September 23, 2025 • 48 mins
Daniel and Kelly dig into the mysteries of magnetism, explaining how magnets work and what they reveal about the Universe.
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Speaker 1 (00:08):
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
(00:31):
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
(00:52):
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.
Speaker 2 (01:23):
Hello, I'm Kelly Windersmith. I study parasites and space and magnets. Man,
how do they work? What a miracle magnets are Hi.
Speaker 1 (01:32):
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.
Speaker 2 (01:41):
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.
Speaker 1 (01:56):
And are you saying they're magicians.
Speaker 2 (02:00):
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
(02:21):
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.
(02:41):
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.
Speaker 1 (02:48):
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,
(03:09):
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
(03:32):
little bit beyond physics, don't they.
Speaker 2 (03:34):
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.
Speaker 1 (03:54):
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
(04:16):
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.
Speaker 2 (04:30):
Our apologies to the Jugglers for demystifying the magic of magnets.
Speaker 1 (04:36):
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.
Speaker 3 (04:57):
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.
Speaker 4 (05:13):
Historically, I wonder if magnetism is one of the earliest
to perceive intersections between magic and science.
Speaker 2 (05:19):
It's a mystery why Magnet and Steel was Walter Egan's
only hit, because that's a great song.
Speaker 4 (05:25):
I can get more magnets by breaking one into pieces.
Speaker 1 (05:29):
Total mystery.
Speaker 5 (05:31):
Spin creates it, but spin isn't really spinning, is it?
Speaker 4 (05:34):
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.
Speaker 3 (05:45):
How magnets can attract and repul without touching.
Speaker 1 (05:48):
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?
Speaker 6 (06:00):
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.
Speaker 3 (06:10):
I think is the fact that the north and south
pull switch and we don't know why or like what
causes it?
Speaker 2 (06:16):
All right, Daniel, magnets, how do they work?
Speaker 1 (06:21):
I don't know. It sounds like we should invite Walter
Egan to sing us his song.
Speaker 2 (06:24):
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.
Speaker 1 (06:38):
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.
Speaker 2 (06:51):
Yeah, me as well. We'll check it out. But then,
how do magnets work, Daniel, Yeah.
Speaker 1 (06:57):
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
(07:18):
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
(07:39):
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
(08:01):
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
(08:22):
and charges.
Speaker 2 (08:23):
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.
Speaker 1 (08:33):
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.
Speaker 2 (08:51):
Okay, so the word monopole refers to one electron alone
or a bunch of electrons together. It can be either
singular or plural elonetrons.
Speaker 1 (09:00):
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.
Speaker 2 (09:20):
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.
Speaker 1 (09:29):
Going down that rabbit hole?
Speaker 2 (09:30):
Here we go, not very far. They are juggalos. Okay,
they are juggalos. Oh got a picture pop brought back
to my youth.
Speaker 1 (09:42):
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.
(10:05):
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
(10:26):
instead of for electricity.
Speaker 2 (10:28):
And so north is plus and south is minus.
Speaker 1 (10:31):
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.
Speaker 2 (10:45):
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?
Speaker 1 (10:56):
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,
(11:18):
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.
(11:39):
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
(12:01):
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.
Speaker 2 (12:22):
Okay, So when I have a magnet, it's because of
stuff electrons and protons are doing in there.
Speaker 1 (12:28):
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
(12:50):
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.
Speaker 2 (13:01):
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.
Speaker 1 (13:07):
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
(13:29):
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.
Speaker 2 (13:39):
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?
Speaker 1 (13:47):
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
(14:08):
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.
(14:29):
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.
(14:50):
So here's David Naylor asking us this question.
Speaker 5 (14:53):
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.
Speaker 2 (15:11):
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?
Speaker 1 (15:21):
Are you inviting David to join your insane magnet posse?
Speaker 2 (15:26):
Yes, the megalows.
Speaker 1 (15:31):
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
(15:52):
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.
(16:13):
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
(16:34):
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
(16:55):
is its own mini magnet.
Speaker 2 (16:57):
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.
Speaker 1 (17:18):
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
(17:39):
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
(18:02):
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.
Speaker 2 (18:18):
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?
Speaker 1 (18:37):
Does that seem like a cozy little neighborhood organization.
Speaker 2 (18:40):
It sounds like they're segregating. I don't like that one.
Speaker 1 (18:42):
Oh no, you're right exactly. Let's mix everybody.
Speaker 5 (18:45):
Yeah.
Speaker 1 (18:45):
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
(19:06):
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
(19:26):
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.
Speaker 2 (19:33):
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.
Speaker 1 (19:38):
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
(19:59):
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
(20:21):
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.
Speaker 2 (20:33):
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.
Speaker 1 (20:49):
I don't know, the Brave Little Toaster. I got a
lot of cultural homework to do after this episode.
Speaker 2 (20:54):
We were born in the wrong decade, man.
Speaker 1 (20:55):
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
(21:17):
or on or reverse.
Speaker 2 (21:19):
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.
Speaker 1 (21:39):
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
(22:01):
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.
Speaker 2 (22:17):
All right, Well, let's take a break and get more
into that. All right, So my brain is stuck on
(22:40):
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.
Speaker 1 (22:47):
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
(23:10):
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
(23:32):
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.
Speaker 2 (23:53):
What kind of things in our lives use electric motors?
Speaker 1 (23:57):
Evs, Oh, yes, what.
Speaker 2 (23:59):
About my hybrid? Does my hybrid use an electric motor?
Speaker 1 (24:02):
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
(24:25):
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?
Speaker 2 (24:43):
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.
Speaker 1 (24:59):
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,
(25:22):
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.
Speaker 2 (25:42):
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?
Speaker 1 (25:50):
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.
Speaker 2 (26:12):
Yeah, I'm fascinated. So what is the biggest magnet? Who
is the current a monarch of the magalows?
Speaker 1 (26:19):
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,
(26:43):
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
(27:07):
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
(27:29):
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.
Speaker 6 (27:51):
Yay.
Speaker 2 (27:51):
Why didn't you come up with that sooner? Daniel? This
is what you do, man.
Speaker 1 (27:57):
I wanted to lead into it a little bit.
Speaker 2 (27:59):
More you're good at this, yes, yes.
Speaker 1 (28:01):
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
(28:22):
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.
Speaker 2 (28:31):
So that's what ten tesla less than what bitter was doing,
Is that right now?
Speaker 6 (28:35):
Yeah?
Speaker 1 (28:35):
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
(28:56):
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.
Speaker 2 (29:17):
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.
Speaker 1 (29:39):
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
(30:00):
detailed geometry of bitter magnets.
Speaker 2 (30:03):
Awesome, Okay, thanks, Now let's blow some stuff up.
Speaker 1 (30:05):
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
(30:25):
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.
Speaker 3 (30:34):
Yeah.
Speaker 2 (30:35):
I can't imagine you're going to get a government to
fund an LHC that runs on explosive magnets, you know.
Speaker 1 (30:40):
Oh that would be cool though, Yeah, be cool.
Speaker 2 (30:42):
Every decade you get one really big batch of data
and then you got to start over again.
Speaker 1 (30:46):
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,
(31:07):
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.
Speaker 2 (31:23):
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.
Speaker 1 (31:35):
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
(31:56):
little bit, but I want to dig a little bit
deeper into it because I want to explain why physics
wants monopoles to exist.
Speaker 2 (32:03):
All right, let's see how many different ways there are
to say we don't know.
Speaker 1 (32:11):
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
(32:34):
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
(32:58):
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
(33:20):
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
(33:41):
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
(34:04):
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
(34:24):
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,
(34:46):
if we saw monopoles.
Speaker 2 (34:48):
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
(35:08):
and when should you not?
Speaker 1 (35:09):
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
(35:31):
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
(35:52):
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
(36:14):
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.
Speaker 2 (36:32):
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?
Speaker 1 (36:42):
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
(37:04):
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.
Speaker 2 (37:15):
Oh wow.
Speaker 1 (37:16):
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.
Speaker 2 (37:22):
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,
(37:52):
you were about to tell us how we go about
looking for monopoles. So what have we done so far?
Speaker 1 (37:57):
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
(38:19):
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
(38:39):
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
(39:00):
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
(39:22):
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.
Speaker 2 (39:31):
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.
Speaker 1 (39:41):
Yeah, exactly.
Speaker 2 (39:43):
Wow.
Speaker 1 (39:43):
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.
(40:03):
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.
(40:24):
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.
Speaker 2 (40:40):
How long have we been using this method to look
for monopoles.
Speaker 1 (40:43):
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
(41:06):
be an amazing discovery, but we've never seen one, and
so maybe the universe just is asymmetric in this way.
Speaker 2 (41:12):
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.
Speaker 1 (41:24):
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
(41:46):
one in which they were prohibited and which they just
cannot exist for some reason we don't yet know.
Speaker 2 (41:52):
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?
Speaker 1 (42:09):
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?
Speaker 2 (42:14):
Yeah, I mean I don't think the magnetars and I
would feel really comfortable on Mars. You know, we need
a strong diepole.
Speaker 1 (42:21):
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
(42:44):
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,
(43:06):
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.
Speaker 2 (43:24):
And is it changing because convection can be sort of
like random, and it's not always happening exactly the same way.
Speaker 1 (43:31):
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
(43:52):
in time a million years, the compass would point north
towards the south pole.
Speaker 2 (43:56):
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.
Speaker 1 (44:05):
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.
Speaker 2 (44:23):
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.
Speaker 1 (44:29):
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
(44:52):
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
(45:14):
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?
Speaker 2 (45:30):
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.
Speaker 1 (45:40):
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
(46:00):
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
(46:20):
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.
Speaker 2 (46:31):
So a little bit of magic left to demystify, all.
Speaker 1 (46:35):
Right, Kelly, So are magnetic fields still magic to you?
Speaker 3 (46:38):
You know?
Speaker 2 (46:38):
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.
Speaker 1 (46:59):
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.
Speaker 6 (47:07):
Me too.
Speaker 2 (47:08):
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.
Speaker 1 (47:17):
Well, thanks to everyone for writing in with your questions
about magnetism, and stay tuned for new episodes.
Speaker 2 (47:22):
Thanks Meglow's Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio.
We would love to hear from you, We really would.
Speaker 1 (47:37):
We want to know what questions you have about this
Extraordinary Universe.
Speaker 2 (47:42):
We want to know your thoughts on recent shows, suggestions
for future shows. If you contact us, we will get
back to you.
Speaker 1 (47:48):
We really mean it. We answer every message, email us
at Questions at Danielankelly.
Speaker 2 (47:54):
Dot org, or you can find us on social media.
We have accounts on x, Instagram, Blue Scott and on
all of those platforms. You can find us at D
and K Universe.
Speaker 1 (48:04):
Don't be shy write to us
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
(00:31):
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
(00:52):
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.
Speaker 2 (01:23):
Hello, I'm Kelly Windersmith. I study parasites and space and magnets. Man,
how do they work? What a miracle magnets are Hi.
Speaker 1 (01:32):
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.
Speaker 2 (01:41):
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.
Speaker 1 (01:56):
And are you saying they're magicians.
Speaker 2 (02:00):
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
(02:21):
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.
(02:41):
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.
Speaker 1 (02:48):
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,
(03:09):
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
(03:32):
little bit beyond physics, don't they.
Speaker 2 (03:34):
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.
Speaker 1 (03:54):
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
(04:16):
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.
Speaker 2 (04:30):
Our apologies to the Jugglers for demystifying the magic of magnets.
Speaker 1 (04:36):
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.
Speaker 3 (04:57):
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.
Speaker 4 (05:13):
Historically, I wonder if magnetism is one of the earliest
to perceive intersections between magic and science.
Speaker 2 (05:19):
It's a mystery why Magnet and Steel was Walter Egan's
only hit, because that's a great song.
Speaker 4 (05:25):
I can get more magnets by breaking one into pieces.
Speaker 1 (05:29):
Total mystery.
Speaker 5 (05:31):
Spin creates it, but spin isn't really spinning, is it?
Speaker 4 (05:34):
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.
Speaker 3 (05:45):
How magnets can attract and repul without touching.
Speaker 1 (05:48):
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?
Speaker 6 (06:00):
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.
Speaker 3 (06:10):
I think is the fact that the north and south
pull switch and we don't know why or like what
causes it?
Speaker 2 (06:16):
All right, Daniel, magnets, how do they work?
Speaker 1 (06:21):
I don't know. It sounds like we should invite Walter
Egan to sing us his song.
Speaker 2 (06:24):
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.
Speaker 1 (06:38):
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.
Speaker 2 (06:51):
Yeah, me as well. We'll check it out. But then,
how do magnets work, Daniel, Yeah.
Speaker 1 (06:57):
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
(07:18):
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
(07:39):
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
(08:01):
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
(08:22):
and charges.
Speaker 2 (08:23):
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.
Speaker 1 (08:33):
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.
Speaker 2 (08:51):
Okay, so the word monopole refers to one electron alone
or a bunch of electrons together. It can be either
singular or plural elonetrons.
Speaker 1 (09:00):
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.
Speaker 2 (09:20):
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.
Speaker 1 (09:29):
Going down that rabbit hole?
Speaker 2 (09:30):
Here we go, not very far. They are juggalos. Okay,
they are juggalos. Oh got a picture pop brought back
to my youth.
Speaker 1 (09:42):
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.
(10:05):
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
(10:26):
instead of for electricity.
Speaker 2 (10:28):
And so north is plus and south is minus.
Speaker 1 (10:31):
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.
Speaker 2 (10:45):
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?
Speaker 1 (10:56):
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,
(11:18):
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.
(11:39):
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
(12:01):
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.
Speaker 2 (12:22):
Okay, So when I have a magnet, it's because of
stuff electrons and protons are doing in there.
Speaker 1 (12:28):
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
(12:50):
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.
Speaker 2 (13:01):
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.
Speaker 1 (13:07):
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
(13:29):
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.
Speaker 2 (13:39):
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?
Speaker 1 (13:47):
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
(14:08):
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.
(14:29):
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.
(14:50):
So here's David Naylor asking us this question.
Speaker 5 (14:53):
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.
Speaker 2 (15:11):
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?
Speaker 1 (15:21):
Are you inviting David to join your insane magnet posse?
Speaker 2 (15:26):
Yes, the megalows.
Speaker 1 (15:31):
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
(15:52):
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.
(16:13):
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
(16:34):
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
(16:55):
is its own mini magnet.
Speaker 2 (16:57):
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.
Speaker 1 (17:18):
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
(17:39):
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
(18:02):
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.
Speaker 2 (18:18):
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?
Speaker 1 (18:37):
Does that seem like a cozy little neighborhood organization.
Speaker 2 (18:40):
It sounds like they're segregating. I don't like that one.
Speaker 1 (18:42):
Oh no, you're right exactly. Let's mix everybody.
Speaker 5 (18:45):
Yeah.
Speaker 1 (18:45):
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
(19:06):
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
(19:26):
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.
Speaker 2 (19:33):
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.
Speaker 1 (19:38):
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
(19:59):
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
(20:21):
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.
Speaker 2 (20:33):
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.
Speaker 1 (20:49):
I don't know, the Brave Little Toaster. I got a
lot of cultural homework to do after this episode.
Speaker 2 (20:54):
We were born in the wrong decade, man.
Speaker 1 (20:55):
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
(21:17):
or on or reverse.
Speaker 2 (21:19):
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.
Speaker 1 (21:39):
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
(22:01):
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.
Speaker 2 (22:17):
All right, Well, let's take a break and get more
into that. All right, So my brain is stuck on
(22:40):
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.
Speaker 1 (22:47):
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
(23:10):
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
(23:32):
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.
Speaker 2 (23:53):
What kind of things in our lives use electric motors?
Speaker 1 (23:57):
Evs, Oh, yes, what.
Speaker 2 (23:59):
About my hybrid? Does my hybrid use an electric motor?
Speaker 1 (24:02):
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
(24:25):
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?
Speaker 2 (24:43):
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.
Speaker 1 (24:59):
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,
(25:22):
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.
Speaker 2 (25:42):
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?
Speaker 1 (25:50):
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.
Speaker 2 (26:12):
Yeah, I'm fascinated. So what is the biggest magnet? Who
is the current a monarch of the magalows?
Speaker 1 (26:19):
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,
(26:43):
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
(27:07):
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
(27:29):
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.
Speaker 6 (27:51):
Yay.
Speaker 2 (27:51):
Why didn't you come up with that sooner? Daniel? This
is what you do, man.
Speaker 1 (27:57):
I wanted to lead into it a little bit.
Speaker 2 (27:59):
More you're good at this, yes, yes.
Speaker 1 (28:01):
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
(28:22):
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.
Speaker 2 (28:31):
So that's what ten tesla less than what bitter was doing,
Is that right now?
Speaker 6 (28:35):
Yeah?
Speaker 1 (28:35):
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
(28:56):
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.
Speaker 2 (29:17):
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.
Speaker 1 (29:39):
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
(30:00):
detailed geometry of bitter magnets.
Speaker 2 (30:03):
Awesome, Okay, thanks, Now let's blow some stuff up.
Speaker 1 (30:05):
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
(30:25):
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.
Speaker 3 (30:34):
Yeah.
Speaker 2 (30:35):
I can't imagine you're going to get a government to
fund an LHC that runs on explosive magnets, you know.
Speaker 1 (30:40):
Oh that would be cool though, Yeah, be cool.
Speaker 2 (30:42):
Every decade you get one really big batch of data
and then you got to start over again.
Speaker 1 (30:46):
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,
(31:07):
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.
Speaker 2 (31:23):
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.
Speaker 1 (31:35):
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
(31:56):
little bit, but I want to dig a little bit
deeper into it because I want to explain why physics
wants monopoles to exist.
Speaker 2 (32:03):
All right, let's see how many different ways there are
to say we don't know.
Speaker 1 (32:11):
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
(32:34):
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
(32:58):
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
(33:20):
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
(33:41):
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
(34:04):
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
(34:24):
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,
(34:46):
if we saw monopoles.
Speaker 2 (34:48):
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
(35:08):
and when should you not?
Speaker 1 (35:09):
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
(35:31):
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
(35:52):
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
(36:14):
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.
Speaker 2 (36:32):
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?
Speaker 1 (36:42):
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
(37:04):
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.
Speaker 2 (37:15):
Oh wow.
Speaker 1 (37:16):
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.
Speaker 2 (37:22):
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,
(37:52):
you were about to tell us how we go about
looking for monopoles. So what have we done so far?
Speaker 1 (37:57):
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
(38:19):
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
(38:39):
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
(39:00):
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
(39:22):
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.
Speaker 2 (39:31):
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.
Speaker 1 (39:41):
Yeah, exactly.
Speaker 2 (39:43):
Wow.
Speaker 1 (39:43):
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.
(40:03):
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.
(40:24):
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.
Speaker 2 (40:40):
How long have we been using this method to look
for monopoles.
Speaker 1 (40:43):
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
(41:06):
be an amazing discovery, but we've never seen one, and
so maybe the universe just is asymmetric in this way.
Speaker 2 (41:12):
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.
Speaker 1 (41:24):
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
(41:46):
one in which they were prohibited and which they just
cannot exist for some reason we don't yet know.
Speaker 2 (41:52):
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?
Speaker 1 (42:09):
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?
Speaker 2 (42:14):
Yeah, I mean I don't think the magnetars and I
would feel really comfortable on Mars. You know, we need
a strong diepole.
Speaker 1 (42:21):
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
(42:44):
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,
(43:06):
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.
Speaker 2 (43:24):
And is it changing because convection can be sort of
like random, and it's not always happening exactly the same way.
Speaker 1 (43:31):
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
(43:52):
in time a million years, the compass would point north
towards the south pole.
Speaker 2 (43:56):
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.
Speaker 1 (44:05):
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.
Speaker 2 (44:23):
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.
Speaker 1 (44:29):
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
(44:52):
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
(45:14):
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?
Speaker 2 (45:30):
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.
Speaker 1 (45:40):
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
(46:00):
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
(46:20):
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.
Speaker 2 (46:31):
So a little bit of magic left to demystify, all.
Speaker 1 (46:35):
Right, Kelly, So are magnetic fields still magic to you?
Speaker 3 (46:38):
You know?
Speaker 2 (46:38):
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.
Speaker 1 (46:59):
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.
Speaker 6 (47:07):
Me too.
Speaker 2 (47:08):
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.
Speaker 1 (47:17):
Well, thanks to everyone for writing in with your questions
about magnetism, and stay tuned for new episodes.
Speaker 2 (47:22):
Thanks Meglow's Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio.
We would love to hear from you, We really would.
Speaker 1 (47:37):
We want to know what questions you have about this
Extraordinary Universe.
Speaker 2 (47:42):
We want to know your thoughts on recent shows, suggestions
for future shows. If you contact us, we will get
back to you.
Speaker 1 (47:48):
We really mean it. We answer every message, email us
at Questions at Danielankelly.
Speaker 2 (47:54):
Dot org, or you can find us on social media.
We have accounts on x, Instagram, Blue Scott and on
all of those platforms. You can find us at D
and K Universe.
Speaker 1 (48:04):
Don't be shy write to us
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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