- Simon Schaffer and Jim Al-Khalili describe the rivalry that James Clerk Maxwell's work led to Duration: 02:55
- Professor Jim Al-Khalili describes James Clerk Maxwell's great breakthrough Duration: 02:54
- Prof Jim Al-Khalili survives nearly a million volts of electricity! Duration: 03:20
- Jim Al-Khalili tells how Oliver Lodge came to be superseded by two of his followers Duration: 02:35
- Prof Jim Al Khalili reads from a dramatic letter written by James Clerk Maxwell and lost for many years. Duration: 01:39
- Prof Jim Al-Khalili explores the birthplace of Scottish mathematician James Clerk Maxwell Duration: 03:05
Revelations and Revolutions
Whilst the 19th century was a time of great electrical experimentation and invention by the likes of Nikola Tesla and Thomas Edison, it also marked a dramatic turning point in the scientific understanding of electricity. For decades electrical engineers had been exploiting electricity without any real understanding of what it was, and as a result, they kept stumbling across bizarre phenomena that they weren't expecting and couldn't explain.
In the academic world, scientists were taking these new discoveries and trying to use them to piece together an understanding of electricity itself.
Michael Faraday had been experimenting with the recently-discovered link between electricity and magnetism, but although he had a natural feel for how things worked he did not have a good background in mathematics and so could not formulate ways of describing and checking his ideas empirically. That task fell to someone else: a brilliant young Scottish mathematician called James Clerk Maxwell.The James Clerk Maxwell Foundation
James Clerk Maxwell worked on the problem of electricity and magnetism for a long time before he finally had a moment of revelation.
Maxwell's mathematical workings were telling him something quite extraordinary - but whilst it was just a series of equations it was all theory. He needed to find something in amongst his workings that could be measured in reality - to check whether his theory had any truth to it. And he did...
Even Maxwell himself didn't understand the full implications of his theory. He had concluded that light was an electromagnetic wave, but he didn't foresee that it was just one small band of wavelengths within a whole vast spectrum of electromagnetic waves. It took many years before other mathematicians, like the eccentric Oliver Heaviside and the Professor in Dublin, George Francis Fitzgerald, actually came to understand the depth of Maxwell's work. Fitzgerald interpreted Maxwell's maths for his physicist friend, Professor Oliver Lodge. But Fitzgerald made a mistake in his interpretation that was to cost Lodge a place in history...
Hertz hits the headlines
The young German physicist Heinrich Hertz is remembered as the first person to detect radio waves, and in doing so he also proved that Maxwell's calculations and theories were all correct. It was a triumph for the group of British 'Maxwellians' like Heaviside and Fitzgerald who had been championing Maxwell's work against the other theories of electromagnetism espoused by continental physicists like Hertz's professor, Hermann Helmholtz.
Professor Oliver Lodge, who had long been seeking a way of producing Maxwell's electromagnetic waves could only stand by and listen as Hertz's ground-breaking work was announced by a triumphant Fitzgerald. Little did Fitzgerald know that Lodge himself had been about to make the announcement that he too had, completely by accident, managed to produce and detect electromagnetic waves using an entirely different method. It was a great disappointment to Lodge, but he bore no grudge. In fact, he admired Hertz's elegant and comprehensive work - the result of years of patient study.
Hertz died tragically young not long after his triumph, and Oliver Lodge saw this as a chance to give a series of memorial lectures in which he could bring Maxwell's work, as well as Hertz's, to a much wider audience.
There has been a great deal of debate about what Oliver Lodge actually did during the lecture he gave in Oxford on the 14th August 1894. It was certainly the start of a revolution, but Lodge's later claims to have transmitted Morse code signals from one building to another are almost certainly incorrect. The inventory of equipment that he had during his lecture includes a Morse tapper, but in fact it seems he was only using this to tap the tube of filings between sending signals. He had, however, been lent telegraph equipment by a colleague after his initial demonstrations in London had proved to be unreliable, and it seems that it was this equipment that suddenly made all the difference to the perception of the demonstration to the assembled crowds.
Lodge's lecture notes were published and widely circulated around the world, and this was to prove another key moment in the story of electricity. It was the moment when two very different people were to become inspired to start experimenting with electromagnetic waves. They would turn out to have very different impacts on the world.
One was the Indian scientist Jagadish Chandra Bose. Bose was fighting a battle against the racism of the day in India. As an Indian his appointment as a teacher at Calcutta College was controversial enough, but he was also offered substantially less pay than his white colleagues. In protest he refused to cash his pay cheques, and as a result he couldn't pursue research that required expensive equipment. Work with electromagnetic waves seemed a promising field - Hertz had left plenty of work still to be done, and Bose could build much of the apparatus he needed himself.
The other person inspired by Lodge's memorial to Hertz was the young son of an Irish mother and Italian father called Guglielmo Marconi. He also saw the chance to experiment with Hertz's waves with equipment he could build himself, but in his case he saw it purely as a means of developing a commercial product, not as a scientific project. He wanted to use radio waves as a means of wireless communication.
Both of these men came to Lodge's attention on one fateful day, at the annual meeting of the British Association for the Advancement of Science as it was being held in Lodge's own home ground of Liverpool.
Marconi's work, backed heavily by the British Post Office, immediately launched the broadcasting revolution. Oliver Lodge, who had long been at the forefront of this research, and who had a better understanding of the science behind wireless communication, was powerless against the commercial might of the young Marconi and his backers. He even had to stand by and see Marconi gain not just great wealth, but the Nobel prize for physics in 1909.
Bose, by contrast, despised patents and commercial gain from science. Working in isolation in India he himself had relied on the openness of others, publishing their work. Commercial telegraph companies had begged Bose not to speak openly of his own work, in which he was developing new and improved receivers for electromagnetic waves. Eventually he gave in to the pressure of taking out a single patent, although he never defended it. It is this patent which has earned him a place in the history books, because he was the first to use the properties of materials called semiconductors, that do not fully conduct electricity.
The birth of semiconductors
Crystals such as lead sulphide, or galena, show semiconducting properties. When touched by a metal wire (called a 'cat's whisker') they conduct electricity much better in one direction than the other. This means that they will 'rectify' a wave signal. The electromagnetic wave causes a flow of electricity first in one direction then another, but the crystal only transmits the electric current in one direction, and so changes that 'alternating current' to a 'direct current' - a current flowing in one direction, and one whose strength fluctuates with the height of the wave. This allowed the changing height, or amplitude, of a wave to carry a signal, leading to 'amplitude modification' or AM signals which could carry an actual sound rather than just an on/off signal as in Morse code. Combined with Marconi's wireless telegraphy system, Bose's semiconductor crystals led to the first 'crystal radio sets'.
This rush of technological innovation was once again beginning to run ahead of scientific understanding. Maxwell's work had explained the far-reaching influence of electricity, well beyond the wires that carried it, and in 1897 the Cambridge physicist JJ Thomson discovered that the electrical current was caused by a movement of tiny particles that became known as electrons.
But still electricity held secrets that puzzled everyone. Even the most dramatic natural phenomena like lightning and the auroras couldn't be fully explained. It needed another great mind to make a breakthrough.
With the breakthrough that light too could be seen as being produced in particle-like packets, called photons, the link between electrons (particles of electricity) and photons (particles of light) could finally be made - explaining the dramatic electrical displays that mankind had wondered at for centuries.
With the understanding of electrons and photons, almost all the mysteries of electricity could be explained. It left only one thing - the behaviour of semiconductors. How could electricity be carried in one direction but not another? It was a question that became particularly pertinent as World War II dawned, as semiconductor crystals became a vital part of radar receivers, a crucial piece of technology in the war.
Radar works by using invisible electromagnetic waves rather like a secret torch beam - sending them out and measuring the faint reflected signals to 'see' objects. Both sides in the war realised that semiconductor crystals were the best way to receive these faint signals, and experiments had shown that the best semiconductor was an element called silicon. But in order to work effectively, the silicon crystals had to be really pure, and purifying silicon was a very difficult process.
The British turned to their American allies for help with silicon receivers, but in Germany, researcher Dr Herbert Matare worked on them, and whilst doing so he noticed a strange effect that would lead him to a dramatic discovery.
Bell Labs' discovery
Dr Matare had discovered by chance that putting two cat's whiskers on the same semiconductor crystal could create a means of amplifying a faint signal. But researchers at Bell Labs in the US came to the same discovery by quite different means.
Whilst working on purifying silicon for radar receivers, researchers at Bell Labs had come across a strange behaviour in an ingot. Impurities in it had been pushed to one end, and now it only conducted electricity in one direction through the ingot. (In fact, not only that, but exposing it to light actually started a flow of electricity in it - a fact that would lead to a secondary branch of research resulting in the very first photovoltaics, or solar cells).
Whilst Bose's semiconductor crystals needed to be touched with a metal wire in just the right place to create a one-way-only flow of electricity, this ingot was a much more reliable way of achieving the same thing, and it was because of the distribution of impurities within it.
The scientific understanding of semiconductors had been improving just before war broke out - ironically it was German and British scientists who had been leading the way (Walter Schottky and Neville Mott). It had become clear that the junction between a semiconductor crystal and a cat's whisker was allowing electrons to flow only one way (known as a Schottky barrier). This is due to the difference between the energy levels of the electrons in the semiconductor and the electrons in the metal - they can much more easily flow one way than the other.
The flow of electrons in the ingot, though, was due to the impurity atoms within it. At one end the atoms of the element boron and been concentrated, and at the other, atoms of the element phosphorus. Phosphorus has a 'spare' electron that is easy to lose, whilst boron easily accepts another, so given a bit of a boost of energy (such as from photons of light), a flow of electrons could be started from the phosphorus end to the boron end.
During the war, Bell Labs cut these 'junctions' they could find out of any ingots that they sent to their British or other collaborators. They didn't want anyone else stumbling across this effect. Although they didn't have time to investigate it further under the pressure of war, just as Herbert Matare didn't have time to investigate the effect that putting two cat's whiskers on the same crystal created.
Once the war was over, though, a research group at Bell Labs started work on the effect. The head of the group, William Shockley, had a brilliant theoretical mind. He understood the flow of electrons in semiconductors, and thought that there might be a way of using this new effect. He came up with a theoretical design for an amplifier using just a solid block of silicon with impurities. But however hard he tried, he couldn't get it to work himself, and left the task in the hands of his colleagues Dr John Bardeen and Dr Walter Brattain. Whilst experimenting, they came across exactly the effect that Dr Matare had found - putting two cat's whiskers on the same crystal of silicon to amplify a signal. It wasn't at all what Dr Shockley had predicted, but it worked - sort of, and with his unique theoretical grasp, he was the first to understand how.
The junction transistor
Dr Shockley's colleagues at Bell Labs were awarded a patent for the 'transistor', but Dr Shockley's name wasn't on it and he was incensed. He worked in secret on his original design, convinced that now he understood how the effect was working in this 'point contact transistor' he could get his own design to work, and that it would be more reliable.
He thought he could replace the two cat's whisker junctions with two impurity junctions (known as 'p-n junctions') within a single ingot of silicon. The cat's whiskers were the weak point in the original transistor design - they were difficult to position and delicate. If only he could create a single block of silicon with impurities in stripes to create two junctions inside it then it should, theoretically, be a reliable alternative. And luckily for him, another of his Bell Labs colleagues had worked out a way of doing exactly that.
William Shockley finally managed to create his own version of the transistor - called a 'junction transistor' - which was much more reliable and easy to mass produce than either Dr Matare's or his Bell Labs colleagues' versions. Finally, he had a patent in his own name, and when the Nobel Prize committee awarded the 1956 Nobel Prize for physics, they awarded it jointly to William Shockley and his Bell Labs colleagues John Bardeen and Walter Brattain. They did not recognise the achievements of Herbert Matare and his colleague Heinrich Welker.
The birth of Silicon Valley
Dr Shockley had a difficult personality, and he had fallen out with his colleagues over the development of the transistor. He left Bell Labs and returned to his native California, where he set up Shockley Semiconductor Laboratory in the fruit-growing region of Mountain View in 1956. It was this choice of destination that would eventually lead to the development of Silicon Valley. No ex-colleagues would work with Shockley again, and so he recruited the best young graduates. However, even they could not work with him for long, and eight of them eventually left Shockley in one revolutionary move. They set up their own company nearby, called Fairchild Semiconductor, and ran it in as different a way as they could from Shockley's overbearing management style. It was a style and ethic that would infuse all the companies that then spawned from Fairchild, such as Intel, and the next generation of companies inspired by Fairchild's founders, such as Apple and Google. They developed the concept of silicon transistors into the 'integrated circuit' or microchip - a single one of which now contains several billion transistors.
Dr Shockley's ex-colleague from Bell Labs, Dr Bardeen, also left, but he returned to academia. He turned his mind instead to another problem of electricity, perhaps the greatest unsolved mystery of all: superconductivity.
Dr Bardeen and his colleagues seemed to be able to explain how some substances could conduct electricity with no resistance whatsoever at very low temperatures. But in 1986, a new compound was discovered that broke the theoretical temperature limit that the theory (known as BCS theory) predicted for superconductivity. It had to be working in a different way.
This new breakthrough started a flurry of research into superconductors. The President of the US made bold announcements of the dawn of a new electrical age. That new age has been a while coming. No one has yet explained fully how these new superconductors are working at these relatively warm temperatures. The limits are constantly being pushed by experimentalists working with trial and error, although as yet no superconductor has been found that works at room temperatures.
Once again, invention has run before understanding. What is needed now is another great theoretical mind to explain this last great unsolved phenomenon of electricity.
It is clear that the long-running story of the scientific understanding of electricity will continue for some time to come.
The Maxwellians by Bruce J Hunt
Syntony and Spark: The Origins of Radio by Hugh Aitken
Oliver Lodge and the Invention of Radio by Peter Rowlands and Patrick Wilson
Jagadis Chandra Bose and the Indian Response to Western Science By Subrata Dasgupta
Crystal Fire: The Birth of the Information Age by Michael Riordan & Lillian Hoddeson
- Jim Al-Khalili
- Jim Al-Khalili
- Alex Freeman
- Alex Freeman
- Alex Freeman
- Alex Freeman
- Series Producer
- Steve Crabtree
- Series Producer
- Steve Crabtree
- Executive Producer
- Tina Fletcher-Hill
- Executive Producer
- Tina Fletcher-Hill