Category Archives: History of Astronomy

Not an expert

BBC Radio 4 has a series called Great Lives, which is presented by former Conservative MP and now journalist, writer and broadcaster Matthew Parris. On the programme a ‘lay person’ talks about a figure, usually from history, who is their hero or role model, their comments being filled out by an ‘expert’ on the life of the figure in question. The format is in the form of a light-hearted three-way chat. Three years ago the BBC DJ Bobby Friction chose Galileo Galilei as his Great Life. At the time I listened and not surprisingly found the programme cringe worthy, dismissed it and forgot about it. However over the weekend people, who should know better, were promoting the programme on social media. Against my better judgement I listened to the whole thing again and decided to write this brief post on just one aspect, the greatest historical blunder, of the programme.

Before turning to the main topic of this post there is an aspect of the programme that needs to be addressed first. As explained above the discussion always includes an ‘expert’ to fill out with facts the account given of the subject of the programme. A programme about Galileo, so we can expect a historian of science as expert, yes? No! Instead of a historian of science what we get is Dr David Berman a reader in theoretical physic from Queen Mary College London. This is unfortunately a very common habit amongst journalists and broadcasters. They want someone to comment on, or explicate some aspect of, or episode out of the history of science, they ask a scientist and not a historian of science. Whilst I’m quite happy to acknowledge that there are some scientists who are also competent historians of science, they are unfortunately a small minority. The majority of scientists when asked to talk about the history of their subject usually deliver something highly inaccurate, factually false and toe curlingly cringe worthy. David Berman is no exception. As I wrote above, I’m not going to waste my time, and yours, doing a blow by blow analysis of this sorry mess but just address the one truly glaring clangour that our so-called expert drops towards the end of the discussion.

In an exchange beginning at about 22.20mins we hear the following:

MP: But he was friends with the Pope, why didn’t the Pope stick up for him?

DB: Oh, so he was friends with Urban VII who was the Pope, who was around the time when he started the book and the original censor but by then he died and we had Urban VIII…

He we have the classic example of a so-called expert who has literally no idea what he’s talking about and just makes something up that he thinks sounds plausible. For those that don’t know their papal history and/or the story of Galileo’s interaction with the papacy I will explain.

Paul V (1552–1621) was the Pope (1605–1621) who set up the commission of theologians in 1616 to consider the status of heliocentricity, which ruled it “foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture”. He then instructed Cardinal Bellarmine to meet with Galileo and to inform him that he was no longer allowed to teach the truth of heliocentricity.

Pope Paul V by Caravaggio. Source: Wikimedia Commons

Pope Paul V by Caravaggio.
Source: Wikimedia Commons

Both Bellarmine and Paul, however, assured Galileo that he was, at this time, in no personal danger. Paul died in 1621 and was succeeded by Gregory XV (1554–1623) who as Pope (1621–1623) played no significant role in the life of Galileo.

Pope Gregory XV Source: Wikimedia Commons

Pope Gregory XV
Source: Wikimedia Commons

Gregory was succeeded in 1623 by Cardinal Maffeo Barberini (1568–1644) who became Urban VIII.

Circa 1598 painting of Maffeo Barberini at age 30 by Caravaggio. Source: Wikimedia Commons

Circa 1598 painting of Maffeo Barberini at age 30 by Caravaggio.
Source: Wikimedia Commons

Those of you wondering where Urban VII fits into this, he doesn’t. Giovanni Battista Castagna (1521–1590) ruled as Pope Urban VII for just twelve days between 15 and 27 September 1590, when Galileo was just beginning his career as professor for mathematics in Pisa. Urban VII’s twelve-day papacy was the shortest in history.

Pope Urban VII – Pope for Twelve Days Source: Wikimedia Commons

Pope Urban VII – Pope for Twelve Days
Source: Wikimedia Commons

As an additional comment no Pope was ever the censor, as claimed by Berman, but naturally employed others to do this work for the Church.

As Matthew Parris rightly claims Cardinal Maffeo Barberini had been a friend and supporter of Galileo’s since the publication of the Sidereus nuncius in 1610 as well as being a patron of the Accademia dei Lincei, the small elite scientific society that had elected Galileo a member in 1611 on the strength of his telescopic discoveries. It was also the Lincei who gave the telescope its name. When Barberini was elected Pope in 1623 the Lincei published a broadsheet celebrating his election, which contained the first every illustrations made with a microscope.

Accademia dei Lincei Flyer celebrating the elevation of Maffeo Barberini to Pope 1623 Stelutii Melissographia

Accademia dei Lincei Flyer celebrating the elevation of Maffeo Barberini to Pope 1623
Stelutii Melissographia

The Lincei also published Galileo’s Il Saggiatore (The Assayer), which was dedicated to the new Pope in 1623.

Title page Il Saggiatore !623 Source: Wikimedia Commons

Title page Il Saggiatore !623
Source: Wikimedia Commons

Barberini much enjoyed Il Saggiatore and showed Galileo much favour. Galileo grasped the opportunity and persuaded the Pope to let him write a book describing the geocentric and heliocentric systems to prove that the Catholics did not favour the former out of ignorance of the latter, as he claimed the Protestants were alleging. Urban agreed to his request but under the condition that the two systems were presented equally without bias and without favouring either.

A portrait of Pope Urban VIII by Pietro da Cortona (1627) Source: Wikimedia Commons

A portrait of Pope Urban VIII
by Pietro da Cortona (1627)
Source: Wikimedia Commons

The book that Galileo wrote, his Dialogo, a polemic masterpiece, was of course anything but unbiased, tilting the arguments so far that any reader would be led to the conclusion that the heliocentric system was vastly superior to the geocentric one; a claim for which he had no empirical proof. He topped the whole thing off by putting the Pope’s own thoughts on the subject, a direct quote, into the mouth of a figure who was close to being a simpleton at the climax of the book.

Frontispiece and title page of the Dialogo, 1632 Source: Wikimedia Commons

Frontispiece and title page of the Dialogo, 1632
Source: Wikimedia Commons

That Urban was pissed off by the results should not have come as a surprise to Galileo and things took their inevitable course. The motto of the story is don’t play your friend for a fool when he happens to be an all powerful absolutist ruler.

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How do we kill off myths of science zombies?

The Internet is a sort of cyberspace limbo where myths in the history of science, which have been debunked a long time ago, keep popping up on social media as #histsci zombies, the history of science undead. One such that has popped up to haunt me several times in recent weeks is the claim that Johannes Kepler murdered Tycho Brahe. This claim was at best ludicrous and, having been thoroughly debunked, is now just pathetic but continues to ghost through cyberspace as a #histsci zombie. Where does it come from, who put it into the world and did it ever have any validity?

Portrait of Kepler by an unknown artist, 1610 Source: Wikimedia Commons

Portrait of Kepler by an unknown artist, 1610
Source: Wikimedia Commons

After protracted negotiations and a return to Graz to fetch his family Johannes Kepler began to work with Tycho Brahe in Prague as his assistant in late 1600, not as his student as is often falsely stated. In September 1601, Tycho managed to negotiate an official position for Kepler at the Imperial Court of the German Emperor Rudolph II. Their partnership was however short lived, as Tycho died 24 October 1601. According to Kepler’s account Tycho had retained his urine during a banquet eleven days earlier, so as not to breach etiquette by leaving the table. Upon returning home he was unable to urinate, fell ill and falling into delirium died, apparently of some sort of urinary infection. This was the state of play in 1601 and remained unchanged until 1901.

Tycho Brahe Source: Wikimedia Commons

Tycho Brahe
Source: Wikimedia Commons

In 1901 Tycho’s body was exhumed and an autopsy carried out that failed to establish a cause of death. However when the corpse was reburied a sample of his beard hair was retained. In 1990 this hair sample was analysed and found to contain abnormally high levels of mercury, which led to the speculation that Tycho had died of mercury poisoning. At this point there was no real suspicion of murder but more speculation about an accidental mercury poisoning. Tycho was a Paracelsian pharmacist, who along with his observatory on Hven ran a pharmacy that produced various medical remedies. The speculation was that he had either poisoned himself whilst working with mercury, a not uncommon problem amongst pharmacists in the Early Modern period when mercury was used extensively in medicines, or that he had poisoned himself by taking one of his own mercury containing remedies.

The first real accusations that Tycho had been murdered, that is poisoned by another person, came with the publication in 2004 of Joshua & Anne-Lee Gilder’s book Heavenly Intrigue: Johannes Kepler, Tycho Brahe, and the Murder Behind One of History’s Greatest Scientific Discoveries. Put simply the Gilders claimed that Kepler had poisoned Tycho to gain access to his astronomical data. The first part of their book, in which they outline the lives of Tycho and Kepler is actually well researched and well written but it’s when they come to the cause of Tycho’s death the book goes of the rails.

The Gilder’s build a chain of speculative, unsubstantiated, circumstantial evidence leading to their conclusions that Tycho was murdered and Johannes Kepler did the evil deed. Any able defence lawyer or competent historian of science could dismantle the Gilder’s rickety and highly dubious chain of evidence without too much effort leading to a full acquittal of the accused. Unfortunately most book reviewers are neither lawyers nor historians of science and the popular press reviewers jumped on the book and swallowed the Gilder’s arguments hook, line and sinker. The result was that Kepler went from being a hero of the scientific revolution to being a perfidious murderer, almost overnight.

Fascinatingly, the furore created by the popular press led to an international team of experts being granted permission to exhume Tycho’s corpse and to carry out yet another autopsy. The noble Dane would not be allowed to rest in peace. This was duly done in 2010 and the corpse, or what was left of it, was subjected to a battery of scientific tests. All of this activity led to the popular science press publishing a cart load of articles, many of them on the Internet, asking if Kepler had indeed poisoned Tycho most of them skewing their articles strongly in the direction of a guilty verdict.

The international team of archaeologists, forensic anthropologists, pathologists and whoever took their time but in 2012 they finally published their results. There was not enough mercury present in the samples to have caused mercury poisoning and there were no other poison found in any quantities whatsoever. Tycho was not poisoned by Johannes Kepler or anybody else for that matter. A second independent team re-analysed the beard hairs taken from the corpse in 1901 and confirmed that there was not enough mercury present to have caused mercury poisoning.

The press outlets both popular and scientific that had trumpeted the Gilder’s highly dubious claims out into the world did not apply the same enthusiasm to reporting the negative results of the autopsy. Those lengthy articles in the Internet claiming, implying, insinuating or suggesting that Kepler had done for his employer were not updated, amended or corrected to reflect the truth and the Gilder’s book was not withdrawn from the market or consigned to the wastepaper basket, where it very definitely belongs. Below is part of the sales pitch for that book taken just a couple of hours ago from Amazon.com:

But that is only half the story. Based on recent forensic evidence (analyzed here for the first time) and original research into medieval and Renaissance alchemy—all buttressed by in-depth interviews with leading historians, scientists, and medical specialists—the authors have put together shocking and compelling evidence that Tycho Brahe did not die of natural causes, as has been believed for four hundred years. He was systematically poisoned—most likely by his assistant, Johannes Kepler.

An epic tale of murder and scientific discovery, Heavenly Intrigue reveals the dark side of one of history’s most brilliant minds and tells the story of court politics, personal intrigue, and superstition that surrounded the protean invention of two great astronomers and their quest to find truth and beauty in the heavens above.

The result of all this is that historian of astronomy of the Early Modern period are forced to indulge in a game of historical Whac-A-Mole every time that somebody stumbles across one of those articles in the Internet and starts broadcasting on Twitter, Facebook or wherever that Johannes Kepler murdered Tycho Brahe.

 

 

 

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

Galileo Super Star – Galileo Galilei to get Hollywood biopic

My attention was drawn recently to a Hollywood gossip website that announced that a movie is to be made of a play by Richard Goodwin about Galileo, The Hinge of the World. I must admit that my curiosity was piqued, not least because I had never heard of either Mr Goodwin or his play and I naturally wondered what his line on the Tuscan mathematicus would be. It turns out that Richard Goodwin is a former high power Washington political advisor and speechwriter who served Presidents Kennedy and Johnson as well as JFK’s brother Robert, not exactly the best qualifications for the author of a play about the history of science. My doubts about this particular production were only heightened upon reading the full original title of the play, The Hinge of the World: In Which Professor Galileo Galilei, Chief Mathematician and Philosopher to His Serene Highness the Grand Duke of Tuscany, and His Holiness Urban VIII, Bishop of Rome, Battle for the Soul of the World. This title does not bode well for a historically accurate account of Galileo’s clash with the Catholic Church. However I will reserve judgement, because as I say, I do not know the play. I have however ordered a second hand copy that is at this very moment wending its way from some distant land to my humble abode and when it arrives and I have perused it with due diligence, I will report back with a critical assessment.

A scene from the stage production of The Hinge of the World

A scene from the stage production of The Hinge of the World

The website report does however offer a précis of the contents of the soon to be film and this is possibly the most confused and inaccurate presentation of the affair and the events leading up to it that I have read in a very long time:

The film will stay true to the spirit of the play in that it will revolve around the one-time friends whose vehement disagreements led to the Church calling Galileo out for heresy when science started to challenge long-held beliefs.

Science had been challenging long held beliefs long before Galileo came along. Apart from anything else Galileo was tried for defending the truth of Copernicus’ heliocentric hypothesis and Copernicus had died twenty-one years before Galileo was born. Just for the record Copernicus was also by no means the first person to present science that challenged the Church’s long-held beliefs.

Just to be a little bit pedantic, the one-time friends, Galileo and Maffeo Barberini (Pope Urban VIII) only had one vehement disagreement.

During that time, around 1610, the Church was never questioned,…

Somebody really ought to have consulted a historian of the Catholic Church. People both inside and outside of the Church questioned it continuous, some with impunity, for example Galileo’s friend Paolo Sarpi, and some with dire consequences, such as Giordano Bruno.

…yet Galileo who had a passion, curiosity and a telescope started to question everything after logging what he was learning through his scientific research. He published much of his findings in a book that were disavowed by Pope Urban VIII and the Catholic Church. Despite delving into dangerous territory, Galileo continued his research into comets, tide movements until he was ultimately ordered by the Church to stop teaching his ideas.

 The above is just a historical train wreck. The book of Galileo’s disavowed by Urban VII and the Church was the Dialogue Concerning the Two Chief World Systems, published in 1632, which led directly to his trail and imprisonment in 1633. However, he was told to stop teaching the truth of the heliocentric hypothesis and only that, the rest of his ideas were not the subject of Church condemnation, in 1616 following the semi-public distribution of the so-called Letter to Castelli, much later published in expanded form, as the Letter to the Grand Duchess Christina. Also in 1616 Paul V was Pope and Maffeo Barberini was a mere Cardinal and still a good friend of Galileo’s.

 The brilliant scientist, engineer, physicist and mathematician who helped discover the law of the pendulum (which became the basis for modern-day clocks), who pushed scientists to conduct experiments to prove theorems, who continued the work of Nicolaus Copernicus to help understand our own universe and laid the groundwork for modern astronomy eventually lost his battle with the powerful Roman Catholic Church.

Again being somewhat pedantic, Galileo got the law of the pendulum wrong and modern day clocks stopped being pendulum driven some time ago. Also, and this is not so pedantic, it was Kepler, and not Galileo, who laid the groundwork for modern astronomy.

 He was tried for heresy and sentenced to imprisonment at the age of 68 where he would remain until his death nine years later at age 77.

A final point, that people love to forget because it rather spoils the image of Galileo the martyr, his sentence of imprisonment imposed for vehement suspicion of heresy, not heresy, was instantly commuted to house arrest, which whilst somewhat restrictive was by no means harsh.

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All of this ties in rather nicely with an exchange that I took part in yesterday evening on twitter. Tim Skellet (@Gurdur) asked me and others, “what’s the very best, most comprehensive bio of Galileo, please?” My answer was, “I don’t think it exists. Read several: Wootton, Heilbron, Biagioli, Shea/Artigas.” I was not trying to be clever or awkward. I genuinely believe that if you wish to study any major figure out of the history of science then you should consult multiple sources, as all sources have their advantages and disadvantages. History is, to a large extent, a game of interpretation. There are facts but they only give a partial picture and it is the role or responsibility of the historian to complete that picture to the best of their ability. All historians have agendas and biases and to obtain a rounded picture it is always advisable to view the facts through the eyes of more than one historian.

Turning to the special case of Galileo, the two most recent complete biographies are J. L. Heilbron’s Galileo (OUP, 2010) and David Wootton’s Galileo: Watcher of the Skies (Yale University Press, 2010). Both are very good but differ in their interpretations and emphases. I wouldn’t recommend one over the other, so if you only want to read one then toss a coin or something. If you really want to get to grips with Galileo then read both. One important aspect of Wootton’s book is that he systematically dismantles the myth that Galileo was a good devout Catholic. This myth is trotted out regularly to make the Church look even worse for having persecuted him. Wootton demonstrates, I think convincingly, that Galileo was at best an indifferent Catholic and in no way the devout son of the Church that historical myth has made him out to be.

Although not a complete biography in the traditional sense I would also strongly recommend Mario Biagioli’s Galileo Courtier: The Practice of Science in the Culture of Absolutism (University of Chicago Press, 1993) Biagioli examines Galileo the social climber who uses his scientific discoveries to further his social status rather than for any idealistic belief in truth. Biagioli’s work is a useful complement to the more conventional scientific style of biography; what did Galileo discover and when. In what is effectively a second volume to his first book, Galileo’s Instruments of Credit: Telescopes, Images, Secrecy (University of Chicago Press, 2006), Biagioli explains how Galileo used the telescopes that he manufactured and the images that he produced to broker social advantages.

William R. Shea’s and Mariano Artigas’ Galileo in Rome: The Rise and Fall of a Troublesome Genius (OUP; 2003) just deals with the six extended visits that Galileo made to Rome, the home-base of the Church and the centre of political and social power in the period, during his lifetime. These include, his triumphal visit in 1611, as the author of his sensational Sidereus Nuncius, his visit in 1615-1616 and his failed attempt to prevent the Church condemning heliocentricity and finally his summons to his trial in 1633. By concentrating only on Galileo’s interactions with the Roman culture of the period the authors succeed in shedding light from a different angle on Galileo’s fateful path to his condemnation and fall.

At some point David Wootton joined the Twitter discussion and he recommended Pietro Redondi’s Galileo Heretic (Princeton University Press, 1992), a recommendation that I would one hundred pro cent endorse. Although Redondi’s central thesis, that Galileo was actually attacked by the Church for his atomism has, in the meantime, been largely refuted this is a superb book and still very much worth reading by anyone who wishes to learn about Galileo and the culture in which he lived and worked.

If you read all of the books that I have recommended above you should, by the time you have finished, have a fairly good all round picture of the life and work of Galileo Galilei and the footnotes and bibliographies will have given you lots of information for further reading. I will however close with a warning, do not read Michael White’s Galileo Antichrist: a Biography (Weidenfeld & Nicolson, 2007). I can deliver a comprehensive and profound review of White’s book in three words, “It is crap!”

 

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Repeat after me! – They knew it was round, damn it!

Last week saw various reports about a rare stolen copy of a Columbus letter that had turned up in the Library of Congress and has now been restored to its Italian owners; a comparatively happy end to one of a series of recent stories about the theft of precious books and documents from archives and libraries. Unfortunately the report on the website of NPR (that’s National Public Radio a non-commercial public American educational radio network) opened with the following paragraph:

The heist of a major historical document apparently went undiscovered for more than 20 years. Now, a stolen letter from Christopher Columbus spreading the news that the world isn’t flat has been returned from the U.S. to Italy.

As some readers might already have guessed the second sentence, specifically the phrase spreading the news that the world isn’t flat, had me screaming and banging my head against the wall to relieve the pain. This is just horrendously wrong in several different ways.

Posthumous portrait of Christopher Columbus by Sebastiano del Piombo, 1519. There are no known authentic portraits of Columbus. Source: Wikimedia Commons

Posthumous portrait of Christopher Columbus by Sebastiano del Piombo, 1519. There are no known authentic portraits of Columbus.
Source: Wikimedia Commons

On his first voyage Columbus set sail from Spain in September 1492 and after approximately a month of sailing westward he landed on a set of previous unknown islands, unknown to the Europeans that is. This voyage proves or disproves absolutely nothing about the shape of the earth. To even contemplate a voyage proving the earth to be spherical and not flat we would have to fast forward thirty years to the return to Spain of the one ship and eighteen men from Ferdinand Magellan’s disastrous circumnavigation in 1522; just for the record Magellan was not one of the eighteen survivors, so to call him the first man to circumnavigate the world, as many people do, is simply false. Some flat-earthers could, and probably do/did, argue that Magellan’s fleet just sailed round in a circle on a flat disc and not around a spherical earth so even that is not a totally convincing proof (even if the objection is somewhat iffy).

Let us return to the good Cristoforo. One could argue that he set sail westward to reach the Spice Islands, instead of heading to the east, as was normal because he believed the earth to be a sphere and also believed that that sphere was small enough that the route west to the Spice Islands was shorter and thus quicker than the route east (A belief, as it turns out, that was based on faulty calculation, of which more later). Having reached what he erroneously believed to be the Spice Islands, leading to the equally erroneous name, the West Indies, he believed that he had proved the world to be spherical. There is however a fundamental flaw in this argument. Columbus did not sail westward because he believed the earth to be a sphere; he did so because he, like almost every other educated European, knew that it was a sphere, knowledge that had been part of the European cultural heritage for the best part of two thousand years.

This should in the meantime be well known, but for those, like the NPR reporter(s), who have been sitting at the back and not paying attention let us pass review over those two thousand years.

We have no direct records but latter authors tell us that the Pythagoreans in the sixth century BCE already accepted that the earth was spherical. Their reasons for doing so are unknown but it was possible in analogy to the celestial sphere of the so-called fixed stars. If you look up into the heavens on a clear dark night the sky appears to take the form of an inverted bowl or hemisphere. By the latest in the fourth century BCE, Aristotle, who would go on to have a massive influence on European intellectual history, knew that the earth was spherical and he offers up a series of empirical proofs for this claim. For example he wrote, “there are stars seen in Egypt and […] Cyprus which are not seen in the northerly regions.” Since this could only happen on a curved surface, he too believed Earth was a sphere “of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent.” (De caelo, 298a2–10). He also pointed out that the shadow of the earth on the moon during a lunar eclipse is circular. Following Aristotle all Greek schools of philosophy accepted that the earth was spherical and following them the Romans. There was no doubt in the classical world that the earth was a sphere. Ptolemaeus, the most influential Greek astronomer, brought a series of arguments and proofs for the spherical form of the earth in his Syntaxis Mathematiké (Almagest) in the second century CE. Most notably that as ships approach over the horizon one sees the top of the mast before one sees the hull.

A lot of this specific knowledge got temporarily lost within Europe in the Early Middle Ages but still almost nobody who was educated doubted that the earth was a sphere. With the rise of the Islamic empire the astronomers writing in Arabic adopted the views of Aristotle and Ptolemaeus including the spherical form of the earth.

Back in the third century BCE the astronomer mathematician Eratosthenes from Alexandria determined the size of the sphere using the angle of the sun’s shadow and a bit of basic trigonometry. He achieved a fairly accurate result, its accuracy depends on which Stadia (an ancient measure of length) you think he used; we don’t know for certain. Other geographers and astronomers also determined the size of the earth’s sphere; all arriving at reasonable ball park figures. Ptolemaeus, in his Geōgraphikḕ (Geography) also determined that the known land area the oikoumenè, Europe, Africa and Asia, stretched over 180° of the earth’s surface from east to west.

In the High Middle Ages, Europe regained this knowledge, largely via the Islamic Empire through Spain and Sicily. The standard European university astronomy text Johannes de Sacrobosco’s De sphaera mundi, written in the twelfth century CE, contained all the standard Greek arguments for a spherical earth including the lunar eclipse shadow, ship breasting the horizon and the change in visible asterism travelling from south to north. There existed no doubt amongst the educated in the Middle Ages that the earth was a sphere.

Picture from a 1550 edition of De sphaera, showing the earth to be a sphere. Source: Wikimedia Commons

Picture from a 1550 edition of De sphaera, showing the earth to be a sphere.
Source: Wikimedia Commons

When Columbus started making his plans at the end of the fifteenth century he knew that the world was a sphere, as did all of the people he tried to get to back his scheme. The only disputed point was how big the earth’s sphere was, how long the central landmass, Europe, Africa and Asia, was and thus how far the Spice Islands were if one sailed west from Europe. It was here that Columbus made some fundamental calculating errors. The Arabic astronomer al-Farghānī gave 5623 Arabic miles (being 111.8 km) as the length of one degree of longitude, whereas Ptolemaeus gave 6023 Roman miles (being 89.7 km). Columbus took al-Farghānī’s figure but multiplied it with the length of a Italian mile (much shorter than the Arabic one) to determine the circumference of the earth thus arriving at a figure that was far too small: approx. 25,255 km instead of al-Farghānī’s very accurate figure of 40,248 km. Ptolemaeus’ estimate of the spread of the main landmass was 180°, whereas it is in fact only about 130°. Columbus however took the even more inaccurate estimate of Marius from Tyre of 225°. The sum of these error meant that Columbus thought he only had about 3,700 km from the Canary Islands to Japan instead of the real 19,600 km! Having convinced his sponsors of the correctness of his calculations he set sail. If America had not been in the way Columbus and his entire crew would have stared starved to death on the open ocean.

So where does the myth of the flat earth come from? There were a few European scholars in antiquity and the early Middle Ages who, against the evidence, still argued that the earth was flat. However none of them enjoyed much support. One of the ironies of history is that Copernicus probably drew attention to the most famous of them, the third century cleric Lucius Caecilius Firmianus Lactantius, by mentioning him in his De revolutionibus. The real myth of the medieval flat earth begins first in the eighteenth and nineteenth centuries and has two principal sources. Probably the most influential of these was the American author Washington Irving who in his fictional biography of Columbus claimed that Columbus had to fight against the Church’s belief that the world was flat in order to get permission and backing for his voyage, a complete fabrication. This falsehood was supported by the nineteenth centuries false interpretation of the medieval T and O Mappa Mundi.

The Hereford Mappa Mundi, about 1300, Hereford Cathedral, England. Source: Wikimedia Commons

The Hereford Mappa Mundi, about 1300, Hereford Cathedral, England.
Source: Wikimedia Commons

These medieval world maps were in the form of a circle, the O, with the three known continents, Europe, Africa and Asia, displayed in the form of a T with east at the top. These maps were interpreted in the nineteenth century as indicating that the medieval cartographers believed the earth to be a flat disc. This is not without irony as they were circular in order to indicate that the world in a sphere. The myth of the flat medieval world was taken up by two figures well known to readers of this blog John William Draper (1811–1882) and Andrew Dickson White (1832–1918) in their widespread myth of the eternal war between religion and science. Science believing in a spherical earth whereas the reactionary Church believed in a flat one.

That Europe in the Middle Ages believed in a flat earth is a total myth that just doesn’t seem to want to die. The next time somebody tells you that the medieval Church thought the world was flat, or that Columbus was a revolutionary for believing in a spherical earth or any other version of this nonsense, do me a favour, take a large, heavy, flat, round, metal object, such as a frying pan, and beat them around the head with it.

 

 

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

Isaac and the apple – the story and the myth

The tale of Isaac Newton and the apple is, along with Archimedes’ bath time Eureka-ejaculation and Galileo defiantly mumbling ‘but it moves’ whilst capitulating before the Inquisition, is one of the most widely spread and well known stories in the history of science. Visitors to his place of birth in Woolsthorpe get to see a tree from which the infamous apple is said to have fallen, inspiring the youthful Isaac to discover the law of gravity.

The Woolsthorpe Manor apple tree Source:Wikimedia Commons

The Woolsthorpe Manor apple tree
Source:Wikimedia Commons

Reputed descendants of the tree exist in various places, including Trinity College Cambridge, and apple pips from the Woolsthorpe tree was taken up to the International Space Station for an experiment by the ‘first’ British ISS crew member, Tim Peake. Peake’s overalls also feature a Principia patch displaying the apple in fall.

Tim Peake's Mission Logo

Tim Peake’s Mission Logo

All of this is well and good but it leads automatically to the question, is the tale of Isaac and the apple a real story or is it just a myth? The answer is that it is both.

Modern historians of Early Modern science tend to contemptuously dismiss the whole story as a myth. One who vehemently rejects it is Patricia Fara, who is an expert on Newtonian mythology and legend building having researched and written the excellent book, Newton: The Making of Genius[1]. In her Science: A Four Thousand Year History she has the following to say about the apple story[2]:

More than any other scientific myth, Newton’s falling apple promotes the romantic notion that great geniuses make momentous discoveries suddenly and in isolation […] According to simplistic accounts of its [Principia’s] impact, Newton founded modern physics by introducing gravity and simultaneously implementing two major transformations in methodology: unification and mathematization. By drawing a parallel between an apple and the Moon, he linked an everyday event on Earth with the motion of the planets through the heavens, thus eliminating the older, Aristotelian division between the terrestrial and celestial realms.

[…]

Although Newton was undoubtedly a brilliant man, eulogies of a lone genius fail to match events. Like all innovators, he depended on the earlier work of Kepler, Galileo, Descartes and countless others […]

[…]

The apple story was virtually unknown before Byron’s time. [Fara opens the chapter with a Byron poem hailing Newton’s discovery of gravity by watching the apple fall].

Whilst I would agree with almost everything that Fara says, here I think she is, to quote Kepler, guilty of throwing out the baby with the bath water. But before I explain why I think this let us pass review of the myth that she is, in my opinion, quite rightly rejecting.

The standard simplistic version of the apple story has Newton sitting under the Woolsthorpe Manor apple tree on a balmy summer’s day meditation on mechanics when he observes an apple falling. Usually in this version the apple actually hits him on the head and in an instantaneous flash of genius he discovers the law of gravity.

This is of course, as Fara correctly points out, a complete load of rubbish. We know from Newton’s notebooks and from the draughts of Principia that the path from his first studies of mechanics, both terrestrial and celestial, to the finished published version of his masterpiece was a very long and winding one, with many cul-de-sacs, false turnings and diversions. It involved a long and very steep learning curve and an awful lot of very long, very tedious and very difficult mathematical calculations. To modify a famous cliché the genius of Principia and the theories that it contains was one pro cent inspiration and ninety-nine pro cent perspiration.

If all of this is true why do I accuse Fara of throwing out the baby with the bath water? I do so because although the simplistic story of the apple is a complete myth there really was a story of an apple told by Newton himself and in the real versions, which differ substantially from the myth, there is a core of truth about one step along that long and winding path.

Having quoted Fara I will now turn to, perhaps Newton’s greatest biographer, Richard Westfall. In his Never at Rest, Westfall of course addresses the apple story:

What then is one to make of the story of the apple? It is too well attested to be thrown out of court. In Conduitt’s version one of four independent ones, …

Westfall tells us that the story is in fact from Newton and he told to on at least four different occasions to four different people. The one Westfall quotes is from John Conduitt, who was Newton’s successor at the Royal Mint, married his niece and house keeper Catherine Barton and together with her provided Newton with care in his last years. The other versions are from the physician and antiquarian William Stukeley, who like Newton was from Lincolnshire and became his friend in the last decade of Newton’s life, the Huguenot mathematician Abraham DeMoivre, a convinced Newtonian and Robert Greene who had the story from Martin Folkes, vice-president of the Royal Society whilst Newton was president. There is also an account from Newton’s successor as Lucasian professor, William Whiston, that may or may not be independent. The account published by Newton’s first published biographer, Henry Pemberton, is definitely dependent on the accounts of DeMoivre and Whiston. The most well known account is that of Voltaire, which he published in his Letters Concerning the English Nation, London 1733 (Lettres philosophiques sur les Anglais, Rouen, 1734), and which he says he heard from Catherine Conduitt née Barton. As you can see there are a substantial number of sources for the story although DeMoivre’s account, which is very similar to Conduitt’s doesn’t actually mention the apple, so as Westfall says to dismiss it out of hand is being somewhat cavalier, as a historian.

To be fair to Fara she does quote Stukeley’s version before the dismissal that I quoted above, so why does she still dismiss the story. She doesn’t, she dismisses the myth, which has little in common with the story as related by the witnesses listed above. Before repeating the Conduitt version as quoted by Westfall we need a bit of background.

In 1666 Isaac, still an undergraduate, had, together with all his fellow students, been sent down from Cambridge because of an outbreak of the plague. He spent the time living in his mother’s house, the manor house in Woolsthorpe, teaching himself the basics of the modern terrestrial mechanics from the works of Descartes, Huygens and the Salisbury English translation of Galileo’s Dialogo. Although he came nowhere near the edifice that was the Principia, he did make quite remarkable progress for a self-taught twenty-four year old. It was at this point in his life that the incident with the apple took place. We can now consider Conduitt’s account:

In the year 1666 he retired again from Cambridge … to his mother in Lincolnshire & whilst he was musing in a garden it came to his thought that the power of gravity (wch brought an apple from the tree to the ground) was not limited to a certain distance from the earth but that this power must extend much further than was normally thought. Why not as high as the moon said he to himself & if so that must influence her motion & and perhaps retain her in her orbit, where-upon he fell to calculating what would be the effect of this supposition but being absent from books & taking common estimate in use among Geographers & our seamen before Norwood had measured the earth, that 60 English miles were contained in one degree latitude on the surface of the Earth his computation did not agree with his theory & inclined him to entertain a notion that together with the force of gravity there might be a mixture of that force wch the moon would have if it was carried along in a vortex…[3]

As you can see the account presented here by Conduitt differs quite substantially from the myth. No tree, no apple on the head, no instantaneous discovery of the theory of gravity. What we have here is a young man who had been intensely studying the theory of forces, in particular forces acting on a body moving in a circle, applying what he had learnt to an everyday situation the falling apple and asking himself if those forces would also be applicable to the moon. What is of note here is the fact that his supposition didn’t work out. Based on the data he was using, which was inaccurate, his calculations showed that the forces acting on the apple and those acting on the moon where not the same! An interesting thought but it didn’t work out. Oh well, back to the drawing board. Also of note here is the reference to a vortex, revealing Newton to be a convinced Cartesian. By the time he finally wrote the Principia twenty years later he had turned against Descartes and in fact Book II of Principia is devoted to demolishing Descartes’ vortex theory.

In 1666 Newton dropped his study of mechanics for the meantime and moved onto optics, where his endeavours would prove more fruitful, leading to his discoveries on the nature of light and eventually to his first publication in 1672, as well as the construction of his reflecting telescope.

The Newtonian Reflector Source: Wikimedia Commons

The Newtonian Reflector
Source: Wikimedia Commons

Over the next two decades Newton developed and extended his knowledge of mechanics, whilst also developing his mathematical skills so that when Halley came calling in 1684 to ask what form a planetary orbit would take under an inverse squared law of gravity, Newton was now in a position to give the correct answer. At Halley’s instigation Newton now turned that knowledge into a book, his Principia, which only took him the best part of three years to write! As can be seen even with this briefest of outlines there was definitely nothing instantaneous or miraculous about the creation of Newton’ masterpiece.

So have we said all that needs to be said about Newton and his apple, both the story and the myth? Well no. There still remains another objection that has been raised by historians, who would definitely like to chuck the baby out with the bath water. Although there are, as noted above, multiple sources for the apple-story all of them date from the last decade of Newton’s life, fifty years after the event. There is a strong suspicion that Newton, who was know to be intensely jealous of his priorities in all of his inventions and discoveries, made up the apple story to establish beyond all doubt that he and he alone deserved the credit for the discovery of universal gravitation. This suspicion cannot be simply dismissed as Newton has form in such falsification of his own history. As I have blogged on an earlier occasion, he definitely lied about having created Principia using the, from himself newly invented, calculus translating it back into conventional Euclidian geometry for publication. We will probably never know the final truth about the apple-story but I for one find it totally plausible and am prepared to give Isaac the benefit of the doubt and to say he really did take a step along the road to his theory of universal gravitation one summer afternoon in Woolsthorpe in the Year of Our Lord 1666.

[1] Patricia Fara, Newton: The Making of Genius, Columbia University Press, 2002

[2] Patricia Fara, Science: A Four Thousand Year History, ppb. OUP, 2010, pp. 164-165

[3] Richard S. Westfall, Never at Rest: A Biography of Isaac Newton, ppb. CUP, 1980 p. 154

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

Tracking the Messenger of the Gods

On 9 May the astronomers of Europe, and other regions, having screwed their sun filters onto their telescopes, will settle down to observe a transit of Mercury. For any not familiar with astronomical jargon that is when the planet Mercury crosses the face of the sun.

Astronomy Picture of the Day: A Mercury Transit Sequence: Image Credit & Copyright Dominique Dierick

Astronomy Picture of the Day: A Mercury Transit Sequence: Image Credit & Copyright Dominique Dierick

Neither as rare nor as spectacular as the similar transits of Venus, it will still be regarded as a major event in the astronomical calendar. Transits of Venus occur in pairs separated by eight years approximately once every one hundred and twenty years. The last pair was in 2004 and 2012. The cycle of occurrences of transits of Mercury is much more complex but there will be a total of fourteen in the twenty-first century with next Monday’s being the third. Because Mercury is much smaller than Venus and much further from the Earth, unlike a transit of Venus which can be observed with the naked-eye (taking the necessary precautions against the sunlight of course), a transit of Mercury can only be observed with a telescope. The French astronomer, Pierre Gassendi, was the first person to observe a transit of Mercury in 1631 but this historic event was preceded by a couple of thousand years of speculation about the orbital path of the Messenger of the Gods.

Pierre Gassendi after Louis-Édouard Rioult. Source: Wikimedia Common

Pierre Gassendi
after Louis-Édouard Rioult.
Source: Wikimedia Common

Both Mercury and Venus when viewed from the Earth never appear to move very far away from the sun leading some astronomers in antiquity to suggest the so-called Heracleidian of Egyptian system in which the two planets orbited the sun whilst the sun orbited the earth in a geocentric system. Thanks to the De nuptiis of Martianus Cappella (fl. 410-420 CE) this partial helio-geocentric model was well known and moderately popular in the Middle Ages, so the idea that Mercury and Venus orbit the sun was not new when Tycho Brahe suggested it in his full helio-geocentric system, in which all the planets, except the moon, orbit the sun which in turn orbits the earth.

Naboth's representation of Martianus Capella's geo-heliocentric astronomical model (1573) Source: Wikimedia Commons

Naboth’s representation of Martianus Capella’s geo-heliocentric astronomical model (1573)
Source: Wikimedia Commons

In 1608 Hans Lipperhey invented the telescope and within a very short time various astronomers began to use it to observe the heavens. In November 1610 Benedetto Castelli (1578–1643) wrote to Galileo reminding him that Copernicus had predicted that Venus would have phases like the moon in a heliocentric system[1].

Benedetto Castelli

Benedetto Castelli Source: Wikimedia Commons

On 11 December Galileo wrote to Kepler informing him that he had discovered those phases, famously putting the information into an anagram, which Kepler failed to decode properly. Galileo was not alone in making these observations, Thomas Harriot in England, Simon Marius in Germany and Giovanni Paolo Lembo in Rome all independently discovered the phases proving that Venus did indeed orbit the sun and by analogy Mercury probably did as well. The telescopes in the early seventeenth century were not powerful enough to resolve the phases of Mercury.

That Venus and Mercury had been shown to orbit the sun was not a proof of heliocentricity, as this was also the case in the Heracleidian as well as various Tychonic and semi-Tychonic systems but it did mean that theoretically it should be possible to observe a transit of one or the other of them. Due to the fact that the orbits of the earth, Venus and Mercury do not all lie in the same plane but are all slightly tilted with respect to each other a visible transit does not occur by every orbit but as mentioned above at semi regular irregular intervals and in order to observe such a transit someone first had to calculate when they would take place. This task was carried out by Johannes Kepler in his Rudolphine Tables based on Tycho Brahe’s observations and published in 1627.

Frontispiece Rudolphine Table 1627 Source: Wikimedia Commons

Frontispiece Rudolphine Table 1627
Source: Wikimedia Commons

Using the information supplied by Kepler’s tables Gassendi tried to observe a transit of Venus in 1631 unaware that it would take place at nighttime for an observer in Europe. Kepler’s table lacked this level of accuracy. However earlier in the same year, on 7 November, Gassendi had become the first person to observe a transit of Mercury. The first observation of a transit of Venus was made by Jeremiah Horrocks in 1639. Gassendi was very initially cautious in going public with his discovery because his measurements of the size of the planet showed it to be much smaller than previous estimates. However three further transit observations in the seventeenth century, Jeremy Shakerly 1651, Christiaan Huygens 1661 and Edmund Halley 1677, confirmed Gassendi’s first observations and measurements.

Observation of transits of Mercury have long since become routine but that won’t stop the amateur and professional astronomers on next Monday putting up their telescopes to follow the tracks of the Messenger of the Gods as he plods his way across the sun.

[1] For a fuller description of the discovery of the phases of Venus and its significance for the history of heliocentricity see my post The Phases of Venus and Heliocentricity: A Rough Guide.

 

 

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Filed under History of Astronomy, Renaissance Science

The Astrolabe – an object of desire

Without doubt the astrolabes is one of the most fascinating of all historical astronomical instruments.

Astrolabe Renners Arsenius 1569 Source: Wikimedia Commons

Astrolabe Renners Arsenius 1569
Source: Wikimedia Commons

To begin with it is not simply one object, it is many objects in one:

 

  • An astronomical measuring device
  • A timepiece
  • An analogue computer
  • A two dimensional representation of the three dimensional celestial sphere
  • A work of art and a status symbol

 

This Medieval-Renaissance Swiss Army penknife of an astronomical instrument had according to one medieval Islamic commentator, al-Sufi writing in the tenth century, more than one thousand different functions. Even Chaucer in what is considered to be the first English language description of the astrolabe and its function, a pamphlet written for a child, describes at least forty different functions.

The astrolabe was according to legend invented by Hipparchus of Nicaea, the second century BCE Greek astronomer but there is no direct evidence that he did so. The oldest surviving description of the planisphere, that two-dimensional representation of the three-dimensional celestial sphere, comes from Ptolemaeus in the second century CE.

Modern Planisphere Star Chart c. 1900 Source: Wikimedia Commons

Modern Planisphere Star Chart c. 1900
Source: Wikimedia Commons

Theon of Alexandria wrote a thesis on the astrolabe, in the fourth century CE, which did not survive and there are dubious second-hand reports that Hypatia, his daughter invented the instrument. The oldest surviving account of the astrolabe was written in the sixth century CE by John Philoponus. However it was first the Islamic astronomers who created the instrument, as it is known today, it is said for religious purposes, to determine the direction of Mecca and the time of prayer. The earliest surviving dated instrument is dated 315 AH, which is 927/28 CE.

The Earliest  Dated Astrolabe Source: See Link

The Earliest Dated Astrolabe
Source: See Link

It is from the Islamic Empire that knowledge of the instrument found its way into medieval Europe. Chaucer’s account of it is based on that of the eight-century CE Persian Jewish astrologer, Masha’allah ibn Atharī, one of whom claim to fame is writing the horoscope to determine the most auspicious date to found the city of Baghdad.

So-called Chaucer Astrolabe dated 1326, similar to the one Chaucer describes, British Museum Source: Wikimedia Commons

So-called Chaucer Astrolabe dated 1326, similar to the one Chaucer describes, British Museum
Source: Wikimedia Commons

However this brief post is not about the astrolabe as a scientific instrument in itself but rather the last point in my brief list above the astrolabe as a work of art and a status symbol. One of the reasons for people’s interest in astrolabes is the fact that they are simply beautiful to look at. This is not a cold, functional scientific instrument but an object to admire, to cherish and desire. A not uncommon reaction of people being introduced to astrolabes for the first time is, oh that is beautiful; I would love to own one of those. And so you can there are people who make replica astrolabes but buying one will set you back a very pretty penny.

That astrolabes are expensive is not, however, a modern phenomenon. Hand crafted brass, aesthetically beautiful, precision instruments, they were always very expensive and the principal market would always have been the rich, often the patrons of the instrument makers. The costs of astrolabes were probably even beyond the means of most of the astronomers who would have used them professionally and it is significant that most of the well know astrolabe makers were themselves significant practicing astronomers; according to the principle, if you need it and can’t afford it then make it yourself. Other astronomers would probably have relied on their employers/patrons to supply the readies. With these thoughts in mind it is worth considering the claim made by David King, one of the world’s greatest experts on the astrolabe, that the vast majority of the surviving astrolabes, made between the tenth nineteenth centuries – about nine hundred – were almost certainly never actually used as scientific instruments but were merely owned as status symbols. This claim is based on, amongst other things, the fact that they display none of the signs of the wear and tear, which one would expect from regular usage.

Does this mean that the procession of astrolabes was restricted to a rich elite and their employees? Yes and no. When European sailors began to slowly extend their journeys away from coastal waters into the deep sea, in the High Middle Ages they also began to determine latitude as an element of their navigation. For this purpose they needed an instrument like the astrolabe to measure the elevation of the sun or of chosen stars. The astrolabe was too complex and too expensive for this task and so the so-called mariners astrolabe was developed, a stripped down, simplified, cheaper and more robust version of the astrolabe. When and where the first mariner’s astrolabe was used in not known but probably not earlier than the thirteenth century CE. Although certainly not cheap, the mariner’s astrolabe was without doubt to be had for considerably less money than its nobler cousin.

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Mariner’s Astrolabe Francisco de Goes 1608 Source: Istituto e Museo di Storia della Scienza, Firenze

Another development came with the advent of printing in the fifteenth century, the paper astrolabe. At first glance this statement might seem absurd, how could one possibly make a high precision scientific measuring instrument out of something, as flexible, unstable and weak as paper? The various parts of the astrolabe, the planisphere, the scales, the rete star-map, etc. are printed onto sheets of paper. These are then sold to the customer who cuts them out and pastes them onto wooden forms out of which he then constructs his astrolabe, a cheap but serviceable instrument. One well-known instrument maker who made and sold printed-paper astrolabes and other paper instruments was the Nürnberger mathematician and astronomer Georg Hartmann. The survival rate of such cheap instruments is naturally very low but we do actually have one of Hartmann’s wood and paper astrolabes.

Hartmann Paper Astrolabe Source: Oxford Museum of History of Science

Hartmann Paper Astrolabe
Source: Oxford Museum of History of Science

In this context it is interesting to note that, as far as can be determined, Hartmann was the first instrument maker to develop the serial production of astrolabes. Before Hartmann each astrolabe was an unicum, i.e. a one off instrument. Hartmann standardised the parts of his brass astrolabes and produced them, or had them produced, in batches, assembling the finished product out of these standardised parts. To what extent this might have reduced the cost of the finished article is not known but Hartmann was obviously a very successful astrolabe maker as nine of those nine hundred surviving astrolabes are from his workshop, probably more than from any other single manufacturer.

Hartmann Serial Production Astrolabe Source: Museum Boerhaave

Hartmann Serial Production Astrolabe
Source: Museum Boerhaave

 

If this post has awoken your own desire to admire the beauty of the astrolabe then the biggest online collection of Medieval and Renaissance scientific instruments in general and astrolabes in particular is the Epact website, a collaboration between the Museum of the History of Science in Oxford, the British Museum, the Museum of the History of Science in Florence and the Museum Boerhaave in Leiden.

This blog post was partially inspired by science writer Philip Ball with whom I had a brief exchange on Twitter a few days ago, which he initiated, on our mutual desire to possess a brass astrolabe.

 

 

 

 

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