by Brian Clegg
The man Faraday was supposed to have stolen the idea from was William Wollaston, one of the scientists whose work Faraday had included in his review. Wollaston had started out as a doctor, but had given up medicine as his eyesight was failing. He had decided (with limited evidence) that electricity spiralled its way along wires like a corkscrew. Wollaston had asked his friend Sir Humphry Davy to search for any evidence of this motion. Davy was unable to do so. However, despite a very limited connection, other than electricity and rotation, between Wollaston’s theory and Faraday’s experiment, Wollaston was convinced that Faraday had stolen his idea. This appalled Faraday. He asked his mentor Davy to help, but to no avail.
While Davy was willing to accept that Faraday did good work, they were miles apart in social status. Davy was a society darling who regularly met with royalty. Early in his career, Faraday had accompanied Davy and the new Mrs Davy on a trip around European scientific establishments. Rather than treat Faraday as an equal, the Davys expected him to take on the role of valet as well as scientific assistant. As far as Davy was concerned, Wollaston, a professional man, was far more of a social equal. He took Wollaston’s side. This was the end of anything more than a purely professional relationship between Faraday and Davy.
Luckily, Davy’s influence was not sufficient to persuade others that Faraday had copied Wollaston’s ideas. And the steady rotation of the wire around the magnet was more than a pretty demonstration: it formed the basis of the electric motor. Faraday had moved out from under Davy’s shadow. Two years later Faraday would be elected to a fellowship of the prestigious Royal Society with only one vote against him. That of Sir Humphry Davy.
It would be ten years before Faraday returned to electricity and magnetism. The pain of the accusations and Davy’s betrayal bit deep. He turned his attention to chemistry and took on the administrative job of Director of the Royal Institution Laboratory, establishing the Friday Night Discourses and a series of Christmas events for children. But Faraday could not resist the challenge of electromagnetism for ever. By 1831 there was evidence that electricity flowing through a wire could generate a current in another, unconnected wire, somehow communicating across space.
This near-magical proposition – induction – was enough to restart Faraday’s enthusiasm for electromagnetism. He constructed a pair of wire coils, wrapping each long, insulated piece of wire around the straight sides of an elongated hoop of iron. He expected to see a steady flow of electricity in the second coil, somehow leaking through to it via the metal hoop, when he powered up the first. Instead there was only a short flow of current in the second coil when the first coil was turned on or off, which soon disappeared.
How, then, was the first coil of wire managing to produce an effect in the second at a distance? As we have seen, Faraday’s first investigation had included the way that a coil of electric wire could produce magnetism. And there was no doubt that magnets worked at a distance – a compass showed that to be the case. When the current flowed in the first wire, then, it would act as a magnet. Faraday realised that if the changing level of magnetism generated a new current in the second wire, rather than electricity leaking across the metal core, it would follow that only a short burst of current would be induced in that second wire. He was soon able to demonstrate the generation of electricity by moving a permanent magnet through a coil, devising a basic electrical generator.
The linkage Faraday demonstrated between electricity and magnetism was difficult for scientists to explain. It was known that when iron filings were sprinkled on a sheet of paper and held above a magnet, the tiny pieces of metal would pull together into curved lines that provided a map of the magnet’s invisible power. With his limited mathematical ability, Faraday was unable to provide equations to describe the effect; instead he imagined the results he had observed in terms of these lines, which he called ‘lines of force’. If he moved a wire near the magnet, the wire was repeatedly cutting through the lines of force, one after another. Each interaction with these imagined lines in apparently empty space generated a flow of electrical current through the wire.
With this picture in mind, Faraday could reconstruct why the electrical induction occurred the way it did. Before the first electrical coil was switched on, the lines of force did not emerge from the coil. But when he started the current flowing, turning the coil into a magnet, the lines moved out into place like the ribs of an opening umbrella. As the lines of force moved out, they cut through the wire of the second coil, one after the other. The way the current pulsed briefly when the magnet was switched on meant that the lines of force did not appear instantly in place when he switched on the magnetic coil; they gradually moved out into position, otherwise the second coil wouldn’t interact with the lines and generate a current. Something was travelling through the air, an invisible magnetic phenomenon.
A matter of speculation
Faraday’s lines of force were visionary, but initially he was wary about revealing their full implications. He could not have forgotten what had happened when Davy had abandoned him. Instead of publishing all his results, he hid his most controversial ideas away in a sealed envelope, dated 12 March 1832, intending it to be opened after his death. And this document went one step further, giving a hint of something JCM would eventually make his own. In Faraday’s mental model, the lines of force moved outwards from the electromagnet when he switched it on. But what exactly did he think was moving? Faraday wrote:
I am inclined to compare the diffusion of magnetic forces from a magnetic pole, to the vibrations upon the surface of disturbed water, or those of air in the phenomena of sound: i.e. I am inclined to think the vibratory theory will apply to these phenomena, as it does to sound, and most probably to light.
This inspired linkage of magnetic vibrations – waves – and the nature of light stayed in the safe inside its sealed envelope until just before nine o’clock on the evening of Friday, 10 April 1846, when legend has it Charles Wheatstone, due to give a lecture on his electro-magnetic chronoscope,¶ panicked and ran out. His friend, Faraday, is said to have presented Wheatstone’s brief talk, then, without time for preparation, is supposed to have given the most inspired lecture of his career: a first insight into the inseparable nature of light, electricity and magnetism.
In reality, the Royal Institution’s records show that on that evening Faraday substituted for another scientist, James Napier, who had given a week’s notice of his absence. It is certainly true, though, that Faraday spoke about Wheatstone’s delightfully named but wholly forgettable electro-magnetic chronoscope. And then, when his colleague’s notes ran out, Faraday began to improvise.
He described light as a vibration, rippling through the invisible magnetic force lines that filled space. This was a remarkable insight to describe in that lecture theatre in 1846. The Royal Institution had moved to its newly-built home on Albemarle Street in London’s fashionable Mayfair. Faraday was positioned at the same polished wooden demonstrator’s bench that still stands in the imposing semi-circular theatre. This was before electric lighting, when the only sources of night-time illumination were oil lamps and candles and the flare of gas lights. To Faraday’s audience, electricity and magnetism were novelties, the inexplicable connection enabling machinery like the chronoscope. Faraday’s leap of genius, connecting the ethereal phenomenon of light with magnets and electrical coils, was inspired.
Faraday would later say that he ‘threw out as matter for speculation, the vague impressions of my mind’. But those impressions were the result of long thought and the outcome was remarkable. Faraday told his audience:
The views which I am so bold as to put forth consider, there-fore, radiation as a high species of vibration in the lines of force which are known to connect particles, and also masses of matter, together. It endeavours to dismiss the aether,|| but not the vibrations.
As we have seen, unlike JCM, Faraday was no mathematician, yet he had produced a visionary idea of the nature of electricity and magnetism
. He believed they produced a sphere of influence around themselves which he would call a ‘field’. Led in part by the way that iron filings line up to connect the two poles of a magnet, Faraday thought of his fields being made up of the lines of force that emanated from magnetic poles or electrical charges. When another electrical or magnetic object broke these lines of force they felt an influence. The field lines were envisaged in a way that tied in with many of the behaviours of electricity and magnetism. For example, when lines of force were compressed together, they repelled each other. And Faraday had also set the seeds of understanding the nature of light by making the remarkable leap from the familiar effects of electricity and magnetism to the concept of waves in a field of force.
All of this would be essential background when JCM began to consider the matter. Although Faraday is rightly celebrated for his contribution to the practical side of devising electric motors and generators, the approach he took theoretically was even more fundamental to the way that physics would develop. His concept of fields, considered by some of his contemporaries as hand-waving, vague nothings, would become the standard way that physicists looked at the world, and remains so to this day, often replacing more familiar models of waves or particles.
Those more mathematical contemporaries who criticised Faraday’s fields pointed out that their own approach, which considered electrical charges and magnetic poles as points that influenced other objects at a distance, obeying an inverse square law like gravity, produced numerical results that could be matched to experiment. However, the fields had a huge conceptual advantage. The point-based mathematical models depended on a mysterious influence at a distance. Just as Newton’s gravitational theory did not explain how gravity worked across empty space (this would take Einstein’s work), so electricity and magnetism could only be explained as causing strange actions at a distance. It was this that Newton’s contemporaries mocked in his approach to gravity as being ‘occult’.
Fields, on the other hand, did away with the need for action at a distance. An electrical charge, for example, acted on the field where it was situated, not on another charge at some distant place. That action then rippled through the field lines to reach the other location. But before the field concept could be considered an effective approach for physics, JCM would have to take Faraday’s qualitative concept and turn it into a mathematical structure that would enable the workings of electromagnetism to be understood and harnessed.
That, though, is still a long way in the future in our story. With the basic ideas of electromagnetism firmly under our belts, let’s rejoin the young Maxwell and his pater on the road to Cambridge.
Notes
1– Roger Bacon’s praise for Peter Peregrinus is from Roger Bacon, Opus Tertius, quoted in Brian Clegg, The First Scientist (London: Constable & Robinson, 2003), p. 33.
* To me, Maxwell will always be Jimmy or Jim, but the wording offends my editor, so henceforth I shall refer to him as JCM.
† Not a demon, then.
‡ Bizarrely, you humans still teach your young children about electricity and magnetism separately. Sometimes I suspect that demons are responsible for your education system.
§ Or ‘nice and cosy’ as we demons would say.
¶ Not as impressive as it sounds: just an electrically controlled clock.
|| The aether or ether was the imagined medium filling all space in which the waves of light were thought to be vibrations. Faraday thought that with fields in place, there was no need for its existence.
Chapter 2
A most original young man
On the way to Cambridge in 1850, Maxwell and his father had stopped off at two great cathedrals – Peterborough and Ely* – so the relatively small Peterhouse, to the south of the city centre where King’s Parade becomes Trumpington Street, may have seemed far less of an architectural marvel. Yet the college should have been an ideal match for Maxwell on his first significant venture outside Scotland. Having his friends Tait and Stewart there to ease the way would have made the transition to Cambridge’s social foibles – rather more sophisticated than Edinburgh at the time – easier to make. Because Peterhouse was one of the smaller colleges, it would have felt a less pressured environment than, say, Trinity or King’s.
Maxwell was given rooms in college with plenty of natural light, something that suited his inclination to experiment – he had a sizeable collection from his home laboratory sent after him on the journey down to Cambridge.† The availability of good space at Peterhouse seems to have been one of his reasons for choosing the college. Mrs Morrison, the mother of Maxwell’s friend Lewis Campbell, noted in her journal before Maxwell had chosen his college that Maxwell ‘came in full of Forbes’ recommendation of Trinity College above all others at Cambridge and that Peterhouse was less expensive than Caius; that the latter is too full to admit of rooms, and freshmen are obliged to lodge out.’ Yet, within weeks of arriving in Cambridge, Maxwell was looking to move on.
Stepping up to Trinity
After a term at Peterhouse, Maxwell transferred to Trinity College – a relatively unusual step to take now, as teaching is largely provided by the university rather than the college. However, in Maxwell’s day, the college you were a member of contributed significantly to the quality of the education you received. Far more direct teaching was provided by the college than is the case now, and some aspects of what was provided at Peterhouse were limited (despite having a good record in mathematics).
What’s more, private tutors were then prevalent and could have a big influence on a student’s success; it seemed that Maxwell wasn’t getting on well with his tutor at Peterhouse. Maxwell’s father had also found out that his son had little chance of remaining at Peterhouse after graduating. There would probably be only one fellowship available for Maxwell’s year, in which it was clear he had several challengers. At the much larger Trinity College, the alma mater and firm favourite of family friend Professor Forbes, Maxwell would have a better chance of gaining a fellowship and staying on.
It’s probably no coincidence that Maxwell was supported in the move to Trinity by James Forbes, who told the master of the college that ‘he [Maxwell] is not a little uncouth in his manners, but withal one of the most original young men I have ever met with’. Not entirely surprisingly, given his background, at this stage in his life Maxwell was a strange mixture of wide-ranging information and a rambling lack of structure. Peter Tait commented that Maxwell had ‘a mass of knowledge which was really immense for so young a man, but in a state of disorder appalling to his methodical private tutor’.
Although Maxwell threw himself into the academic world and thrived at Cambridge, seeming to benefit particularly from the lively social life and intellectual cut-and-thrust that he experienced in Trinity College, he was determined to pack as much into his time there as he could. He had always been enthusiastic for exercise, but with his daily timetable already filled, for a period he devised a way to keep fit despite the restrictions that required students to remain in college at night time. A student with rooms on the same staircase as Maxwell remembered:
From 2 to 2:30 a.m. he took exercise by running along the upper corridor, down the stairs, along the lower corridor, then up the stairs, and so on until the inhabitants of the rooms along his track got up and lay perdus‡ behind their sporting-doors§ to have shots at him with boots, hair brushes, etc., as he passed.
This timing was part of a set of experiments Maxwell undertook to determine the best possible hours for sleep and work – everything about life seems to have provided him with an opportunity for experiment. In 1851, for example, he noted in a letter that he had tried out sleeping after hall (the evening meal in the ornate college hall):
I went to bed from 5 to 9.30, and read very hard from 10 to 2, and slept again from 2.30 to 7. I intend some time to try for a week together sleeping from 5 to 1, and reading the rest of the morning. This is practical scepticism with respect to early rising.
The results of his
experiments were not published, but he seems finally to have settled for more sociable hours.
Becoming an Apostle
Clear evidence that Maxwell’s air of a country bumpkin was wearing off came in his election to the Select Essay Club, better known by the nickname ‘the Apostles’, an elite intellectual club which, as the name suggests, originally had twelve members. It was a university-wide group, but drew largely on a group of wealthy colleges, including Trinity. The club would number the likes of Alfred Tennyson, Bertrand Russell and John Maynard Keynes among its members – and still exists. Unlike the infamous Oxford Bullingdon Club, the Apostles meetings were fixed around tea rather than alcohol-fuelled dining, and it had a far more intellectual basis, though it still suffered from some of the affectations of a secret society. It is highly unlikely that Maxwell would have been considered for such a club if he still came across as ‘uncouth in his manners’.
It was perhaps due to a more sophisticated circle of friends that during his time at Cambridge, Maxwell made his only known foray into spiritualism, then at the height of its public interest. His friend Lewis Campbell notes that even the ‘occult’ sciences, in the then fashionable shapes of electro-biology and table-turning, received a share of Maxwell’s ‘ironical attention’. This was despite a dark warning from Maxwell’s father who noted that an acquaintance had known ‘two cases of nervous people whose minds were quite disordered’ by electro-biology, and warned:
