Category Archives: History of Astronomy

Misusing Galileo to criticise the Galileo gambit

Yesterday The Guardian website had an article on climate change denialists entitled, Here’s what happens when you try to replicate climate contrarian papers[1].

The article is headed with this portrait of Galileo

Galileo demonstrating his astronomical theories. Climate contrarians have virtually nothing in common with Galileo. Photograph: Tarker/Tarker/Corbis

Galileo demonstrating his astronomical theories. Climate contrarians have virtually nothing in common with Galileo. Photograph: Tarker/Tarker/Corbis

And it opens with the following paragraph:

Those who reject the 97% expert consensus on human-caused global warming often evoke Galileo as an example of when the scientific minority overturned the majority view. In reality, climate contrarians have almost nothing in common with Galileo, whose conclusions were based on empirical scientific evidence, supported by many scientific contemporaries, and persecuted by the religious-political establishment. Nevertheless, there’s a slim chance that the 2–3% minority is correct and the 97% climate consensus is wrong.

Now it is true that climate change denialists, like denialists in many other areas of scientific consensus, commonly use what is now known as the Galileo Gambit. This involves claiming in some way that Galileo was persecuted for his theories, although he was proved right in the long run. Implying that the denialist will also be proved right in the long run and hailed as another Galileo. Bob Dylan provided the perfect answer to the Galileo Gambit in his song Bob Dylan’s 115th Dream way back in 1965.

I said, “You know they refused Jesus, too”

He said, “You’re not Him

I would not object to the author’s comments on the contrarians misuse of the name of Galileo if her his comment had stopped at, climate contrarians have almost nothing in common with Galileo, however she he goes on to spoil it with what follows.

Although Galileo’s views on heliocentrism, and that is what stands to discussion here, had their origins in empirical observations made with the telescope he unfortunately did not stop there and they were not supported by a consensus of his contemporaries by any means. In fact at the time of Galileo’s trial by the Catholic Church the majority of astronomers qualified to pass judgement on the subject almost certainly rejected heliocentricity, most of them on good scientific grounds.

In his Dialogo, the book that caused his downfall, Galileo knew very well that he did not have the necessary empirical facts to back up the heliocentric hypothesis and so he resorted to polemic and rhetoric and brought as his pièce de résistance, his theory of the tides, which was fatally flawed and contradicted by the empirical evidence even before it hit the printed page.

Although it became largely accepted by the experts by around 1670, the necessary empirical evidence to substantiate heliocentricity didn’t emerge until the eighteenth and in the case of stellar parallax the nineteenth centuries.

I have written about this historical misrepresentation of Galileo’s position on various occasions and I don’t intend to repeat myself in this post. However anybody who is interested can read some of my thoughts in the post collected under the heading, The Transition to Heliocentricity: The Rough Guides. I also strongly recommend Christopher M. Graney’s recently published Setting Aside All Authority: Giovanni Battista Riccioli and the Science against Copernicus in the Age of Galileo, my review of which should, hopefully, appear here in the not to distant future.

Addendum: Seb Falk has pointed out that Dana Nuccitelli is a he not a she and I have made the necessary corrections to the text. I apologise unreservedly to Mr Nuccitelli for this error.

[1] h/t to Seb Falk (@Seb_Falk) for drawing my attention to this latest misstatement of Galileo’s scientific situation.


Filed under History of Astronomy, Myths of Science

Made in Nürnberg

In the period from roughly 1550 and 1650 Nürnberg was the leading centre in Europe, and thus probably the world, for the manufacture of scientific instruments. It is historically interesting to look at how this town in the middle of Europe came to acquire this status and also to take a brief look at some of the more famous of the Nürnberger instrument makers from this ‘golden’ period.

Like many European towns and cities, Nürnberg, as an entity, began to emerge at the beginning of the High Middle Ages, probably around the year 1000 CE. Like many such settlements it was initially not much more than a fortified hill top at a crossroads. The first record of the name is 1050 CE as nuorenberc, which later evolved into Nuremberg, the name by which it is still known in English. This name is the subject of a rare German bad pun; the Germans don’t really go in for puns. According to folk etymology the name was originally ‘Nur einem Berg’, which translates as ‘just a hill’. The geographical position of Nürnberg played an important role in its development. If you take an outline map of Europe and draw a straight line from Kiel, in Northern Germany, to Northern Italy and a second one from Paris to Prague, the point where they cross is Nürnberg. This led to Nürnberg becoming a major European trading hub in the medieval period; importing wares from the Northern Italian trading cities and then distributing them throughout Europe.

Germany didn’t exist as a country in the Middle Ages but was a loose conglomerate of large and small states interconnected through a network of feudal obligations and vaguely held together in the so-called Holy Roman Empire, which as somebody once quipped was neither holy nor Roman nor an empire. Within this patchwork of large and small Germanic states Nürnberg was one of the so-called Free Imperial Cities, small independent city-states, which only owed feudal allegiance to the Holy Roman Emperor. From 1105 CE Nürnberg was ruled by a hereditary Burggraf, a title that translates as Lord of the castle. From 1192 till 1427 the Burggrafen of Nürnberg came from the Hohenzollern family, who would go on to play a significant role in German history. In 1427 the rich traders of Nürnberg, of whom more shortly, bought the Burggraf rights from the Hohenzollern and from then on until 1806, when Nürnberg became part of Bavaria, the city was ruled by the town council. Although dominated by the rich trader families the town council was surprisingly democratic with three groups of councillors being appointed/elected from the three tiers of citizenry at regular intervals. During the Renaissance Nürnberg, like one of its major trading partners Venice, called itself a republic.

The Holy Roman Emperor granted the city of Nürnberg special tax privileges, which combined with its favourable geographical position and the large Europe wide demand for the spices that came into Europe through the Northern Italian trading cities meant that the Nürnberg traders became very, very wealthy. This led to them looking for new opportunities to invest their surplus profits. The High Middle Ages saw a steeply rising demand for metals (gold, silver, copper, lead, iron) and with it an expansion of the metal ore mining industry. The major ore deposits, and thus the mines, were situated in the eastern part of Middle Europe, Eastern Germany, Hungary, Rumania, Austria etc. Realising that it was an expanding business with a future the Nürnberg traders began investing in the metal ore mines and soon controlled a large part of this industry. At first content just to sell the ore they soon realised that they could make more profit if they smelted the ore themselves and so built their own smelters and began selling refined metal. It did not take long before the artisans of Nürnberg began to work the metal themselves producing finished metal objects for sale. By the fifteenth century Nürnberg had become one of the major metal working centres of Europe producing quite literally everything that could be made from metal from pins and needles to suits of armour. A sign of this development is that the first mechanical wire drawing machine was developed in Nürnberg. The Nürnberg guilds were incredibly well organised with single families responsible for the production of one object or group of objects. When Karl V (Holly Roman Emperor 1519–1556) ordered 5000 suits of armour from Nürnberg, one group of families was responsible for the leg plates, another for the breast plates and so on. Highly organised piecework.

Nürnberg as depicted in the Nuremberg Chronicles 1493

Nürnberg as depicted in the Nuremberg Chronicles 1493

Of course many scientific instruments are made of metal, mostly brass, and so Nürnberg in its all inclusiveness became a major centre for the manufacture of all types of scientific instruments. In fact it became the leading European centre for this work and thus, most probably, the leading world centre in the fifteenth and sixteenth centuries. We have two important historical attestations of Nürnberg’s supremacy in this area. The philosopher Nicholas of Cusa (Cusanus) (1401–1464) was very interested in astronomy and he purchased a celestial globe and other astronomical instruments from Nürnberg and this can still be viewed in the Cusanus Museum in his birthplace Kues. In 1470 when Johannes Regiomontanus set out to reform and modernise astronomy he moved from Budapest to Nürnberg because, as he tells us in a letter, Nürnberg had a good communications network through which he could communicate with other astronomers and because the best astronomical instruments were manufactured in Nürnberg. The communications network was an essential element of any Renaissance trading city and Nürnberg’s was second only to that of Venice.

By 1500 Nürnberg was the second biggest German city with a population of around 40 000, half of which lived inside the city walls and the other half in the surrounding villages, which belonged to the city. It was one of the richest cities in the whole of Europe and enjoyed a high level of culture, investing both in representative architecture and the arts, with many of the leading German Renaissance artists fulfilling commissions for the rich Nürnberg traders, known locally as the Patrizier; most famously Albrecht Dürer. Interesting in our context, Dürer’s maths book contained the first printed instructions in German of how to design and construct sundials. The first half of the sixteenth century was the golden age of scientific instrument production in Nürnberg with many of the leading instrument makers selling their wares throughout Europe, where they can still be found in museums in many different countries. In what follows I shall give brief sketches of a couple of the more well known of these craftsmen.

Nürnberg was famous for it’s portable sundials with family dynasties producing high quality products over three, four or even five generations. At the beginning of the sixteenth century the most significant sundial maker was Erhard Etzlaub (ca. 1460–1532) who like many other Nürnberger instrument makers was as much as a scholar as an artisan. As a cartographer he produced the first map of the Nürnberg region. He followed this with the so-called Rome pilgrimage map displaying the routes to Rome for the Holy Year of 1500, which famously Copernicus also attended. This map plays an important role in the history of modern cartography because it’s the first map with a scale, enabling the pilgrim to plan his daily journeys.

Etzlaub's Rome Pilgrim Map Source: Wikimedia Commons

Etzlaub’s Rome Pilgrim Map
Source: Wikimedia Commons

Etzlaub also constructed a map on the cover of one of his compasses in 1511 that is drawn in a projection that comes close to the Mercator projection. Etzlaub was a member of the so-called Pirckheimer Circle. A group of like minded proponents of the mathematical sciences centred around Willbald Pirckheimer, soldier, politician humanist scholar and translator from Greek into Latin of Ptolemaeus’ Geographia; a translation that became a standard work.

Willibald Pirckheimer, porträtiert von Albrecht Dürer (1503) Source: Wikimedia Commons

Willibald Pirckheimer, porträtiert von Albrecht Dürer (1503)
Source: Wikimedia Commons

This group of mathematical scholars demonstrated their interest in the mathematical sciences and in the construction of complex instruments in the highly complex sundial that they painted on the side of the Lorenzkirche in 1502, which also displays the time according to the Great Nürnberger Clock:

Lorenzkirche Sundial Source: Astronomie in Nürnberg

Lorenzkirche Sundial
Source: Astronomie in Nürnberg

And the clock on the Frauenkirche constructed in 1506:

Frauenkirche Clock

Frauenkirche Clock

The gold and blue ball above the clock dial displays the phases of the moon and is still accurate today.

Another member of the Pirckheimer Circle was Johannes Schöner(1477–1547), addressee of Rheticus’ Naratio Prima, the first published account of Copernicus’ heliocentrism.

Johannes Schöner Source: Wikimedia Commons

Johannes Schöner
Source: Wikimedia Commons

Schöner was the first producer of serial production printed globes both terrestrial and celestial. He also wrote, printed and published pamphlets on the design and manufacture of various scientific instruments. Schöner was Europe’s leading globe maker whose globes set standards for globe making, which influenced the manufacture of globes down to the nineteenth century.

Schöner Celestial Globe 1535 Source: Science Museum London

Schöner Celestial Globe 1535
Source: Science Museum London

Also a member of the Pirckheimer Circle and a close friend of Schöner’s was Georg Hartman (1489–1564).

Georg Hartmann Source: Astronomie in Nürnberg

Georg Hartmann
Source: Astronomie in Nürnberg

Hartmann like Schöner was a globe maker although none of his globes have survived. He was also one of the leading sundial makers of his generation and his complex and beautiful dials can still be found in many museums.

Hartmann Bowl Sundial Source: Wikimedia Commons

Hartmann Bowl Sundial
Source: Wikimedia Commons

In the early sixteenth century Nürnberg was the main European centre for the production of astrolabes and here Hartmann played a leading role. As far as can be ascertained Hartmann was the first person to produce astrolabes in series.

Hartmann Astrolabe Yale Source: Wikimedia Commons

Hartmann Astrolabe Yale
Source: Wikimedia Commons

Previously all astrolabes were produced as single pieces, Hartmann, however, produced series of identical astrolabes, probably employing other craftsmen to produce the individual parts according to a pre-described plan and them assembling them in his workshop. As a young man Hartmann had spent several years living in Italy where he was friends with Copernicus’ brother Andreas. As a scholar Hartmann was the first to investigate magnetic inclination or dip. However his studies were never published and so the credit for this discovery went to the English mariner Robert Norman.

Handmade metal instruments were, of course, very expensive and could in reality only be purchased by the wealthy, who often bought them as ornaments of status symbols rather than to be used. To make scientific instruments available to those with less money both Schöner and Hartmann produced paper instruments. These consisted of the scales and tables, normally found engraved on the metal instruments, printed accurately on paper, which the user could then paste onto a wooden background and so construct a cheap but functioning instrument.

Paper and Wood Astrolabe Hartmann Source: MHS Oxford

Paper and Wood Astrolabe Hartmann
Source: MHS Oxford

A later instrument maker was Christian Heiden (1526–1576) who like Schöner was professor for mathematics on the Egidiengymnasium in Nürnberg, Germany’s first gymnasium (similar to a grammar school). He made a wide range of instruments but was especially well known for his elaborate and elegant sundials, as much works of art as scientific instruments these were much prized amongst the rich and powerful and could be found on many a German court.

Column Sundial by Christian Heyden Source: Museumslandschaft Hessen-Kassel

Column Sundial by Christian Heyden
Source: Museumslandschaft Hessen-Kassel

This is of course only a very, very small sample of the Nürnberger instrument makers, the history pages of the Astronomie in Nürnberg website, created and maintained by Dr Hans Gaab, lists 44 globe makers, 38 astronomical instrument makers and more than 100 sundial makers between the fifteenth and nineteenth centuries; with the greatest concentration in the sixteenth century. Nürnberg was known throughout Europe for the quality and the accuracy of its scientific instruments and examples of the Nürnberger handwork can be found in museums in many countries, even outside of Europe.


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

Sorry Caroline but Maria got there first!

Astronomer Caroline Herschel observed her first comet on 1 August 1786 an anniversary that was celebrated by various people on Twitter yesterday. Unfortunately many of them, including for example NASA History Office (@NASAhistory), claimed that on this date she became the 1st woman to discover a comet. This is quite simply not true.

Maria Margarethe Kirch (née Winkelmann), the wife of Gottfried Kirch the Astronomer Royal of Berlin, discovered the comet of 1702 (C/1702 H1) on 21 March 1702 that is forty-eight years before Caroline Herschel was born. Unfortunately the discovery was published by her husband and it was he who was incorrectly acknowledged as the discoverer. In 1710 Gottfried admitted the error and publically acknowledged Maria as the discoverer but she was never official credited with the discovery.

Both Maria Kirch and Caroline Herschel were excellent astronomers with much important work to their credit. However credit where credit is due, Caroline was not the first woman to discover a comet, Maria was.


Filed under History of Astronomy, Myths of Science

σῴζειν τὰ φαινόμενα, sozein ta phainomena

For all those, who like myself, can’t actually speak or read ancient Greek the title of this post is a phrase well known in the history of astronomy ‘saving the phenomena’, also sometimes rendered as ‘saving the appearances’. This post is in response to a request that I received from a reader asking me to explain what exactly this expressions means.

The phrase saving the phenomena was first introduced into the history of astronomy discourse by the late nineteenth-century and early twentieth-century French physicist and historian of science, Pierre Duhem. Duhem used the expression in the title of his work on physical theory Sauver les Phénomènes. Essai sur la Notion de Théorie Physique de Platon à Galilée, (1908), which was translated into English in 1969, as To Save the Phenomena, an Essay on the Idea of Physical Theory from Plato to Galileo. In this work Duhem argued that all mathematical astronomy from Plato up to Copernicus consisted of mathematical models designed to save the phenomena and were not considered to represent reality. The phenomena that needed to be saved were the so-called Platonic axioms, i.e. that the seven planets (Mercury, Venus, Moon, Sun, Mars, Jupiter and Saturn) move in circles at a constant speed. It is fairly obvious that the planets do not move in circles or at a constant speed thus posing a difficult problem for the mathematical astronomers, in order to save the phenomena they have to present a mathematical model, which can account for the apparent irregularity of planetary motions in the form of a more fundamental real regularity.

Duhem’s thesis suffers from several historical problems. He bases his argument on a quote from Simplicius’ On Aristotle, On the Heavens, which dates from the sixth century CE. According to Simplicius Plato challenged the astronomers to solve the following problem:

“…by hypothesizing what uniform and ordered motions is it possible to save the phenomena relating to planetary motions.”[1]

Simplicius goes on to say:

“In the true account the planets do not stop or retrogress nor is there any increase or decrease in their speeds, even if they appear to move in such ways … the heavenly motions are shown to be simple and circular and uniform and ordered from the evidence of their own substance.”

Simplicius attribution of the concept of saving the phenomena to Plato is made more than nine hundred years after Plato lived. In fact there is no mention in the work of Plato of the principle of uniform circular motion, the earliest known example being in Aristotle. The earliest example of the phrase ‘saving the phenomena’ occurs in Plutarch’s On the Face in the Orb of the Moon, from the first century CE and does not refer to planetary motions but to Aristarchus’ attempt to explain the revolution of the sphere of the fixed stars and the movement of the Sun through heliocentricity.

We find some support for the view of Simplicius in the introduction to astronomy of Geminus of Rhodes in the first century BCE, although he doesn’t use the explicit phrase to save or saving the phenomena, he writes:

“For the hypothesis, which underlies (hupokeitai) the whole of astronomy, is that the Sun, the Moon, and the five planets move circularly and at constant speed (isotachôs) in the direction opposite to that of the cosmos. The Pythagoreans, who first approached such investigations, hypothesized that the movements of the Sun, Moon, and the five wandering stars are circular and uniform … For this reason, they put forward the question: how would the phenomena be accounted for (apodotheiê) by means of uniform (homalôn) and circular motions.”

As we can see Geminus attributes the concept of uniform circular motion to the Pythagoreans and not Plato. It should be pointed out that neither Simplicius nor Geminus was a mathematical astronomer.

Duhem also claimed that the most significant of all Greek astronomers, Ptolemaeus, adhered to the principle of saving the phenomena in his Syntaxis Mathematiké, the only substantial work of Greek mathematical astronomy to survive. However a careful reading of Ptolemaeus clearly shows that he regarded his models as representing reality and not just as saving the phenomena.

The most famous case of saving the phenomena can be found in Andreas Osiander’s Ad lectorum (to the reader) appended to the front of Copernicus’ De revolutionibus. In this infamous piece Osiander, who had seen the book through the press writes:

For it is the duty of an astronomer to compose the history of the celestial motions through careful and expert study. Then he must conceive and devise the causes of these motions or hypotheses about them. Since he cannot in any way attain the true causes, he will adopt whatever suppositions enable the motions to be computed correctly from the principles of geometry for the future as well as the past. The present author has preformed both these duties excellently. For these hypotheses need not to be true nor even probable. On the contrary, if they provide a calculus consistent with the observations that is enough. [2]

As can be clearly seen here Osiander is suggesting to the reader that Copernicus’ work is just a mathematical hypothesis and thus need not be regarded as mirroring reality. It is clear from the rest of his text that Osiander is trying to defuse any objections, religious or otherwise, that Copernicus’ heliocentricity might provoke. Of course his claims stand in contradiction to Copernicus’ text where it is obvious that Copernicus believes his system to reflect reality. Because Osiander’s Ad lectorum was published anonymously, it was assumed by many people that it was written by Copernicus himself a confusion that was only cleared up at the beginning of the seventeenth century.

It is not clear whether Osiander was appealing to a two thousand year old tradition of saving the phenomena, as Duhem would have us believe, or whether he, and possibly Petreius the publisher, had devised a strategy to avoid censure of the book and Copernicus’ radical idea.

Although many people continue to quote it as a historical fact it is highly doubtful that Duhem’s thesis of the saving of the phenomena ruling mathematical astronomy for the two thousand years from Plato to Galileo is true and it is fairly certain that most if not all mathematical astronomers, like Ptolemaeus, believed the models that they devised to be true representations of reality.


[1] This and all other quote from the Greek are taken from Mark Schiefsky, “To save the phenomena” and curve fitting” (pdf)

[2] On The Revolutions, translation and commentary by Edward Rosen, The Johns Hopkins University Press, Baltimore and London, pb., 1992, p. XX


Filed under History of Astronomy

For those who haven’t been paying attention

Galileo Galilei was found guilty and sentenced by the Inquisition on 22 June 1633; as usual this anniversary has produced a flurry of activity on the Internet much of it unfortunately ill informed. This is just a very brief note for all those who haven’t being paying attention.

The crime of which Galileo was found guilty was “vehement suspicion of heresy” and not heresy. This might appear to some to be splitting hairs but within the theological jurisdiction of the Catholic Church the difference is a highly significant one. Had the Inquisition found him guilty of heresy then a death sentence would have followed almost automatically. As they only found him guilty of the lesser charge “vehement suspicion of heresy” it was possible for him to be sentenced to life in prison commuted the next day to house arrest.

And please Richard Coles, and anybody else stupid enough to quote it, the claim that he said Eppur si muove (and yet it moves) upon being sentenced is almost certainty a myth.


Filed under History of Astronomy, Myths of Science

Teaching the Revolution.

Anthony Millevolte is professor for chemistry at the University of Wisconsin Colleges where he also teaches the history of science courses. When he was teaching an introductory course on the so-called Copernican or Astronomical Revolution he realised that there was no suitable modern textbook available for such a course so he decided to write one: The Copernican Revolution: Putting the Earth into Motion.[1] His resolve to do so was strengthened when he realised that some people wee still teaching such courses using Thomas Kuhn’s The Copernican Revolution from 1957. He writes, “As well written as it is, the obviously unavoidable weakness of Kuhn’s text is that it doesn’t reflect over a half century of active scholarship in this field”[2]. Being somewhat less diplomatic than Millevolte I would add that Kuhn’s book was flawed in some aspects in 1957 and those flaws haven’t improved in the almost sixty years since.


Millevolte’s book is exactly what he set out to write an introductory textbook for college students on the developments in European astronomy in the sixteenth and early seventeenth centuries centred on the period between Copernicus and Galileo. Having above referred to the so-called Copernican Revolution I should point out that Millevolte doesn’t believe in a revolution either, as he explains in the final chapter of the book, An Epilogue, but uses the term in his title because it “reflects a long-standing historical convention – not because it accurately summarizes a series of events that unfolded over many centuries”[3].

The first three chapters could be summarized as setting the scene, giving a quick survey of European astronomy prior to the Renaissance. Consisting of only eight-two pages they don’t offer much depth but however cover all of the salient points clearly and accurately. All the chapters of the book have excellent endnotes and these contain references to the extensive bibliography helping any reader who wishes to pursue any given topic further.

The fourth chapter is devoted to Renaissance astronomy and Copernicus and contains one of the few minor criticisms that I have of the book. In his biographical sketch of Copernicus Millevolte makes some errors only significant to a pedant like me, which however could profitably corrected in a second edition. Otherwise this like all the other chapters in the book is clearly presented and the history of science is as far as it goes correct.

In his introduction Millevolte says that in the process of writing he realised why nobody had written such an up to date textbook. He writes, “It turns out that the experts disagree on a good many of the central elements of the story – so much so that it is sometimes challenging to identify an acceptable narrative”[4]. On this point I agree with him so one should bear this in mind when considering any criticism that I might make here. Despite this problem throughout the book Millevolte had managed to produce a clear, coherent narrative suitable for beginners. On those points that are contentious he includes clearly written, extensive endnotes, which list alternative viewpoints, thus managing very successfully to have his cake and eat it, too.

Having set the astronomical revolution in motion Millevolte produces one chapter each on Tycho Brahe and Kepler and three on Galileo. Here I would complain that the balance is false as Kepler contributed far more to the astronomical revolution than Galileo. However the traditional narrative always favours Galileo over Kepler and as this is a college textbook Millevolte stays within the tradition. He does however redress the balance somewhat in the final chapter where he attributes equal weight to Kepler and Galileo in establishing heliocentricity. I still think this gives too much credit to Galileo but it is it is better than the standard mythology that gives almost all the credit to Galileo and almost none to Kepler.

In his chapters on Galileo Millevolte also tend to emphasise positive aspects of Galileo’s activities oft by simply omitting the negative. For example whilst discussing the dispute between Galileo and Orazio Grassi concerning comets, that led to Galileo writing Il Saggiatore, whilst conceding that Galileo’s attacks on Grassi were, to say the least, immoderate Millevolte neglects to mention that on the question of whether the comets were sub- or supralunar Grassi was in the right and Galileo very much in the wrong.

The same subject turns up in the discussion of the third day in the Dialogo, which is devoted amongst other things to the novas and that they were supralunar. Millevolte claims that Galileo devoted space to this theme because “there remained many Aristotelians who refused to believe the novas were located beyond the sphere of the moon”[5]. This may well have been but the Jesuit, who were without doubt the leading geocentric astronomers, had already accepted the supralunar status of the novas in the sixteenth century. Galileo is here flogging the proverbial dead horse. Again not mentioned by Millevolte, who in general fails to make the important distinction between Aristotelian cosmology and Ptolemaic and/or Tychonic astronomy; a distinction that played a central and significant role in the gradual acceptance of heliocentricity. Geocentric astronomers were prepared to abandon Aristotelian cosmology when the evidence showed it to be wrong but not to give up geocentric astronomy without clear evidence against it and for heliocentricity.

Concerning day four of the Dialogo, Millevolte fails to mention that Galileo’s much favoured theory of the tides was in fact refuted by the empirical facts.

All of the above points whilst, in my opinion important, are for an introductory text not absolutely essential and should not be thought to lead to a negative assessment of Millevolte’s book.

The closing chapter of the book delivers a brief but very clear assessment of the further progress towards heliocentricity up to and including Isaac Newton. As already mentioned the book has an extensive bibliography and the endnotes to each chapter deal skilfully with many of the historically contentious points in the story. I personally would have welcomed an index. The book is attractively illustrated with black and white pictures and diagrams.

Taken as a whole Millevolte has fulfilled his original resolve extremely well and what we have here is a first class up to date textbook on one of the most important episodes in the history of astronomy. I would heartily recommend this book to anyone who wishes to read an introductory text on the subject to inform and educate themselves and especially to anyone wishing to teach an introductory course on the subject to college students or even to the upper classes/grades of grammar schools, high schools etc. Currently priced at circa $17 US on most students should be able to afford a copy.


[1] Anthony Millevolte, The Copernican Revolution: Putting the Earth into Motion, Tuscobia Press, 2014.

[2] Millevolte, p. iv

[3] Millevolte, p. 294

[4] Millevolte, p. v

[5] Millevolte, p. 270


Filed under Book Reviews, History of Astronomy, Uncategorized

Asterisms and Constellations and how not to confuse them with Tropical Signs.

If you are going to write about something, especially if you intend to lay bare somebody else’s ignorance, it pays to actually know what you are talking about otherwise you could well end up looking like a total idiot, as does Anna Culaba in her article on the RYOT website, The Stars and Your Astrological Signs Have Been Lying to You This Whole Time. I should point out that Ms Culaba is by no means the first person to publically embarrass themselves pontificating on this subject, in fact it’s a reoccurring theme much loved by scientists and science fans who want to take a cheap shot at astrology. Indeed, as we will see later Ms Culaba, in her article, is in fact just regurgitating the content of a BBC website. So what exactly does our intrepid science fan say in her blog post?

My horoscope for today (I’m a Virgo) according to reads, “Today, explore an aspect of an unfamiliar religion or culture. Today is a day to make plans and aim high.” There are only two things that are keeping me from leaving work right now: one, I don’t really believe that the stars can determine what will happen in my life and two, I wasn’t really born under the star sign that the world told me I was born into. According to the BBC, about 86 percent of people are actually born under a different sign than the one they think. This is because 2,000 years ago, when the Ancient Greeks first created the zodiacs, the star signs corresponded to the position of the sun relative to the constellations that appeared in the sky the day people were born. Unfortunately, during that time people didn’t know of the phenomenon known as the precession. Live Sciences reports that the precession is when the Earth continually wobbles around its axis in an almost 26,000-year cycle thanks to the gravitational attraction of the moon. Thanks to this phenomenon, the constellations some people live and die by have actually drifted away from us. This means that constellations are now actually off by a month. So if you were born between August 11 to September 16 you’re not the picky and critical Virgo that you thought you were — you’re really an ambitious Leo whose strength of purpose allows you to accomplish many, many things. And if you’re astrological world hasn’t been rocked enough, if you thought you had your star sign wrong, wait until some of you realize that there’s actually a 13th zodiac sign known as the Ophiuchus. According to the BBC, the Ancient Greeks deliberately left out the original zodiac so that ancient astrologers would be able to divide the sun’s 360 degree path into 12 equal parts. Where does Ophiuchus fit into the zodiac calendar? It goes between Scorpio and Sagittarius, so if you were born between November 30 and December 18 consider yourself an Ophiuchus. You’re probably very secretive and good at hide and seek.

I have reproduced the whole of Ms Culaba’s screed here to save me having to quote it in little bits, merely removing the links from the original. If you read it through you what will discover is the central claim that astrologers were too stupid to realise the astronomical phenomenon of precession and so you were not actually born under the star sign that they claim you were. There are two general points to be made here, firstly astrologers were well aware of precession and secondly Ms Culaba and the source she is quoting don’t know the fundamental difference between constellations and tropical signs. So for the benefit of Ms Culaba and all others who are confused by the topic we will have a Renaissance Mathematicus guide to asterisms, constellations, the zodiac and tropical signs.

If you go out on a dark night with a clear sky in an area with little or no light pollution (and if you have never done so you should, it’s awesome) and look up in the heavens you will see a myriad of stars looking down on you in a vast blue black vault. If you are not a trained astronomer you will probably find no means of orienting your gaze in this confusion of twinkling lights. This problem was confronted by all human cultures since the dawn of human existence. The human brain seems to be programmed for pattern recognition and so, like children with a join up the dots picture book, all cultures started to create pictures by imagining lines joining up or outlining eye-catching groups of stars and giving these pictures names. These pictures, and they exist in all human cultures, are known technically as asterisms. These asterisms help the observing eye gain orientation when traversing the vast dome of the night sky and early astronomers started compiling lists of the most prominent such join-up-the-dots-pictures or asterisms in order to use them as a scaffolding for mapping the heavens. Those asterisms contained in such formal lists are called constellations. Our modern, western list of constellations has its origins in ancient Babylonian astrology/astronomy and comes down to us via the ancient Greeks and the medieval Islamic astronomers. In his Syntaxis Mathematiké, Ptolemaeus lists 48 constellations by name. Currently, the International Astronomical Union (IAU) recognises 88 named constellations. We now need to turn our attention to the origins of the zodiac.

Viewed from the earth, and before the beginning of the so-called space age that was the only way possible to view the heavens, the sun appears to orbit the earth once every year. In fact the year is defined as the time it takes for the sun to orbit the earth. The path the sun follows on its way around the earth is called the ecliptic and is tilted at approximately 23 degrees to the earth’s equator. This tilt, known as the obliquity of the ecliptic, is the reason why we have seasons on the earth. The six planets visible to the naked eye and know in antiquity – Moon, Mercury, Venus, Mars, Jupiter and Saturn – all appear to orbit the earth in the plane of the ecliptic making this imaginary belt around the heavens very important for the study of astronomy. The earliest known mapping of the ecliptic is contained in a set of Babylonian clay tablets known as the MUL.APIN, which date from around 1000 BCE. Here the path of the moon’s orbit is described or mapped with 17 or 18 (the text is somewhat ambiguous) constellations and stars. The moon’s orbit is tilted at about five degrees to the ecliptic. This mapping was still in use around 700 BCE. By around 500 BCE the 17/18 constellations/stars had be replaced by twelve constellations of varying sizes. Circa 420 BCE the Babylonians had replaced those twelve constellations with twelve equal divisions of the ecliptic comprising 30° segments. These segments were named after the constellations they replaced and form the zodiac that was taken over by the Greeks and made its way down to us. Those segments are known technically as tropical or sun signs, form the basis of zodiacal astrology and are abstract geometrical segment of the ecliptic and not constellations. The constellations slowly circle the heavens due to precession, the tropical signs do not! If an astrologer says you were born under the sign Virgo it means that the sun was in the 30° segment of the ecliptic that bears the name Virgo at the moment of your birth. This has nothing apart from the name in common with the constellation Virgo.

It is not the astrologers who display ignorance of the precession of the equinox, to give the phenomenon its full name, but Ms Culaba who displays total ignorance of both astronomy and astrology. This is not a very good situation to be in if you are going to write about the history of science and yes we are talking about the history of science here, the zodiac with its tropical signs was originally conceived for astronomical purposes. Ms Culaba might be excused because she did not originate this particular piece of history of science rubbish but is merely regurgitating false information from what she obviously thought was a reliable source, the BBC.

Here we have the presenter of Stargazing Live, a high prestige BBC science programme, Dara O Brian presenting the world with high-grade bullshit under the BBC’s banner. O Brian and his co-presenter Brian Cox should know better and I find it a total disgrace that the fee payers money is being wasted on such rubbish under the guise of educational television, both the presenters and the Beeb should be thoroughly ashamed of themselves.


Filed under History of Astrology, History of Astronomy, Myths of Science