In Our Time - Magnetism

Episode Date: September 29, 2005

Melvyn Bragg and guests discuss the history of magnetism. Pliny the Elder, in his Historia Naturalis, tells a story of a legendary Greek shepherd called Magnes who, while guiding his flock on Mount Ida, suddenly found it hard to move his feet. The nails of his sandals held fast to the rock beneath them, and the iron tip of his crook was strangely attracted to the boulders all around. Magnes had stumbled across the lodestone, or 'Magnetite', and discovered the phenomenon of magnetism. Plato was baffled by this strange force, as were Aristotle and Galen, and despite being used in navigation, supposedly suspended over the body of Mohammed and deployed in the pursuit of medical cures. St Thomas Aquinas thought magnets had souls. it was not until the late 16th century that any serious scientific attempt was made to explain the mystifying powers of the magnet. Descartes developed a particle theory of magnetism but the great Isaac Newton fought shy of the problem of what caused magnets to attract and repelWho pioneered the study of magnetism? What theories did they construct from its curious abilities and how was the power of the magnet brought out of the realm of magic and into the service of science? With Stephen Pumfrey, Senior Lecturer in the History of Science at the University of Lancaster; John Heilbron, Emeritus Professor of History at the University of California, Berkeley; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London.

This BBC podcast is supported by ads outside the UK. Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uk forward slash radio four. I hope you enjoy the programme. Hello, Pliny the Elder in his Historia Naturalis, tells a story of a legendary Greek shepherd called Magnase, who, while guiding his flock on Mount Ida,

suddenly found it hard to move his feet. The nails of his sandals held fast to the rock beneath them, and the iron tip of his crook was strangely attracted to the boulders all around. Magnets had stumbled across the lodestone or magnetite and discovered the phenomenon of magnetism. Plato was baffled by this strange force, as were Aristotle and Galen, despite being used in navigation first by the Chinese, supposedly suspended over the body of Muhammad,

and deployed in the pursuit of medical cures, apart from some 13th century scholastic studies, it wasn't until the late 16th century that any serious scientific attempt was made to explain the mystifying powers of the magnet. Who pioneered the study of magnetism, what theories did they construct from its curious abilities, and how has the power of the magnet

brought out of the realm of magic and into the service of science? And do we really know what it is even now? With me to discuss magnetism is Stephen Pumfrey, senior lecturer in the history of science at the University of Lancaster, John Heilbrun, Emeritus Professor of History at the University of California, Berkeley,

and Lisa Jardine, Professor of Renaissance Studies, of Queen Mary, London. Stephen Pumfrey, the fact that there was no satisfaction for one lump of eyeing attracting another or a magnet moving its position to point in one direction didn't stop people using them. Can you tell us when magnets were first used and what for? Well, as you said, the Chinese were the first

to discover this property of magnets pointing north, but it was really in Europe, around the time of the Crusades, that European navigators started to use magnets, needles in their ships. Had this come from the Chinese through the Ottoman? Yeah, yes. I mean, through those of trade routes. And it was, I think, as far as we understand, when the Crusaders sailed to the Livan

from the Port of Amalfi, it was there that they first encountered primitive compasses. And they used them in the medieval period, really there's a rough check on north, especially when it was cloudy. And as we all know, compasses do point roughly north. But it was really during the age of exploration when the Spanish and Portuguese led Europe

and exploration of uncharted territories that the compass came into its own. And all progress, really up until 1600, was made by these practical seamen rather than philosophical scientists. And the main point of the compass and the main help it gave was that you could navigate away from the shoreline.

That's right. With the age of exploration, navigation changed from knowing roughly where you were from the shoreline to sailing completely uncharted waters. And the Portuguese first began to discover, that the compass didn't actually point actually north, but deviated slightly. They sailed to the Orient. They found it sailed east.

And that rather screwed up the standard philosopher's theory that it somehow had some magical correspondence with the celestial pole. Because there seemed to be two poles, a north pole and a true pole. And also it varied. When you were in different parts of the globe, it varied. Well, that's right. And indeed when Columbus led the Spanish to America, as he later discovered, he was astonished to find that the compass pointed west.

and at this point people were really very confused as to how the magnetic property operated at all. But there was one saving virtue out of this disaster. And? Are you going to keep us all in suspense? We haven't got much time to cover this whole subject. Which was that if the compass perhaps pointed east, if you sail eastwards,

and west when you sailed westwards, could you perhaps use this difference in magnetic variation to solve the great pressing problem of navigation which was finding your longitude at sea? And up until the 16th century, navigators whose live deputies, depending on it, we're trying to solve this problem. There are two, three things to say about the compass.

First of all, this is a study in which practicality preceded theory quite emphatically and for a long time. It certainly ran ahead of theories. It's certainly run ahead of theories. And secondly, the compass is very important commercially, as you've indicated, but also politically how you could move around the world and conquer people. And also, theoretically, in a sense, religiously, in sense, how could you get across to these foreign places full of non-Christians and Christianize them? So we're talking about a very important instrument in many senses of the word.

but it was a man, an Englishman called Gilbert in 1600, who did the first major work on a massive book on magnets, de magneta, and that's taken also to be the first scientific treatise, perhaps on any subject. Can you tell us briefly what Gilbert did? What Gilbert did was to talk to the extremely experienced English navigators, who, because of the Spanish and Portuguese rule of the southern hemisphere, were forced to sail near the North Magnetic Pole where compasses went,

of haywire, really. So English navigators knew much more, even than Spanish and Portuguese, about it. He learned a lot from them. He's consulted what Shakespeare would have called the rude mechanicals when many natural philosophers would not have thought of having them, having very much the same. And he, de magnate is his extraordinary book. It's got an extraordinary thesis, which the earth is a giant magnet. It's got an extraordinary attitude for a renaissance natural philosopher, which is that because he thought that, he knew that Aristotle and Plato had know nothing about the earth as a magnet. He took the very radical view that really the ancients

had nothing to say to us and their whole philosophy was to be dismissed. Can I turn to John Harbin? Can you explain what Gilbert's theory was? We talked about 1600. He was the court physician to Queen Elizabeth I. Well Stephen said his notion has to do with the earth as

a magnet. In fact magnetism is the principal quality of the earth. It distinguishes it from everything else in the universe. There is lunar properties that cause the moon to stick together and jovian properties that cause Jupiter to stick together. And our particular form of accretion is magnetism. And in fact, the Earth's soul is magnet and the Earth's soul is more noble, in fact, than ours.

So was that a great discovery on Gilbert Spar? It may not be a discovery. Oh, the Earth was a magnet. No, in fact, one of these medieval persons to whom you have. eluded Petrus Paragrinus, who seems to have been a teacher of Roger Bacon's, had many of the same ideas as Bacon, and had, in fact, done some of the experiments that, for which Bacon would later, excuse me, for which Gilbert would later become famous, particularly modeling the Earth as a spherical loadstone.

So how far did Gilbert go with this first massive book? How far did he take us in the study of magnetism? Well, he brought together what had been known, very greatly amplified it, but perhaps the most important thing is that he showed how by a series of systematic experiments it would be possible to exclude what was suggested as properties of magnets, which such as killing it power by rubbing it with garlic, or that it would not perform. in the presence of a diamond or any such thing, or that a pocketful of magnets would give you eloquence. I tried that, incidentally, but I think you have to swallow them. I might hope so learned it, learning. So he got rid of a number of old and new wives' tales, and he showed how by systematic

exploration of this Terrellas, he called, this simulacrum of the earth, this lodestone made into a sphere, it would be possible to show. show how the compass worked. And its dip and declination, the variation of which Stephen has spoken, could all be observed on this tiny tarrella. And as Stephen said, as you indicated, he got a lot of his information from people down in the docks who'd come with their compasses from all over the world. He did, indeed, and he was something of a hobbyist. He would rush down to the docks to get the latest rock from here or there and run home and test its magnetism. and so forth.

How were his ideas received by his contemporaries, by Francis Bacon, for example? We all know about the great Francis Bacon. How has he thought of? Well, we do. I feel that I'm most shy in speaking about Francis Bacon in the presence of Lisa. Oh, go on. Get over it. I'll get over it. I'll get over it.

And say, if I suppose I can, if it were possible for Bacon to say of Gilbert what he did, not knowing anything about the subject, namely that he was a perfect. example of this idol of the cave in which one raises one's own hobbies or hobby horses to the level of philosophy building as he said

a philosophy out of the loadstone but Bacon had a what an ability to see not to see what was the most progressive in the science of his time what did you mean Aliz Jardin when he called

Bacon called Gubber being an example of the idol in the cave Well, it's interesting because Stephen's given us such a good account of Gilbert's idea of a unifying theory of the magnet, that the earth is a great magnet that you can account for all kinds of phenomena by regarding it as a self. John Howard also said that it had a soul. And that it has a soul, quite. Francis Bacon was deeply skeptical of grand theories. The idols of the cave are grand theories.

And he actually picks Gilbert out as an example of how a man who has very, very good practical knowledge, very good practice can get carried away and elevate what he's doing and what he knows about to the level of a grand theory in which, as it turns out, he was profoundly wrong. Gilbert was living in revolutionary times. I'm going to let that pass from a minute. Because you had the Copernican revolution going on. How did that affect the way Gilbert came to his conclusions?

I think, again, we're all deferring to each other. I think that the Copernican moment, if you like, in the middle of the 16th century is a moment when the power of the mind, the power of the human mind, to bring together observation and experiment and to make the great ideas fly, really, the movement of the planets, the attraction of the Earth, gravity as a possibility well before Newton.

that it is the moment, let's say 1543 for Copernicus and then 1600, between 1543 and 1600, when these thinkers who are practical men, interested in the commercial world, interested in experiment, how things work, get the courage and the mathematical knowledge to build that into great theory. Because Comenicus has observed, of course, that the earth and I think go around the sun. And Gilbert was saying, when that's because of magnetism. Well, because of an attractive... Yes, Gilbert makes it magnetism. Bacon says you couldn't be more wrong.

And the Copernican theory shows that there is some constant force that is pulling the planets towards the sun. There's also, for me, the intriguing notion at that time of what was called action at a distance, because magnetism was invisible and yet it had a force, it came off, it pulled the nails out of your shoes, and so on.

It was like, as they then thought, infection, which they didn't know about being carried, and love. There were two examples. as they brought along. How widespread was this notion of action at distance? And how did it affect the thought even of Gilbert himself? Action at a distance, we still are interested in.

They were hugely interested in, how sap is sucked up in plants, how people get the same idea, how people fall in love, and how bodies like. Why is it called action at a distance, Lisa? One or two listeners might want it really spelled out. Because whereas when I push this pen on the table, table, you can see the force acting on the pen and you understand that the pen moves because I push it. If the, if a planet moves around in the sky, you cannot see the force impinging

on the material body and you therefore are inclined to think in rather mystical and spiritual terms about what's happening. The magnet in French is called an eminion, which is related to a lover and there was a very strong sense that the kinds of emotional pressures that you can't see the force originating from but which affect other people like my making eye contact with you, that those are mysterious, that they are related to magnetism, related indeed to gravity, related to electricity. We're in a time of scientific, let's use that word all over, a revolution at that time, but we're also in a form of great religious absolutism

where everything had to be filtered through religion, every idea. How did the Gilbert in a Protestant country, nearly a fairly newly Protestant country in 1600, how did that filter through in religious thought, Stephen? Well, although Bacon didn't like Gilbert's big idea that it was a magnetic force that drove the earth around the sun, there were plenty of astronomers and philosophers who did. Kepler, in fact, made it the basis of his elliptical astronomy.

and it was when Galileo also started using Gilbert's ideas to buttress his idea of communion that the Catholic Church in particular became very interested. Interested in the sense of, let's be interested. Interested in the sense, I think, that the Catholic Church had this kind of body of highly trained theological and philosophical professionals, the Society of Jesus, the Jesuits, whose job it was to kind of take on potentially dangerous new ideas and neutralize them. And around the time when Galileo is making waves, you can almost, I think, here, the call coming out from their headquarters at the Roman College saying,

we need urgently a new Catholic, safe, Aristotelian theory of magnetism, but above all proves that the Earth doesn't move. And for 50 years after 1628, it's Jesuits more than anybody else who publish it, and they do, to their own satisfaction at least, prove that magnetism is probably the Earth, but it holds it still at the centre in Galileo and Gilbert are completely wrong. So it's highly theologically charged. John Hardman, what does Descartes out to the argument about magnetism? Well, he changes the entire basis of the discussion.

These souls, or let us call them rather, special qualities, there are things that are not further reducible. You cannot express them in terms of atoms or some sort of more primitive matter. So the world is full in the Aristotelian case with different sorts of things, irreducible things. And comes Descartes, and he says, that's nonsense. I'm going to get rid of all those various things that are supposed to be in the world and reduce the world to matter in motion, undifferentiated matter in motion.

Well, that's nicely said, but how do you do it with respect to something like magnetism, which has puzzled people for a good long time, and for which various explanations or forms of words have been used to remove this quality from the universe. And he has to do it by matter in motion. So what he imagines is that there are specially shaped little particles and that magnets and iron have very specially shaped little pores in them and that the little particles go through the pores

and finding the cells unable to penetrate further into the atmosphere because of their shapes, they come around back to the bottom of the magnet, and in the course of their motions accomplish magnetic attraction and repulsion. Now, I should say that Descartes' little particles that do these things are a product of the Cartesian Big Bang. They come from the very formation of the universe, so magnetism is radically important. important as being a consequence, a relic, if you will, of the Cartesian Big Bang.

But you see, he's got rid of the quality. That's the essential thing. He has reduced the world to a very uninteresting place without these special qualities. And, of course, that turns out to be a vain hope because of all the, magnetism, I think the reason people are so intrigued by magnetism is it never loses that sense, that there are occult qualities associated with the draw of the magnet, which will never be encompassed simply by matter in motion. How did Descartes' ideas fall down?

I mean, and they've been very clearly explained by John. Why did they not once explain to carefully and in the time he was such a towering figure? Why did they not have a greater acceptance? Well, no, I mean, actually they did. I mean, Descartes' ideas are sort of a mechanized universe which gets rid of the magic which lies behind magnetism did have a wide currency. I mean, they did change the face of scientific thinking.

The unfortunate thing is that there are some things that really don't work very well, explain this way, as John said. That's meant about magnetism. Yeah, I mean, and it's Newton, as it were, who shows that really you can't have a fluid explanation of magnetism. I'm reminded of a, there was some vain Italian philosopher who wrote to the Royal Society said that he had a theory of everything.

and the Secretary of the Royal Society wrote back and said, that's very good. What we'd like to know first, please, is your explanation of gravity, the spring of the air and magnetism. These were the things that mechanical philosophers just simply couldn't deal with. And Newton's success is coming up with a different way, which in a sense brings back the magic. Hold on. I want to get to Newton in a minute. I'm going to go through Halliday. Do you want to say something? I just wanted to say that we talked about the practicalities, the fact that this was, magnetism was a phenomenon that was discovered in practice and by seamen and by navigators. One of the reasons that Descartes's theory collapses is it doesn't work.

It's no use to you on a ship. The precision of the mechanical universe is a grand idea, but it doesn't work. And there has to be this interplay between the grand theory and the practice on the ground. But you have in these little particles and their trajectories, you have a perfect image of the iron filings that are scattered around magnets in which we all saw when we were children. And so it became a challenge to calculate just how those iron filings,

or if you prefer, the course of these little particles, worked out. So even though Newton came along, there were a lot of Cartesian's for many years who kept speculating about how this vertical trick could be played. We are running the practical and the theoretical together, and enter a man called Halley, who was an extraordinary man, wealthy, Newton's patron,

Got Newton, finance the publication of Principia and so on, an astronomer himself. But he, one way and another, went round the world with the Royal Navy to try to make a magnetic map of the world. Could you tell us about that, please? Halley is a magnificent example. It's he of the comet, isn't it? Halley of the comet.

it, Hallie, probably the most hands-on, successfully hands-on of the early members of the Royal Society. He was born in 1656. He was born in the middle of the English Revolution. He came back, sorry, he grew up in the returned monarchy, which was desperate for money. And therefore, the commerce and science go hand in hand in that period. Even as a young man under 20, he decided he would go to St. Helena in the middle of the, at the middle of nowhere as far as contemporary Europe thought, but the most southernmost point that England

owned in order to map the stars in order to help navigation to navigate south of the equator. Magnetism took his interest on that first voyage. He subsequently became a very proficient sea captain himself and then went off to try and explore in the 1680s and

90s the way in which the magnet refuses to behave, as Stephen explained so beautifully, the magnet refuses to behave as you move around the oceans. So that this variation, the way that the compass needle points away from geographical north towards somewhere else, the angle between them is called the angle of magnetic variation, Halley decided that it must be possible to map that. and indeed he took numerous, though we're not quite sure how many, measurements as he sailed on a very long voyage across the Atlantic Ocean, and he called in measurements from anybody else who was taking measurements. And he produced something called an exogenous?

Isogamous, isn't it? Mr. Hargey there, Stephen. Map. Now then, can you tell us about that and how good his exogenous map was? Well, he did produce this very wonderful map joining up points of similar variation. And driving it all was this still pressing problem of the longitude. I mean, Halley was certainly hoping that if you could map this accurate enough, you would be able to use magnetic variation to solve the longitude problem.

That is to tell the navigator where he was on the great circles of the globe. You knew how far you were north and south, but you could not map precisely. That's the longitude problem where you are is between east and west. And maybe you could just look at your compass needle and say, oh look, it's four and a half degrees. My map tells me that off the coast of Newfoundland, 20 miles away, it's four and a half degrees.

That's where I am. And that would have been fantastic. I mean, governments were prepared to pay millions of pounds in today's money for someone who could come up with that solution. And unfortunately, it doesn't work. I mean, it doesn't work because variation actually changes over time. Halley knew that. He had an elaborate theory of four poles of the earth

in which he hoped to predict the change, but that doesn't work. And indeed, scientists today, who rejoice the name of geomagnetohydionicists, have a very good model the interior workings of the earth. But in terms of being able to use that model to predict actual compass bearings on the surface,

we still can't do it. So the only way that would have succeeded would have been if Halle or someone like Halley had gone out every five years to remap it empirically and no government was prepared to pay for that. There's also the awkwardness, I believe, that the lines in question don't change much. The variation doesn't change much

as you go east-west in the latitudes of interest so it wouldn't have helped at all. It's not discriminating. Especially given the problems of using a compass at sea. Yes. John Halburn, Newton's name has entered and necessarily into any discussion of science around this time more than once. What did he, did he concern himself?

I know he did, but you answer the question. Did he concern himself with magnetism? And what did he find out? Yes, of course he can concern himself with magnetism as with all other things. But yes, his approach was quite interesting perhaps just because it differed so much from his approach to gravity.

He was interested in it as a form of attractions. He was interested in electricity. But in the case of magnetism, he did not do what he did in the case of gravity, which was to add up all the little forces between all the little particles of gravitating matter in the apple and the earth or the earth and the moon and so forth. But rather just took on the two magnets or magnet in a loadstone and asked what the force between. them was. And he got an answer which of course was very peculiar and dependent upon his experiment because the force between what? The nearest the poles and the or between the

nearest surfaces or whatever. And so he gave an expression for this force between them which was not, which people then were unable to reproduce. He did not take this approach of gravity, which is to go between little particles of magnetic fluid. That would have been the analogy, but rather a gross approximation using the bodies in question. And I'm sorry I did not say that very clearly, but the point here is that the essence for the mathematician and the exact experimenter of Newton's gravitational theory was just to be able to define a clear, distinct force and that was not possible for magnetism for a long time.

Why was it not possible? I mean gravity seems is still one of the people are still mulling over, ruminating over all they acknowledge in the greatness of Newton's contribution there. Why did magnetism seem some, he lost interest in it really, but why did it seem so much difficult? The magnet is a magnet we're talking about magnets, you know, as if we all

were quite sure what they are. A magnet is such an interesting object and very different from remote planets which you can reduce to point masses and calculate the mathematics of how they move. Every time you break a magnet it turns into two little magnets with the north and a

south pole and all the properties intact. You keep on breaking the magnet it keeps on reproducing itself with the poles closer and closer together. So messages are not coming from one thing but from two things. From two things and... Well with two magnets four things and that's getting very confusing. And it's just

extremely confusing on that scale. Also, it doesn't only attract, it repels and attract unlike poles. Well, so the like poles repel and the unlike poles attract. And it's really sad in a way that our own children can't do those experiments because magnets are so dangerous around computers. My home as a child was full of magnets and all these properties with iron filings and producing patterns of iron filings around the poles of the magnet. We all can actually see them in our mind's eye. Nowadays, they're not even done in schools. However, Newton, in a way, shows that Newton is an absolutely brilliant mathematician.

That is, he wants the large theory, the mathematicians, the equation that will capture simplified systems in a way that will produce results, which are helpful in everyday life, which is exactly what the theory of gravity does. But magnetism just didn't work like that. And he lost interest because he was a, I don't like Newton, but he was a very characteristic. He doesn't like Newton to think he's a genius. He was an unpleasant man, but a genius. We can live with that.

He was a tiresome man, and when he couldn't solve it, he discarded it. So he couldn't work this one out. Well, isn't that sensible? It's not sensible. It's not sensible. I think that's a very sensible thing to do. On the theory that you can't do everything for goodness sake, maybe you can. Maybe you can't. Despite the fact that he couldn't measure it, John, did he not declare, as it were, that he was sure it was an inverse cube?

I sometimes think he just wanted to kind of differentiate it. Inverse cube. He says from some rough experiments that I have done, I think it's something like the inverse cube. And then, as you say, Melvin, he's sort of moved away from the problem. And magnets are even worse than Lisa has described. Because, for example, they will lose their magnetism. And you put them in the fire, they lose their magnetism.

You put them on the shelf too long, they lose their magnetism. And worse yet, you can change the poles of the things. So gravity is a piece of cake in company. We're going to do a program on gravity. I'm not looking forward with that piece of cake. Quite as much as you seen. But let's move on to 1760. there's a French physicist, Charles Coulomb,

a devised an experiment that moved even further into magnetism. John Hallburn, can you tell us about that? Could you make that the 1780s and then I could do it? Well, in around 1716? No, no, I can't even have that. My God, not my area, really in spades, yeah. Well, here is the Newtonian experiment at last with respect to magnetism.

By the time Kulom, who was an engineer, came on the scene, it was possible to make very long, narrow, thin magnets. Think of essentially a magnetized steel wire. And that had well-localized poles. So now you get back into the point story, which and a geometry that looks like the geometry of the gravitational system. and what he did was to put up two of these magnets

facing one another and allow one to be mobile and the other fixed and to drive the mobile needle around and by measuring the deflection was able to calculate

that indeed a magnetic fluid analogous to ponderable matter could give rise to or did give rise to forces which depended upon the inverse square. And that he took to be confirmation of the Newtonian picture,

that it would be possible eventually to discuss all phenomena in terms of attractions and repulsions, because, you see, he got the law. He got something that was quite analogous to the gravitational theory, which Newton had not been able to do. As a mere observer, it's quite interesting that it's an engineer We've been talking from the beginning since the Chinese about the practicalities of this matter.

And Gilbert went and talked to say it doesn't sound so. It's an engineer who brings the two together. Yes, and through a special balance that he had invented, which a torsion balance, essentially a thread or a wire that bears the body on which you're going to do your experiments and which can be twisted. And the twist of the thread produces a force

which Kulom measured very carefully, and it was that twist, that force of torsion that he balanced against his force of magnetism. How successful, Zimbabomber was Kulom? How successful in spreading his ideas? People take that on and think it's been solved? Well, I think very much so. I mean, Kulom had done what Newton was unable to do with his engineering skill to show the inverse square law of magnetism. Kulon's perhaps most famous today for, I think, for showing that there was an inverse square law of the electric. point charge as well. We talk about Coulogs as a unit of electricity. So by the end of the 18th century, French scientists in particular look like they've got to the end of the Newtonian program. They're arriving at the grand unified theory. Everything in the universe, gravity, magnetism,

electricity, the lot can be explained in terms of simple mathematics of inverse square laws of forces. And whether or not Pierre Simone Laplace, who was the great collaborator of Coulomb, actually said this on it. And the idea is that you can get the magic, you can get God out of the universe. We can calculate and predict exactly how the universe goes. So Coulomb's work was very important. He didn't actually, I think, push it that far. He became a kind of great technocrat of the kind who ruled France ever since the 18th, the French Revolution, didn't, I think, pay much further part.

But his ideas go into this grand unifying thing, which is actually a bit of hubris, because they were about to find that they didn't understand these things as well as they thought. What about the culture of magnetism in the 18th century? Is it what was going on in a sort of funfares and drawings? drawing rooms? Well, the lure of the occult version of magnetism never went away. And so what you get, at the very moment when you're getting these grand theories, the unified theories of how gravity and magnetism are subject to the same law of inverse square law of attraction, and you get the, you get the fun fairs producing more and more elaborate versions of men with, usually men, with bundles of magnets.

making young ladies faint at the fun fair with erotic ideas that are generated from the bag of magnets. And of course, Mesmer is the past master of exploiting these ideas of magnets. You have to remember that all these scientific ideas get exploited one way or another. But again, the magnet is so deliciously handleable and its properties are so wonderfully curious that drawing in the idea of emotional attraction or curing someone almost in a Freudian, as Freud did,

by interaction of magnets rather than the talking cure. That is literally how magnets are being used in the 18th century. There's also a kind of religious experience in a way, isn't it? Because after all, if you take Newton seriously, magnetism, gravity, electricity are all signs of the divine power hidden in matter. So when you conjure up the magical powers of magnetism, you're experiencing the divine as well. That's a big hoots for someone.

So the spinous idea of the soul of magnets having a cell and Gilbert's idea of having a cell persist still. But it ended into old wife superstitions as well, didn't it? What about the superstition that if you put magnets under the marital bed, you discover that your wife, whether or not your wife was being unfaithful? Well, exactly. There's a connection with sex going through this, isn't there? Had to get sex in some way.

No, I didn't. I don't do that sort of thing, but I mean, it is. Lisa mentioned that the French word for magnet is amor, and Gilbert was so obsessed in the sense with this kind of sexual angle that he wanted to abolish the... the word attraction. He thought that was violent. That was like kind of rape. The word he used was cohesion. Magnets are two lovers coming together. Sex does run through this.

And remember, you know, we just have to think for a second, attractive. She's a very attractive woman. I am attracted to him. Those words, and I looked up their etymologies last night, the etymologies all run together. They come from magnets into the sphere of the discussion of

sex and emotion. John Halberin, would you care to be engaged in this rather lowering ring of the time. No, I've been fascinated by it, and I've, of course, think of Mesmer, whose little games often had an erotic character to them, the passing of one's hands over the magnetizer's hands, over the body of the ill to affect... Usually female.

Usually female. To affect a magnetic cure, to restore the balance of the animal magnetism and so on. Mezor, incidentally, who was a rather engaging character from time to time, and a great lover of music, was a sponsor of Mozart, who then repaid the debt by making a magnet a principal character in Cozy Fantutee, right? who are, this quack, well, I can't remember the story exactly, but this quack made who passes a magnet over the bodies of the suitors who are supposed to have taken poison, who then immediately quake and shake in the approved manner of the mesmeric crisis. But in this sort of cultural, subcultural stratum,

it's competing with electricity with people like Galvani, who puts a charge through frogs like the frogs dead frog, twitches, and then, we lead to Frankenstein. Our life is just a series of pulses which can be put in from outside. So it's an interesting game. It's coming from magic, but it's verging on science as well, isn't it? That's right.

I mean, it's easy to dismiss Mesmer as a charlatan or a dreamer, and many at the time as now did. But just at the time when Mesmer's reputation looked like it was going down the pan, the Academy of Science has set up a commission with Franklin and Lavoisier to find out, whether there was animal magnetism, mesmeric fluid, just at the time that that's looking dodgy, Galvani comes up in, as you say, in Italy and sort of puts electricity through a frog

and electricity looks like it's a kind of fluid of life. So why should there not be a magnetic fluid of life as well? And this does have serious implications because are we getting to the point now, as you say, with some frankest, one of the themes of frankness, is have scientists, as it were, tamed, or are they in danger of thinking that they can, tame the life principle, the animate principle,

down to a series of physical fluids. But let's go another way from Galvani, too, and remember that Volta comes out of the story. From Volta comes the electric battery, and from the electric battery come various things to which you, I'm sure, will lead us in good time. There isn't much time, but we're going to get to Faraday. That's what you're talking about.

Let's get to Faraday now, because there's right. What did Faraday contribute? Do you want to kick off, John? Well, I think we ought to back up one step, if you will, before we get to Faraday, which to introduce Hans Christian Ersted, who succeeded in a project in which many people had been interested from the 18th century on, which was to show some connection between electricity and magnetism. There were many indications that there was a connection, one of the most curious of which was that iron, Rod's fire tongs struck by lightning were often magnetized.

So Erstead and many others, imbued with the notion of the interconnection of all things, sought to show that there was some way in which electricity could produce magnetism or vice. First, and he succeeded in 1820 by showing that a current carrying wire could produce a magnetic force, which set up, of course, a quest for the opposite effect, how magnetism somehow could create an electric current. Faraday was one of the first to take up the ersted effect and then interrupted his researchers for various other things, returned to them in 1831,

and then found that a combination of magnetism and motion and an electric, rather a current, excuse me, a circuit, a wire could produce. electricity, which enabled one to say that these powers were interconvertible. Amazing to think we're in a quite small studio here. It's amazing that it did it in a room not much bigger than this, just around the corner, isn't it? So what did induction or electromagnetism do, Stephen, in the story of magnetism? Where did it take the story? Well, I mean, the fact that you can use the word, the electromagnetism shows that we have now

entered a new era, which we're still in, of electricity and magnetism. as different parts of the same field of force. Parada introduces the idea of a field of force, which is new as well. And in a sense, I mean, I'm not a great sort of believer in cyclical theories of history, but I think it has come full circle. Magnetism started off in the ancient world,

along with the electron, amber, as two very unusual, strange magical properties, which were the properties of a strange mineral called lodestone or a strange substance called amber. and they're linked together in the kind of panoply of magical cures. And then with Gilbert, Gilbert tries very hard to separate them, they remain separated. But yet, after all, at the end of our story,

they've come back to be two sides of the same coin with the big difference, that they're now no longer unique magical properties of strange minerals, but they're the fundamental forces of the entire universe. Fine, is there a sense in which magnetism is still mysterious, is still not fully understood? Yeah, every sense. almost every sense. People still want to, science

still has not cracked magnetism and people still want magnetism somehow to have a soul. What do you mean ever since then? Well, there are many ways in which one can look at this question to example after the discovery of Ersted

the French busy themselves getting rid of magnetism altogether, right? It was to be replaced by electricity in motion. Faraday, having shown that the complete indecundated convertibility of the two, then busied himself getting rid of both electricity and magnetism and putting the stresses and strains or the forces involved in some sort of medium between the bodies that were interacting.

Bevan? I'm not obviously a kind of modern scientist. My understanding is that the Holy Grail for sort of modern scientists in science is to find the single magnetic pole, the magnetic monopole. This would be the kind of the fundamental unit of magnetism that would give them the some explanation, and they just haven't got it yet. It's like a lot of areas in this, isn't it? We're finishing now, that finding the single thing is the final problem.

I wonder whether it's the beginning of the next lots of problems. But it may not exist. That came in very well, creepily. Thank you. Well, I enjoyed that a lot. Lisa Jardin, John Heilberg, and Susan Pumperin. Thank you very much. Next week, we'll be talking about two young kings, great princes in their time of Renaissance Europe,

Henry the 8th and Francis I, and how they met in. imitation of war on the field of the cloth of gold. Thank you for listening. We hope you've enjoyed this Radio 4 podcast. You can find hundreds of other programmes about history, science and philosophy at BBC.com. UK forward slash radio 4.