Speaker 1: Or Hey, I know you like to joke that any
Speaker 1: physics question I ask you could be answered with the
Speaker 1: Big Bang. I think it's a pretty solid answer for
Speaker 1: any science question, you know, like why does why does
Speaker 1: this happen? And it's all because of the Big Bang? Man,
Speaker 1: you are like a deep philosopher of science. Sometimes I
Speaker 1: think I just just heard you say the Big Bang
Speaker 1: too many times. Well, I don't mean to burst your bubble,
Speaker 1: but I think I finally found a question where the
Speaker 1: Big Bang is not the valid answer. What could not
Speaker 1: be due to the Big Bang? Keep listening. Hi, am
Speaker 1: orhammy cartoonists and the creator of PhD comics. Hi. I'm
Speaker 1: Daniel Whitson. I'm a particle physicist, and I owe my
Speaker 1: existence to the Big Bang, as do we all, as
Speaker 1: does this podcast. That's right, even this podcast so Welcome
Speaker 1: to Daniel and Jorge Explain the Universe, a production of
Speaker 1: My Heart Radio. Welcome to our podcast, in which we
Speaker 1: explore things big and small, things out there, big and small,
Speaker 1: out there in the universe, and even right here in
Speaker 1: our homes, in our everyday lives. Something that we use
Speaker 1: almost too much. I think perhaps that's right. One of
Speaker 1: the joys of being a physicist is looking around you
Speaker 1: all the time and wondering how does that thing work?
Speaker 1: And that extends to the cosmos and the stars and
Speaker 1: the big question to the universe, but it also applies
Speaker 1: to just stuff happening around you. You know, why does
Speaker 1: that leaf dance that way? Why does the ball bounce
Speaker 1: this way? How do I make this thing happen? Or
Speaker 1: how does this thing in my kitchen do it's thing?
Speaker 1: How does this magic happen? There's crazy physics all around us, right,
Speaker 1: and potentially dangerous sources of radiation in our own homes.
Speaker 1: That's right. Basically the whole universe is crazy physics. I mean,
Speaker 1: that's a good way to summarize the whole thing, right.
Speaker 1: That's a that's an alternate answer to the Big Bang?
Speaker 1: Why why does why does this particle do that? It's
Speaker 1: just crazy physics. It's better than the answer being crazy physicists. Right,
Speaker 1: physicists crazy because of crazy physics. I'm not sure about
Speaker 1: the cause and effect there, Yeah, um, it might be
Speaker 1: the becoming a physicist makes you a little bit crazy
Speaker 1: because you see the world through different eyes. Right, everything
Speaker 1: you look at you try to understand in terms of
Speaker 1: an equation or model, or try to dig down and
Speaker 1: understand how this emergent phenomenon can be explained by tiny
Speaker 1: little particles bumping up against each other. Yeah. So on
Speaker 1: this podcast we usually tackle very big topics like the
Speaker 1: size of the universe or where did the Big band
Speaker 1: come from? But sometimes we like to tackle smaller topics
Speaker 1: or topics that are in everyone's everyday life. Yeah, So
Speaker 1: to be on the podcast, we'll be tackling something that
Speaker 1: everyone has in their kitchens. So today on the program,
Speaker 1: we'll be asking the question how does a microwave work?
Speaker 1: Where I guess more specifically, how does a microwave oven work?
Speaker 1: You know what a microwave is. You put the stuff
Speaker 1: in there, you press the button, It spins, it beeps,
Speaker 1: it turns around, and it comes out hot. Right, But
Speaker 1: how does that actually happen? What's the physics that's going
Speaker 1: on there? Yeah? How do microwaves work? I mean, we've
Speaker 1: had them around for a long time. It seems right
Speaker 1: to heat up our foods are in our snacks, in
Speaker 1: our hot pockets. They first appeared in kitchens in the
Speaker 1: late fifties, I think, so it's been decades. Hatties around
Speaker 1: for a while, Yeah, And like many useful inventions, they
Speaker 1: were discovered by accident. They were discovered by a physicist
Speaker 1: poking around trying to do one thing, discovered something else useful,
Speaker 1: another way to save time. Right, for a lot of people,
Speaker 1: it's sort of it's sort of a convenience appliance. Like
Speaker 1: if you were to heat things up in the regular oven,
Speaker 1: it would just it would take much longer, but in
Speaker 1: a microwave, things seem to get hot really fast. Yeah,
Speaker 1: and you know, I don't want to take any of
Speaker 1: this the em out of this this podcast episode, but
Speaker 1: I'll admit that the microwave in our kitchen at home
Speaker 1: has been broken for about five years. And yeah, it's
Speaker 1: built into the double oven thing we have, so to
Speaker 1: get repaired, we have to replace the whole thing. So
Speaker 1: we just sort of put it off forever. And the
Speaker 1: truth is we haven't really missed it or never really noticed.
Speaker 1: You've lived without a microwave for five years. It is possible, people,
Speaker 1: you can live with that a microwave. Yes, it turns
Speaker 1: out you can make popcorn on the stove. So what
Speaker 1: do you use it for? It is like a storage
Speaker 1: You store some pots and dance in it or did
Speaker 1: you clean Did you clean it before you abandoned it?
Speaker 1: I wonder if you open this now, it's never been cleaned. No,
Speaker 1: you know our pet rats like to hang out in there. Um, okay,
Speaker 1: we don't use it for anything. It just uses up
Speaker 1: space in the kitchen. Wow, So you don't use a
Speaker 1: marc So if you have to heat up a quick thing,
Speaker 1: you just what do you do? You eat it cold? No,
Speaker 1: we got a toaster oven, We got an electric water kettle,
Speaker 1: We got a stove top that serves for mostly everything. Yeah,
Speaker 1: it turns out life is possible without a microwave. But
Speaker 1: it's a fascinating object in so many people's kitchen, and
Speaker 1: lots of people swear by it, so I thought it'd
Speaker 1: be interesting to dig into the physics of it. It
Speaker 1: turns out that very few people know how microwave works,
Speaker 1: and the people who think they know how microwave works
Speaker 1: probably have it wrong. Yeah. I was reading through these
Speaker 1: notes and I realized I have no idea how a
Speaker 1: microwave oven works. Or I thought I did, but it
Speaker 1: turns out that I that I don't, And so that
Speaker 1: sort of brings up an interesting question, like there's so
Speaker 1: many people out there who use a microwave. Almost nobody
Speaker 1: knows how it works. How come nobody seems to have
Speaker 1: spent any time thinking about it or wondering about it.
Speaker 1: Is it just physicists who want to understand, like how
Speaker 1: this stuff around us worked, and everybody else is sort
Speaker 1: of happy to just press a button and get their popcorn.
Speaker 1: I wonder if it's a generational thing. You know, at
Speaker 1: this point, most people grew up with the microwave. You know,
Speaker 1: it's sort of like, um, it's just there. It's like
Speaker 1: nobody sits around wondering how a refrigerator works or how
Speaker 1: a pencil works. You know. I think my kids ask
Speaker 1: me how refrigerators work. I want to know how things
Speaker 1: work that existed in the universe before I came to be.
Speaker 1: I'm not like big Bank. That's old news. I'm only
Speaker 1: interested in the news stuff. It's not trending, the big Bang,
Speaker 1: it's not trending. I don't care. So it's something that
Speaker 1: everyone is probably familiar with, and maybe most people own.
Speaker 1: But we were wondering how many people out there and
Speaker 1: know how a microwave actually works. That's right. So I
Speaker 1: walked around the streets of Aspen, Colorado, a place where
Speaker 1: people come from all over the world, with all sorts
Speaker 1: of different backgrounds. And I asked folks if they knew
Speaker 1: how a microwave work. The most people in Aspen, Colorado
Speaker 1: own multiple microwaves. They probably own multiple microwave companies, That's
Speaker 1: what I mean. And they say, I don't care as
Speaker 1: long as the share price keeps going up. Yeah, So
Speaker 1: I think about it for a second. If you were
Speaker 1: skiing out there and askm in Colorado and then a
Speaker 1: scruffy physicist asked you, hey, how does the microwave work?
Speaker 1: What do you think you would answer? Here's what people
Speaker 1: had to say, best guess microwaves electricity fastened through food. No,
Speaker 1: electricity turned into something genetically modifies your food? Yeah, has
Speaker 1: right onto, right on too? And how does that eat
Speaker 1: up your food? The moistation of food is what calls
Speaker 1: the uh yes electricity, the Mormon quality. Can you find
Speaker 1: that jet English? Something around electricity coming down in waves?
Speaker 1: You say, start and then what happens microwaves? No, I
Speaker 1: do not know. Do you know how a microwave works?
Speaker 1: I do, Oh, how it works? Maybe not? We pressed
Speaker 1: plus through a second bottom then start, all right. It
Speaker 1: seems that those microwaves company owners in Asthment don't really
Speaker 1: have much of an idea of how they work. Well,
Speaker 1: I was amazed at the huge variety of answers. I mean,
Speaker 1: we got radiation, we got genetic modification to the foods um.
Speaker 1: There's that one guy who seemed to understand how microwave worked,
Speaker 1: but he could only explain it in Japanese to his wife. Well,
Speaker 1: that's the same with me. I I know how it works,
Speaker 1: but I only know how it works in Japan. I
Speaker 1: like the guy who said, how does the microwave work?
Speaker 1: You just press the start button. That's how it works, right,
Speaker 1: I know. Like I was asking for tips, like help,
Speaker 1: I need to use the microwave and I don't know
Speaker 1: how it works. Please give me tell me my food
Speaker 1: is cold, Like I'm out here on the street with
Speaker 1: my recorder looking for tech support from my microwave. Well
Speaker 1: he would have been helpful. Yeah, yeah, and uh, and
Speaker 1: you know, and you heard a couple of people say
Speaker 1: what I think is a common trope, which is that
Speaker 1: the microwave heats up the water, right, which I think
Speaker 1: is a common misunderstanding. We'll get into it later, but
Speaker 1: that's not how a microwave works, right, Yeah, that's what
Speaker 1: I thought too. And also some people said it has
Speaker 1: with electricity, like somehow it uses electricity to zap your food. Yeah,
Speaker 1: and you know it does use electricity. It's not like
Speaker 1: it's a coal powered microwave or something steampunk steampunk microwave,
Speaker 1: like you have all the steam, but you converted to microwaves. Yeah,
Speaker 1: somebody out there probably has done that, you know. On
Speaker 1: a recent episode about gravitons, I wondered out loud what
Speaker 1: a gravitron was, and that moment in our podcast I
Speaker 1: think might have generated the most listener response because I
Speaker 1: got dozens of emails from people who had written in
Speaker 1: their childhood a gravitron an amusement park ride. So that
Speaker 1: generated the most the most emails of anything we've ever
Speaker 1: done so far. Actually know that, because that was on
Speaker 1: the latest season of Stranger Things. Yes, you're right, there
Speaker 1: was a scene in the gravitron Um. So if anybody
Speaker 1: out there knows of a coal powered microwave, please right
Speaker 1: in and say, d as a picture. I'd love to
Speaker 1: see it. Well, so, um, not a people. A lot
Speaker 1: of people know how a microwave works, and I didn't
Speaker 1: know apparently how a microwave works, so let's get into it.
Speaker 1: But maybe first what you talked about how normal ovens work,
Speaker 1: like the ones with gas or the ones that are electric,
Speaker 1: not the microwave kind. So a normal oven basically works
Speaker 1: by heating the air inside the oven, and then the
Speaker 1: air heats your food, right, And that's you'll notice this
Speaker 1: because if you open a normal oven, you get like
Speaker 1: a rush of hot air that comes out and burns
Speaker 1: your face, right, Whereas if you open a microwave, you
Speaker 1: don't notice that. In a regular oven, you you rely
Speaker 1: you like, you put the energy into the air, and
Speaker 1: then you rely on the air to give the energy
Speaker 1: to your food. That's right. And remember, on a microscopic level,
Speaker 1: what's happening is that the air is heating up, and
Speaker 1: that means that the air molecules are getting faster. Right.
Speaker 1: We talked about temperature in another episode. Sort of crazy concept,
Speaker 1: but the simplest idea is that you're just speeding up
Speaker 1: the air molecules, so they're zooming around faster and faster
Speaker 1: inside the oven, and sometimes they bounce into your food
Speaker 1: and they deposit some energy, so they heat up the
Speaker 1: molecules in your food. Right, maybe your oven is gas
Speaker 1: and his little flames or it has heating element if
Speaker 1: it's an electric oven, and that heats up the air, right,
Speaker 1: which speeds up those molecules, and they bounce into the
Speaker 1: molecules of your food and heat them up. Yeah, when
Speaker 1: you put it like that, it seems really inefficient to
Speaker 1: think about ovens like that. The air and then the
Speaker 1: air you have to wait for the air to bump
Speaker 1: into your food, and then it only bumts into the surface, right,
Speaker 1: the outer skin of your food. So that's why it
Speaker 1: takes a while to heat up in a regular oven,
Speaker 1: that's right. And they're super inefficient in my house because
Speaker 1: every time I'm baking something, somebody will walk by the
Speaker 1: oven every five minutes and open it up. What's in there,
Speaker 1: and then all the hot air rushes out and you've
Speaker 1: got to heat up the whole oven again. I'm surprised
Speaker 1: you're a regular oven works, Daniel. I'm gonna put a
Speaker 1: lock on it or something. But yeah, that's over camp
Speaker 1: fire every night. That things exactly why. Um, that's exactly
Speaker 1: why the food in your oven heats from the outside
Speaker 1: in because the outside is the only part exposed to
Speaker 1: the air. Right, So the outside of your food, the
Speaker 1: outside layer gets heated by the air, and the inside
Speaker 1: gets heated by the outside. Like you're cooking the turkey,
Speaker 1: the skin gets hot first, and then the heat of
Speaker 1: the skin cooks the next layer, and that layer cooks
Speaker 1: the next layer, and that layer cooks the next layer.
Speaker 1: So it's sort of like heat propagating through the turkey,
Speaker 1: but has to start from the outside. That's the hottest part, right,
Speaker 1: And that's kind of then that's kind of good sometimes
Speaker 1: because that's where you get you know, crunchy crusts. Yeah, exactly,
Speaker 1: you get this browning effect from the hot air, and
Speaker 1: that's because the air can get to a sort of
Speaker 1: a high enough temperature to be like caramelization, and that
Speaker 1: gives you the good browning stuff. And you know, sometimes
Speaker 1: you want that. You want the outside to be crunchier
Speaker 1: and hotter than the inside. Like for a turkey, you
Speaker 1: don't want the breast meat to get up to a
Speaker 1: certain temperature because then it gets dry, but you do
Speaker 1: want the outside of a higher temperature. So for things
Speaker 1: where you want the outside hotter and the inside a
Speaker 1: little bit cooler, a convection of it is perfect, Okay,
Speaker 1: So it doesn't sound super efficient, but it's an old,
Speaker 1: old timey trusted technology we've been doing. We've been using
Speaker 1: ovens for thousands and thousands of years. It doesn't break down,
Speaker 1: that's right. I mean in the old days, before we
Speaker 1: had gas ovens and electric ovens, an oven it was
Speaker 1: just like an enclosed space with a bunch of burning
Speaker 1: wood in it. Right, And people still do that, like
Speaker 1: a pizza oven. Right, you can get up to eight
Speaker 1: hundred degrees or nine degrees, and you see these things,
Speaker 1: they're just like they got wood burning in the back.
Speaker 1: And it's just an enclosed space to trap the heat.
Speaker 1: Because if you have a fire without walls around it,
Speaker 1: then the heat just rises and you can cook over it,
Speaker 1: but it's much less efficient. So you just enclose it
Speaker 1: to sort of capture the heat um where you are.
Speaker 1: And that's that's an oven. That's all an oven is
Speaker 1: is a heat source and something to capture it to
Speaker 1: the air stays hot. All right, that's how normal ovens work.
Speaker 1: So let's get into microwaves. But first let's take a
Speaker 1: quick break. All right, we're talking about microwave ovens and
Speaker 1: how they work. So Daniel break it down for us
Speaker 1: how does a microwave oven work? Well, maybe we first
Speaker 1: we should figure out we should talk about what a
Speaker 1: microwave is, right, Like, what is this thing? We tackled
Speaker 1: the word oven, now we're tackling the word microve waves. Right,
Speaker 1: but first let's break it that into micro m wave.
Speaker 1: What is the letter N really means? What is letter I?
Speaker 1: Three hours later we'll get to the answer. It's pretty simple. Actually,
Speaker 1: a microwave is just a kind of light. Right. Remember
Speaker 1: that all these things gamma rays, X rays, UV light,
Speaker 1: visible light, um, radio waves, these are all just parts
Speaker 1: of the electro magnetic spectrum. It's not like a special
Speaker 1: kind of ray or a special kind of particle, or
Speaker 1: you know, laser is just plan o light. It's just
Speaker 1: plain old electromagnetic radiation, right, And a microwave just refers
Speaker 1: to the wavelength of that radiation. So remember, the thing
Speaker 1: that differentiates a gam array from ultraviolet light, from visible light,
Speaker 1: from X rays or radio waves is just the frequency
Speaker 1: of the wiggling. Right. All these things are electromagnetic fields
Speaker 1: oscillating up and down and left and right, and the
Speaker 1: speed at which they oscillate, how many times they oscillate
Speaker 1: per second, right, or equivalently, the wavelength of their oscillation, right,
Speaker 1: how long that wave is UM determines which one it is.
Speaker 1: And so radio waves are the ones with a really
Speaker 1: long wavelengths, Like there are radio waves that have lengths like,
Speaker 1: you know, dozens and dozens of meters. Microwaves. It's sort
Speaker 1: of a confusing name because microwaves are radio waves with
Speaker 1: shorter wavelengths, so down about twelve centimeter. But it's only
Speaker 1: shorter compared to radio waves, which have like dozens of
Speaker 1: meters of wavelength. They're not short comparable light visible, they're
Speaker 1: not like nanometers, they're not microscopic, that's right, They're only
Speaker 1: micro compared to really big radio waves. Oh scale thing. Huh.
Speaker 1: But so they're microwaves are actually like megawaves compared to
Speaker 1: like the visible light that we all see every day, yeah,
Speaker 1: which is wavelengths of like hundreds of nanometers, which is tiny, right,
Speaker 1: These things have wavelengths that are in the twelve centimeters.
Speaker 1: That's you know, the size of your hand or something
Speaker 1: like that. So these things have real physical wavelength Wait
Speaker 1: are you telling me that physicists names something in a
Speaker 1: confusing way? What are you telling me that you're surprised
Speaker 1: that physics name would be confusing. Touche touche. Anything named
Speaker 1: in the pre Jorge epoch is defined to be confusing
Speaker 1: because you were not involved. Yeah, yeah, the PJ. We
Speaker 1: don't like to talk about it. You know, it's a
Speaker 1: dark period in the history of physics, but it does exist. Okay,
Speaker 1: so they're they're microwaves, but they're not really micro they're
Speaker 1: actually like, you know, twelve centimeters. It's sort of like
Speaker 1: the length of your hand. Yeah, yeah, exactly, And so
Speaker 1: that's what a microwave is. And then you might wonder, like,
Speaker 1: all right, but you know, how does that heat my food?
Speaker 1: If I shine my flashlight at a turkey, it doesn't
Speaker 1: cook it, right, not, Well, it depends on your flashlight,
Speaker 1: doesn't it. If your flashlight is the large Hadron collider,
Speaker 1: then yeah, maybe, yeah, that's what I mean. It's it's
Speaker 1: it's it's not that the regular light doesn't cook, it's
Speaker 1: just that it doesn't cook as well. Yeah, that's true.
Speaker 1: It does deposits of energy, it just doesn't have that
Speaker 1: much energy on it. But it's essentially the way a
Speaker 1: microwave oven works is that it blasts your food with
Speaker 1: marcro wave radiation, right, which, again, radiation, It sounds scary,
Speaker 1: but it's really just light. Yeah, light is an example
Speaker 1: of radiation. So this is just another kind of electromagnetic radiation.
Speaker 1: And and you might be wondering like, well, okay, why
Speaker 1: does this specific frequency of radiation tend to heat at
Speaker 1: your food? Why is that do that? Right? Well, one
Speaker 1: thing you'll notice is that when you open up a
Speaker 1: microwave oven after you've cooked your food, right, that the
Speaker 1: air inside the microwave oven is not hot. So a
Speaker 1: lot of people think that the way a microwave works
Speaker 1: is that the microwave radiation heats up just the water
Speaker 1: inside the food. Yeah, I've heard, I've heard of that. Yeah,
Speaker 1: Like somehow there's something like it only heats up the
Speaker 1: water molecules, or preferentially the water molecules in your food.
Speaker 1: That's kind of why. I like, if you stick a
Speaker 1: plastic plate, it's not going to heat up as much
Speaker 1: as if you put you know, a hot dog, mhmm.
Speaker 1: And there is some truth to that, right, A microwave
Speaker 1: will heat up some kinds of food more than other
Speaker 1: kinds of food. But the reason that some people give
Speaker 1: is that they think that microwave has like a resonant
Speaker 1: frequency with the water. Remember, microscopically, water is made out
Speaker 1: of molecules, and those molecules can do things like spin
Speaker 1: and vibrate, and like all atomic stuff, it's quantum mechanical,
Speaker 1: which means it can only accept um radiation. It's certain frequencies.
Speaker 1: Like we talked about how atoms can absorb wavelength certain
Speaker 1: wavelengths of light and not other wavelengths of light. So
Speaker 1: some people, I think, imagine that this is what's happening
Speaker 1: instaide your microwave. That water can absorb frequency at this
Speaker 1: wavelength um and the air and the other stuff can't. Right,
Speaker 1: So that's the common misconcept. And when you say resonant
Speaker 1: frequency mean like kind of like a water the idea
Speaker 1: that water has kind of an internal bouncing nous to it, right,
Speaker 1: like an internal m M like frequency. It likes to
Speaker 1: bounce around like a guitar string. Yes, exactly, And it's
Speaker 1: true of every atom, right, they do have special frequencies
Speaker 1: at which they like to vibrate. And it depends on
Speaker 1: the atom and how it's built and how the electrons
Speaker 1: are organized and all that stuff, and so they do
Speaker 1: have special resident frequencies that they do like to absorb radiation.
Speaker 1: But that's not what's happening here. That's not the way
Speaker 1: that the microwave work. It's not it's not definitely not No,
Speaker 1: it's a totally different but really fascinating mechanism. You just
Speaker 1: nuke my brain here, I just reard my start my
Speaker 1: illusion of understanding here. Okay, so it's not making a
Speaker 1: residence with the water, So how is it? But it is?
Speaker 1: It is sort of related to water, right, Like, there's
Speaker 1: something about water molecules that microwaves are kind of specially
Speaker 1: tuned to a heat up. Yeah, and it's a different process.
Speaker 1: It's called dielectric heating. Essentially. It's because water molecules they
Speaker 1: have the same number of positive and negative charges, but
Speaker 1: they're not exactly balanced in the same place, right, which
Speaker 1: means that one part of the water molecule is a
Speaker 1: little more positive and another part is a little more negative.
Speaker 1: So overall there's a little bit of a separation of
Speaker 1: the charges. So what happens when electroc one side of
Speaker 1: water is more optimistic dealing, what's more pessimistic. That's right,
Speaker 1: You got the upside and the downside. Um somewhat some
Speaker 1: water molecules are like the glasses have full of us.
Speaker 1: They have just like this glasses have empty of us.
Speaker 1: It's a big But what happens when electromagnetic waves by,
Speaker 1: Remember electromagnetic waves interact with things that have charge, right,
Speaker 1: negative and positive charge, and so what they do is
Speaker 1: that one part of the molecule gets pushed one way
Speaker 1: and the other part that has the other charge gets
Speaker 1: pushed the other way. You're saying, like a water molecule
Speaker 1: is kind of like a little magnet where one end
Speaker 1: is sort of negative and the other side is positive.
Speaker 1: So it's not like perfectly even, yeah, it's not. It's
Speaker 1: kind of like a magnet in that there are north
Speaker 1: and south, right, But in this case we're talking about
Speaker 1: electric charges and they're positive and negative, and the waves
Speaker 1: come by and they tweak it, and they tweak it
Speaker 1: differently because the charge is different on one side than
Speaker 1: the other. Right, it's overall neutral, but you've separated the
Speaker 1: charges a little bit so that you have a positive
Speaker 1: and negative and so the wave gives the two sides
Speaker 1: a different kick right in different directions, and that spins it.
Speaker 1: But the thing about a wave is that it's a
Speaker 1: wave which means it goes up and then it goes down.
Speaker 1: So now the other part of the wave comes by
Speaker 1: and it spins it the other direction. And so essentially
Speaker 1: what happens when these waves come by a water molecule
Speaker 1: is they spin them back and then forth, and then
Speaker 1: back and then forth, and so they're sort of like
Speaker 1: they're spinning all the little molecules. All the little water
Speaker 1: molecules in your food gets spun back and forth by
Speaker 1: this microwave. So it's not like an internal vibration. It's
Speaker 1: more like a it's but it is sort of a resonance,
Speaker 1: right like in how it spins, like it likes to
Speaker 1: spin at that frequency or special resonance. It's just it's
Speaker 1: the fact that it has this. Anything in your food
Speaker 1: that has an electric dipole will get spun this way.
Speaker 1: It just so happens that water is pretty good at
Speaker 1: getting spun that way because the arrangement of the atoms
Speaker 1: inside the water molecule gives it a larger electric dipole
Speaker 1: than things like plastic, which we're not supposed to eat,
Speaker 1: which you're not supposed to eat. And so what happens
Speaker 1: you heat up all the water molecules and they they
Speaker 1: got a lot of energy now, right, and then they
Speaker 1: spread the energy to the stuff around it. So you're
Speaker 1: cooking a turkey, right, you heat up with the water molecules,
Speaker 1: and then the heat spreads out right from the water
Speaker 1: molecules to the other stuff that didn't get sort of
Speaker 1: mixed up or spun around. I'm sort of thinking about it,
Speaker 1: like to cook something with a microwave. You take like
Speaker 1: a billion tiny little spoons and you stir up each
Speaker 1: of the little water molecules. You're like shaking. You're shaking
Speaker 1: each molecule. Yeah, exactly, you're shaking their booties and they're dancing,
Speaker 1: and they spread their energy out to other stuff. And
Speaker 1: so that's how the non the stuff that in your
Speaker 1: food that doesn't have an electric dipole also gets heated up.
Speaker 1: So it is sort of there is something about water,
Speaker 1: but it's not doesn't have to do with this sort
Speaker 1: of internal resonance. It's just really just it's just it
Speaker 1: just has this kind of a magnet like structure. Yeah, exactly,
Speaker 1: it's the electric dipole structure. And the fascinating thing is
Speaker 1: that for this to work, the water molecules have to
Speaker 1: be able to wiggle right, the keys, you're like turning
Speaker 1: it and turning it back and turning and turning it back.
Speaker 1: So this is something I didn't understand very well, but
Speaker 1: that frozen water is harder to heat up in the
Speaker 1: microwave the liquid water because the molecules can't wiggle as
Speaker 1: much because they're trapped in this ice crystal. It's frozen too, right,
Speaker 1: So it's just naturally harder to heat up because it's
Speaker 1: a pretty cold. That's true. It takes longer to heat
Speaker 1: up to a certain temperature. But it absorbs microwaves less
Speaker 1: efficiently when it's frozen than when it's liquid. So it's
Speaker 1: like it takes in the energy, but because they can't move,
Speaker 1: that energy doesn't get absorb Yeah, exactly. They you know,
Speaker 1: the wave comes by and it tries to wiggle that
Speaker 1: little water molecule because it has that electric dipole, but
Speaker 1: it just doesn't get wiggled as much, and so it
Speaker 1: doesn't absorb as much energy. And then you know, later
Speaker 1: when it's freer because it's you melted it a little bit,
Speaker 1: then you can get mixed up even better. Wow. Imagine
Speaker 1: you know, imagine trying to take a frozen block of
Speaker 1: water and mixing it up until it melts, right, that's
Speaker 1: not going to be very efficient. But you could put
Speaker 1: a spoon into a bowl of water and mix it
Speaker 1: around until it got really hot. That's more efficient. And
Speaker 1: I guess it's convenient because most of the things we
Speaker 1: eat have water in it, right, that's right, And that's
Speaker 1: a convenient overlap between our diet and the physics. Another
Speaker 1: misconception that people have is I think that people think
Speaker 1: that microwaves cook their food from the inside out, or
Speaker 1: that it cooks it totally evenly, right, that it doesn't
Speaker 1: really matter where it is because it's this mysterios quantum
Speaker 1: mechanical thing that's happening. So you're saying it doesn't heat
Speaker 1: up from the inside. No, it doesn't, actually, because these
Speaker 1: microwaves penetrate the food, but they only penetrate a few centimeters.
Speaker 1: They can't get all the way in. Their energy gets
Speaker 1: absorbed before they get really deep into the food, and
Speaker 1: so the stuff that's cooking the inside of your turkey
Speaker 1: in a microwave is still the outside of the turkey. Right.
Speaker 1: All you can do is heat the outside and then
Speaker 1: the inside gets heated by the next layer. And a
Speaker 1: lot of people have microwaves with like a defrost setting
Speaker 1: on it. You know, you press the button. It doesn't automatically.
Speaker 1: What it actually does often is that it runs for
Speaker 1: a little while and then it just turns off. It
Speaker 1: looks like it's doing something, but it turns off the
Speaker 1: microwaves and it just sort of lets the heat flow
Speaker 1: around for a little bit. Oh, I see, So it
Speaker 1: doesn't cook. The outside doesn't cook, it's just you know,
Speaker 1: heats it up in berths. Yeah, exactly. And different parts
Speaker 1: of your food will get hot differently, and and the
Speaker 1: reason is, of course, you know, different parts of different
Speaker 1: amounts of water. But also it's really difficult to get
Speaker 1: an even um dose of radiation, right. It's generating this
Speaker 1: this radiation using a little cavity called a magnetron, and
Speaker 1: and it's really hard to get like an exactly even
Speaker 1: density of microwave radiation inside your microwave. And so you
Speaker 1: have hot spots and cold spots. Yeah. Well I always
Speaker 1: thought that the reason that the inside get hotter than
Speaker 1: the outsides was because you know, I imagine my food
Speaker 1: is getting bombarded by microwaves from all directions, and it's
Speaker 1: the center of my food that's getting hit by all
Speaker 1: directions more than any other part, you know what I mean,
Speaker 1: Like it's surrounded, so all the all the microwaves sort
Speaker 1: of concentrate in the middle. Isn't that the reason why
Speaker 1: maybe the center would heat up more? Well, that would
Speaker 1: be true if the microwaves are sort of aimed at
Speaker 1: the center from some source on the outside. But that's
Speaker 1: that's not how they're generated. This one source, this magnetron um,
Speaker 1: which is a pretty cool name. It generates all the
Speaker 1: radiation and this little wave god that just sort of
Speaker 1: dumps it out into your microwave. And more expensive fancier
Speaker 1: ones have more complicated or double magnetrons to try to
Speaker 1: make it even. But the best thing you can do
Speaker 1: to get even cooking of your food is to put
Speaker 1: it to make it spin, so it sort of rotates
Speaker 1: your food through the hot spots and the cold spots.
Speaker 1: But you shouldn't just put it in the center. R
Speaker 1: If you just put it right in the center of
Speaker 1: your turntable, then all your food is doing is spinning around.
Speaker 1: It's not actually moving through the hot in the cold spots.
Speaker 1: All right, let's get into how microwaves actually make the microwaves.
Speaker 1: But first let's take a quick break, all right. And
Speaker 1: also let's get into how a microwave makes microwaves. And
Speaker 1: you're saying that it uses a couple of transformers toys.
Speaker 1: This alien came to Earth and transformed from a killer
Speaker 1: robot into a kitchen appliance, and its name was magnetron.
Speaker 1: His name was magnetron. Uh no. And this is why
Speaker 1: microwaves were discovered by physicists. There's a guy, Percy Spencer,
Speaker 1: and he was playing with magnetrons because he was interested
Speaker 1: in using microwaves for like navigation and for radar. I
Speaker 1: think it was probably funded by like the U. S.
Speaker 1: Navy or the Air Force or something for like communications,
Speaker 1: like to transmit stuff. Yeah, to either transmit stuff or
Speaker 1: just detect, like you know, where are the rocks and
Speaker 1: where's the coastline and this kind of stuff, you know,
Speaker 1: useful radar stuff where are the enemy ships and all
Speaker 1: that stuff. And he had built this magnetron, and a
Speaker 1: magnetron is just something that generates microwave radiation. How does
Speaker 1: a magnetron make microwaves? How do you make microwaves in general? Well,
Speaker 1: the way to make radiation is, you know, you find
Speaker 1: something in nature which normally produces that radiation, you know,
Speaker 1: because it has a residant frequency, it likes to wiggle
Speaker 1: in exactly the right way to make that radiation. You
Speaker 1: can do that, or you can build a cavity that
Speaker 1: makes it so that electrons have exactly that resonant frequency,
Speaker 1: like you build a little metal box and so that
Speaker 1: when electrons go in there, they like to shake around
Speaker 1: add exactly the frequency you want to generate. And that's
Speaker 1: essentially what a magnetron is, yeah, exactly. It's a lot
Speaker 1: like a musical instrument, you know, and a musical instrument,
Speaker 1: the shape and the size of the cavity determines exactly
Speaker 1: the acoustic waves that you can generate from it. Right,
Speaker 1: you can shorten the cavity or lengthen the cavity by
Speaker 1: putting your fingers on the keys exactly. So a magnetron
Speaker 1: is just a cavity where you shoot electrons. You have
Speaker 1: magnetic and you have magnetic fields in there in order
Speaker 1: to generate exactly the right kind of frequency. And you
Speaker 1: can generate different frequencies by having a different sized cavity.
Speaker 1: So you shoot the electrons in and they all sort
Speaker 1: of sync up and then outcomes this kind of synchronized
Speaker 1: right of light, right, yeah, of of radiation. And for
Speaker 1: those of you know any quantum mechanics, you know that
Speaker 1: when you create a confined space like an infinite well,
Speaker 1: for those of you have taken physics, that's when you
Speaker 1: get quantum mechanical effects that you get special residue frequencies
Speaker 1: energy levels for example. So the same way you have
Speaker 1: energy levels around an atom, you can have energy levels
Speaker 1: inside a cavity. And so you get electrons in there
Speaker 1: and they like to wiggle at this energy level and
Speaker 1: then they jump down an energy level and give off
Speaker 1: that radiation, which is then at the frequency that you want.
Speaker 1: So the microwave in my kitchen has one of these
Speaker 1: magnetrons like a little too. Yeah, exactly, everybody who has
Speaker 1: a microwave has a little radiation creating device in their microwave.
Speaker 1: And um, but don't worry, right, that sounds crazy like
Speaker 1: what I'm exposing myself to radiation? You know, you're exposing
Speaker 1: your coffee to radiation. But also the microwave has metal
Speaker 1: box around it. And the cool thing about electromagnetic radiation
Speaker 1: is that it's basically blocked by almost any conductor. So
Speaker 1: you have a wall of metal, or even just like
Speaker 1: a grate of metal something we call a Faraday cage.
Speaker 1: It will and all out almost any radiation. So the
Speaker 1: microwave radiation inside your microwave is basically trapped there by
Speaker 1: the metal that goes all the way around the box.
Speaker 1: Because because I think I always assumed that my microwave
Speaker 1: has like several microwave guns amy at the middle. But
Speaker 1: you're saying there's only one tube here, like genera spewing out.
Speaker 1: He's a light waves man. You made a funny mental
Speaker 1: image there with microwave gun imagining shooting these things at
Speaker 1: each other. Not a good idea. Most of them have
Speaker 1: a single one. Yes, some of them have double ones,
Speaker 1: or you know, more expensive elaborate ones might have multiple magnetrons,
Speaker 1: but you only really need one and it then you
Speaker 1: just need to guide the radiation using you know, any
Speaker 1: sort of metal tube. Radiation will propagate down that tube
Speaker 1: and into your cooking area. That's pretty cool. So then
Speaker 1: how did they how did he discover the microwave? He
Speaker 1: built this magnetron to try to generate microwaves, you know,
Speaker 1: for these other physics studies, and I guess he was hungry.
Speaker 1: He was a guy could like the snack and need
Speaker 1: a chocolate bar in his pocket, and he noticed that
Speaker 1: he turn the thing on, literally, the chocolate bar would
Speaker 1: melt and like like a couple of centimeters from his
Speaker 1: private parts, exactly exactly. I'm thinking, Okay, you're cooking the
Speaker 1: chocolate bar. You're also cooking the physicist, you know, chocolate
Speaker 1: covered physicist. Here is what we're preparing. Um. But yeah,
Speaker 1: that's what he noticed it, and he reported to his employer.
Speaker 1: He's like, hey, look turns out, you know, my whole
Speaker 1: radar project didn't work, but I invented a new kind
Speaker 1: of oven for you. Um, we can't spin in the Russians,
Speaker 1: but hey, we can all have warmer meals. I always
Speaker 1: wonder how executives feel that way. You know, they give
Speaker 1: you money because they're looking for a certain contract, and
Speaker 1: you come back with like teflon or microwaves, right, all
Speaker 1: these things you're discovered by accident um in research environments. Yeah,
Speaker 1: the pivot, And I wonder what what like amazing inventions
Speaker 1: were thrown away by small minded executives are like, that's
Speaker 1: not what we asked you to develop. Put it on
Speaker 1: the shelf and go back and work on that. Ray gun.
Speaker 1: Make the ray gun work. And for those of you
Speaker 1: who are scared of radiation whatever, don't worry. These things
Speaker 1: are really safe. They surround your microwave with plenty of metals.
Speaker 1: There really is no leakage um, and it's really it's
Speaker 1: even pretty safe to like put your face up against
Speaker 1: the microwave. They used to test microwaves really carefully to
Speaker 1: make sure that none of this radiation leaked out to like,
Speaker 1: you know, cook your brain. But for so many years
Speaker 1: they were so safe they couldn't measure anything that these
Speaker 1: days they don't even bother anymore. And it's really you're
Speaker 1: just hitting it with the light, you know. It's not
Speaker 1: like you're hitting it with particles that then make the
Speaker 1: food radioactive. Right, that's not what's happening. Oh no, no, no,
Speaker 1: It certainly does not make your coffee radioactive, Although that
Speaker 1: does sound like an awesome superhero creation story. Microwave man
Speaker 1: he drank radioactive coffee and gained that coffee's proportional strength.
Speaker 1: Just heats up the food, right, It doesn't make it um,
Speaker 1: It doesn't give it the ability to admit radiation. No,
Speaker 1: just heats of the food. But you know, if you
Speaker 1: were inside a microwave, it would heat up you also, right,
Speaker 1: you would literally get cooked. So there are dangerous but
Speaker 1: only inside the microwave. Outside is not dangerous at all. Cool.
Speaker 1: So that's that's how microwaves work. I feel like like, um,
Speaker 1: I've been irradiated with knowledge today. That's right. A small
Speaker 1: amount of knowledge leads to a lot of inside. So
Speaker 1: the next time you're turning on your microwave, remember you're
Speaker 1: blasting it with radiation. That's basically just taking a little
Speaker 1: spoon into all the molecules in there that have a
Speaker 1: little dielectric field and spinning them around to heat up
Speaker 1: everything else. So there is physics that's making your food taste.
Speaker 1: And as a public service, just remember contents might be
Speaker 1: hotter than expected. That's right. And you know, some people
Speaker 1: like microwaves. Some people don't like microwaves. You know. One
Speaker 1: of the limitations is that you know, did get that
Speaker 1: crispy browniness, But you can just you know, put it
Speaker 1: in your toaster of it afterwards if you really want
Speaker 1: that crunchiness. Yeah, that's that. That's my strategy. Heat up
Speaker 1: the insides and then you toast the outside. On our
Speaker 1: next podcast, how do toasters work? How to eat dinner
Speaker 1: at RG Sounds, how to fix Daniel's microwave of it? Yeah, please,
Speaker 1: I'd love to hear that podcast for less than ten dollars. Alright, everyone,
Speaker 1: we hope you enjoyed that. See you next time. If
Speaker 1: you still have a question after listening to all these explanations,
Speaker 1: please drop us a line. We'd love to hear from you.
Speaker 1: You can find us at Facebook, Twitter, and Instagram at
Speaker 1: Daniel and Jorge That's one word, or email us at
Speaker 1: Feedback at Daniel and Jorge dot com. Thanks for listening,
Speaker 1: and remember that Daniel and Jorge Explain the Universe is
Speaker 1: a production of I Heart Radio. For more podcast from
Speaker 1: my Heart Radio, visit the i heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.