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EMILY KWONG, HOST:
Hey, everybody. Emily Kwong here. Today we're going back to school, where we revisit something you may have learned in science class and go a bit deeper with it. Joining me in this is science correspondent Geoff Brumfiel.
GEOFF BRUMFIEL, BYLINE: And today, Emily, I've got a good one for you. It's one of the most mysterious forces in the world, but you can find it on your fridge. I'm talking about magnets and magnetism, which is a fundamental force of nature. It can feel a little bit like magic.
BRUMFIEL: But how it works is really interesting. And I'm going to tell you something else. We all should know how magnets work, Emily, because magnets matter.
CARLOS VILLA: There are magnets in the TV. We wouldn't be able to hear our favorite TV shows without magnets. Our clocks and watches would not function without magnets. Our computers. Most of the...
BRUMFIEL: Carlos Villa is a magnet evangelist. Once you get him started, it's hard to get him to stop (laughter).
VILLA: Just holding the phone up to your ear, there's a couple of magnets in your phone. Everybody that's listening to this podcast right now is using magnets to listen to that podcast.
VILLA: So magnets are essential to everything we do, and we don't stop to think about it.
BRUMFIEL: But we will think about it today.
KWONG: I am so excited. I had no idea. All right.
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KWONG: Today on the show, magnetism - how does it work? And are magnets good for more than just your fridge?
BRUMFIEL: Don't let Carlos hear you talking about magnets like that.
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KWONG: OK. Geoff Brumfiel, where does our journey into the world of magnetism begin?
BRUMFIEL: It begins with a call to Carlos and a guy named Tim Murphy.
BRUMFIEL: They both work at the National High Magnetic Field Laboratory in Tallahassee, Fla.
Normally, you know, I do research, and I learn about things. But this time I just brought some bar magnets. I thought I would let you guys - (laughter).
TIM MURPHY: Well, I mean, that's all we do here. So they just - you know, they're bigger, and they give us money for it. So...
VILLA: More expensive, too.
MURPHY: Yeah. And they're painted. We paint them.
KWONG: (Laughter) They're so ready for this interview.
BRUMFIEL: (Laughter) They were born ready for this interview.
BRUMFIEL: These folks work with magnets all day long. Carlos heads the K-12 education programs for the lab. Tim is a physicist there. And like Carlos was saying earlier, they really feel like magnets need respect.
VILLA: I guarantee you that whatever direction you're looking in right now, unless you're in the wilderness right now, there's probably a magnet in your line of sight, and you just don't know it.
MURPHY: Well, and if you're in the wilderness, you're standing on the biggest magnet that we have, which is the Earth.
BRUMFIEL: The Earth is a giant magnet, with a North Pole and a South Pole. And where that magnetism comes from is kind of complicated. So for today, we're just going to stick to smaller magnets, like the ones we use in our daily lives.
KWONG: OK. Geoff, I'll be honest - I don't really know what makes a magnetic field a magnetic field. So how would you describe that?
BRUMFIEL: (Laughter) Which is kind of fascinating because you've turned yourself into the sort of SHORT WAVE physics geek.
KWONG: There's gaps in my knowledge. Fill the gap. What is a magnetic field exactly?
BRUMFIEL: (Laughter) Well, so magnetic fields, like I just said, you know, based on the Earth's field, actually, they're often said to have a North and South Pole.
BRUMFIEL: And opposite poles attract, and like poles repel. So magnets can pull each other together or push each other apart. And actually, magnetism itself is half of a fundamental force called electromagnetism, which also includes electric fields. But what I think is really fascinating is, aside from gravity, magnets are, really, the only fundamental force that we can just experience and encounter on a regular basis.
KWONG: Right. And we can kind of see this magnetism in action when we're playing around with magnets and they stick to certain metals, right?
BRUMFIEL: Yeah, yeah. I mean, the whole metal-magnet thing is kind of complicated. Carlos will tell you that.
VILLA: Everybody comes up - and I see on TV shows all the time, even the education TV shows - they say, magnets stick to metal. And I'm like, no, you got it wrong again.
VILLA: There's only three metals that are naturally magnetic. That's iron, nickel and cobalt.
BRUMFIEL: And what Carlos means there is that there are only three metals that can be permanent magnets that hold their magnetism forever and ever. Other metals can stick to magnets. But then there are a lot of metals that can't. So we just moved to a new house that has a stainless steel fridge. And guess what? Like, all our fridge magnets don't work on this fridge anymore.
KWONG: So what makes some materials magnetic and others not so much?
BRUMFIEL: Well, it actually all has to do with electrons.
KWONG: Oh, our friends, the electrons - of course. These are the negatively charged particles and atoms, and when they flow, they create electricity.
BRUMFIEL: That's right. And whenever electrons move and in particular when they spin around something, they generate a magnetic field as well as an electric field.
KWONG: So magnetic fields have to do with spinning electrons.
BRUMFIEL: Exactly. So the electrons are spinning around the atom, and that makes, like, a little magnetic field. But then in a permanent magnet, what happens is all the atoms are facing in the same direction.
MURPHY: Imagine all these atoms lined up in a row, and they kind of want to do what their next neighbor is doing. So if their neighbor is pointed up - right? - their magnetic moment is up, then the one next to him says, hey, up is the direction. So they go up as well. So now you end up with a macroscopic magnetic field because all of these atoms are kind of lined up with their magnetic moments.
KWONG: Oh. So all of these atoms facing the same direction is what creates one big magnet.
BRUMFIEL: Exactly. That's how permanent magnets work. Like, the magnets that stick to your fridge, all the atoms in that magnet are lined up in the same way, and they make this big magnetic field that pulls the magnet against your fridge and keeps it there. But then there's another kind of magnet. And Tim, the guy you just heard there, he actually works with this one. It's called an electromagnet.
MURPHY: For electromagnets, we actually don't care about the spin of the electron. What we care about is the motion of the electrons.
BRUMFIEL: So what they do is send electrons through wires as electrical current, but then they coil the wire, like a phone cord.
KWONG: And because the wire is coiled, the electrons will kind of naturally spin around, and the spinning electrons can make a strong magnetic field. Is that it?
BRUMFIEL: That's exactly right. And Tim's electromagnets, when they've got electricity flowing through them, are really, really powerful. So magnetism is measured in tesla, which is not just a car; it's a unit of measurement. And 45 tesla is what these magnets can pull, and that's about 1 million times as powerful as Earth's magnetic field.
BRUMFIEL: So to give you a sense of how strong a 45 tesla magnet is...
BRUMFIEL: ...Tim was walking by it one day when his butt started to heat up.
KWONG: (Laughter) What?
MURPHY: And I was like, what is going on? So I walk away from the magnet, reach back there, and it's my phone. And the magnetic field had opened all the electrical relays in the phone, so the battery was just putting out 100% and was on its way to catching fire. So I almost ended up with a flaming rear end because of the 45 T.
KWONG: (Laughter) That is some serious magnetic power there.
BRUMFIEL: (Laughter) It is.
KWONG: Be careful what you put in your pocket.
BRUMFIEL: You know, I actually, when I was an undergrad, worked at a powerful magnet. And there were lines painted on the floor. You were not supposed to bring your phone or screwdriver or anything past that line because it could do real damage. So it's a serious issue.
KWONG: Fascinating. So to recap, magnets are just objects that produce a magnetic field. And that's either because of the way their atoms are arranged or, I'm learning, because of electrical currents going through them. But why is there a whole national lab devoted to studying magnets?
BRUMFIEL: Well, it's a good question. And what it comes down to is that every atom on the planet can respond to magnetism. Atoms are made of electrons and, their counterparts, protons, which are these positively charged particles that sit at the center of an atom. And both electrons and protons can move in magnetic fields if those magnetic fields are large enough.
VILLA: I've learned from being at the lab that every material will react in some way, shape or form if the field is strong enough, and we are able to make the field strong enough.
BRUMFIEL: So at the National High Magnetic Field Laboratory, what they do is they basically stick all sorts of different materials and objects into magnetic fields and measure their response. And Carlos will tell you, basically, you can use magnets in almost any other scientific field you can think of.
VILLA: It really is almost limitless. I've seen paleontology, oceanography, psychology. I've seen a little bit of everything done at the lab since I've been there.
BRUMFIEL: And actually, beyond the laboratory, there's this huge medical application, if you've ever had an MRI.
KWONG: Oh, yeah, of course. MRI - magnetic resonance imaging.
BRUMFIEL: That's right. And so what's going on there is your body is actually being poked with a huge magnetic field. And by measuring how the atoms in your body line up, doctors can build a picture of what's going on inside.
KWONG: Very cool. And how about everyday uses of magnets, beyond putting postcards on your fridge?
BRUMFIEL: O-M-G. Emily...
MURPHY: Just to chime in with Carlos...
BRUMFIEL: Do not get them started again. Tim will talk your ear off just about the magnets in, say, your car.
MURPHY: You think, oh, there's not many magnets here. But you have a starter. That needs magnets. You have an alternator. That needs magnets. You have an air conditioner with magnets. Your transmission uses magnets to change gears and to engage gears. You say, well, I have an electric car. Lovely. But the way you move your wheels are electric motors, which use magnets. So they're everywhere.
KWONG: What a thesis statement. It's magnets.
BRUMFIEL: It's magnets. It's always magnets. And actually, like, even the way we're talking right now, OK, with microphones and speakers, all of this uses magnets.
BRUMFIEL: So a speaker is a magnet inside of a coil of wire, and the electric current runs through the coil, makes a magnetic field, which moves the magnet, which creates sound waves through vibration. A microphone's kind of the same thing backwards. Like, my voice is moving a little magnet in a microphone that then creates an electrical current in a coil, and so that electrical signal can then be recorded somewhere else.
KWONG: Right. That's why it's called electromagnetism.
BRUMFIEL: It is. It is. And, you know, I mean, if you're really trying to sort of take a step back and understand it, I think the way I kind of get my head around it is, like, magnets are very good at moving things in the real world, right? The magnetic field can actually manipulate things. But it's all tied up with electrical signals as well, electrons moving, and so it's a great way to take electricity and turn it into real motion or work in the real world. And I think that's why magnets are everywhere.
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KWONG: Well, Geoff, from my magnetic microphone to yours, thank you so much for bringing this information. It was really interesting.
BRUMFIEL: Oh, it's been my pleasure, Emily.
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KWONG: This episode was produced by Rebecca Ramirez, edited by Gisele Grayson and fact-checked by Rasha Aridi. The audio engineer for this episode was Patrick Boyd. I'm Emily Kwong. You're listening to SHORT WAVE, the daily science podcast from NPR.
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