This is going to be a book review and it is not going to be a nice one and I am definitely not going to be recommending this book. Not for the first time I have to serious ask why publishers don’t employ fact checkers and in this case whether the prominent authors, who glowing recommend this book in blubs on the cover, actually read the book before writing those blurbs.
The book in question is Our Moon: A Human History by Rebecca Boyle[1] and has the following glowing celebrity endorsements:
Chris Hadfield, the astronaut: This book is a must-read for anyone who has looked up at the Moon in wonder.
Lewis Dartnell, author of Being Human: This is a beautiful evocative hymn to the intimate connection we have shared with our planet’s cosmic companion.
Rebecca Wragg Sykes, author of Kindred: Glinting with intriguing facts and fascinating connections.
Ed Yong, author of An Immense World: A riveting feat of science writing, which recasts that most familiar of celestial objects into something eerily extraordinary, pivotal to our history, and awesome in original sense of the world. I learned so much.
Peter Brannen , author of The Ends of the World: With a remarkable command of planetary science and human history Boyle provides a sweeping, lyrical new account of our comic neighbour…
Neil Shubin, author of Your Inner Fish: Rebecca Boyle’s Our Moon will change how you think about our planet, the Moon, and ourselves.
With the exception of Ed Yong, these are just extracts of the effusive praise these worthies pour out over this book. That, when it comes to the history of astronomy, a central element of any study of the Moon, the book is factual disaster area seems to escape the attention of all of these expert science writers. I asked my friend the HISTSCI_HULK what he would have done if he had got a manuscript of just the history of astronomy elements of this book to fact check and he answered.
Hulky: I would have picked it up with a pair of tongs with my right hand, whilst holding my nose closed with my left hand and flushed it down the sewer, where stinking excrement belongs.
I had intended to write a review of the whole book, as there are some good parts but also some other aspects that disturbed me, her treatment of archaeoastronomy for example, but didn’t want to end up with another twelve-thousand word review, so I have decided only to tackle the disastrous history of astronomy elements of the book.
Having presented a very long, rather bizarre and very one sided account of Babylonian astronomy, she concentrates almost entirely on the moon goddess cult of the last Neo-Babylonian King Nabonidus (c.620 – after 522 BCE), ignoring to a large extent the previous more that two-thousand years of Babylonian astronomical history and all the other planetary deities they worshiped over this time she dismisses the Babylonian astronomers as astrologers, earlier she refers to them as sky priests, Boyle now wants to tell us that the first to have the concept of modern science was the pre-Socratic philosopher Anaxagoras (c. 500–c. 428 BCE). Historians of astronomy think that Babylonian astronomy was scientific in the modern sense!
Before turning to Boyle’s adoration of Anaxagoras, her chapter on Nabonidus’ moon cult closes with a real gem: “Nearly 2,500 years had gone by since the people of Mesopotamia invented religion.” Really, the people of Mesopotamia invented religion? Does she mean developed their religion, which would be an acceptable statement or that they were the first to have a religion at all, which would be pure poppycock.
She also claims that:
“Now the Persians, conquers of Babylon [took place in 540 BCE] were the leading experts on the daily and nightly happenings above. They made the most advanced measurements of the heavens any humans had achieved yet. Their astrological omen tablets show a detailed understanding of the Moon’s motions, eclipses the movements of planets and stars through the constellations [stars move through the constellations!?] and how the Moon interacted with them. These astronomers–or call them astrologers, their goal was the same–gave us the signs of the zodiac that we still use today, dividing the sky into twelve zones and assigning each section with the name of the most prominent constellation within it.”
The astronomer-astrologers she is describing were not Persians but Babylonians living under Persian rule. The zodiac does not divide up the sky but the ecliptic, the apparent path of the Sun around the Earth. It evolved over a long period of time. The earliest known version occurs in the MUL.AlPIN, two clay tablets from the 7thcentury BCE but content dates back to at least one thousand BCE and probably much further. Here it is seventeen constellation that actually map the path of the Moon. Over time it was reduced to twelve constellation and became the map of the ecliptic.
She then describes the Babylonian discovery of the Soros cycle of lunar and solar eclipses, which is, of course, a perfect example of empirical science.
She writes here: “Before paper, before pen, before what we what we would consider arithmetic, Babylonian astronomers counted out what we now call the Saros cycle.”
The Babylonians had a perfectly good system of writing and recording with their Cuneiform script and their clay tablets, so didn’t need paper and pen. In fact baked clay tablets conserve better than paper, which is why we know as much about the Babylonians as we do. Not only did they have what we consider arithmetic, they also had a fairly advanced knowledge of algebra, including the general solution of the quadratic equation, albeit only for positive values. They also used algebraic algorithms to accurately track the orbits of the planets, as well as to predict lunar and solar eclipses.
When we get to Anaxagoras, Boyle’s Persia obsession goes totally overboard:
A twenty-two-year-old Persian refugee named Anaxagoras wrote down what he saw, determined to find out more about where the eclipse shadow fell.
Anaxagoras was from Ionia, across the Aegean Sea from Greece in what is now Turkey, and arrived in Athens in 480 B.C.E. during the Greco-Persian Wars. He came from the great Persian tradition of sky-watching and brought a distinctly Persian spirit of scientific enquiry to his adopted city where he probably travelled as a war veteran or refugee.
Anaxagoras came from Clazomenae, an Anatolian Ionic city, which was at the time under the control of the Persian Empire but he was not Persian, he was an Ionian Greek. There was no great Persian tradition of sky-watching and what he brought to Athens was the Ancient Greek, Ionian school of pre-Socratic philosophy.
Boyle singles out Anaxagoras (c. 500–c.428 BCE) because, he is said to have been the first to claim that the Moon received its light from the sun, it is also said that Parmenides, who predates Anaxagoras was the first, and also that Aaxagorus said that the Moon was Earthy. Anaxagoras is credited with having given the correct explanation for lunar and solar eclipses. There is a major problem with all of this that for all the Pre-Socratic philosophers we only have very small fragments of any original works and a lot of hearsay. Boyle admits this and writes, “His works were lost in antiquity, and only transmitted to us through other luminaries of philosophy and science, especially Claudius Ptolemy in his opus the Almagest.” Anaxagoras does not feature anywhere in the Almagest, I looked!
A very typical line of transmission of the pre-Socratics is Simplicius (c. 480– c. 540 CE), so a thousand years later than the pre-Socratics, commenting on a lost book by Theophrastus (c. 371–c. 287), so around three hundred years later that Anaxagoras and seven hundred before Simplicius, commenting on a lost pre-Socratic text! Not exactly the most reliable source of evidence.
Boyle thinks that because Anaxagoras made these claims he is the first scientific astronomer. She thinks this view is supported because, “All of Anaxagoras’s unorthodox ideas refuted earlier theories.” She names some of those unorthodox theories such as the Sun is a mass of burning metal and that the planets were burning rocks. What she doesn’t mention is that Anaxagoras believed that the Earth was flat and the shape of a column drum (that’s a segment of a column and not a musical instrument) which was one third as high as its diameter that rested on a bed of air, which prevented it falling. It also seems that during his lifetime people were starting to suggest that the Earth was a sphere and he argued against this. He also thought that the Sun was about the size of the Peloponnese, so about twenty-two thousand square kilometres. Theories about as scientific as the Moon is made of green cheese.
There is much more about Anaxagoras that I will skip and move on to Boyle’s closing statement on him:
A long list of Greeks built on Anaxagoras’s work in their own ways, and their works survive so those scholars are more well known than Anaxagoras now.
As for as his cosmology/astronomy goes there is almost no evidence that anybody built on it. His other philosophical ideas had more impact. The things that he got right were newly recognised or rediscovered over the centuries but nobody said, oh, I got that from Anaxagoras. He along with the other pre-Socratic astronomers, who Boyle doesn’t have time for because they didn’t say anything significant about the Moon, played a role in getting Ancient Greek astronomy rolling but that’s about as far as it goes.
She moves on to Aristotle, having rubbished Plato in less than half a page. She apparently thinks that because “he thought that we should study the mathematical motions of the heavenly bodies, not the motions they appear to make as seen from our limited perspective” he unlike Aristotle is astronomically unscientific.
She introduces Aristotle’s cosmological concept of the sublunar Earth sphere and the supralunar heavenly sphere and calls this Moon-centric. She then writes:
The most important contribution of Aristotle’s Moon-centric cosmology was the idea of astronomy as a scientific discipline.
There is nothing scientific about Aristotle’s cosmology it is pure, unadulterated metaphysics. It is a set of prescriptive rules that the cosmos in his opinion fulfils or should fulfil. Rules that have little or nothing to do with observable, empirical reality. She declares this to be scientific and attributes to Aristotle , following on from Anaxagoras, the scientific study of the heavens, as opposed to the non-scientific activity of the “cultish sky priests tasked with hedging bets for twitchy sovereigns.”
Firstly, in their astronomy, the Babylonian astronomers, her “cultish sky priest”, were far more scientific than anything Aristotle contributed to the discipline. Secondly, the real Greek astronomers were just as much sky priests (astrologers) as the Babylonians, seeking their justification for this in Aristotle’s metaphysical concept of celestial influence; This is the belief that the events in the upper world or celestial sphere influence the events in the lower world or terrestrial sphere. As above so below or macrocosmos–microcosmos, to use the catch phrases.
At the end of this section Boyle writes:
Others would carry this scientific method forward, make their own observations , and ultimately surpass Aristotle’s neatly packed cosmos. The concept of seeking astronomical knowledge for its own sake would power the minds of the most consequential scientists to follow, twenty centuries later: Nicolaus Copernicus, Johannes Kepler, and Galileo Galilei.
All three of her Early Modern astronomers were also, to use her derogatory term, sky priests.
We now get the people were too dumb to realise that we live in a heliocentric system and committed “geocentric blunders.” Without the knowledge that we acquire through our education, everything that we perceive through all of our senses tells quite firmly that we live of a static Earth in a geocentric cosmos. This is not a blunder but our daily reality. The miracle is that a couple of people imagined, not perceived but imagined, it otherwise. Boyle naturally brings Aristarchus of Samos:
At least one ancient Greek figured out the truth, but his works were lost until after Copernicus independently made this realisation a second time. Aristarchus of Samos (310–230 B.C.E.) realised that when the Moon is exactly half full, the angle between Earth, Moon, and Sun will be ninety degrees. He calculated the ratio of the Earth-Moon distance to the Earth-Sun distance and found out the Sun is much more distant than the Moon, though it appears to be the same size in the sky. The monarch of the night is therefore not on a par with the ruler of the day. Aristarchus realised that given these huge sizes and distances, Earth must revolve around the Sun, and not the other way around. But nobody listened to him.
The only known surviving work by Aristarchus, his On the Sizes and Distances (of the Sun and Moon) is written and presented entirely from a geocentric view point. We only know of his heliocentric hypothesis through hear say and it is highly unlikely that he deduced it from the results delivered by On the Sizes and Distances. Both Hipparchus (c. 190–c. 120 BCE) and Ptolemy (fl. 150 CE) used a similar procedure and got even larger values than Aristarchus but neither of them then said, oh, the cosmos is heliocentric!
Boyle then brings up Meton of Athens (fl. fifth century BCE) and the Metonic cycle and that it was introduced into the Attic calendar, making it a lunar-solar calendar. However, she fails to mention that this was only one of numerous Greek calendars in use at the time and all the others remained lunar calendars. There is also the strong possibility that Meton took over the Metonic cycle from the Babylonians, those sky priests.
Next, Boyle delivers a totally mindboggling piece of fake news:
Then in 331, Alexander the Great, a student of Aristotle’s, became the next to conquer Babylon, that great city on the Euphrates. He ordered the Babylonians’ astronomical tables translated into Greek. [my emphasis] The Greeks found a wealth of knowledge within, and Alexander became another in along line of rulers to grasp the immense power that derives from being in charge of time.
When I first read the emphasised sentence, I was totally gobsmacked! Not only is it total and utter ahistorical garbage, I, initially, couldn’t for the life of me imagine where Boyle had acquired this piece of garbage. Did she simply make it up?
Dealing with the historical claim first. The Greek astronomers and astrologers, you know those sky priests, had been using Babylonian astronomical data long before Alexander was even born and one of the puzzles in the history of astronomy is we don’t know who transmitted/translated it. Secondly the Greeks never came close to acquiring all of the Babylonian astronomical tables.
On the question of Boyle’s source for this glaring piece of misinformation, after a couple of days thought the penny dropped. She is misquoting a Sassanian legend. Alexander conquered the first or Achaemenian Empire (550–330 BCE) and the legend about Alexander’s theft of knowledge is from the second or Sassanian Empire (224–651 CE). Plagiarising myself:
The Sassanians had a myth/legend that Zoroaster, the founding prophet of their religion, was, in the Avesta, the Zoroastrian canonical scriptures, the source of all leaning. The Chinese have a similar myth concerning the Yellow Emperor, who is said to have discovered and invented everything. When Alexander conquered Persia he copied all of this leaning had it translated into Greek and sent back to Greece. He then destroyed all traces of it in Persia. Basically, everything from Pythagoras, Euclid, Aristotle et al had been stolen by Alexander from the Persians.
We now get another piece of garbled information:
Working on behalf of Alexander, a fellow student of Aristotle’s named Callippus used the Babylonian records and the knowledge of his Greek predecessors to once again recalculate the length of the lunar month. Callippus proposed a new calendar, which started on June 28, 330 B.C.E., eight months after Alexander captured Babylon.
The new calendar, which all later Greek astronomers used, runs for seventy-six years, or for Meton cycles. After 940 Moon months, at the end of every fourth nineteen-year period, Callippus’s calendar drops a day. This keeps the lunarsolar calendar even better aligned with the seasons of the solar year.
Callippus (c. 370–300 BCE) was a student of Eudoxus of Cnidus (c. 390–c. 340 BCE) and not of Aristotle, although he appears to have later worked with Aristotle. There is no know connection to Alexander, who certainly did not commission his work, which was not a calendar but as Boyle correctly describes, a recalculation of the Metonic cycle. The Callippic cycle was used by some, but by no means all, later Greek astronomers, Hipparchus, for example used his own Hipparchic cycle, an improvement on the Callippic cycle, to give a common basis for dating astronomical events. Other astronomers used the Egyptian solar calendar for this purpose, a practice that was still used by Copernicus in the sixteenth century.
Boyle now delivers a long winded account of the Roman Republic and Julius Caesar’s adoption of the Egyptian solar calendar and the introduction of the Julian calendar, and moans about the fact that her beloved moon was no longer the time giver.
Chapter nine of Boyle’s book, The Moon in Our Eyes, starts once again with the erroneous claim that geocentrism was somehow a philosophical fable because Aristotle ordered it so, the Church in the Middle Ages taking on this obviously false model because it fit Holy Scripture. Closing with the statement, “The geocentric model was easy to accept because it made sense. As long as you didn’t ask too many questions.” She then writes:
By the turn of the seventeenth century C.E., people did start asking those questions, or at least they began writing them down and publishing them. Men like Thomas Harriot, Johannes Kepler, and Galileo Galilei changed the way we see the cosmos.
[…]
These men promoted and then proved [my emphasis] the revolutionary heliocentric theory of Nicolaus Copernicus.
I don’t need to tell regular readers of this blog that these men did not in anyway succeed in proving the heliocentric theory.
In a great swirl of purple prose about Alexandria and the library, which I’m not going to type out here, Boyle introduces us to Claudius Ptolemy. We then get a totally false and highly misleading picture presented to her readers.
Before Ptolemy, a simple Aristotelian, Earth-centered universe was the most widely accepted cosmology. The other planets, the Moon, and the Sun [superfluous as the moon and the sun were considered planets] traced a circular path–because circles are a “perfect” shape–around Earth. The celestial bodies do not actually do this, of course, and this is obvious if you watch them. So philosophers performed mental gymnastics to satisfactorily “save the phenomenon” of the Sun’s apparent rotation around the Earth. A theory of cosmology must account for the actual cosmos after all.
Apart from a few quibbles it is basically OK up to here but it is with Ptolemy that she goes off the rails.
Claudius Ptolemy performed incredible feat of mental goaltending to achieve this save.
[…]
Ptolemy called it Mathematike syntaxis (Mathematical Arrangement)
[…]
Ptolemy’s model of the heavens placed a stationary Earth at its center, just as thinkers before him had done through the ages. But Ptolemy was the first [my emphasis] to attempt to explain how this arrangement could work, using what might generously be considered fuzzy math.
The Babylonian astronomers, it’s those pesky sky priest again, had arithmetical-algebraic algorithms that fairly accurately tracked the orbits of the planets before the Greeks began to take astronomy seriously. Unfortunately, we know next to nothing about Babylonian cosmology. The mathematician Eudoxus of Cnidus (c. 390–c. 340 BCE), so five hundred year before Ptolemy, probably a student of Plato, combined Plato’s wish for the “study of the mathematical motions of the heavenly bodies” with Aristotle’s metaphysical, cosmological precepts to create the geometrical, homocentric spheres model of the cosmos, which did a reasonable job of modelling the motion of the celestial bodies, but did have some problems. His student, Callippus (c. 370–c. 300 BCE) produced an improved version of this model as did, later, Aristotle.
The deferent-epicycle model that Ptolemy used, his fuzzy maths according to Boyle, was first proposed by Apollonius of Perga (c. 240–c. 190 BCE) at the end of the third century BCE, so three hundred and fifty years before Ptolemy. It was developed by Hipparchus (c. 190–c. 120 BCE), who used it extensively during the second century BCE, so three hundred years before Ptolemy, who references both Apollonius and Hipparchus in his usage. But Boyle tells us that that Ptolemy was the first!
Boyle goes on to give a rather confused account of the deferent-epicycle model and Ptolemy’s equant point, I’m not going to go there, before pointing out that Ptolemy’s model for the Moon, whilst correctly predicting its position, would have meant a ridiculous change in its apparent size.
Boyle points out correctly that several Islamic astronomers criticised and corrected Ptolemy’s models without naming them, with the exception of Ibn al-Haytham (c. 965–c. 1040) with his Doubts Concerning Ptolemy. Then goes on to blame Augustinus (354–430) for the fact that nobody in the West criticised Ptolemy, which is simply not true, several people did, but I can’t be bothered to go there.
We then get the standard myth of the start of the Renaissance, although she doesn’t use the term, with the fall of Constantinople in 1453, and the image of Greek Orthodox scholars fleeing before the Ottoman Turks with armfuls of precious book. An outdated and largely false story. She continues:
One of these migrants was a man named Basilios Bessarion, who studied philosophy in Constantinople. He vowed to reunite the Greek and Latin worlds, both their religions and their faith traditions and in this quest he saved huge swaths of material that may otherwise have been destroyed by the new Turkish regime.
As we shall see this is a complete fairy tale and I was curious where she had acquired it. She references Violet Moller, The Map of Knowledge: How Classical Ideas Were Lost and Found; A History of Seven Cities (Picador, 2020). I bought this book, when it came out, and when I tried to read it, was so pissed off by the factual errors in the opening pages that a gave up and never went back to it. I quit on page twenty-five! So, being a sucker for punishment, I took Moller’s book off the shelf and look at what she had written about Bessarion and interestingly she doesn’t deliver the fairy tale that Boyle dishes up but gets the story largely right.
Bessarion left Constantinople in 1437 to attend the Council of Ferrara-Florence on the reunification of the Churches. He returned to Constantinople in 1439 but found that he was unpopular due to his support of unification and in the same year returned permanently to Italy. A Renaissance Humanist, Neo-Platonist scholar he acquired his famous library by having manuscripts coped from the libraries and archives of the cloisters and monasteries of Europe. He donated his collection, of 482 Greek manuscripts and 264 Latin manuscripts to the Senate of Venice where it still forms the core of the St. Mark’s Biblioteca Marciana. Having been acquired in Europe his collection was never in danger of having “been destroyed by the new Turkish regime” This potential destruction is also a myth, as Mehmed II, the Ottoman Sultan, who conquered Constantinople was a scholar and an avid patron of the arts, literature, and the sciences. He invited artists from Renaissance Italy, Greek scholars, and Islamic astronomers to come and work on his court. He built a massive multilingual library that contained over 8000 manuscripts in Persian, Ottoman Turkish, Arabic, Latin, and Greek, among other languages.
Boyle continues the story of Bessarion:
Then in 1460, Bessarion travelled to Vienna and had a fateful encounter with a young man named Regiomontanus.
Bessarion commissioned Regiomontanus and another scholar to produce a new translation of Almagest. It would be used for teaching so they cut it in half and included a handy reader’s guide–essentially a SparkNotes version of the must important mathematical treatise to come down from antiquity.
The Epitome of the Almagest was a pleasant abridgement of Ptolemy’s master work, and like modern literary criticism, the translators had no problem pointing out errors, either in fact or omission. Chief among Regiomontanus’s critiques was the fact that Ptolemy had been wrong about the Moon. In 1491, an eighteen-year-old student at the University of Kraków picked up a copy of the Epitome and grew intrigued.
I’ve written a whole blog post telling the correct story of the Epitome, so I’ll just give a brief synopsis here. Bessarion travelled to Vienna as papal legate to negotiate with Frederick III. He met with Georg Peuerbach (1423–1461), Boyle’s “other scholar”, then the leading astronomical scholar in Europe and commissioned him to make a new translation of the Almagest. Peuerbach couldn’t read Greek but agreed to produce an epitome or digest, an updated, modernised, shortened, mathematically improved version of the Almagest. He died in 1461 having only completed the first six of thirteen book of his epitome. He did, however, extract the deathbed promise from his star pupil, Regiomontanus, to finish the work. In the same year Regiomontanus left Vienna for Italy as a member Bessarion’s entourage, where he spent the next four years learning Greek, finishing the epitome and acting as Bessarion’s manuscript collector and librarian. The Epitome of the Almagest is a masterpiece, to compare it to a SparkNotes is like comparing a Ferrari to a rusty bicycle.
The Epitome is neither a translation (an oft repeated error) nor a commentary but a detailed sometimes updated, overview of the Almagest. Swerdlow once called it “the finest textbook of Ptolemaic astronomy ever written.” (Michael H. Shank, Regiomontanus and Astronomical Controversy in the Background of Copernicus, pp. 79-109 in Rivka Feldhay and F. Jamil Ragep eds., Before Copernicus: The Cultures and Contexts of Scientific Learning in the Fifteenth Century, McGill-Queen’s University Press, 2017, p. 90)
That Copernicus picked up a copy of the Epitome as an eighteen-year-old during his first year at the University of Kraków is hogwash. In Kraków Copernicus owned a copy of Regiomontanus’ Tabulae directionum (1490) and a copy of the Alfonsine Tables (1492) and had probably known of Albert of Brudzewo’s commentary on Peuerbach’s Theoricae novae planetarium but there is no mention of the Epitome. He probably first read it when he moved to Bologna in 1496, as in that year the first printed edition was published by Johannes Hamann in Venice. Text analysis shows quite clearly that his De revolutionibus is modelled on the Epitomerather than the original Almagest, so he definitely studied it in detail at some point in his life.
Boyle now produces a load of garbage about Copernicus being inspired to his heliocentric theory by his observations of the Moon, she writes:
On March 12, 1529 [my emphasis], Copernicus witnessed the Moon block the planet Venus from view: “I saw Venus beginning to be occulted by the Moon’s dark side midway between both horns at one hour after sunset,” he wrote in On the Revolutions. He used this occultation, and others from the star catalogues of antiquity, to deduce the motions of Venus. He was beginning to realise that Ptolemy was wrong about more than just the Moon’s weirdly tilted deferent. He began to understand the truth: that the immobile Earth is not at the center of a whirling universe, but that we inhabit but one of many planets, which all revolve around the Sun.
A wonderfully dramatic presentation of “The moment of truth”! Unfortunately, it has one small flaw. Copernicus launched his heliocentric hypothesis into the world in a manuscript, now known as the Commentariolus not later that 1514!
We still don’t know why or how exactly Copernicus came up with his heliocentric theory, the only clue he gives is that he wanted to eliminate Ptolemy’s equant point, which in his opinion was not conform with Aristotle’s metaphysical homocentric precept.
Bizarrely, Boyle writes on the following page:
Copernicus’s groundbreaking theory had taken shape by 1514, but he did not publish it for almost thirty years, until he reached old age. In the meantime, he worked as a priest and a doctor, but never neglected astronomy.
We don’t know how widely the Commentariolus was distributed but there are strong indications that it was widely known, so saying he did not publish it is rubbish. Also, Copernicus never worked as a priest, in fact he was not ordained, he was a cathedral canon, that is an administrator of the Frombork Cathedral.
Boyle then delivers up the classic, he was afraid to publish because…
He may have hesitated to publish because he understood the consequences of doing so. Even with the most religious, worshipful intent–even with a dedication to the pope himself–authoring a missive calling for Earth’s displacement was revolutionary, even heretical.
I get bored with having to repeat this. There were no religious objections to Copernicus publishing his De revolutionibus, in fact he was encouraged to do so by several high ranking Church officials, also it was not heretical. He was reluctant to publish because in the Commentariolus, he had stated that in his future book on the topic, he would prove his hypothesis and he had failed to do so.
We now turn to the telescope and refreshingly we start with Thomas Harriot (c. 1560–1621) and not Galileo. This is of course because the earliest known astronomical drawing made with a telescope is Harriot’s sketch of the Moon. Boyle visits Petworth House, where Harriot’s Moon sketches are housed. Here we get told:
To celebrate the four hundredth anniversary of the first telescope use, in 2009, the Egremont estate shared the image with the British press and McCann [Egremont House archivist] was inundated with queries. She was frustrated by the attention and the sudden realisation that Harriot, not Galileo was the first to view the Moon through spyglass. The Egremont family had known the whole time. “It really annoys the Italians. They borrowed this for an exhibit about Galileo, and I bought a copy of the catalogue because it’s such fun how dismissive they are of Harriot, “she added with a grin.
That Harriot was the first to make astronomical observations with a telescope was well known in history of astronomy circles and the information was published in Henry C. King’s The History of the Telescope in 1955 and in Albert van Helden’s The Invention of the Telescope in 1977. It is also in John W. Shirley’s Thomas Harriot, a Biography from 1983 and his earlier A Sourcebook for the Study of Thomas Harriot from 1981.
Of course, Boyle goes to town boosting Harriot’s reputation:
Harriot ought to be better known, because he was one of Elizabethan England’s finest scholars. He is considered the father of modern algebra and at his time was regarded as the equal of any Renaissance thinker. He might be the greatest mathematician Oxford has ever produced.
Regular readers will know that I hate the expression father of and Harriot is not considered the father of modern algebra. I am not cognizant with all of the mathematicians, who have issued forth from Oxford’s hallowed halls but that’s a pretty awesome statement to make, as well as a pretty stupid one.
She’s definitely going for a full hand of history of science myths and clichés:
Though Sir Francis Bacon gets credit for originating the modern Western method of experiment based science…
I wonder what it will take to kill that particular piece of ahistorical bullshit off?
Of course, hot on the heels of Harriot’s Moon drawings we have Galileo’s:
Galileo knew this, too, [the impact of an image] and, trained as a painter, he did a much better job conveying what he saw. Galileo’s masterwork Sidereus nuncius (Starry Messenger) was published in March 1610. Harriot received one of the first copies, hot off the press, and read it avidly.
[…]
As a scholar of renown, in frequent contact with men like Kepler, it’s likely he received books like Starry Messenger and Kepler’s Conversations with the Starry Messenger from the authors themselves.
I genuinely don’t know whether Harriot ever received a copy of Kepler’s Conversations with the Starry Messenger but in 1610, Galileo had almost certainly no idea who Harriot was. Harriot received a copy of Starry Messenger thanks to the English Ambassador to Venice, Sir Henry Wotton (1568–1639). Wotton was a big fan of astronomy and was friends with many leading astronomers, including, for example, Kepler, He bought two copies of Sidereus Nuncius on the day it was published, it sold out on the first day, and sent them by diplomatic courier to London.
At the close of her over long section on Harriot, Boyle writes:
Harriot and Galileo, Copernicus and Kepler, all these brothers in science, must have felt the weight of their discoveries; they certainly knew they were charting a new course. They talked about it with one another in letters, offering praise in their correspondence, and clearly enjoyed the adventure of discovery.
We are of course in the Renaissance Republic of Letters, the correspondence between scholars was often vast, running into thousands of letter over a life time and fulfilling the function that would later be taken over by academic journals. But let us examine the four astronomers that Boyle presents here. Of course, none of the other three corresponded with Copernicus, who died long before any of them was born. There was an extensive correspondence between Harriot and Kepler, on a variety of topics, between 1606 and 1609, which Boyle touches on briefly. There is no known correspondence between Harriot and Galileo. Interestingly the much quoted correspondence between Kepler and Galileo is almost non-existent. Unless I’ve miscounted, Galileo wrote a grand total of three letter to Kepler in the thirty-three years that they knew each other. Kepler a few more to Galileo but he gave up because Galileo simply didn’t reply.
We now enter the world of Galileo and Kepler. Boyle writes:
A half century after he published them, Copernicus’s ideas would change everything for both Galileo and a young Johannes Kepler at university in Germany.
In 1595, Kepler dove into Copernicus’s work in much the same way that Copernicus had studied the Epitome of the Almagest. On a scholarship to learn philosophy at the University of Tübingen, Kepler read Plutarch’s De facie and Copernicus’s On the Revolutions, and proclaimed that the Copernican system was “an inexhaustible treasure of truly divine insight into the wonderful order of the world and all bodies therein.
In 1595, Kepler had already left the university and was working as a school teacher and district mathematicus in Graz, about which more later. He did indeed have a scholarship for the University of Tübingen. However, not to study philosophy but to do a general degree in a program to qualify young men as school teachers or village pastors to replace the Catholics occupying these positions when Württemberg converted to Lutheran Protestantism. It was Kepler’s desire to become a pastor but he was assigned to the position of professor of mathematics at the Protestant school in Graz in 1594.
Boyle continues:
Around the same time. About 475 miles to the south, at the University of Pisa, Galileo was employed as a mathematician. In his study of gravity and motion, he gradually came to doubt the teachings of Aristotle. His uncertainty about Aristotle led him to question everything else, and like Kepler to accept the wild heretical ideas of Copernicus.
In 1595, Galileo had already been professor for mathematics in Padua, having been kicked out of Pisa in 1592. At that time, he didn’t doubt the teachings of Aristotle on motion, projectile and fall, but totally rejected them. We don’t actually know when he adopted Copernicus’s heliocentric theory, which by the way was not heretical.
It gets worse:
In the summer of 1609, while Harriot looked through his telescope and made his sketches in England, Galileo visited Venice and, for the first time gained access to a telescope. There he observed the Moon’s surface, the cloudy luminous stripe of the Milky Way; and the large moons of Jupiter, which he called “the four planets.”
Padua was the university of the Republic of Venice, and Galileo had been living there for fourteen years in 1609. He claimed that he had created his own telescope based entirely on reading a description and then applying the laws of optics. Modern research by Mario Biagioli has shown that Galileo was almost certainly shown a telescope by his friend the Venetian polymath Paolo Sarpi (1552–1623) before he made his own one.
Though Galileo’s telescopes were modest by modern standard, thin brass instruments that magnified his vision some twentyfold, they were more powerful than Harriot’s spyglass. Now in in a museum in Florence, mounted in glass cabinets with carefully controlled humidity and temperature they are some of the most precious pieces of technology in the history of humanity.
If you are going to describe how Galileo’s telescopes are housed in the Museo Galileo in Florence, then you really should also read the description; “thin brass instruments”?
Original telescope made by Galileo consisting of a main tube with separate housings at either end for the objective and the eyepiece. The tube is formed by strips of wood joined together. It is covered with red leather (which has become brown with the passage of time) with gold tooling. (Museo Galileo Virtual Museum)
As to relative magnification, the telescope that Galileo presented to the Venetian Senate on 24 August 1609 had about ninefold magnification. The ones he later built for himself to begin astronomical observation were indeed about twentyfold magnification. Harriot’s first telescope, which was probably imported from the Netherlands was about sixfold magnification. However, he and his instrument maker Christopher Tooke went on to construct better telescopes:
On 26 July 1609 at 9p.m. he sketched the Moon which was at that time 5 days old, viewing it through a telescope with a magnification of 6. He sketched the Moon again a year later on 17 July 1610, by this time he had a telescope giving him a magnification of 10. Soon he had constructed a telescope with a magnification of 20, then by April 1611 he had a 32 magnification telescope. (MacTutor)
In the years after the publishing Starry Messenger Galileo wrote letters on the nature of sunspots and conducted experiments to understand gravity.
Assuming, “experiments to understand gravity” means Galileo’s work on the laws of fall this was all done in earlier years before he ever had a telescope.
Next up Dialogo:
In the dialogue [ …] He correctly speculates on the nature of earthshine, which people had for centuries named “the ashen glow,” the phenomenon that lets you view the dusky figure of the dark sector of the Moon. This is visible when the Moon is a crescent. It happens because sunlight reflected from the Earth’s surface is bright enough to partially light the Moon, too, like a mirror shining back at you. […] Galileo wrote that “this light is seen most clearly when the horns are thinnest.”
Galileo had already given his explanation for earthshine in his Sidereus Nuncius but he was by no means the first. The earliest known correct explanation was given by Leonardo da Vinci around 1506-1509 in his notebook, which he, however, never published. Around 1578–1583 Paolo Sarpi had written about earthshine in his Scritti filosofici e Teologici:
Because of the seas, which have a polished surface, the Earth gives more light to the Moon than does the Moon to the Earth, and that light that we see on the darkened part of the Moon’s face when she is crescent comes, perhaps, from the Earth, since it cannot be the Moon’s own.
Michael Mästlin also published the explanation in 1596, with Kepler drawing attention to Mästlin’s publication in his Astronomia pars optica in 1604
Galileo followed the ancient Greek tradition and wrote his argument as a conversation, in which his characters talk about the two systems and debate their usefulness. It’s a story telling framework that makes scientific arguments easier to digest, but it is also strategic. In dialogue form, Galileo himself doesn’t have to take sides, or discuss Copernican ideas on their merits. But it is obvious where he stood.
It is immediately obvious to anybody who reads the Dialogo that Galileo does takes sides and does so massively, which is why he ended up before the Inquisition for breaching the injunction from 1616 “not to hold or teach the Copernican opinion.”
Of course, Boyle also gets this wrong:
Galileo was charged with heresy in 1633 but avoided being burnt to death at the stake by pleading because he agreed to plead guilty and deny heliocentrism.
He was not charge with heresy and he pleaded guilty because it was patently obvious that he was guilty as charged i.e. of having held or taught the Copernican opinion. He was never in danger of being burnt at the stake, as he was only found guilty of vehement suspicion of heresy, a lesser offence.
The moons of Jupiter were another huge problem, both for the world order and the Moon. By charting the Jovian satellite’s motions, Galileo had shown that not all bodies revolve around the Earth. Io, Europa, Ganymede, and Callisto–now called the Galilean moons were proof of the Copernican principle and challenged Ptolemy, Aristotle, and the Church.
The moons of Jupiter contradict the Aristotelian precept that all the celestial bodies have a common centre of rotation–homocentricity. This precept was also breached by the Ptolemaic deferent-epicycle model of planetary orbits, as Ptolemy’s critics were keen to point out over the centuries, so this was nothing new. The Copernican principle is a twentieth century philosophical concept and was not part of the game in the seventeenth century. In fact, the moons of Jupiter were as big a problem for the heliocentric astronomers as the geocentric astronomers.
Being a book about the Moon next up we have Kepler’s proto-science-fiction story Somnium.
It was 1608, and no one had yet seen the Moon through a telescope. But it was up full, and after pondering it for some time before the clouds rolled in Johannes Kepler fell into a deep sleep and began to dream.
This is how Boyle introduces the Somnium and it is poetic hogwash. To explain why I will jump forward in her book and also backwards. I shall return to the text of the Somnium afterwards.
Johannes Kepler stood on a fulcrum between two worlds. […] He learned Ptolemaic astronomy, read ancient tablets and star catalogs, but then he preformed measurements of his own in order to draw independent conclusions. At the University of Tübingen, he became a believer in the Copernican system and even tried to argue for it publicly, but the university wouldn’t let him.
Earlier Boyle had written:
Kepler decided to focus his dissertation on the Moon, aiming to use its motions to prove Copernican ideas.
Both the “dissertation” and “tried to argue for it publicly” refer to the same thing and the actual origin of Somnium. At medieval universities, and Kepler’s Tübingen was still a medieval university, student were required to take part in public disputations in which, one student would present and defend a thesis and his opponent would attempt to disprove it. These debates were refereed and marks awarded. Whilst still a student, Kepler wanted to present a thesis in a disputation in which he viewed the cosmos from the Moon to demonstrate that the geocentric concept was merely a question of perception and a lunarcentric concept would emerge from viewing the cosmos from the Moon. This is actually the central theme of Somnium. It was not a dissertation but a thesis for a student disputation. The university did not consider it a suitable topic for a disputation. In 1608, Kepler did not write it but rather rewrote it.
The conclusions that Kepler drew leading to a heliocentric system were not based on his own measurements but on those of Tycho Brahe and came more than a decade later. His adoption of Copernicanism at university was the result of hearing the lectures on the topic by Michael Mästlin, not on any measurements he had performed.
About Mästlin, Boyle writes:
His beloved professor Michael Maestlin was ultimately forbidden from speaking openly about Copernicus.
No, he wasn’t!
Because it’s about the Moon, Boyle gives a fairly detailed description of Somnium but unfortunately repeats the myth that it led to Katherina Kepler’s trial for witchcraft. The story is complicated and I once wrote a very long blog post about it that you can read here.
Returning to the Copernican Kepler, Boyle writes:
Kepler posited in 1609, in his groundbreaking New Astronomy, that the Sun is at the center of the orbits of the planets; that the Sun moves them along their orbits, and that Scripture, that states otherwise, should be appreciated as poetic analogy but not taken as dogma: and the planets do not orbit the Sun in a circle, but in an ellipse.
A small, but very fundamental, point is that the Sun is not at the centre of a planet’s orbit but at one focus of the ellipse, as stated in Kepler’s first planetary law.
Kepler’s findings were all remarkably bold, especially for a devout, mystical man witing in the early seventeenth century. Kepler stood above the field of science arrayed before him, from Copernicus to Brahe to Galileo, and applied his own observation to draw original conclusions.
To claim that Kepler stood above is wrong. He created a symbiosis out of his ardent Copernicanism and Tycho’s decades of accurate observations, which supported, but not yet proven, by the telescopic observations of Galileo, Simon Marius, Christoph Scheiner and others laid the foundations of our modern astronomy.
Though he remained pious, Kepler’s well-known support of Copernicus and Galileo made it harder for him to get a good job when he graduated from university. Instead of procuring a faculty position in astronomy like he wanted, Kepler was sent to practice astrology in faraway Graz, Styria, which is now part of Austria.
How is it possible to get so much wrong in just fifty-three words? We will start with Galileo. When Kepler left the University of Tübingen in 1594 he had never heard of Galileo and had absolutely no idea who he was, the same was true in reverse. Kepler didn’t have to get a job when he graduated, as already explained he had a scholarship in a program to train university graduates as school teachers and village pastor for the Lutheran church to replace to Catholic ones evicted in recently converted areas. When he finished his education he just had to wait to be allocated to his new position. Far from wanting a faculty position in astronomy, there was no such thing anyway, Kepler deeply desired to become a pastor and was initially deeply disappointed when offered the position of professor for mathematics in the Protestant school in Graz instead. He could have declined but then he would have had to repay his scholarship, which he was in no position to do, so he went to Graz. Famously it was there, whilst teaching that he had the revelation that he could worship his God by revealing the geometrical structure of his cosmos. Kepler also held the position of district mathematicus, which, amongst other things, meant that he had to produce the annual almanac and prognostica. This provided the necessary astrological data for physicians to practice astro-medicine, or iatromathematic as it was known, the then mainstream medicine. This was actually profitable for Kepler as the compiler and the printer publisher usually shared the not inconsiderable profits fifty-fifty.
The prognostica about which he was more than somewhat reluctant, of which more soon, proved profitable in a different way. His prognostication for his first year proved very accurate and he earned a good reputation. This reputation saved him and gave him an exemption, the first time the authorities in the deeply Catholic region forced the Protestants to either convert of to emigrate.
He did not like it, scoffing that astrology is “sortilegious monkey-play.”
[…]
“A mind accustomed to mathematical deduction, when confronted with the faulty foundations [of astrology], resists a long, log time like an obstinate mule, until compelled by beating and curses to put its foot into that dirty puddle,” Kepler complained in one exemplary letter.
It is possible in Kepler’s voluminous writings to find many statements attacking astrology but one has to be careful before drawing the conclusion that he was anti-astrology. His position was much more complex. He totally rejected the conventional Greek horoscope astrology and this rejection is what fuelled all of his infamous negative attacks on the discipline. However, he believed deeply in celestial influence the principle on which astrology is constructed, so he developed his own system of astrology. Unlike his astronomy, this found no takers and died with him, except for the new planetary aspects that he introduced. When forced to produce conventional horoscope astrology he relied on common sense and applied psychology rather than the stars and proved to be a highly successful astrologer.
Kepler […] published The Cosmographical Mystery, another weird amalgam of mystical and evidence-based meanderings that compare Copernican and Ptolemaic cosmology. The great Tycho Brahe read it and appointed Kepler his assistant, rescuing Kepler from astrology. [my emphasis] When Brahe died in 1601, Kepler took over Brahe’s role as imperial mathematician to Holy Roman Emperor Rudolph II.
When I first read the four emphasised word I didn’t know whether to laugh or cry. But first things first. Mysterium Cosmographicum (1596) does not compare Copernican and Ptolemaic cosmology but answers the question why, in Copernicus’ heliocentric cosmos, there were exactly six planets. Brahe didn’t read it and appoint Kepler as his assistant, he read it and complained bitterly to Mästlin that Kepler had dedicated it to Nicolaus Reimers Baer (1551–1600), an astronomer, whom Brahe hated. In 1599, due to the fact that the Protestants had all been driven out of Styria, the school closed and Kepler became unemployed, he wrote to Tübingen hoping for some sort of appointment but only received the cold shoulder. In desperation he wrote to Tycho and before he even received a reply, Tycho had written him one inviting him to visit, he set off to Prague. The two men met and right at the beginning the two sensitive and explosive astronomers clashed and almost never came together. Thanks to the negotiating skills of the physician Jan Jesenius (1566–1621) the two hot heads reconciled and Kepler began to work in Prague, not as Tycho’s assistant but as his colleague, as an employer of Rudolf II.
Tycho was, naturally, a practicing astrologer and when Kepler succeeded him as Imperial Mathematicus, less than a year later his most important function in this role was as court astrologer to Rudolf, a post he held for ten years, hence my reaction. Given the volatile political situation in Prague especially concerning Rudolf’s position this was a very stressful situation for Kepler, as the court astrologer was an important political advisor. As already mentioned, with his mixture of common sense and applied psychology he managed to survive the perils of his position.
At this point, I abandon my analysis of Boyle’s book as she move on into the eighteenth century and beyond, discussing science-fiction, rocketry and other things that I do not wish to comment on.
In my opinion, the presentation of the history of astronomy in this book is so bad, as I hope I have demonstrated through my analysis, that it should never have been published as it stands.
[1] Rebecca Boyle, Our Moon: A Human History, Sceptre, 2024