Category Archives: History of Physics

Christmas Trilogy 2016 Part 1: Is Newtonian physics Newton’s physics?

Nature and nature’s laws lay hid in night;

God said “Let Newton be” and all was light.

Isaac Newton's Tomb in Westminster Abbey Photo: Klaus-Dieter Keller Source: Wikimedia Commons

Isaac Newton’s Tomb in Westminster Abbey
Photo: Klaus-Dieter Keller
Source: Wikimedia Commons

Alexander Pope’s epitaph sets the capstone on the myth of Newton’s achievements that had been under construction since the publication of the Principia in 1687. Newton had single-handedly delivered up the core of modern science – mechanics, astronomy/cosmology, optics with a side order of mathematics – all packed up and ready to go, just pay at the cash desk on your way out. We, of course, know (you do know don’t you?) that Pope’s claim is more than somewhat hyperbolic and that Newton’s achievements have, over the centuries since his death, been greatly exaggerated. But what about the mechanics? Surely that is something that Newton delivered up as a finished package in the Principia? We all learnt Newtonian physics at school, didn’t we, and that – the three laws of motion, the definition of force and the rest – is all straight out of the Principia, isn’t it? Newtonian physics is Newton’s physics, isn’t it? There is a rule in journalism/blogging that if the title of an article/post is in the form of a question then the answer is no. So Newtonian physics is not Newton’s physics, or is it? The answer is actually a qualified yes, Newtonian physics is Newton’s physics, but it’s very qualified.

Newton's own copy of his Principia, with hand-written corrections for the second edition Source: Wikimedia Commons

Newton’s own copy of his Principia, with hand-written corrections for the second edition
Source: Wikimedia Commons

The differences begin with the mathematics and this is important, after all Newton’s masterwork is The Mathematical Principles of Natural Philosophy with the emphasis very much on the mathematical. Newton wanted to differentiate his work, which he considered to be rigorously mathematical, from other versions of natural philosophy, in particular that of Descartes, which he saw as more speculatively philosophical. In this sense the Principia is a real change from much that went before and was rejected by some of a more philosophical and literary bent for exactly that reason. However Newton’s mathematics would prove a problem for any modern student learning Newtonian mechanics.

Our student would use calculus in his study of the mechanics writing his work either in Leibniz’s dx/dy notation or the more modern F’(x) = f(x) notation of the French mathematician, Lagrange (1736–1813). He won’t be using the dot notation developed by Newton and against which Babbage, Peacock, Herschel and the Analytical Society campaigned so hard at the beginning of the nineteenth century. In fact if our student turns to the Principia, he won’t find Newton’s dot notation calculus there either, as I explained in an earlier post Newton didn’t use calculus when writing the Principia, but did all of his mathematics with Euclidian geometry. This makes the Principia difficult to read for the modern reader and at times impenetrable. It should also be noted that although both Leibniz and Newton, independently of each other, codified a system of calculus – they didn’t invent it – at the end of the seventeenth century, they didn’t produce a completed system. A lot of the calculus that our student will be using was developed in the eighteenth century by such mathematicians as Pierre Varignon (1654–1722) in France and various Bernoullis as well as Leonard Euler (1707­1783) in Switzerland. The concept of limits that are so important to our modern student’s calculus proofs was first introduced by Bernard Bolzano (1781–1848), Augustin-Louis Cauchy (1789–1857) and above all Karl Theodor Wilhelm Weierstrass (1815–1897) in the nineteenth century.

Turning from the mathematics to the physics itself, although the core of what we now know as Newtonian mechanics can be found in the Principia, what we actually use/ teach today is actually an eighteenth-century synthesis of Newton’s work with elements taken from the works of Descartes and Leibniz; something our Isaac would definitely not have been very happy about, as he nursed a strong aversion to both of them.

A notable example of this synthesis concerns the relationship between mass, velocity and energy and was brought about one of the very few women to be involved in these developments in the eighteenth century, Gabrielle-Émilie Le Tonnelier de Breteuil, Marquise du Châtelet, the French aristocrat, lover of Voltaire and translator of the first French edition of the Principia.

In the frontispiece to Voltaire's book on Newton's philosophy, du Châtelet appears as Voltaire's muse, reflecting Newton's heavenly insights down to Voltaire. Source: Wikimedia Commons

In the frontispiece to Voltaire’s book on Newton’s philosophy, du Châtelet appears as Voltaire’s muse, reflecting Newton’s heavenly insights down to Voltaire.
Source: Wikimedia Commons

One should remember that mechanics doesn’t begin with Newton; Simon Stevin, Galileo Galilei, Giovanni Alfonso Borelli, René Descartes, Christiaan Huygens and others all produced works on mechanics before Newton and a lot of their work flowed into the Principia. One of the problems of mechanics discussed in the seventeenth century was the physics of elastic and inelastic collisions, sounds horribly technical but it’s the physics of billiard and snooker for example, which Descartes famously got wrong. Part of the problem is the value of the energy[1] imparted upon impact by an object of mass m travelling at a velocity v upon impact.

Newton believed that the solution was simply mass times velocity, mv and belief is the right term his explanation being surprisingly non-mathematical and rather religious. Leibniz, however, thought that the solution was mass times velocity squared, again with very little scientific justification. The support for the two theories was divided largely along nationalist line, the Germans siding with Leibniz and the British with Newton and it was the French Newtonian Émilie du Châtelet who settled the dispute in favour of Leibniz. Drawing on experimental results produced by the Dutch Newtonian, Willem Jacob ‘s Gravesande (1688–1742), she was able to demonstrate the impact energy is indeed mv2.

Willem Jacob 's Gravesande (1688-1745) Portrait by Hendrik van Limborch (1681-1759) Source: Wikimedia Commons

Willem Jacob ‘s Gravesande (1688-1745) Portrait by Hendrik van Limborch (1681-1759)
Source: Wikimedia Commons

The purpose of this brief excurse into eighteenth-century physics is intended to show that contrary to Pope’s epitaph not even the great Isaac Newton can illuminate a whole branch of science in one sweep. He added a strong beam of light to many beacons already ignited by others throughout the seventeenth century but even he left many corners in the shadows for other researchers to find and illuminate in their turn.





[1] The use of the term energy here is of course anachronistic


Filed under History of Physics, History of science, Myths of Science, Newton, Uncategorized

Werner von Siemens and Erlangen

I (almost)[1] live in the town of Erlangen in Franconia, in Southern Germany. Erlangen is a university town with an official population of about 110 000. I say official because Erlangen has a fairly large number of inhabitants, mostly student, who are registered as living elsewhere with Erlangen as their second place of residence, who are not included in the official population numbers. I suspect that the population actually lies somewhere between 120 and 130 000. Erlangen is dominated by the university, which currently has 40 000 students, although several departments are in the neighbouring towns of Furth and Nürnberg, and is thus the second largest university in Bavaria, and the company Siemens. Siemens, one of Germany’s largest industrial firms, is a worldwide concern and Erlangen is after Berlin and Munich the third largest Siemens centre in Germany, home to large parts of the company’s research and development. It is the home of Siemens’ medical technology branch, Siemens being a world leader in this field. 13 December is the two hundredth anniversary of the birth of Werner von Siemens the founder of the company.

Werner von Siemens (Portrait by Giacomo Brogi) Source: Wikimedia Commons

Werner von Siemens (Portrait by Giacomo Brogi)
Source: Wikimedia Commons

Werner Siemens (the von came later in his life) was born in Lenthe near Hanover the fourth child of fourteenth children of the farmer Christian Ferdinand Siemens and his wife Eleonore Henriette Deichmann on13 December 1894. The family was not wealthy and Werner was forced to end his education early. In 1835 he joined the artillery corps of Prussian Army in order to get an education in science and engineering; he graduated as a lieutenant in 1838.

Werner Siemens as Second-Lieutenant in the Prussian Artillery, 1842 Source: Wikimedia Commons

Werner Siemens as Second-Lieutenant in the Prussian Artillery, 1842
Source: Wikimedia Commons

He was sentenced to five years in military prison for acting as a second in a duel but was pardoned in 1842 and took up his military service. Whilst still in the army he developed an improved version of Wheatstone’s and Cooke’s electrical telegraph in 1846 and persuaded the Prussian Army to give his system field trials in 1847. Having proved the effectiveness of his system Siemens patented it and in the same year founded together with the fine mechanic Johann Georg Halske the Telegraphen-Bauanstalt von Siemens & Halske. They received a commission to construct Prussia’s first electrical telegraph line from Berlin to Frankfurt, which was completed in 1849, when Werner left the army to become an electrical engineer and entrepreneur. The profession of electrical engineer didn’t exist yet and Werner Siemens is regarded as one of its founders.

Pointer telegraph, 1847 (replica) Source: Siemens

Pointer telegraph, 1847 (replica)
Source: Siemens

Already a successful electrical telegraph construction company the next major step came when Werner discovered the principle of dynamo self-excitation in 1867, which enabled the construction of the worlds first practical electric generators. Werner was not alone in making this discovery. The Hungarian Anyos Jedlik discovered it already in 1856 but didn’t patent it and his discovery remained unknown and unexploited. The Englishman Samuel Alfred Avery patented a self-exciting dynamo in 1866, one year ahead of both Siemens and Charles Wheatstone who also independently made the same discovery.

Structure (with cross section) of the dynamo machine 1866 Source: Siemens

Structure (with cross section) of the dynamo machine 1866
Source: Siemens

Throughout his life Werner Siemens combined the best attributes of a scientists, an engineer, an inventor and an entrepreneur constantly pushing the range of his companies products. He developed the use of gutta-percha as material for cable insolation, Siemens laying the first German transatlantic telegraph cable with their own specially constructed cable laying ship The Faraday in 1874. The world’s first electric railway followed in 1879, the world’s first electric tram in 1881 and the world’s first trolleybus in 1882.

The Faraday, cable laying ship of Siemens Brothers & Co. 1874 Source: Wikimedia Commons

The Faraday, cable laying ship of Siemens Brothers & Co. 1874
Source: Wikimedia Commons

Werner Siemens was a great believer in scientific research and donated 500,000 Marks (a fortune), in land and cash, in 1884 towards the establishment of the Physikalisch-Technische Reichsanstalt a state scientific research institute, which finally came into being in 1887 and lives on today under the name Physikalisch-Technische Bundesanstalt (PTB). From the very beginning Werner Siemens thought in international terms sending his brother Wilhelm off to London in 1852 to represent the company and another brother Carl to St Petersburg in 1853, where Siemens built Russia’s first telegraph network. In 1867 Halske left the company and Carl and Wilhelm became partners making Siemens a family company. In 1888, four years before his death, Werner was ennobled becoming Werner von Siemens.

The research and development department of Siemens moved to Erlangen after the Second World War, as their home in Berlin became an island surrounded by the Russian occupation zone. Erlangen was probably chosen because it was already the home of Siemens’ medical technology section. In order to understand how this came to be in Erlangen we need to go back to the nineteenth century and the live story of Erwin Moritz Reiniger.

Siemens-Administration in the 1950s „Himbeerpalast“ Designed by  Hans Hertlein  Note the Zodiac clock dial Source: Wikimedia Commons

Siemens-Administration in the 1950s „Himbeerpalast“ Designed by Hans Hertlein
Note the Zodiac clock dial
Source: Wikimedia Commons

Reiniger born 5 April 154 in Stuttgart was employed as an experiment demonstrator at the University of Erlangen in 1876. He was also responsible for the repair of technical equipment in the university institutes and clinics. Realising that this work could become highly profitable, Reiniger set up as a self-employed fine mechanic in Schlossplatz 3 next door to the university administration in the Schloss (palace) in 1877, producing fine mechanical, physical, optical and simple electro-medical instruments.

Schloss Erlangen (university Administration) Source: Wikimedia Commons

Schloss Erlangen
(University Administration)
Source: Wikimedia Commons

Schlossplatz 3. Site of Reindeer's original workshop Source: Wikimedia Commons

Schlossplatz 3. Site of Reiniger’s original workshop
Source: Wikimedia Commons

Plaque on Schlossplatz 3

Plaque on Schlossplatz 3

By 1885 Reiniger was employing fifteen workers. In 1886 he went into partnership with the mechanics Max Gebbert and Karl Friedrich Schall forming the Vereinigte physikalisch-mechanische Werkstätten von Reiniger, Gebbert & Schall– Erlangen, New York, Stuttgart (RGS). The workshops in New York and Stuttgart were soon abandoned and the company concentrated on Erlangen. Karl Schall left the company in 1888 and Reiniger was bought out by Gebbert in 1895.

Reiniger Gebiert & Schall Letterhead 1896 Source: Wikimedia Commons

Reiniger Gebiert & Schall Letterhead 1896
Source: Wikimedia Commons

Wilhelm Conrad Röntgen discovered X-rays on 8 November 1895 and published his discovery in three scientific papers between then and January 1896.

Wilhelm Conrad Röntgen Source: Wikimedia Commons

Wilhelm Conrad Röntgen
Source: Wikimedia Commons

Famously he didn’t patent his discovery and RGS were already, as the very first company in the world, producing X-ray tubes and X-ray machines in 1896 and this would become the mainstay of their business. There is a rather sweet letter in the Siemens archive from Röntgen, who was professor in Würzburg, not too far away from Erlangen, asking if he could possibly get a rebate if he purchased his X-ray tubes from RGS.

Reiniger, Gebbert & Schall AG Factory in Erlangen constructed in 1883. Now a protected building. Source: Wikimedia Commons

Reiniger, Gebbert & Schall AG Factory in Erlangen constructed in 1883. Now a protected building.
Source: Wikimedia Commons

Following the First World War, RGS got into financially difficulties due to bad management and in 1925 the company was bought by Siemens & Halske, who transferred their own medical technology production to Erlangen thus establishing the medical technology division of Siemens in Erlangen where it still is today. Originally called the Siemens-Reiniger-Werke AG it has gone through more name changes than I care to remember currently being called ‘Healthineers’ to the amusement of the local population, who on the whole find the name ridiculous.

Siemens Medical Museum in the Reiniger, Gebbert & Schall AG Factory Building

Siemens Medical Museum in the Reiniger, Gebbert & Schall AG Factory Building

What of the future? Last week saw the laying of the foundation stone of the new Siemens Campus in Erlangen a 500 million Euro building project to provide Siemens with a new R&D centre for the twenty-first century.

Siemens Campus Architects Model

Siemens Campus Architects Model



[1] I actually live in a small village on the outskirts of Erlangen but the town boundary is about 150 metres, as the crow flies, from where I am sitting typing this post.


Filed under History of Physics, History of science, History of Technology

If you are going to blazon out history of science ‘facts’ at least get them right

Today’s Torygraph has a short video entitled 10 Remarkable Facts about rainbows, at 57 seconds it displays the following text:

Until the 17th Century, no one had

the faintest idea what a rainbow

was, how it got there or what it was

made of…

This is, of course, simply not true. In the 14th century the Persian scholar Kamal al-Din Hasan ibn Ali ibn Hasan al-Farisi (1267–1319) gave the correct scientific explanation of the rainbow in his Tanqih al-Manazir (The Revision of the Optics). Almost contemporaneously the German scholar Theodoric of Freiberg (c. 1250–c. 1310) gave the same correct explanation in his De iride et radialibus impressionibus (On the Rainbow and the impressions created by irradiance). The two scholars arrived at their conclusion independently of each other but both of them did experiments involving the study of light rays passing through glass spheres full of water and both scholars were influenced by the optical theories of Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham. Unfortunately both explanations disappeared and it was in fact first in the 17th Century that the Croatian scholar Marco de Antonio Dominis (1560–1624) once again gave an almost correct explanation of the rainbow in his Tractatus de radiis visus et lucis in vitris, perspectivis et iride.

De Dominis' explanation of the rainbow Source: Wikimedia Commons

De Dominis’ explanation of the rainbow
Source: Wikimedia Commons


Filed under History of Optics, History of Physics, History of science, 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


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


DO IT! is the title of a book written by 1960s Yippie activist Jerry Rubin. In the 1970s when I worked in experimental theatre groups if somebody suggested doing something in a different way then the response was almost always, “Don’t talk about it, do it!” I get increasingly pissed off by people on Twitter or Facebook moaning and complaining about fairly trivial inaccuracies on Wikipedia. My inner response when I read such comments is, “Don’t talk about it, change it!” Recently Maria Popova of brainpickings posted the following on her tumblr, Explore:

The Wikipedia bio-panels for Marie Curie and Albert Einstein reveal the subtle ways in which our culture still perpetuates gender hierarchies in science. In addition to the considerably lengthier and more detailed panel for Einstein, note that Curie’s children are listed above her accolades, whereas the opposite order appears in the Einstein entry – all the more lamentable given that Curie is the recipient of two Nobel Prizes and Einstein of one.

How ironic given Einstein’s wonderful letter of assurance to a little girl who wanted to be a scientist but feared that her gender would hold her back. 

When I read this, announced in a tweet, my response was a slightly ruder version of “Don’t talk about it, change it!” Within minutes Kele Cable (@KeleCable) had, in response to my tweet, edited the Marie Curie bio-panel so that Curie’s children were now listed in the same place as Einstein’s. A couple of days I decided to take a closer look at the two bio-panels and assess Popova’s accusations.

Marie Curie c. 1920 Source Wikimedia Commons

Marie Curie c. 1920
Source Wikimedia Commons

The first difference that I discovered was that the title of Curie’s doctoral thesis was not listed as opposed to Einstein’s, which was. Five minutes on Google and two on Wikipedia and I had corrected this omission. Now I went into a detailed examination, as to why Einstein’s bio-panel was substantially longer than Curie’s. Was it implicit sexism as Popova was implying? The simple answer is no! Both bio-panels contain the same information but in various areas of their life that information was more extensive in Einstein’s life than in Curie’s. I will elucidate.

Albert Einstein during a lecture in Vienna in 1921 Source: Wikimedia Commons

Albert Einstein during a lecture in Vienna in 1921
Source: Wikimedia Commons

Under ‘Residences’ we have two for Curie and seven for Einstein. Albert moved around a bit more than Marie. Marie only had two ‘Citizenships’, Polish and French whereas Albert notched up six. Under ‘Fields’ both have two entries. Turning to ‘Institutions’ Marie managed five whereas Albert managed a grand total of twelve. Both had two alma maters. The doctoral details for both are equal although Marie has four doctoral students listed, whilst Albert has none. Under ‘Known’ for we again have a major difference, Marie is credited with radioactivity, Polonium and Radium, whereas the list for Albert has eleven different entries. Under ‘Influenced’ for Albert there are three names but none for Marie, which I feel is something that should be corrected by somebody who knows their way around nuclear chemistry, not my field. Both of them rack up seven entries under notable awards. Finally Marie had one spouse and two children, whereas Albert had two spouses and three children. In all of this I can’t for the life of me see any sexist bias.

Frankly I find Popova’s, all the more lamentable given that Curie is the recipient of two Nobel Prizes and Einstein of one, comment bizarre. Is the number of Nobel Prizes a scientist receives truly a measure of their significance? I personally think that Lise Meitner is at least as significant as Marie Curie, as a scientist, but, as is well known, she never won a Nobel Prize. Curie did indeed win two, one in physics and one in chemistry but they were both for two different aspects of the same research programme. Einstein only won one, for establishing one of the two great pillars of twentieth-century physics, the quantum theory. He also established the other great pillar, relativity theory, but famously didn’t win a Nobel for having done so. We really shouldn’t measure the significance of scientists’ roles in the evolution of their disciplines by the vagaries of the Nobel awards.



Filed under History of Chemistry, History of Physics, History of science, Ladies of Science

The Huygens Enigma

The seventeenth century produced a large number of excellent scientific researches and mathematicians in Europe, several of whom have been elevated to the status of giants of science or even gods of science by the writers of the popular history of science. Regular readers of this blog should be aware that I don’t believe in the gods of science, but even I am well aware that not all researches are equal and the contributions of some of them are much greater and more important than those of others, although the progress of science is dependent on the contributions of all the players in the science game. Keeping to the game analogy, one could describe them as playing in different leagues. One thing that has puzzled me for a number of years is what I regard as the Huygens enigma. There is no doubt in my mind whatsoever that the Dutch polymath Christiaan Huygens, who was born on the 14 April 1629, was a top premier league player but when those pop history of science writers list their gods they never include him, why not?

Christiaan Huygens by Caspar Netscher, Museum Hofwijck, Voorburg Source: Wikimedia Commons

Christiaan Huygens by Caspar Netscher, Museum Hofwijck, Voorburg
Source: Wikimedia Commons

Christiaan was the second son of Constantijn Huygens poet, composer, civil servant and diplomat and was thus born into the highest echelons of Dutch society. Sent to university to study law by his father Christiaan received a solid mathematical education from Frans van Schooten, one of the leading mathematicians in Europe and an expert on the new analytical mathematics of Descartes and Fermat. Already as a student Christiaan had contacts to top European intellectuals, including corresponding with Marine Mersenne, who confirmed his mathematical talent to his father. Later in his student life he also studied under the English mathematician John Pell.

Already at the age of twenty-five Christiaan dedicated himself to the scientific life, the family wealth sparing him the problem of having to earn a living. Whilst still a student he established himself as a respected mathematician with an international reputation and would later serve as one of Leibniz’s mathematics teachers. In his first publication at the age of twenty-two Huygens made an important contribution to the then relatively new discipline of probability. In physics Huygens originated what would become Newton’s second law of motion and in a century that saw the development of the concept of force it was Huygens’ work on centripetal force that led Christopher Wren and Isaac Newton to the derivation of the inverse square law of gravity. In fact in Book I of Principia, where Newton develops the physics that he goes on to use for his planetary theory in Book III, he only refers to centripetal force and never to the force of gravity. Huygens contribution to the Newtonian revolution in physics and astronomy was substantial and essential.

In astronomy Christiaan with his brother Constantijn ground their own lenses and constructed their own telescopes. He developed one of the early multiple lens eyepieces that improved astronomical observation immensely and which is still known as a Huygens eyepiece. He established his own reputation as an observational astronomer by discovering Titan the largest moon of Saturn. He also demonstrated that all the peculiar observations made over the years of Saturn since Galileo’s first observations in 1610 could be explained by assuming that Saturn had a system of rings, their appearance varying depending on where Saturn and the Earth were in their respective solar orbits at the time of observations. This discovery was made by theoretical analysis and not, as is often wrongly claimed, because he had a more powerful telescope.

In optics Huygens was, along with Robert Hooke, the co-creator of a wave theory of light, which he used to explain the phenomenon of double refraction in calcite crystals. Unfortunately Newton’s corpuscular theory of light initially won out over Huygens’ wave theory until Young and others confirmed Huygens’ theory in the nineteenth century.

Many people know Huygens best for his contributions to the history of clocks. He developed the first accurate pendulum clocks and was again along with Robert Hooke, who accused him of plagiarism, the developer of the balance spring watch. There were attempts to use his pendulum clocks to determine longitude but they proved not to be reliable enough under open sea conditions.

Huygens’ last book published posthumously, Cosmotheoros, is a speculation about the possibility of alien life in the cosmos.

Huygens made important contributions to many fields of science during the second half of the seventeenth century of which the above is but a brief and inadequate sketch and is the intellectual equal of any other seventeenth century researcher with the possible exceptions of Newton and Kepler but does not enjoy the historical reputation that he so obviously deserve, so why?

I personally think it is because there exists no philosophical system or magnum opus associated with his contributions to the development of science. He work is scattered over a series of relatively low-key publications and he offers no grand philosophical concept to pull his work together. Galileo had his Dialogo and his Discorsi, Descartes his Cartesian philosophy, Newton his Principia and his Opticks. It seems to be regarded as one of the gods of science it is not enough to be a top class premier league player who makes vital contributions across a wide spectrum of disciplines, one also has to have a literary symbol or philosophical methodology attached to ones name to be elevated into the history of science Olympus.

P.S. If you like most English speakers think that his name is pronounced something like Hoi-gens then you are wrong, it being Dutch is nothing like that as you can hear in this splendid Youtube video!


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

Well no, actually he didn’t.

Ethan Siegel has written a reply to my AEON Galileo opinion piece on his Forbes blog. Ethan makes his opinion very clear in the title of his post, Galileo Didn’t Invent Astronomy, But He DID Invent Mechanical Physics! My response is also contained in my title above and no, Galileo did not invent mechanical physics. For a change we’ll start with something positive about Galileo, his inclined plane experiments to determine the laws of fall, the description of which form the bulk of Ethan’s post, are in fact one of the truly great pieces of experimental physics and are what makes Galileo justifiably famous. However the rest of Ethan’s post leaves much to be desired.

Ethan starts off by describing the legendary Leaning Tower of Pisa experiment, in which Galileo supposedly dropped two ball of unequal weight of the tower and measured how long they took to fall. The major problem with this is that Galileo almost certainly never did carry out this experiment, however both John Philoponus in the sixth century CE and Simon Stevin in 1586 did so, well before Galileo considered the subject. The laws of fall were also investigated theoretically by the so-called Oxford Calculatores, who developed the mean speed theory, the foundation of the laws of fall, and the Paris Physicists, who represented the results graphically, both in the fourteenth century CE. Galileo knew of the work of John Philoponus, the Oxford Calculatores and the Paris Physicists, even using the same graph to represent the laws of fall in his Two New Sciences, as Oresme had used four hundred years earlier. In the sixteenth centuries the Italian mathematician Tartaglia investigated the path of projectiles, publishing the results in his Nova Scientia, his work was partially validated, partially refuted by Galileo. His landsman Benedetti anticipated most of Galileo’s results on the laws of fall. With the exception of Stevin’s work Galileo knew of all this work and built his own researches on it thus rather challenging Ethan’s claim that Galileo invented mechanical physics.

Galileo’s central achievement was to provide empirical proof of the laws of fall with his ingenious ramp experiments but even here there are problems. Galileo’s results are simply too good, not displaying the expected experimental deviations, leading Alexander Koyré, the first great historian of Galileo’s work, to conclude that Galileo never did the experiments at all. The modern consensus is that he did indeed do the experiments but probably massaged his results, a common practice. The second problem is that any set of empirical results requires confirmation by other independent researchers. Mersenne, a great supporter and propagator of Galileo’s physics, complains of the difficulties of reproducing Galileo’s experimental results and it was first Riccioli, who finally succeeded in doing so, publishing the results in 1651.

A small complaint is Ethan’s claim that Galileo’s work on the laws of fall “was the culmination of a lifetime of work”. In fact although Galileo first published his Two New Sciences in 1638 his work on mechanics was carried out early in his life and completed well before he made his telescopic discoveries.

The real problem with Ethan’s post is what follows the quote above, he writes:

…and the equations of motion derived from Newton’s laws are essentially a reformulation of the results of Galileo. Newton indeed stood on the shoulders of giants when he developed the laws of gravitation and mechanics, but the biggest titan of all in the field before him was Galileo, completely independent of what he contributed to astronomy.

This is quite simply wrong. After stating his first two laws of motion in the Principia Newton writes:

The principles I have set forth are accepted by mathematicians and confirmed by experiments of many kinds. By means of the first two laws and the first two corollaries Galileo found that the decent of heavy bodies is the squared ratio of the time that the motion of projectiles occurs in a parabola, as experiment confirms, except insofar as these motion are somewhat retarded by the resistance of the air.

As Bernard Cohen points out, in the introduction to his translation of the Principia from which I have taken the quote, this is wrong because, Galileo certainly did not know Newton’s first law. As to the second law, Galileo would not have known the part about change in momentum in the Newtonian sense, since this concept depends on the concept of mass which was invented by Newton and first made public in the Principia.

I hear Galileo’s fans protesting that Newton’s first law is the law of inertia, which was discovered by Galileo, so he did know it. However Galileo’s version of the law of inertia is flawed, as he believes natural unforced motion to be circular and not linear. In fact Newton takes his first law from Descartes who in turn took it from Isaac Beeckman. Newton’s Principia, or at least his investigation leading up to it, are in fact heavily indebted to the work of Descartes rather than that of Galileo and Descartes in turn owes his greatest debts in physics to the works of Beeckman and Stevin and not Galileo.

An interesting consequence of Newton’s false attribution to Galileo in the quote above is that it shows that Newton had almost certainly never read Galileo’s masterpiece and only knew of it through hearsay. Galileo’s laws of fall are only minimally present in the Principia and then only mentioned in passing as asides, whereas the parabola law occurs quite frequently whenever Newton is resolving forces in orbits but then only as Galileo has shown.

One small irony remains in Ethan’s post. He loves to plaster his efforts with lots of pictures and diagrams and videos. This post does the same and includes a standard physics textbook diagram showing the force vectors of a heavy body sliding down an inclined plane. You can search Galileo’s work in vain for a similar diagram but you will find an almost identical one in the work of Simon Stevin, who worked on physical mechanics independently of and earlier than Galileo. Galileo made some very important contributions to the development of mechanical physics but he certainly didn’t invent the discipline.


Filed under History of Mathematics, History of Physics, Myths of Science, Newton