I love that science has made so much progress in explaining the universe, unraveling its inner workings.

It's almost incredible what we've accomplished.

There's almost nothing left in our everyday lives that remains a true deep mystery.

Sure, the early universe and the black holes and lots of extreme situations still defy explanation, and we dig into those on the podcast all the time, But your everyday experience is mostly explained and understood.

The motion of the stars, the Sun, the planets, those are understood.

We know what an earthquake is and how weather works, even if we can't predict them very well.

Makes me wonder what it was like to be a human when there were unexplained mysteries right up in your face every day, when science hadn't fully conquered magic.

Today, we're going to try to get the flavor of that by talking about the remaining mysteries of one of the most magical forces in physics, magnetism.

Welcome to Daniel and Kelly's Extraordinarily Magnetic Universe.

Hello, I'm Kelly Windersmith.

I study parasites and space and magnets.

Man, how do they work?

What a miracle magnets are Hi.

I'm Daniel.

I'm a particle physicist and my job is to unravel how the world works.

And yet I sort of sometimes wish there really was magic.

Yeah, yeah, no, me too.

That would be pretty cool.

Like it's been really fun being a parent and seeing the like sort of magical world that resides in my daughter's head and kind of wishing some of it could be real.

But you know what exists in the real world is the Insane Clown Posse.

And are you saying they're magicians.

No, I think they're into magic.

So they the Insane ICP is from Detroit, and I grew up in Toledo, and so the Insane Clown Posse often had shows in Toledo, and I got sort of exposed to some of their music, and exposed is maybe exposed.

You know, I feel uncomfortable when I hear the word exposed, and that's how I felt when I listened to ICP.

But they had this one song, and anytime I hear about magnets, I think about this one song they had called Miracles, where this is a kid show, so I'm going to replace a word with stinkin'.

They'd be like stinking magnets.

How do they work?

And I was like, I think if you talk to someone, we could tell you there's probably an answer.

It doesn't have to be a miracle.

But they do go on to say they hate scientists, so that's I feel like they're not interested in what we have to say.

Thumbs down for that.

Well, you know, there's a lot of really interesting stuff there.

Like, on one hand, some of the stuff we figured out is as fascinating and amazing as the kind of magic that exists in those novels.

You know, like internet communication, I'm talking to you in real time across the country.

You know, like that's basically magic, but it's explained, it's understood.

And there's something about magic which is that it's not explained and not understood, which makes it sort of special.

And the thing about magnets is that, yeah, we know how electromagnetism works, and we can even understand it on the quantum level, and qwd's the most successful theory of all time dot dot dot dot dot.

And yet when you play with magnets, they do feel a little magical.

They do feel like a little bit beyond physics, don't they.

They absolutely do, and I think if you were to talk about like mag love trains, which I suspect is a slightly different situation, but I can't say I know about it, and you were to explain that to someone from like one hundred years ago, that and Zoom would absolutely feel like magic.

You know, Like I feel like the life we live in would feel like magic for people one hundred years ago.

I agree, Yeah, yeah, Like we went to the moon, man, we really did the moon in the sky, that's right.

Yeah.

And so on today's show, we're going to ruin magnets a little bit for all of y'all.

Right, magnets are not magic, and we're gonna explain the science of them.

And I did something a little bit different with this episode.

I wanted to really answer people's questions to resolve their magnetic mysteries.

So before I even got started writing this episode, I went out and asked people, what are the deepest mysteries of magnets?

What do people need explaining?

How can we ruin the magic of magnets for all of our listeners.

Our apologies to the Jugglers for demystifying the magic of magnets.

So here's what our listeners had to say if you would like to contribute your voice for future episodes.

Please don't be shy.

We'd love to hear from you.

Write to us two questions at Danielankelly dot org.

In the meantime, think about it for a moment.

What do you think is the deepest mystery of magnets?

Here's what listeners had to say, how migratory birds are able to detect magnetic fields.

To me, the most mysterious thing about magnetism is that it's not constantly canceling itself out, that we can have magnets at all, and that the atoms aren't just arranging themselves in such a way that the positive and negative are canceling out in any macroscale sort of way.

Historically, I wonder if magnetism is one of the earliest to perceive intersections between magic and science.

It's a mystery why Magnet and Steel was Walter Egan's only hit, because that's a great song.

I can get more magnets by breaking one into pieces.

Total mystery.

Spin creates it, but spin isn't really spinning, is it?

And then moving charges make magnetic fields, and magnetic fields make moving charges.

It's basically the universe's most passive aggressive friendship.

Also, magnetism is just electricity from a different perspective.

How magnets can attract and repul without touching.

There is no such thing as a monopole.

There always dipoles.

Why is it binary?

Why isn't there a third attraction?

So it all works in a triangle?

Is the repellent force between two magnets and the attractive force between a magnet and an object that's attracted to it?

I think that force.

Both of those forces are very mysterious.

I think is the fact that the north and south pull switch and we don't know why or like what causes it?

All right, Daniel, magnets, how do they work?

I don't know.

It sounds like we should invite Walter Egan to sing us his song.

I have to admit I haven't heard of Walter Egan.

Not that I'm like a great music connoisseur, but have you heard of Walter Egan?

It's no fair if you google it, Daniel.

So, Walter Egan's great hit apparently came out in nineteen seventy eight, and I was only three, so I think it was a little too young to enjoy it at the time.

So no, I'm not familiar with Walter Egan's only hit, but I'm gonna enjoy it after this recording.

Yeah, me as well.

We'll check it out.

But then, how do magnets work, Daniel, Yeah.

So magnets are amazing and fascinating, but they're best understood if we start with a related topic, which is electricity.

Because electricity magnetism very closely connected, and we can use our intuition for electricity to understand how magnets are similar and also crucially different.

So let's step away for a moment and start with electric charge.

So we know that you can have positive and negative charges, right, like the electron, what's its charge?

It's negative one.

Right, the proton, what's its charge?

It's positive one.

There's no like balancing charge to the electron.

You can have a proton and electron together, and you can make a neutral object or even like a dipole where you have like more negative and one side more positive on the other.

But you can also crucially separate the electron and the positron.

You can just have in principle, an empty universe with an electron in it, or an empty universe with just a proton in it.

So you can have positive charges, negative charges, and they can be isolated and separate.

Right.

We call these things monopoles mono because they're just one right, So they're alone, they don't have to come in pairs.

Crucially, they are the source of electric fields, right, Like if you have an electron in space, it makes an electric field, so it could push and pull on other electrons.

A proton can also make electric fields, and if you like to draw field lines, these lines start from the electron or the proton, right.

So that's the basics of electric fields and charges.

So to clarify for monopoles, when they're alone, do you have to have just one electron alone or you can have a bunch of electrons as long as they don't let any protons in.

Yeah, great question.

You can have just one electron alone.

You can also have like ten thousand electrons and they're a source of negative charge.

So that's ten thousand monopoles, which makes an effective monopole.

It's still only a negative charge.

It's a negative charge.

It's a source of the electric field.

Okay, so the word monopole refers to one electron alone or a bunch of electrons together.

It can be either singular or plural elonetrons.

Yeah, okay, yeah, I see how that's confusing.

What we mean by mono is not the number of electrons, but the fact that there is no balancing pole, because a diepole, in contrast, is a positive and a negative, where a net charge is zero, but a monopole has negative or positive net charge, even if it's one or seventy five electrons.

We got to make sure that we're clear because we've got to bring the juggalos along with this conversation.

Wait, can I just check the jugglos?

What are icps.

Going down that rabbit hole?

Here we go, not very far.

They are juggalos.

Okay, they are juggalos.

Oh got a picture pop brought back to my youth.

Okay, all right, So that's electricity.

What about magnetism.

Well, as we've talked about on the show a few times, this concept of charge extends to other forces.

We call it charge, but really the efficient name is electric charge, because we have also magnetic charges and weak force charges and strong force charges.

Okay, so magnetic charges, what do we call them?

We don't call them plus or minus.

We call them north or south.

And that's a historical anomaly because we associated with the Earth's magnetic field, which happens to be aligned mostly with the north and south poles, and so we call it a magnetic north or magnetic south.

But physically and conceptually abstractly, you should think of these insame category as electric plus and minus, just for magnetism instead of for electricity.

And so north is plus and south is minus.

No, No, not necessarily, It's just two labels like plus and minus are arbitrary.

Right, We could have called the electron plus and the proton minus.

Ben Franklin went the other way.

There's no necessary connection between north and south or plus or minus.

You're just biased for the northern hemisphere.

Kelly, Well, I like where I live, but I'm sure the southern hemisphere is lovely as well.

It was when I visited.

So are we going to get to why the Earth has a magnetic field too?

Yes, and what we don't understand about it and how weird it is definitely going to dig into that magic all right.

So, so far magnetism is very similar to electricity.

Here's the crucial difference.

There are no monopoles.

You can never have just a magnetic north the way you can have a negative electric charge or a positive electric charge by itself.

As far as we know, there is nothing which, if you put it in an empty universe, would just have a magnetic north or a magnetic south.

They only come and diepoles, pairs of north and south together.

Why yeah, why is a great question, and we don't have a good answer to that.

We think, actually, there should be Like physics actually wants there to be a monopole.

It would be a nice balance.

We'd like symmetry in the universe.

We like symmetry in the laws of physics.

And if you just looked at the equations, you're like, oh, yeah, there should totally be monopoles.

But we've never seen one.

We've never found anything out there that's the magnetic equivalent of an electron, Like an electron carries charge just on its own, just a negative charge, no balance.

We've never found anything out there that carries magnetic southgetic north.

The only way we've ever made magnets is by moving electric charges.

There's this connection between electricity and magnetism.

Electricity can generate magnetism, magnetism can generate electricity.

That's the only way we can make magnetism through charges, not through pure magnetic sources.

There are no sources of magnetism that are pure.

Okay, So when I have a magnet, it's because of stuff electrons and protons are doing in there.

Exactly.

One of Maxwell's equations, one of the crucial equations for electromagnetism, tells us that charges in motion make magnetic fields.

So you take a bunch of electrons, you run them down a wire.

What happens, They make a magnetic field around them.

So you can make magnetic fields from charges in motion, but you can't make them monopoles.

You can only make dipole fields.

A charge in motion can make a magnetic field, but it has to make a north and the south at the same time.

You can't just generate a north.

You can't just generate a south.

And is that the end here?

The answer is, we don't know why that's the case.

I think that's what you were saying.

We understand why you can't generate a monopole from electric charges.

We don't understand why there aren't monopoles out there that just make magnetic north or make magnetic south.

We don't know, and there might be it could be that they are somewhere in the universe.

But if they are, they are very rare.

We've never seen them.

We've looked for them, and we can dig into that in a minute.

But every magnetic field we've ever made or seen, or that you've used, doesn't come from some inherent source of the magnetic monopole, the way electric fields come from electrons or protons.

It comes from electric charges in motion.

So why do electric charges in motion result in a north and a south?

Have I just asked the same question in a slightly different way?

Okay, no, no, No, that's a great question.

And this is a very mathematical answer if you look at the structure of Maxwell's equations.

But intuitively, the way to think about it is think about the magnetic field that's generated when electron moves down a wire.

It's got to be in a loop.

It's a curl equation, so it makes a magnetic field in a loop around the wire, and there's no source there.

The magnetic field line starts and ends on itself.

It doesn't start or end in a specific location, so there's no end points there.

Monopoles have end points for magnetic fields, but an electronic motion can't make that.

It can just make a loop that ends and starts on itself, and that has a north and the south all together, and so it can't generate these sources.

So let's talk about the two kinds of magnets that we have experience with the kitchen magnet, like a permanent magnet, like a pheraohmagnet, and then we'll talk about electromagnet, so a ferromagnet.

You might ask, like, I have this thing on my fridge, I'm not running electricity through it.

What charges are in motion?

And this is exactly the question I just got yesterday as I was prepping this episode.

So here's David Naylor asking us this question.

Hi, Daniel and Kelly.

I'm told that magnetic fields are generated by moving electron charges.

So my question for you is what moving electron charge is powering two magnets that I hold in my hand.

Thank you both for an awesome show, and I can't wait to hear your answer.

Well, David, since we both asked exactly the same question, I've got to say that this is a truly great and insightful question.

What is the answer, Daniel?

Are you inviting David to join your insane magnet posse?

Yes, the megalows.

Right, So what's moving here to generate this magnet?

So zoom in on the magnet.

You have molecules of iron.

Inside those molecules, you have the nucleus, and you also have electrons whizzing around.

Right.

Well, all of these fundamental particles have something we call spin.

It's quantum spin.

They're not physically spinning, but they have this property which is very closely related to spin.

And one of the reasons we say that this property is related to spin is that it has a lot of the same behavior as classical spin.

Like if you take a metallic sphere that's charged and you spun it, it would generate a magnetic field.

Why, because you got charges in motion.

You have charges attached to the surface of the sphere and they're in motion.

Generates a magnetic field.

Cool.

If you have a fundamental particle like an electron, that's charged and you give it quantum spin, it also has a little magnetic field.

It has a little north and a little south.

Why is that exactly?

It's a little bit circular.

Like we call it spin because we see that it generates magnetic field, and so we're like, well, whatever, this quantum spin thing is it has angular momentum and it generates magnetic fields.

So it's a lot like spin, So we'll call it spin.

So you can either say, well, something is happening with the electron to generate these mini mechnetic fields and it's related to spin, or you can say we call it spin because it generates magnetic fields.

It's sort of two sides of the same coin.

But basically each little electron is its own mini magnet.

Okay, So I'm just trying to make sure I've got my head around them.

So you were saying that electrons are like all negative, totally negative, but they can still have a north in a south because north and south is not the same thing as positive and minus, despite the fact that I have locked that into my brain.

So what does it really mean then, to say that an electron has a north in a south pole.

So electrons can spin in two different ways.

They can spin up or spin down.

If it spins up, then it has a north and a south pole.

If it spins down, then it has a south and a north pole, if you like to think about it that way.

So the direction of its spin determines which side of it the electron is north and which side is south.

And then if you pass them through a magnetic field, spin up electrons will go one way and spin down electrons will go the other way.

This is actually the crucial experiment that revealed that electrons could only have two spins up or down as they passed them through a magnet.

And they didn't see a whole distribution of electron deflections.

They saw two deflections either left or right.

They were tightly clustered.

So you can use the magnetic field of the electron to measure its spin because it's not closely connected.

So to answer David's question directly, like, we don't want to say that electron is in motion because it's a quantum particle and it doesn't have a surface, and it's not really spinning.

But the quantum spin of the electron is analogous to electric current, and together with the electrons charge that generates a little tiny dipole magnet.

Okay, so I'm thinking about my kitchen magnet and I've got some electrons spinning up, some electrons spinning down.

Is the top of my magnet, yeah, or the bottom whatever?

Is one side of the magnet where my electrons that are spinning up live and the bottom side is where my electrons that spin down live.

And why don't they mix together?

Does that seem like a cozy little neighborhood organization.

It sounds like they're segregating.

I don't like that one.

Oh no, you're right exactly.

Let's mix everybody.

Yeah.

Well, if you just take a hunk of iron out of the earth, then it's got all these little electrons and they have all their little magnetic fields, but they're all pointing in random directions, and so it doesn't act like a magnet.

And actually, if you zoom in, you find that they have organized themselves into little megas knetic domains, little clusters where they all point the same direction, and then there's another cluster pointing the opposite direction.

But on a macroscopic scale, they all add up to nothing.

They cancel each other out.

What happens if you bring another magnet nearby is it'll start to flip those guys, right.

Those magnets will align with the other magnets.

So that's why if you bring like a hunk of iron near a magnet, it gets magnetized.

What you're doing is just rearranging all of those electrons, so they're no longer fighting each other, and they're now all aligned in the same direction, and they add up instead of canceling out.

They add up to an overall magnetic field.

Okay, so you're not just moving them around so they're in like groups, you're actually flipping them all to the same direction.

Yeah, okay, And we're talking about electrons here because they're easiest to think about.

But it's not just the electrons to have these magnetic fields.

Protons of magnetic fields.

Also, the neutron even has its own residual magnetic field because it has quarks inside of it which are charged, and so you can measure the magnetic moment of the neutron or of the proton or the electron.

And so I'm saying electrons, that really mean like all the particles inside that add up to do this.

And so you can make pretty powerful magnets with the right materials that have like the right structure and everything can align nicely.

The strongest magnet we've ever measured is about one and a half tesla, which uses neodymium, iron and boron magnets, and that's pretty powerful.

I remember, the Earth's magnetic field is almost a million times weaker than that.

It's like thirty to fifty micro tesla.

So we can make very powerful magnets that like are much more powerful than the Earth's magnetic field.

So I'm thinking of the Brave Little Toaster and the giant magnet that was picking stuff up to throw it away in the landfill.

So like one point for tesla?

How many?

How many cars could you pick up with that?

What are we talking about?

The Brave Little Toaster is a classic.

I don't know, the Brave Little Toaster.

I got a lot of cultural homework to do after this episode.

We were born in the wrong decade, man.

Yeah, exactly.

Well, you could pick up a lot of cars, but actually, those big guys is that pickup cars tend to be electro magnets.

Because those are magnets you can easily turn off and on, Like you could demagnify something by trying to reflip it and re randomize all the magnetic domains.

But that's a lot of work.

Instead, the other kind of magnet is very easy to turn off or on or reverse.

All right, magnet I've got on my fridge.

It has electrons spinning up on one side, electrons spinning down on another side over time, would I expect those to like decay where some of the ones that are going upstart going down, or they just keep spinning in the direction they're spinning in unless you do something to force them otherwise.

Yeah, this is a great question.

People often ask this because they imagine, like, why do magnets not lose their energy?

Yeah, but yeah, they just point in the same direction unless something comes along and flips them.

And so to demagnet as a magnet, you'd have to like flip some of the electrons or some of the particles one way and not the other ones, which would be pretty tricky.

And they can just sit there and keep spinning in the same direction without requiring any energy, you know, the same way that like a rock can sit on the top of a hill until somebody comes along and pushes It takes energy to move the rock.

So we can get more into that in a minute.

But yeah, they will keep spinning in the same direction unless you come along and scramble them.

All right, Well, let's take a break and get more into that.

All right, So my brain is stuck on the brave little toaster now, and that electromagnet that was picking cars up and slinging them around and throwing them down.

How do electromagnets work.

So electromagnets are like macroscopic versions.

Right a minute ago, we were talking about microscopic electrons.

We say they have charge and spin and therefore they generated magnetic field.

Here, we just take a bunch of electron, as we say, whiz them around in a circle.

That's charges in motion, and so that generates a magnetic field.

And you know that's just says current.

So if you want a straight up magnetic field, for example, you make a loop of wire, you like wrap wire around a cylinder and then as the electrons go through that wire, they generate a magnetic field in a loop around the wire, and then inside that cylinder they all add up in the same direction to make a big magnetic field.

So this is what an electromagnet is.

It requires running a current.

You have to run energy through it.

So you run out energy, boom, your magnet turns off.

This is for example, how an electric motor works.

Has an oscillating electromagnet.

You turn the magnet in one direction so it pulls on something.

Then you turn it on the other direction so it pushes and it oscillates very rapidly to spin that rotor.

Every electric motor uses electro magnets.

What kind of things in our lives use electric motors?

Evs, Oh, yes, what.

About my hybrid?

Does my hybrid use an electric motor?

Your hybrid definitely has an electric motor.

And like every robot you've ever seen and anything that goes like all that stuff, you know, use this little electric motors.

Electric motors are everywhere and they're wonderful, and you can combine these two things.

You can take an electric motor and instead of just having like a plastic cylinder whatever, you can use a ferromagnetic cylinder.

So now you're electromagnetic motor is aligning the spinning electrons of the ferromagnet.

So it all adds up and you get like a really powerful magnet.

So people have been doing experiments to try, like make the most powerful electromagnet possible to see like how much magnetism can we have in a little bit of space?

So why would having a permanent magnet and then running electricity through that make it more intense?

Like you know, you've already got the electrons doing their thing and running current.

Why does that supercharge the magnetism, magnet or magic.

There's no here, It's just that if you have the electromagnet, it generates a magnetic field through its core.

That's one magnet.

If you add a chunk of iron, then your electromagnet will align, will magnetize your iron for you.

So now you have a permanent magnet adding to your electromagnet.

So it just adds up.

So you use the electromagnet to magnetize your chunk of iron to give you a permanent magnet, and now your permanent magnet just sits there adding to your electromagnet.

If that's what you want, right.

If you want an oscillating magnetic field, then that's not what you want because you can't turn off the permanent magnet or oscillated very quickly.

But if your goal is to like be a magnet nerd and make the most powerful magnet ever made on Earth, then that's what you want, and that's what people are doing.

And why would you want to make the most powerful magnet ever made on earth?

Is there like a thing you can do once you have that?

Or is it just awesome?

You get to be the magnet king or queen I mean, come on, kell, Queen of thes, I just think it's cool.

You know, probably there will be some outplications someday, and I hope it's not weapons.

But you know, a lot of us who got into physics just do things because like, let's see if we can and what happens, and maybe our theory breaks down, and you know, these things are fascinating.

Yeah, I'm fascinated.

So what is the biggest magnet?

Who is the current a monarch of the magalows?

Yeah.

So one of the first guys to get into this was an American physicist named Francis Bitter.

If you look into no, and he's not a very bitter guy though.

The magnets that he inspired and he designed are called it bitter magnets, but you know, they don't taste bitter.

Nobody's grumpy about them.

They're just named after Francis Bitter.

Okay, So he and his design of magnets set a record of forty one point four tesla, which is a huge amount of magnetism.

Right.

Remember, the strongest permanent magnet ever was like one and a half tesla, So already blowing out of the water, all permanent magnets.

The limit there is that there's so much energy in this magnet that basically it'll overheat.

There's not a physical limit, like it's not that you can't have more magnetism or density or something.

We think it's just that it melts the whole apparatus because there's so much energy in it.

And that's because you know, you can't have current without loss, and the resistance of your wire is going to heat up everything, and you're just going to melt your whole apparatus.

So people said, well, let's try to use superconductors.

Right.

Superconductors are famous for having low resistance, so higher currents, so bigger magnet.

Yeay, And that's very cool, And we use superconducting magnets in for example, the Large Hadron Collider.

Say you wanted really powerful magnets because you wanted to bend the path of super high energy particles so you could collide them together and reveal the secrets of the universe.

See, there you go, there's an application for very powerful magnets.

Yay.

Why didn't you come up with that sooner?

Daniel?

This is what you do, man.

I wanted to lead into it a little bit.

More you're good at this, yes, yes.

And that sounds awesome.

But the problem is that superconductivity is not something we understand super well, and at some point, having a lot of magnetic field interferes with the superconductivity.

And the superconductivity comes from like electrons behaving weird, they pair up with each other and flow differently, et cetera, et cetera.

It's not something we super understand, but we do know that magnetism interferes with it.

And so there's a limit there.

And they've only gotten to like thirty two tesla at the National Magnetic Field Lab in the US.

So that's what ten tesla less than what bitter was doing, Is that right now?

Yeah?

Exactly?

Okay, yeah.

So then somebody said, well, let's combine all the best ideas out there, right, oh yeah, let's have a bitter magnet with superconductors, and they were able to get up to forty five tesla.

This is the Florida State Magnet Lab, and so that's the current record for a magnet that lasts more than a few microseconds.

A magnet's like stable and you could use it to do something, for example, But there are other folks out there they're like, so what if your magnet milts?

So what if the whole apparatus blows up, You still got a powerful magnet.

So there are folks working on something called explosive magnets that says like, let's just try to get the most powerful magnetic field ever.

We don't care if the whole building collapses afterwards.

We still get the record.

Okay, I mean I can get behind that attitude, But can I take one quick step back?

So yeah, I thought that the Okay, so when we talked about using a superconducting wire, I thought you were taking the bitter magnet plan but using a superconducting wire instead.

So what does it mean to say you're doing a hybrid of the bitter and the superconducting idea.

The answer is a little bit technical.

The way a bitter magnet works is or requires these circular plates with insulating spacers in them, and it's not very conducive to the superconducting setup.

So people started from a different approach using superconductors, and then later they're like, made some efforts to try to bring these two designs together.

So sort of a compromised design, but has to do with the detailed geometry of bitter magnets.

Awesome, Okay, thanks, Now let's blow some stuff up.

Yeah.

So not only are these folks willing to let their magnet get blown up, but they're going to literally use explosives to generate the high magnetic field.

They use explosives to compress the whole apparatus, so you get a higher density magnet as the explosion is happening.

And the record here is twenty eight hundred tesla.

Wow, so we're almost one hundred times what the bitter superconductor magnet at the FSU Magnet Lab can do, but only for a few microseconds.

Still pretty awesome.

Yeah.

I can't imagine you're going to get a government to fund an LHC that runs on explosive magnets, you know.

Oh that would be cool though, Yeah, be cool.

Every decade you get one really big batch of data and then you got to start over again.

But before you feel too proud of humanity's achievements, let's put it in like astronomical context.

Right, twenty eight hundred tesla is a lot bigger than the Earth's magnetic field, which is like thirty to sixty microtesla.

But a neutrons is already at a million tesla.

Oh wow, right, so we're talking a thousand times are explosive magnets and a magnetar, a super magnetized version of a neutron star that's a pulsar and spinning and crazy, has ten to the eleven tesla, So like blowing us out of the water by a factor of ten to eight.

So yet nature can do what humanity can't.

Still, all right, well, so I've decided instead of the magelos, we're going to be the magnetars because that sounds way cooler.

I'm sorry to the juggalos out there, but the magnetars are going to.

Take over the world, all right.

And so that's the basics of how magnets work.

We got permanent magnets, we look got electromagnets.

We've got magnetism generated by charges in motion.

One of the other questions that the listeners asked was why are there no monopoles?

Why do we only generate magnetic fields from dipoles?

And we talked about this a little bit, but I want to dig a little bit deeper into it because I want to explain why physics wants monopoles to exist.

All right, let's see how many different ways there are to say we don't know.

I mean, if you just looked at the equations, if you write down Maxwell's equations, you see they describe how electric fields are generated from sources you know, positive and negative charges, how magnetic fields are generated from those sources in motion, how you can even get current from magnets, all sorts of back and forth.

It's beautiful.

The symmetry is gorgeous.

But there is one flaw in it, this one glaring omission, this lack of symmetry, which is that there are no sources of magnetic fields.

And so in the equations we just say zero, right, the total sources of magnetic fields are zero.

It would be so much nicer if we could replace that zero with something that paralleled what happens in electricity, where you have monopoles, you have sources of fields.

And so that awkwardness makes physicists want to be like, well, what if there are our poles out there, we just haven't found them yet, you know, because that would make the equations more beautiful.

And let me remind you that beauty and symmetry in physics has led us to real discoveries before, Like even in this particular aspect.

When Maxwell was putting his equations together, he noticed that there was a term that was asymmetric.

He was like, hmm, it would be more beautiful if this other term existed, And then he went out there and actually found the effect.

He's like, oh, this is a real thing in the universe, just nobody has isolated it and looked for it before.

So symmetry does lead to discoveries like mathematical insight really does reveal physical nature of the universe, which is like cool and philosophical and tells you like, wow, maybe the universe really is mathematical, and so it inspires us.

It says, hmm, wouldn't it be cool if there was a full symmetry if these equations really were exactly the same for electricity and magnetism.

Because remember, electricity and magnetism are not separate things.

They are two sides of the same coin.

It's not even always possible to draw a dotted line and say this is magnetic and this is electricity.

Like let's say, for example, I'm holding an electron.

I see an electric field, right, I don't see any magnetic field because I'm just holding it.

It's not moving.

But what if Kelly drives by, you know, at fifty miles an hour, she looks at my electron.

She's like, no, that electron is moving because according to you, it's moving a fifty miles an hour.

So do you see a magnetic field?

Answer is yes, So you see a magnetic field and I don't because really it's just electromagnetism.

Right.

This dotted line we draw between them is an artifact of humans being like, oh, electricity is lightning, magnets are weird rocks.

These are separate things, and later we realize they're actually just two sides of the same coin.

So it would be beautiful if you could fully unify these things, if we saw monopoles.

Every time I talk about beauty and symmetry and physics, I find myself really wanting a framework for when we should be able to say, oh, it would be beautiful if there were this other thing to complete the symmetry.

And then whenever we don't see a symmetry, is that because we're missing something or is it just like, well, there, it just isn't symmetrical.

Like when should you see symmetry and when should you not?

We don't know, and it sounds arbitrary and biased, and the only real explanation, if I want to be honest, is so far this works.

Like looking for symmetry and trusting our gut about like what is beautiful and elegant has led us to discoveries.

That doesn't mean it always will.

The universe could be a mess, you know, it could be ugly deep down.

And this is something you and I have talked about, like why do we find vista is beautiful?

Why are flowers pretty?

They're not designed for us.

This whole sense of aesthetics.

It feels weird and subjective and not scientific, And yeah, that's true, but there's a lot of subjectivity in thinking about what to explore.

In the end, the data's got to tell you what's real.

But when you're like hunting for ideas, trusting your gut and looking for beauty is useful.

And there's another reason why we think magnetic monopoles might exist, which is if they did, it would instantly solve another deep question about the universe, which is why is electric charge quantized?

Like why do we have electrons that have plus one charge but there's no particles with like one point zero zero four to two charge or seventy five point nine charges that come in these increments, and quarks have one third and two third charge, but they're still quantized.

Nobody knows the answer to this.

But if there was a magnetic monopole, even just one that existed in the universe, it would answer this question.

WHOA, all right, this is Schrodinger's equation, right, So would that mean that if if we found one, would that mean his equations were wrong?

Or would that complete his equations?

This has to do actually with quantization of angular momentum, right.

We know that angular momentum is quantized, and we know this relationship between electricity and magnetism, and so it's very easy to derive this quantization from the existence of monopoles.

It's a few steps in the equations, and so famous physicists like Joe Polchinsky says, quote, magnetic monopoles are one of the safest bets that one can make about physics not yet seen, like if you had to guess about future discoveries.

A lot of physicists are confident that eventually we will see a magnetic monopole.

Oh wow.

And it's not like we haven't looked.

We've been looking for them it's actually quite easy to see a magnetic monopole.

All right, I'm dying to know how we've been looking for them.

So let's take a break, ruminate on beauty and what it means for our universe, and when we come back, we'll find out how you find monopoles.

All right, you were about to tell us how we go about looking for monopoles.

So what have we done so far?

There's two categories of ways to discover monopoles.

One is try to find them already existing in the universe, and the other is try to make some.

So how do you find a monopole?

Well, let's think about early experiments with magnets.

Right.

Faraday did these experiments where you had a coil of wire and he passed a magnet through it, and he saw that it generated a current.

Right, And but the crucial thing is all the magnets he had had a north and a south.

So he would pass the north part through the wire and it would generate a current one way, and a south part would then follow and it would generate a current the other way.

So if you have a dipole that goes through a loop of wire, you get current one way and then current the other way.

It all adds up to zero because the dipole has no net magnetic charge.

But if you have a monopole that passes through, it just generates current in one direction.

That's it.

So what do you do.

You build a huge loop of current to capture any monopole that happened to fly through, and you wait and you just see, maybe we'll find one.

And some guy built a really big wire and he ran it for a while.

And there was this event on Valentine's Day nineteen eighty two where he saw a huge bike a current only in one direction.

Boom.

It looks exactly like a monopole.

But it's never been replicated.

Nobody's ever seen another one.

So either monopoles are super dup or rare in the universe, and he happened to capture one, nobody has been able to do it since, which means they must be super rare, or it was a glitch or some weird error and not a real signal.

Nobody knows to this day, Like did he really see a monopole?

You can't really conclude yes based on just one observation, So.

Is like essentially this experiment running continuously looking for so we're it's still running, still looking, and it's only been seen once in forty years.

Yeah, exactly.

Wow.

And so if he's right, it means that monopoles are like very rare, Like there's less than one monopole per ten to the thirty atoms, which you know that's not actually that rare, because there's a lot of ten to the thirty atoms in the Earth, for example.

But you know, if monopoles are out there, they're super duper rare.

So the other thing we try to do is let's make them.

One thing we can do with colliders is create new kinds of matter that we don't have ways to build otherwise.

You know, we smash protons together, it turns into some intermediate state, and then through alchemy basically we can create new kinds of matter.

We create electrons or muons or quarks or whatever.

And so people have tried to make magnetic monopoles at the collider.

It's nothing you do in particular.

You just look to see, Hey, if we smash protons together often enough, do any of these guys come out, And so far we haven't seen any.

They would act weird in the magnetic fields that our detectors are immersed in and so there would be a very obvious signal, but we've never seen one so far.

How long have we been using this method to look for monopoles.

Basically, every time we run a collider, we look through the data for monopoles, and we've been doing collisions for fifty years or so.

Basically at this level, we look for them at the large hadron collider, we look for them at the tempatron, we look for them at the large electron proton collider.

We've never seen anything that looks like a monopole.

So that's disappointing and it's confusing because boy, sure would be beautiful if monopoles existed, and it would be an amazing discovery, but we've never seen one, and so maybe the universe just is asymmetric in this way.

So, say you do see a monopole, but it really is so rare that you see it, you know, one time every forty five years.

Is that still as amazing If it's just this rare blip that sometimes happens in the universe.

It's still as amazing because their very existence would be satisfactory.

It would open up new questions like, well, why are electric monopoles everywhere and magnetic monopoles super duper rare.

That would need to answer the same way that, like matter is everywhere and antimatter is super duper rare.

That would be another asymmetry we'd have to explain.

But if they did exist, it would be a very different universe than one in which they were prohibited and which they just cannot exist for some reason we don't yet know.

Well, my favorite dipole is Earth.

I'm a big fan biased Yeah, well so, yeah, that's fine.

You can check out my whole book for why I think the Earth is so great?

So why is Earth such?

What makes Earth such a great dipole?

Daniel?

Is that why you don't want to go to Mars because there's no magnetic field there and you just pro Earth's magnetic field?

Yeah, I mean I don't think the magnetars and I would feel really comfortable on Mars.

You know, we need a strong diepole.

Well, the Earth has a big magnetic field.

We all know that because we use compasses to navigated for thousands of years.

It's not a permanent magnet, right, It's not just like there's a hunk of iron down there that has a magnet to it because it's changing, right, the Earth's magnetic field is not constant.

We don't fully understand where the Earth's magnetic field comes from.

Roughly, we know that the Earth has a fluid layer.

There's rock down there that's under a lot of pressure, and there's convection, so the stuff is bubbling and rising and then sinking.

So you get these like loops of stuff moving and the Earth is spinning, and so Roughly, probably the explanation is that molten liquid currents of this stuff that and it's charged.

These are metals, a lot of them give a magnetic field.

And once you have a magnetic field, that magnetic field can drive currents, and those currents can make more field, and those fields make more currents.

You get this dynamo effect that enhances itself.

But what we know is that this is not something that's just fixed.

It's not like the Earth has how the same magnetic fields for four billion years.

It changes and it changes in weird ways.

And is it changing because convection can be sort of like random, and it's not always happening exactly the same way.

We don't know, Like we see these reversals through history and the reversals are not periodic, like sometimes it's every fifty million years, sometimes it's every hundred thousand years.

The most recent reversal that we've seen is about eight hundred thousand years ago.

The polls were the opposite.

So like, if you took a compass from today and went back in time a million years, the compass would point north towards the south pole.

What would we be totally screwed if that happens?

How how fast does it happened?

Is it like, you know, Monday morning it's one way and Monday afternoon it's the other.

No, it doesn't happen that fast, but it might be happening right now.

Like right now, the Earth's north pole is drifting.

It's moving away from the location around which the Earth is spinning, the sort of geometric north pole and towards Siberia at forty kilometers per year, and every year that gets faster.

Oh yeah, so wow, are we sure it's going to go all the way or could this just be like a we don't know, jiggling.

It could just be a juggalo, you know, for all we know.

But the cool thing is that we can measure the Earth's magnetic field through history.

This is one of those amazing moments when people have come up with this incredible detective strategy to unearth some data from history.

We can use magnetized lava that's frozen on the sea floor.

What So, there's these parts of the sea where like you're making a lot of new rock all the time.

So you're making new crust of these like mid ocean ridges that come out and then spreads outwards, and these are susceptible to magnetism, and so they get magnetized by the Earth's magnetic field.

All the little particles aligned in one direction and then they freeze right, and so you get these stripes as the Earth's magnetic field flips.

This palaeomagnetic record is formed.

It's like a tape recorder of the Earth's magnetic field.

You can go down and measure the magnetic field of this lava and you're like, oh, it's flipped.

Oh it's back.

And if you know when it was made, you can reconstruct the whole history of the Earth's magnetic field.

Isn't that amazing?

Aren't scientists so clever?

That is so cool?

And you know, the folks in the geology section on our discord are rejoicing because we've we've done something in their wheelhouse now, so yeah, that is incredible.

Yeah, so we know that it's happening, We know that it's irregular.

We don't know why.

And in contrast, for example, the Sun has a magnetic field that flips every eleven years, super regularly, like every eleven years for like a long long time.

Why does the Earth have a magnetic field that flips irregularly?

We don't know.

Why does the Sun or versus field ever eleven years?

We don't know.

We think the Sun's magnetic field comes from connection of plasma inside it.

We don't fully understand it.

Huge question.

You know.

Mars we think has no magnetic field because it's essentially frozen.

There might be some motion inside Mars, but there's no dynamo inside Mars.

Venus has no field, Jupiter has a huge field.

Some moons have magnetic fields if we think they have internal motion.

So there's some understanding of a lot of big questions left about planetary and lunar magnetic fields.

So a little bit of magic left to demystify, all.

Right, Kelly, So are magnetic fields still magic to you?

You know?

I still feel like science holds a lot of magic in a good way, Like it's amazing that we've been able to figure this all out.

And maybe I'm stretching the definition of magic, but I still feel I still feel inspired and uplifted, and I get that sort of like magical tingly feeling what I learned about some of this stuff and the fact that we figured it all out.

Yeah, I think it's satisfying to replace the mystery with understanding.

It's not magic in the same way, but its scratches a deep bitch for me.

Me too.

I think if I said this to my daughter, she'd be like, come on, mom.

But I still feel that in my bone.

So let's go with it, all right.

Well, thanks to everyone for writing in with your questions about magnetism, and stay tuned for new episodes.

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