In Our Time - The Invention of Radio

Episode Date: July 4, 2013

Melvyn Bragg and his guests discuss the invention of radio. In the early 1860s the Scottish physicist James Clerk Maxwell derived four equations which together describe the behaviour of electricity and magnetism. They predicted the existence of a previously unknown phenomenon: electromagnetic waves. These waves were first observed in the early 1880s, and over the next two decades a succession of scientists and engineers built increasingly elaborate devices to produce and detect them. Eventually this gave birth to a new technology: radio. The Italian Guglielmo Marconi is commonly described as the father of radio - but many other figures were involved in its development, and it was not him but a Canadian, Reginald Fessenden, who first succeeded in transmitting speech over the airwaves.With:Simon Schaffer Professor of the History of Science at the University of CambridgeElizabeth Bruton Postdoctoral Researcher at the University of LeedsJohn Liffen Curator of Communications at the Science Museum, LondonProducer: Thomas Morris.

Thank you for downloading this episode of In Our Time, for more details about In Our Time, and for our terms of use, please go to BBC.co.com.uk slash Radio 4. I hope you enjoy the program. Hello, on the 2nd July 1897, a young Italian living in Bayswater was awarded a patent for a new device. The official document explains that, according to this invention, electrical actions or manifestations are transmitted through the air, earth or water, by means of electric oscillations of high frequency. The inventor's name was Marconi, and he was 23. Today we'd call these electric oscillations radio waves,

and Marconi had devised a means of sending telegraphic signals great distances by using them. His invention led eventually to the development of modern radio communication. But although Marconi is often described today as the father of radio, the story of the technology began several decades earlier and involved a number of other celebrated scientists and engineers who paved the way. with me to discuss the invention of radio are Simon Schaffer, Professor of the History of Science at the University of Cambridge,

John Liffin, curator of communications at the Science Museum in London, and Elizabeth Bruton, a post-doctoral researcher at the University of Leeds. Simon Schaffer, the story really begins, as I understand it, in the first half of the 19th century, the work of two scientists, Faraday and Orsted, who investigated the nature of electricity. Can you tell us about them and where they took us? Yes. For a very long time in human history, almost all information was communicated at the same speed as humans could travel. And it's in the early 19th century that electrical technology and electrical experimenters began to design systems that could in principle at least transmit messages using electricity. In 1820, Hans Christian Ersted, who was professor in Copenhagen, showed that a current carrying wire can affect at a distance. position of a compass needle. And in trying to replicate those experiments and explore what they

meant, Michael Faraday, working in London, showed, first of all in 1821, that magnets and current carrying wires could rotate around each other. And then a decade later, his work on electromagnetic induction showed that changing magnetic fields could induce electric currents. So already by the 1830s, it became clear to a relatively large number of scientists and engineers, that in principle it must be possible to use electricity to transmit something like messages at a distance by affecting the position of a needle. What possibilities did they see then? We're talking about Faraday.

It always tickles me that it was working three or four streets from where we're sitting now in that wonderful little laboratory, who's still there. What possibilities did they see then for this discovery? There was a very widely shared idea that if a current carrying wire can affect the position of a needle, of a magnetic needle, one ought to be able to lay electric conductors over, in principle, immense distances, over land and underwater, linking cities, railway systems, linking countries by transmitting currents over vast distances, so that making or breaking a current would make a needle far far away shift its position. And then imagine that around the end of the compass you set up, first of all, a scale of letters

so that the needle can point to different letters. You could send a message that way. Or perhaps more plausibly, and this was the achievement of the 1830s and 40s, you could send some kind of code already by the late 30s and mid-40s. workers like Samuel Morse in the United States were beginning to work out forms of coded message which became more efficient and technically viable. And then enter one of the great physicists of all time,

much admired by Einstein, that's a genius. James Clark Maxwell, is any way to tell us briefly what his breakthrough was in the 1860s? Come on, Simon, you can do it. What Maxwell was impressed by was the success of the Telegraph and some of the difficulties that the electric telegraphists faced. Faraday's demonstration in 1853 and 4 of why there were big problems about telegraphic communication

was announced more or less the same months as Maxwell graduated from Cambridge. And for a lot of his career, Maxwell was obsessed by those kinds of problems. In the early 1860s, what Maxwell did was to put together in a coherent theory all the knowledge about electric and magnetic effects and their mutual interaction in a system of equations which showed to Maxwell's satisfaction anyway that in apparently empty space there are electric and magnetic energies which oscillate in the form of a wave and this wave of electromagnetic energy he showed travels at the same speed as the speed of light. And therefore, he concludes, already in the early 1860s,

that whatever it is that carries light through space, also, in principle, is responsible for electromagnetic action. And that's a germ of the possibility of electromagnetic radiation. Thank you. John Liffin, the telegraph, which Sam is referred to in the 1860s, can you tell us a bit about its development and invention and what it was doing then? Yes, it started in a practical form in 1837 in London, in Britain, when a practical man, William Cook, inspired by seeing a demonstration of ersted's effect while studying in Germany, realized that this was his life's work. He was a soldier. He'd just retired. He was looking for a new direction, but he wanted to make money. So he made his own copies, brought them back to London, tried to make them work, but not a scientist. He didn't really get them working properly.

And through a convoluted series of contacts, including consulting Faraday, he made contact with Charles Wheatstone at King's College London. Wheatstone, a scientist who did understand the electricity of telegraphy. together they produced a practical system which they demonstrated in 1837. What did this system demonstrate? Because for the first half of this programme, at least, we're going to go step by step stage, which is absolutely fascinating about the creation

and refinement of knowledge by various men, it is exclusively men, in Europe and in America and India and so on. So what did he add to what had already been discovered by Faraday and Orsted and Clark Maxwell? What Cook and Wheatstone added was a system that worked and could be used to practical effect by anybody else to pursue their particular business. So turning it from a laboratory demonstration by scientists who were not entrepreneurs and were interested in just studying what the effects were to something which people could take and use and communicate at a distance and make their... business more efficient. Another pioneer, we come to a man called David Hughes.

He seems to be one of the first to observe electromagnetic radiation. Can you tell us about him and his work? David Hughes, born in Britain, studied in the United States, became a professor of music. He's another one of these pioneers who had nothing to do with the engineering or science of the subject. eventually he became interested in electric telegraphy and his particular contribution was to produce a very much more efficient printing telegraph.

Now for a printing telegraph you need to have absolute synchronism of the sending and the receiving end so that if you press a key marked A the printing letter at the other end will print A and he used his musical knowledge to produce a system which provided absolute synchronism of the system that way. Now, he was quite clever because unlike many of these developers, he managed to hang on to the money he made. So he had plenty of time to spare. After he'd given the electric telegraph, printing telegraph to others to follow,

he was able to relax and he came to London from Paris with his wife and they sat up a flat in Great Portland Street just around the corner from here. I looked at the blue plaque this morning. and he experimented in his workshop upstairs using just the bits and pieces and wood, sealing wax, bits of wire and amongst other things he invented the microphone. But he also invented the metal detector,

which is a means of measuring induction. And it was through a fault in this induction balance that he made his discovery. Did these people know each other? It's almost like a baton being passed on, Did they know each other? I'm not totally personally. Did they know of each other's work?

Certainly Hughes, of course he would have known of Cook and Wheatstone's work. He may have been aware of James Clark's Maxwell's researchers, but Maxwell's output was in very refined mathematics. Very few other physicists and scientists could understand his work, which is why it wasn't immediately picked up. So he was probably working pretty much in isolation. He was more of a technologist, so he was. was interested in practical things like Bell's telephone, which had just been invented. But it was

this fault on the induction balance, which he heard through a telephone he'd built and experimented with. He discovered that he could hear a click in his earphone, even when he disconnected the telephone from the equipment. And he made a little device to replicate the fault, which was actually a wire sort of coming apart from the battery, causing a little spark. And he made a little device, That little spark caused electromagnetic radiation, and he walked around his house and out in the street with his detector and his earpiece, and he could still hear the clicks. But he didn't know it was electromagnetic radiation.

And a few years later, monstrous BBC buildings spring up in his very footsteps. Magnificently monstrous, of course. Elizabeth Bruton, the first generally accepted proof of the existence of the electromagnetic waves It came from a German. People who have heard this name, Hertz. Can you tell us about him and how did he prove it? Well, Hertz was a very intelligent man. He was a German trained in science.

And he was one of rare people who could actually understand the theory of Clark Maxwell and wanted to try and demonstrate in a physical laboratory that these radiating electromagnetic waves existed. So he needed to be able to produce electromagnetic waves and he also needed to be able to produce a way of detecting them. It's possible for you to tell us how he experimented with. He was the proof of Maxwell's equations.

He delivered the proof, which is greatly important. Can you tell us, tell me so I can understand, how he did that? Okay, well, his background was in mathematics, but he trained as a scientist, and he worked in Berlin with an expert signed von Helmhurst, and he wanted to figure out if he could detect them. So he built apparatus and including a spark gap. So he could see a spark literally going across quite a narrow gap.

And using this apparatus, he was able to produce electro-meneidic waves, but more importantly, he was able to build a very, very crude detector of electromagnetic waves. And he was the first person to be able to produce this apparatus and to prove conclusively, both practically and theoretically, that these were Clark Maxwell's electromagnetic waves that they existed and that he was producing and he was detecting them. Interesting, isn't it, that he transferred this into reality in his laboratory in Germany. I love the way knowledge is hopping from place to place,

and people are just taking it on. So have we said enough about Hertz? Yes. So can we talk about the British Post Office in the 1880s? Yep. So we've got Hertz doing some pretty intricate physical. research. And at the same time, in a very different way, we have much more practical on-the-ground research being conducted by the post office in the 1880s, who we wouldn't necessarily, today,

at least, associate with telecommunications. But they had a massive engineering department at this time, and a key engineer who would later rise to being engineer-in-chief of the post office was William Preece. And during this period, obviously, they have the telegraph, as John has talked about, and they've also got the telephone. And they notice quite a very important. on that there's interference between the two, even over quite long distances. And obviously this is a problem in terms of the security and privacy of telegraphic and telephone communications. So they look into this and at first it's a problem and they solve it by having sort of twisted wires. But then they realize, well, this could be a way of communicating without wires, at least without wires between the two points.

And the main thing that they need this for at the time is for lighthouses. So they develop basically two systems at this time, one using induction and one using conduction. So the system using conduction is sort of generally through water or sometimes through earth. And the induction system is basically you have a very, very long wire equal to the distance that you want to transmit. And then you have a shorter wire somewhere else, either on a boat or on an island. And you can use this to induce signals across the gap. it's not very practical because you essentially have to have a wire as long as the distance you want to communicate and it's got a maximum transmission range of about 10 miles

but it is the best available solution at the time and this is obviously a period before the publication and discovery of what we now call herzian waves or radio waves so it's the best available solution and it's put forward by a state body at the time which is the post office meanwhile the telegraph and the telephone where are they in the development of things Well, I mean, the telegraph is just being developed incredibly. You know, it's going across countries, under seas, you know, between continents. That's the major telecommunication system of the time. And in Britain, the inland domestic telegraph is managed by the post office

to a monopoly that they're granted in the late 1860s, which is why they have such an active role in telecommunications during this period. And great engineering features like laying that cable under the Atlantic? Well, they're their domestic telegraph not. international telegraph. But I mean, you have incredible developments in telegraphy at the time. You've just telegraph thousands and thousands of miles of telegraph cables

going everywhere. Simon Schaffer, in this eventful journey, we go to France. The Frenchman called Eduard Braunley. What did he add? So, Bronley was a physicist of genius. He was a deeply conservative Catholic who believed in sound

salvation and cleaning up the nation and so on. he left the Sorbonne for the Catholic Institute under a certain cloud. He performed a series of extremely ingenious experiments using initially the apparatus that Hertz had designed in the late 1880s. It was very well known when Brunley began his experiments that if you electrified dust or bubbles or metallic, particles, they tend to cohere. They tend to come together and attract each other in a slightly strange way.

Brunley was working on this and in 1890 realized that that phenomenon in which if you electrify a metallic powder, for example, it tends to associate and coagulate, could be used to detect the presence of electromagnetic radiation. So if you use a spark gap as a transmitter, what Brunley showed was that you could use this device to detect the presence or absence of an electromagnetic signal. And that was what you might need, crucially, for the possibility of telegraphy without wires. Because this was a system, this was going to be a system, this is what Bromley contributed to, in which all you needed to do was to know whether the signal had arrived or not. So it was a kind of on-off switch.

And Brunley's device of metallic powder cohering or separating was just what was needed, he argued, to set up a reasonably viable kind of detector. What's been thrilling for me, really thrilling, reading about this, is that man after man, person after person, has been doing what we would now call pure science. So far, there's not the slightest possibility of any commercial, and they're allowed to do it, they do it, they get on with it.

And what it's going to lead to is massive commercial potential, massive development in human society in so many ways. It's just another little nod to say that pure research is the basis of so much that's happening in this world now. I think that's absolutely right. I mean, certainly the work we've talked about, whether you think of Hertz or Brunley, is work which, or indeed Maxwell, is work which is no doubt inspired by the state of technology of the time,

but it takes place on a scale and with an intensity that required, it seems to me, a kind of cloistered physics, a physics where you could afford to fail, where intense study of the kind that Brawley engaged in, was not only necessary, but it was viable. It was possible for him to spend a long time exploring the details of the device that he was designing. And when he designed that device, he had no commercial interest in view, quite the reverse, in fact.

Enter Oliver Lodge, John Liff, and a British scientist, so back to the Faraday tradition as he were in a clockwork. What improvements did he make? Lodge, excuse me, studied Hertz's work. and indeed he met Hertz and when Hertz visited Britain, he stayed with Lodge and they discussed matters. But Lodge had been independently studying the phenomenon of electromagnetic radiation as well. He had a lot to talk about. So he experimented, he was working on lightning conductors and he was using this phenomenon of the powders,

but he also realised that lightning doesn't necessarily go to the path of least resistance. It goes down through the air to somewhere which has the most inductance or capacitance to receive it. Now, this brought him into conflict with priests of the post office because Lodge was a scientist, it was a professor at university college in Liverpool, Priest was a practical man, and in the early 1890s there was a certain edginess between their relationship later patched up, because priests didn't really understand the science that was developing, whereas Lodge did. Anyway, so Lodge took these researchers, and he worked out that you could transmit and receive. The important thing was a detector.

His first detector was, well, he called it a co-heera. you're going to detect? It was the electromagnetic radiation and it's this on-off switch. His first detector was an infinitesimally small gap between two spheres where it is thought that the corrosion, the abstract corrosion that develops on the face of these spheres would break down in the presence of electromagnetic radiation. But a tap, a knock, a physical knock against its apparatus would restore this non-conducting state. state. This worked, but then he took Bronley's tube, the filings tube, and he found that worked better, and he began to demonstrate using his spark gap transmitter and his Bromley tube. But he too was a scientist with a busy schedule in his life, not an entrepreneur, and he, although he showed that you could transmit and receive dots and dashes, he did not at first send intelligence. So we're still at the stage where, and other scientists has taken, refined the process a little bit further forward,

but hasn't started to communicate. Is there a sense that telegraphy, and that says, the telegraph is working so well that why need we bother with this other thing? Oh, there's certainly an element of that in the same way that why do you need the telephone because the postal system is so good. And that was an attitude that the post office had in the 1880s. Elizabeth Bruton, Lodge also invented something known as Syntony, which we know as tuning,

which became very important, very, very important later. Can you tell us how he did it and why it's so important? Well, Lodge's perhaps most important contribution to the field of radio is indeed Sintini. So up to this point, we have spark-gap transmitters and they essentially broadcast, to use a historically incorrect term, over an incredibly wide range of frequencies. So if you have one transmitter and then, let's say four miles down the road,

another transmitter. You can only use one at the same time. Otherwise, you have interference. And if you've got receivers, you've got potential interception. So this is a major problem. It means that wireless telegraphy, these kind of systems just isn't very practical. So Lodge comes along and based on his sort of deep knowledge of electrical resonance, he develops a thing called Syntony, which is essentially you have selective tuning to a particular, well, nowadays to particular frequencies, then to a particular band of frequencies. So, for example, you could have your wireless transmitter on tune A, for example, and two miles or a mile or how many, a short distance away, you have a different station on tune B, and they can transmit at the same time.

And if the tunes are sufficiently far apart, there will be no interference. And that's essentially lodges most important contribution to radio. And he, I know we're coming back to this later in talking in relation to Marconian patent, but he does actually patent this. So he is starting to think about this not just as a scientist. So he patents this in May 1897. And in fact, you can argue that this is probably one of the most important patents in terms of radio communications. Yes, it is extraordinary to manage to separate those?

Is there anything you can tell us a bit more about it, just to annihilate for, physics illiterates like myself. I'll bow to John Niffon and this one actually. Well, it's something I think I might struggle with too, but it's the relationship of the capacitance of a circuit and in the inductance of a circuit. If you change the inductive nature of your receiving circuit, then you will go out of tune with your transmitter.

So you have to set up your transmitter so that what you're saying, send is within a particular range of frequencies and you can arrange for your receiving aerial and your detector to only resonate at that particular range of frequency.

The analogy that Lodge used was with musical sounds that if you hit a tuning fork a particular note then another tuning fork that is exactly the same will resonate nearby because it will

take the vibrations passing through the air and it will cause those vibrations be sufficient to make it shake at that frequency. I mean, like the musical glasses as well. Music comes into it once again. Simon, Simon Schaffer, many countries seem to have

their own inventors. The American candidate is Nikola. Tesla. What did he contribute? Tesla was an electrical engineer and entrepreneur of genius. That doesn't mean everything he did was successful or indeed rational.

He was a Serb by birth, who trained in Budapest in Hungary in engineering and science. In the 1880s, he worked for Edison's company in Paris and then in New York. And then, like a lot of people Edison employed, he broke with Edison and set up his own business and collaborated with the great American engineering company Westinghouse. What mattered to Tesla's work for radio was his initial

fascination with alternating current systems. This led to a story we don't have time to go into called the War of the Currents. Another time. E.NTS. Between Edison's system and the Westinghouse Tesla

system, which in many ways Tesla won. he designed generators and dynamos that produced very high voltage and therefore low current systems of power transmission which were extremely efficient and in the late 80s and early 90s he designs a series of coils which can both transmit and receive electromagnetic radiation

So where are we in the story now? What does that mean? That meant at least this was Tesla that you could design an economically viable, very long range, very high power system of signal transmission of electromagnetic radiation. How would it be better? How did it convince people it was going to be better than the telegraph, which was sweeping the world? It was better, at least though Tesla and his allies argued in two rather obvious ways.

One was that you would save on the technical challenges and difficulties of laying cable. This was, after all, wireless telegraphy. The word radio, as we now use, it doesn't appear until much, much later after the First World War, really. Still hasn't appeared for some people. And it still hasn't appeared. Even though radio is marvelous and wonderful, it still hasn't appeared. No, wireless, you see. People like saying wireless.

And the other advantage for Tesla was the possibility of using this system of transmission, not just to transmit messages, but also to transmit power. That was a visionary scheme that Tesla was committed to. What he was really good at, or one of the things he was really good at, was publicity. Publicity matters to our story a lot. So in 1898, Tesla took over Madison Square Garden in New York City and showed a huge audience, a radio-powered boat, which would travel around on water without wires, without anyone seeming to direct it, simply by radio control. And he proclaimed this magnificently in the newspapers as the first of a new breed of automata. So there was a vision with Tesla, which some of his contemporaries share, of a cosmology of wireless,

an entirely new social order, perhaps, would be summoned into existence. John Liffin, we're just going towards the end of the list all we get to Markovett, so I'd like you to mention J.C. Bose, the Indian scientist, great Indian mathematician and scientist. Yes, Jagatiss Bose, a very important scientist. Yes. Professor of Physical Science at Presidency College Calcutta. he too studied electromagnetic radiation. He was inspired to do so by reading Lodge's account of his researchers with Hetz.

So the word is beginning to get around. And Boas found that the co-heroes he was working with in Calcutta in this warm and moist climate were not very effective. So he tried to find another form of detector. And he actually produced, I suppose, almost prematurely, but it's a key device these days, the semiconductor diode detector. Now that's sort of a rather long-winded expression. But the key thing in wireless telegraphy is receiving those signals,

catching them from the air and making them useful to you. And the semiconductor diode detector placed dissimilar metals or other semiconductor materials in conjunction with each other, so either mercury and iron or mercury and coppery and copper. carbon in a little glass tube and the fact of them touching would cause the incoming, the electromagnetic radiation to have, it would give them a rectifying action. The rectification converted the alternating current, the oscillation of the electromagnetic radiation into direct current, sort of direct current, and then you can work with that in your receiver.

There are others that's pop off in Russia and so on, but we must move to Marconi now. Simon Shabberg, Can you tell us a little about his background in early life, and then I'll turn to Elizabeth? Marconi was not from a humble background, unlike some of our heroes in the story, a very wealthy family. His mother, this is relevant to his success, was Annie Jameson from the famous Irish family. He grew up in the countryside near Bologna. He read Lodge's work and Hertz's work. Heutz died tragically young in 1894,

and Marconi was exposed to the account of Heutz's work that the local physics professor, Agostina Rigi, in Bologna, provided him with. So in the early 90s, Marconi began to do a series of, again, extraordinarily ingenious experiments on atmospheric. He was in his late teens and early 20s when he started this work. He used the family butler as his lab technician. He set up apparatus that would warn of thunderstorms and lightning strikes. He invited his parents in to see the results.

And it seems to me that what was stunning about Marconi's early work from the get-go is that he almost uniquely understood that electromagnetic radio, could be understood as a form of telegraphy. Most previous experimenters in this field understood electromagnetic signaling as a kind of optical signaling. What Marconi understood was that if you re-engineered electromagnetic signaling as though it was wireless telegraphy, you could increase the power and the reliability and the rain. of radio signaling, and that was genius. Elizabeth Bruton, how did he build on the work of others?

Marconi, as Simon's mentioned, studied Hertz and others. Can you just show him? He's some sort of endgame in this that we've been leading to, because he understands it and he's the first great commercializer of it and popularized of it, so he brings a lot together. Can you just tell us what he did bring together? Yeah. So, I mean, Marconi's contribution to the field of radio, is definitely not as a scientist or an engineer.

He puts together the work of those that have gone before. So if you looked at his black box, which is on display in the Museum of History Science in Oxford, and you opened it up, you would see apparatus that was completely familiar to scientists and engineers and indeed telegraphists of the time. So he is using Brannley's co-hearer, well, he's using Lodge's version of Brannley's Coherer.

he's using a Morse key that you would recognise from any telegraphy station. He's building on the work of Hertz. He's using electrical battery technology that would be familiar to almost any electrical engineer of the day. But he puts it together. He develops an aerial system, which means you can start transmitting instead of over distances of feet and yards, or measures I suppose in modern distances. You now can start communicating over distances of maybe a mile or a mile and a half. half and you can build it up.

So he seems to understand, as Simon has said, inherently that telegraphy is how you're going to develop, that wireless telegraphy is a practical commercial system and that you just need to work in terms of

developing the reliability, the practicality and the distances over which you're going to communicate. That was very clear. So John Liffin, once he gets that going, how long does it take you to make them massively? What's the apparatus able to do now? It's progressive in the next three or four years. As each step goes on, the distances become greater and the potentiality becomes more important. Marconi started his first company to

develop commercially at White's Day of System in 1897. He'd been backed by priests of the post office, which is interesting because Priests had not really been interested in Lodges' proposals and developments. But when Marconi came along with something very similar, priests adopted him. But it didn't take very long for Marconi to decide he wanted to go his own way. So he developed a company. And within three years... In Chelmsford. In Chelmsford, yeah.

Within three years, it's beginning to get a bit upish. decided that it might be possible to communicate across the Atlantic. Can you just take us on that next stage, Elizabeth Bruton? Because it suddenly went well, didn't it? Worldwide. Yeah, so it's... What were the incidents that helped him, sorry? There were two... Well, I mean, this is incredible, because you look four years previously,

and they're not even sure if you can actually transmit wirelessly over water. We've talked a lot about the contribution of scientists and how Marconi built on the work of scientists, but now it's almost like he's stepping he's stepping beyond the known science and he's developing the technology and it's almost that the science is lagging behind that the understanding

so he starts testing over longer distances he goes across the channel so the English Channel in 1898 and then he starts thinking we need something they say it again this ties to test he needs some kind of publicity

because he's got a company and he needs to make money and he needs to show that wireless telegraphy has a purpose that over shorter distances over land you've got telegraphy already we've said this before, why would you need that? So it's the maritime application that is very important but he also needs to show the long distance range

because if you've got ships with wireless they're going to need to communicate with each other but they're also going to need to communicate with land stations so communication across the Atlantic does in a slightly sort of odd way is part of this so he starts he puts a wireless station in Poldo

in Cornwall which obviously pretty almost as close as you can get to America if you're not on Ireland and he has one in the US and then eventually in Canada and in 1901 he transmits across the Atlantic and this is incredible

John you're going to come in well I just observed that this is an example of somebody who isn't a scientist and doesn't understand the physics, not realizing something can't be done because, of course, you can't transmit across the Atlantic, because the frequency range won't let you. But not knowing this, he went ahead anyway. He had the benefit of Alexander Fleming to help him as a scientific advisor. But I would just like to comment on this Atlantic crossing that the key device that received the signal across Atlantic was Bose's semiconductor diode detector. The other equipment didn't work, but Boe's

detector did, but Marconi did not credit Boes with the invention. You raised on his own, didn't he was a cat who walked alone, Marconi. Yeah, he was also, he very rarely acknowledged, I mean, we've talked a lot

about how he's building on the work of previous scientists and engineers, he very rarely acknowledged this. I mean, he denied reading Lodge's work on Hertz, which is incredibly unlikely. You know, he denied that he was using Bose's apparatus. He denied that he was infringing other people's patents, but was very, very careful of defending his own.

We've been much more generous than Marconi ever was. This is a man whose best man at his wedding was Mussolini. Second wedding. I think we'll just move on in the case. Lovely as that is, we're going to talk about the next thing, Simon, and we haven't got a great deal of time, so it's accelerated time. The human voice, getting that involved, and then that was clinched everything. This, right, way go.

So remember that everything we've been talking about up till now is about code signaling. It's not about transmitting noises. In the 1890s, Canadian electrical engineer and scientist, Reginald Fessenden, working first for Edison, then fired by Edison, then working as university professor, then for the American weather service along the east coast of the United States. worked out a system which strongly resembles that of Tesla, which was capable of generating regular and reliable continuous radio waves. What Fessenden then did, where in 1900, was to put a microphone into the circuit, a microphone just like that of David Hughes, and use the radio waves as a carrier signal whose amplitude would be modulated by the sound

that the microphone picked up. By 1906 Fessenden was able to do something very like broadcasting on Christmas Eve of 1906 Fessenden broadcast handles Largo one of the first pieces of noise broadcast by radio. Very briefly John really very briefly how long did it take to lift off we've got 1906 and then what?

What course lift off was the invasion of of the thermionic valve, which occurred in stages, which we can't go into now. But that meant that you could get away from using rotating machinery to develop your continuous wave. You could cause a vowel to oscillate, and you could get real power to transmission. So by about 1920, you could have broadcasting stations,

and broadcasting, as we know it today, began in the United States in 1920. Is there anything else to add vitally to this picture, Elizabeth? I would say that we like to think of heroes in this story. We like to think maybe of continuous development that one scientist or engineer or entrepreneur passing a baton from another and it's quite a continuous narrative.

This definitely isn't the case at all. It's a collective contribution of a community of scientists, engineers, physicists, odd bodies, entrepreneurs, everyone and anybody to this wonderful development of broadcast radio. Thank you very much. Thank you, Elizabeth Bruton, Simon Schaffer and John Liffon. We'll be back on September 19th with the programme on Blaise Pascal,

the 17th century French scientist and philosopher. Thank you for listening. There are many more Radio 4 arts and discussion programmes to download for free. Find these on the website at BBC.co.uk slash radio 4.