The Magnetic Mystery

This BBC podcast is supported by ads outside the UK.

Start your journey toward the perfect engagement ring with Yadav, family owned and operated since 1983.

We'll pair you with a dedicated expert for a personalized one-on-one experience.

You'll explore our curated selection of diamonds and gemstones while learning key characteristics to help you make a confident, informed decision.

Choose from our signature styles or opt for a fully custom design crafted around you.

Visit yadavjewelry.com and book your appointment today at our new Union Square showroom and mention podcast for an exclusive discount.

Ready to buy a car, a home, or just want to take control of your money?

Your FICO score matters and 90% of top lenders use it to make decisions.

Check your FICO score for free today without hurting your credit score.

Visit myfico.com slash free or download the MyFICO app today.

MyFICO gives you the score lenders use most, plus credit reports and real-time alerts to help keep you on top of your credit.

Visit myfico.com slash free and take the mystery out of your FICO score.

BBC Sounds, Music, Radio, Podcasts.

Hello, Curios.

Now, this is one of those episodes where I'm so ignorant of the whole subject and it's quantum physics that I can only really contribute

mid-naughties music references.

You know what though?

I seem to remember someone said once that if you understand quantum physics, then you're lying.

There's a quote like that.

I can't remember.

It was Richard Feynman who probably did understand quantum physics.

Well, certainly more than me.

What's the quote?

It is.

Anyone who claims they understand quantum physics doesn't understand quantum physics.

Something like that.

Someone will write in.

Surely.

Turn it into a jingle.

Surely.

Anyway.

They're not going to be any more enlightened after the end of this program, that's for sure.

Here we go.

Today's Curious Case concerns a mysterious phenomenon, a universal force that surrounds us, penetrates us, and binds the galaxy together.

Are you talking about what gives the Jedi their power?

Which one's a Jedi again?

I always get confused between them and hobbits.

No, no, Adam, we're not.

We're talking about magnets.

Yeah, I can't pretend I'm not disappointed.

Well, I'd mostly do it to annoy you.

That is why I'm disappointed.

Listener Lucas sent in the question to curiouscases at bbc.co.uk.

In my high school physics classes, I learned all about the properties of magnets, but I am yet to understand what a magnetic field actually is.

In my mind, it still feels a bit like a magical aura.

And another question here, magnets, how do they work?

And I don't want to talk to scientists.

You're lying and getting me annoyed.

Who was that one from?

That one came from the American Horacor rap duo The Insane Clown Posse in their 2009 classic Miracles.

They didn't send that through, they did they?

No, they did not.

No, you just wanted to talk about Clown Posse on radio 4, didn't you?

I did.

Do you see why I need to annoy you?

I do.

Okay, good.

Right, well, we are going to talk to some scientists, which I'm sure to your disappointment, Clown Posse.

Our expert magnet magicians are Dr.

Felix Flicker, who's a theoretical physicist at Cardiff University.

And Dr.

Anna Porschaisky, material scientist and engineer and author of Handmade.

Now, Felix, I know that you wrote a book that was called The Magic of Matter.

So I feel like you're a good person to ask about this question.

I quite like that Insane Clown Posse song, I have to admit.

I did.

I do.

Hang on.

You're supposed to be siding with me.

Hannah didn't know what it was.

I sneaked these things into the script without her noticing and she did not know who the Insane Clown Posse was.

I wanted to quote that exact quote you said, which I think was a little bit more explicit in the rap core version.

I did sanitize it, but yes,

how do magnets work?

Scientists are lying to us all.

Are you?

I mean, it's certainly pretty magical how they work.

I agree with them on that, certainly.

I mean, there's not many things in the world where you get two objects and you twizzle one over here and the other one over there twizzles, right?

That is kind of magical in any sense that you want to use that word.

What actually is a magnetic field?

So the idea of a field originally was because people like Newton didn't want to think that there was action at a distance, right?

So you twizzle one magnet, the other one moves and it's some distance away.

And we wanted this mechanistic view of the universe where things act locally.

So if a force is being exerted, it happens, something is pressing into something else.

So magnets seem to to go against this idea.

And so the idea of a field is that you twizzle this magnet, and what really happens is it changes a magnetic field, and the field spreads out throughout space, and so it's really acting locally.

The field twizzles the other magnet.

But then you can see it.

I mean, we've all done that experiment where you get iron filings and you pop a magnet, and then you can sort of see the shape of the field.

But you're saying the field is a bit of a fudge.

It's not really...

No, it is how we think about the magnetic fields and other things these days.

But historically, it was to avoid this idea of action at a distance, which because that was just seen to be too magical.

But what you're doing, in a sense, is you're just sort of pushing the mystery further back.

So it's not with the magnet anymore, it's with this sort of strange thing that permeates the ether.

Right, exactly.

And we do understand these things, you know, the modern understanding of the world is by what's called quantum field theory, and it gets rather complicated.

But essentially, we say that everything is made up of fields, even when we say there are particles.

Those are excitations of quantum fields.

We're going to get to that in due course, because this is going to be a very good question.

This is one of those subjects where I really struggle to contribute anything meaningful at all.

But Anna, perhaps you can tell us a little about the background, the history of magnets.

When did we first realize that magnetism was a thing?

We first realised that magnetism was a thing when we started looking at stones and how they were affected by the environment.

That sounds a bit weird.

One of the first stones that we realized was magnetic was a lodestone.

And this was a rock made of ferrite, which is a metal oxide, iron oxide, and iron of course is magnetic.

And this was a material that would move direction depending on the Earth's magnetic field.

Now, back then, we didn't know that the Earth was round, we didn't know that the Earth had a magnetic field.

All we could see was that these rocks were changing direction.

And so these lodestones were carried on board ships as they were going off and exploring the seas, and it was a way for them to be able to know which direction they were going in.

How long ago are we talking about here?

I mean, the earliest extant reference to lodestones is in an ancient Chinese text called The Book of the Devil Valley Master,

which is pretty cool, isn't it?

Yeah, that's very cool.

Hang on, this is all adding to Adam's idea of this big sort of thing.

Mysterious and magical.

The word itself, magnet, do we know where that comes from?

I don't think I do.

I do, because I looked it up on that.

That would be

where it comes from ancient Greece.

Magnesia, a place, the stone of magnesia.

Wikipedia, extremely helpful.

Is that to do with lodestones then?

The stone of magnesia?

Yeah.

These lodestones, where are they found all over the world then?

Do we know what is inside them?

Yes, we know what they're made of,

but we don't know why they're magnetised.

So if you get something that can be magnetic, like a lump of iron,

when you formed it, it may not naturally be magnetic.

In fact, it probably wouldn't.

You would have to train it.

Probably at school, you remember taking something like a needle and you stroke a magnet along it, and that causes it to become magnetic.

So lodestones, we know how they're able to to become magnetised but we don't know why they're magnetized in the first place.

So some of the evidence, like it's believed that it has to do with lightning, which is also pretty magical I think.

And the reason for thinking this is that we find that lodestones are only kind of close to the surface of the earth.

If you go much deeper you don't find lodestones in the crust of the earth.

So it seems that probably it's within a sort of depth that lightning could have struck.

So lightning's inherently electrical but also electricity and magnetism have this kind of deep connection and it seems to be that's probably something to do with it but we don't have a good reason.

So is that the idea then that just on the surface of the earth over billions of years

lightning will have struck in enough places enough times that any stones that are predisposed to become magnetic will have done so?

Yeah that's a good way to think of it actually.

Okay so Felix you mentioned that connection between electricity and magnetism.

Now Anna, as an engineer, magnets are everywhere in our everyday lives, everywhere.

Tell us some of the other practical applications for magnets.

Yeah, so magnets are, as you say, everywhere in our everyday lives.

A really good example is if you take a mobile phone, there are various places in a phone where we can find electromagnets.

So an electromagnet is just a coil of wire, a coil of copper wire.

Copper is not a magnetic material, but when you flow electrons through it, when you flow electricity through it, that coil of wire becomes magnetic.

It has a magnetic field in the same way that a piece of iron, if it's magnetised, has a magnetic field.

So how our phones pick up our voices and how they play sounds back are kind of two different ways of using an electromagnet.

So a very simple speaker in a phone has a coil of wire and a magnet and when you pulse electric signals through that coil of wire, your sound signal if you like what you're doing is you're kind of vibrating those electrons inside that material and those vibrating electrons cause a kind of vibrating magnetic field.

That vibrating magnetic field can then physically vibrate a magnet, which is on a little diaphragm, and that vibrating diaphragm vibrates the air around it, which is what we hear in our ears as sound.

So it's the trick, ultimately, to get from electricity to movement that is being used there.

Exactly right.

I remember this from GCSE Physics, the left-hand rule.

Yes, Fleming's left-hand rule.

Fleming's left-hand rule.

And I can't remember what...

You point your fingers in different directions in your thumb, and there are three things on it, and I can't remember what any any of them are.

Yeah, exactly.

So, if you do a thumbs up, a point in first finger, and then a kind of middle finger that's pointing outwards.

So, your thumb is the force, the movement.

Your forefinger is field.

Yes.

So, that's the direction from north to south of the magnetic field.

And your second

finger is current.

This is the worst magic of all time.

Yeah.

GCST students around the country are thinking, yes, I remember this.

But this is the main thing that I remember from the left-hand roll is people sitting in exams.

Exactly.

Just trying to rotate this thing pointing it to the ceiling.

Which direction the movement is going to go if you pass a current in one direction and the magnetic field is another direction.

See, I did actually pass GCSE physics.

There are some more exotic examples of the use of magnets in, well, perhaps not everyday life, but in this country, but in certain countries.

Maglev trains.

I mean, they're just incredible, aren't they?

So cool.

Yeah, from an engineering perspective, so, so cool.

So there's a few things that the magnets are able to do with these trains.

The first is levitate them.

So, the strength of the magnetic field in the magnetic track on the magnetic train means that it is levitated above the tracks.

That means you've got zero friction from the tracks, which means that your trains can go extremely fast.

So, that's the first thing.

The second thing they can do is to keep the trains on track, because if you imagine levitating something, if you were to go around a corner, you could imagine that it might quite easily kind of fling off the track.

So, it keeps the trains on track as well.

But the third thing it does is actually push it along, it causes that force forward.

And that's because of the north and south poles on the trains themselves.

So the train carriages themselves are magnets.

And you have north on one corner and south on another.

And the way that the magnetic field in the track pushes it forward, it's the magnetic push between those two things that makes it go really fast.

So some countries do have maglev trains.

Why aren't all trains magnetically levitating?

I think because it's extraordinarily expensive to run it.

And at least in the UK, we have quite a big Victorian rail network as it is.

So we've got to update our stuff.

Doesn't that mean that if you get on one of those trains, you've got to be careful about if you've got metal on you?

I would expect they would make some sort of Faraday cage within the train itself so that the people on board aren't experiencing the magnetic field.

Have you got a favourite, Felix?

Have you got a favourite everyday use of magnets?

Not that maglev trains are particularly everyday if

you live in Britain.

Well, doing cheap magic tricks, I suppose.

Is that a good idea?

Sure, I mean, if you're doing that every day, then I think it counts.

You mentioned I'm a theoretical physicist, not an inherently practical one.

So you're also not helping with the whole magnets are magic idea here.

If magic tricks is your everyday occurrence, then sure, why not?

And I notice, by the way, that you've brought something with you.

Yeah, I do.

I have a little magic trick just here.

Let me get it out of its little box.

So I went to St Andrews in Scotland.

I was visiting the university there about 10 years ago.

And I went to an office that the PhD students were in.

And we were talking about physics stuff.

And I spotted in the corner of the room, I could see a crystal levitating in the air.

And no one was mentioning this.

It was just sat there in the air.

And I thought, okay, how does that work?

It seems to be magic, so probably magnets are involved, right?

And what I saw was this crystal levitating

with a clear air gap underneath it, with what looked like some other magnets beneath beneath it.

So that seems pretty magical.

But actually,

when you studied magnetism at university, you learned that this is actually even more magical because there's what's called Earnshaw's theorem that says that it's impossible to statically levitate one magnet above another one.

So you can levitate stuff with magnetism, but it has to be moving, as it is with the maglev trains.

And I asked the PhD students, and I said, okay, is it maybe slowly turning?

And that's what's happening.

And they said, well, they didn't know, actually.

But they said it had been there for months.

and they'd sort of forgotten about it that's why no one thought to mention it they said it's been there for months if it's turning not very good researchers if they were not innately curious about their own environment but anyway carry on they they said it had been there for months so it but if it's turning you know you'd assume that the air resistance would have caused it to stop so something weirder was going on uh so i've brought for you today this this thing I saw in St.

Andrews.

I eventually found what was going on with it.

So these are neodymium magnets.

So here is the crystal.

It doesn't look much like a crystal, but I can assure you it is.

It's a teeny tiny square.

Yeah, it's a little black square, this thing.

Okay, so if I place it above here, it will levitate.

You see that?

And you can see that it's levitating because it's.

This is the

little tiny black square crystal has been placed on top of a very strong magnet and it's floating around.

Am I allowed to touch it?

You certainly are.

Yeah,

it slipped away.

It maybe doesn't want to be touched.

So this is like a, this is sort of, oh gosh, like a, I mean, in many ways, a really mini, mini, mini version of the maglev train that we're talking about.

It's so satisfying how smoothly it floats on top.

And yet you said this was impossible.

Yeah, so

you see, I was under a kind of assumption that I thought, oh, I've done physics at university, I know about magnets, and I thought, but Earnshaw's theorem says this is impossible.

So it turns out, Earnshaw's theorem says that you can't statically levitate ferromagnets.

Now, those are the ones we usually think of when we study magnets.

Iron.

Iron, for example.

But the thing that's levitating there is an example of what's called a diamagnet.

So it's not magnetic by itself, but when you put it in a magnetic field, it becomes magnetic so as to oppose the field.

And actually everything in existence is diamagnetic to some extent, but most stuff is so weakly diamagnetic you would basically never detect it.

And that thing is the strongest known diamagnet.

Oh, that's good.

I like that a lot.

The thing that I was thinking about when I'm looking at this is

if you had a big enough version of this, could you stand on it?

Like, does the physics say that you could levitate a human?

Yes, you need a very large magnetic field gradient.

So it's not just the field, it's the change in the field as you move through space.

But it's possible.

A sufficiently large field gradient would levitate.

Because, Adam, I don't know if you've seen this paper, but some people have levitated a frog in the past.

I mean, yeah.

Why?

Why is the question?

Why not?

Is the answer.

Quite right.

So, just getting a

lovely frog suspended in a dye magnetic field.

Now,

there's a paper about this and it has a wonderful discussion about how could you escape, if you weren't just using this as some sort of magic trick, but instead as some sort of

way to contain a prisoner, like a frog prisoner, how could the frog escape that magnetic field?

And essentially what it says here is that when you are levitating, you are trapped in an energy minimum right so it's very difficult to get out

and yet these authors of this paper have worked out that it would be possible to escape if the frog did a swimming motion

but the oscillations are going to be so tiny that it needs to do 10 to the five swimming motions

and it needs to be absolutely perfect to get perfect swimming strokes because otherwise the frog could be suspended there in the energy minimum for up to 30 minutes

Which you wouldn't really, I mean, I don't know whether the frog likes that or not.

I think we should reconsider our approach to prisons.

That's uh

to have levitating swimming-based prisons.

Mice are the biggest thing that have been levitated.

Mice are living things.

My understanding is they levitated mice in the end because they want to simulate the effects of zero gravity without having to use the expense and energy to send stuff to space.

So they can see what happens when things live in zero gravity, just in a lab setting.

Oh, that's interesting.

So if you could get this up to the size of a human, then,

you know, you don't need the International Space Station anymore.

You would never need that ever again.

Yeah, we'd all just sit in a pod on Earth.

But so far it's just frogs and mice, so of limited use.

Now, there are lots more exciting possibilities with magnets, not just levitating frogs, mice, motors, smartphones, trains.

We called up the UK Magnetic Society.

Yes, there is a UK Magnetic Society.

Matthew Swallow is the vice chair and technical product manager for Bunting Magnetics.

This is a man who is really into magnets.

He wanted to talk about why magnets are so useful on roller coasters.

So if you move a conductive material like aluminium in the presence of a magnetic field, what are called eddy currents are generated.

And those eddy currents generate a magnetic field.

And the generated magnetic field is opposite to the permanent magnetic field.

So as an aluminium fin moves between two magnets either side of it, a braking force is generated.

And it's fantastic for roller coasters because it's non-contact, which means it'll never wear out.

There's no brake pads.

If the entire power to the park should fail, it's okay because it's all done without any power at all.

So it will always stop.

And it's really quite speed dependent.

So the faster you're going, the harder you brake, the slower you're going, the slower you brake.

So it's never going to be a sudden stop.

Let me make sure I understand what is going on there then.

Is it that you have

just, it's the track that applies the brakes rather than the roller coaster, Anna?

Yeah, exactly right.

It's the roller coaster's interaction with...

the magnetic field in the tracks that's causing it.

And you'll experience this force.

If you've ever tried to put two south poles of two bar magnets together, you will feel that kind of resistance.

And that resistance is the same sort of resisting magnetic force that the roller coaster is experiencing as it's traveling through.

So the eddy currents that we can imagine are a bit like an eddy current in water would just be like a little sort of spiral of water.

It's kind of a similar thing, but like a spiral of electrons inside the material.

You can think of it a bit like that.

So with an eddy current in a piece of aluminium, what's happening is small areas of magnetic field sort of appearing.

And the eddy currents form little mini south poles, if you like, in this analogy.

So we have these south poles that are in the roller coaster.

And then when they pass through the magnetic field that is on the brakes in the track,

you basically get these two, if you like, south poles sort of interacting and causing that resistance force.

And that is what slows the roller coaster down.

So at the end of the track, once you've gone down the hill, there'll be a section of the track which is lined with magnets on either side and that's essentially the brakes.

Exactly.

That's quite a useful thing, being able to create what's essentially sort of electron turbulence inside a material.

Yeah, very much so.

And we use it in lots of different areas.

My favourite, I'm very passionate about recycling.

And in big, big recycling plants, they use what are called eddy current separators.

So you can imagine if you've got a big pile of recycling, loads of mixed materials, your aim is to separate all those different materials so that you can go off and recycle them.

You can imagine doing that with a magnet to get all of the magnetic material out, but what do you do with the rest of it that's not magnetic?

So to separate out materials like aluminium that aren't magnetic, they use what's called an eddy current separator.

So they're able to have a sort of temporary attraction of the aluminium to this separator and then take it off for recycling.

Which is the connection between electricity and magnetism because aluminium is not a magnetic material.

It's only magnetic because you put a current through it.

Exactly right.

That's very clever.

But why though?

Why are electricity and magnetism so closely related?

Electricity and magnetism are inherently linked because of what materials are made out of at their very, very tiniest scale.

So we've got a positively charged nucleus and a cloud of negatively charged electrons around those in atoms of which all matter is made.

So we've got differently charged sort of subatomic particles there.

And what happens with magnetism is that within those materials, those electrons aren't randomly distributed.

They're not behaving randomly inside.

So they have what is called electron spin, and this is where the quantum mechanics comes into it.

So an electron spin, you can imagine it a bit like a sphere that is spinning round, a bit like how the Earth spins on an axis, right?

You can imagine it like that.

So it can spin one of two ways, right?

And those different spins result in magnetic forces because of how a charged particle is moving.

Remember how I talked earlier about how electromagnetics work?

So you have charged electrons flowing through a thing, which is what causes magnetism.

Those movements happen at very, very tiny scales within materials as well, even as the electrons aren't being made to flow like electricity.

And it's the spins of these tiny electrons inside these materials that is what can cause magnetism.

But okay, then, Felix.

Why does that happen in some materials and not others?

And I guess maybe what I just mean is to get back to your insane cloud posse: is

how do magnets even work?

What are magnets?

What are they?

So it basically, exactly as Anna said,

it depends on how the electrons are arranged in atoms.

And if an atom has a full shell of electrons, there's none of them are unpaired, then it would be typically a dire magnet.

So it would oppose, you apply, it's not magnetic, you apply a magnetic field to it, and the electrons that are there will,

you can think of it as them changing their behavior so as to oppose the magnetic field.

So they oppose the field that's being applied to them.

Or in some cases,

the magnetic fields of individual atoms all try to line up together spontaneously.

And that's the case with like iron and so on.

So within a domain in iron, as it's called, all the magnetic fields are lining up spontaneously.

So all I heard then was magic.

Essentially, yeah, to boil it down to a word

that the insane clown posse would agree with, it is magic.

But that's not good enough for me.

I will not stand for it.

And you're a quantum physicist and I want more.

Tell me about what's going on at the quantum level that means that magnets are even a thing.

Okay.

There's another theorem, the Bohr von Leuven theorem.

Bohr-von Leuven theorem says that magnetism just shouldn't exist.

Full stop.

And it's a really simple, in terms of theoretical physics, argument that according to all the things that were known at the time, magnets just shouldn't be able to exist.

So in that sense, I think it's legitimate to say they're pretty magical.

Now, the answer as to how they really exist is that what was known until that time was what we now call classical physics.

Really, everything leading up to Einstein's work in 1905.

And so to explain magnets, you need quantum mechanics.

And ultimately, you need special relativity as well.

So two of the things he came up with in 1905.

And so the Bohr-von-Leeufen theorem says that using classical physics, magnets shouldn't exist.

And therefore, since they do exist, we need quantum mechanics.

Is this because, like you said right at the beginning of the show, that if you twiddle one magnet over here, another one will twiddle at a distance.

You've got forces that are acting at a distance.

Is that part of it, that in classical mechanics, that just doesn't really work?

There's an element of that to it.

Okay, there's a couple of reasons why we need quantum mechanics.

If you take two magnets, bar magnets, you know, with north-south each, and you put them down next to each other, they'll try to point north pointing towards south, right?

They try to point in opposite directions.

Yet, when iron becomes a magnet, I said that that on the atomic scale the magnetic fields want to line up, so they want to point in the same direction.

So that seems to contradict our everyday experience of what magnets actually do.

So that already requires quantum mechanics to explain it.

And the answer uses something called the Paoli exclusion principle, which is a famous result in quantum mechanics.

And the end result of this is that if you take just two electrons, both of those have their own magnetic field,

and you put them next to each other,

If their magnetic fields point in opposite directions,

that means that the two electrons are able to exist at the same point in space, which is a very weird quantum mechanical fact, but it's a fact.

Now, when they do exist at the same point in space, they still repel each other, because they're still both negatively charged.

So the energy for them to do that is quite high.

If their magnetic fields or their spins point in the same direction as each other, then they're unable to exist at the same point in space because of the Pauli exclusion principle.

And therefore, they don't live at the same point where they have this very large repulsion, so they lose a bit of energy by doing that.

And since they lower their energy by pointing, having the spins point in the same direction, you can then get magnets, after all.

Now,

I sort of followed that with my very superficial understanding of quantum physics.

I mean, that's being quite generous to myself there.

But I've got a...

a sort of more basic question than this.

If there is this force between, that is transferred between two objects, is it not reasonable to suggest that there is something carrying that force?

Is there such a thing?

What is happening in the field?

What is the force carrying particle then?

Ah, okay.

Our modern way of thinking about this again goes to what we call quantum field theory and specifically quantum electrodynamics.

Am I going to regret asking that question?

So it says that really it's an electromagnetic field.

Remember, electricity and magnetism are inherently linked.

And it says that that force field that exerts the force from one magnet on the other, it is carried by particles.

And those particles are the particles of the electromagnetic field, and those are particles of light.

So, basically, the short answer is: light conveys electromagnetism.

Okay, it's look, I'm sorry, lightning causes earth magnets.

Light is at the heart of how magnets work.

I mean, there is.

Look, you've won me rounds.

Magic.

You've won me round.

It's obviously magic.

Well, listen, thank you to our two guests who've absolutely proved that magnets are made of magic: Dr.

Felix Flicker and Dr.

Anna Pruszaiski.

So, Dr.

Rutford, when it comes to the case of the magic magnets, can we say case solved?

Well, kind of, Professor Fry, you can't explain magnets with classical physics, though.

And there are physicists who have questioned whether they should exist at all.

And yet they do.

They are everywhere.

From the microphones and speakers in our phones to the brakes on roller coasters.

And the ways that we separate recycling.

But when it comes to the explanation of how magnets actually work, they're somewhere between quantum physics and magic.

There is one quite interesting use of magnets that we didn't talk about in that program, you know, which is in MRI scanners.

Have you ever had one?

I have.

I've had two in fact and weirdly I had one given to me by Sarah Jane Blakemore.

Did you?

Yeah.

I had one given to me by Sophia Scott.

Did you?

I did.

Very good.

So it's like a little club, isn't it?

Yeah.

Who's been MRI scanned by UCL neuroscientists?

Hands up.

It's both of us.

It's both of us.

Okay, so the first thing that's worth saying is the strength of those magnets is phenomenal.

Well, I know that because I was about 26 when I had my MRI scan.

By Sarah Jane Blakemore.

By Sarah Jane Blakemore.

And it was the only time.

in my adult life since I was 18 that I had to remove my belly button piercing.

Have you got a belly button piercing?

Yep.

Still?

Yep.

This is...

How long have I known you for?

21 series.

I don't know whether

I'm pleased or annoyed that I didn't know this before.

Tell the Sophie Scott scanning story, why don't you?

You go into the room holding a penny and, well, you're not actually allowed to, but Sophie Scott said it was okay.

And you can feel the pull.

from the magnetic field of the of the scanner on the coin in your hand.

It's sort of, it's kind of dragging you forwards.

And there have been some unfortunate people who've sort of brought in, you know, ah, this patient's here.

I want to sit with them and comfort them.

Brought in a metal chair.

Immediately it sucked onto the side of the machine.

I mean, it's not ideal.

It's not ideal.

Now, the reason why MRIs use magnets is because it allows them to detect which parts of your brain are using more oxygen than others.

A tiny, tiny, tiny, tiny differences in the spin of

the particles that are inside your head.

But magnets are not only used in MRI scanners to

work out stuff that's going on inside your head, because there is also something called TMS, as Sophie Scott explains.

So TMS is transcranial magnetic stimulation and it's made possible by the development of coils which you could pass a large electrical current through and if you hold it over somebody's head it means that the magnetic field goes into their head.

That causes neurons just below where you've put the coil to all discharge all at once and that can suppress activity so it can stop things from happening depending on where you are in the brain or it can make things happen.

Well the first time I had it I do remember thinking you know this

my brain's pretty useful for doing all sorts of things like stopping me from I don't know weeing everywhere or swearing or all the other things that people don't do.

I hope they don't get that bit of the brain.

I thought I would need to turn that off briefly.

I think we need that.

But it is, because it's very focal, it's incredibly precise.

I mean, as I say, if they go along the bit of the motor strip that controls your hand, which is called the hand knob,

you get individual movements of fingers.

It's incredibly precise.

But it's also, if you go over the brain areas that are controlling speech production, which are just down in front of your, sort of in front of your ear on the left side of your brain,

you can completely stop somebody's ability to talk by using TMS over those areas.

It's a bit alarming.

I've actually done a TMS.

I've had one and you sort of wave it around.

It looks like a little hairbrush.

It's got a little ring at the top and you wave it around your head and it does make you,

well,

just you're suddenly speaking and then you go,

yeah, is it bad for you when that happens?

No.

No, not really.

But when you take it away, does it come back?

Yes.

It's incredibly temporary as well.

So it's a little bit like those classical videos of open brain surgery where because there's no actual nerve endings in the brain.

So once you've you've taken away the skin and the skull you can get electrodes and put them in parts of the brain and change people's musculature get them to move their hands in particular ways get people to move their hands yeah you can get them wait so you can do that with a magnet

that's it's exactly the same same idea you're just basically creating a tiny electrical stimulus in a very specific part of the brain, which means that they lose control of whatever that is temporarily.

Okay, wait.

I've just thought of a potential court case in future.

Because what if, right, what if someone created a helmet that had one of these magnets in it and put it on someone's head and then made them hold a gun and then from remotely set it so that they pulled a trigger?

Who's responsible?

Yeah, you are.

And because that's how the law works.

You designing the helmet, you pulling the trigger.

It's definitely you.

Hold on, there's a video here, though.

Hold on, there's a video of someone disrupting this speech, which is what you were describing.

Advert.

Hold on.

It looks a a bit like a pair of opera glasses that he's slightly thicker, which have clearly got these coils inside them.

And he's holding up to his forehead, just above his eye, left eye, is it?

Well, the speech centers are on the left-hand side of your temple, right?

So here.

And then he pulls it down, he's talking, pulls it down, and then there's a moment where he very convincingly fails to be able to speak.

Yeah it's pretty impressive isn't it?

Really impressive.

It's a really weird sensation because you know it's happening and then suddenly you have absolutely no control over what word comes out of your mouth.

But do you know the word still in your mind?

Yes.

You can still form the word in your mind.

So he's he's I think in this video he's it's a speech center which controls motor function.

So it's not to do with generating the thought, it's to do with getting it out of his mouth.

And if you get a motor center, a motor area for for a different part of the body, like Sophie said in that clip, you can, you know, get people to move their fingers in particular ways.

Anyway, look, that is quite enough about magnets.

It's definitely quite enough about the insane clown posse, who we really should have forgotten about in 2010.

We've got loads of some of us never heard of them.

Although

Felix had, he was well into them.

Strange thing about the insane clown posse is they turned out to be evangelical Christians.

Did they?

Yep.

Why were they insane?

Were they clowns?

Were they dressed as clowns?

Yeah, so

they used to put like one of the guys was a larger man, the other one was a thin man.

And they're both white guys, but their face, they were all, they know, no one knew who they were because they were always covered in black and white face paint, which did make them look kind of insane.

And they did a lot of very sweary, quite bad rap.

But then this one song, which became an internet phenomenon

in the innocent days of 2009, which included this

ridiculous line, which is

magnets, how do they work?

I don't want to talk to scientists.

I'm not going to talk to scientists because they're lying to you all.

Yeah.

But it also includes lyrics about the amazing things in nature that they also can't explain, such as rainbows.

Oh, I know how those work.

I know.

Most of the things in this song are things that scientists have known for, in some cases, literally centuries.

But then there's an amazing bit bit where one of them describes how one of the most miraculous things the song is called miracles so along with rainbows and magnets and giraffes another thing they can't explain and kittens and brown paper bags a different similar sort of sentiment but much more grimecore rap uh he describes a situation where he was down in san francisco bay and he was trying to feed a fish to a heron a pelican i'm sorry he was trying to fit he was trying to feed a fish to a pelican and the pelican stole his phone and ate it and then flew away.

It's an amazing song.

It's really not, it's terrible.

Should we do correspondence?

Yes, please, please.

Okay.

Okay.

Well, there were two curators who heard the story about your reply-all to your colleagues, Adam.

Oh, great.

One of my favourite stories of all time.

This is when I accidentally did a massive, humble brag to the entire faculty of the life sciences at UCL one week after I started my new ship.

He was asked to fill in a form about audience size, and Adam said, How's 2.4 billion for you?

Anyway, these two curies, they said,

But after they had finished laughing,

they actually both responded with

detailed instructions on how to set a delay to your outgoing email.

So you need to know how to set a one-minute delay before they leave.

You can track down Wolfgang Statler or Martin Rye.

The problem is, Wolfgang and Martin.

I think it was quite a lot longer than a minute later that Adam realized.

I think it was when the replies started coming in.

Yeah, thanks for that.

Yeah, let's bring back a painful memory for me there.

So another one.

Oh, this is also for me.

So the program we did about allergies.

A junior doctor called Miranda Chapman works on a pediatric ward.

She says, I was interested to hear Adam's vague recollection of a penicillin allergy, which is a common tale on the pediatric wards.

Oh, interesting.

Miranda recommends Adam gets an allergy challenge to find out if he really does have the allergy because she says more than 90% of children who thought they were allergic to penicillin can actually tolerate it.

So essentially, what she's saying is that my advice to you to just take some penicillin and see what happens was correct.

Thank you very much.

Yeah.

Do you know what?

I do accept medical advice from Miranda Chapman, the junior doctor in the pediatric ward, not from Professor Fry of the Maths Institute at UCL.

Yeah, this is probably fair.

This is a new section in the show that we've seen.

We've got correspondence.

That's what it has become.

Yeah.

Letters.

Yeah.

That's it for correspondence, but we've also got a Curie of the Week.

Curie of the Week.

So this week comes from Emmeline in Malaysia.

She says, hi, I'm Emmeline.

I'm 13 years old.

I live in Malaysia.

I started listening to your incredibly interesting podcast when the pandemic was at its peak.

Do you remember that?

You remember the pandemic?

I try not to.

No, not at all.

Yeah.

I was doing online lessons for at least six months and my internet was atrocious.

Then your Wi-Fi episode was released.

I feel I know where this is going, which is super cool, by the way.

And I thought to myself, wouldn't it be amazing if Hannah could come over to my house and help me fix my internet problem that my family and I have.

So just recall, listeners, that during the pandemic, when we were doing the program and writing our book, Hannah came over to my house where my internet was supremely rubbish.

Not because of your internet service provider.

I feel it's important that we point that out.

Nothing to do with the...

No, it was more to do with the very low level of interest I took in fixing it.

Yeah, low level of interest in fixing it, but quite a high level of anger at it.

Well, fix it, you did.

And Emmeline has picked up on this

and has said, well, yeah, wouldn't it be amazing if Hannah came up to my house and fixed the internet problem?

But you can't be hired without getting the word out first.

So basically, she's come up with an attached flyer for if science, communication, and maths doesn't work out for you as a career, or indeed a career in academia, you could go and set up a business.

which is Professor Hannah Fry's Wi-Fi Down Curios Internet Service Providing Call line support.

Yeah, my favorite thing about this, first off, it says my age, which I think is obviously an essential for any electrician.

Yeah,

I never get internet help from people older than 38, to be honest.

It says,

38-year-old Hannah Fryer with expert experience of always fixing her acquaintances.

Wi-Fi.

I think she just called you an acquaintance.

This is my favorite bit, though.

Package of being called names is included.

Accurate.

Absolutely.

So, I mean, so far, this is just your client list is one

but she's got you down as Instagram she's got the curio back here's an interesting thing though Emmeline

five pounds an hour no but that's not five pounds an hour for me fixing it that's five pounds an hour for every hour you use the internet after I've been at your house oh I see so if you could just cough up actually Adam that'd be that'd be wonderful she's put an email address and a uh and a website I'm gonna I'm gonna email the fry underscore electrician at gmail.com and see if I'm gonna have a phone number is that your phone number no should we ring it and and see what happens yeah shall we yeah right you know

you've dialed an incorrect number oh

how am I gonna get work how am I gonna get work she's she's absolutely condos anyway listen that flyer for I wonder what I wonder what service I could provide as a if I if it doesn't work out for me in this in this game um what service could you provide uh niche sci-fi quotes for hire sort of like a hotline

like a premium premium phone call line when you phone phone up and I'll tell you things about genetics and science fiction.

Let me try it.

Let me try it.

Let me just do this.

Oh, she's ringing my phone.

I see what's happening here.

All right.

All right.

Hello, Dr.

Rutherford's science fiction and genetics hotline.

How may I help you?

I'd like a quote, please.

Something to do with pigs and

space.

That's easy.

Is it?

Yeah, that's so easy.

Come on in.

Well, you must remember from the Muppets running from the 1970s well into the 90s that one of their drop-in segments was called Pigs in Space.

You don't remember that one because you weren't born were you?

No.

Let me do another one.

That's one pound an hour.

I would like

cabbage.

Cabbage.

Yeah, just anything to do with cabbage.

Hmm.

Well, Actually, in what's my favourite book?

What's the most important book ever written?

The Bible.

Guess again.

Guess again.

Brief history of anyone who ever looked.

That's not bad, but it does mention cabbages in that because it cites that the first chapter of The Origin of Species is not about natural selection, it's about artificial selection.

And he's mostly talking about pigeons and different races of

cabbages.

Yeah.

So are we saying now the origin of species is science fiction?

Good.

On that note, thank you very much for joining.

Man, I walked into that trap, didn't I?

Send us in your questions.

Send us in your

entries for Cure of the Week.

Send us in anything that you like to curiousgest at bbc.co.uk and we will see you next week.

Is Batman actually a baddie?

Wayne Enterprises have a huge carbon footprint.

What's really going on with Marvin Gay?

The moment you play it, everyone's raising eyebrows.

Was Cleopatra a snake or a saviour?

She's manipulated Roman leaders.

Maybe she had a great personality.

I'm Russell Kane and this is Evil Genius.

It's where I join a panel of comedians to reveal surprising things about historical icons.

Not even the hobbits are safe.

I'm on board.

Have you dated any?

Evil Genius with me, Russell Kane.

Listen on BBC Sounds.

Start your journey toward the perfect engagement ring with Yadev, family owned and operated since 1983.

We'll pair you with a dedicated expert for a personalized one-on-one experience.

You'll explore our curated selection of diamonds and gemstones while learning key characteristics to help you make a confident, informed decision.

Choose from our signature styles or opt for a fully custom design crafted around you.

Visit yadavjewelry.com and book your appointment today at our new Union Square showroom and mention podcast for an exclusive discount.

Ready to buy a car, a home, or just want to take control of your money?

Your FICO score matters, and 90% of top lenders use it to make decisions.

Check your FICO score for free today without hurting your credit score.

Visit myfICO.com/slash free or download the MyFICO app today.

My FICO gives you the score lenders use most, plus credit reports and real-time alerts to help keep you on top of your credit.

Visit myfico.com/slash free and take the mystery out of your FICO score.