained in the form of tables calculated with the help of the mathematical models, which had been derived by the astronomers from the observed behaviour of those bodies, the planets. The earliest Babylonian models were algebraic but were soon replaced by the Greeks with geometrical models based on spheres and circles. To a large extent it did not matter if those models were depictions of reality, what mattered was the accuracy of the prediction that they produced; that is the reliability of the associated tables. The models of mathematical astronomy were judge on the quality of the data they produced and not on whether they were a true reproduction of what was going on in the heavens. This data was used principally for astrology but also for cartography and navigation. Mathematical astronomy was a handmaiden to other disciplines.

Before I outline the history of such tables, a brief comment on terminology. Data on the movement of celestial bodies is published under the titles planetary tables and ephemerides (singular ephemeris). I know of no formal distinction between the two names but as far as I can determine planetary tables is generally used for tables calculated for quantitatively larger intervals, ten days for example, and these are normally calculated directly from the mathematical models for the planetary movement. Ephemeris is generally used for tables calculated for smaller interval, daily positions for example, and are often not calculated directly from the mathematical models but are interpolated from the values given in the planetary tables. Maybe one of my super intelligent and incredibly well read readers knows better and will correct me in the comments.

The Babylonians produced individual planetary tables, in particular of Venus, but we find the first extensive set in the work of Ptolemaeus. He included tables calculated from his geometrical models in his Syntaxis Mathematiké (The Almagest), published around 150 CE, and to make life easier for those who wished to use them he extracted the tables and published them separately, in extended form with directions of their use, in what is known as his Handy Tables. This publication provided both a source and an archetype for all future planetary tables.

The important role played by planetary tables in mathematical astronomy is illustrated by the fact that the first astronomical works produced by Islamic astronomers in Arabic in the eighth-century CE were planetary tables known in Arabic as zījes (singular zīj). These initial zījes were based on Indian sources and earlier Sassanid Persian models. These were quickly followed by those based on Ptolemaeus’ Handy Tables. Later sets of tables included material drawn from Islamic Arabic sources. Over 200 zījes are known from the period between the eighth and the fifteenth centuries. Because planetary tables are dependent on the observers geographical position most of these are only recalculation of existing tables for new locations. New zījes continued to be produced in India well into the eighteenth-century.

With the coming of the European translators in the twelfth and thirteenth centuries and the first mathematical Renaissance the pattern repeated itself with zījes being amongst the first astronomical documents translated from Arabic into Latin. Abū ʿAbdallāh Muḥammad ibn Mūsā al-Khwārizmī was originally better known in Europe for his zīj than for The Compendious Book on Calculation by Completion and Balancing” (al-Kitab al-mukhtasar fi hisab al-jabr wa’l-muqabala), the book that introduced algebra into the West. The Toledan Tables were created in Toledo in the eleventh-century partially based on the work of Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Zarqālī, known in Latin as Arzachel. In the twelfth-century they were translated in Latin by Gerard of Cremona, the most prolific of the translators, and became the benchmark for European planetary tables.

In the thirteenth- century the Toledan Tables were superseded by the Alfonsine Tables, which were produced by the so-called Toledo School of Translators from Islamic sources under the sponsorship of Alfonso X of Castile. The Alfonsine Tables remained the primary source of planetary tables and ephemerides in Europe down to the Renaissance where they were used by Peuerbach, Regiomontanus and Copernicus. Having set up the world’s first scientific press Regiomontanus produced the first ever printed ephemerides, which were distinguished by the accuracies of their calculations and low level of printing errors. Regiomontanus’ ephemerides were very popular and enjoyed many editions, many of them pirated. Columbus took a pirate edition of them on his first voyage to America and used them to impress some natives by accurately predicting an eclipse of the moon.

By the fifteenth-century astronomers and other users of astronomical data were very much aware of the numerous inaccuracies in that data, many of them having crept in over the centuries through frequent translation and copying errors. Regiomontanus was aware that the problem could only be solved by collecting new basic observational data from which to calculate the tables. He started on such an observational programme in Nürnberg in 1470 but his early death in 1475 put an end to his endeavours.

When Copernicus published his De revolutionibus in 1543 many astronomers hoped that his mathematical models for the planetary orbits would lead to more accurate planetary tables and this pragmatic attitude to his work was the principle positive reception that it received. Copernicus’ fellow professor of mathematic in Wittenberg Erasmus Reinhold calculated the first set of planetary tables based on De revolutionibus. The Prutenic Tables, sponsored by Duke Albrecht of Brandenburg Prussia (Prutenic is Latin for Prussian), were printed and published in 1551. Ephemerides based on Copernicus were produced by Johannes Stadius, a student of Gemma Frisius, in 1554 and by John Feild (sic), with a forward by John Dee, in 1557. Unfortunately they didn’t live up to expectations. The problem was that Copernicus’ work and the tables were based on the same corrupted data as the Alfonsine Tables. In his unpublished manuscript on navigation Thomas Harriot complained about the inaccuracies in the Alfonsine Tables and then goes on to say that the Prutenic Tables are not any better. However he follows this complaint up with the information that Wilhelm IV of Hessen-Kassel and Tycho Brahe on Hven are gathering new observational data that should improve the situation.

As a young astronomer the Danish aristocrat, Tycho Brahe, was indignant that the times given in both the Alfonsine and the Prutenic tables for a specific astronomical event that he wished to observe were highly inaccurate. Like Regiomontanus, a hundred years earlier, he realised that the problem lay in the inaccurate and corrupted data on which both sets of tables were based. Like Regiomontanus he started an extensive programme of astronomical observations to solve the problem, initially at his purpose built observatory financed by the Danish Crown on the island of Hven and then later, through force of circumstances, under the auspices of Rudolph II, the Holy Roman German Emperor, in Prague. Tycho devoted almost thirty years to accruing a vast collection of astronomical data. Although he was using the same observational instruments available to Ptolemaeus fifteen hundred years earlier, he devoted an incredible amount of time and effort to improving those instruments and the methods of using them, meaning that his observations were more accurate by several factors than those of his predecessors. What was now needed was somebody to turn this data into planetary tables, enter Johannes Kepler. Kepler joined Tycho in Prague in 1600 and was specifically appointed to the task of producing planetary tables from Tycho’s data. Contrary to popular belief he was not employed by Tycho but directly by Rudolph.

Following Tycho’s death, a short time later, a major problem ensued. Kepler was official appointed Imperial Mathematicus, as Tycho’s successor, and still had his original commission to produce the planetary tables for the Emperor, however, legally, he no longer had the data; this was Tycho’s private property and on his death passed into the possession of his heirs. Kepler was in physical possession of the data, however, and hung on to it during the protracted, complicated and at times vitriolic negotiations with Tycho’s son in law, Frans Gansneb Genaamd Tengnagel van de Camp, over their future use. In the end the heirs granted Kepler permission to use the data with the proviso that any publications based on them must carry Tengnagel’s name as co-author. Kepler then proceeded to calculate the tables.

Put like this, it sounds like a fairly straightforward task, however it was difficult and tedious work that Kepler loathed intensely. It was not made any easier by the personal and political circumstances surrounding Kepler over the years he took to complete the task. Wars, famine, usurpation of the Emperor’s throne (don’t forget the Emperor was his employer) and family disasters all served to make his life more difficult.

Finally in 1626, twenty-six years after he started Kepler had finally reduced Tycho’s thirty years of observations into planetary tables for general use, now he only had to get them printed. Drumming up the financial resources for the task was the first hurdle that Kepler successfully cleared. He then purchased the necessary paper and settled in Linz to complete the task of turning his calculations into a book. As the printing was progressing all the Protestants in Linz were ordered to leave the city, Kepler, being Imperial Mathematicus, and his printer were granted an exemption to finish printing the tables but then Wallenstein laid siege to the city to supress a peasants uprising. In the ensuing chaos the printing shop and the partially finished tables went up in flames.

Leaving Linz Kepler now moved to Ulm where, starting from the beginning again, he was finally able to complete the printing of the Rudophine Tables, named after the Emperor who had originally commissioned them but dedicated to the current Emperor, Ferdinand II. Although technically not his property, because he had paid the costs of having them printed Kepler took the finished volumes to the book fair in Frankfurt to sell in September 1627.

Due to the accuracy of Tycho’s observational data and the diligence of Kepler’s mathematical calculations the new tables were of a level of accuracy never seen before in the history of astronomy and fairly quickly became the benchmark for all astronomical work. Perceived to have been calculated on the basis of Kepler’s own elliptical heliocentric astronomy they became the most important artefact in the general acceptance of heliocentricity in the seventeenth century. As already stated above systems of mathematical astronomy were judged on the data that they produced for use by astrologers, cartographers, navigators et al. Using the Rudolphine Tables Gassendi was able to predict and observe a transit of Mercury in 1631, as Jeremiah Horrocks succeeded in predicting and observing a transit of Venus for the first time in human history based on his own calculations of an ephemeris for Venus using Kepler’s tables, it served as a confirming instance of the superiority of both the tables and Kepler’s elliptical astronomy, which was the system that came to be accepted by most working astronomers in Europe around 1660. The principle battle in the war of the astronomical systems had been won by a rather boring set of mathematical tables, Johannes Kepler’s Tabulae Rudolphinae.

Rudolphine Tables Frontispiece

Rudolphine Tables Frontispiece

 

 

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Filed under History of Astrology, History of Astronomy, History of Cartography, History of Navigation, History of science, Renaissance Science

The Transition to Heliocentricity: The Rough Guides

Prompted by a question from Brian Cox, on Twitter, I wrote a post outlining the history of Galileo’s engagement with heliocentricity and the Catholic Church giving it the sub-title “A Rough Guide”. This post in turn provoked a series of question and answers on Twitter between myself and my #histsci soul-sister Dr Rebekah “Becky” Higgitt, which I developed into a post on the role played by the observations of the phases of Venus in the gradual acceptance of heliocentricity; a second post to which I added the sub-title “A Rough Guide”. I have now decided to go with the flow and produce a series of posts dealing one by one with the various things that contributed to the gradual transition from a geocentric to a heliocentric astronomy during the sixteenth and seventeenth centuries, each post bearing the sub-title “A Rough Guide”.

The aim is to demonstrate that this transition was not a simple question of the one is right and the other wrong, as it is unfortunately all too often presented today, particularly by those of a gnu atheist persuasion, but that within the context of the times the various factors involved often required subtle and careful interpretation and were not the clear cut evidence that hindsight seems to make them now. For example, I hope I have already achieved this in the post on the phases of Venus. To make it easier for readers to put the whole series together and to form, for themselves, the big picture, I have added a new separate page to the Renaissance Mathematicus, which will contain a list of all the posts, with links.

Suggestions, from readers, for topics to be dealt with in this series are welcome; I already have a list of eight, the first of which will be posted some time next week.

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The Phases of Venus and Heliocentricity: A Rough Guide

The word planet comes from the Greek word for wanderer. When people first started observing the heavens most of those points of light that we call stars appeared to remain fixed in place relative to each other, although the whole bowl of twinkling points appeared to revolve around the earth once every twenty-four hours, hence they became known as the sphere of fixed stars. With time however the early observers noticed that some of those points of lights behaved very differently to the vast majority, appearing to wander somewhat randomly around the heavens and these maverick stars became the planets. Further observations showed that the movement of the wanderers were in fact not random but followed a regularity that could, over suitably long periods of time, be recorded and then predicted in advance and planetary astronomy was born, however the behaviour of the various wanderers differed.

The Sun and Moon, which were both regarded as planets, have very special geocentric orbits and delivered the basics of timekeeping, the year and the day – the Sun – and the month and possible the seven day week (the phases of the moon) – the Moon. In the most common order of the planets, Moon, Mercury, Venus, Sun, Mars Jupiter and Saturn moving outwards from the Earth the remaining five planets were divided into the inner and outer planets with the Sun’s orbit providing the dividing line. The outer planets – Mars, Jupiter and Saturn – display a rather curious behaviour. They trundle along quite regularly in one directions then halt, reverse direction for a short period, halt again then reversing direction once again continue as before. This brief period of reversed motion is called retrograde motion and I’ll deal with its history and significance for heliocentricity in another post.

The two inner planets – Mercury and Venus – display a completely different orbital behaviour viewed from the Earth. Firstly they never stray very far from the Sun. They disappear for periods of time first being one side of the sun then reappearing on the other side and lastly their orbits around the Earth is exactly the same as the Sun’s i.e. one year. This combination of phenomena led some astronomers in antiquity to hypothesise that Venus and Mercury do not orbit the Earth but the Sun, being carried with it on its annual journey around the Earth. This model became know as the Egyptian or Heracleidian system. It was also presented in late antiquity by Martianus Capella in his De nuptiis Philologiae et Mercurii (“On the Marriage of Philology and Mercury”) a text that was very well known and popular in the Middle Ages and so the Heracleidian model was also well known in the Early Modern Period.

 

Capellan system - Valentin Naboth (1573)

Capellan system – Valentin Naboth (1573)

In the sixteenth-century the Danish astronomer Tycho Brahe seeing the advantages of Copernicus’ heliocentric astronomy but very unhappy about a moving Earth extended the Heracleidian system in that he let all five of the planets orbit the Sun, which in turn orbited the Earth.

 

Tychonic System

Tychonic System

The telescope made its public debut in Holland in September 1608. Within a year Thomas Harriot in London, Simon Marius in Ansbach, Galileo Galilei in Padua, and the Jesuits Odo van Maelcote and Giovanni Paolo Lembo in Rome were all using the new instrument to make astronomical observations and ushering in a new era in our understanding of the cosmos. Famously, Galileo was the first in print with his Sidereus Nuncius, the impact of which I’ve dealt with here. The earliest known reference to the possibility of Venus having phases occurs in a letter sent by the mathematician Benedetto Castelli to his old teacher Galileo in December 1610. Referencing thoughts of Copernicus from chapter ten of book I of De revolutionibus, Castelli enquired if the telescope would make it possible to observe phases of Venus. This enquiry makes two assumptions, firstly that Venus orbits the sun and secondly that it is lit by reflected light from the sun and is not a light source itself.

Galileo experts are divided as to whether Galileo had already been considering the question before he received Castelli’s letter or whether he appropriated the idea without giving his onetime student the credit he deserved. Whatever, shortly after receiving this letter Galileo wrote to Kepler in Prague enclosing the following anagram announcing a new sensational discovery:

Haec immatura a me iam frustra leguntur o.y.

This reads in translation, “I am now bringing these unripe things together in vain, Oy!” It was common practice for researchers in the Early Modern Period to announce their new discoveries in the form of anagrams to establish their priority in an age that knew no patents or copyright in the modern sense. Kepler was unable to decipher Galileo’s message and had to wait until the Tuscan astronomer revealed his sensation to the world. Deciphered the anagram read as follows, in Latin:

Cynthiae figuras aemulatur mater amorum

In English translation this reads as, “The mother of love [Venus] copies the forms of Cynthia [the Moon]”. In other words Galileo had discovered that Venus has phases like the Moon and therefore must orbit the Sun and not the Earth. Also in 1610 Galileo informed his friend and former patron Christoph Clavius in Rome of his discovery. He included his discovery in his first letter on sunspots written and distributed privately in 1611/12 but which wasn’t published until 1613.

 

Galileo's Sunspot Letters

Galileo’s Sunspot Letters

Actually having phases was not a sufficient proof of Venus’ heliocentricity; the matter is in reality somewhat more complicated. If Venus were to orbit the Earth in a geocentric system between the Earth and the Sun, as proposed by Ptolemaeus, then it would also display phases. However the phases of the two configurations differ substantially so the accurate observation of those phases is a true experimentum crucis, in Francis Bacon’s sense, between a geocentric and a heliocentric Venus. What Galileo had in fact observed were phases consistent with a heliocentric orbit for Venus.

 

The Phases of Venus in both systems

The Phases of Venus in both systems

Independently of Galileo, Harriot, Marius and the Collegio Romano astronomers also observed the phases of Venus so there was no doubt that Venus and, by analogy, probably Mercury, (the phases of Mercury were first observed by the Jesuit astronomer Giovanni Battista Zupi in 1639) orbited the Sun and not the Earth. Harriot as usual did not publish, Marius sent his discovery to Kepler who published it in the preface of his Dioptrice in 1611. Odo von Maelcote included the Jesuit confirmation of Galileo’s observations in his speech during the banquet to honour Galileo at the Collegio Romano in 1611.

This discovery put an end, once and for all, to a pure geocentric system à la Ptolemaeus but did not as Castelli thought, in his letter to Galileo, provide definitive proof of Copernicus’ heliocentric system. Both the ancient Heracleidian and Tycho’s helio-geocentric systems would display the same, newly discovered, phases of Venus. This situation is illustrated on the famous title page of Riccioli’s Almagestum Novum (1651), which shows Ptolemaeus lying on the ground with his system, feebly claiming, “I will rise again” whilst Urania weighs the merits of the Copernican heliocentric system against those of Riccioli’s own semi-Tychonic system. In Riccioli’s system Mercury, Venus and Mars orbit the Sun, which in turn, together with Jupiter and Saturn, orbits the Earth. As far as I know, nobody other than Riccioli ever propagated this strange beast.

 

Title page Riccioli’s Almagestum Novum (1651)

Title page Riccioli’s Almagestum Novum (1651)

Although the phases of Venus were not decisive in deciding the conflict between the supporters of geocentricity and those of heliocentricity they did provide an important step along the twisting road towards the eventual acceptance of a heliocentric model, Kepler’s, for the then known cosmos.

 

h/t to my #histsci soul sister Rebekah “Becky” Higgitt whose questions on this topic on Twitter inspired this post.

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Science grows on the fertilizer of disagreement

At the weekend German television presented me with all three episodes of Jim Al-Khalili’s documentary on the history of electricity, Shock and Awe: The Story of Electricity. On the whole I found it rather tedious largely because I don’t like my science or history of science served up by a star presenter who is the centre of the action rather than the science itself, a common situation with the documentaries of ‘he who shall not be named’-TPBoPS, and NdGT. It seems that we are supposed to learn whatever it is that the documentary nominally offers by zooming in on the thoughtful features of the presenter, viewing his skilfully lit profile or following him as he walks purposefully, thoughtfully, meaningfully or pensively through the landscape. What comes out is “The Brian/Neil/Jim Show” with added science on the side, which doesn’t really convince me, but maybe I’m just getting old.

However my criticism of the production style of modern television science programmes is not the real aim of this post, I’m much more interested in the core of the first episode of Al-Khalili’s documentary. The episode opened and closed with the story of Humphrey Davy constructing the, then, largest battery in the world in the cellars of the Royal Institution in order to make the first ever public demonstration of an arc lamp and thus to spark the developments that would eventually lead to electric lighting. Having started here the programme moved back in time to the electrical experiments of Francis Hauksbee at the Royal Society under the auspices of Isaac Newton. Al-Khalili then followed the development of electrical research through the eighteenth-century, presenting the work of the usual suspects, Steven Gray, Benjamin Franklin etc., until we arrived at the scientific dispute between the two great Italian physicists Luigi Galvani and Alessandro Volta that resulted in the invention of the Voltaic pile, the forerunner of the battery and the first producer of an consistent electrochemical current. All of this was OK and I have no real criticisms, although I was slightly irked by constant references to ‘Hauksbee’s’ generator when the instrument in question was an adaption suggested by Newton of an invention from Otto von Guericke, who didn’t get a single name check. What did irritate me and inspired this post was the framing of the Galvani-Volta dispute.

Al-Khalili, a gnu atheist of the milder variety, presented this as a conflict between irrational religious persuasion, Galvani, and rational scientific heuristic, Volta, culminating in a victory for science over religion. In choosing so to present this historical episode Al-Khalili, in my opinion, missed a much more important message in scientific methodology, which was in fact spelt out in the fairly detailed presentation of the successive stages of the dispute. Galvani made his famous discovery of twitching frog’s legs and after a series of further experiments published his theory of animal electricity. Volta was initially impressed by Galvani’s work and at first accepted his theory. Upon deeper thought he decided Galvani’s interpretation of the observed phenomena was wrong and conducted his own series of result to prove Galvani wrong and establish his own theory. Volta having published his refutation of Galvani’s theory, the latter not prepared to abandon his standpoint also carried out a series of new experiments to prove his opponent wrong and his own theory right. One of these experiments led Volta to the right explanation, within the knowledge framework of the period, and to the discovery of the Voltaic pile. What we see here is a very important part of scientific methodology, researchers holding conflicting theories spurring each other on to new discoveries and deeper knowledge of the field under examination. The heuristics of the two are almost irrelevant, what is important here is the disagreement as research motor. Also very nicely illustrated is discovery as an evolutionary process spread over time rather than the infamous eureka moment.

The inspiration produced from watching Al-Khalili’s story of the invention of the battery chimes in very nicely with another post I was planning on writing. In a recent blog post, Joe Hanson of “it’s OKAY to be SMART” wrote about Galileo and the first telescopic observations of sunspots at the beginning of the seventeenth-century. The post is OK as far as it goes, even managing to give credit to Thomas Harriot and Johannes Fabricius, however it contains one truly terrible sentence that caused my heckles to rise. Hanson wrote:

Although Galileo’s published sunspot work was the most important of its day, on account of the “that’s no moon” smackdown it delivered to the Jesuit scientific community, G-dub was not the first to observe the solar speckles.

Here we have another crass example of modern anti-religious sentiment of a science writer getting in the way of sensible history of science. What we are talking about here is not the Jesuit scientific community but the single Jesuit physicist and astronomer Christoph Scheiner, who famously became embroiled in a dispute on the nature of sunspots with Galileo. Once again we also have an excellent example of scientific disagreement driving the progress of scientific research. Scheiner and Galileo discovered sunspots with their telescopes independently of each other at about the same time and it was Scheiner who first published the results of his discoveries together with an erroneous theory as to the nature of sunspots. Galileo had at this point not written up his own observations, let alone developed a theory to explain them. Spurred on by Scheiner’s publication he now proceeded to do so, challenging Scheiner’s claim that the sunspots where orbiting the sun and stating instead that they were on the solar surface. An exchange of views developed with each of the adversaries making new observations and calculations to support their own theories. Galileo was not only able to demonstrate that sunspots were on the surface of the sun but also to prove that the sun was rotating on its axis, as already hypothesised by Johannes Kepler. Scheiner, an excellent astronomer and mathematician, accepted Galileo’s proofs and graciously acknowledge defeat. However whereas Galileo now effectively gave up his solar observations Scheiner developed new sophisticated observation equipment and carried out an extensive programme of solar research in which he discovered amongst other things that the sun’s axis is tilted with respect to the ecliptic. Here again we have two first class researchers propelling each other to new important discoveries because of conflicting views on how to interpret observed phenomena.

My third example of disagreement as a driving force in scientific discovery is not one that I’ve met recently but one whose misrepresentation has annoyed me for many years, it concerns Albert Einstein and quantum mechanics. I have lost count of the number of times that I’ve read some ignorant know-it-all mocking Einstein for having rejected quantum mechanics. That Einstein vehemently rejected the so-called Copenhagen interpretation of quantum mechanics is a matter of record but his motivation for doing so and the result of that rejection is often crassly misrepresented by those eager to score one over the great Albert. Quantum mechanics as initial presented by Niels Bohr, Erwin Schrödinger, Werner Heisenberg et. al. contradicted Einstein fundamental determinist metaphysical concept of physics. It was not that he didn’t understand it, after all he had made several significant contributions to its evolution, but he didn’t believe it was a correct interpretation of the real physical world. Einstein being Einstein he didn’t just sit in the corner and sulk but actively searched for weak points in the new theory trying to demonstrate its incorrectness. There developed a to and fro between Einstein and Bohr, with the former picking holes in the theory and the latter closing them up again. Bohr is on record as saying that Einstein through his informed criticism probably contributed more to the development of the new theory than any other single physicist. The high point of Einstein’s campaign against quantum mechanics was the so-called EPR (Einstein-Podolsky-Rosen) paradox, a thought experiment, which sought to show that quantum mechanics as it stood would lead to unacceptable or even impossible consequences. On the basis of EPR the Irish physicist John Bell developed a testable theorem, which when tested showed quantum mechanics to be basically correct and Einstein wrong, a major step forward in the establishment of quantum physics. Although proved wrong in the end Einstein’s criticism of and disagreement with quantum mechanics contributed immensely to the theories evolution.

The story time popular presentations of the history of science very often presents the progress of science as a series of eureka moments achieved by solitary geniuses, their results then being gratefully accepted by the worshiping scientific community. Critics who refuse to acknowledge the truth of the new discoveries are dismissed as pitiful fools who failed to understand. In reality new theories almost always come into being in an intellectual conflict and are tested, improved and advanced by that conflict, the end result being the product of several conflicting minds and opinions struggling with the phenomena to be explained over, often substantial, periods of time and are not the product of a flash of inspiration by one single genius. As the title says, science grows on the fertilizer of disagreement.

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Galileo, the Church and Heliocentricity: A Rough Guide.

A couple of days ago on Twitter, Brian Cox asked the Twitter historians, “Did Galileo know that he would annoy the Church when he published The Starry Messenger?” The very simple answer to this question is, no but a lengthy discussion of the situation developed on Twitter. It was suggested that somebody should produce a short temperate answer to the question as a reference source and after some hesitation I have acquiesced. This will be a relative short presentation of the various stages of this historical process with a minimum of explanation and justification, as Joe Friday used to say, “the facts ma’am, just the facts!” This is of course my interpretation but it is based on a fairly good knowledge of the most recent principal secondary literature on the subject and it is one that I think would find fairly general agreement amongst those who have seriously studied the subject. Those who disagree are welcome, as always, to air their views in the comments but I expect those who choose to do so to base those views on historical facts and not on prejudice.

The first thing to make clear is the situation in terms of astronomy, cosmology and the Church in the first decade of the seventeenth-century before Galileo, Marius, Harriot, Lembo and others changed our view of the cosmos forever with the recently invented telescope. Astronomy and cosmology were not very high up on the Church’s agenda between 1600 and 1610. The vast majority of people, including the experts, still believed in a geocentric cosmos in the form developed by Ptolemaeus, the most modern version being basically that of Peuerbach and Regiomontanus. A very small handful believed in the Copernican heliocentric model, and believed is the right word because it lacked any real form of empirical proof and was burdened by all the physical problems engendered by a moving earth. A probably equally small number favoured a Tychonic geo-heliocentric model with or without a rotating earth and another small number were finding favour with Gilbert’s geocentric model with a rotating earth. All of the discussions were very academic and nothing that could or would threaten the dominance of a solid Bible conform geocentricity, so nothing for the Church to get its knickers in a twist about.

The telescopic discoveries were brand new empirical evidence and the biggest shake up in astronomy since mankind first cast its little beady eyes on the heavens. When he started to make his discoveries, late in 1609, Galileo was very much aware of the fact that he was sitting on the Renaissance equivalent of a Nobel prize, a knighthood and the keys to the treasure chest all in one and also very aware that he almost certainly wasn’t the only person making or about to make these discoveries. In the last point he was of course completely right, Harriot was ahead of him and Marius was breathing down his neck. Galileo was fully aware that if his wished to cash in then he had to get his priority claim in tout suite.

To understand this one needs to look at Galileo’s situation. In 1610 he was a forty-six year old professor of mathematics, stuck in the same rather lowly position for the last eighteen years. He was on the down hill slope to ill health, death and anonymity. He had already done his ground-breaking work on dynamics but hadn’t published it. If he were to die tomorrow nobody would remember him beyond a few close friends and his family. Now he had hit the jackpot and needed to cash in fast. He bunged his principal discoveries together in book form, in what was more a press release than a scientific report, the Sidereus Nuncius, and had it printed and published as fast as possible.

The last thing the Galileo wanted to do at this point was to annoy anybody; he wanted fame and fortune not infamy. He spent as much effort on getting permission to dedicate his small book to Cosimo Medici, the ruler of the Duchy of Florence, his home province, and his sometime private pupil, as he did on his telescopic observations. He also made very sure that the Medici would approve of the name he gave to the newly discovered moons of Jupiter; he was after preferment, which he got as a result of his clever tactical manoeuvring. He would have been mortified if his publication had caused problems with the Church in Rome because that would almost certainly have cost him any chance of an appointment to the Medici court, his main aim at the time. The Medici did in fact drop him when he finally collided with the Church in the 1620s.

The telescopic discoveries, which Galileo was the first to publish, shook up the whole of Europe and not just the Catholic Church. However the contents of Sidereus Nuncius neither disproved Ptolemaeus/Peuerbach nor did they prove Copernicus, as I’ve already explained here. Of course at first they did nothing at all because like all new scientific discoveries they needed to be confirmed by other astronomers. This proved to be somewhat difficult, as the available telescopes were very poor quality and Galileo was an exceptional telescopic observer. In the end it was the Church’s own official astronomers, the members of Clavius’ mathematical research group at the Collegio Romano, who with the active assistance of Galileo delivered the necessary confirmation of all of Galileo’s discoveries.

Hailed now as the greatest astronomer in Europe Galileo travelled in triumph to Rome where he was feted by the mathematicians of the Collegio Romano, who threw a banquet in his honour, had an audience with the Pope and was appointed a member of the Accademia dei Lincei who also threw a banquet in his honour. No signs of annoyance here. Galileo was appointed philosophicus and mathematicus to the Medici court in Florence, as well as professor for mathematics without teaching obligations at the University in Pisa. The humble insignificant mathematician had become a renowned social figure, almost overnight, feted and praised throughout Europe. High Church officials flocked to make his acquaintance and win his friendship, one of these, the Cardinal Maffeo Barberini, became a close friend and the cause of Galileo’s downfall later in his life.

Although nothing in the Sidereus Nuncius disproved the geocentric model of Ptolemaeus the discovery of the phases of Venus a short time later, by Galileo, Lembo, Harriot and Marius, did. The basic geocentric model was dead in the water and the Church had a problem because Holy Scripture clearly implied a geocentric cosmos. Riding on the wave of his fame Galileo wanted to go for the big one. He wanted to go down in history as the man who proved that the cosmos was heliocentric. Unfortunately he lacked a genuine proof. He had evidence that the cosmos was not geocentric and not homocentric but all the available empirical evidence satisfied both a heliocentric cosmos and a geo-heliocentric Tychonic one and it was the latter that most astronomers, still worried about the physical problems of a moving earth, tended to favour.

Around 1613, despite his lack of genuine proof Galileo began to canvas his newly won influential friends in Rome in an attempt to convince them to give their support to a call for the acceptance of a heliocentric cosmos, a dangerous move. The Church was a vast structure set in its ways and like a large ocean liner getting it to stop in full motion and reverse its direction was something that required a lot of time and space, Galileo eager to make his mark in history lacked the necessary patience to wait for the Church to accept the inevitable and was trying to force the pace. Several of his friends including Maffeo Barbarini advised him to calm down and not to force the Church into a corner, but Galileo, his ego inflated by his recent successes failed to heed this sound advice.

In the next couple of years both Galileo and the Carmelite father Paolo Antonio Foscarini tried to tell the Church how to reinterpret those passages of the Bible that contradict a heliocentric interpretation of the cosmos. This was a fundamental failure and guaranteed to annoy the Church extremely, which it did. One should remember that all of this was taking place in the middle of the Counter Reformation and on the eve of the Thirty Years War, which would kill off between one third and two thirds of the entire population of Middle Europe in what was basically an argument about who had the right to interpret the Bible. The Church set up a commission to investigate Foscarini’s book on the subject and the commission came down very hard on heliocentricity, calling it both philosophically (read scientifically) absurd and heretical. The accusation of heresy was not confirmed by the Pope and so was never official Church doctrine, but the damage was done. Cardinal Roberto Bellarmino was instructed to inform Galileo of the commission’s judgement. In a friendly chat Bellarmino did just this, informing Galileo that he could neither hold nor teach the theory that the cosmos was heliocentric. It is important to note that the theory was banned not the hypothesis. One could continue to discuss a hypothetical heliocentric cosmos, one could not, however, claim it to be fact. As many people have pointed out over the centuries this restriction was actually in line with the known empirical facts. The books of Kepler and other Protestants claiming that the cosmos was heliocentric were placed on the Index and Copernicus’ De revolutionibus was placed on the Index until corrected. Interestingly the Inquisition did just that. They removed the handful of passages from De revolutionibus that claimed the heliocentric cosmos to be fact and then gave the book free to be read, already in 1621. We still have Galileo’s personal censored copy of the book. This censorship was only really effective in Italy the rest of Europe not taking much notice of the Church’s efforts to suppress heliocentricity.

This setback did very little to slow down Galileo’s rise to fame and he became a very favoured celebrity throughout Northern Italy. Symptomatic for this is his notorious dispute with the Jesuit astronomer Orazio Grassi over the nature of comets that peaked in the publication of Galileo’s Il Saggiatore, in 1623. A dispute in which Grassi was scientifically right and Galileo wrong, but in which Galileo carried the laurels thanks to his superior polemic and the sycophantic cheers of his high powered fan club, which included the newly elected Pope, Urban VIII, Galileo’s old friend Maffeo Barberini.

Barberini’s elevation to the Holy Throne gave Galileo the chance he had been waiting and longing for, the chance to go down in history as the man who established the heliocentric cosmos. Using his friendship with the new Pope, Galileo convinced Barberini that the German Protestants were laughing at the Catholic Church because it had rejected heliocentricity because according to those dastardly Protestants the Catholics were too stupid to understand it. Beguiled by his silver tongued friend Barberini gave Galileo permission to write and publish a book in which he would present both the Ptolemaic and Copernican systems to demonstrate the deep astronomical knowledge of the Catholics but by no means was he to favour one of the systems. Galileo wrote the book, his Dialogo, in which he was anything but impartial and unbiased, as instructed, but instead left nobody in any doubt just how superior the Copernican system was in his opinion, however he still lacked any real empirical proof. Through a series of tricks he managed to get his book past the censors and into print. Galileo had erred very badly, you don’t play the most powerful absolutist ruler of your time for a fool, particularly not when that ruler is already displaying strong signs of the paranoia that, sooner or later, effects all absolutist rulers.

I’m not going to go into all of the contributory factors that played a part in the sorry mess that was Galileo’s trial by the Inquisitions, I’ll deal with those one day in another post, but it is safe to say that he got stamped on for his hubris. By comparison with other cases he didn’t actually get stamped on very hard and got off relatively lightly. I can already hear the screams of protest at the last sentence but within the context of the times and place where Galileo lived and moved it is an accurate description of his fate.

One thing that should be made very clear when discussing this whole sorry mess is that Galileo was never the fearless defender of scientific truth or freedom of speech that his modern fan club like to present him as. He was an extremely egotistical social climber with an eye on the main chance, his own undying fame. Through his ill-considered actions he achieved his goal but not quite in the way he had intended.

It is ironic that many people today still believe erroneously that Galileo actually proved the reality of a heliocentric cosmos in his Sidereus Nuncius.

[The original opening paragraph of this post was modified at the request of those who wish it to be used as a short simple reference source]

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The Moons of Jupiter

As anyone interested in astronomy or its history should know Io, Europa, Ganymede and Calisto are not only the names of four of Zeus’ lovers (or rape victims!) but also the names suggested privately by Kepler and publicly by Simon Marius for the four largest of Jupiter’s moons discovered on 7th and 8th January 1610 respectively by Galileo Galilei and Simon Marius. It must have been an exhilarating experience when they were first observed by those two pioneers of Renaissance telescopic astronomy and it is still an exciting one for an amateur astronomer in the twenty-first-century as related by Clive Thompson in a blog post at The Message. Unfortunately Thompson then goes on to complete misinterpret what that original discovery, four hundred years ago, meant for the cosmology and astronomy of the times. This is a topic I’ve dealt with before but it seems to be one that needs to be addressed at regular intervals like a game of #histsci Whac-A-Mole. What exactly did Thompson say that needs to be banged on the head?

Siderius [sic] Nuncius was a powerful piece of evidence that Copernicus was right: The Earth wasn’t the center of our solar system. The sun was, and the planets revolved around it. Astronomers had been gradually warming up to the idea, and even some church authorities had accepted the Copernican system as a mathematical theory. But by showing that Jupiter had its own moonsthat a planet could be a mini-system of its ownGalileo offered something rather more: Electrifying proof [emphasis in original] of the Copernican idea. You could argue endlessly (and people did) about the geometry and math of various systems explaining how the stars moved through the sky. It was just conjecture.

But proofthat’s different. Once people put their eyes to the telescope and saw those moons circling Jupiter, they had the same whoa-dude reaction that I had on the sidewalks of Brooklyn. The solar system got real. So real, in fact, that the church began to panic; and since Galileo went on to use his telescope to amass even more evidence against geocentrism, including the phases of Venus, religious authorities eventually stepped in and demanded he recant, or else.

To explain what is wrong with the above we first need to know what the accepted view of the cosmos in the first decade of the seventeenth-century. The standard model of the age was an uneasy alliance between Aristotelian cosmology and Ptolemaic astronomy. I say uneasy because the two systems were not actually compatible, something that the scholars of the period knew but chose, mostly, to ignore. It was this geocentric mish-mash that the handful of Copernicans and Tychonians were trying to dethrone. So what exactly was the scientific significance of the Galilei-Marius discovery of the Jupiter moons?

The discovery of the four principal moons of Jupiter didn’t actually have any direct relevance, either positive or negative, for Copernican heliocentricity. What it did do was to refute a central tenet of Aristotelian cosmology that of homo-centricity. Aristotelian cosmology stated that all celestial bodies revolve around the same central point, the earth. The discovery of the moons of Jupiter of course showed this to be totally wrong. Surprisingly this did little or no damage to Ptolemaic astronomy, as this was viewed by strict Aristotelians to already contradict this fundamental principle. In Ptolemaic astronomy the seven planets revolve around the centres of their respective epicycles, which are in turn carried around the earth, actually centred on a point other than the earth, on their deferents. This in the opinion of some Aristotelians was definitely not homo-centricity. This contradiction between the two systems of thought led to various revivals of concentric or homo-centric astronomy over the centuries the most recent being in the sixteenth-century barely a decade earlier than Copernicus’ publication of De revolutionibus. In fact Christoph Clavius, the leading proponent of Ptolemaic astronomy in 1610, regarded the homocentric astronomy of Giovanni Battista Amico and Girolamo Fracastoro to be a greater threat that Copernican heliocentricity and was quite happy to have it shot down by Jupiter’s moons.

Put very bluntly the discovery of the moons of Jupiter by Galileo and Marius was in no way what so ever a proof of the Copernican idea, something of which Galileo was very much aware and he did not try to present it as being one. Marius didn’t even consider it as he was a proponent of the Tychonic system to which he remained true all of his life.

The situation is of course different with the discovery of the phases of Venus. This discovery made independently by Thomas Harriot, Simon Marius, Galileo Galilei and Giovanni Paolo Lembo, the latter a Jesuit astronomer in Rome who probably discovered the phases before Galileo, effectively killed of a pure Ptolemaic astronomy as it proved that Venus, and probably Mercury by analogy (it would be some decades before the phases of Mercury were observed), orbited the sun and not the earth. Once again this is not in anyway a proof of the Copernican system, as there were other competing systems, the Heracleidian, in which Mercury and Jupiter Venus orbit the sun, which, along with the other planets, orbits the earth and the Tychonic in which all the planets except the moon orbit the sun which then orbits the earth, that were conform with the new telescopic discovery. In fact due to the very real unsolved physical problems presented by the concept of a moving earth most astronomers now chose the Tychonic model and not the Copernican one.

Thompson’s final comment about the Church panicking and forcing Galileo to recant is just pure historical hogwash. Any new empirical evidence needs to be confirmed by independent observers. It’s all very well for Professor Galilei the little known mathematicus from Padua to come along and say that he has discovered all of these wonderful things in the heavens with this new fangled device from Holland, if nobody else can see them. What is required is that other independent observers confirm that they too can see all that Signor Galilei claims to have seen. Given the extremely poor quality of the available telescopes and the optical limits of the Dutch or Galilean telescope this was not an easy task. Popular histories criticise contemporaries who failed to see what Galileo had seen but such critics have obviously never tried to observe the moons of Jupiter with a modern Galilean telescope with state-of-the-art good quality lenses, let alone one with very shitty quality seventeenth-century lenses. It is bloody difficult to put it mildly. So who in the end did provide the scientific confirmation that Galileo so desperately needed for his telescopic claims? This confirmation was delivered by the Jesuit professors of the Collegio Romano, the Vatican’s own astronomers. Doesn’t quite fit the picture of a Church in panic, does it?

The true reasons for that oh so notorious trial are far too complex so that I’m not going to deal with them here but I will just say that they have more to do with politics and authority than science. That however is the subject for another blog post on another day.

 

 

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Beware of hindsight!

This post is a sort of footnote to my review of Dan Falk’s The Science of Shakespeare it doesn’t really contain anything that I haven’t already said in several earlier posts but it does say something that I think bears repeating at regular intervals for those contemplating historical studies, the dangers of presentism. This time my thoughts were provoked by a comment on Twitter on my review. Jeffrey Newman (@JeffreyNewman) tweeted the following:

Is it too simplistic to suggest that Shakespeare, whose awareness of religious controversy is acute though his own views are wisely not revealed – must have been equally fascinated by contemporary scientific discoveries and controversies, news of which must have been circulating in his circles?

I had of course said something similar in the opening paragraph of my review:

Given that Shakespeare was born just twenty-one years after Copernicus’ De revolutionibus was published and lived through the period in which Kepler and Galileo, amongst others, made the heliocentric hypothesis the hottest item in the European scientific community it is not unreasonable to ask, as Falk does, in the more general sense, whether the cosmological and astronomical upheaval of the age left any traces in Will’s work.

What I wish to address here is to what extent Copernicus and heliocentricity really was actual and controversial during Shakespeare’s lifetime and how much of our perception that it must have been is actually the product of misapplied hindsight.

The common modern perception of the impact of Copernicus and his heliocentric cosmology finds its origins in the work of Immanuel Kant, one of the most influential of all European philosophers, in the late eighteenth century. Kant coined the term Die kopernikanischen Wende (The Copernican Turn) to describe what he saw as the biggest change of perception of humanities place in the cosmos that had ever taken place. In the course of the nineteenth century in English, Kant’s term mutated into the Copernican Revolution also called the Astronomical Revolution and often conflated with the Scientific Revolution, a concept also born in that century. For here on the advent of heliocentricity in the Early Modern Period was perceived as something stupendous, quite literally earth moving, a change in the intellectual climate that was almost without comparison in the history of human existence. But was it perceived as such in the second half of the sixteenth-century? The very simple answer is no, in fact rather the opposite, almost nobody took any notice of it at all.

Most astronomers and those who understood mathematical astronomy and cosmology found his book interesting but most of them remained largely unconvinced by his hypothesis and that’s all it was, an unsubstantiated hypothesis. Outside of this rather small circle of knowledgeable experts, Copernicus’ ideas received almost no attention at all. Put simply the majority of people living in Europe at that time had more important things to occupy their minds than the complex mathematical ideas of some German speaking cleric from the outskirts of civilization (Copernicus’ own estimate of his place of domicile). As I wrote in an earlier post on the same subject Copernicus’ hypothesis went off like a damp squib rather than the proverbial bombshell.

A more general discussion of the various competing systems of astronomy on offer at the beginning of the seventeenth-century first really took off in 1610 following the telescopic discoveries made by Galileo, Marius, Harriot, Lembo and others; the biggest impact being made by Galileo’s publication of his Sidereus Nuncius. I say various because there were more systems on offer than just Ptolemaic geocentricity and Copernican heliocentricity as I outlined in an earlier post. Kepler had thrown his hat into the ring one year earlier with his Astronomia nova, but his tendency to write long diatribes in convoluted Latin meant that not many people could be bothered to plough through his book. Heliocentricity, in the Keplerian version, first gained a foothold, as a viable alternative, after Kepler published his ideas in simple readable form in his Epitome Astronomiae Copernicanae, in three volumes between 1617 and 1621, and his Rudolphine Tables in 1623. Even here the acceptance, which was effectively completed by about 1660, was more gradual and low key than revolutionary.

On the negative side the common modern perception of the reception of the heliocentric hypothesis is almost totally shaped by the all too notorious dispute between Tuscany’s lamb to the slaughter, Galileo Galilei, and the big bad wolf of Early Modern history, the Catholic Church. Unfortunately here mythology rather than factual history looms large. The popular vision has the astronomers and cosmologist of Europe quaking in their shoes, only daring to discuss the new astronomy behind closed doors in fear of being used as fuel to fire the Vatican’s furnaces having first had their finger nails extracted with red hot pincers.

In reality there was almost no appreciable opposition to heliocentric astronomy before 1616. In 1616 the Catholic Church reacted to the attempts of Galileo and Foscarini to reinterpret Holy Scripture to remove the contradictions to heliocentric cosmology. This was done sotto voce and remained a purely local affair, causing hardly a ripple outside of Rome. Galileo’s trial in 1632 stirred up a lot more interest but its effect on the spread of heliocentric cosmology and astronomy in Europe was considerably less than most people imagine, in fact it was almost negligible outside of Italy, even in Catholic countries. Within Italy there was a short period of caution and then authors started producing heliocentric texts, which merely pointed out in the preface that the system whilst mathematically interesting was of course entirely hypothetical because the Holy Mother Church said so. A great battle between the Church and the astronomers never really took place and very few astronomers ever quaked in their shoes.

So what does this all mean for Dan Falk, Peter Usher and Will Shakespeare? As far as can be ascertained Shakespeare was active as a playwright from about 1590 to 1610, or possibly a couple of years longer. During this period heliocentric cosmology was not really a burning topic either scientifically or in any way socially, politically or religiously so there are no real grounds to think that Shakespeare would take up the topic in his plays, which were largely social or political commentaries. Usher argues that Shakespeare encoded the new astronomy in his plays, most notably Hamlet, rather than discussing it openly out of fear of repression. However nobody was being repressed for discussing Copernicus or Copernicanism during Shakespeare’s lifetime, he died in 1616 just as the Galileo affair was beginning, so this claim is based on a false assessment of the actual historical situation.

We now come to the crux of the matter. The arguments for a potential interest of Shakespeare in the evolving new astronomy in the closing decade of the sixteenth-century and the opening decade of the seventeenth-century and a necessity for secrecy on his part in taking an interest are based on hindsight and not on real historical research. The current view of the Copernican Revolution and its social, political and religious consequences consists largely of myths created in the late eighteenth-century and throughout the nineteenth-century. By projecting backwards from these myths, and that is committing the historical sin of presentism, rather than researching the actual historical facts Falk, Usher and Jeffrey Newman with his question on Twitter create a false scenario for Shakespeare and his potential interest in the then new but hardly present astronomy.

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