How do microwaves work?

Find out how microwaves work with Daniel and Jorge

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Episode Transcript

Speaker 1 (00:09):
Or Hey, I know you like to joke that any
physics question I ask you could be answered with the
Big Bang. I think it's a pretty solid answer for
any science question, you know, like why does why does
this happen? And it's all because of the Big Bang? Man,
you are like a deep philosopher of science. Sometimes I
think I just just heard you say the Big Bang
too many times. Well, I don't mean to burst your bubble,

(00:30):
but I think I finally found a question where the
Big Bang is not the valid answer. What could not
be due to the Big Bang? Keep listening. Hi, am

(00:55):
orhammy cartoonists and the creator of PhD comics. Hi. I'm
Daniel Whitson. I'm a particle physicist, and I owe my
existence to the Big Bang, as do we all, as
does this podcast. That's right, even this podcast so Welcome
to Daniel and Jorge Explain the Universe, a production of
My Heart Radio. Welcome to our podcast, in which we
explore things big and small, things out there, big and small,

(01:18):
out there in the universe, and even right here in
our homes, in our everyday lives. Something that we use
almost too much. I think perhaps that's right. One of
the joys of being a physicist is looking around you
all the time and wondering how does that thing work?
And that extends to the cosmos and the stars and
the big question to the universe, but it also applies

(01:38):
to just stuff happening around you. You know, why does
that leaf dance that way? Why does the ball bounce
this way? How do I make this thing happen? Or
how does this thing in my kitchen do it's thing?
How does this magic happen? There's crazy physics all around us, right,
and potentially dangerous sources of radiation in our own homes.
That's right. Basically the whole universe is crazy physics. I mean,

(02:00):
that's a good way to summarize the whole thing, right.
That's a that's an alternate answer to the Big Bang?
Why why does why does this particle do that? It's
just crazy physics. It's better than the answer being crazy physicists. Right,
physicists crazy because of crazy physics. I'm not sure about
the cause and effect there, Yeah, um, it might be
the becoming a physicist makes you a little bit crazy

(02:22):
because you see the world through different eyes. Right, everything
you look at you try to understand in terms of
an equation or model, or try to dig down and
understand how this emergent phenomenon can be explained by tiny
little particles bumping up against each other. Yeah. So on
this podcast we usually tackle very big topics like the
size of the universe or where did the Big band
come from? But sometimes we like to tackle smaller topics

(02:46):
or topics that are in everyone's everyday life. Yeah, So
to be on the podcast, we'll be tackling something that
everyone has in their kitchens. So today on the program,
we'll be asking the question how does a microwave work?
Where I guess more specifically, how does a microwave oven work?

(03:06):
You know what a microwave is. You put the stuff
in there, you press the button, It spins, it beeps,
it turns around, and it comes out hot. Right, But
how does that actually happen? What's the physics that's going
on there? Yeah? How do microwaves work? I mean, we've
had them around for a long time. It seems right
to heat up our foods are in our snacks, in

(03:27):
our hot pockets. They first appeared in kitchens in the
late fifties, I think, so it's been decades. Hatties around
for a while, Yeah, And like many useful inventions, they
were discovered by accident. They were discovered by a physicist
poking around trying to do one thing, discovered something else useful,
another way to save time. Right, for a lot of people,

(03:48):
it's sort of it's sort of a convenience appliance. Like
if you were to heat things up in the regular oven,
it would just it would take much longer, but in
a microwave, things seem to get hot really fast. Yeah,
and you know, I don't want to take any of
this the em out of this this podcast episode, but
I'll admit that the microwave in our kitchen at home
has been broken for about five years. And yeah, it's

(04:10):
built into the double oven thing we have, so to
get repaired, we have to replace the whole thing. So
we just sort of put it off forever. And the
truth is we haven't really missed it or never really noticed.
You've lived without a microwave for five years. It is possible, people,
you can live with that a microwave. Yes, it turns
out you can make popcorn on the stove. So what
do you use it for? It is like a storage

(04:31):
You store some pots and dance in it or did
you clean Did you clean it before you abandoned it?
I wonder if you open this now, it's never been cleaned. No,
you know our pet rats like to hang out in there. Um, okay,
we don't use it for anything. It just uses up
space in the kitchen. Wow, So you don't use a
marc So if you have to heat up a quick thing,
you just what do you do? You eat it cold? No,

(04:53):
we got a toaster oven, We got an electric water kettle,
We got a stove top that serves for mostly everything. Yeah,
it turns out life is possible without a microwave. But
it's a fascinating object in so many people's kitchen, and
lots of people swear by it, so I thought it'd
be interesting to dig into the physics of it. It
turns out that very few people know how microwave works,

(05:13):
and the people who think they know how microwave works
probably have it wrong. Yeah. I was reading through these
notes and I realized I have no idea how a
microwave oven works. Or I thought I did, but it
turns out that I that I don't, And so that
sort of brings up an interesting question, like there's so
many people out there who use a microwave. Almost nobody
knows how it works. How come nobody seems to have

(05:34):
spent any time thinking about it or wondering about it.
Is it just physicists who want to understand, like how
this stuff around us worked, and everybody else is sort
of happy to just press a button and get their popcorn.
I wonder if it's a generational thing. You know, at
this point, most people grew up with the microwave. You know,
it's sort of like, um, it's just there. It's like
nobody sits around wondering how a refrigerator works or how

(05:55):
a pencil works. You know. I think my kids ask
me how refrigerators work. I want to know how things
work that existed in the universe before I came to be.
I'm not like big Bank. That's old news. I'm only
interested in the news stuff. It's not trending, the big Bang,
it's not trending. I don't care. So it's something that
everyone is probably familiar with, and maybe most people own.

(06:17):
But we were wondering how many people out there and
know how a microwave actually works. That's right. So I
walked around the streets of Aspen, Colorado, a place where
people come from all over the world, with all sorts
of different backgrounds. And I asked folks if they knew
how a microwave work. The most people in Aspen, Colorado
own multiple microwaves. They probably own multiple microwave companies, That's

(06:39):
what I mean. And they say, I don't care as
long as the share price keeps going up. Yeah, So
I think about it for a second. If you were
skiing out there and askm in Colorado and then a
scruffy physicist asked you, hey, how does the microwave work?
What do you think you would answer? Here's what people
had to say, best guess microwaves electricity fastened through food. No,

(07:00):
electricity turned into something genetically modifies your food? Yeah, has
right onto, right on too? And how does that eat
up your food? The moistation of food is what calls
the uh yes electricity, the Mormon quality. Can you find

(07:23):
that jet English? Something around electricity coming down in waves?
You say, start and then what happens microwaves? No, I
do not know. Do you know how a microwave works?
I do, Oh, how it works? Maybe not? We pressed

(07:45):
plus through a second bottom then start, all right. It
seems that those microwaves company owners in Asthment don't really
have much of an idea of how they work. Well,
I was amazed at the huge variety of answers. I mean,
we got radiation, we got genetic modification to the foods um.

(08:06):
There's that one guy who seemed to understand how microwave worked,
but he could only explain it in Japanese to his wife. Well,
that's the same with me. I I know how it works,
but I only know how it works in Japan. I
like the guy who said, how does the microwave work?
You just press the start button. That's how it works, right,
I know. Like I was asking for tips, like help,

(08:27):
I need to use the microwave and I don't know
how it works. Please give me tell me my food
is cold, Like I'm out here on the street with
my recorder looking for tech support from my microwave. Well
he would have been helpful. Yeah, yeah, and uh, and
you know, and you heard a couple of people say

(08:48):
what I think is a common trope, which is that
the microwave heats up the water, right, which I think
is a common misunderstanding. We'll get into it later, but
that's not how a microwave works, right, Yeah, that's what
I thought too. And also some people said it has
with electricity, like somehow it uses electricity to zap your food. Yeah,

(09:10):
and you know it does use electricity. It's not like
it's a coal powered microwave or something steampunk steampunk microwave,
like you have all the steam, but you converted to microwaves. Yeah,
somebody out there probably has done that, you know. On
a recent episode about gravitons, I wondered out loud what

(09:30):
a gravitron was, and that moment in our podcast I
think might have generated the most listener response because I
got dozens of emails from people who had written in
their childhood a gravitron an amusement park ride. So that
generated the most the most emails of anything we've ever
done so far. Actually know that, because that was on
the latest season of Stranger Things. Yes, you're right, there

(09:52):
was a scene in the gravitron Um. So if anybody
out there knows of a coal powered microwave, please right
in and say, d as a picture. I'd love to
see it. Well, so, um, not a people. A lot
of people know how a microwave works, and I didn't
know apparently how a microwave works, so let's get into it.
But maybe first what you talked about how normal ovens work,

(10:12):
like the ones with gas or the ones that are electric,
not the microwave kind. So a normal oven basically works
by heating the air inside the oven, and then the
air heats your food, right, And that's you'll notice this
because if you open a normal oven, you get like
a rush of hot air that comes out and burns
your face, right, Whereas if you open a microwave, you
don't notice that. In a regular oven, you you rely

(10:35):
you like, you put the energy into the air, and
then you rely on the air to give the energy
to your food. That's right. And remember, on a microscopic level,
what's happening is that the air is heating up, and
that means that the air molecules are getting faster. Right.
We talked about temperature in another episode. Sort of crazy concept,
but the simplest idea is that you're just speeding up

(10:55):
the air molecules, so they're zooming around faster and faster
inside the oven, and sometimes they bounce into your food
and they deposit some energy, so they heat up the
molecules in your food. Right, maybe your oven is gas
and his little flames or it has heating element if
it's an electric oven, and that heats up the air, right,
which speeds up those molecules, and they bounce into the

(11:16):
molecules of your food and heat them up. Yeah, when
you put it like that, it seems really inefficient to
think about ovens like that. The air and then the
air you have to wait for the air to bump
into your food, and then it only bumts into the surface, right,
the outer skin of your food. So that's why it
takes a while to heat up in a regular oven,

(11:37):
that's right. And they're super inefficient in my house because
every time I'm baking something, somebody will walk by the
oven every five minutes and open it up. What's in there,
and then all the hot air rushes out and you've
got to heat up the whole oven again. I'm surprised
you're a regular oven works, Daniel. I'm gonna put a
lock on it or something. But yeah, that's over camp
fire every night. That things exactly why. Um, that's exactly

(12:01):
why the food in your oven heats from the outside
in because the outside is the only part exposed to
the air. Right, So the outside of your food, the
outside layer gets heated by the air, and the inside
gets heated by the outside. Like you're cooking the turkey,
the skin gets hot first, and then the heat of
the skin cooks the next layer, and that layer cooks
the next layer, and that layer cooks the next layer.

(12:23):
So it's sort of like heat propagating through the turkey,
but has to start from the outside. That's the hottest part, right,
And that's kind of then that's kind of good sometimes
because that's where you get you know, crunchy crusts. Yeah, exactly,
you get this browning effect from the hot air, and
that's because the air can get to a sort of
a high enough temperature to be like caramelization, and that
gives you the good browning stuff. And you know, sometimes

(12:45):
you want that. You want the outside to be crunchier
and hotter than the inside. Like for a turkey, you
don't want the breast meat to get up to a
certain temperature because then it gets dry, but you do
want the outside of a higher temperature. So for things
where you want the outside hotter and the inside a
little bit cooler, a convection of it is perfect, Okay,
So it doesn't sound super efficient, but it's an old,
old timey trusted technology we've been doing. We've been using

(13:08):
ovens for thousands and thousands of years. It doesn't break down,
that's right. I mean in the old days, before we
had gas ovens and electric ovens, an oven it was
just like an enclosed space with a bunch of burning
wood in it. Right, And people still do that, like
a pizza oven. Right, you can get up to eight
hundred degrees or nine degrees, and you see these things,

(13:28):
they're just like they got wood burning in the back.
And it's just an enclosed space to trap the heat.
Because if you have a fire without walls around it,
then the heat just rises and you can cook over it,
but it's much less efficient. So you just enclose it
to sort of capture the heat um where you are.
And that's that's an oven. That's all an oven is
is a heat source and something to capture it to
the air stays hot. All right, that's how normal ovens work.

(13:51):
So let's get into microwaves. But first let's take a
quick break. All right, we're talking about microwave ovens and
how they work. So Daniel break it down for us

(14:12):
how does a microwave oven work? Well, maybe we first
we should figure out we should talk about what a
microwave is, right, Like, what is this thing? We tackled
the word oven, now we're tackling the word microve waves. Right,
but first let's break it that into micro m wave.
What is the letter N really means? What is letter I?

(14:33):
Three hours later we'll get to the answer. It's pretty simple. Actually,
a microwave is just a kind of light. Right. Remember
that all these things gamma rays, X rays, UV light,
visible light, um, radio waves, these are all just parts
of the electro magnetic spectrum. It's not like a special
kind of ray or a special kind of particle, or

(14:56):
you know, laser is just plan o light. It's just
plain old electromagnetic radiation, right, And a microwave just refers
to the wavelength of that radiation. So remember, the thing
that differentiates a gam array from ultraviolet light, from visible light,
from X rays or radio waves is just the frequency

(15:17):
of the wiggling. Right. All these things are electromagnetic fields
oscillating up and down and left and right, and the
speed at which they oscillate, how many times they oscillate
per second, right, or equivalently, the wavelength of their oscillation, right,
how long that wave is UM determines which one it is.
And so radio waves are the ones with a really
long wavelengths, Like there are radio waves that have lengths like,

(15:40):
you know, dozens and dozens of meters. Microwaves. It's sort
of a confusing name because microwaves are radio waves with
shorter wavelengths, so down about twelve centimeter. But it's only
shorter compared to radio waves, which have like dozens of
meters of wavelength. They're not short comparable light visible, they're
not like nanometers, they're not microscopic, that's right, They're only

(16:04):
micro compared to really big radio waves. Oh scale thing. Huh.
But so they're microwaves are actually like megawaves compared to
like the visible light that we all see every day, yeah,
which is wavelengths of like hundreds of nanometers, which is tiny, right,
These things have wavelengths that are in the twelve centimeters.
That's you know, the size of your hand or something

(16:26):
like that. So these things have real physical wavelength Wait
are you telling me that physicists names something in a
confusing way? What are you telling me that you're surprised
that physics name would be confusing. Touche touche. Anything named
in the pre Jorge epoch is defined to be confusing
because you were not involved. Yeah, yeah, the PJ. We

(16:50):
don't like to talk about it. You know, it's a
dark period in the history of physics, but it does exist. Okay,
so they're they're microwaves, but they're not really micro they're
actually like, you know, twelve centimeters. It's sort of like
the length of your hand. Yeah, yeah, exactly, And so
that's what a microwave is. And then you might wonder, like,
all right, but you know, how does that heat my food?

(17:12):
If I shine my flashlight at a turkey, it doesn't
cook it, right, not, Well, it depends on your flashlight,
doesn't it. If your flashlight is the large Hadron collider,
then yeah, maybe, yeah, that's what I mean. It's it's
it's it's not that the regular light doesn't cook, it's
just that it doesn't cook as well. Yeah, that's true.

(17:34):
It does deposits of energy, it just doesn't have that
much energy on it. But it's essentially the way a
microwave oven works is that it blasts your food with
marcro wave radiation, right, which, again, radiation, It sounds scary,
but it's really just light. Yeah, light is an example
of radiation. So this is just another kind of electromagnetic radiation.
And and you might be wondering like, well, okay, why

(17:56):
does this specific frequency of radiation tend to heat at
your food? Why is that do that? Right? Well, one
thing you'll notice is that when you open up a
microwave oven after you've cooked your food, right, that the
air inside the microwave oven is not hot. So a
lot of people think that the way a microwave works
is that the microwave radiation heats up just the water

(18:16):
inside the food. Yeah, I've heard, I've heard of that. Yeah,
Like somehow there's something like it only heats up the
water molecules, or preferentially the water molecules in your food.
That's kind of why. I like, if you stick a
plastic plate, it's not going to heat up as much
as if you put you know, a hot dog, mhmm.
And there is some truth to that, right, A microwave

(18:37):
will heat up some kinds of food more than other
kinds of food. But the reason that some people give
is that they think that microwave has like a resonant
frequency with the water. Remember, microscopically, water is made out
of molecules, and those molecules can do things like spin
and vibrate, and like all atomic stuff, it's quantum mechanical,
which means it can only accept um radiation. It's certain frequencies.

(19:01):
Like we talked about how atoms can absorb wavelength certain
wavelengths of light and not other wavelengths of light. So
some people, I think, imagine that this is what's happening
instaide your microwave. That water can absorb frequency at this
wavelength um and the air and the other stuff can't. Right,
So that's the common misconcept. And when you say resonant
frequency mean like kind of like a water the idea

(19:22):
that water has kind of an internal bouncing nous to it, right,
like an internal m M like frequency. It likes to
bounce around like a guitar string. Yes, exactly, And it's
true of every atom, right, they do have special frequencies
at which they like to vibrate. And it depends on
the atom and how it's built and how the electrons
are organized and all that stuff, and so they do

(19:42):
have special resident frequencies that they do like to absorb radiation.
But that's not what's happening here. That's not the way
that the microwave work. It's not it's not definitely not No,
it's a totally different but really fascinating mechanism. You just
nuke my brain here, I just reard my start my
illusion of understanding here. Okay, so it's not making a

(20:04):
residence with the water, So how is it? But it is?
It is sort of related to water, right, Like, there's
something about water molecules that microwaves are kind of specially
tuned to a heat up. Yeah, and it's a different process.
It's called dielectric heating. Essentially. It's because water molecules they
have the same number of positive and negative charges, but

(20:25):
they're not exactly balanced in the same place, right, which
means that one part of the water molecule is a
little more positive and another part is a little more negative.
So overall there's a little bit of a separation of
the charges. So what happens when electroc one side of
water is more optimistic dealing, what's more pessimistic. That's right,
You got the upside and the downside. Um somewhat some

(20:48):
water molecules are like the glasses have full of us.
They have just like this glasses have empty of us.
It's a big But what happens when electromagnetic waves by,
Remember electromagnetic waves interact with things that have charge, right,
negative and positive charge, and so what they do is
that one part of the molecule gets pushed one way

(21:09):
and the other part that has the other charge gets
pushed the other way. You're saying, like a water molecule
is kind of like a little magnet where one end
is sort of negative and the other side is positive.
So it's not like perfectly even, yeah, it's not. It's
kind of like a magnet in that there are north
and south, right, But in this case we're talking about
electric charges and they're positive and negative, and the waves

(21:31):
come by and they tweak it, and they tweak it
differently because the charge is different on one side than
the other. Right, it's overall neutral, but you've separated the
charges a little bit so that you have a positive
and negative and so the wave gives the two sides
a different kick right in different directions, and that spins it.
But the thing about a wave is that it's a
wave which means it goes up and then it goes down.

(21:52):
So now the other part of the wave comes by
and it spins it the other direction. And so essentially
what happens when these waves come by a water molecule
is they spin them back and then forth, and then
back and then forth, and so they're sort of like
they're spinning all the little molecules. All the little water
molecules in your food gets spun back and forth by
this microwave. So it's not like an internal vibration. It's

(22:13):
more like a it's but it is sort of a resonance,
right like in how it spins, like it likes to
spin at that frequency or special resonance. It's just it's
the fact that it has this. Anything in your food
that has an electric dipole will get spun this way.
It just so happens that water is pretty good at
getting spun that way because the arrangement of the atoms

(22:34):
inside the water molecule gives it a larger electric dipole
than things like plastic, which we're not supposed to eat,
which you're not supposed to eat. And so what happens
you heat up all the water molecules and they they
got a lot of energy now, right, and then they
spread the energy to the stuff around it. So you're
cooking a turkey, right, you heat up with the water molecules,
and then the heat spreads out right from the water

(22:55):
molecules to the other stuff that didn't get sort of
mixed up or spun around. I'm sort of thinking about it,
like to cook something with a microwave. You take like
a billion tiny little spoons and you stir up each
of the little water molecules. You're like shaking. You're shaking
each molecule. Yeah, exactly, you're shaking their booties and they're dancing,
and they spread their energy out to other stuff. And

(23:16):
so that's how the non the stuff that in your
food that doesn't have an electric dipole also gets heated up.
So it is sort of there is something about water,
but it's not doesn't have to do with this sort
of internal resonance. It's just really just it's just it
just has this kind of a magnet like structure. Yeah, exactly,
it's the electric dipole structure. And the fascinating thing is
that for this to work, the water molecules have to

(23:39):
be able to wiggle right, the keys, you're like turning
it and turning it back and turning and turning it back.
So this is something I didn't understand very well, but
that frozen water is harder to heat up in the
microwave the liquid water because the molecules can't wiggle as
much because they're trapped in this ice crystal. It's frozen too, right,
So it's just naturally harder to heat up because it's

(24:00):
a pretty cold. That's true. It takes longer to heat
up to a certain temperature. But it absorbs microwaves less
efficiently when it's frozen than when it's liquid. So it's
like it takes in the energy, but because they can't move,
that energy doesn't get absorb Yeah, exactly. They you know,
the wave comes by and it tries to wiggle that
little water molecule because it has that electric dipole, but

(24:23):
it just doesn't get wiggled as much, and so it
doesn't absorb as much energy. And then you know, later
when it's freer because it's you melted it a little bit,
then you can get mixed up even better. Wow. Imagine
you know, imagine trying to take a frozen block of
water and mixing it up until it melts, right, that's
not going to be very efficient. But you could put
a spoon into a bowl of water and mix it

(24:46):
around until it got really hot. That's more efficient. And
I guess it's convenient because most of the things we
eat have water in it, right, that's right, And that's
a convenient overlap between our diet and the physics. Another
misconception that people have is I think that people think
that microwaves cook their food from the inside out, or
that it cooks it totally evenly, right, that it doesn't

(25:06):
really matter where it is because it's this mysterios quantum
mechanical thing that's happening. So you're saying it doesn't heat
up from the inside. No, it doesn't, actually, because these
microwaves penetrate the food, but they only penetrate a few centimeters.
They can't get all the way in. Their energy gets
absorbed before they get really deep into the food, and
so the stuff that's cooking the inside of your turkey

(25:26):
in a microwave is still the outside of the turkey. Right.
All you can do is heat the outside and then
the inside gets heated by the next layer. And a
lot of people have microwaves with like a defrost setting
on it. You know, you press the button. It doesn't automatically.
What it actually does often is that it runs for
a little while and then it just turns off. It
looks like it's doing something, but it turns off the

(25:47):
microwaves and it just sort of lets the heat flow
around for a little bit. Oh, I see, So it
doesn't cook. The outside doesn't cook, it's just you know,
heats it up in berths. Yeah, exactly. And different parts
of your food will get hot differently, and and the
reason is, of course, you know, different parts of different
amounts of water. But also it's really difficult to get

(26:08):
an even um dose of radiation, right. It's generating this
this radiation using a little cavity called a magnetron, and
and it's really hard to get like an exactly even
density of microwave radiation inside your microwave. And so you
have hot spots and cold spots. Yeah. Well I always
thought that the reason that the inside get hotter than

(26:30):
the outsides was because you know, I imagine my food
is getting bombarded by microwaves from all directions, and it's
the center of my food that's getting hit by all
directions more than any other part, you know what I mean,
Like it's surrounded, so all the all the microwaves sort
of concentrate in the middle. Isn't that the reason why
maybe the center would heat up more? Well, that would

(26:52):
be true if the microwaves are sort of aimed at
the center from some source on the outside. But that's
that's not how they're generated. This one source, this magnetron um,
which is a pretty cool name. It generates all the
radiation and this little wave god that just sort of
dumps it out into your microwave. And more expensive fancier
ones have more complicated or double magnetrons to try to

(27:14):
make it even. But the best thing you can do
to get even cooking of your food is to put
it to make it spin, so it sort of rotates
your food through the hot spots and the cold spots.
But you shouldn't just put it in the center. R
If you just put it right in the center of
your turntable, then all your food is doing is spinning around.
It's not actually moving through the hot in the cold spots.
All right, let's get into how microwaves actually make the microwaves.

(27:37):
But first let's take a quick break, all right. And
also let's get into how a microwave makes microwaves. And
you're saying that it uses a couple of transformers toys.

(28:00):
This alien came to Earth and transformed from a killer
robot into a kitchen appliance, and its name was magnetron.
His name was magnetron. Uh no. And this is why
microwaves were discovered by physicists. There's a guy, Percy Spencer,
and he was playing with magnetrons because he was interested
in using microwaves for like navigation and for radar. I

(28:21):
think it was probably funded by like the U. S.
Navy or the Air Force or something for like communications,
like to transmit stuff. Yeah, to either transmit stuff or
just detect, like you know, where are the rocks and
where's the coastline and this kind of stuff, you know,
useful radar stuff where are the enemy ships and all
that stuff. And he had built this magnetron, and a
magnetron is just something that generates microwave radiation. How does

(28:45):
a magnetron make microwaves? How do you make microwaves in general? Well,
the way to make radiation is, you know, you find
something in nature which normally produces that radiation, you know,
because it has a residant frequency, it likes to wiggle
in exactly the right way to make that radiation. You
can do that, or you can build a cavity that
makes it so that electrons have exactly that resonant frequency,

(29:08):
like you build a little metal box and so that
when electrons go in there, they like to shake around
add exactly the frequency you want to generate. And that's
essentially what a magnetron is, yeah, exactly. It's a lot
like a musical instrument, you know, and a musical instrument,
the shape and the size of the cavity determines exactly
the acoustic waves that you can generate from it. Right,

(29:31):
you can shorten the cavity or lengthen the cavity by
putting your fingers on the keys exactly. So a magnetron
is just a cavity where you shoot electrons. You have
magnetic and you have magnetic fields in there in order
to generate exactly the right kind of frequency. And you
can generate different frequencies by having a different sized cavity.
So you shoot the electrons in and they all sort
of sync up and then outcomes this kind of synchronized

(29:55):
right of light, right, yeah, of of radiation. And for
those of you know any quantum mechanics, you know that
when you create a confined space like an infinite well,
for those of you have taken physics, that's when you
get quantum mechanical effects that you get special residue frequencies
energy levels for example. So the same way you have
energy levels around an atom, you can have energy levels

(30:17):
inside a cavity. And so you get electrons in there
and they like to wiggle at this energy level and
then they jump down an energy level and give off
that radiation, which is then at the frequency that you want.
So the microwave in my kitchen has one of these
magnetrons like a little too. Yeah, exactly, everybody who has
a microwave has a little radiation creating device in their microwave.

(30:38):
And um, but don't worry, right, that sounds crazy like
what I'm exposing myself to radiation? You know, you're exposing
your coffee to radiation. But also the microwave has metal
box around it. And the cool thing about electromagnetic radiation
is that it's basically blocked by almost any conductor. So
you have a wall of metal, or even just like
a grate of metal something we call a Faraday cage.

(30:59):
It will and all out almost any radiation. So the
microwave radiation inside your microwave is basically trapped there by
the metal that goes all the way around the box.
Because because I think I always assumed that my microwave
has like several microwave guns amy at the middle. But
you're saying there's only one tube here, like genera spewing out.
He's a light waves man. You made a funny mental

(31:21):
image there with microwave gun imagining shooting these things at
each other. Not a good idea. Most of them have
a single one. Yes, some of them have double ones,
or you know, more expensive elaborate ones might have multiple magnetrons,
but you only really need one and it then you
just need to guide the radiation using you know, any
sort of metal tube. Radiation will propagate down that tube

(31:44):
and into your cooking area. That's pretty cool. So then
how did they how did he discover the microwave? He
built this magnetron to try to generate microwaves, you know,
for these other physics studies, and I guess he was hungry.
He was a guy could like the snack and need
a chocolate bar in his pocket, and he noticed that
he turn the thing on, literally, the chocolate bar would
melt and like like a couple of centimeters from his

(32:07):
private parts, exactly exactly. I'm thinking, Okay, you're cooking the
chocolate bar. You're also cooking the physicist, you know, chocolate
covered physicist. Here is what we're preparing. Um. But yeah,
that's what he noticed it, and he reported to his employer.
He's like, hey, look turns out, you know, my whole
radar project didn't work, but I invented a new kind
of oven for you. Um, we can't spin in the Russians,

(32:31):
but hey, we can all have warmer meals. I always
wonder how executives feel that way. You know, they give
you money because they're looking for a certain contract, and
you come back with like teflon or microwaves, right, all
these things you're discovered by accident um in research environments. Yeah,
the pivot, And I wonder what what like amazing inventions

(32:51):
were thrown away by small minded executives are like, that's
not what we asked you to develop. Put it on
the shelf and go back and work on that. Ray gun.
Make the ray gun work. And for those of you
who are scared of radiation whatever, don't worry. These things
are really safe. They surround your microwave with plenty of metals.
There really is no leakage um, and it's really it's
even pretty safe to like put your face up against

(33:11):
the microwave. They used to test microwaves really carefully to
make sure that none of this radiation leaked out to like,
you know, cook your brain. But for so many years
they were so safe they couldn't measure anything that these
days they don't even bother anymore. And it's really you're
just hitting it with the light, you know. It's not
like you're hitting it with particles that then make the
food radioactive. Right, that's not what's happening. Oh no, no, no,

(33:33):
It certainly does not make your coffee radioactive, Although that
does sound like an awesome superhero creation story. Microwave man
he drank radioactive coffee and gained that coffee's proportional strength.
Just heats up the food, right, It doesn't make it um,
It doesn't give it the ability to admit radiation. No,

(33:53):
just heats of the food. But you know, if you
were inside a microwave, it would heat up you also, right,
you would literally get cooked. So there are dangerous but
only inside the microwave. Outside is not dangerous at all. Cool.
So that's that's how microwaves work. I feel like like, um,
I've been irradiated with knowledge today. That's right. A small
amount of knowledge leads to a lot of inside. So

(34:16):
the next time you're turning on your microwave, remember you're
blasting it with radiation. That's basically just taking a little
spoon into all the molecules in there that have a
little dielectric field and spinning them around to heat up
everything else. So there is physics that's making your food taste.
And as a public service, just remember contents might be
hotter than expected. That's right. And you know, some people

(34:39):
like microwaves. Some people don't like microwaves. You know. One
of the limitations is that you know, did get that
crispy browniness, But you can just you know, put it
in your toaster of it afterwards if you really want
that crunchiness. Yeah, that's that. That's my strategy. Heat up
the insides and then you toast the outside. On our
next podcast, how do toasters work? How to eat dinner
at RG Sounds, how to fix Daniel's microwave of it? Yeah, please,

(35:00):
I'd love to hear that podcast for less than ten dollars. Alright, everyone,
we hope you enjoyed that. See you next time. If
you still have a question after listening to all these explanations,
please drop us a line. We'd love to hear from you.

(35:21):
You can find us at Facebook, Twitter, and Instagram at
Daniel and Jorge That's one word, or email us at
Feedback at Daniel and Jorge dot com. Thanks for listening,
and remember that Daniel and Jorge Explain the Universe is
a production of I Heart Radio. For more podcast from
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(35:42):
or wherever you listen to your favorite shows.